anyone know why a eurofighter would be constantly circling a light aircraft at 2500ft

[Agaricus bisporus]

The answer is chillingly obvious. It hasn't got a gun and was powerless to do anything except try to frighten it into submission. Useless bloody waste of money.

[P6 Driver]

A good looking girl is flying the ultralight and the Eurofighter pilot is trying to get her number?

Or a good looking MAN is flying the ultralight and the Eurofighter pilot is trying to get HIS number, surely. In this day and age of "equality and diversity" I'm sure the RAF would thank you for some balance...

[sycamore]

A-B, would you like to say that in front of a 27mm Mauser...?

[Agaricus bisporus]

No, I wouldn't. And had I known that after the much publicised anouncements that no gun was to be fitted, then that the gun would be fitted inert as ballast in lieu of concrete at 1/1,000,000th of the cost I hadn't noticed that they'd finally done the sensible thing (and who would have anticipated that?) and quietly decided to go back on all that idiocy and actually comission it after all. oops.
Use a 27mm canon on a microlight? Might work I suppose. Perhaps the pilot was orbiting ro see if there was anything substantial enough to be worth aiming at. Chucking his boots at it might work better...

[SuperF]

or maybe one of his mates was in the ultralight and he was saying hi!

or after radio calls, maybe the ultra light said, ill give you a race...

[Sir George Cayley]

Two things. 1) all this malarky applies to helicopters as well as fixed wing.
2) the rules of engagement permit when authorized the use of lethal force.

SGC