Pragmatic 11A: Cause And Effect Follow-up 1

20 March, 2014


Follow up (Part A) to Cause And Effect with more detail on the Aeroperu crash courtesy of listener Dean Lombard.

Transcript available
This is pragmatic follow-up part a for episode 11 cause and effect. I'm Ben Alexander and my co-host is John Chichy. Hi, John Hey Ben. Thanks for that. So I had an excellent grateful email from gentlemen by the name of Dean Lombard and one of the great things about the fact that it was so many people listening to the show is that every now and then you come across somebody who's Got a lot more in-depth knowledge and experience about the topics that you're talking about. It just so happens that Dean is somewhat of a fan of this aircraft, air crash investigations. He actually has a book. The book itself is called Black Box. There's a link to it in the show notes. It was published by Harper Collins in 1998 and edited by Malcolm McPherson. What it is, the full title is The Black Box Cockpit Voice Recorder Accounts of In-Flight Accidents. It actually does mention the Aero Peru crash that we mentioned in the cause and effect main episode. He's written a very good list of a couple of extra details that I'd like to read out excerpts from his emails. He actually sent me two emails on the subject. So, first of all, regarding the CVR, sorry, CVR is cockpit voice recorder. So the CVR transcript, he says, is a very harrowing read. The pilot and co-pilot are completely baffled. They're getting such contradictory information. They are getting a stall warning and an overspeed warning at the same time, even though they were applying the spoilers and had cut the engines back. the pilots still believed the overspeed warning above the stick shaker stall warning. Just pausing there for a second, when aircraft are about to stall, in other words, they're not going fast enough in order to actually stay in the air, they actually drop out of the air if you go any slower, the sticks literally shake. That concept was brought in a decade or two earlier. The idea is that before autopilot was really a thing, pilots would sometimes fall asleep and they would ease back on the speed of the plane. It would gradually slow down. It's about to stall. The sticks literally then were programmed to shake. They would shake so that that would wake up the pilot. That was the whole idea of the stick shaker. Kind of like rumble strips on the side of the road. Yeah, exactly. Exactly. Good analogy. Just like that sort of thing. They're very effective but the problem was in this case, they were getting so much contradicting information that they ignored the stick shakers of all things, they ignored them He goes on to say, possibly because of the compelling evidence from the airspeed indicator Of course, the problem was the airspeed indicator wasn't indicating correctly either For ages, he goes on to say, for ages they believed they had control problems rather than instrument problems because their actions weren't reflected by the instrumentation readings and for a while they had it on autopilot which was of course was using incorrect data as its parameters. So the control tower was actually getting altitude data from the plane and speed data from the radar. So this is one of the things that people don't realize is that there's actually a connection between planes and aircraft towers towers that where the aircraft towers can actually get information from the computers on board the plane. They can cross-reference that information against radar readings. Anyway, long story short, the altimeter was reading 9,700 feet and that's just been confirmed by air traffic control. What they were doing was they were comparing the value that they were erroneously getting from the aircraft rather than from the radar, which meant that they were essentially reading back the value that they saw. Yeah, we confirm. They didn't realize that I was simply telling the airplane back, "Yes, and we actually have you at the wrong altitude." We really don't know because we didn't really check anything. Yeah, could the story get any more awful? Yeah, it's awful, just absolutely awful. See, all these things added up. It's crazy, terrible. Anyway, the overspeed warning, he continues, "The overspeed warning was still sounding along with too low terrain." terrain. If you watch the reenactment in, I think it was the air crash investigation, and in the reenactment when they're reading that part of the CVR transcript, you heard the alarm going off, "Too low, terrain. Too low, terrain. Too low, terrain." These pilots are trying to figure out what the hell is going on. They can't see anything, and of course, at which point, they hit the water at 300 miles an hour and it's all over. I have to say a very big thank you to Dean for that and he had a lot more of that information for me and it was great to get that feedback from someone who was into that and also has an interest in it. I haven't gone so far as to buy the book but honestly, if you are interested in this sort of thing, then there are books out there, not just this particular one, there's several of them and I think a lot of them are done by the same guy, Malcolm McPherson, I think has had several books, I believe, on the subject. I think that's an interesting addendum to the episode. Thank you very much for that feedback and that was all I had. [BLANK_AUDIO]
Duration 5 minutes and 36 seconds Direct Download

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Ben Alexander

Ben Alexander

Ben created and runs and Fiat Lux

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, software developer, podcaster, vocal actor and runs TechDistortion and the Engineered Network. John is a Chartered Professional Engineer in both Electrical Engineering and Information, Telecommunications and Electronics Engineering (ITEE) and a semi-regular conference speaker.

John has produced and appeared on many podcasts including Pragmatic and Causality and is available for hire for Vocal Acting or advertising. He has experience and interest in HMI Design, Alarm Management, Cyber-security and Root Cause Analysis.

You can find him on the Fediverse and on Twitter.