Thanks for the great site; you have helped me a lot. I am a regular flyer (about twice a week) and I don’t really get too anxious about flying anymore.
Anyways, just recently I have noticed that just before takeoff, the pilots lower the flaps or something along those lines so there is a slight hole in the wing.
I have only noticed this since I watched an air crash investigation in which the pilots had the flaps in the wrong position on takeoff and the plane spiraled out of control as soon as it left the ground.
Ever since I have seen this, I have watched the wing anxiously just before takeoffs to make sure the flaps are in the normal position.
My two questions are:
1. What would happen if the plane took off with the flaps in the incorrect position?
2. What type of safety measures are built into the plane to prevent the captain from beginning his takeoff roll with the plane configured incorrectly.
Thanks for any help.
I believe you are referring to the Delta 1141 Boeing 727 crash that occurred in 1988 at Dallas-Fort Worth International Airport, USA.
Yes, the plane took off without any flaps being selected. The crew did not ensure that the wing's flaps and slats were properly positioned for take-off, possibly being distracted by some conversation with the cabin crew. The contributory cause was that the take off warning horn that would caution the captain of no flap selection was not working as well.
The answers to your questions:-
1. The function of the flaps is to produce lift and enable the plane to take off at a lower speed. Without flaps, the plane would require a higher speed to take of. For example, a particular plane would normally take off at 140 knots with flaps 2, but if it were to take off without flaps, it would only lift off at 170 knots. So you can imagine if the captain thinks he has flaps 2 when in fact he has none selected and lift off at 140 knots - the plane would stall and crash as has happened in Flight 1141.
2. All commercial planes have safety feature to warn the captain if the plane is incorrectly configured for take off. There is a warning mechanism whereby a horn will sound when the captain apply power for take off if he forgets to select flaps for take off (which means he must immediately abort the take off). Prior to that, there is another switch, a take off configuration warning button whereby the first officer will have to depress as part of the “Before Take Off Check List” If it sounds, something is incorrectly set and corrective actions must be taken to continue with the take off.
To prevent distraction as has happened in Flight 1141, a “sterile cockpit” policy is introduced in all airlines whereby the pilots must not be involved in any unnecessary conversation with the cabin crew until above 10,000 feet in the air.
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