Calibrated sight gauge on header tank by adding measured amounts from graduated container. Marked quantity on header tank in 1/2 gallon increments. Checked calibration by draining into graduated container. Header holds 4.0 gallons. Header sight gauge reads accurately at all fuel levels.
Calibrated sight gauges on wing tanks by adding measured amounts from graduated container. Wing tank sight gauges do not indicate any fuel until 2 gallons have been added. With 2 gallons gauges indicate 1 gallon. Approximately one gallon remains when gauges read zero. This error proportionately decreases with increasing quantities until gauges read 9 gallons when 9 gallons are actually in the tanks.
Inspected all fuel connections from both wing tanks to the header tank and from the header tank to the engine side of the firewall. All connections secure.
Inspected both wing tank vent lines by blowing through vents. No back pressure noted and airflow heard at filler neck.
Added 1.0 gallons to left wing tank. Flowed left wing fuel to header tank. Header tank sight gauge shows 0.85 gallons. Left wing tank contains 0.15 gallons (0.9 lbs) unusable fuel.
Added 1.0 gallons to right wing tank. Flowed right wing fuel to header tank. Header tank sight gauge shows 1.85 gallons. Right wing contains 0 unusable fuel.
Flowed Header tank fuel through fuel system to firewall connector and from firewall connector into a graduated container. Container shows 1. 75 gallons. Total unusable fuel is 0.25 gallons (1.5 lbs).
Checked fuel sump drain system for leaks.
Flow Tests
With 2 gallons in header tank and 0 gallons in wing tanks (worst case scenario, minimum head pressure) measured fuel flow at engine fuel pump location using gravity flow only (boost pump off). One gallon flowed in 260 seconds (.072222 hr). This equates to a fuel flow of 13.8 gallons per hour. Minimum fuel flow required by AC 90-89A (150% of maximum calculated engine c
