Originally Posted by
Stan Woolley
tdracer
I remember reading a really interesting response to a thread by a man (I’m sure his surname was Green) on an aviation forum in the nineties. The conversation was about how best to deal with a reverser deploying after take off, as it’s a possible failure in the simulator. He had been( maybe still was) a Boeing test pilot. He gave me the impression that unless you were very very lucky, this was one failure that would end in a crash. I seem to remember him saying that they’d investigated the 737-400 and saying that the results of a failure of a reverser on that variant was pretty frightening. It of course had the sleeve type reverser, rather than the bucket type on the -200, which was even worse.
edit: He said that to have any chance you’d have to get the engine shut down very quickly, as well as getting above a certain speed (V2 + ?).
I was directly involved in the Lauda 767 investigation - probably the hardest, most unpleasant thing I ever did at Boeing. During the investigation, they were (coincidentally) running some 777 developmental thrust reverser efflux testing at the Boeing Vertol facility in Philly (useful as it had a moving ground plane capability). Well the wing/engine layout of the 777 is very similar to the 767 - just scaled up - so after the wrapped up the 777 testing, we went in and did some testing. It was a 'half model' - so a single engine with a wing and half fuselage - the 'engine' used a 'Turbine Powered Simulator' or TPS - high pressure air piped in through the wing and strut ran a turbine the drove a 'fan', while the TPS exhaust became the core exhaust. It was a good sized model - 1/10th scale IIRC. We removed the ground plane, changed the wing to a clean, flaps up configuration, and did a bunch of testing measuring the lift, drag, and controllability characteristics. It was almost funny - there was an Aero S&C guy there also witnessing the testing that swore up and down that the Lauda pilots had screwed up - that the deployed T/R was fully controllable - until we started testing. As the testing progressed, and he reviewed the data, he got really quiet. Being a propulsion guy, I didn't really understand all those control coefficients (I'd taken some Aero S&C classes in college, but that had been over 15 years earlier and I didn't recall much of it). But the last test we did was a flow visualization - they taped hundreds of yarn tufts on the upper surface of the wing and tail - and it was stunning. Nearly the entire upper surface of the wing was separated, as was most of the tail (both horizontal and vertical).
Ultimately it was determined that it simply was not practical to make an in-flight deployment controllable with the (then new) very high bypass turbofan engines, the only answer was to make sure it never happened. Hence the retrofit of the 'third lock' (aka 'sync lock', although not all installations use an actual lock on the sync cable).