A C172G/U with tanks full of warm fuel lost power because of a vapor lock at 8;500 feet but was able...

Narrative:

I did not follow the placard instructions to switch to single tank operation above 5;000 feet; installed on my C172G per ad 72-07-02. The aircraft was full of warm fuel from a desert airport and had been out in the sun. We were cruising lean at 8;500 feet indicating 105 or so mph. We were 8;000 AGL or so. The engine slowly lost power; sagging and partway recovering on a 10 second period; before losing all power. Carb heat (sustained); mags; mixture (both ways) had no positive effect. We were well within range of mit and headed there. We switched tanks around rapidly; to no effect. We then stuck on right tank for a while; and later switched to left; and the engine then regained power around 6;000 MSL. Subsequently the engine ran on either tank. We landed anyway. All engine sumps were ok; etc. And we determined that the problem was not following the placard. We then flew home 2.5 hours.what seems odd to me is that we unknowingly restarted the engine using a procedure found in the 1964 poh; but not in the 1966 poh. It would have been helpful if the procedure appeared in the 1966 poh that I have for my plane. People flying this plane above high ground really should know about this procedure. There are rumors out there that this placard is nonsense that 'got the FAA off cessna's back' about some unexplained engine failures; which is misleading.

Original NASA ASRS Text

Title: A C172G/U with tanks full of warm fuel lost power because of a vapor lock at 8;500 feet but was able to regain power by switching fuel tanks as per a 1964 POH procedure which is not published in some later POHs.

Narrative: I did not follow the placard instructions to switch to single tank operation above 5;000 feet; installed on my C172G per AD 72-07-02. The aircraft was full of warm fuel from a desert airport and had been out in the sun. We were cruising lean at 8;500 feet indicating 105 or so MPH. We were 8;000 AGL or so. The engine slowly lost power; sagging and partway recovering on a 10 second period; before losing all power. Carb heat (sustained); mags; mixture (both ways) had no positive effect. We were well within range of MIT and headed there. We switched tanks around rapidly; to no effect. We then stuck on right tank for a while; and later switched to left; and the engine then regained power around 6;000 MSL. Subsequently the engine ran on either tank. We landed anyway. All engine sumps were OK; etc. and we determined that the problem was not following the placard. We then flew home 2.5 hours.What seems odd to me is that we unknowingly restarted the engine using a procedure found in the 1964 POH; but not in the 1966 POH. It would have been helpful if the procedure appeared in the 1966 POH that I have for my plane. People flying this plane above high ground really should know about this procedure. There are rumors out there that this placard is nonsense that 'got the FAA off Cessna's back' about some unexplained engine failures; which is misleading.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1166605
Time
Date	201404
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	None
Component
Aircraft Component	Fuel Distribution System
Person 1
Function	Pilot Flying
Qualification	Flight Crew Private
Experience	Flight Crew Last 90 Days 20 Flight Crew Total 270 Flight Crew Type 240
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

A C172G/U with tanks full of warm fuel lost power because of a vapor lock at 8;500 feet but was able to regain power by switching fuel tanks as per a 1964 poh procedure which is not published in some later pohs.