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Who, what, why: How easy is it to push a plane? Who, what, why: How easy is it to push a plane?
(about 2 hours later)
The story of passengers pushing a frozen Siberian plane soon went viral. But was it really possible, asks Tom de Castella.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."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 video of the incident appears to confirm their version. 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. 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.""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 general 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 applies to a 30-tonne plane. You would need about 90 people or, as in this case, about 50 strong men. "You are just trying to overcome the rolling resistance of the tyres," says Andrews. 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 is true if the wheels turn. But the problem with the Siberian plane was unlocking wheels 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. 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.
The physics relates to something called moments (force x perpendicular distance). It turns out that the passengers - whether they knew it or not - did just the right thing by pushing the wings. 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 the same probably wouldn't work with a bigger plane. The wings of a Boeing 747 or Airbus would be higher and probably out of reach, 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.
There's always pulling. A plane pull for charity takes place every year at Bournemouth Airport where teams of 20 pull a 35-tonne Boeing 737 a distance of 50m as fast as they can. And then there are the fitness fanatics - in 1990 a Malaysian man pulled a 737 with his ponytail. However, they were not dealing with locked wheels in Siberian temperatures. 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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