I agree with Wayne that any coupe whose fuel system has the gascolator,
or fuel filter bowl (see Parts Catalog, p. 26, Item 54), mounted low on
the forward face of the firewall is subject to unanticipated fuel flow
interruption in the manner he describes. Some Forneys and coupes (not
Alons) have been retrofitted with this firewall-mounted gascolator by
well-intentioned but uninformed owners or mechanics.
I agree that this would seem the most likely cause of the recent crash
in Portugal.
Wayne's solution should be in the preflight checklist of any and all
such airframes.
Regards,
WRB
--
On Mar 26, 2010, at 07:49, Wayne Woollard wrote:
Ed:
I have advocated for many years that there is a serious problem with
tha architecture of the Alon fuel line routing.
The problem shows up if the fuel line is shut off at the base of the
header tank, and work is done on the remaining fuel system, or if the
header tank is drained for any reason or if all the fuel is consumed
and it is refilled.
A basic fact of hollow lines is the fuel weight is enough to create a
small amount of fuel pressure at the carburetor, but this is not
enough weight to allow an air "bubble" to pass. A bubble of air in
the fuel line will only allow a limited amount of fuel to pass by, and
will act as a partial restriction, although THE LINE IS NOT
RESTRICTED!!
This simple fact along with the fuel line routing to the Alon
Gascolator setup and beyond are the cause of many frustrating takeoff
incidents, wherein the equipment failure cannot be duplicated.
If you push down the tail of an Alon to duplicate the "Takeoff" angle
of attack and you have recently refilled your fuel system, an air
bubble can occur between the output of the header tank and the input
to the carburetor. This "Can" be duplicated by draining the header
tank, and the loop in the fuel line at the carburetor input, then
refilling the fuel tank and powering up the airplane, go through all
the check lists, and taking off on a 3 mile long runway, such as
Castle, and see for youself. Halfway down the runway at an altitude
of 200 feet the engine will quit from fuel starvation! Plenty of room
remaining to land, but not so at a "Normal" airport.
Solution: Bleed the air from the fuel line connection to the
carburetor by disconnecting it and holding it to a position below the
lowest point in the fuel system till the fuel runs smoothly without
air, and reconnect. following all the safety procedures of course.
D. Wayne Woollard CPBE
o--iii---(
