This particular incident, the pilot rejected takeoff "due to a aft door indication".
My questions are:
- Is it a such serious situation so as to reject take-off?
- If the pilots had taken off, could the crew have secured the door on their ascent?
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12$\begingroup$ Do you continue to drive your car if the "open door" warning light is on? $\endgroup$– n_bMay 20, 2018 at 22:28
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4$\begingroup$ @n_b If I have physically verified that all the doors are properly closed, then yes, quite possibly. I'd still want that fixed, obviously. That said, the risk involved in driving a car at, for all intents and purposes, 0 AGL is somewhat different from the risk involved in flying an airplane at 30k-40k ft AGL. $\endgroup$– userMay 21, 2018 at 11:09
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5$\begingroup$ @DavidRicherby They can't, but that's pretty much my point; you can't directly compare driving a car to flying an airplane. $\endgroup$– userMay 21, 2018 at 11:12
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2$\begingroup$ @n_b ... Yep! I open and close it whilst driving :D $\endgroup$– CloudMay 21, 2018 at 11:14
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3$\begingroup$ @Cloud the extra drag allows for tighter turns, if you do it right! $\endgroup$– Tin WizardMay 21, 2018 at 20:13
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2 Answers
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The crew has already secured the door just before leaving the gate, cross-checked them and the pilots saw the sensors indicate closed. So if the warning goes off during take-off roll, it is not somebody's simple mistake, but something is broken. It might be the sensor, but it might be something on the door and that might be pretty bad. So as the old saying is “it's better to be on the ground wishing to be in the air than in the air wishing to be on the ground.”
Below about 80 knots the pilots will (should) reject the take-off for almost any warning or abnormal indication they get. If the problem can be fixed easily, they can just taxi around and take off a couple of minutes later. Above that speed the emergency braking is likely to overheat the brakes, so from about that up to V1 pilots will only reject for engine failures and other very serious warnings, while for other issues they'll make the circuit and return to land again.
answered May 20, 2018 at 18:49
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9$\begingroup$ Your second paragraph describes the policy at the two 747 carriers I flew for. Also, though it wasn't in the op specs as I remember, it was felt that any abort between 100 knots and V1 (typically somewhere in the range of 140 to 160 knots) would be a full blown emergency. $\endgroup$– TerryMay 21, 2018 at 2:35
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$\begingroup$ As I understand, a lot of warnings appear in the cockpit throughout the flight. The intent of my question was to understand, that a door indication alert was a big enough reason to abort takeoff. $\endgroup$– FireeMay 22, 2018 at 6:59
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1$\begingroup$ @Firee, no, there are normally no warnings except during preflight as either checks of the warning systems or during intermediate state when some systems are not started yet. A warning means something is really, really wrong that needs immediate correction from the pilot (a caution means something is wrong, but not as critical). In most flights you don't get any. In fact, most of the time there is very little beyond the flight and navigation instruments as indications are designed so that all lights are extinguished in the usual flight state of things. $\endgroup$ May 22, 2018 at 20:43
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Yes if prior to V1 (takeoff decision speed). On most modern airliners there are proximity sensors that monitor the latching system at various points, that will produce various warning or advisory messages (for example, a single sensor out of an array of several on a given door may provide only an advisory, whereas more than one sensor agreeing may produce a warning). The more minor indications are usually inhibited during takeoff.
If after V1, the pilot will continue the takeoff (although in extreme circumstances the PF might reject after V1 if he/she hasn't rotated yet; like say there is a huge bang, and the runway is really long; it's an instantaneous judgment call). If an advisory, during the climb-out the pilot may ask the FA to visually verify the mechanical latch indications and if ok he/she may carry on, or if a more serious warning he/she won't take any chances and will tell the FA to stay strapped in, depressurize the aircraft, and return.
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5$\begingroup$ Note that on a long runway, V1 will simply be equal to Vr. $\endgroup$ May 20, 2018 at 16:25
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3$\begingroup$ "in extreme circumstances he might reject after V1 if he hasn't rotated yet" I suspect the pilots of Air France flight 4590 would have loved to use that option... $\endgroup$– userMay 20, 2018 at 17:56
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12$\begingroup$ V1 is a decision point, generally selected such that, past this point, there is insufficient runway remaining to stop the aircraft. The safest option here is to go flying, declare an emergency and return to the airport. $\endgroup$ May 20, 2018 at 18:12
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15$\begingroup$ After V1, a pilot will only reject takeoff if they have reason to believe the airplane is unflyable. V1 is the point at which you no longer have enough runway to stop on, so you're basically trading a crash in the air for a crash on the ground. $\endgroup$– MarkMay 20, 2018 at 19:52
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1$\begingroup$ On 4590, a thin strip of metal cut a tire which blew up and caused the tank skin above it to rupture from the shockwave. The crew would have heard a little thump, at most, and when ATC reported flames, they may have assumed it was the engine flaming from a bird strike would continue the takeoff. $\endgroup$– John KMay 21, 2018 at 2:38