Re: Fuel dumps

From: (Brian A. Reynolds)
Organization: Rockwell Avionics - Collins, Cedar Rapids, IA
Date:         08 May 95 02:09:09 
References:   1 2 3
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Fuel jettisoning is coverd by FAR 25.1001.  In (f) of 25.1001, "For turbine
engine powered airplanes, means must be provided to prevent jettisoning
the fuel in the tanks used for takeoff and landing below 10,000 feet and
thereafter allowing 45 minutes cruise at a speed for maximum range."

Taking into consideration that all aircraft also have some quantity of
unusable fuel, by definition one can never dump all of the fuel on board.

In 25.1001 (a); "A fuel jettisoning system must be installed on each airplane
unless it is shown that the airplane meets the climb requirements of 25.119
and 25.121(d) at maximum takeoff weight, less the actual or computed weight
of fuel necessary for a 15-minute flight comprised of a takeoff, goaround, and
landing at the airport of departue with the airplane configures, spped, power,
and thrust the same as that used in meeting the applicable takeoff, approach,
and landing climbe performance requirements of this part."

25.119 deals with Landing climb; all-engiens-operating, while 25.121 is
Climb: one-engine-inoperative and (d) deals with approach speed.

Being in Avionics I haven't delt with this issue before, but found this brief
exercursion through the regs to be interesting in that the requirement is
tied to speed and not to landing weight (where I thought it would have gone.)

With this in mind, then it is indeed a safe assertion that the engineers
made a decision as to how much fuel to leave on board.  Based on economics,
(increased landing gear capacity = higher construction AND operating costs)
I would think that dumping sufficient fuel to get below the maximum gross
landing weight (a figure required to be supplied in the Flight Crew Operating
Manual and one established by the capability of the landing gear) for that
airport and weather condigions would be sufficient.

The views expressed are my own, the Company has their own!