Vapor Lock at FL82

[constantin_w]

Hi guys,

today I went to FL82 for a while and had to drop to somewhere about FL65. As soon as the descent started, the fuel pressure sensor started screaming and showing high numbers and the engine started running rough. Originally I felt the oil may be the root cause as the oil temp didn't rise above 70°C but after descending a bit the problem disappeared immediately. In the end, I think I experienced vapor lock (as I know the symptoms from the summer time near the ground). I own a 2013 RV12 with the 912 ULS engine and I use Mogas .
I am a bit surprised that FL82 does already trigger vapor lock. Did anyone of you experience similar issues at that altitude?

BR
Constantin

 

[Avanza]

Hi guys,

today I went to FL82 for a while and had to drop to somewhere about FL65. As soon as the descent started, the fuel pressure sensor started screaming and showing high numbers and the engine started running rough. Originally I felt the oil may be the root cause as the oil temp didn't rise above 70°C but after descending a bit the problem disappeared immediately. In the end, I think I experienced vapor lock (as I know the symptoms from the summer time near the ground). I own a 2013 RV12 with the 912 ULS engine and I use Mogas .
I am a bit surprised that FL82 does already trigger vapor lock. Did anyone of you experience similar issues at that altitude?

BR
Constantin

It normal to see reduced fuel pressure during a climb at that altitude if fuel is varm at take of. This can trigger vapour lock.
Rising fuel pressure during a decent is not related to vapor lock.
Rather it is more likley the carb had problem to adjust the fuel level due to
quick power reduction.

Good luck

 

[Rick_A]

FL82 ?.?? Just nit picking but I thought that “FL” altitudes started at 18,000 ft, FL180

 

[egp8111]

Flight levels start at 18000 in the US. In Europe and other countries they can start at much lower altitudes.

 

[constantin_w]

Flight levels start here with the transition altitude which is generally at or near 5000ft.

 

[Richard Connell]

TA is 10,000 here

 

[Southern Pete]

I would say the Mogas is the culprit. The vapour pressure of the Mogas is much lower than Avgas meaning that as the aircraft climbs the pressure differential keeping the fuel liquid drops, usually not a problem with Avgas but with Mogas who knows?