markinnorthtexa

Does anyone have links to information about wind tunnel test results of the Boeing 737 Max and the Airbus A320 Neo ? It looks like there is a design flaw in the work around that Boeing used in order to move the engines up high enough on the wing in order to be able to use these on this airplane. It would be interesting to compare how both airplanes compare in wind tunnel tests since both use similar engines. It looks like Airbus chose an airplane design where the engines are mounted under the wings whereas Boeing seems to have tried to move the engines up higher with some sort of strut that holds it high enough on the wing so that the engine will not touch the ground. Is this design naturally as aerodynamic as airplanes whose engines are mounted below the wings? I would like to learn more about all of this so that I can answer these questions. Thank you.

rickair7777

The 737 was designed in the 1960's. Engines used then were low bypass turbofans and narrow by today's standards. Boeing made the gear high enough for that engine, but not much higher. The wing box was then designed with space into which the gear could retract.

The bus was designed in the 80's, for larger, higher-bypass turbofans. So it's gear is taller.

Today's very high bypass engines are even wider. By chance, the bus had longer gear and could accommodate a wider engine.

The 737 (which had already gotten engines wider than the original during previous upgrades) simply had no more room under the wing. Lengthening the gear would be difficult (since the wing box was designed around that) so they relocated the engines forward and upwards, simply to fit them under the wing. So no advantage to that at all, just something they had to do by an accident of history. Which of course lead to the MCAS debacle.

Interestingly enough, the 737 MAX 10 actually needs longer gear, they couldn't make it work with just moving the motor. So that version will have a collapsible gear strut which well expand to the needed length when extended, and collapse to fit into the wing box for retraction.

Xray678

I’m not sure I would call it an accident of history. When Boeing built the 737NG they completely redesigned the wing. By that time the trend toward ever higher bypass engines (along with their larger size) should have been evident. When they were designing the new wing they should have made the changes required to the wing box to accommodate a taller landing gear.

rickair7777

They didn't know that there would be another generation of the 737. Actually most folks with industry awareness would have thought the safe money was on a clean-slate design next time around.

Mesabah

That's going to be interesting when the gear extension fails on the MAX 10.

rickair7777

You said it, but I've been thinking it.

I think it's still in development, so hopefully they take a good hard look at that before they commit to production.

Xray678

They didn’t know....I will grant you that. But even with the NG they should have lengthened the gear rather than flatten out the engine cowlings. At that point it would not have been too hard to make the gear a little taller.

BobZ

Anyone know if the NG and classic 737 gear strut and geometry are the same?

OOfff

I’d bet that if they didn’t know about the max, flattening a cowl bottom was WAY cheaper and more efficient than redesigning a wing box and landing gear

joepilot

The Boeing executive in charge of that decision got his bonus and retired.

Companies don't know things or make decisions. People do. Sometimes those decisions are in a persons short term best interest (bonus for "saving money"). This may well be against the company's best long term interest.

Joe