Headscratchers / Mayday

• 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One of the reversers wasn't working, standard procedure left the captain thinking he'd run out of runway, so he uses an outdated procedure that was scrapped particularly because this error could occur.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.
    • Is there a reason that couldn't also be Just Plane Wrong?
  • 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.
    • Still, applying full thrust with fully deployed flaps (as per landing) would lead to them being torn off. The newer aircraft like the last two generations of a 737 actually have automatic systems that raise the flaps when too much thrust is commanded by the pilot. The pilots do increase power before landing to compensate for increased drag, but nowhere near full thrust.
  • 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?
  • Or tied to a raised loop or track or something.
• 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 loop (30 minutes seems to be standard, but there are some that are longer), therefore preserving the last thirty minutes of flight. It's mentioned in a few episodes (most notably the Helios crash) that they weren't able to get relevant information because a plane stayed in the air too long after the actual incident occurred. As far as how they get all that without it then being taped over, the recorders only run so long as they're receiving power from the aircraft, so they're automatically cut off on impact or, in the case of a safe landing, when the engine is shut off. (Or if power is cut/the system is disrupted in some other way — some cases of in-flight fire, for example, are missing the last few minutes because the fire burned through a power line or connection.)
• 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.
  • It's not really most accidents anyway. It's generally only if it fits the parameters of a criminal act, and if the cause isn't already known to be something else. If the plane blows up/breaks apart in midair for no apparent reason, a bomb is a possibility, especially if other risk factors are involved (there's someone important aboard or it's a politically tumultuous area).
• 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.
• Why did the pilots on UPS 6 decide to go all the way back to Dubai rather than diverting to the much closer Doha, especially given that the manual was telling them to land ASAP?
  • To have more time to prepare to land and to achieve a controlled, smooth descent in a fairly crowded airspace? Plus some time to dump and/or burn excess fuel to land at lower weight.
    • Unlikely, since Doha wasn't so close as to inhibit this; while it was closer than Dubai, they were still more than 100 miles away, so it shouldn't have been so close that they would have trouble getting down in time. Familiarity might explain the decision, but in retrospect, it's a decision that may have cost the pilots their lives. (Interesting that the episode doesn't spend any time on this factor.)
• In the Uberlingen disaster, why didn't the Russian pilots just tell the controller about the TCAS conflict? If they had told him "Our TCAS is telling us to climb" instead of just debating the issue among themselves, the controller would probably have realized his mistake and told them to follow TCAS, crash averted.
  • You get the reasoning (implied) in the episode itself - practice in the former Soviet Union is that the controller's instructions can override TCAS commands, whereas Western practice is that the TCAS trumps controller instructions. It can be as simple as them assuming/believing that the controller has a better picture of what's happening and him giving conflicting instructions is for a good reason (ie TCAS is partially failing on their plane and giving unreliable/wrong data).
• The first officer involved in the Detroit airport collision was filed by one troper under Miles Gloriosus. The guy definitely exaggerated his achievements, but still he was an Air Force pilot who retired as a major - very unlikely that he was a Dirty Coward with Feet of Clay, which Miles Gloriosus is. Would The Münchausen be a better trope to describe the man? Or some other trope would fit better?
• In the United Express Flight 6291, how did the ice that the investigators found on the wings not melt in the fire?