Would you fly on a 737 Max?

[Eric Mc]

I am pretty sure it was an internal management decision.

[MarkwG]

Halmyre said:

But was the decision to build the 737 MAX customer driven or cost-driven? Surely the customers would have preferred a completely new aircraft instead? Or did Boeing have them over a barrel - well, we can sell you the 737 MAX at such and such a price or a new 7XX but it'll be 10% more expensive.

The problem stems from the need for certification for a new aircraft & the huge costs that involves: by basing the design on an older model, the manufacturer bypasses those costs - it's called Grandfather or acquired rights. The costs involved are massively different, which makes it worthwhile to do, but the rules can only be stretched so far. The basic frame of the 737 is low wing, under slung engines, however, stretching the fuselage length to accommodate more passenger load requires bigger engines; bigger engines demand longer undercarriage legs, which need to be tucked away inside the fuselage for flight; there's a finite limit on how long/heavy they can be, at which point, other solutions/compromises need to be employed to make the gains required. Some, such as flattening the underside of the engines, have unintended consequences with the aerodynamics, which have to be mitigated in other ways. The end result is a compromised aircraft, but still much cheaper than starting from fresh - but Murphy has many way of biting you on the 4rse...

[anonymous-user]

Plus also Airbus came up with the A320 neo and all Boeing had was the B737 so decided to quickly bodge a 737 into the MAX as a competitor,rather than develop an entirely new type.

Obviously now this looks like an even worse decision as Boeing still doesn’t have a new type and Max activity has been a bit thin recently.

Again this goes back to problems Boeing created with all the outsourcing on the B787 and the problems they had with it, which then delayed the 737 replacement which now looks more like a ‘midsized’ 757 replacement.

Interesting to lookback on Boeing’s plans with project Yellowstone.

https://en.wikipedia.org/wiki/Boeing_Yellowstone_P...

The Y2 was originally going to be the sonic cruiser which post 9/11 became the B787 and the Y1 and Y3 are all on hold.

[Munter]

MarkwG said:

The problem stems from the need for certification for a new aircraft & the huge costs that involves: by basing the design on an older model, the manufacturer bypasses those costs - it's called Grandfather or acquired rights. The costs involved are massively different, which makes it worthwhile to do, but the rules can only be stretched so far. The basic frame of the 737 is low wing, under slung engines, however, stretching the fuselage length to accommodate more passenger load requires bigger engines; bigger engines demand longer undercarriage legs, which need to be tucked away inside the fuselage for flight; there's a finite limit on how long/heavy they can be, at which point, other solutions/compromises need to be employed to make the gains required. Some, such as flattening the underside of the engines, have unintended consequences with the aerodynamics, which have to be mitigated in other ways. The end result is a compromised aircraft, but still much cheaper than starting from fresh - but Murphy has many way of biting you on the 4rse...

All of those problems wouldn't matter though if they had not deliberately designed in a single point of failure in the control system. 2 or more AoA sensors, an "AoA disagreement" warning. Voila, no crashes, and a safe (if imperfect) plane flying about the place. The other stuff you can weigh up and see benefits and consequences, it's decisions that can be made.

Single point of failure, in a control system, that's so fundamentally dumb with no upsides to argue for it, it's hard to comprehend how it got out the door.

[MarkwG]

Munter said:

MarkwG said:

The problem stems from the need for certification for a new aircraft & the huge costs that involves: by basing the design on an older model, the manufacturer bypasses those costs - it's called Grandfather or acquired rights. The costs involved are massively different, which makes it worthwhile to do, but the rules can only be stretched so far. The basic frame of the 737 is low wing, under slung engines, however, stretching the fuselage length to accommodate more passenger load requires bigger engines; bigger engines demand longer undercarriage legs, which need to be tucked away inside the fuselage for flight; there's a finite limit on how long/heavy they can be, at which point, other solutions/compromises need to be employed to make the gains required. Some, such as flattening the underside of the engines, have unintended consequences with the aerodynamics, which have to be mitigated in other ways. The end result is a compromised aircraft, but still much cheaper than starting from fresh - but Murphy has many way of biting you on the 4rse...

