3 Responses to “Model Plane”

1. Tom M
   October 9th, 2010 @ 11:47 pm

   Actually this should be possible to scale down to test – model planes and a conveyor – is anyone from Mythbusters listening?

   Update – it appears so – the Mythbusters forum has several threads on this subject already – all reaching the conclusion that the plane can take off.

2. Tom Keliher
   December 29th, 2010 @ 6:10 pm

   Hi Mike, I was just looking at Hobby People's website and Black Horse model airplanes. Then I followed the link to BH's webpage, hosted by HP. Then I did a google search for Black Horse Models and a place called American Pioneer Hobbies is at the top of the list and they claim they are the exclusive distributors of Black Horse model planes. So does Hobby People. What gives? Something is not quite right about this. Maybe you want to ckeck into this outfit?

3. mbs
   March 9th, 2011 @ 6:38 pm

   The Mythbusters are wrong and right because there are three ideas in this myth that need to be resolved.
   Strictly speaking a plane, a car with wings, a cheetah with an ultralight wing attached to its back CAN take off from a moving treadmill – so the Mythbusters are right a plane CAN take off from a treadmill. The explanation was wrong however — There are two related issues and one unrelated issue…

   1. Friction. The “free spinning” wheels of the model or any plane are not really frictionless. In the show Adam is seen holding the model plane on the treadmill and there is even a block of wood at the end of the treadmill holding the plane from being pushed off the treadmill. The propeller is not on and the plane is moving backward from the force of the treadmill pushing against the friction of the wheels (two kinds, bearings and wheel against the surface of the treadmill). If the wheels where truly frictionless then setting the plane down on a moving treadmill would have no effect (other that perfect free spinning wheels) and the plane would remain stationary, no need to hold it or put a wood block at the end. A hovercraft over a treadmill would not move backward since there is no (except a small amount of air friction) friction between it and the surface of the treadmill. The force being imparted by Adam holding the plane or the wood block holding the plane is offsetting the opposing force from the treadmill acting on the friction of the wheels.

   Now, if the plane imparted its OWN force (through the engine and propeller) to EXACTLY offset the same force (remember both equal and opposite force) being imparted by the treadmill, then Adam could let go and the plane would remain STATIONARY. In the show the planes engine and propeller easily overcame the friction force, continued forward after offsetting this force and reached enough air speed over the wings to provide lift and the plane took off. This would work for a car with a wing on it. If a treadmill could only go 11 miles per hour in one direction and the engine in your car could only achieve 11 miles per hour forward then the car would not move (relative to the ground and air). But since the car could achieve a speed of say 110 miles per hour and it only needed 99 miles per hour of airspeed over the wings to take off, then it would be able to take off as well.

   2. This leads to the second part of this problem. All that is required is enough force to overcome the friction in the wheels (and the friction of air resistance) to impart enough speed forward to create the airspeed over the wings to create the lift required to lift the plane. An exaggerated example: What if the treadmill was infinity long and instead of a hard rubber surface it had a mud trough 6 inches deep. The plane with its “free spinning wheels” would now have much greater friction to overcome. However, given enough power in the engine the plane could gain enough speed to overcome the friction of driving through 6 inches of mud moving in the opposite direction and still take off. If the plane could only muster enough forward thrust to EXACTLY offset the friction of the mud pulling it in the opposite direction, then the plane would remain stationary again. The point is that AIRSPEED over the WING is the deciding factor in whether or not the plane will lift off the ground not speed relative to the treadmill.

   3. This raises the final question. Does the planes own engine provide enough wind speed over the wings of the plane to make it lift off (very much like a helicopter) the ground without any forward movement. That would depend on the engine, the plane and the location of the thrust produced by those engines. A plane can certainly lift off the ground from a gust of wind, the wind creates the lift and the plane lifts off the ground. This is not strictly speaking “taking off” and achieving stable flight, this is lifting off the ground. The problem here is that by the time enough force was being imparted to the wings from its own forward mounted engines, the plane would begin moving forward and it would take off normally. The answer to this question is that it depends on the plane, the position of the engines, the power of the engines vs the lift capacity of the wings etc. Given the type of model airplane and the ultralight airplane used in the show, neither had the power (or the configuration) to create independent lift even if they were tethered or had their brakes on. This issue is not related to the treadmill and the forces it imposes on the planes.

   Can a plane take off of a moving treadmill? Yes! if it has the power to offset the friction imposed by the treadmill. If the power only matches this force(granted a small force) then the plane will remain stationary. Airspeed over the wings will provide the required lift. Watch how a seagull can lift off the beach when enough wind provides the lift it needs. The seagull could be standing still or running on a treadmill and still take off.