RV-4
Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 15; Flight Crew Total 4990; Flight Crew Type 4970
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
General None Reported / Taken
Aircraft; Human Factors
Reduced engine power due to fuel starvation (unusable fuel) in left main tank on final approach. Engine continued to run erratically during the final approach until the aircraft was rolling out in 3 point attitude. Landing was otherwise not a problem; flare and roll out were completed in normal manner. Because the engine faltered during the final seconds of the approach; correct action was to maintain full attention to the landing flare and directional control rather than switching tanks (the right main tank was nearly full). With assistance from line crew; we simply pushed the aircraft off the runway to investigate.It seemed that it might be helpful for aviation safety purposes to report the factors leading up to the incident:1. Left main fuel gauge inaccurate (during flight; the gauge indicated 1/3 full; plenty adequate for the planned fifteen minute flight; but trust in the gauge; even for such an estimate was trust misplaced.2. Aircraft had been refueled recently; with less than two hours flight time since fill-up; therefore; based on fuel consumption rate; amount of fuel in the left main appeared adequate (but visual inspection with fuel stick was not performed).3. Investigation after the incident revealed a slow fuel leak (drip) via the tank drain. Fuel level in the tank had been visually checked less than 24 hours before but was NOT checked again immediately before flight. It should have been. The drip had apparently had the same effect as excessive fuel consumption; usual factors and calculations were inadequate under the circumstances. So here's my conclusion as to avoid such a situation in the future:Do not depend on timing of fuel consumption as a substitute for visual inspection; even for a short flight; even when the aircraft 'should have' plenty of fuel; based on normal fuel consumption factors. Also do not depend on a fuel gauge for such a calculation! Thinking I still had adequate fuel; 1/3 full; in the left main; I didn't switch tanks before starting the approach to landing...I should have switched to the full right main. On the other hand; it occurs to me that changing tanks that late in the pattern and approach might have also been problematic. In other words; I should have switched tanks to the right main well several minutes earlier before making the approach.Final thoughts:Check fuel visually; before every flight; even if you refueled the aircraft the day before the flight! This; because even a minor fuel leak out through a tank drain may simulate excessive fuel consumption; throwing off calculations; fooling you into thinking 'I've got plenty of fuel; just gassed the airplane up!' When the engine started to miss; I believe that directing my full attention to final and flare was the right decision; even a second's attention to switching tanks at that point would not have been wise. Because I use aircraft for aerobatics (and desiring lower weight/less than full tanks during flight maneuvers) visual check with a fuel measuring device may also be a necessary protocol. Further irony: I was landing to top off the left main tank with fuel I had on hand there!Though this was a comparatively (and thankfully) minor incident; I report it with the hopes that other pilots in similar circumstances can avoid trouble.
RV4 pilot reported a loss of power on short final because of fuel starvation.