fuel vents and loss of power

My Alon has flown flawlessly since I removed the cover to the header tank fuel gauge and opened the vent hole. I saw in the December Coupe Capers page 8 that a bug plugged the vent hole 10 years ago causing the same problem. From S/N 4000 through M-10's have the same single vent that can cause engine failure. The open wire fuel gauge provides a second source of air to keep the engine running. Great insurance.

It has flown perfectly since. It climbs at 2380 RPM at 700-800 FPM at 1000 density altitude, and 600 at 3000 feet. The local mechanic did an annual and signed it off still blocked. Our lives are in our hands. Be sure your plane is right. Lynn Nelson provided priceless info.

So Henry, you don't tell us if that solved the problem and you've had no more failures.

The current Coupe Capers recorded an incident where an Alon Aircoupe lost power in flight. Upon further discussion with Ron, we concluded that his header tank vent was plugged. I bought an Alon in January and had some good flights on. The weather proof cover on the header tank was broken. I replaced it. The next flight the engine quit at 200 feet on take off. Pumping the throttle made no difference. I was out of runway with a plowed field ahead with standing water after a 5 inch rain. I dumped the nose 30 degrees and rolled into a 45 degree bank and was able to turn 90 degrees to the runway. I rolled wings level and round out for a soft touchdown. It was a hay field with standing water, causing damage to the nose wheel. The mechanic found brown stuff in the carb, but the next flight also resulted in a momentary loss of power. We put on a rebuilt MS 5082, but it also lost power in flight. The mechanic had no answers. I thought what was the difference between when it flew right and loss of power. Every flight with the good cover experienced loss of power. I took a closer look at the header tank fuel cap. Someone had plugged the vent with a piece of aluminum tubing. No air could get through it. When I put the good weather proof top on, the tanks were sealed with no way to vent. The vacuum shut off fuel to the carb. We drilled out the plug in the header cap horizontally and vertically and now it vents. I also removed the weather proof top to get a second source of air in case the main vent gets plugged. I am too old to trust my life to one vent. My plane is hangered, so I am not concerned about rain getting in past the wire. S/N 4000 and up have unvented wing tank caps, with the header cap as the only vent. I suggest that if you have the late models, remove the weather proof cover if you keep your plane in a hanger, or add checking the vent if it is kept out in the rain.