Test flying a prototype light single with about 20 hours on the airframe, just joined the circuit on a wide left base, No.5 in a very congested circuit. I was in the right hand seat, Wyvern (not seen him around Pprune for a while) in the left.
Sudden loud thumping from just in front of our feet, very brief cockpit conversation:
Wyvern: What's that?
Genghis: Don't know, might it be the engine?
Wyvern: Certainly might be!
Whereupon Wyvern called a very calm mayday, possible engine problem, and requested priority for an immediate landing.
We were given that and the next bit was visually quite comical - without being asked, the four aeroplanes in front of us went left-right-left-right as they all initiated their own go-arounds.
We landed safely, taxied back in, to find to our relief that a non-critical bungee in the undercarriage had failed and decided to play a drum beat on the underside of the cockpit.
We removed the bungee, went over to the tower to thank them, and explained (with props) that "the elastic band had snapped".
G