Here's my offering.
Last summer I flew the Rallye down to Goodwood for a long weekend. On the Friday I decided to have a trip round the Isle of Wight then across to Compton Abbas. The outbound trip went fine, and although there was a very strong wind blowing down the runway at Compton Abbas, the landing was OK. So far, so good.
I topped up with fuel. On the Rallye, the fuel tank is accessed via a rubber bung which is held in place by a detachable cover with lugs that slide under the wing skin and is locked in place with a spring loaded screw T-bar. I checked that everything was firmly in place, did my power checks and took off.
On my way back to Goodwood I wanted to fly over the farm where I was brought up, which was about 10 miles to the north east of Compton Abbas, just outside the western stub of the Boscombe Down MATZ. I had done a couple of orbits and was heading off towards Romsey when I happened to look across at the port wing. Something was streaming back across the wing. 100LL!!
The spring catch had come undone on the fuel cap cover. Fortunately the cover was still in place holding the bung in, but the lower pressure over the top of the wing was sucking fuel out at a rapid rate. I decided that the best option was to return to Compton Abbas, which was only a few minutes away, and by flying with the starboard wing low the fuel loss dwindled to a trickle and then stopped. This was just as well, because the Rallye has a cross feed between the tanks.
I had visions of the cover and bung departing company with the aircraft and landing somewhere in deepest Dorset and leaving me with a u/s aircraft, but thankfully they stayed in place. I called up Compton Abbas and told them I had a problem and was returning, rejoined the circuit and landed without further ado.
They had just received a fuel delivery, so I had time to recover from my ordeal before I refuelled again. The nett fuel loss was about 19 litres, getting on for half a tank full (which included about 20 minutes flying time). This time I cadged some gaffer tape from the engineers in the hangar, and taped up both covers to stop a repeat performance. The second attempt to return to Goodwood went off without further incident, although I was visually checking the covers every couple of minutes.
I can only think that I hit a bump the first time I took off, which was enough to spring the T-bar open. From then on, the covers were thoroughly checked for security before each flight and we never had the problem recur. Just once was enough. Fortunately it hadn't happened somewhere like mid channel. An incident like that certainly focusses the mind.
At the end of the year the Rallye went off to a new life in Ireland. We've got an AA5 now.