I'm thinking this question had to been asked before, but I did a search and couldn't find anything on it. It's really bugging me, because I never could find out the right answer.

Suppose you have a jet airplane sitting on a runway. But this runway acts like a treadmill. The jet starts it's thrusters and for every mile an hour the Jet's wheels move forward, the treadmill moves a mile an hour in the opposite direction.

Will this jet eventually take off? Thanks.

Rob

Old_Fart

No.

It's all about relative wind. If there is no wind flowing over the wings, there is no lift.

That's why carrier based aircraft do so well. First they generally have a good headwind and then they have the speed of the carrier added to this. They could be doing 60 knots before they even release brakes.

lobrobster

Thanks Old_Fart, but...

We're talking about a jet which uses thrust. Theoretically, wouldn't the thrust propel the plane foward (even though the treadmill is moving in the opposite direction), and eventually take off?

CaptainRich

We're talking about how the plane gets up into the air. Not how it's propelled.
**edit** Forces on an Airplane

NeedKarma

There was a very long thread here about that exact same subject a while ago. I'll try to dig it up.

NeedKarma

Opps I was wrong, the convo was on Digg. Plenty of discussion about this topic everywhere: plane treadmill take off - Google Search

MarkRealEstateConsultant

as a pilot - the answer is no. Simple physics - there is no air passing under the wing to provide lift

lobrobster

Thanks NeedKarma! That's what I was looking for! We had a HUGE debate at work about this awhile back that lasted for almost a month. I didn't know this was such a popular question.

CaptainRich

On second thought, the tires would spin very fast but if the thrust was sufficiant to move the craft against the still air, who cares how fast the tires have to turn?

ebaines

Since there's no air flow over the wings, they are essentially useless in this scenario. So they may as well not be there. Now the question may be easier to comprehend - would a plane fuselage with jet engines but no wings ever lift off? Obvously not (unless it's a Harrier or some other VTOL design).