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Airline Pilot Technical Theory Adam Howey Airline Pilot Technical Theory Adam Howey

TCAS

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What Is TCAS

Sam. Adam. TCAS. Yeah, traffic collision. No. Traffic alerting. Traffic alert and collision avoidance system. Yeah, that's it. Which is a type of ACAS, Airborne collision avoidance system. That's the only one really until maybe some time in the future, which we might talk about. How recently have you had a TCAS RA?

00:29

Resolution Advisory I have had one or two. Where was it? Obviously flying into Amsterdam. And it was a surprise, you not really, because we could almost see the traffic coming and it look very close to us and it wasn't actually An aggressive RA.

00:47

It was actually what was the command the command was monitor, vertical speed. So basically just to fly level, right? Destruction was to carry on flying level, where we were Yeah, so it was pretty young eventful, but we obviously went through the whole process of save the day, did it?

01:01

Yeah, this guy went underneath this about 400 feet. Wow. I could say I'm all the way it was a king. Was like a king air. Okay, but, yeah, just going down the beach. We were on approaching to AMS Amsterdam. What did the Dutch have to say about that? They weren’t very interested really.

01:15

I told him that we had a TCAS RA. Told him that it was because he could hear the guy on frequency. Let's say just like yeah, we'll put in a report , rewind then TCA. Yeah, what is it? Traffic. No. But what is it? Oh, what is that? Sorry. So well, what's it done for you?

01:35

So it's It's an avoidance system built into the aircrafts transponder. Of all aircraft with mode. Charlie, with altitude information can have TCAS, and TCAS to talk to each other. So, That they can issue instructions between aircraft. They can interrogate each other and talk to each other and provide avoiding action.

02:00

To prevent to prevent a midair collision basically? Yeah, it's a tool for preventing mid-air. Mid air collision . So like, mid air collision loss of separation. One of the biggest. Categories of aircraft accidents. Yep. I think TCAS has done a good job of Definitely keep an accident rates in that category way down. Yeah.

02:23

So I think TCAS was made mandatory in about 2000s. I think in European airspace and apart from the one accident which we're going to talk about, what could that be? So, that would be the mid air collision over the German Swiss border Uberlingen, okay? Part from that one. I can't really think of any other.

02:45

Mid-air collisions. Between between aircraft that have been equipped with TCAS. Yeah. Okay. So surprises me that it was only mandated after the 2000s. Yeah, I think it was 2000. It was mandated. Yeah, pretty successful system. You like it? Yeah, yeah, I do. Yeah, I love it. It's pretty simple.

03:07

Yeah, and it's only there as a backup. If a mistake by pilot or air traffic control, Yeah it's labelled as a safety net. So yeah GPWS Ground Proximately warning system being another one TCAS. A safety, net being almost as if all other Possibilities to catch that accident have failed.

03:27

And this is the last thing that's going to Save you apart from the pilot being the The inbuilt traffic collision avoidance system if you like. We can always prevent an accident but TCAS is a safety net. There, You've told me it's to stop as hitting another aircraft from what airborne?

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03:42

What does TCAS do

Yeah. So practically What does it look like to you when you had your TCAS? So it built up our situational awareness as well, even without issuing warnings or advisories because it displays other aircraft on our navigation display. In form of a little diamond. So you can look at your map.

04:00

See other aircraft that are that are equipped with TCAS. And you can see where they are in relationship to you and what altitude above or below. So, what use is that and Well, it's good for your own awareness. Particularly in like a busy TMA around an airfield, you can Building up your situation awareness as to where you might be in the sequence for approach, where are the traffic is?

04:25

If you're maybe requesting further climber a traffic aren't giving it to you, you can maybe see the reason why because there's traffic above you, that's about to cross. So front of you, So actively we're actually using it most of the time. Yeah. For not what it was designed for.

04:40

Yeah. Exactly. I mean it is designed to raise your SA but you're looking okay. The person in fronts two and a half miles in front of me on the approach. If you get any closer that's going to be a go around close, you're saying I want to climb out this table in this but I can't because somebody's I can see somebody 2000 feet above me.

04:56

That's going to cross in front of us in the next two or three minutes. So it's like on our ND moving map kind of crudely. We almost have like the air traffic control is radar. Yeah exactly. Yeah. Except that it's not as cluttered because it only gives us certain aircraft depending on how we've got it set and Yeah.

05:16

What we thinks relevant to us. Okay, so what when we get more involved in it, what happens next? Then I suppose so it goes from a hollow sort of white diamond. The next sort of phase if you like if you're getting quite close to another potential conflict or potentially intruder, The the diamond gets coloured in.

05:35

So it's now like a solid white. That diamond and that is It's essentially potentially intruder. This that see that yeah, coming quite close to us in terms of literally, or vertically or their rate, whatever rate their climbing or descending out, or your climate, go to sending out is a potential.

05:54

Conflicts make quite proximate traffic. That's right. Yeah. So that would, that definitely draws your attention to the navigation display. I find if you see one, you see, one go coloured in. What would you do then? Okay, you can see proximate traffic. Yes. So again great tool for situational awareness.

06:13

That makes you think, right? That somebody close to us approximate traffic. So I might adjust my rate of climb my rate of descent. If it's particularly excessive, I might look at the window. To see if I can see them. So again, yeah, probably share your mental model with your.

06:29

Yeah, exactly. Say, have you seen that? I've seen that look. We've got traffic there. Even ATC, sometimes might point out that there's traffic. And your traffic in your one o'clock while thousand feet above. So it's raising or you giving your opportunity to raise your SA. Maybe think ahead about what might be next.

06:49

Possibly silently review the TCAS manoeuvre. Should it happen, Okay, so what what would happen next? So the next level would be a traffic advisory at TA and in this case, the little white diamond would turn to a orange diamond and then the system the TCAS system would then call out to you.

07:10

That i'm not going to do the impression. You have to “traffic traffic”. That's really good. Thank you, sort of an American accent. Traffic traffic, that definitely gets you attention. Yeah. So that would if not already that would draw both pilots, every airline will have different operating procedures but There will be possibly, some sort of call then between the pilots as to Who is at least in control of the aircraft or Some sort of separate procedure to almost get them ready for what may come next.

07:40

Should you manoeuvre? Now based on that? No, Well, I mean every airline might be different but I think Some airlines you might be told to maybe adjust your rates, but Other airlines will say no just Really don't don't interfere. Basically, just leave or preparing and just prepare for what may or may not.

08:01

Come next, Somebody looking for the traffic. Yeah, so one generally, one pilot will start looking out for the traffic whilst the other. There is looking in on the navigation displaying and getting ready for the manoeuvre. You know, what's next? So then the final level, which if it gets to that it is resolutionary advisory.

08:19

So, resolution advisory RA. So That's when I think the diamond goes to a square. I think you're right. Red square. Right. This all being an airbus, this is all air bus. Yeah. Obviously. And then you'll get some instruction basically from TCAS and the TCAS will actually tell you What to do and as a could be a simple as Climb.

08:40

Climb this and descends. Monitor vertical speed adjust vertical speed. Increased climb. Decrease climb. Few others as well probably. But the systems are we talking to each other? So the other aircraft may or may not get an instruction Sometimes. One, aircraft can get an RA, was the other record of trying to gets a TA.

08:58

All right, all right. So, Just stop us. Hitting another aircraft? Yep. It's a safety. Net should be the last thing. Really that saves us. That's what it looks like to a pilot. I'd say it's pretty simple works really well. It's very simple system and it does work very well and we practice it a lot in the simulator Probably over practiced it really for the actual amount that we not over practice it but we do it a lot considering.

09:22

Well, yeah, how you've had one in one and 13 years. Yeah, for two maybe things might have been tea, definitely had one into pafos. Because, airspace basis. Don't talk to each other there and people are trying to use high rates of climb to reach there. Cruise level. So, If we have an RA in the Airbus and it's pretty similar and all fleet, it's just like a really simple memory item for us to do.

09:46

Yeah, remember . What the memory item is the actions. So the actions would be to disconnect the autopilot. I'm turning off the flight directors. I'm so two reasons for that on the Airbus. Of obviously because you don't you not going to be following the flight direct just anymore. You can be following the TCAS instruction but also it reverts the thrust mode to speed mode on.

10:07

Yeah, on an airbus. So autopilot off flight, directly soft. And then following the TCAS into the green band, which is The TCAS kind of takes over your VSI, your vertical speed indicator. I know have big chunk of red and a little chunk of green. And it wants you to basically aim for the green.

10:24

So whether that's climb descent or maintain, and you should manoeuvre the aircraft into the green band. Of the way I train it is. And smoothly. But promptly so it's not it's not like a It's not yanking her But how simple is that? So green. Good, red bad. Yeah, exactly.

10:44

Definitely all pilot. Yeah, should be pretty simple for a pilot degree. Keep the authorised in. Yeah, and just just do it and just following, it didn't worry about anything else. Yeah, exactly. So it's Really simple in a really good way, really effective system. Yeah, I'm really happy with it as a system.

11:04

It's not even something that I'm sort of scared of. I don't like a GPWS but TCAS any day. Yeah, definitely that makes sense. And I think Taken into another level talking about, you know, passages on board in the commercial environment. I imagine if you had a TCSRA It's not that violence and manoeuvre.

11:24

I don't think mostly Some people have mentioned seatbelt. So it's not part of manoeuvre and I don't think they really need to know. So, is there any horizontal? Thing you need to do. In terms of well, the whole system is vertically based, which is genius. Yeah, it doesn't require you to turn left or right.

11:43

And if you're in a turn in the question is, what do you do? It? Don't matter. Yeah, he's just got a resolve, it vertically This genius and smoothly and promptly just inside the green band. If you even at high altitudes especially on a fly by wire aircraft. If you kind of Blip the side stick, you're going to end up in that green band quite quickly and smoothly, really Know.

