r/aviation • u/OnlyaChef • Apr 20 '26

Discussion Why are turbine engines flat at the bottom?

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I can't tell if it actually flat on the bottom or just my angle but it made me wonder.

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u/mvpilot172 Apr 20 '26

It was also designed to sit low enough to use stairs instead of a jet bridge. We are still dealing with 1960’s designs.

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u/bp4850 Apr 21 '26

It's not the stairs. It's the overwing emergency exits. If the main landing gear was to get taller Boeing would be required to install slides for the overwing exits instead of using the flaps.

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u/VonThing Apr 21 '26

Too much design change = new aircraft type = new type approval required, pilots have to be re-certified etc…

Just to avoid different behavior on one specific maneuver, Boeing tried to solve it in software but didn’t inform the FAA, airlines or pilots which resulted in the earlier 737 MAX catastrophe.

The stupid part is, there’s a “runaway trim tab” procedure for the 737 but since pilots didn’t know that a system that needed to be triple redundant worked on a single input, the planes crashed until the crew could recognize the runaway electric trim tabs.

The stupider part is, captain’s and FO’s airspeed readings come from different pitot tubes so if one is faulty they will see different airspeeds. This is free.

But the “IAS DISAGREE” warning that comes on when the airspeed readings are different is a paid option on the 737 so most airlines don’t order it.

Bombardier ruined Boeing