Better safe than sorry


Flight instructor Cord Becker is a former Lufthansa pilot with around 20 000 flight hours under his belt. He also writes for Lufthansa Magazin on aviation topics. This month, Cord Becker talks about engine redundancy

Do you know how many engines are powering the plane you are sitting in right now? If it’s a short-haul flight and you guessed two, you’re probably right. But on a long-haul flight across the Atlantic, for instance, the correct answer isn’t quite so obvious.

engine redundancy

Efficient powerhouse: An engine belonging to the new long-distance Lufthansa Boeing 747-8

© Jens Görlich/ MO CGI

 There are three possibilities: two, three or four engines. Soon, however, there will be only two options, because the three-engine aircraft, or trijet, is on its way out. Lufthansa only has a single trijet in its fleet: an MD-11F operating for its subsidiary Lufthansa Cargo. It’s usually twin- and four-engine jets you’ll see sharing the duties above the clouds; among them aircraft of identical size and with identical seating capacity, but equipped with a different number of engines.

For safety reasons, single-engine aircraft are never used for passenger services; passenger planes must be equipped with at least two engines to meet the requirements for engine redundancy. In fact, to be absolutely on the safe side, commercial airline pilots automatically take into account the possibility of engine failure when preparing for takeoff. But modern jet engines have become so reliable that it makes virtually no difference whether planes are equipped with two or four of them, even on longer flights.

This wasn’t always the case: The famous Lockheed Super Constellation, affectionately known as the “Super Connie,” was called the “world’s finest tri-motor” in the 1950s and ’60s. Why? Although it was equipped with four large twin-row radial engines, one of them seemed to fail regularly. Today’s twin-engine aircraft can fly higher, farther, faster and more safely than airplanes back in the days of the Super Constellation.

Modern wide-body aircraft like the Airbus A380 or the Boeing 747, however, can easily weigh up to 500 tons and would not be able to leave the ground equipped with only two engines. They need at least four, because no engine developed so far is powerful enough to lift such giant aircraft off the ground with fewer. But in the end, it doesn’t matter whether the aircraft you’re sitting in is equipped with two engines or four: You’re perfectly safe either way.