12:04

is genius and am I right in thinking, you have four seconds to react. It might be, I think it's four seconds to react to an initial RA. Yeah, which is quite a long time, really. And if We'll talk about this maybe in a minute, a reversion. You have two seconds to react.

12:22

Yeah. Yeah. That's right. So I supposed to talk about now. So, reversion would be If either one aircraft, maybe wasn't. Following the TCAS or possibly you are Your climb climb, takes you into the path. Another aircraft. The different aircraft going above. You might get a reversion which then says, descend descend.

12:42

So you might actually swap completely what you're doing. And the green band has gone from right at the top of the VSI, your climbing to write the bottom. He has to be a bit quicker on reacting to a reversion because things are I forget the, the makes us sound pretty cool.

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12:57

Why TCAS, History

If anybody got four seconds to react but, you know, being possible not to do it really. It. So, As air traffic increased, call it in the 50s. But it was very famous mid-air collision over the Grand Canyon Which is when the FAA decided that they needed something to prevent mid-air collisions, okay?

13:16

But obviously, if you were going to increase air traffic volume significantly and mid-air collisions of factor, it has to be reduced to like near zero because The physics of the situation mean that any mid-air collision is basically always going to be catastrophic. Though, you know, in America they have a lot of mixing of like general and airliner aircraft as well into all sorts of airfields, which is like less.

13:40

I'm always surprised when I go to America, you know. Yeah. But although in Amsterdam You get our light aircraft. Yeah. Scoot and underneath you. And that's exactly what our situation was. I don't, I forget the exact details but I'm pretty sure the other aircraft and it was only yes that got the got the RA but going back you know they to come up with a system that works this.

14:02

Well was taking a long time but actually they developed it quite early on First they want to like a ground based system. And it was actually called be CAS and was like a beacon based system but I mean doesn't work over the sea Does it? And also there was issues with how busy the beacons would be.

14:19

And that's a big part of this is the the data that has to be transmitted rapidly between the aircraft. And then you imagine some of these systems were designed a long time ago and it has to compute Very quickly if there's going to be an accident but the airspace is so busy.

14:33

I mean, it must be computing all the time. Yeah and initially when TCAS was implemented, there was a lot of nuisance and you could even say spurious. Triggers of the system, which is not good because empires Blend that it was annoying and maybe not to follow us. I mean, people are getting them off boats that have transponders, right?

14:54

And this kind of thing, right? Yeah. But eventually, we’ve up with this like incredibly robust. Airborne collision avoidance system which may be superceded sometime in the future. Now, ADSB is coming out but still going to use basically the same principles that we've been using for. I don't know, like 40 years, the years.

15:14

Well, we know, yes, something like that. And then i think you're a control. Reckon, it's Decrease the chance of airborne collision by like a factor of five. Out Most of saved. A lot of lives, definitely, and I think Pilots now our generation pilots definitely love the system. And it's so good that it's actually the nuances of Of it which of course problems which is because it's such high density traffic.

15:40

Situation that we're flying through. Now, the systems just needs tweak in every so slightly just to stop as it being so annoying. So the fact that it's safe isn't even in question. Yeah. So yeah, I mean, I don't know if you remember the mid-air accolision that sticks in my mind, is the cessna that hit an aircraft in the circuit in the states and then there's a picture of San Diego.

16:02

And it was as a picture of the southwest airliner. I can't remember if it was a DC9 like on inflames going down this booty have visual contact with that right with that session 172. Okay? And they think there's a lot of confirmation like oh yeah he's gone that way or whatever and it's actually underneath them.

16:21

That was like, 144 people. There was another DC9 with, like, 80 people who died in the 80s, but this is when TCAS, basically different been developed, but then it was like accelerated. And then by the end of the 80s, we had we had like the the TCAS system Almost that we know now.

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16:40

Faults

So, It's really simple for us to use works really well. Any idiot could kind of grasp it in a few, a few minutes. However, like most of these systems, if you, it's good, if you know the memory drills, I mean, you have to not good, it's mandatory. But if you just understand slightly deeper, The system that will give you a much safer use of it And I'm only talking just scratch the surface of it.

17:05

So yeah, if you just fly in the green you'll be safe. But a couple of things like the RT and how air traffic controller involved, if you just slightly understand that That's going to prevent. Potential accidents. Which ubiling in was in there was a mix of conflict. Yeah, so my understanding now, is that extra control if someone reports TCAS RA air traffic control will just sit back and not try and issue.

17:28

Yeah my experience is totally the opposite. Really? Honestly it's totally the opposite. I found the controllers really defensive, okay. So they start talking and they start saying, no, no, it's not a problem. The bottom line is once TCSRA. Activates yeah. You ignore ATC even if they're screaming at you, even if they said Ignore TCAS.

17:55

The the law aviator Air Law is that you were follow that TCAS system. So my questions you is uberlingham was 2002. Yeah. Was that in was that made law after uberlingen or was it? It was definitely the law in the procedure joining uberlingen and however, Thing about air law is depends where you are?

18:15

Yeah, well yeah yeah was was depends whether things are standardised. And the Russians had a different idea. So the RT you need to know your RT as part of the memory action, Like to the letter. And you need to be able to What makes like, Always gone about unreliable speed.

18:36

I mean, you always do what air traffic control says but this is the one Chance. You've got a snap out of however many years of listening to our traffic control and go. No. Because in some countries they will ignore you tell you to ignore tcas , something like that.

18:50

The other thing is, That in any other situation. Don't say TCAS. Which is a really bad habit that pilots have gotten here all the time. Yeah. So you said that. When you see proximate traffic, You'll start looking for them. Next minute, air traffic control to be helpful, say others crossing traffic that and they you will always hear people read back.

19:12

Yeah, we've got him on TCAS. Yeah, but the word the phrase TCAS should only be used when you in an RA manoeuvre. Yes, that's right. Yes, yes. It doesn't help. Yeah, because that changed as well. Didn't it? And so, so, yeah. So I have to sort of consciously So say just copied.

19:27

Thank you. Yeah. Yeah you can say we visual or visual or even though when you IMC, I guess because you so anything but TCAS I'm yeah, don't say the word TCAS, I guess everybody. Oh, it doesn't, but it should get everybody's like blood pressure at basically, everyone should get that startle factor.

19:47

So that's our safety. Net air traffic control, have their own safetinets. They have like short-term collision avoidance, which is a bit of a wider. A time that the radar system will predict things like their own TCAS but yeah it's a bit it's two and a half minutes in advance of an ever.

20:06

Collision collision. And now we're moving into aircraft that will fly the tcas manoeuvre for you. Yeah, we already have that. Yeah, I'm so talking as if it's the future but it's on A350 A380. Obviously it'll just fly the manoeuvre. So, We've got high performance aircraft now especially like a hear the seven, three, 737 max is just so powerful, so you've got we've now got really high rates of climb aircraft when sometimes we don't want them, especially an upper air space and in RVSM air space, so TCAS.

20:43

Doesn't know. What we're intending to do even though the FMS does know, we're going to go into an out capture mode. So TCAS, now, often tells us off It when it thinks we're going to have a collision when we know full well, we're going to level off. Yes. And say that's something that probably will be developed into future versions of airborne collision avoidance system.

21:06

Of preventions better than cure, right? So not having high rates of climb. Is the most. Is your biggest defence against having a t-cast most of the time, because I think 80% of TCAS RAs, Are. Preventative RAs. Yes. As that make sense and they're reducing ours, IE, you've got a high rate of climb towards the level off.

21:29

It's just asking you to reduce your rate of climb, reduce your rate of descent, which you said earlier early versions of TCS actually that all warning was reduce climb But people would always go the wrong way because they'd hear the word climb. Yeah. So then they changed it to adjust vertical speed adjust, right?

21:47

Which always meant reduce vertical speed but that was too ambiguous. So now we just have “level off”. Yeah. So it used to say, oh, choose a lower vertical speed, like, you doing 3,000 feet a minute. So just choose 1500, but now they've sacked it all off. And it just tells you to level up leveller because it's Because it's easier pilots understand that.

22:07

Yeah so it stops you climbing order to send him just for a minute and then Say it was a major problem for a while that the most common RA was for you to adjust vertical speed. But a significant proportion of pilots would go the wrong way. Wrong way, not into the green.

22:25

And the other thing is they'd overreact, So it's smoothly and promptly just inside the green band, but they'd go. They'd have the start of factor, I guess. Just they remember uberlingen, and they'd go for it. All stick. And then, as you've already said, then they cause a another RA with another level, because they go too hard.

22:44

Yeah. Yeah. But I thought you manual actually says, just into the green band. Yeah, that's your goal or just out of the redband in my even second. Okay. Yeah, exactly. So TCAS is so good. We're sort of creating a little issues within the system of TCS. So having some sort of understanding a belief, the surface of how it works.

23:05

And how it interacts with ATC, definitely makes it even safer system. But it but it works really well. One. One little thing that I wanted to mention earlier, which I forgot about building up our situational awareness. You know, looking at the navigation display was the accident that happened in Milan Linate.

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23:25

Linate Airport Disaster

I remember oh, like this. Yeah. So His first tragic, really, there was a private jet, which was Somewhere where it didn't think it was. It was like this foggy day. I can't remember how long ago. This was probably 20 years ago. Up by essentially. In the low phase, this private jet thought it was on a taxi labour, It was actually on the active runway.

23:49

A traffic control. Cleared Scandinavian SAS to take off. And unfortunately the SAS hit the private jet. They had a collision on the runway. Big fireball, but because of the low vision of the fog, nobody knew that the crash had happened. Even after control couldn't see from their position that a crash had happened.

