Can a Jumbo loop the loop?

The question arose out of the blue and for no discernible reason: Can a Jumbo jet loop the loop?
For the benefit of those who aren’t flyers or don’t drive Johannesburg taxis and therefore might not know what looping-the-loop is, let me explain.
Looping the loop describes how an aircraft suddenly climbs steeply and performs a backward somersault before diving and resuming level flight.
The question was picked up from the Internet by a friend who was for years involved in space flight and aviation. He says it was originally posed to Cecil Adams who runs a questions and answers website called The Straight Dope.
The full question was: “Is it possible to roll or loop a 747 or DC-10 (airliner) loaded or empty?”
Adams replied, “No one has ever tried to get fancy with one of the Big Birds, but there once was a Boeing test pilot who, in a moment of frivolity, took it into his head to execute a barrel roll in a (Boeing) 707.”
The consensus at Boeing’s factory, says Adams, was that a 747 would probably survive a barrel roll but to try it would be, and he quotes, “an extremely foolish action.”
A barrel roll is when the aircraft rolls over on its back and continues the roll through 360 degrees, spiralling along a horizontal path hopefully through the air.
The problem, says Adams, is not so much with the strength of the wings, which are designed to stand much greater pressures. It has to do with the skill of the pilot.
“Enough forward speed must be maintained during the roll to compensate for the loss of lift that occurs when, in effect, the wings cease to function. That happens when the wings are in the vertical position and can no longer hold the plane up.
“In a small plane, the problem is minimal: the wings spin out of the vertical position in a split second. But in a larger plane it takes longer to roll and the margin for error is increased, and the fatal moment could be stretched out enough to pull the plane down.
“Looping a 747 or a DC-10 would be trickier still.”
I sent the comments to Geoff Quick, an ex Royal Air Force pilot who is a fellow member of the RAF Officers’ Club in Johannesburg.
Geoff is originally from Cornwall where, he says, people still point excitedly at the sky when aeroplanes pass overhead.
Geoff has seen both the Trident (a De Haviland airliner) and the F28 airliner (some versions carried 85 passengers) barrel rolled at the Farnborough Air Show in Britain. And he says the VC10 – a serious four-engined jet airliner in the 1960s – has looped-the-loop .
“Most business jets have barrel rolled from time to time. Executed properly the manoeu
vre puts little stress on an airframe or its occupants,” says Geoff. “Most aircraft, including many helicopters, can theoretically do it.”
I was shown a U-Tube video of a pilot balancing a cup of coffee on top of the instrument panel where it remains steady while the plane rolled through 360 degrees. Then he poured a cup during another roll and spilled not a drop.
Trick photography? No says Karl Jensen, perhaps South Africa’s best-known airline pilot (now retired). Karl knows the fellow who did it.
It’s all very sad. There’s just no respect for the law these days – not even the law of gravity.

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