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The fallout for Boeing continues

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2 hours ago, reo said:

I havent looked in depth into their design decisions but I'll take a guess.

 

First off I'm not really sure why they wanted the larger engine. Someone on the outside might initially guess that it's a more powerful engine and although it might be, that's probably not the reasoning. A more powerful engine would be about increasing speed or acceleration but lift is a function of airspeed and wing design so more airspeed isn't really something they'd probably want. And as a commercial airliner, acceleration isnt really a factor either.

 

But a larger diameter engine could probably increase airflow through the intake which might make them more fuel efficient. My guess would be that's their reasoning. 

 

However if that's the case they don't really want to add more weight to do it bc more weight means they need more lift. Changing the landing gear height would mean more weight from the landing gears and changing the landing gear bays to accommodate the larger gears, possibly also adding more weight. This also meaning they'd either need to fly faster or more lift from the existing wings.

 

Instead they just out the new engines into the wings instead of under them figuring they'd still have plenty of lift to manage (and they do).

Once the airframe/wing is in a nose-up attitude, wouldn't an (bigger) engine with more thrust also increase the rate of climb?

Especially when it's loaded?

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2 hours ago, reo said:

I havent looked in depth into their design decisions but I'll take a guess.

 

First off I'm not really sure why they wanted the larger engine. Someone on the outside might initially guess that it's a more powerful engine and although it might be, that's probably not the reasoning. A more powerful engine would be about increasing speed or acceleration but lift is a function of airspeed and wing design so more airspeed isn't really something they'd probably want. And as a commercial airliner, acceleration isnt really a factor either.

 

But a larger diameter engine could probably increase airflow through the intake which might make them more fuel efficient. My guess would be that's their reasoning. 

 

However if that's the case they don't really want to add more weight to do it bc more weight means they need more lift. Changing the landing gear height would mean more weight from the landing gears and changing the landing gear bays to accommodate the larger gears, possibly also adding more weight. This also meaning they'd either need to fly faster or more lift from the existing wings.

 

Instead they just out the new engines into the wings instead of under them figuring they'd still have plenty of lift to manage (and they do).

I think you are right in that the engines were more about fuel efficiency, but some probably due to an increase in passenger capacity or future capacity increases. I did forget the 737 have the flush mounted rear landing gear so that would have required a complete re-design of the landing gear bays to accommodate longer landing gear. 

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reo   
1 hour ago, TitanDuckFan said:

Once the airframe/wing is in a nose-up attitude, wouldn't an (bigger) engine with more thrust also increase the rate of climb?

Especially when it's loaded?

Yeah, to a certain extent but that's not really  why planes pitch up. They pitch up to increase the angle of attack of the wings to the airstream which increases lift. Hold your hand out the window of your car. When you're level, you might feel a bit of upwards force but if you pitch up (increase the angle of your hand compared to the air flow) you'll increase the lift.

 

Now you get to a point where you've pitched up too far and most of the force is pushing your hand back instead of up and that's stall.

 

The 737 max would stall at a lower angle of attack than the other 737s. So the software would sense that and pitch it back down to prevent the stall.

 

The engines are really there to counter drag and propel you forward.

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6 minutes ago, reo said:

Yeah, to a certain extent but that's not really  why planes pitch up. They pitch up to increase the angle of attack of the wings to the airstream which increases lift. Hold your hand out the window of your car. When you're level, you might feel a bit of upwards force but if you pitch up (increase the angle of your hand compared to the air flow) you'll increase the lift.

 

Now you get to a point where you've pitched up too far and most of the force is pushing your hand back instead of up and that's stall.

 

The 737 max would stall at a lower angle of attack than the other 737s. So the software would sense that and pitch it back down to prevent the stall.

 

The engines are really there to counter drag and propel you forward.

AIRPANE ENGINEER AIRPANE ENGINEER! HAHAHAHAHAHAHAHAHA 

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1 hour ago, reo said:

Yeah, to a certain extent but that's not really  why planes pitch up. They pitch up to increase the angle of attack of the wings to the airstream which increases lift. Hold your hand out the window of your car. When you're level, you might feel a bit of upwards force but if you pitch up (increase the angle of your hand compared to the air flow) you'll increase the lift.

 

Now you get to a point where you've pitched up too far and most of the force is pushing your hand back instead of up and that's stall.

 

The 737 max would stall at a lower angle of attack than the other 737s. So the software would sense that and pitch it back down to prevent the stall.

 

The engines are really there to counter drag and propel you forward.

Yeah I get how wings work to create lift.  BTDT

Were the design changes to the MAX version of the 737 restricted to the fuselage/cabin and engine re-fit?  Or did they also change elements of the wing (length, control surfaces etc.) to accommodate the increased load?

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9 minutes ago, TitanDuckFan said:

Yeah I get how wings work to create lift.  BTDT

Were the design changes to the MAX version of the 737 restricted to the fuselage/cabin and engine re-fit?  Or did they also change elements of the wing (length, control surfaces etc.) to accommodate the increased load?

Yeah, I don't make any assumptions to what people know or don't.

 

Haven't looked into it extensively but I think it was pretty much limited to engine placement. They didn't do anything to the wings bc they didn't have to. If anything they were decreasing lift by adding the bigger engines.

Edited by reo

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The video earlier pretty much stated it was 100% because of fuel consumption that they threw new engines on it. 

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2 hours ago, titanruss said:

The video earlier pretty much stated it was 100% because of fuel consumption that they threw new engines on it. 

Yeah, which is lower bc the air intake is larger I think but it's been a while since I've done anything with air breathing propulsion. We do inlet tests at work but we don't do any of the calcs on pressure differentials or gas expansions involved in those types of engines. 

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16 minutes ago, reo said:

Yeah, which is lower bc the air intake is larger I think but it's been a while since I've done anything with air breathing propulsion. We do inlet tests at work but we don't do any of the calcs on pressure differentials or gas expansions involved in those types of engines. 

They said that it was a larger /more powerful AND more fuel efficient engine. .. but it was just tacked on without thought in order to compete with Airbus' new better and ore fuel efficient engine. 

 

Boeings sits too low to the ground and limited lift on takeoff. Pilots were told it will fly "exactly" the same.. so pilots were flying it and werent gaining the altitude the thought they should be and were over-correcting.  Boeing made the software fix to increase lift on takeoff and limit the overcorrection but then if the sensors were fucked, it kept making the plane nosedive. 

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7 hours ago, titanruss said:

They said that it was a larger /more powerful AND more fuel efficient engine. .. but it was just tacked on without thought in order to compete with Airbus' new better and ore fuel efficient engine. 

 

Yes.... I said it might be more powerful as well as more efficient but the more power probably didn't matter as much. 

 

Quote

Boeings sits too low to the ground and limited lift on takeoff. Pilots were told it will fly "exactly" the same.. so pilots were flying it and werent gaining the altitude the thought they should be and were over-correcting.  Boeing made the software fix to increase lift on takeoff and limit the overcorrection but then if the sensors were fucked, it kept making the plane nosedive. 

The plane was stalling at higher angles of attack and the software was to autocorrect the pitch angle to prevent the stall. The faulty sensors incorrectly read the conditions and said it was stalling when it wasn't. 

Edited by reo

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12 hours ago, reo said:

Agree. They definitely aren't going under. If you look at their overall track record, it is good, including their military projects.

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