@Peter, do you know where can I find 2 filler caps for a Socata TB20, eventually with a key lock?
I have replaced the outer o rings, however I still don’t like the feed back I get when rotating them, it’s like one can keep turning, with no ‘click’ or lock sound to know they’ve reached the end and the tanks are securely sealed…
Apart from Socata, no idea, though I believe they are standard parts. Look for markings on the bottom.
The adjustment of the central bolt needs to be done just right.
The pre-GT ones are different from the GT ones.
I found two surplus stock on eBay when I hadn’t the TB20 they were about half the price of factory new. You do have to pay some duty if they are from the USA. Check eBay
The fuel cap model is Shaw Aero 416-50, and it seems it is widely used on many aircraft models.
Prices are around $400 per piece.
Does anyone know if a compatible key lock variant that can be installed exists out there?
Has anyone a source for lockable fuel caps?
Specifically a C182. Most of the ones I’ve found are for motorbikes or, interestingly, a RV6.
In a country where a tankful is equivalent to an individual’s annual income, they’re useful.
“In a country where a tankful is equivalent to an individual’s annual income, they’re useful.”
I once had my car, parked outside overnight, damaged to get to the petrol. It would have been better not to have a secure cap.
Thinks: for an annual income in a few minutes, I might be tempted to pierce the wing underside to get the fuel drained.
Surely you can drain the whole tank via the water drain(s).
I did that once – after returning from a flight on which suspected water-contaminated fuel was taken on and during which we had some fun. IIRC, about 30 USG was drained out, in an hour or so, into a collection of jerrycans which I gave away and which I am pretty sure were used to refuel a certain PA28 
Draining fuel from the filler cap is allegedly, reportedly, the popular procedure at “farm strips” and needs a low wing plane to be parked alongside a high wing “donor”, and the fuel is siphoned out with a hose. Low wing planes are probably drained via the water drains.
The main plus of lockable filler caps is that it stops somebody putting stuff into the fuel. One pilot reported this having been done in Turkey (into a PA46 I believe).
In 2010 I also asked for lockable fuel caps for my Cessna 182, but there was none.
If someone will work for 330L of Avgas for a year, and there are 261 working days in a year. I’d happily pay them $5 a day to make sure nobody took anything.
If you have to worry about fuel being nicked you maybe shouldn’t park there. I’ve had people cut a hole in the wing of my Cub parked on a lakeshore, steal my stuff and push the aircraft adrift.
WilliamF wrote:
I’ve had people cut a hole in the wing of my Cub parked on a lakeshore, steal my stuff and push the aircraft adrift.
Where was that ?
