This acceleration is for any change in speed. It doesn’t matter if the object increases or decreases in speed – it is still an acceleration. If you know the acceleration for something, you can find the stop speed by using the following kinematic equation (this is a cross-reference if you want it).
In this sentence, v1 is the starting speed (20 mph in this account) and v2 the final distance would be – hopefully zero since it stopped. Therefore, with known acceleration the stop speed (Δx) would be:
Now I need to get value for the Boeing 747 stop acceleration. Ah ha! That is not so easy. Yes, large planes stop all the time – it’s usually called “landing.” However, the usual landing method doesn’t work here. Large aircraft like the Boeing 747 typically use two things to slow down. Not only does it use the wheels, which have brakes, but there are also rear thrusts. The rear thrusts are essentially forces from the engines directed backwards (hence the “back” part). This pushing back force, along with the brakes, slows down the plane.
For this stunt enter Tenet, the 747 will only have brakes since it is not a full-fledged aircraft. So what acceleration would there be if a plane did not use the rear thrushes? Well, we are in good luck. This is called a rejection test (RTO). For this movement, a plane starts and takes off to remove speed. At that point, the pilot applies his brakes (or rear thrusters) and stops. It is a worst-case test to make sure the plane’s brakes can handle real issues.