All of those problems wouldn't matter though if they had not deliberately designed in a single point of failure in the control system. 2 or more AoA sensors, an "AoA disagreement" warning. Voila, no crashes, and a safe (if imperfect) plane flying about the place. The other stuff you can weigh up and see benefits and consequences, it's decisions that can be made.

Single point of failure, in a control system, that's so fundamentally dumb with no upsides to argue for it, it's hard to comprehend how it got out the door.

Indeed - all part of a fundamentally flawed policy where commercial outweighs safe engineering principles. Lessons already learned, then ignored.

[griffdude]

I’ll be flying the Max next year. Looking forward to it in fact.

Just a shame Boeing decided to go down the stretch 737 route instead of an all new 757. Now that was a great aircraft to spend the day in (just a bit noisy & the brown...).

[montymoo]

griffdude said:

I’ll be flying the Max next year. Looking forward to it in fact.

Just a shame Boeing decided to go down the stretch 737 route instead of an all new 757. Now that was a great aircraft to spend the day in (just a bit noisy & the brown...).

A revised 757 would have been fantastic and is such a shame they didn't go down this route.
Strangely enough I am not looking forward to the max, and I actually prefer an older ng to the newer ones, they all feel a bit plasticy.
However if all goes well I will have to fly one too. Hope I'm not gonna be the one to drop the gear in the after t/o checks.

[anonymous-user]

The other point is that nobody will actually be flying on “the max” because nobody will be calling it a “max” anymore.

Passenger “is this a 737 max?”
Crew “no it’s a 737 dash seven, eight or nine” etc

Or

Passenger “Is this a max?”
Crew “No it’s a 737-8200”

I doubt any airline will be using the word “Max” anywhere. Boeing still seem to be using it but I think that might even change after it returns to service.

Edited by anonymous-user on Wednesday 11th November 08:49

[Halmyre]

griffdude said:

I’ll be flying the Max next year. Looking forward to it in fact.

Just a shame Boeing decided to go down the stretch 737 route instead of an all new 757. Now that was a great aircraft to spend the day in (just a bit noisy & the brown...).

According to Wikipedia Boeing are considering a 757 revival.

I'm curious, why would they have dropped the 757 in favour of the 737? It's much longer than the 737, but they could shorten the fuselage and be able to fit more efficient engines without compromising their installation.

[williamp]

montymoo said:

A revised 757 would have been fantastic and is such a shame they didn't go down this route.
Strangely enough I am not looking forward to the max, and I actually prefer an older ng to the newer ones, they all feel a bit plasticy.
However if all goes well I will have to fly one too. Hope I'm not gonna be the one to drop the gear in the after t/o checks.

I always thought the 757 was a handsome design. Was their use on 9/11 part of the reason why orders dried up?

[MarkwG]

williamp said:

montymoo said:

A revised 757 would have been fantastic and is such a shame they didn't go down this route.
Strangely enough I am not looking forward to the max, and I actually prefer an older ng to the newer ones, they all feel a bit plasticy.
However if all goes well I will have to fly one too. Hope I'm not gonna be the one to drop the gear in the after t/o checks.

I always thought the 757 was a handsome design. Was their use on 9/11 part of the reason why orders dried up?

No, not related to that, it was down to the maths. IIRC the 757 was effectively a "thin" 767, using the same wing design, & was effectively very over engineered as a result, which equalled relatively expensive to build & operate.

[anonymous-user]

williamp said:

I always thought the 757 was a handsome design. Was their use on 9/11 part of the reason why orders dried up?

No they’re just old and the engines are too big and use too much fuel.

They’re great for landing and take off performance and certain distance flights but the newer 737s carry almost as many people and are doing it cheaper.

You still see them around as airlines can get them really cheap and they’re still great for mid range flights like U.K. to canaries or even some of the shorter trans Atlantic routes.

