Car vs Boeing 747 Engines - Top Gear Style

Richard Hammond tests whether a car can survive standing behind a Boeing 747 at power. A Citroën 2CV and a Ford Mondeo volunteer. Neither wins.

The numbers behind the stunt

Each engine on a 747-400 produces around 60,000 lb of thrust; the GEnx-2B on the 747-8 produces 66,500 lb. Four of them together push roughly a quarter of a million pounds.

But thrust is not really what wrecks the cars. What matters is the mass flow: a high-bypass turbofan of that size moves well over a tonne of air every second, and jet blast behind an aircraft at takeoff power can exceed hurricane wind speeds for a considerable distance behind the tailpipe.

Wind force rises with the square of velocity, so a jet blast at twice the speed hits four times as hard. A 2CV weighs about 600 kg. It is not a fair contest.

This is a real operational hazard

Airports take jet blast seriously enough to build infrastructure around it. Blast fences stand behind runup areas and at the ends of taxiways at many airports; ground crews work to marked minimum distances behind aircraft; and blast has repeatedly blown over ground vehicles, luggage carts and, at St Maarten’s famous Maho Beach, people.

The 747’s four engines spread that energy across a wider arc than a large twin does, but at close range that is little comfort.

The related failure mode

Blast is thrust going backwards deliberately. Reverse thrust is the same energy redirected forward — which is why a 747 landing on a wet runway throws up a wall of spray.

Related

• The GEnx-2B engine
• Reverse thrust on landing
• The 747-400