TAP Portugal Airbus A320 Strikes Wingtip
On Lauda, a miss-rigged sensor was causing auto-restow to cycle (sensor would go target far, auto-restow would snug the reverser up tight, sensor would indicate target near, auto-restow would close the isolation valve, vibration and flight loads would move the T/R a bit and cause the sensor to go target far and the cycle would repeat). On one of those cycles, for reasons that were never firmly established, the DCV changed state to 'deploy'. The aircraft was at ~24k, Mach 0.78, max climb - with the engine at power, the eflux from the deployed reverser effectively destroyed the lift on that entire wing and they rapidly rolled into a dive. Although the FADEC commanded the thrust to idle, at those conditions it takes well over 10 seconds for a PW4000 engine to decel to idle - by which time it was already too late and the aircraft was coming apart.
The addition of the third lock, along with stricter maintenance requirements, pushed the probability of an in-flight deployment from ~10-8 out to ~10-13/flight hour. Prior to Lauda, a T/R deployment in flight wasn't considered to be catastrophic - and had happened multiple times with the older low bypass and pure jet engines - no body appreciated how the introduction of big, high bypass engines tucked up relatively close to the wing had changed the impact. They had actually tested an in-flight T/R deployment during 767 flight test - but they'd done it at 10k, 200 knots, with the engine already at idle - 24k/Mach .78/climb power was completely different.
Interestingly, the relevant FAR still says a T/R deployment in-flight must be shown to be controllable - so the Boeing cert basis is an "Equivalent Level of Safety" - basically showing it'll never happen (in regulatory lingo, 'never' is "extremely improbable" - a probability of 10-9/hr or less). EASA has changed their CS to basically say 'controllable or 'extremely improbable'.
Join Date: Apr 2007
Location: Lisbon
Age: 53
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
Couldn't the T/R just have been deployed on the 2nd landing with a shutdown #1? Low LH hydraulic pressure (PTU unable to cope) resulting in the partial stow.
The sloppy go-around could be a flameout of #1 on balked landing at low energy/high drag condition?
The sloppy go-around could be a flameout of #1 on balked landing at low energy/high drag condition?
Only half a speed-brake
Does not really fit the FCOM limited explanation
- there is an accumulator on the system
- the four petals are operated by a single (?) hyd valve
- by the looks of it, each petal is hinged to the actuator to weathervane shut if not energised
- there is an accumulator on the system
- the four petals are operated by a single (?) hyd valve
- by the looks of it, each petal is hinged to the actuator to weathervane shut if not energised
tdracer,
Thanks for your informative post on the TR history. It’s always been of a subject of interest to me since the Cranbrook crash. The FO was a friend of mine.
Thanks for your informative post on the TR history. It’s always been of a subject of interest to me since the Cranbrook crash. The FO was a friend of mine.
I was heavily involved in the Lauda investigation - by far the most difficult thing I had to do during my career. It was the only fatal crash investigation that I was directly involved in, and it really started getting to me emotionally, particularly as it quickly become obvious that engineering wise we'd missed something - and made all the worse that (as I've noted on other threads) you're basically under a gag order during the investigation - I was only allowed to discuss it with other people involved in the investigation. I could never have been an accident investigator - emotionally it was just too difficult to isolate the impact of what had happened.
If you want more details of the TR history, PM me...
Heartfelt post, tdracer. Many of us tend to forget that engineers are human and have deeply-felt emotions. It's not all equations and experimental results.
My father, who held a Mechanical Engineering degree from the Georgia Institute of Technology and a Masters degree in Marine Architecture from The U.S. Naval Academy at Annapolis, designed aircraft carrier hulls, specifically the Essex class.
I never saw Dad cry often, but every once in awhile, when there was a carrier accident (e.g. Forrestal CV-59), he would stand staring out of our library's bay window for a long time, then turn, wet-eyed, to embrace me and my mother.
Engineers have brains - big ones. Engineers have hearts - bigger ones.
- Ed
My father, who held a Mechanical Engineering degree from the Georgia Institute of Technology and a Masters degree in Marine Architecture from The U.S. Naval Academy at Annapolis, designed aircraft carrier hulls, specifically the Essex class.
I never saw Dad cry often, but every once in awhile, when there was a carrier accident (e.g. Forrestal CV-59), he would stand staring out of our library's bay window for a long time, then turn, wet-eyed, to embrace me and my mother.
Engineers have brains - big ones. Engineers have hearts - bigger ones.
- Ed
DAIB preliminary notification (press release) is out; 3 out of 4 TR doors on the no. 1 engine did not stow when TOGA was applied.
https://havarikommissionen.dk/media/...orfly_ekch.pdf
Whilst the press release doesn’t say, one can maybe infer that the crew elected to go-around after deployment of thrust reversers. If TR were not selected by crew, and the doors “decided by themselves" to open asymmetrically on one engine only, that’s a whole different - and much scarier - scenario.
Press release doesn’t say why crew decided to go-around.
https://havarikommissionen.dk/media/...orfly_ekch.pdf
Whilst the press release doesn’t say, one can maybe infer that the crew elected to go-around after deployment of thrust reversers. If TR were not selected by crew, and the doors “decided by themselves" to open asymmetrically on one engine only, that’s a whole different - and much scarier - scenario.
Press release doesn’t say why crew decided to go-around.
Last edited by SMT Member; 19th Apr 2022 at 16:45.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,403
Likes: 0
Received 0 Likes
on
0 Posts
Whilst the press release doesn’t say, one can maybe infer that the crew elected to go-around after deployment of thrust reversers