24:09

And they actually, then cleared, the next aircraft to take off, which was a left answer. And the left hands refused to accept the takeoff clearance because his SA was so high that he hadn't seen the magenta of the white diamond of the SAS like get airborne. So you know he would have seen it say yeah.

24:30

Plus zero one plus zero two. So yeah. So he refused the takeoff clearance because he said that German situational NS yeah. And i think tcas is used same much like reigning up on anything. Yeah. And especially low visit. It's very useful. For the SA now in the so with ADSB, automatic dependence valence broadcast, aircraft, that can accept that information onto their ND.

24:57

They have like a They have like an enhanced, what you would say, Ticest display tells you Might be wrong about this. I think it tells you to call sign and the type okay and the altitude probably wrong about one of these but really, really enhances your SA that information is coming from the ADSB which is different to TCAS but a future generations of TCAS.

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Future

25:23

I probably going to use. ADSB. So, the problems always been since time began, which is How do you solve the problems of? CNS, communication, navigation and surveillance. So, we've already done a podcast on A communicate, we VHF and some of the limitations of that VHF is on radio. Communication is, is a really old system, but works really well and that's one of the That's one of the main defences against aircraft.

25:51

Collisions is just read backs. You know, it's just it's just talking to air traffic control and coordinating everything. Yeah, navigation. Obviously, we used to use radio beacons and now we're moving towards. And performance base navigation. So Where we are in in space and time the aircraft now, knows better.

26:13

Then the ground knows because of our GPS input. So we can not from the ground but from the aircraft, we can tell other aircraft where Where we are better than we used to be able to. So with ADSB, We can have a like, a more accurate TCAS because a GPS position, basically is so accurate and then surveillance used to be done by.

26:33

This yet primary radar. Which would like, you know, developed in World War, I would would ping back if it be a dot on a screen. Yeah. And then you've got secondary radar, which uses the transponder. So if you interrogate a transponder, it decides, whether to send back information, like, yeah, I'm here and it can have lots of information sent with it, but definitely sends back, it's it's altitude .

26:56

And that's what TCAS uses, which is transponder. But the use of adsb in the future, He's going to just mean it's like broadband for aircraft. Basically, Lots more data travelling between the aircraft other aircraft and the ground. And say all this airborne collision of avoidance systems are going to probably start to use that.

27:16

And then if you think about like drones, like if they had ADSB on, you can have a TCAS against the drone. Yeah. You know whether it was supposed to be there or not whether it's just You know, what is already? A very sort of safe system. It's probably only gonna get even safer and even better.

27:31

They did get to. So TCAS 2 is what we're talking about. TCAS is just TAs and it was some regional aircraft had that but TCAS 3 was supposed to come in at some point and had horizontal resolutions but basically you don't need them because everything can be solved vertically.

27:50

Yeah but with I think it's called ACAS x at the moment is what they're calling it. That's like the next generation of airborne Collision of avoidance system because That's the umbrella term TCAS is almost like the brand name. So, if something else can solve airborne collision avoidance, that will come under the same umbrellas, it'll be some changes in the future, but the point I'm making is ever our sa .

28:11

A situation awareness that's coming from this pretty rudimentary like, pings from transponders. He's going to be enhanced by a ADSB and It's like a, it's so many layers of cheese in front of the, actually, using the TCAS system that keeps us safe. Yeah, other things, air traffic control, you know, like, they don't know, we've got an RA, but now we have the ability maybe to download it to them and it pings the same.

28:35

We've got an RA. Yeah, and so be all sorts of changes to it, but all these things have to be You know, I think they're basically proposing to change nothing as far as the pilot is concerned because the simpler the better. Yeah. You don't mess with it. Yeah. But the algorithms that run in the in the TCAS haven't been changed since the 80s but now the computer power is so much better.

28:57

You can have much more accurate computations about closest point of approach and stuff like that. It's definitely some changes come in. But as far as we're concern hopefully I'll just be flying the green. Yeah, stupid. Simple for us. Yeah, first pilots. So I think what we're going to talk about now Is how it managed to go wrong.

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29:18

Überlingen Mid-Air Collision

Yeah. Even they taste was well in truly involved in the accident. Yeah, the sad sad story of uberlingen is sort of referred to as the uberlingen crash, but yeah, uberlingen was the town on the ground. On the Swiss German border. On Lake Constance, where the debris of the aircraft fell.

29:37

Yeah, you've maybe done a little more research than this on this to me I sort of Feel like I know this story quite well. And this obviously world documented on Natural, geographic air crash investigation. You know, this quite a lot of stuff out there on it but You want to broadly so talk about.

29:55

Yeah happened. It is well documented because it's very dramatic. And like,, there's been plenty of films. Including did you know an Arnold Schwarzenegger film? About this about this. I think I might have known that. Yeah, I didn't know that. So I need to watch it. Now it's loosely based.

30:13

On, on this. It's a 2017, but Yeah. It's no. What's it called? I've written it down. I feel like I might even seen it. Aftermath. And did Arnold Schwarzenegger play the controller think? Maybe. Yeah, I've seen it. I've got feeling I might even seen it. Well, But I need to watch it.

30:33

Yeah. So, It's well known. It's, it's Dramatic in its in that sense, it's addictive. So there's a lot of films and podcasts and That plays and whatever, all written about it. Likes. You see after learning about it again. I think probably last time I learn about it was pretty me being an airline pilot as always becoming an airline pilot.

30:58

It's really given me. It gives me that. And, But i are basically lose. Sleepover it? Yeah. And because Our routine day job, which I'd like to say take incredibly seriously still leaves you a bit disconnected from the reality of what you do in sometimes or what could go wrong.

31:21

Yeah. I don't think it changes anything about your approach to the job. But, Definitely gives it a bit more. Makes it a bit more vivid, so, Like you said, do you like first 2002? Of aircraft taking off from Moscow, to go to barcelona. With 45 children on board as well as other people.

31:43

The school trip. Wasn't I think or yes school trips Barcelona. Yes. The children had like one their place on this trip. And for their achievements. And i also they probably been picked because they had well connected parents and bear that in mind. So, they're going to Barcelona in the evening and Like sliding doors or whatever but they're they'd missed one of their connections or it been late and this was especially charted to get them there without delay.

32:12

So the air line, the Russian airline Bashkirian. Yeah there you go. And they're flying, the Tupolev Tu-154. Which is amazing Russian aircraft that they basically had to build and design in Russia during the cold war and fly around Russia. And it's actually designed to go in like rough strips, can like land on gravel and stuff even though suggest aircraft is like, super high performance, they had like a thousand of them in Russia.

32:39

So I guess the Russians loved it, really? A little try. Try jet. Try engine thing. I don't think I've ever really been in close to it any of these things and well, they were still flying until About 2010 are likely things. So, This airline no small outfit had about 33 aircraft okay, maybe like 13 of these four of them on the flight deck.

33:03

It's a training flight and flight. Yeah. So you captain left-hand seat and the chief pilot in the right hand sea, How many times in these accidents? Is it like some combinations? Like that? Some yeah, they have a flight engineer and for no reason. There's a copilot super numerary so I don't know why he's in the flight deck but There's even some.

33:23

Ambiguity about who the piloting command was. And I You know, i just throw that in there as to whether that is any kind of contribution. So maybe, yeah. As to So they're going towards Barcelona, it has to be a training flight because I say, I guess they think Barcelona is so crazy which it is and they captain has to have two supervised visits for they go.

33:42

So that's why they're chief pilots going. Okay. But there experience flying outside of Russia is like really limited like they've only done a handful of trips each I think they're chief pilots only been outside, Russian territory twice, right? Or something but he's checking out the captain to get Barcelona.

33:59

So even there experience outside , so Russia. Is slightly limited. Meanwhile, DHL 757, we've only two people, two pilots on boards, taking off from Bergamo. And to fly north over the Alps to Brussels, and then imagine that this Russian aircraft is coming, kind of southwest generally towards Barcelona from Russia.

34:20

And it's late in the evening by the time they get towards this piece of airspace, it's about 11 o'clock at night. So, At any about halfway through the Russian sector, maybe about two hours to land in. Not long. After space, the DHL would have grab one the captain of the DHL British.

34:40

Yeah. And a Canadian first officer 757. So at this point in in history, yeah, the DHL have Had. TCAS for a while and they like you said have been training it in the simulator a lot. And so they may or may not have had one in real life, but in every check, they're doing their.

35:01

Yeah. Now If the Russian airlines want to fly outside of Russia, they have to have TCAS because as you said is been mandated, yeah, about the time in the millennium but in Russia you don't have to have TCAS. So, The Russian aircraft has got TCAS. It's been fitted. However The pilots have and the Navigator, the sorry, the flight engineer have done the I want to say CBT (computer based training).

35:27

They've done the That they've ticked a box somewhere that says, they've done the learning. They've done the learning , They've never done one in the simulator because guess what? The simulator doesn't have TCAS fitted to it. And there it's their exposure to TCAS is like incredibly limited like, The amount of sectors, whether even done a flight with TCAS on board is like a hand like, very, very few.

35:51

So, That's his aircraft approach. This piece of airspace, Simsuric controllers. Below. And well, there's one actually bases. One, this is another factors that it's always, massive is always the holes of the Swiss cheese and they left the Swiss cheese. Well, so this this unit used to always have three controllers on And it became, Common.

36:19

That the controllers would take it upon themselves to for one of the three to just sleep for the entire shift. Because then as they alternate day after day, one of them's, getting a free, a free night sleep, and then on these deep night shifts, Then due to personnel limitations, there was only two in the control room, shift?

