Hi Jim,
Great question! Awareness is an arrow everyone should have in their
quiver ;<)
With all the variations of vented and unvented caps, five and six
gallon nose tanks, different nose tank standpipe configurations,
degrees of gauge cork saturation, autogas vs. avgas, possible partial
obstruction of fuel strainers, possible partial obstruction of the
1/16" restriction in the outbound fuel line fitting on the fuel pump,
and possible corrosion in the fuel pump itself...I doubt there is a
one-size-fits-all "normal".
In various coupes I have at times noticed a variation such as you
describe, but only in cruise. To be honest, knowing the "bobber is up
before I begin the takeoff roll (and that there is an hour of operation
with that amount of fuel even with a dead pump), I just tend to ignore
what happens with the bobber in climb and look for traffic.
That doesn't mean I EVER ignore that bobber very long!
Mark that "fuel stick" for reference in cruise (trial and error,
starting with where it is after a runup). Later I recommend
calibrating your tanks for reliable fuel consumption information.
If you find that ANY "full power" operations suggest an inability of
your pump to "keep up", it's time to get serious about
trouble-shooting. Fuel pumps are way too expensive to replace
prophylactically when the problem is one of proper maintenance (crap
accumulating in fuel tank cap vents, fuel tanks, fuel lines, strainers,
orifice, or valve; detached header tank standpipe, etc.), but when
everything else is A-OK and pump output has dropped to the point that
you describe, it's time to rebuild or replace the pump.
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
--
On Mar 26, 2010, at 20:31, Jim Truxel wrote:
Folks,
I have a question. When I climb out in the Coupe, 415C, at 70 MPH , I
notice the fuel stick in the header tank guage seems to get lower than
normal. But shortly after I level off, the fuel inidicator goes back
to full normal showing. We just installed a new cap and float. I was
wondering if with full power and at this climb angle the fuel pump was
not able to pump fuel into the header fast enough. We have had no
problems with the bird in any other area.
First time we noticed this we got concerned and flew around the
airport before heading off on a flight.
Is this normal ? Next time I will try a climb speed of 75 to see
what that does.
Thanks,
Jim
N3439H
KFDK
----- Original Message -----
From: William R. Bayne
To: ercoupe list
Sent: Friday, March 26, 2010 1:04 PM
Subject: [ercoupe-tech] Re: Fuel starvation:
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---(
