This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
I departed the airport in a Cessna 172 with a student working on his instructor rating. Shortly after takeoff we smelled raw fuel fumes and returned for a landing.
The scent of the fumes got stronger in our descent.
The student asked me to land. On the ground he told me he got a migraine headache from the fumes. It appeared he was incapacitated from the fumes. If he was by himself this could have been deadly.
The plane was withdrawn from service and the fuel tank sent to a welding shop. Apparently the filler tube developed a crack where it is welded to the gas tank.
We were lucky that there was no fire or explosion.
This was the second time this year that this fuel tank leaked. About eight or nine months ago I refused to fly the plane after smelling fumes on another training/demonstration flight.
The plane continued to be operated by other instructors and students, despite my emailed warnings to them, until it was pulled from service for its 100-hour inspection. The fuel tank was apparently sent to a welding shop for repair.
I spoke with an aircraft inspector who works for a different school and was told that this was a common problem in their Cessna aircraft. This inspector believes the problem is caused by the fuelers letting the fuel nozzle apply too much force on the filler neck.
Our inspector/director of maintenance thinks it is caused by the fuel tank walls or top flexing, and causing stress cracks where the nozzle is welded.
Person A at Company confirmed that a lot of Cessna fuel tanks have cracks where the filler neck joins the top of the tank. They seem to think it is from the fuelers letting the nozzles put too much pressure on the filler necks. However, they said the top of the tanks also develop cracks.
The Cessna leaking fuel tanks appear to be a systemic problem and it is inconceivable that the FAA is unaware of the problem and obscene that there have been no ADs issued to warn pilots to have mandatory fuel tank inspections and ground the aircraft anytime there is the smell of fuel in the cockpit or fuel stains behind the filler caps or under the wing above the door.
Some operators have taken the step of not filling the fuel tanks to the top. However, in a descent, there will be fuel behind and consequently above the filler neck to create a pressure head to drive fuel through the crack in the neck weld. Partially filling a tank with a known leak should be considered operating an aircraft in a reckless manner and consequent violation of FAR 91.13.
Primary Problem: Aircraft
ACN: 1994807
Old planes wear out. Fix stuff. Cessna 182’s have fuel bladders that eventually wear out, just like the metal tanks of their smaller cousins. Fuel odors in the cockpit from the few drops remaining in the fuel tester won’t even be noticeable after 4-5 minutes… if then. If we can smell the fuel we have a safety issue (the plane isn’t safe to fly); If we smell fuel the aircraft is noncompliant with its type certificate and we have an airworthiness issue. In either case, regardless if the aircraft is part of a fleet or its a personal only, fuel odors ground the aircraft.
We just had the same issue with our 1980 172 with 2,600 hrs. Fuel fumes, took it to our mechanic and he discovered a crack at the filler neck. Probably caused by pressure from the fuel nozzle. Perhaps a service bulletin from Cessna?
Sounds as if lots of pilots don’t know a Phillips from an open end
Poor fueling procedures by Line Technicians or plane owner resting the fuel nozzle on the filler neck, against the filler neck.
“The Cessna leaking fuel tanks appear to be a systemic problem and it is inconceivable that the FAA is unaware of the problem and obscene that there have been no ADs issued to warn pilots to have mandatory fuel tank inspections and ground the aircraft anytime there is the smell of fuel in the cockpit or fuel stains behind the filler caps or under the wing above the door.”
Fuel tank filler neck “assemblies” that are routinely abused by poorly-trained personnel using improper refueling techniques are going to leak eventually. As Mr. Patterson indicated: It shouldn’t take an AD to direct people to use common sense if something doesn’t look right, feel right, or SMELL right.
No: If other instructors, students, mx personnel, and management (Chief CFI?) continue to fly after these issues have been documented…the real problem is the Safety Culture at that flight school.
If you are CONCERNED about this issue; my advice is to use SELF-SERVE pumps and do the refueling yourself WITHOUT LETTING THE NOZZLE HANG its weight on the filler neck.
Another common issue that can cause fuel smell in the cockpit of older 172’s is deteriorated rubber fuel line coupling hoses for the cross-feed vent line just above the windshield. Just a few inches of forward headliner must be pulled back to replace hoses. BUT, before you dot his; make darned sure the smell is not coming from residue from your Fuel Tester or Sample Cup.
AV-gasoline or Auto-gasoline[STC]??? Regardless… the fire/explosion potential should raise the hair on Your neck if You get a persistent ‘smell’ of raw gasoline around or in any aircraft.
AV-gas 100LL is still tinted blue for leak detection… as all aviation gasoline fuels have been for decades. The tinting is explicitly intended for leak detection and tracking-back to the ‘source’.
Auto-gas is likely to be ‘clear’. IF SO, then tracing leaks is far more difficult… unless gasoline ‘puddling’ and/or paint-damage occurs.
OH YEAH… raw gasoline is a solvent which can ultimately damage primer and paint finishes.
Actually the tinting was/is for specific octane and type detection, not leak detection.
Stupid is as stupid does. No AD needed!
Yet another cost-gutted item featured in a quarter-$million flying coffin. Ranks right up there with collapsing nose wheels upon hard landings. These kinds of pitifully irresponsible inadequate / dangerous engineering parts designs pre-date the Ford Model-T. Pathetic is the only adjective that fits.
Regards/J
It is indicative that “The plane continued to be operated by other instructors”, that not every instructor was unable to deal with the situation. Thousands of Cessnas are flown every day without having to deal with fumes. Fix the problem on that specific aircraft. AD’s are for problems with the fleet.
I had a leaking 172 35 years ago, but didn’t need an AD to tell me the blue stains on the back of the wing and on the rear side window was from leaking fuel. This has been a nonevent for thousands over the decades.
Please, if there is a safety issue such as this contact the manufacturer (Cessna) to see if there is a published remedy. Don’t assume that everyone knows about it and has done nothing. Safety relies on feedback.
This ASRS is a non sense in the part it implies that FAA should be emitting an AD for the leaking (I supposed of fuel – the text isn’t clear) of the thousands of 172 that everyday fly. If flumes are detected, the remedy is to send immediately the a/c to the repair shop to find out what’s happening.