4 ms·

The engines on the original 737 design were quite small by modern standards, and the wings were low as well. As such there aren't really a ton of places to put

The engines on the original 737 design were quite small by modern standards, and the wings were low as well. As such there aren't really a ton of places to put new, larger engines. They basically have to be placed further forward and higher up. This means the pitch moment created by throttling up/down is different on different versions of the 737, which is what required the MCAS device in the first place - they were trying to make sure the 737 MAX flew the same as previous models.

chrisseaton 7y ago
I think you’re just repeating the impact of the low ground clearance, rather than explaining why there still has to be low ground clearance. You’ve said they can’t have larger engines because ground clearance is low... we already know that... but why must ground clearance be low?
- supergauntlet 7y ago
  Ah, you mean why did they originally do it? Sorry, I misunderstood. The original reason was that the 737 was designed that way so that it could be boarded with just stairs instead of a skybridge: https://simpleflying.com/737s-low-to-the-ground/ https://simpleflying.com/737s-low-to-the-ground/ This was super helpful to small carriers at the time, but as time has gone on it's caused problems.
  - deleted 7y ago
    [deleted]
- GiorgioG 7y ago
  Because they would have to redesign the parts of the fuselage that holds the landing gear when they are retracted - as far as I know, there's not enough room to house taller landing gear.
  - tropo 7y ago
    Boeing did actually design extendable landing gear for the 737 MAX-10 model, which hadn't shipped yet. That aircraft is longer. To avoid tail strikes, the rear gear becomes longer as the aircraft is taking off. I'm sure that costs more money. If it were on all 737 MAX aircraft, perhaps the engines could be lower. It'd be like a kneeling bus that gets lower when stopped to take on passengers. Another option would be to make the engines move. They could be folded up or slid up-forward when driving around the airport. The FAA might have issues with this though. I don't know of any aircraft that does transformer stuff while zooming down the runway.
    - lutorm 7y ago
      True, there are planes that compress the struts before retracting the gear for the gear to fit, so perhaps something like this could be designed for the 737 too? But that's increased complexity on a non-redundant part that you definitely don't want to fail, so it's not obvious how the trade comes out...
      - tropo 7y ago
        Not "perhaps". It actually was designed for the 737 MAX, which comes in 4 lengths. Only the long one gets the fancy gear. Short video with gear model in action: https://www.youtube.com/watch?v=F4IGl4OizM4 https://www.youtube.com/watch?v=F4IGl4OizM4 https://www.geekwire.com/2018/boeing-737-max-10-landing-gear/ https://www.geekwire.com/2018/boeing-737-max-10-landing-gear... Scroll down for a nice diagram: http://www.b737.org.uk/737max10.htm http://www.b737.org.uk/737max10.htm
        VBprogrammer 7y ago
        To be fair a similar system on the Dash 8 Q400 has a pretty nasty habit of folding up on landing.
    - magduf 7y ago
      You're talking about changes that would cause the plane to be a very different plane than the 1967 737, and would then need a new type rating. If you're going to do that, you might as well just throw out the 737 design altogether and make an all-new clean-sheet design. Boeing wanted to avoid that because that costs a lot more money and pilots would need retraining on the new type. They wanted to be able to call this piece of junk a "737" and claim that pilots didn't need any new training to fly it.
- dralley 7y ago
  Because the airlines use hangars that are built for the current dimensions of the 737, not a bigger airplane. And also you can't just redesign the landing gear without redesigning a substantial portion of the wings.

chrisseaton 7y ago

I think you’re just repeating the impact of the low ground clearance, rather than explaining why there still has to be low ground clearance. You’ve said they can’t have larger engines because ground clearance is low... we already know that... but why must ground clearance be low?

supergauntlet 7y ago
Ah, you mean why did they originally do it? Sorry, I misunderstood. The original reason was that the 737 was designed that way so that it could be boarded with just stairs instead of a skybridge: https://simpleflying.com/737s-low-to-the-ground/ https://simpleflying.com/737s-low-to-the-ground/ This was super helpful to small carriers at the time, but as time has gone on it's caused problems.
- deleted 7y ago
  [deleted]
GiorgioG 7y ago
Because they would have to redesign the parts of the fuselage that holds the landing gear when they are retracted - as far as I know, there's not enough room to house taller landing gear.
- tropo 7y ago
  Boeing did actually design extendable landing gear for the 737 MAX-10 model, which hadn't shipped yet. That aircraft is longer. To avoid tail strikes, the rear gear becomes longer as the aircraft is taking off. I'm sure that costs more money. If it were on all 737 MAX aircraft, perhaps the engines could be lower. It'd be like a kneeling bus that gets lower when stopped to take on passengers. Another option would be to make the engines move. They could be folded up or slid up-forward when driving around the airport. The FAA might have issues with this though. I don't know of any aircraft that does transformer stuff while zooming down the runway.
  - lutorm 7y ago
    True, there are planes that compress the struts before retracting the gear for the gear to fit, so perhaps something like this could be designed for the 737 too? But that's increased complexity on a non-redundant part that you definitely don't want to fail, so it's not obvious how the trade comes out...
    - tropo 7y ago
      Not "perhaps". It actually was designed for the 737 MAX, which comes in 4 lengths. Only the long one gets the fancy gear. Short video with gear model in action: https://www.youtube.com/watch?v=F4IGl4OizM4 https://www.youtube.com/watch?v=F4IGl4OizM4 https://www.geekwire.com/2018/boeing-737-max-10-landing-gear/ https://www.geekwire.com/2018/boeing-737-max-10-landing-gear... Scroll down for a nice diagram: http://www.b737.org.uk/737max10.htm http://www.b737.org.uk/737max10.htm
      - VBprogrammer 7y ago
        To be fair a similar system on the Dash 8 Q400 has a pretty nasty habit of folding up on landing.
  - magduf 7y ago
    You're talking about changes that would cause the plane to be a very different plane than the 1967 737, and would then need a new type rating. If you're going to do that, you might as well just throw out the 737 design altogether and make an all-new clean-sheet design. Boeing wanted to avoid that because that costs a lot more money and pilots would need retraining on the new type. They wanted to be able to call this piece of junk a "737" and claim that pilots didn't need any new training to fly it.
dralley 7y ago
Because the airlines use hangars that are built for the current dimensions of the 737, not a bigger airplane. And also you can't just redesign the landing gear without redesigning a substantial portion of the wings.