Re: Fuel Dump Question

Date:         30 Nov 98 03:07:37 
From: (MCL757)
Organization: AOL
References:   1
Followups:    1
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>I went through the FA 25.1001 and found that for turbine engines:
>    (f) For turbine engine powered airplanes, means must be provided to
>    prevent jettisoning the fuel in the tanks used for takeoff and
>    landing below the level allowing climb from sea level to 10,000 feet
>    and thereafter allowing 45 minutes cruise at a speed for maximum
>    range. However, if there is an auxiliary control independent of the
>    main jettisoning control, the system may be designed to jettison the
>    remaining fuel by means of the auxiliary jettisoning control.
>    Since dumping of fuel is used for an emergency which requires the
>    plane to land ASAP, (are there other uses?), why would the FAA want
>    the fuel dumping system to retain enough fuel to climb and fly for
>    45 minutes? Is this to allow for a missed approach? Do missed
>    approaches really take that long, do planes really climb back to 10k
>    feet?
>    Is the dumping of fuel something which is done in circumstances
>    which are not actual emergencies and which require the plane to
>    abide by congested airport queing and waiting (thus requirememt to
>    stay in air 45 minutes) or is fuel dump done only in circumstances
>    requiring immediate landing and thus declaring emergency which >gives
>    the plane immediate access to the runway of its choice?
>    If it allows for an auxiliary system which dumps all of the fuel,
>    and such system has no requierement for a minimum reserve (5 minutes
>    flight?), what's the point of the first fuel jettison system? Or is
>    such system used only for maintenance purposes and not to be used by
>    pilots?

The way that the regs are written, it sounds to me like the main concern is
that thee FAA doesn't want it to be possible to dump too much fuel... so much
that the aircraft runs out.  I'm not sure, but I figure that the system that
would dump the fuel leaving enough for a climb to 10,000 and 45 minute reserves
may be a gravity dump system with just valves open, but to dump more than this
a auxiliary system is neccessary.  This would be the regulation that decides
how high to mount the dump pipes in the tank..... according to the regs, just
high enough to leave enough fuel for a go-around and some holding.  I'm not
100% sure on this, but that is what it looks like to me....

To answer your other question pertaining to dumping...  Fuel dumping is not a
normal occurance that is taken lightly... if there is a dump, it is usually a
pretty big deal.  I think the standard fuel reserves are 45 minutes for any
I think the main aim of this reg is to prevent the design of an aircraft from
enabling the dump of too much fuel and the aircraft running out of fuel.

>    Why does the FAA not mention a need to reduce to a bare minimum is
>    the amount of fuel so that if the landing doesn't go too well (UA
>    232 comes to mind), the resulting fire will be as small as possible?
>    Seems to me that 45 minutes worth of fuel is a lot.

The reg just requires the primary (?) dump system to leave this much fuel, the
secondary can dump even more, but once you are below your max landing weight a
safe landing is probable... of course that changes if you have no hydraulics.
I think the FAA is more concerned about the aircraft having enough fuel to get
to the airport than reducing the amount that will burn on a crash landing...
it's all up to the Captian...

Matt in Seattle, Student Pilot... My Unofficial Alaska Airlines Mailing List is
----Fly Alaska Airlines, Horizon Air, and Continental Airlines!!!