Airplanes & Safety Margins

[Steve L]

Can anyone tell me to what extent are the safety margins on the payload capacity of the average aeroplane.  Lets take, for example, the average Boeing 757 - if, say the maximum allowable takeoff weight according to the air flight manual is 100,000 Kilograms, then how hard would Boeing have pushed that during testing ? Would they, for example, have managed to safely take off at 200,000 Kilograms and then set their maximum at 50% of that ???

(I'm assuming of course, there is some safety margin built in somewhere !!!)

 

 

[Clanad]

Design and production of aircraft, especially transport category aircraft as referenced in your question, is extremely complex.  The initial design and final testing of a new aircraft, in the U.S. are accomplished under Federal Aviation Regulation (FAR) Part 25. (small aircraft are under a different Part).  The simple answer to your question is that an ultimate fail load/weight factor of 1.5 times the operational maximum weight is required to be incorporated into the design.  This is influenced by many considerations including the strength of the landing gear and the structural integrity of wing structures.  Most of the world's aircraft manufacturer's have similar requirements because the aircraft cannot be operated in the U.S. unless it meets minimum standards of the FAR's, even though certificated in a different country.  Most of the countries have agreed upon standards.

By the way, your question intermixes differing terms that make it confusing to answer.  You reference payload and maximum allowable take-off weights.  These are two entirely different considerations.  My 1.5 allowance is related to the maximum allowable weight of the aircraft. This weight is function of design and would be achieved by computations and proven in static testing before flight was ever attempted...

[Steve L]

Thanks for the detailed response Clanad.  Thats just the kind of thing I was looking for.