Impact of Flap

[stranger12]

Hi All,

I was looking at a documentry which can post the link if you are interested.

basically the plane did dive from 39000 feet all the way down in matters of few minutes and was saved from landing last minute.

when an investigation was carried out, boing believe the pilot had opened the flap to increase speed as this was what was rumeroud amongst pilots that opening it will increase speed.

and that resulted in the dive and one of the flat hinges breaking .

what are the danger of opening a flap at lets say 30000 feet art 600 nm ?

[Cusco]

The flaps depart the aeroplane and take the tailplane/stabilator with them......

End of story.

[stranger12]

know that , what I was asking is what happens if you open it at high speed in high altitude.

Banned Air Crash Investigation Trans World Airliness Flight Massacre or Accident - YouTube

in 1979 in 44 sec the boing 727 fell 33000 feet .

[BEagle]

This is clearly a reference to TWA Flight 841 which, on 4 Apr 1979, nearly crashed after a LE slat was extended during the cruise. The slat was ripped off and the aircraft entered an uncommanded roll. It is claimed by some that the aircraft rolled at least twice through 360° and exceeded M1.0 during the recovery, which also exceeded the g-limit for the aircraft.

Why was the slat extended though?

There was an 'unofficial procedure' among some 727 pilots for flying at extremely high altitudes. At 40,000 feet or so, the air is so thin that the 727 staggers along at a rather high angle of attack. Hoping to improve high-altitude cruising performance and handling, adventuresome 727 crews were known to deploy the first notch of flaps (2 degrees), which increases the effective wing area and might theoretically allow the airplane to cruise more efficiently. However, four of the eight leading-edge slats automatically deploy when the first notch of flaps is selected. Since it's obvious that leading-edge slats are a no-no at Mach 0.80, part of the unofficial procedure is to pop the circuit breaker for the slats so that they'll stay put during the flap extension. This gives the desired trailing-edge-flaps-only configuration. But if the flight engineer pops the wrong circuit breaker.....

Aircraft limits are there for a reason - whether for a 727 or a PA28, is immaterial.

[Pilot DAR]

The principles of training edge wing flaps are the same for all aircraft so equipped, though there are more factors involved with high altitudes and fast (jet) aircraft. The jet aircraft aspects of the discussion do not really belong in the Private Flying forum, though the subject of the use of flaps for a high speed descent could also apply to smaller general aviation (GA) aircraft. It is a good thing if "private fliers" are simply aware of other factors, such as mach speed effects, leading edge flaps, and true emergency descents (usually for depressurization reasons), just for increased knowledge, even though they don't really apply to GA.

Certainly with smaller numbers all the way around, the OP's observations could be relevant to GA aircraft operations. A high speed descent with flaps out can do damage, and I have had a broken flap track on a Cessna 180, which presumably was the result of a previous flight in that aircraft when damage was done.

Posts on the GA aspect of flap use and high speed descents would fit well into this thread. Jet aircraft operations, less so....