Hi Steve,
I suggest you seek a means to accurately monitor in-flight fuel consumption. A good first step would be to re-coat any and all cork floats before starting.
Go flying with a short builder's level (or 6" "torpedo" level), some duct tape, and half of an old wooden clothes pin in the plane. Trim the plane for level flight "nose down" at whatever RPM you normally use for cross-country flight. Set the level on your sidescreen sill and tape down the end the bubble moves to. Slide the half clothes pin under the other end, wedge it as necessary to indicate "level", and tape it in place.
After landing, sandbag your tail cone higher (or let air from your nose tire) until the taped level again reads "level". It is only after doing this that you can calibrate useful "in-flight" fuel remaining information from your fuel tank gauges.
Get a five gallon bucket and another small bucket. Pour a measured gallon of water in the small bucket and mark the fluid level with one or more thin paint lines to "calibrate".
Mark the wire on your nose tank gauge (or the tube on "rain-proof" gauges) with a red line you can see from the cockpit. This is the "normal", or FULL indication for your nose tank. Loosen the fuel line from the firewall at the gascolator and CAREFULLY remove precisely one gallon of fuel into the small bucket. Drain remaining nose tank fuel into the five gallon bucket, and tighten the fuel line back on the gascolator.
Pour your measured gallon back into the nose tank filler. Your gauge wire won't move. Measure another gallon from the five-gallon bucket and pour it in. Your gauge wire still won't move. Measure out and pour in another gallon. If the gauge moves, make another mark where it rises to. Measure out and pour in each remaing gallon, so marking. (If you're marking a bare wire gauge, it may be more lasting to paint the area red between alternate marks) When you have less than a gallon remaining, carefully measure it with a measuring cup before adding it back.
You now know precisely USEABLE fuel from your nose tank, because the "full" level was determined in flight as supplied by the fuel pump and as limited by the return line(s). If you keep a record of your fuel purchased and accurate time in your pilot log it isn't rocket science to get a fuel burn per hour for each fuel purchase.
You now also know you have significant useable fuel remaining when your nose tank gauge "thumps bottom". Use your WORST figure in the last six months for (conservative) fuel consumption expectations when flight planning, and you now know how much of your nose tank fuel you can SAFELY use and still preserve (your choice) 3/4 or 1/2 hour landing reserve. Some put a BOLD mark (or one of a different color) to indicate desired "reserve" on the gauge.
Now, fly the wing tanks dry (so the nose tank gauge drops from the calibrated "full" mark). Put 1.1 gal. in one wing tank and then .9 in the other. They should level within a minute. If the gauge moves, mark it. This is a two-gallon mark. Repeat the process (as you did with the nose tank, except you now work in two-gallon (or 1/8-tank) increments. Now you will know precisely USEABLE fuel in YOUR wing tanks according to YOUR gauge, because this fuel was removed the same way it is removed when consumed in flight. Unuseable fuel is just that... unusable!
If your coupe doesn't have a functional wing tank gauge, substitute one of the "rain -proof" ones for a filler cap. It's true you probably lose some fuel to siphoning the first few minutes of flight, but that lost fuel is purchased and is therefore allowed for in your fuel burn calculation.
Too much work? How long would you have to work to earn, after taxes, the cost of a fuel totalizer system of comparable accuracy, installed? It's CHEAP confidence!
Now remove the sand bag or reinflate the nose tire so your coupe sits "normally" again. (You can also remove the taped level from the sill) You could go through the above again to calibrate your "Fuel Hawk", but I would just immediately mark "full" for wing and fuselage tanks and in the future when landing with wing tanks at 3/4, 1/2 and 1/4 full (as indicated in flight just before landing, stick them and note the reading.
This should give you sufficient data to draw a graph of readings for the "Fuel Hawk" sufficiently accurate for most needs. It also allows you to "gauge" fuel this device cannot measure because of wing dihedral.
Regards,
William R. Bayne
<____|-(o)-|____>
Copyright 2004
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On Oct 1, 2004, at 9:00 PM, Steven Finkelman wrote:
A few days ago I posted a message asking whether
anyone has calibrated a dipstick or "fuel-hawk" measuring device for coupe wing tanks.
I have received a couple of requests to share any
information I receive, but have not heard from anyone
who has done this.
I am making one last check to see if anyone can help
with this task.
I am willing to give it a try if no one has done it, but
I need some advice about the crossfeed in the wing tanks. It obviusly would not work to simply drain one
tank and then measure it as you fill it up, since the crossfeed would confuse the situation.
The only way I can think of to do this is to drain both tanks and then to fill the tanks in unison so the crossfeed would not give a confusing reading.
It seems like a project for a nice summer afternoon, which unfortunately, we are quickly losing.
Once again I would appreciate any help anyone can offer.
Steve Finkelman
C-FIWR
