How stunt planes fly

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  • Illustration by Martin Laksman
Date:19 September 2014 Tags:,

A day with a stunt pilot revealed the limits of what stunt planes – and a person – can withstand. By Joshua A Krisch

The cherry-red stunt plane tore off the runway as the tree line blurred beneath us. My life – and the location of my lunch – was entirely in the hands of Jeff Boerboon, the 2010 US National Aerobatic Champion, who sat at the controls. It was practice day at the Bethpage Airshow in New York, and we were strapped into the cockpit of his two-passenger Extra 300L – an aerobatic aircraft that can reach speeds of 407 km/h. Boerboon asked if I was ready, then, before I could respond, yanked the stick to one side. Here are some of the stunts we tried that nearly killed me.

Loop
What it is: Vertical loop at 290 km/h

How it works: We were pulling close to 4 g’s at the top of the loop, which would have put serious strain on a lesser plane’s structure (a 747 could break under similar stress). But the Extra is reinforced with steel tubes and carbon fibre, so its frame can easily handle up to 10 g’s.

How it feels: The climb jammed me into the seat. Suddenly, the sky was down, the sea was up, and g-forces were crushing my chest. I may have screamed into my headset.

Aileron roll
What it is: A tight roll around the horizontal axis.

How it works: Aeroplanes stay up because of “lift,” the difference between airflow above and below the wings. A regular plane would drop like a rock if it inverted. But the Extra’s wings are symmetrical. When the plane does a knifeedge (wings vertical), the rudder – a movable fin on the tail – acts like a small, sideways wing.

How it feels: It took only a light tap of the Extra’s stick to flip us. One roll wasn’t so bad. A series of them gave me sickening vertigo.

Vertical spin
What it is: Straight up until you nearly stall, before spinning back towards the earth.

How it works: A standard aeroplane has precise control surfaces, such as the horizontal stabilisers on its tail. Executing a spin demands instability, however, so the Extra has an oversize rudder and elevators so pilots can get into and out of spins.

How it feels: Spins are sluggish manoeuvres – the power is at idle, and you’re falling at a fairly constant speed. I was acutely aware of how little Boerboon was doing to manipulate the plane.

Hammerhead turn
What it is: A climb with a cartwheel turn at the peak. How it works: Rockets can lift off because their thrust is greater than their weight. The thrust-to-weight ratio in a Boeing 757 is only 0,33, but the Extra 300L boasts a higher ratio, 0,55. That means the stunt plane can accelerate rapidly and has a high climb rate.

How it feels: The same formidable g-forces as the loop, but at the top you get a gut-churning wing-over-wing spin. My teeth are still clenched from the ride.

Watch Joshua’s gut-churning stunt plane ride…

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