Dear all,

Thanks so much for all the postings on this very controversial topic. I wanted people to have the opportunity to hear from me about my opinion as the show's executive producer. For me and my team, it's very important that I categorically state for the record that our results for POCB are 100% accurate. Period. A plane on a treadmill where both the plane and treadmill are going the plane’s take-off speed (but in opposite directions) will ALWAYS move forward and therefore will ALWAYS take off. It is completely impossible for the plane to be held in place by the conveyer belt at this speed. Our results are correct.

Plenty of people more qualified than I have tried to to explain why this happens, but I will reiterate it again here. I suspect that the ‘no-flys’ will still think this is incorrect but put simply it’s not! Let’s start from the top. Here’s what Adam said in the blueprint opener:

Adam: “Let me spell it out for you, normally a plane sits on the runway, spins up its engines, moves forwards gets enough air over its wings and takes off. But in this case, the plane is sitting not on the runway, but a huge conveyor belt that is matching the planes forward speed in reverse, and the grand question is can the plane take off? The myth is that it can’t".

A lot of the confusion seems to stem from how the myth is interpreted. The ‘noflys’ seem to think that with the belt going backward at 25mph and the plane forward at 25, the plane will stay where it is neither moving forward nor backward. Given this situation, will the plane suddenly rise into the air like a helicopter? Unfortunately this interpretation of the myth is not correct because this situation is simply impossible. At take off speeds, the plane will ALWAYS move forward and will NEVER stay where it is.

And seriously, if you don’t believe me, why not try it for yourself - get a treadmill and put an RC plane on it. Repeat our experiment and you will get the same result. When both belt and plane are going at the plane’s take off speed, the plane will move forward accelerating to its take off velocity and therefore it will lift off. Here’s something else you may want to try - even if the conveyer belt is going twice, three times or 50 times the plane’s take off speed, the plane will still move forward!

So the idea that the plane will stay stationary is bogus. But why? Well the reason for this, as many people have explained (including Adam), is that a plane gets its thrust independently of its wheels. And that means it’s very different from a car. Put a car on a treadmill and match its speed to the belt and the car will stay put. The speed of a car is set by how rapidly the engine is rotating and what ratio the transmission is set to. This is directly linked to the wheels which then turn producing motion. However the thrust of an airplane does not directly cause its wheels to turn - the two vehicles work very differently in that regard. Instead an airplane’s speed is controlled by its engine thrust which acts on the air courtesy of the propeller or jet engine. Because of this, the speed of the airplane is air speed and is COMPLETELY independent of the wheel speed.

Now, ‘noflys’ instead of just trying to spot the mistake (which doesn’t exist), please consider this concept for a moment to see if actually you may agree with it. And as said already, if you’re still doubtful, try it! Planes on treadmills at take off speeds will always move forward.

Finally, let me try to end with an analogy so that we don’t need to keep thinking about this in pure physics: Imagine that you are on a regular running treadmill at the gym. The treadmill is going backwards at 10 mph and you are jogging forward at 10 mph. So you stay in the same place and don’t fall off, right? Now instead of running get on a skate board. You propel the skate board forward at 10 mph and therefore still stay in the same place. You are now behaving like a car. But now tie a rope around your waist and throw it to your gym buddy who is standing in front of the treadmill. Get them to hold the rope taught and walk forward at 1 mph. You will be pulled along the treadmill until you fall off the front. Dust yourself off and get back on the treadmill and repeat at 25 mph, even with your buddy moving forward at 1 mph, you will always be pulled off the end. Repeat at 50 mph, at 100, even 1000 mph you will always fall off the front even with your buddy at 1 mph let alone a realistic plane take off velocity!

In this analogy, your gym buddy is like an airplane’s engine. The force he exerts has nothing to do with the treadmill or the skateboard’s wheels - he is completely independent of the treadmill. Replace the skateboard with a plane’s hull and wheels, and your friend and rope with a plane’s engine and hey presto you’ve got a plane on a conveyer belt that moves forward.

So the mythbusters were 100% accurate after all. And finally, if you still don’t believe it, then try it yourselves, and you’ll see that it’s Myth Busted.

Until soon,

Dan