36:40

Yeah. And for, however, long that had been going on, but still, the controllers had decided that they one of them would still sleep for the entire shift. There's only one On duty. The same time maintenance returned up, they're like “yeah, we need to do some maintenance on the, on the old radar there”.

36:58

Yep. To the radar goes into this thing called backup made, I think or degraded mode. Another hole in the Swiss cheese. Okay? An integrated mode. The radar can only do seven miles of separation, rather than five and unbeknown to the controller. The STCA short-term collision avoidance visual warning, which goes off at two and a half minutes prior to collision.

37:26

Doesn't work, doesn't work. But all one that goes off 30 seconds prior to collision does work. Now, there's a little airport down there, which I've flown into called Friedrichshafen on Lake Constance, Add This controller also has to do the area control for that. So guide the aircraft in onto the ILS, basically.

37:47

Um, but no problem because it's 11 o'clock at night and Friedrichshafen doesn't have any inbound traffic. It's part from some little airbus shows up and says I’m late and needs like vectors towards Friedrichshafen. He does that. He's working two radar screens. I think it looks like two stations.

38:03

Yeah. And So, A DHL request climb 360 and the Russian aircraft is at 360. Yeah. So, The controller is trying to co-ordinate the fact that two aircraft are going to be at 360 because he delays one of them That the climb for a minute and he's trying to get into touch with Friedrichshafen tower.

38:27

To hand over this airbus. He's coming into land. But every time he tries to use the phone, it's not working. And I don't know if that's due to this maintenance or not, or the Friedrichshafen just aren't picking up, okay? So, he keeps getting distracted. And then, just at the wrong moment.

38:44

He gets quite heads down in that problem of trying to contact Friedrichshafen Yeah. And he misses the first part of this of this TCAS. Yeah. So the two aircraft to fly in towards each other and simultaneously. They. Both. Get TCAS RAs. Yeah. And the DHL. Calls “TCAS RA” and their controller.

39:09

Doesn't hear that because he's busy with the Friedrichshafen situation. Yeah. Next minute, he notices of his own accord that these two aircraft are going to collide or. Yeah. At least they're heading towards each other. So he instructs The Russian aircraft, to descend. And to fly level, three, five zero, due crossing traffic and expedite.

39:32

He doesn't say emergency or avoiding action or anything like that. Up to the Russian stars to descend. And, This is now whilst the DHL is starting their. Manoeuvre to descend send. So just to clarify that say the Russian aircraft, They were instructed to climb on TCAS. Was that right?

39:57

And they were contradicting that by following the air traffic controllers, instruction to descend it all happen at the same time and while. Basically control is distracted. These two aircraft. Get a TCAS RA. Yeah. And the DHL aircraft is told to descend. Yeah. And the Russian aircraft is told to climb.

40:16

By the TCAS system, yeah. The. Air traffic controller wheels. This chair over sees that something's going on, has missed the fact that DHLs called over the radio TCASRA And to resolve the situation. He decides to tell the Russian to descend, fly level three five zero. I mean it's 50 50, isn't it?

40:34

I think so complete 50/50. So the Russian decide even a 25/75. Because if you'd have contacted DHL, yeah, with a conflicting instruction they might have ignored him. So DHL down game involved, because They can hear the air traffic controller, trying to deconflict is what we think happened. Initially. This.

40:57

What? I'm just describing now and folds over seconds. Yeah yeah. And now, An aural alert goes off for the controlling now which he never heard, which is totally useless anyway, because it's too too late for him to really do the for the controller to provide any Useful instructions that would result in a thousand feet of separation So it's going to be a loss of separation.

41:18

Say both aircraft to descend in. And the TCAS can see that they're still on a collision course. And so it tells the DHL. To increase the rate of descent. Hm, which they do down to 2600 feet per minute. And it now tells the Russians. To increase their climb. Even they they're not climbing, they're descending.

41:43

Now, the Russians. And CVR shows that they're a little bit confused about what to do. Yeah. Yeah. There was Can I say that there is a conversation about? It is a concept imagine you've got conflict of like you got a captain Chief pilot who's the training, captain examining, kind of examining this guy Two other pilots, well, Pilot and fly engineer all in flight deck.

42:09

This is happening pretty quickly. Interestingly the co pilot this 757 was PF. He went to the toilet . And literally, as he sat back down, And the RA was beginning, right? Now. What's amazing is these aircraft are not just at the same level. Then now descending. Yeah. But, They could be descendent at any rate.

42:34

I find it. Unbelievable. They managed to collide, like, I mean, So, I could DHL chimes in and says, Something about TCAS RA, I think they say unable to guess already. But then, in the next few seconds, the controlling gives visual. Information. To the Russians. Hmm. And says that. The DHL aircraft?

43:01

Is i think one o'clock or two o'clock? On their right side, and it's wrong. Yeah, they're on the other side, decide. Yeah. But the Russians actually spotted in the end. And that's when they start to start a climb. But it's too late, basically. So the entire vertical, stabiliser of the 757, Basically goes right through the middle.

43:25

Yeah, of this Russian aircraft, with these children on board in the middle of the night. So, the Russian aircraft is sliced into like four bits, And the 757 has no fin goes on a little bit. And just getting into a spin, just goes nose. First into the ground, 70 degrees nose down.

43:49

So, Before I talk about the aftermath, you know what, what could we unpack about that? And I mean, for me, it's I like to talk about the Swiss cheese, but there is so many little things in that, they're just remove one of them. And it probably doesn't happen. Remove that airbus going into Friedrichshafen and remove the maintenance guys in the air traffic control centre.

44:11

Removed. The The guy who's sleeping the night, he sleeping removed, the Russians, sort of following ATC rather than TCAS. I just anything. Just one little thing would probably so the Russia. So it's easy to blame the Russians, right? Yeah, I don't think you can really, I mean, but the stay had they didn't really know and they weren't required by law.

44:32

Really what? What TCAS is about Now, there manuals had about three conflicting statements in them. One that said, Be ATC is basically the final say, but another, that kind of said, you would always follow TCAS. But then another that said, you should look and try and see an avoid aircraft rather than that's your last line of defence.

44:55

So it was not objective and a must that you absolutely follow TCAS, which I think answers when you questions from earlier. So, In terms of air law, you just got a total. Fuck up there. Where The Russians are. Allowed to do whatever they want in their own airspace and then they're obviously transit in other airspace And it's not been mandated or, it's not absolutely clear what the procedure has to be.

45:21

Yeah. Another nuance now in TCAS 7.1, they changed the reversal logic. And or they updated the reversal logic so you can get reversal in TCAS but it used to be that if you if you got too close, the TCAS thought that the it's too late to command a reversal but now it will up to a later.

45:42

Point realise. Oh if one's not following out, I'll switch it around. Um because the DHL could have gone into anything of climb. Yeah, it's just bizarre that, you know, you can understand slightly two aircraft hidden each other both flying level. Because with the aeroplane flights. So accurately, but the fact that they were both in a descent, I mean, I I can't even compare, I it must it would be like two goalkeepers at different end of a football pitch, both kicking the ball, and it'd be like the balls hitting each other.

46:11

You know, be the amount of air and space up there is just so vast. Yeah. I mean, chance of two aircraft in each other. In, whilst in a manoeuvre, is some art doubtitude. It's just It's just incredibly bad. Look really. Yeah, it's horrifying. What will come on to? Another usually sleep over.

46:31

I also find A harrowing about it is that there are other aircraft that were flying around. Is a clear night that say they saw oh yeah saw the flame. You know saw the explosion basically. Yeah I mean that would just it's in July oh just stay with you forever.

46:47

Like seeing that you know it's like flying on a clear night excee hundreds of miles To see that. And and oh, yeah, horrible horrible. It just impossible to engineer this situation. Going back to the history of TCAS and mid air collisions and so on, it's it is amazing that they happen at all because I've said before, we're so used to live in on a 2D in a 2D world.

47:12

It's kind of hard to imagine how much volume there is up there. Yeah. So there is a lot of space, but Aircraft tend to congregate together, you know, in the same circuit pattern in the same, airfield the same time. Up and they're kind of attracted to each other. Yeah, you know, these, these all these layers that prevent aircraft here in each other.

47:33

And have to be there because otherwise we would all be at the same place at the same time and and that that piece of airspace there, you believe in it is a very busy bit of airspace. And although it was 11 o'clock at night in July For the to be one controller on.

47:49

I don't know too much about air traffic control but That that does strike me as as As not, right? I'm always going over that bit of airspace high altitude. Yeah. So there has to be all these things, you know, just the semicircular rule about what altitude you fly. Yeah.

48:08

And you read backs. Your the radar. Then you've got your STCA short-term collision, avoid the system, you TCAS, and so many layers that in there. That should prevent this from happening. And then, just the fact that they happen to Be so close to each other. I mean the tail of their 757.

48:28

I mean you talking like Couple of meters and it would have been a near miss or something. So, That kind of tragedy. I think difficult for humans to kind of understand. You know, in terms of our aircraft safety. Accident reports of what we go on to decide. Like, you know what what's happening.

48:50

So the next thing report didn't come out until 2004 and that's where we start to draw conclusions from and In the beginning, the air traffic control. Company responsible for air traffic, control that did. Basically blame the Russians which didn't help. What happens next? As there. Final extra reports coming out is kind of unbelievable.

49:12

But without getting too graphic, let me just Tell you what happened in the days, following the accident. Imagine you've sent your children off on an aircraft. He told that there's been no survivors and you know, quite common. I think a lot of these parents didn't believe it. The Russians flew them out there like the next day or something.

49:31

And they get to the site and this beautiful countryside. And of the site of this, this crash. If you split a spread over quite a wide distance, the the tupolev aircraft And the Russian is just join in like the the search effort. One gentleman. Vitaly. Kelly of. Goes to find his wife, his daughter, and his son.

