Re: Fuel dump switch in homebuilt

On Tue, 02 Dec 2003 17:09:41 GMT, Kyler Laird <[EMAIL PROTECTED]>
wrote:

>Ron Wanttaja <[EMAIL PROTECTED]> writes:

>>>>Well... as far as homebuilts are concerned, fuel exhaustion (defined as the
>>>>pilot running the airplane out of fuel) plays only a minor role in the
>>>>overall accident rate.  During 1998-2000, only 4.5% of all homebuilt
>>>>accidents involved fuel exhaustion (including some accidents that occurred
>>>>during precautionary landings due to a low fuel state). 
>>>
>>>How many of "all homebuilt accidents" involved an "emergency landing"?
>>>(I don't think we mean "landing" to include "falling to earth in pieces".)
>
>>About 20% of the homebuilt accidents in that period involved a loss of
>>power due to mechanical failure of the engine or fuel system (vs. pilot
>>mismanagement of fuel or power system).  About 15% engine related, about 5%
>>fuel-system related.
>
>So are you saying that there's a 1:1 relationship between losing power and
>making an emergency landing?  No one loses power and performs a stall/spin
>return to the ground?

Certainly, to a depressing extent, especially when the engine failure
occurs on takeoff.  I apparently didn't make my point clear:  Another
poster commented that "If you are making an emergency landing in a small
plane, chances are that you don't have any fuel left on board to dump."  My
response was meant to counter this, in that fuel-exhaustion-related
accidents were a relative minority.

>I'm just trying to get back to the point about fuel probably being already
>exhausted when an emergency landing is executed.  Are you saying that three
>of every four emergency landings are made with significant quantities of 
>fuel on board?  

No.  All I said on my original posting was that 4.2% (I posted "about
4.5%") of all homebuilt accidents in the January 1998 to December 2000 time
period (29/692) involved fuel exhaustion.  I make no claim about how much
fuel remained in the remaining 660-odd accidents that year, other than to
guess that the NTSB investigator apparently considered there was sufficient
fuel on board to rule out lack of fuel as a reason for a loss of power
situation.

>(Another complication is that it's fairly common to still
>have gobs of fuel on board even when fuel starvation is the cause of the
>accident.)

Out of the 29 cases of fuel exhaustion, two cases involved a crash during a
precautionary landing due to a low fuel state, one involved the fuel tank
unporting when the pilot maneuvered at low attitude with a low fuel state,
one had a bad header tank, and one pilot failed to select his reserve tank
when the main tank ran dry.  Three cases of extremely low fuel, two of some
amount of fuel.  In the remaining 24 cases, the engines quit because the
pilot used up all his or her usable fuel (one case included a leaking fuel
tank).  That would still leave several gallons aboard each aircraft.

In ~660 accidents, then, the airplane crashed with sufficient fuel on board
to have enabled continued flight.  I personally don't think a fuel-dump
valve would have helped in most of these cases.  But I suspect it's like
the ballistic parachute argument; if you need one, then you REALLY need 
one. :-)

Ron Wanttaja