I was down at the local field airfield over the weekend listening to ATC (Tip: An excellent way to tune your ear to ATC lingo and speed is to listen using a cheap airband receiver), when I heard an exchange between a pilot and the tower.
The pilot was obviously an elderly gentleman who had flown in earlier on during the day. He was a little unsure about the airfield and started asking directions for taxiing out to the runway for a departure.
ATC were very obliging and steered him in the right direction. However as he was doing his run-up/engine check he obviously noted a problem and asked for time to investigate.
Once again tower duly obliged and he taxied away to a disused bit of tarmac to fiddle with whatever needed to be fiddled with. I could see the plane from my vantage point and noted it was a Piper Cub type aircraft (Tandem seating, cloth covered, fairly old and basic), and that it was painted in a lurid green livery.
After about fifteen minutes he came back on the radio, asked for permission to taxi, got back to the holding point, did his run-up and requested clearance. This was duly given and he started his takeoff run.
About 50 feet off the ground he came back on the radio asking for permission to switch frequency to the nearest LARS service with the following exchange
"Bxxxx Tower, this is Golf - Alpha Alpha requesting permission to change to Fxxx on 125 decimal".. there was a slight pause "Oh no, my engine's playing up again. I'm going to have to land immediately"
Tower gave him permission to land and - with his engine audibly misfiring even from my vantage point at the far end of the airfield - he executed a swift 180 in the air and landed back on the runway he had vacated only moments before - in the opposite direction!
I reckon the time from wheels up to wheels down was no more than about 20 seconds.
Now if you're going to make an emergency landing, that's the way to do it!