49:58

And straight away, just Thus starts looking for for them. And he finds his daughter. In the woods. Wearingthe little necklace that she wears is young tiny little daughter and later on Basically finds his wife and his son as well. So, For a human being to be able to comprehend.

50:18

Really, what has unfolded to fly to this? This piece of countryside, like far away and, and your families lying there. You know, in the, in the days after it's just, it's incomprehensible, yeah. So the edge trafficking controller is obviously Most weird. He needs mentor treatment basically for being The edge of controller, he was responsible, at that time, the one on duty.

50:47

And, The parents had turning up to the side of the crash. And, You know, totally destroyer and there's probably a lot of anger. And the father of, if those of that family vitali Kelly of wants to me with the air traffic controller and obviously that that doesn't happen and and refuses.

51:10

And then over the next few years, you know, bits of the Accident report, start to unfold and so on. Just a few months before the final extra report. Years later. Vitali of decided to return. To that same place. And hires a private detective. To find the air traffic controller.

51:32

And decides to go and confront him. Turns up to his house. Where he himself has got three children. I think the air traffic, controller. Neilson is his surname. Confronts him in his back garden. And stabs him to death in front of his own family, then he dies within minutes. In Front of his children.

51:54

Say I said, like really terrible. turn of events, it's not really related to the aviation necessarily. But then the story gets even crazier. Because, He's arrested and he goes to prison. But he only he does like a couple of years. Putin lobbies to get him out. Yeah. And he's Has this sentence reduced for diminished responsibility.

52:21

And then he gets lobbyed gets out, then he goes back to Russia. And becomes like quite a high ranking politician. Yeah, there is area and then gets like a national award like one of the highest awards for his region for his services in politics. And, This is all sort of explains why you can see him be an interviewed on multiple locations in high definition.

52:46

Talking with complete victory, all about that controller like talking. And with no regret, remorse whatsoever about the murder that he committed. Which is something I don't think I've ever seen in my life but before which is like, he's not locked away where you can't hit. He's shouting from the rooftops about how proudy as of what he did and seemingly as the support of the people who are You know in his country here appointing him on TV and so on and say the Russian is like have quite a different response, Nationally to the accident and and his involvement in it.

53:24

I don't really know what to say, like it's crazy, it's a crazy story and I think. Good that, you know, let's say this last bit is not really related to TCAS but Is such a dramatic story. I think admit actually being Possibly the most dramatical. Yeah, exactly. Aircraft accident.

53:44

I don't know. Most harrowing , aircraft accident. It then invokes like so much emotion. Yeah, in the people who Survive effectively. But they didn't know how to respond. Either nationally, or on an individual level because there is no explanation, your average aircraft accident, like to me, like a road traffic accident, you know what I'm like about speeding.

54:08

A road traffic accident, you know, with with fatalities. It's just so meaningless. It's like it's not cancer, it's not, it didn't have to happen. Yeah. An air traffic. Accidents are always the same. They're just I think if you lost somebody in one, you would never really understand why on a human level like why is that happened?

54:30

But this one, with all the, the my new Things that came together to allow it to happen. Is even more unexplainable. Does that make sense? Definitely. And so more. Upset in shocking. Yeah, shocking. Yeah. It's a shocking story. So for me, all it does. Really maybe as I've got older is In.

54:56

You know, sad. Sadly, it posts like the human element back into the job. But then, It also shows you that How amazing? We can do. Some some geeks who've probably never flown a plane in their life, like, came up with the algorithm, like in the 60s to detect aircraft, collisions and fit omni directional, aerials to top and bottom of aircraft then And then some genius, you know who knew about the semantics of aircraft displays was like kept flying to the green.

55:29

Yeah. How many lives have been saved like that? Despite that tragic story, TCAS has been a brilliant edition to The aircraft and saved many, many lives and accidents. So long may continue. Yeah absolutely and it's moving promptly just inside the green. Yeah and keep it really simple for those pilots for risk, guys For me.

55:50

Yeah. That's it? Really? That's TCAS. All right. Yes.

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Altimetry

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Transcript Start

00:03

Sam, Adam, Altimetry. What do you know? Well, I feel like I know a lot. Why? Because it's in our everyday life, okay, but then I also feel like I don't know as much as I should. And when it gets very technical, I don't really, you know, this just things that are more clear to understand it.

00:22

Yeah. Maybe. But obviously, then this is not so much about the technical side of it that we're gonna talk about. Do you think the scope of this is big or? Yeah? I think so. I think you could go on a lot of tangents with our altimetry and altimetres, okay?

00:36

It kind of touches on instrumentation and pressure. Where should we stop? I thought maybe the different types of altimeter. Okay. I thought of three that we use commercially three different types. Can you think of any more? I'd say if I can think of three, but I was thinking the barometric altimeter, obviously, the GPS altimeter, which we don't really use, but is there and then the radio altimeter, yeah, as well.

01:04

And maybe just explaining the differences and how we would use them differently and what they used for. Should we talk about? Pressure altimetry barometric? Yeah, sounds good. It might be the main source of altimetry. Yeah that's generally what we use primarily? Listen to. But what is your altitude?

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Altitude

01:24

Yeah. What does that mean? Well, it is obviously your height above sea level based on standard atmospheric pressure. I feel like if mixed of a few things that yes probably I'm sure when I was doing my research I read some Latin like definition of oh yeah I'll team metre or I'll really yeah but I'm interested.

01:51

I can't remember. Yeah. Sorry, well I mean I think you can distil this to the basics which is do we ever really know what our altitude is? Well, yes, sort of. Okay, this is, yeah, with the radio altimeter. Okay, good point, but not so much with the barometric. I agree.

02:15

What do we want to know our altitude with reference to? Yeah, and the core of it being what is an instrument in the cockpit. What is it? Really telling you? Yeah. Okay. And after staring at it for 30 years or 50 years or how long you career might be, what does your brain think?

02:39

It's telling you do we need to always be aware of the limitations of everything that instrumentation the aircraft, especially these things that were staring at. Yeah, all day, every day. Yeah, because I feel like after thinking long and hard about altimeters I've realised. It's more of a concept than like a.

03:02

Yeah yeah and an absolute thing. Yeah, I agree. So you like to tell everybody, were at 3,000 feet feel so secure. It's like I got three zero zero. Yeah. But where am I? Really? How? How high yeah. What exactly is my height above? Well, let me level the ground.

03:21

Yeah. Let's separate those terms first. Because you said, I said, what's altimetry? And you said something about and use the word height? Yes. So that's distinct from the word altitude. Yeah. So what is height? So height is your distance above said objects to the ground easily whereas altitude going.

03:53

You can say something when you learn the two uses of the words in aviation yeah. High is your distance above the runway and altitude is your distance above sea level. Yeah, your flight level is your distance above a datum, 1013hpa, here. So say we should make sure we use the word height and altitude.

04:17

Which I hear people use the word high incorrectly all the time. And since I haven't done any general aviation for a long time, I've not set the QFE no, for a very long time. No me neither. I used to love it. They because when you touch down it reads zero at the threshold.

04:33

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Pressure Altimetry

Yeah. And when I was in the circuit I just flew out a thousand feet, I didn't have to fly it. Yeah, 1270 feet. Exactly. So I missed the QFE. So let's talk about barometric altimeters on our aircraft on the, on the airbus. So what have we got in the flight deck barometrically?

04:52

Well, I've got a PFD. Yeah, my colleagues got a separate, PFD primary, flight display, yep. With this most amazing altimeter, which I take for granted. The display is what I'm referring to, yeah. Because the three-pointer style altimeter, the drum barrel style and so on have been attributed to accidents by pilots misreading, miss reading them.

05:19

Yeah. Various and so they like to use combinations of those but the one that we look at is so clear. Yeah. And the way they've integrated, which will come on to radio altimetry on top of. Yeah, pressure altimetry. Yeah, is really good. And we also have standby instruments in the flight deck, which may be an older fashioned style of display display.

05:43

But like a lot of things on the aircraft, we have three separate sources. Yes, that's important of air data. Yes, which we can kind of move around the displays, but you should have in normal situation, three, separate displays of three distinct separate air data. And if one of them is unserviceable, you could turn that one off and still have three displays, but from two sources, right?

06:12

Yep. So we like three things for redundancy and complex. Yeah, airliners okay so we're wherever Manchester Leeds Heathrow takeoff on wherever just the places we've just been with, we would would depart on the local QNH here for that airport, which would obviously. So they are reading on the altimeter would be the heights, the elevation, essentially of that airport above sea level.

06:43

So yeah, 200 feet, 250 feet, wherever 600 is 600 leads. Usually, yeah, LHR is what to 200? Just under 200. I think mean sea level, that's what they say mean. Let's sea varies in like I don't know, the tide maybe anyway. Well yeah, that's a whole, that's a whole podcasting itself if you want to fly really close to the ground.

07:06

Yeah, your best staying away from pressure, altimetry. Yeah. So you don't have to worry whether the sea is gone up or down a few, a few feet that day. But, yeah. So I've got a really good story about flying very close to the ground, which I the, you know, about, but we'll come on to that later on because that's exciting.

07:22

I hope it's not like me or you doing there and everything. Okay and so he throws a couple hundred feet leads, for example, sits on a hill leads Bradford says 600 feet. So when you're sat in your aircraft, doing your pre-flight checks and you have a look at your altimeter, it should say, and 600 feet in leeds.

07:42

Yeah, exactly. Yeah, okay. Providing you set the QNH it's correctly. So then you take off and if you had just all flying around the circuit leeds down initially climbing out on the standard instrument departure, you'd stay on that QNH until you reached the transition level which I hate the definition of transition level and transitional altitude.

