Airbus, and Boeing, to name just two of today’s most produced commercial aircraft are equipped with engines under the wing. Aircraft manufacturers have made this choice for over 40 years.
Is it for better aerodynamics, fuel consumption, or what? We went to find out from engine manufacturer Snecma, a Safran Group subsidiary.
As Thierry Wilmet, Design & Manufacturing Support Department Manager explains, "the choice is the result of an aerodynamic compromise. We understand the aerodynamic integration of large engines below the wing very well. It allows for bigger engines, thus improving fuel consumption."
Even so, in the 70’s, Snecma and Rolls Royce developed the M45H turbofans for this 40-seater Fokker, which were mounted in pods on pylons above the wings. According to the engineers of the time, this principle reduced drag, the plane was less noisy, and the engines were protected against potential ingestion problems (debris thrown up from the ground). All the same, the concept was soon abandoned on commercial aircraft, notably because of one major drawback, being the weight of the engines.
Mounting the engines on over-wing pylons, requires a more complex wing structure, and additional reinforcement; added to which the fuel that is stored within the wing has to be pumped to supply the engine.
However, some commercial aircraft, such as the MD-80 or the Caravelle, opted for an aft fuselage mounted engine, as on some present day Embraer’s or Bombardier’s. On these narrower bodied aircraft, the landing gear has to be short in order for it to be retracted in flight. This in turn restricts an under wing engine position due to the plane’s lower ground clearance.