----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Hi gang,
I got the following email from John Rogers. He's right. I meant to say 0.4 psi. The exhaust port of a shop vac does a fine job in supplying this.
Syd
Although I do not normally get involved in the discussions of this forum, I feel that I must comment on applying 4 psi of air pressure to check a fuel tank. If that much pressure is applied to an Ercoupe fuselage fuel tank, it will end up looking like a distorted globe of the world with its its tectonic plates separated. CAR 4a, paragraph 608 (under which the 415C was built) states “Fuel tanks shall be capable of withstanding an internal test pressure of 3 ½ pounds per square inch without failure or leakage”. I am of the opinion that test was accomplished in a containment cage to prevent distortion of the tank. I have seen A&P mechanics attempt this test to that psi while a tank was still installed in the wing of a Cessna 182. The results were a wing that was shaped like a swollen sore thumb – unsalvageable! I have further demonstrated this test several times with all types of tanks in the A&P classroom to put across my point. The results were always the same. The tank ended up looking somewhat like a football. In fact, a 55 gallon drum will not withstand this test without distortion. The proper leak test procedure can be found in AC 65-9, Chapter 4, page 96. That reference states “ When performing a pressure check, ¼ to ½ psi air pressure is adequate. The previous paragraph states that not over ½ psi should be used on welded tanks.
Sincerely
John W. Rogers
A&P #1401399 IA
owner of Ercoupes N611P and N94355
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