Recent Float Experience
Flew out to California last Wednesday 3/23/05 and returned last night 3/27/05 with some long weather circumnavigation legs (4.7 hour longest - 55 gallons onboard - probably 51 usable) and the float/EI instruments worked just fine. When the red light comes on (the last one in the quantity remaining sequence) the tank is still delivering fuel to the engine but it is a real attention getter. I am sorry that some of my carefully recorded data appear to be lost, especially the long leg into the wind from Silver City, New Mexico to El Monte, California but some survived. With changes in attitude such as a climb followed by a level off the tip tank lights would change from red back to green briefly because of the long tank configuration and the float position; downdrafts caused a similar response. The engine is O-360-A1A, 2450 rpm, leaned 50 degrees rich of peak EGT, tank system is LT (left tip) = 8.5 gal, LM (left main) = 19 gallons, RM = 19, RT = 8.5. Santa Ana, CA to El Paso, Texas fuel burn (time-hours/refill quantity) LT(0.7/6.1), LM(1.7/11.9 - a lot of idle time at SNA), RM(1.7/14), RT(0.6/5.2) - so the 10gph flight planning assumption gives a little margin. The RM was yellow - occassionally went red and showed 3 gallons remaining and the LT was indicating a similar status. On the leg from El Paso to Oklahoma City the numbers were LT (0.6/5.1), LM(1.4/12.3), RM(1.05/~10.4), RT(.5/~4) - the fill numbers are inaccurate on the right side as I did not catch the precise number after the RT was filled before the RM was started - close but not exact. Conclusion - for me this supports my earlier assumption the the indications are sufficiently accurate and the quantity remaining sufficiently conservative to permit safe operations in the 10 GPH fuel burn/5 hours out of gas flight planning and direct gauge indications of low fuel anomalies.
P.S. I found the Silver City to El Monte Data:
RT (0.6/5.9), RM (1.2/11.5), LM (1.6/14.2), LT (0.5/4.3)
No change in conclusion.