MOST people wait until the aeroplane is on the ground before leaving it.

Sergeant Phil Collett is inclined to make his exit at around 12,000feet and then hurtle earthwards at upwards of 120 miles an hour.

And if you are up there with him and he tells you to jump, he expects you to jump, no questions asked.

Phil (39) is a parachute instructor in the RAF, a veteran of 3,500 jumps, and is based at Boscombe Down, near Amesbury.

Such is his enthusiasm for skydiving that he is qualified as a civilian instructor with the British Parachute Association, as well as with the military instructor.

He is also an advance instructor and can train people on the Accelerated Freefall course.

Phil joined the services in 1986 as a physical training instructor.

Within two months of starting training, he found himself at RAF Brize Norton for two weeks where he did four static line jumps, two from planes and two from balloons.

No matter how many jumps you make, he says, you always remember the first one although perhaps you would rather not.

"You jump out of cage under a balloon which has been wound up to 800 feet.

"It was a complete blur, absolutely horrific," he says.

Six months parachute training followed in 1991.

He moved on to freefall parachuting, and then qualified as an instructor.

Now he is one of around 400 men in the physical education branch of the RAF, of whom about 50 per cent are parachute-jump trained.

At Boscombe, he is one of a team of four sergeants, one flight sergeant and two officers, who work in conjunction with the civilian staff at QinetiQ.

Much of his work is spent training others or putting parachuting systems on trial on behalf of the armed forces.

At least three months of the year are spent overseas he has just returned from a month in Arizona because the weather conditions abroad make it a more cost effective option.

"We work a 12-hour day on detachment and make three jumps a day," he says.

Phil is keen to emphasise the safety element in trialling parachutes.

Apart from tests by the manufacturers, he says, parachute systems are put through a series of gantry tests and dummy drops before they go anywhere near a person.

Is it worrying to be the "test driver" for something as crucial as a parachute?

"The fear factor completely goes and you just concentrate on what you've got to do," he says.

"You're always aware that something could go wrong although there is a consolidated ground phase and briefing before jumping to eliminate risk. Anything considered greater than low risk wouldn't have got any further."

With so much adrenaline involved in his job, you would think that a relaxing hobby was in order.

"I jump at the weekends for fun," says Phil.

He is a member of a formation squad that takes part in the Army Four-Way in August, above Netheravon, competing against 30 teams from all the armed forces, and also does charity tandem jumps.

"It's addictive," he says, "and it's a really good job.