Regional Jets

[lovejoy0120]

Why are the engines always mounted on the back and how and why are regional jets different from boeings/airbuses etc.

Thanks

[trevHCS]

Not really sure what you mean by a "regional jet"?

The only ones I know with the engine on the back are the military type and I assume that's practicality since they are relatively small and need to carry the weaponry & fuel in tanks on the wings.

The larger jets like boeing need a lot more engines and don't need to be able to turn in quite the same way, so putting them on the side is a better design idea especially as one large engine would take up a huge amount of the cabin space.

[Clanad]

Actually, the design is quite ancient by today's standards. The French Carvelle first utilized the design in the early 1960's. This was followed by the British BAC-111 and then the Douglas DC-9 in about 1966. The design allows for a greater weight and balance envelope, quieter cabin and better lift generation from the wings enabling the use of shorter runways at more "local" airports... at least in the 1960's. The design has been copied on a smaller scale by the Canadian firm Bombardier fro the CL-600 as well as the Brazilian firm, Embraer. The use of the "T" tail also provides some aerodynamic advantages... and neccessary for the use of rear mounted engines...

[blue virgin]

Also, you'll find that the latest Embraer models of Regional Jets (170, 190 etc) have underwing mounted engines.

[Ralph]

You'll also find that regional jets and the smaller planes from the "big boys" (737, A319) are designed for more "cycles". A cycle is one cabin pressurisation or in other words, one take off and one landing.

This pressurisation stresses the fuselage and in time will increase the likelihood of fatigue failures. A B777 flying from London to Singapore will possibly go through 2 cycles per day where a BAe 146 flying from Manchester to Dublin may go through 10 or 20 (complete guess!). Unless the structure is engineered for these higher cycles, it's effective working life would be reduced significantly.

You can get high-cycle big planes like the B747's they use in Japan since they're moving so many people internally, they need big planes. These are heavier though. A long haul operator won't want the extra weight because it costs money to fly this extra metal (or composite) around for the life of the plane.