Quote from
Boeing 727 Flight Crew Training Manual
Maneuvers - Cruise - Airwork
Flap Usage
Flaps are intended for use during takeoff, traffic pattern work and landing. Thus, flap systems are designed to withstand limited attitude and airspeeds and limited time exposure within these flight regimes. Use of flaps during enroute descents is not recommended and can result in operational problems and higher maintenance costs.
Flaps placard speeds at high altitudes have not been verified or FAA approved. The flaps are designed to accommodate the FAR maneuver requirement of 2.0 g's or a derived gust velocity of 25 feet per second at flap placard speed. These are for limited loads and ultimate loads are 50% higher. Thus with flaps extended the airplane has less tolerance to gust and maneuver accelerations than in the clean configuration.
At higher altitudes (above 20,000 feet) where aerodynamic damping diminishes, lateral control capability with the outboard ailerons active (flaps down), results in excessive ro]] rates.
Because of the above, flap extension is limited to altitudes below 20,000 feet.
- end quote
BTW: I don't know if they have covered the subject(s) but do take a look at Boeings Aero magazine on
http://www.boeing.com/commercial/aeromagazine/
[This message has been edited by dusk2dawn (edited 30 June 2001).]