The converyor belt question

[Stealth Pilot <tailwind@xxxxxxxxxxxx>]

>The question:
>
>There's an airplane (what type of plane is immaterial, as long as it's not
>VTOL) sitting on a huge conveyor belt the length of the runway.  Now this
>conveyor belt is designed in such a way that it will perfectly match the
>speed of the airplane, but traveling in the opposite direction!
>
>So, for example, if the plane takes off to the west, the conveyor belt
>travels towards the east.  It's a perfectly calm day with absolutely no
>breeze to speak of.
>
>Will the aircraft be able to take off?
>

Of course it will.
The tyres will be rotating at twice the normal takeoff rpm.
It's air velocity will be the normal takeoff airspeed.
Since a powered aircraft typically has a stall speed to velocity never
exceed speed ratio of 1:4 or 1:5 it shouldnt be a problem.

Takeoff speed is usually 1.3 times the stall speed.

Certification sees  most aircraft stall below 50 knots so there isnt
too much variation in the speeds in consideration.

Most aircraft tyres are rated to 120knots so they should be able to
handle the task.

See the reality is that the wheels are usually on greased taper roller
bearings so the behaviour of the conveyor belt is almost not a
consideration.

Now a question for you.
The aircraft normally takes 600yards to land to a halt.
If it took off and landed back on your conveyor with the same conveyor
speed concepts as before, how long a distance would it take to stop if
the brakes werent used? 

Stealth Pilot
Australia