Imagine you’re driving at the maximum speed allowed on a major highway and you have to suddenly stop the car.
It’s basically what Boeing test pilot Captain Kirk Vining had to do recently with the new 747-8 Freighter during one of the most dramatic airplane certification tests. However, instead of a 4,000-pound (1815 kilograms) car, the 747-8 weighed in at close to one million pounds.
“In the emergency event that we have to make a rejected takeoff at these heavy weights, it takes a long distance for the airplane to stop,” says Capt. Vining.
The Boeing 747-8 Intercontinental and 747-8 Freighter are the new, high-capacity 747s that offer the lowest operating costs and best economics of any large passenger or freighter airplane. Both are on track to make their first deliveries later this year after certification.
In April, the Boeing Test & Evaluation team brought the 747-8 Freighter to a long runway in California to simulate the ultimate rejected takeoff (RTO). Crews loaded the airplane above its maximum takeoff weight of 975,000 pounds (443,181 kilograms) and installed a set of 100% worn-out brakes.
“It’s down to the studs,” says Andy Hammer, the 747-8 flight test manager. “They’ve got them machined down so there’s basically no material left.”
Capt. Vining taxied the airplane out to the start of the runway and began the takeoff roll as usual by pushing all four engines to maximum thrust.
Just as the airplane was going over 200 miles per hour (320 kilometers per hour), Capt. Vining slammed on the brakes. To channel maximum energy to the carbon brakes, he was not allowed to use the thrust reversers.
“It’s just brakes,” says Hammer, explaining why the condition is also called the maximum brake energy test. “The whole intent is to demonstrate that under the worst conditions you can safely bring the airplane to a stop.”