08:03

Yes, it messes with my brain but luckily for me practically you don't need to really know where it is. No, when you're under radar control. No, exactly. And the idea being of that that once you've passed through that everybody sets standard pressure which is 1013 millibars. Hmm.

08:22

So that if you take enough from Heathrow on a QNH of say 1 0 0 3 and somebody's taken off from Manchester on a QNH of 1 0 0 1 and you're converging to each other eventually once you've gone through the transition level everybody's on 1013. So we've all got the exact same.

08:39

Yeah, pressure setting because when we take off from Leeds and there's the peak district around or the Yorkshire Dales, and then we want to know what our altitude or high is reference to the terrain. Yeah. Yeah. But once we're away from the terrain so they'll set the transition level.

08:58

Well above any terrain for that country? Yeah. Because I think in the states is like 10,000, maybe yeah. Yeah. Some places are really high. The UK is different to be a six usually between six and seven thousand feet normally. So once we're above well above terrain, it doesn't really matter how close to the train.

09:16

We are as accurately as it matters. How close we are to other craft. Exactly. We need to know what our altitude is with reference to their aircraft and like you're saying if there's high pressure down in London and slightly lower pressure up, north it leads, then as you travel from one place to the other, you're going to be on different QNHs , exactly.

09:35

It's just not going to work. So you all need to be on the same pressure setting. Yeah. So that so that we're all nice and separated. Yes. From each other. Not from the terrain. No from each other. Exactly. And we usually use a thousand foot separation and this is it.

09:52

It's kind of emphasises the importance of making sure that you have your QNH set, but also it also links into every as long as everybody's on the same. Then you're always going to have a thousand foot separation if somebody's unless you're altimeters not working. Correct. Yeah. That's yeah. Absolutely.

10:10

So a thousand foot separation is our RVSM? Yes which isn't been around forever. No, I think 2002 and Europe led the way of RVSM. Yeah, and be. Yeah. 2,000. Yeah. 2,000 feet was separation version and it's doubled amount of aircraft. You can fit in a box of airspace essentially.

10:32

Yeah so they eventually did it over the Atlantic as well so again went from 2000 foot separation to 1,000 foot separation and I learnt that something I didn't know which is that during the implementation of that. They, they being the regulatory bodies, wanted to know how accurate, actually, everybody was keeping their altitude, right?

10:55

Because now are only a thousand foot separation. So they wanted some kind of check on it, right? So did you know that they actually geometrically measure our altitude in Europe in that busy busy part of airspace with something called height measuring units. Okay. So they get the ping off the transponder like how GPS works using the time.

11:21

It takes to ping that aircraft to a certain station and another station on another station. I think they except they triangulate it. So they work out your geometric altitude. Nothing to do with your pressure reading, nothing at all, and they compare it to what you're supposed to be flying, right?

11:38

And they actually hone in on certain airframes that have bad altitude, keeping? Okay. And then they all contact the company and say, you know, G-BBBA. Yeah, is always flying 200 feet low, okay, that's interesting. And they can also track certain manufacturers or so aircraft types and say that aircraft.

12:00

They're not keeping initially or not. And they're always 100 feet low and you can see these graphs of where they've intervened and then the altitude keeping's got better. So vertical separation is so important to safety that they needed to introduce RVSM. But they were so worried about altitude, keeping that they, I'd ever realised that they actually monitor our geometric altitude to see if your aircraft, your company, your manufacturer has good alternatory.

12:34

That's really interesting. I didn't know that. I'd not really bother. Yeah, I didn't know that, you know, we could go on just loads. So you could talk about the they downsides of thousand foot separation. In terms of how busy and TCAS or did you look into überlingen air crash for this?

12:54

I didn't but I know. Yeah, I I was tempted to but I didn't either. So I have to look at that another time but that is that maybe that's another podcast. Yeah, I think so. Yeah, be a good one. So TCAS is a system that helps us keep vertical separation when things have gone wrong.

13:10

Basically? That's the same busy piece of airspace that where they first introduce RVSM. Yeah. But I just like exploring the idea of like, what you say, basically you're out. Altimeter is not really an altimeter. Yeah. Yeah. It's just a, it's just a barometer like your granddad might have on the wall.

13:30

Yeah, house. Yeah, haven't you got one, yeah I have. I have got a barometer well then and then basically it's just someone's painted over the barometer with without you. It's a lie. It's a lie. Yeah. But everyone's telling the same lies. Why at the same time?

13:44

Yeah. So that's fine. So it's really a pressure measuring device that we can use to approximate our altitude. And I think, the more you appreciate that will perhaps, try and store that away. The more you will just always have in the back of mind that there's a limitation to this device.

13:58

That is so crucial to the operation. And, and not put all your faith into it, because obviously, there's accidents, where incorrect, pressure settings, or problems with the, the system and failures, of course, like big loss of life. And I just like also you know, understanding that the pressure is higher sea level and the pressure.

14:22

Reduces you go up for one simple reason gravity. So obviously the effect of gravity is stronger towards the earth so the air is denser and as you get higher and higher and higher, the air gets less and less dense. And so I just I just like the simplicity of that, but the relationship of pressure with height is not linear and temperature it is but that but we rely on the temperature might not be.

14:51

There's all these problems with our altimeter but we get it to work through all sorts of international standard atmosphere and then these super, super accurate altimeters which are just measuring pressure. Like, see practically. So I just thought. So I'm like if you go from A to B on one zero, one three and you're going from high to low, then to high pressure again, you're actually riding the 1013

15:13

Like isobar almost. Yeah. And we're all doing it. So, it's fine. Yeah, you're actually going up and down. Yeah. You just have no idea because when I'm sat in the cruise, and I want to feel like I'm sat on the top of like a tower, that's labelled, FL350 and then my aircraft dips, or the speed, like just very slightly and I get annoyed with it.

15:34

Like, what's this doing? Little do I know, you know, like I always say we try and operate the aircraft so precisely to the nearest foot, you know. It's the nearest kilo of fuel flight to the nearest knot of airspeed, but the environment that we operate in is so imprecise.

15:49

And this is like the best example of it. But because what is out, what is altitude is? Yeah, it's a lie. It's a lie because we just use this standards kind of 30 feet per hectopascal. For example, you, you're talking about your your wave of 1013 if you took off somewhere, pressure, setting of 1030 and flew not very far.

16:12

Maybe a couple of hours to someone that was like, 1 0 0, so 30, millibars different. Yeah, you actually will be like a thousand feet lower. Yeah, the time you get there but you wouldn't know that because you asked me to still read the same. Now it's a massive fudge.

16:28

And then when you think about you think, well hi what's the what do they call the earth is oblate? Spheroid with the geodetic mean, so the ground is growing up and down. Anyway, yeah, as much but at least everybody's just doing the same thing. So hopefully hopefully with these super super accurate and then this is the problem, isn't it?

16:46

Like the air is there's a lot more volume to the air than the ground. We're light used to be in these 2d people really who live on this one plane and it's like, I so crowded down here. Yeah. But then, you know, like a skyscraper of apartment shows you how much more space there is when you go up?

17:04

Yeah. Right. That's why like, you know, when it's 5pm and everyone leaves the offices and then they're all stuck in traffic because they all live in high. They'll work in high-rise officers and then there's only one plane for them to drive on. Yeah, right. But in the air, there's loads of planes because there's well a thousand feet every time fee.

17:22

Yeah. But the problem I'm saying is we all fly so precisely and laterally on navigational tracks, that sometimes you can go ahead to head of an aircraft. Yeah, which is ridiculous. Yeah, so like we offset our lateral tracks sometimes just to introduce a bit of randomness but we don't offset vertically.

17:39

Probably for good reasons. But you know when I was doing GA I used to fly around like at 3,000 feet exactly or something. So everybody I should have just like, yeah, shit. I just feel like maybe was I doing the wrong thing, you know. introduces some randomness. Yeah.

17:53

It's everyone's at 3,000 feet is true. That's true. And and then perhaps before we move away that just the the idea that yeah, when you, you're basically measuring the out, another way to think of me is you're just measuring the weight of the column of air above your aircraft and so if if it's warmer or cooler, that affects the density of that, that thing that that you're measuring.

18:16

So yeah altitude is BS, but it's super important. So we've established it. What's your favourite pressure setting? I've never really thought about that ,1013 probably. Yeah, and when I'm doing like simulators running simulators, it's just easier to just do one two or one.

18:35

Three serious. Yeah, that's not realistic. Okay, sorry. Well, I was gonna say, so, it all works as long as everybody's doing the right thing and we fly around on standard once or one three to get to where we're going. And then we start descending to to land somewhere and this is the more dangerous way coming down.

18:54

Yeah going you know doing your altimeter check is you mentioned on the ground that he threw at the start of the day is fairly straightforward because you're on the ground. You checking the elevation and you take it off up into the air? Yeah. Well there's nothing. You're gonna hit coming down towards the terrain and the ground.

19:08

That's where problems are going to arise and going back through the transition level onto local QNH. You have to change your alternator setting. Now this is where this is where problems can occur. For example, with like language barriers, etc. So you often hear this set QNH is mm-hmm.

19:29

So if you heard, if the QNH was say 1013, when you heard 1033, that's 30 big problem. Yeah, that's already said what? 30? Well, yes, goals is a thousand feet, so known as a problem for the ground, that's pretty bad. It's also a problem for other aircrafts because they, that was obvious.

19:52

Yeah. Well, like the different, you know, like a few hundred feet might be easy to miss. Yes, that's true. That's true. And that could create and, you know, maybe we'll talk about this, but on a non-precision approach. Yeah, that could kill you. Well, yeah, exact on an non precision approach.

