Who, what, why: How easy is it to push a plane?
The story of passengers pushing a frozen Siberian plane soon went viral. But was it really possible, asks Tom de Castella.
"Siberians are so tough that for them pushing a frozen plane along a runway is a piece of cake," the Russian daily newspaper Komsomolskaya Pravda reported. The 30 tonne UTair Tupolev 134 refused to move, reportedly because the wrong grease had been applied, leaving the brake pads frozen in the minus 52C temperature.
Some of the passengers sprang into action, allegedly pushing the plane backwards until its wheels were able to turn and a tow truck could take over.
A passenger was quoted as saying that they had been asked to help, and had pushed it "about 5m, maybe more". But the local authorities have cast doubt on the story.
"Naturally, the plane was moved by the truck, because people physically could not do it," the West Siberian transport prosecutor's aide Oksana Gorbunova said. "It looks like a joke."
In theory it's not very hard to push a plane, says Dr John Andrews, visiting fellow in physics at the University of Bristol. A one-tonne car can be pushed by three people. The same principle should apply to a 30-tonne plane. You would need about 90 people or, as in this case, about 50 strong men, Andrews suggests. "You are just trying to overcome the rolling resistance of the tyres."
That may be true in theory. But in practice, it is very hard to find anywhere on a plane to push, says Chris Shepherd, teacher support manager at the Institute of Physics. The wings are not a good place to push as they are too high to get much force behind, he says.
And in the case of the Siberian plane, there was an additional problem in that the wheels were stuck with frozen grease. Here you have to overcome not only the rolling resistance but the frictional resistance of the ball bearings due to the fact the grease had solidified, Andrews says.
In terms of freeing up the wheels, Andrews says pushing the wings could help. Because there was a large distance between the wings and the wheels it gave the people pushing greater leverage. "It's the principle of the spanner - the longer the spanner the less force you have to apply in order to shift the nut," Andrews says. Once the wheels unlocked, the friction would have melted the grease. Then the tow truck took over. So the passengers' version is feasible, he says.
But for Shepherd, it remains very unlikely that there's any explanation that allows for the people making a significant contribution to moving the plane. He thinks the spanner analogy is not relevant here as the whole plane was not rotating - it was moving laterally. In the Siberian case, he says it seems likely that the plane moved because of the tow truck. Many planes can also use reverse thrust.
Getting the passengers out and therefore lightening the plane would have helped. And they may have applied some force, but it would have been marginal, Shepherd argues. "One of the guys is pushing with one hand. They're not really putting their backs into it."
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