Power Loss RV12 912ULS
in General Tech Discussion
8 years ago
POWER LOSS VAN’S RV12 ROTAX 912ULS
Today 3/14/2017 a friend flew a RV12 to Williams Arizona, KCMR. Airport elevation 6691 ft. outside temperature was low 70’s. Flight in was normal. When he went to leave, just after becoming airborne the engine stumbled and lost significant power. An aborted landing was successful. An A&P from Prescott, AZ was contacted. The A&P had built this RV12 as well as a second one he flies. The A&P flew the second RV12 to Williams. He checked the carburetor bowls for debris on the first RV12 as well as doing a full run-up. All seemed normal and no debris was found. A second attempt to take off was made by the first RV12. Again the engine stumbled and failed to produce full power. The decision was to leave the first RV12 in Williams and fly the second one back to Prescott, planning on returning in the morning. The second RV12 did a run-up, which was normal, and started the take off roll. The second RV12 experienced a similar engine stumble and extreme roughness. The second RV12 could not develop take off power. Both aircraft are Rotax powered with 912ULS engines. Both are identical in the fuel system and carburation. Both also experienced fluctuating fuel pressure during the attempted takeoffs.
Both aircraft were burning 91-octane auto fuel with ethanol, purchased locally in Prescott Arizona at two different locations. It appears that both aircraft experienced vapor lock while applying full power for take off. The weather has been much warmer in Northern Arizona than usual for this time of year. We believe the fuel, which is in all probability, a winter blend, has too high a vapor pressure, thus causing the vapor lock.
For those of you RV12 drivers using auto fuel at high elevation airports in warm temperatures BEWARE. Both RV12’s will be flown out of Williams tomorrow morning when the temperatures are expected to be in the high 30’s to low 40’s.
Until or when we can determine that the refineries are producing summer blend auto gasoline, we will be changing to 100ll. And may continue with 100ll during the summer months to avoid the possibility of vapor lock at high elevation airports, regardless of the auto fuel blend.
Today 3/14/2017 a friend flew a RV12 to Williams Arizona, KCMR. Airport elevation 6691 ft. outside temperature was low 70’s. Flight in was normal. When he went to leave, just after becoming airborne the engine stumbled and lost significant power. An aborted landing was successful. An A&P from Prescott, AZ was contacted. The A&P had built this RV12 as well as a second one he flies. The A&P flew the second RV12 to Williams. He checked the carburetor bowls for debris on the first RV12 as well as doing a full run-up. All seemed normal and no debris was found. A second attempt to take off was made by the first RV12. Again the engine stumbled and failed to produce full power. The decision was to leave the first RV12 in Williams and fly the second one back to Prescott, planning on returning in the morning. The second RV12 did a run-up, which was normal, and started the take off roll. The second RV12 experienced a similar engine stumble and extreme roughness. The second RV12 could not develop take off power. Both aircraft are Rotax powered with 912ULS engines. Both are identical in the fuel system and carburation. Both also experienced fluctuating fuel pressure during the attempted takeoffs.
Both aircraft were burning 91-octane auto fuel with ethanol, purchased locally in Prescott Arizona at two different locations. It appears that both aircraft experienced vapor lock while applying full power for take off. The weather has been much warmer in Northern Arizona than usual for this time of year. We believe the fuel, which is in all probability, a winter blend, has too high a vapor pressure, thus causing the vapor lock.
For those of you RV12 drivers using auto fuel at high elevation airports in warm temperatures BEWARE. Both RV12’s will be flown out of Williams tomorrow morning when the temperatures are expected to be in the high 30’s to low 40’s.
Until or when we can determine that the refineries are producing summer blend auto gasoline, we will be changing to 100ll. And may continue with 100ll during the summer months to avoid the possibility of vapor lock at high elevation airports, regardless of the auto fuel blend.