20:08

The QNH is the only thing that you're flying on with reference to the ground. Really? I was thinking because sometimes do you ever think about? Like the end of the world situation and somehow you've got your hands on an aircraft and you're gonna go and fly your family somewhere. Alright?

20:21

Right. So you've got no air traffic control. Yeah. So you can set the QNH yourself on the ground. Yeah. Because do you know the elevation the airport? Yeah but if there was never any radio communication with the ground and you were flying somewhere different and you had no met information.

20:35

Yeah. How could you ever know what the local pressure was? You have no datum, you wouldn't to come into land because if you are flying to a remote airfield, like in general aviation, you kind of set the regional QNH, or sometimes they'll say, you get it from this airport and then you adjust it to this local airport or you?

20:56

Just there's a there's a certain tolerance or something. Yeah, if you had no met information at all, you would never know what the local QNH is. You just have to head towards the ground. Yeah, as the impossible, basically? Yeah, although I'm starting to think about other source that we've got on our modern aircraft.

21:13

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Radio Altimeters

So, the radio altimeters. So, maybe this good times to talk. Yeah, about that. So, so when, when might, you know, you've missed at the QNH then, well, so when you're already out to me, it goes off. So radio, altimeters are more accurate way of measuring your altitude.

21:31

Well, your height above the ground? And it's basically like a well, it's just a radio signal. Yeah, bounces off the ground bounces back to the aircraft and calculates your height in feet above the ground. That is directly below the aircraft. Yeah. So and it's important, if you're stupid like me, you might think it's called radar altimeter, but it's radio and it doesn't use.

21:56

So I think for example, like, combat aircraft would have like ground following radar to fly into enemy territory. So it's totally different to that and it's only it's just a simple radio. Yes, signal suit super high frequency signal between. It's about 4,000 megahertz, yep. And it's like some kind of weird frequency modulated thing and basically they bounce it off the ground and the difference.

22:21

It's essentially the time that they're measuring yet to your height above the ground. It's a slightly different and we got two of those anyway. Yeah, not just one. Yeah. See two those and that's a good point. Why don't we just gun then cross check? You know, you could cross check your yeah.

22:37

That's that might so where you would trap that you buy a miss set the QNA. If your radio altimeter is reading two and a half thousand feet and you're expecting your barometric to be the same. And it's not, that could be a catch, but we can't just to make the distinction.

22:51

We can't use that in the well, we don't use it anywhere above two and a half thousand feet. No. And I think due to the design of the instrument you can't. No because it'll be too much error. I believe you can't use it in the masking now why don't you just use that?

23:05

Yeah, but again like I said it's not relevant in the opacity because you want everyone to be on the same data. Exactly. You don't want to be some guy over one. Town is you feet higher than yeah. And if you see what it literally measures the ground right beneath you.

23:19

So exactly. So, you know, relevant so it's not relevant. There might be a massive hill underneath you. Yeah, you might actually be 5,000 feet above the aerodrome that you're landing at. But only two and a half thousand feet above the hill. That's directly below. You. Tell anyone else.

23:31

It goes off. He's flying across the Atlantic. Yeah. It's black at night. Yeah. There's nothing below you. Yeah. And it suddenly goes. “500” wouldnt is say “1,000”. Okay. Yeah. There you go. But a thousand. Yeah. Why is it done that obviously? There's an aircraft has passed directly below you.

23:50

Yeah, at a thousand. Exactly. A thousand feet below. You and obviously the audio J following it as well. Yeah, it can stay you radios right over. It has picked up the aircraft, believe you and thinks it's the ground. Yeah. Yeah. The use for thousand because it's on all the time.

24:04

Yeah and when the wheels when you when you have to've lifted off and so if you ever get intercepted by like a secret fighter jet or UFO, you would know about it. If you underneath you. Yeah. There's you can't turn that system off. So that's very accurate. And that is true if you like compared to this lie of barometric.

24:24

That is literally telling you to the foot. How high you are here above the ground. Yeah, and like you say, it's at that moment. So yeah, talking about the North England. Again, if you're on a kind of like bass leg for RWY23 Manchester, it'll go off. And when you're over there Peak District there.

24:45

So it's a trigger for most SOPs. I think when that goes off, you'd be a fol to ignore it. Yes. So what kind of what do we do when it goes off. So we've verify we you know, in terms of our situational awareness. We love hopefully pre-briefed where we expect it to go off, right?

25:05

And that will verify whether our position is correct whether we've got the QNH set correctly, did it go off where we expected it to go off? Has it gone off earlier than we expected? Does that mean? We're not where we thought? We are etc. Etc. It can help. I think I had it go off in a hail storm once actually but it's pretty good apart apart from very very rarely.

25:25

And yeah. So we we check our essay and including the pressure data. Yeah, at that point. Yeah we also use it for our stability as well for our stable call. Don't we? Oh yeah most airlines use similar but maybe yeah. Actually the thousand foot radio call 500 radio calls more infallible and yeah, not ignore the verbal.

25:49

You can't ignore the save The radio. The read radio, altimeter has a display on the PFD. That's how we know it. And it also has this beautiful like, the actual horizon, the the brown horizon starts to come up to rise. This is such a good display and even a red tape comes up.

26:07

Yeah. As you get close to the ground, but also and the manufacturer and the airline chooses certain callouts of, which there should be one at 2,500 1,000 feet, 500 feet your decision height. So you can use the radar to to ping to ping those off, which I think is what you're saying, which is, which is good.

26:30

So we use it for a thousand for another thing. It's good for is measuring the rate of change. Yep. So what system does it feed? That might be the last thing that could save your life in terms of controlled flight into terrain feast their GPWS, right? Exactly, yeah. Same warning system.

26:49

So all those like, you know, too, low, terrain warnings, terrain, pull up, those kind of things. It's the rate of change as well. Yeah. So it can't necessarily look. Well, it can't look ahead of the aircraft, although, we now have aircraft with a database over the map in, which helps the enhance.

27:04

But also, if the ground is approaching, yeah, then it then it doesn't, it doesn't like it. And but it builds a basin around there, an airport to allow you to, to get close to the terrain without spooking it. So now and then it's, I don't know if it came in at the same time, but it's really crucial for one of our automatic systems for auto land.

27:25

Yes. Yeah. So we wouldn't be able to auto land without the radar altimeter, radio alternator. I see. This is the problem. I feel like I want to say that. So to be clear it's the radio. So yeah. So that's how the aircraft manages to do. What we normally do that eyeballs.

27:43

Yeah. Which is flare and which it does a really good job of really good. And it's the height of the landing gear above the ground. It's calibrated for. Yeah, I think that's why occasionally on the ground. It reads minus because then the landing is compressed, it's slightly compressed. Yeah, yeah, minus one.

28:00

I minus two. Yeah. Yeah. Don't come and see that. Okay, so you sort of touched on something else there, which we could talk about. So you mentioned, an auto land, we use the radio alternator. Yeah, auto land would typically be often ILS approach and instrument landing system. Yes, essentially flying a beam, both lately and yeah, vertically.

28:22

All like across hairs all the way into the airport. If you haven't got an ILS approach which a lot of airports don't have then you are flying. What we call a non-precision approach. Where we are managing the vertical profile ourselves and the only reference we've got to start from, is the is the QNH?

28:43

The? Yeah. So even on our approaches, although there's kind of more modern ways of flying those. They're still based on making sure that you've set the correct QNH. Yeah. Otherwise, nothing will save you. Exactly. Say, an ILS is a precision approach, and we like to fly now non-precision approaches as precision like approaches, which means that we're using, it's basically GPS.

29:12

But, you know, it could be your inertial sources to navigate an area navigation. Are you not following them down a beam? So, you know where you are, but you're not directly going in tracking inbound to something. So, it's a non-precision approach using area and navigation, which can be very, very accurate.

29:31

However, vertically, there is no element to it. So, you have to have the right pressure set in all your screwed. Yeah, GPS altitudes available, but it's not part of the approach whatsoever. No. So that's interesting say just to be clear for anybody out there that ILS is you could haven't, you could do it without altimetres, if you could lock onto that beam.

29:54

Yeah, there's a vertical beam and there's a lateral beam and that'll take you down to the threshold of the runway as well. So you all the way in, but on approach, you need to know that this distance from the runway. I need this pressure altitude. Yeah, yeah, exactly. So GPS altitude is not used by us at all, apart from in, sort of back door, play redundancy.

30:20

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Aeroperú Flight 603

Yeah, failure of the air data interesting that it's not, we might, we might cross reference it. Yeah, so lots of lots of potential. It's it's leading me towards a couple of accidents that I've looked into. Yeah. Okay. A couple of things that you've said. Yeah go okay well Aero Peru, okay what happened there?

30:42

Then I haven't looked at Aero Peru but I feel like I know the accident you'll know it. So unfortunately arrow Peru 1996 B757 the aircraft had been. Oh yeah on the ground and they covered the static ports with they call it like masking tape, some kind of tape. Right.

31:02

Wasn't picked up by the engineers, wasn't picked up by the Captain on the walk around took off and all hell break loose in terms of aural warnings and stuff because they essentially got ground level air trapped in the static port because it had been taped over. Yeah exactly. And so let's think that through.

31:24

So, would that affect their takeoff roll? No. No. Because the airspeed would come from the pitot. Yeah, but it's minus the static. Yeah. But say, wouldn't be affected until you climbed until you climbed when you when the static should decrease. Yeah, because we do cross checks on the air data on takeoff, which could prompt to rejected takeoff.

31:47

Yeah. So they got airborne and some pretty crazy stuff happened. It's really, it's amazing that they didn't crash for so long. I don't know what the duration of the flight was, but it makes for a really upsetting sort of series of events. Because this the situation awareness in the flight deck, sort of breaks down and down and down.

