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Wrong fuel tank cap leads to accident

The pilot reported that during the preflight inspection, he filled the Piper J-4A’s forward (main) fuel tank to about 1 inch below the top and noted that the auxiliary fuel tank contained 4 gallons of fuel. The pilot used a stick to “dip” the two fuel tanks and validate the amount of fuel in them. The pilot planned on departing from North Omaha Airport (3NO) in Nebraska for flight operations in the airport’s traffic pattern. Before the takeoff, the fuel selector was positioned for the forward… ( More...

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victorbravo77 10
"The accident occurred 39 days after the inspection, and 2.3 airplane flight hours had accumulated since the inspection."

Why wasn't the incorrect fuel cap (It had a part number of 2501621 etched on it with no manufacturer name displayed -from the article) found during the most-recent annual inspection?
btweston 19
I’m going to go out on a limb here and suggest that maybe the inspection wasn’t as thorough as it could have been.

Great question, though. Hard-hitting.
There are good annual inspections and cheap annual inspections.
Unless you can see the bills, you can't tell which is which.

It would have been a great catch if the mechanic caught this. But does every mechanic look at EVERY PART OF EVERY PLANE?

No, they don't. They might not even have removed the fuel cap unless the pilot told them of a specific concern with it.

It was an expensive lesson for the pilot and their insurance company. Leave it at that.
Jimmy Robinson 10
In reading this, I feel that a multitude of mistakes led up to this accident. The fuel cap itself had two gaskets that were worn and cracked and should have been replaced if not the entire fuel cap. There was no manufacturer or aircraft type stamped or etched on the fuel cap which would not let someone know that it was the incorrect fuel cap. Memorizing part numbers like that is probably not something that a pilot would expect to have to do. And the fuel cap obviously had been there before he did his inspection, at least that's what I got from the article if I read it correctly, so he wouldn't have thought that an incorrect part was on the aircraft. Still, he should have inspected the fuel cap and noticed the worn and cracked gaskets. The mechanic is also responsible for the aircraft which is one reason he shared the blame. It's a shame that a series of mistakes led up to the aircraft crashing like it did. But, it is an important lesson for someone to learn if they read the article. You can't be too careful with an inspection, never too careful. There's nothing wrong with being over cautious and going beyond what's required.
ryan Smith 10
How does a 1940s era GM fuel cap get on a 1940s plane unless it's been there for a long time? Probably long before this owner had it. 2501621 is the GM Patent number for a vented fuel cap from 1947,
Harry Andersen 1
I sure you can find automotive partsI used by the manufacturer on a 1940s plane, and later models too. Of course with a changed part number.
Rick Kennerly 5
Really? Which of us would even know what the proper fuel cap for a 1940 J4 should look like? Near as I can tell, they used & modified all kinds of automotive parts back then. Saw a 40's ercoupe with a car-looking cap with a hole drilled in it for a cork bobber & a wire the other day. Hell, subject cap might have replaced in the 60's sometime.

Not finding the worn cap seals is one thing. Not recognizing the wrong cap on an antique is another entirely. I know this is a minority view today, but any vented cap that fit & sealed back in those days was probably fine.
rbt schaffer 1
I think half the parts on on some old A/C are off old Fords or Tractors... I had early hydraulic brakes on an L-16 and the rebuild part was an auto part and some landing gear'packing' was a plumbers supply product.
g m butcher 4
The wrong fuel cap is not the root cause of the accident. The investigation stopped, as most do, when the immediate suspected cause was identified.
btweston 1
What did your investigation come up with?
Barry Morse 2
2501621 imprinted on the fuel cap is the patent number for the vent design - not a part number.
flyenlo1 2
If the gasket just leaked a bit (more) the tank would have vented
Dennis Fernkes 3
I hope the owners don’t get stuck with the loss.
Larry Toler 2
The cap should have been caught on preflight. On another note,a lot of parts are aftermarket to save money. Even aftermarket parts still have a part number with manufacturers name and certification paperwork. Seems it may have been a counterfeit part from a dubious supplier. To many this may not seem like a big deal, until something like this happens.
rbt schaffer 1
Had an old C182 with the fuel cap AD once... Climbed to altitude and right tank was 1/2... Looked at Rt wing and fuel was streaming off... H.mmm...Switched to Left tank,Landed, gased up and carefully put on cap as per AD... Flew home and had cap AD done by A&P. Expensive lessons
Brian Hood 1
I’m a much less experienced pilot than most of you and just a glider pilot as well, so my question is- from what AGL could that aircraft pull a 180 and land back on the runway or the grass next to it? And do you think the pilot could have done a less damaging accident if he had not been trying to restart the engine? I believe that’s how John Denver died, trying to switch fuel tanks right after takeoff and stalled it. (Along with a string of other very poor decisions).
Dan Boss 4
Well it is specific to each aircraft type, but generally you must have from 600 to 1,000 feet AGL to execute "the impossible turn" back to the runway. Otherwise push the nose over to maintain sufficient speed above stall and land straight ahead or 10 deg right or left of your track. A look at this field in Google Earth and he had plenty of good choices for a forced landing - so it was lack of skill/practice of forced approaches that caused the crash instead of a decent landing.

And I call bullchips on the NTSB saying a blocked vent in the wrong cap caused the engine failure. They do not even go to these small accidents - they either decline to find a probable cause or make one up. But logically if the tank vent were blocked running the engine for under 10 minutes would NOT cause fuel starvation from no tank venting!!!!

C'mon people, gasoline evaporates readily, and the cold fuel going into warmer wing tanks is going to make vapor as the fluid level drops and creates a partial vacuum, thus offsetting the blocked vent condition for some time before enough vacuum is created to overcome the 4-5 feet of head pressure that wing tanks have over the carbureter!

I just did the engineering calcs, and the 60 liter tank filled to 1 inch below, leaves 10 liters of airspace. The head pressure of the wing tank to carburetor is about 150 millibar. So the tank pressure would have to reduce from 1013 mb to 863 mb before the fuel flow to the carb would cease. And by the full throttle fuel flow, this means he needed to be at full throttle for 942 seconds to reach 863 mb, not including the vapor pressure of evaporating fuel in the increasing vacuum. (have you ever left a plastic gas can partially full in the hot sun? What happens - the liquid evaporates to create a lot of extra gaseous pressure and the container bulges with way more than 150 millibars of extra pressure!)

So again I call bullchips on the NTSB finding. The engine died for some other reason, like water in the fuel, or bad magnetos or carb ice, etc.
I'm just a paramotor pilot, but, I've done extensive reading over the past 6 years on all things aviation related. One thing I've learned is 300 feet AGL is WAY too low to EVER attempt a 180° - your focus should be AIRSPEED, and flying straight ahead and wings level. Otherwise you WILL stall and the outcome is likely to be VERY bad. They call the 180° turn the, "Impossible Turn" for a reason. That compulsion has killed countless pilots, some very seasoned.

If I were a pilot, I'd practice an engine-off 180° at 5000' AGL or higher and see how much altitude is lost in that process over MANY attempts, weights, air temperatures, etc., average the worst of them, and then add 25% to that number as the LOWEST I could safely make a 180° to land the opposite direction from where I took off. Otherwise, pitch for best glide and go STRAIGHT ahead. Your odds of survival are much higher just flying straight ahead and landing in a field, gear up if possible. Even landing in trees beats stalling at 50' AGL and plummeting straight into the ground. From the moment that engine quits, let your insurance company worry about the aircraft. Your job is to keep yourself and your passengers, and possible folks on the ground alive.


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