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Old Feb 25, 2010 | 10:29 am
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jbcarioca
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Thrust reverser deployment in flight is generally unrecoverable, and very, very rare

Originally Posted by gougoul
I had it one rather bad on JFK-GVA.
Really mininal service (food was flying around, so it didn't really made sense anyway), they tried to fly over it, failed, beside, failed, under it, failed.

At the end of the day, I drank a glass more wine, and got some sleep

Turbulences seem dangerous but it's very rare that a plane goes down because of them (unless it's landing/starting). Most of the time, you rather have people who get killed/hurt because they are not wearing the belt.
To give you an idea what an airplane can sustain, I recall (It was an Asian carrier, not sure it was Korean...) that once in an MD11, once from the FC activated the thrust reversers in flight, you can imagine what kind of constraints that puts on the airframe. There were fatalities, but not because the plane went down...
Technically thrust reversers on transport category aircraft will not deploy without an actual landing, that is weight on the extended landing gear. There have been a tiny number of incidents where that happened, notably a 1991 crash of a Lauda Air Boeing 767 with a loss of all on board, which resulted in disabling all 767 thrust reversers while that was fixed. The DC8 once could have thrust reversers deployed in flight and some B737-200 models were modified to permit it. Despite those it is a certification requirement for all aircraft equipped with thrust reversers that they cannot be deployed in flight. No MD11 ever had such an incident on record. Some turboprops can have their propellers reversed in flight (the ATR 42-72 being notable) but most of thsoe not incorporate the "squat" switch also that precludes reverse deployment without weight on the landing gear. There is colorful history on this subject, mostly involving incorrect rigging and inadequate preflight inspections. That said, don't worry about it, it is almost 100% certain that such a thing will never happen to you.

As for turbulence, turbulence can and has caused inflight breakups. No commercial use aircraft can withstand unlimited weather. There is a speed, called "turbulent air penetration speed" that is the maximum speed permitted in turbulent air. That speed is the one below which the aircraft will 'stall' before structural damage can happen. Without discussing load limits and 'stall' definitions, this means that a well maintained and piloted aircraft can endure some very frightening weather. I've been in such weather as both a pilot and as a passenger. The passenger side is probably less of a strain... anyway accidents in turbulence are indeed very, very rare.

There are quite a few FTers who are type rated on jet aircraft, including me, so if you want more pilot perspective on any of this kind of thing just ask, and they'll emerge to venture informed opinions, and will correct me quickly if I hjave made any errors in my comments.
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