32:09

However, the first officer seems to have kind of a grasp of what might be the problem, but can't really convinced it's not that he's advocating it but it seems like he has more of a chance of doing the right thing. The couch in total loss of SA and I wanted to kind of work out if they had memory drills for unreliable airspeed.

32:31

At this point on the B757, which you assume they have all they are not. I wish I'd got to the bottom of that, but I haven't but they are aware that they have contradicting information. Yeah. Because the aircraft is they say over the radio all the time, the aircrafts accelerate in even though there are idle power.

32:53

And basically, they're stuck at 9,700 feet on the altimetres, right? And a lot of the time the GPWS system is aurally. Warning them. So unfortunately at some point they ask air traffic control. What their altitude is right? And the air traffic. Controller tells them, it's 9,700 feet and they accept that as a valid or one of the sources.

33:23

So it adds up to really break down their SA. But Sam, where's the air? Traffic controller. Getting the information. Well yeah from exactly the same source as they often that transponder. Yes. So the information that the air traffic controls got is erroneous, so just to be clear that thing that I mentioned earlier, height monitoring unit is so obscure we don't even know about it.

33:42

There's no real-time data for the out for the radar controllers on the ground to measure your altitude, geometrically or anything like that. There's nothing like that available. The pressure altitude that you have in the flight deck is transmitted via data. To the control on the ground. So if you don't know your altitude, they don't know on the ground.

34:03

So if you're in an unreliable speed situation, you tell them or possibly turn off the mode C of your transponder if the controller doesn't stand that. So in this accident, unfortunately, the amount of alarms in the flight deck was horrible. They also had like, you know, EICAS for like rudder and mack problems that were due to this and this chain of events, but it was just adding to alarms alarms alarms.

34:28

So we don't know what their altitude was doing, but we know that the GPWS was doing, it was saying the right thing. So a lot of the time they're very low but we know their lateral track and the captain does kind of have a good idea. He's like, well, if I can get on the ILS then I can land.

34:49

Yeah, but at no point. Do they do the Unreliable speed drill. So and I've said this before but basically the captain had like 20,000 hours. FO first I've said like 8,000 hours staring at altimetres that were working correctly right now. They're not, but they weren't able to blank them.

35:08

No, you know, sometimes it'd be nice to have a sheet of paper and just put it above across the altimeter, or the airspeed. Yeah. Because otherwise, your eyes are gonna get drawn into it. Yeah. So I just so, your brain is saying, look there look, I've run this in the simulator occasionally just to show people where you get an unreliable static because we always do unreliable air speed right?

35:29

I've showed them a block, static pool. Yeah. And it's amazing that you can feel the aircraft climbing, right. And the pitch is climb pitch. Yeah. But the altimeter is just staying for. Yeah and not moving horrible. It doesn't feel right because we spent so many thousands of hours looking at it and it just isn't, right?

35:47

It's just not. So, that was so powerful for these guys that they disregarded the GPWS warnings, right? They believed, what the air traffic controller was telling them, but yeah. It just stayed the same altitude, the whole time. The display. Yeah. And then in the way it ends is horrible because they, they think they're sort of, they kind of trying to troubleshoot it.

36:07

There's not too much structures to it, but the wing clips the sea and they're like, then they they realise. Oh, we've just hit the sea. Yeah. But then they have another 20 seconds, maybe of of trying to climb out right. But I don't know what damages occurred, but they're still flying and in a even though they've actually hit a bit of the sea.

36:28

Yeah, it's crazy. And then eventually they get sort of go inverted and go into the sea, at this point, the FOs, trying to sort of advocate, a little bit that the GPWS is probably reliable is almost getting there. So, the things that we've talked about already, they're relevant, are that your instruments are fallible?

36:46

And you need to understand their limitations? Yes, that the ILS doesn't use any barometric data. So, apart from you need to find your way on to it. So how and something else? I think we picked up on was relevant to this accident as well. Of course, now we'd have GPS altitude data, we could kind of cross check that.

37:05

Well, that's bullshit altitude. And yeah, also just that the radar ultimate is totally different system. So if that's going off, you know, and we have specific training on this. It's not as ambiguous as I'm about to make out to be. But some, you know, what do you believe? Do you believe the stall warning

37:22

Do you believe you're a airspeed tape? Do you believe the GPWS system? Do you believe your pressure altitude? So you need to be aware a little bit of the technical aspects of these systems. Think which one? Which one is likely to be reliable? And what's the chance that they're both wrong?

37:38

That's how. Can my GPWS? And my barometric altitude. Both have failed today, but so many alarms in the flight there definitely wasn't helpful. I am say, that was one. And then unfortunately, another B757 took off in the Caribbean and an insect had decided to move into the static port.

37:58

I is, it's Birgenair and it is a charter flight and it and that had blocked the static port, right? And that accident is, my memory is failing me now but it was different but was blocked. Static port on our 757, not to not too long after so that's a shame but what I wanted to find out which I didn't find out.

38:23

Was now I feel like we've got very rigid drill for like if there's any ambiguity here? Yeah. About the air data. Yeah. Then we go into a memory drill. Yep. We it's a look it up or anything like that and we go back to basics if you like, which is pitch and power to power and we can fly the aircraft safely on pitch and power.

38:43

Yeah. And to a point where we can troubleshoot, but until that point, we don't look at one of the three and go. That's the right one. That's the right. Yeah. Because we don't know at that point, right? But it seems like and these accidents that that wasn't as explicit as like, okay you go into the memory journal so they're the accidents that I'd looked at specifically with regard to altimetry.

39:06

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Dambusters

Yes. So I I didn't look at an accident. I looked at something kind of more anecdotal and something I found really interesting and you talked about it, flying low earlier was the was the Dambusters, you know, you know that I love this. But and for any of you that don't know, sort of the detail about the Dambusters and I've only heard about it.

39:30

I'd strongly urge you to watch, there's multiple documentaries on it, but the one I watched was with Dan Snow the presenter, really, really interesting. But essentially, so when they were creating the bouncing bomb to try and destroy these dams in Germany, so much, testing went on as to what the perfect altitude or height was to drop the bomb to let it bounce along the reservoir and hit the down bear in mind in the, you know, 1940s the best altimeter out.

40:08

There was an old three dial barometric. Which, you know, would only really accurately measure to 100 feet. So it wasn't really, very well calibrated, but like I said, earlier, you can't ask the Germans for the QNH. No, exactly. Yeah. And yeah. Exactly. You can't ask me. Yeah. Just as you come into, German airspace.

40:27

Yeah. Anyway, so you say this, so what they found was that 60 feet above the water, was the perfect height to drop the bouncing bomb. So the question was, how do you fly at 60 feet at night without knowing what the QNH is from the Germans? So they came up with this really clever system, which was basically two torch lights mounted to the front of the, of the Lancasters.

40:57

And essentially, they were calibrated to such an angle that as the aircraft came over the reservoir at night time. Obviously generally, perfectly flat level plain the, the reservoir, these two torch beams move closer together and when they made a perfect figure of eight on the water light on the water, that was exactly 60 feet.

41:19

And I just thought that was such a nice anecdotal story of like, altitude and altimetry like 60 feet. These guys were flying out and literally just as simple as two torch lights. Yeah, could fly. So accurately. Right, what works? So clever ingenious way and then they would obviously drop then.

41:37

I drop the bouncing bombs from from that 60 feet. Say, I just thought I'd share that as a as a sort of little side story on altimeter, I like it because well there was a point in terms of navigation where we did it all by using ground-based system.

41:53

So you'd fly in towards the beacon and then turn away in the way you want to go outbound on a beacon? Yeah. And then we started using area navigation which we still use ground-based stuff. Now, we're moving to a world where it's stuff on the aircraft, you know, so you you're making on-ever approaches using GPS.

42:11

Yes. But then the GPS isn't actually on the aircraft. Everybody thinks that I'll never go down, which probably won't because there's multiple systems now, but it has caused accidents in the past and people have been shot down because of their navigation error. So in the same way, in terms of altimetry, it's like what can we have on board.

42:29

We got this wicked radio altimeter now which is but wonder if other on board stuff like the GPS will become yeah. Relevant you know, in the upper atmosphere or yeah. Possibly. But there's guys in the Dambusters they have to have everything. They're not gonna get any help from the ground.

42:47

Yeah. Yeah. Every system had to be on on board system. Yeah, you're not gonna have an ILS into your target site that bomb. Yeah. Everything had to be on board including the altimetry. So two, light bulbs, two light, bulb one, just had spare light, but what if the filament went?

43:02

Yeah. Exactly. I don't know. Yeah, I mean interesting, yeah, it was such a simple piece of technology but worked perfectly, you did your brain, you listen to the radio radio ultimate call outs when you flare not consciously. No. You think you don't do it on that or well. I I don't know, maybe I do more now as a training captain because they teach that that's how we teach it for.

43:26

People learning to learn the airbus and maybe I'm more conscious of it. Now it, what about like the texture of the ground? Or, you know, do you actually have a little of you have how low you are? Yeah, I think it's more on judgement now by just looking out the window and judging it was supposed to look at the end of the runway.

43:42

It's not that I'm saying. So yeah, exactly. Whereas I think in your early days, you probably did use the radio altimeter, more as your gauge to help you flare and land. Yeah, yeah. Well hope we've destroyed the concept of how to meet us. So next time passenger says, you know or you make your PA how high we are but I wouldn't suggest you tell the passengers.

44:02

We don't really know just so just guesswork. But we're all doing anything. Yeah exactly. Don't worry about it and yeah. I think we've then we've talked about some interesting, interesting, sides to our altimetry there. So yeah. Thanks very much, bye.

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