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Headscratchers / Air Crash Investigation

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  • In the episode on British Airtours Flight 28M, which happened in 1985, the captain stated in his interview that he had aborted the takeoff because he thought one of the tires had blown. Yet the episode covering the 1991 crash of Nationair Flight 2120 made the case that blowing a tire during the takeoff roll wasn't sufficient reason for aborting a takeoff. How is that?
    • Different aircraft. Nationair 2120 was a DC-8 and standard procedure for a tire failure during takeoff didn't include aborting takeoff. British Airtours 28M was a Boeing 737. A major reason for the difference is that the rear landing gear on the DC-8 consists of 2 sets of 4 tires, so blowing a single tire on either side still has 3 tires on that side and 7 of the 8 tires in total to carry the load. A 737's rear landing gear only has two tires per side, so blowing a tire has a greater impact on the load carried by the remaining tires.
  • Is it normal for an airplane to land with the engines almost at full thrust as TAM Airlines Flight 3054 seemed to have done? (That's where the right engine was when it ran off the end of the runway.)
    • That was the whole point of the episode. One of the reversers wasn't working, standard procedure left the captain thinking he'd run out of runway, so he uses an outdated procedure that was scrapped particularly because this error could occur.
      • That wasn't my question; my question is why the right engine was at full power during the final approach.
      • See "Just Plane Wrong" in the main page-it was a mistake by the producers.
    • I get that the throttles at full power during cruise was a case of Just Plane Wrong; I'm talking about while the plane was on final approach, as in the last 500 feet before touchdown.
    • The crash of TAM 3054 happened because the right engine was at full power after touchdown, and neither pilot realized it. This troper's question was why either engine would be at full power at all during the approach and/or landing.
      • According to "Terror in San Francisco", airplanes need more engine power during the approach phase to overcome the increased drag caused by the flaps and landing gear.
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    • Was it on full power, actually? As the A320 nears the runway, the throttles are about 1/3 forward (the engines still have to generate enough thrust to, well, get the plane to the threshold). Slightly before touchdown, they are retarded (moved to idle position) so that the plane has optimum speed on contacting the tarmac. When the plane lands, the throttles are put into reverse to deploy the thrust reversers. This is how it should be done; the older procedure was to move both throttles to idle, then only the one for the engine with a working reverser was put in reverse, the other was on idle. The captain messed it up leaving one of the engines in a forward position, generating thrust; there were two separate problems here. First, with one engine producing substantial forward thrust, the plane would be slowing down much slower than usual (not to mention the flooded, short runway). The second, even more significant was that the right engine was pushing the plane forward, while the other was in reverse - a very difficult situation to handle. The engine did not have to be at TOGA (full power) on landing; the fact that it was not at idle and producing thrust was more than enough.
  • How is it that the first officer of SilkAir Flight 185 was a 23-year-old who'd been flying for the airline for over a year, and was already type rated on the 737 when he started flying for SilkAir? Do different countries have different pilot criteria, or...?
    • Depends on when he did start his training. And indeed the criterias vary (or at least varied two decades ago) - the captain must have a ATPL (airline transport pilot license, which means a minimum of 2000 hrs flight time), while in many countries, the copilot was required to have a minimum of a CPL (commercial PL, no less than 500 hrs) - a 23-year old copilot is not a particular stretch.
  • The National Airlines 102 episode makes the statement about restraining straps needing to be tied down at a specific angle to get maximum strength out of them. Is it even possible to tie down straps parallel to the floor?
    • Parallel to the floor, connected to the sides instead maybe?
  • How do the tape based flight recorders record data such that they can capture the flight down to the very instant the plane hits the ground? Do they record half the timespan's data on one side of the tape and the other half on the other side, or...?
    • Tape-based flight recorders, for both data and voice, recorded in a 30 minute loop, therefore preserving the last thirty minutes of flight.
  • Why is a criminal act one of the first theories (if not the first theory) considered in most accidents? Especially by aviation experts, who should be able to pick up on patterns in the way accidents have happened.
    • Because its always a possibility when the cause of the crash is unknown. And the difference between mechanical failure and deliberate sabotage is not always immediately obvious.
  • How would a passenger know about the presence of a cruise ship near their flight's destination in 1998?
    • If memory serves, its presence there was planned, and a pretty big deal, which was why there were loads of yachts and private planes — including a photojournalist — hanging around to get a look.

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