There will be a replacement in this sector eventually as Boeing have a pretty big gap in newer aircraft between the max and the 787-8 but Boeing have had their fingers burned a lot recently so it’s put their plans back somewhat.

[Dr Jekyll]

MarkwG said:

No, not related to that, it was down to the maths. IIRC the 757 was effectively a "thin" 767, using the same wing design, & was effectively very over engineered as a result, which equalled relatively expensive to build & operate.

Wasn't the 757 initially conceived as a twin engined 727 and only adapted to use 767 bits later in the process?
Boeing did seem to have an obsession with making every model a version of another if vaguely possible.

[Eric Mc]

One of the main selling points promoted by Boeing in the late 70s/early 80s was that a pilot trained on a 757 was also qualified on the 767 - or vise versa. The point being that an airline could cut down on training costs if it operated both types. In the end, not that many airlines had fleets containing both 757s and 767s.

The problem for Boeing later is that when they decided that they needed to continue with a narrow bodied twin in their range, they chose to modernise the 737 line rather than the 757 line.

The 737 project began in 1965. The 757 project began around 10 years later - so the 757 was a more modern design to start with.

[JuniorD]

Seems some people have still have reservations on flying on a 737-Max but would they be happy flying on a 737-8?

[MarkwG]

Dr Jekyll said:

MarkwG said:

No, not related to that, it was down to the maths. IIRC the 757 was effectively a "thin" 767, using the same wing design, & was effectively very over engineered as a result, which equalled relatively expensive to build & operate.

Wasn't the 757 initially conceived as a twin engined 727 and only adapted to use 767 bits later in the process?
Boeing did seem to have an obsession with making every model a version of another if vaguely possible.

Quite possibly - like car manufacture, the more parts in common, the bigger the saving, the cheaper the end product for the customer. Manufacturers often run a number of different ideas in parallel, then back the one the most customers opt for. I think the modified 727 idea ran out of steam when the benefits of the 757 design were fully appreciated. As Eric says above, training is a huge cost for the company (after a career in training I hate that it's a cost not an investment, but that's the way it is), so commonality reduces that cost too - airlines love that, as all that cost is notionally loaded onto them, rather than built into the sale price of the aircraft. Airbus spotted that from the start, & capitalised on it, Boeing were playing catch up a bit.

I guess there's also a finite limit on how big an engine you can hang off the rear fuselage, vs under the wings, & once you move the engines, the T tail becomes a bit redundant.

[Leon R]

Do people put this level of thought into they type of engines that the aircraft they are flying on has?

[MarkwG]

Leon R said:

Do people put this level of thought into they type of engines that the aircraft they are flying on has?

Nope - the only time that arises is when the choice is between jet or propeller, & that's still a tiny percentage of passengers who would worry about that. The major factor is always ticket price.

[Eric Mc]

I presume by "people" you mean "passengers". If that is the case, of course not.

However, for designers and operators of airliners, the type of engines and their location on the aircraft is pretty fundamental.

The chief issue with the 737 is actually the size and location of the undercarriage. When the aircraft was originally designed in 1965/66, it was fitted with very slimline Pratt and Whitney JT8D low bypass turbofans. This allowed the aircraft to have a fairly short-stroke undercarriage. This was considered a good feature at the time as it brought the engines close to the ground, making them easier to access and therefore quicker, easier and cheaper to maintain - as working on the engines did not need gantries, platforms etc.

When the second generation 737s emerged in the early 1980s, they were fitted with much fatter high-bypass CFM56 engines. This necessitated a relocation of the engines forward of, rather than underneath, the wing as the ground clearance was much less. It also involved relocating some of the engine ancilliaries to the side of the engine to keep ground clearance

With the Max, the engine is even bigger which involves moving the engine up a bit. That is what has caused all the aerodynamic issues which they "fixed" with software.

Original 737-100



737-200



737-300



737-800



737-Max

[MarkwG]

^evolution photos^ - that's very good, shows how the original engines were 100% underslung, whereas the MAX (or whatever it becomes..) are ahead of the leading edge, & how that developed over time.