StudiodeKadent
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Double stretches of an aircraft, why don’t they work?

Sat Apr 07, 2018 6:02 am

I've heard a number of times that "double-stretches" of an aircraft "never work."

Is there a reason for this?
Last edited by qf789 on Sat Apr 07, 2018 6:48 am, edited 1 time in total.
Reason: Updated title for clarity
 
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LAX772LR
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Re: question, may be a touch technical...

Sat Apr 07, 2018 6:10 am

Obviously, this isn't an absolute, as the 739ER is doing just fine. The 779 will likely be a winner as well.

But yes, the likes of the 764ER, 753, A346, 748i were total dogs in terms of sales... but they perform well.

There are factors beyond just being a double-stretch (and therefore less optimized for wing/engines/etc), usually timing and more-optimized competition. It's not a simple answer.
I myself, suspect a more prosaic motive... ~Thranduil
 
StudiodeKadent
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Re: question, may be a touch technical...

Sat Apr 07, 2018 6:29 am

LAX772LR wrote:
Obviously, this isn't an absolute, as the 739ER is doing just fine. The 779 will likely be a winner as well.

But yes, the likes of the 764ER, 753, A346, 748i were total dogs in terms of sales... but they perform well.

There are factors beyond just being a double-stretch (and therefore less optimized for wing/engines/etc), usually timing and more-optimized competition. It's not a simple answer.


Ahhh. So its not like double-stretches are as technologically-inefficient as a shrink, then?
 
flipdewaf
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Re: question, may be a touch technical...

Sat Apr 07, 2018 6:32 am

LAX772LR wrote:
Obviously, this isn't an absolute, as the 739ER is doing just fine. The 779 will likely be a winner as well.

But yes, the likes of the 764ER, 753, A346, 748i were total dogs in terms of sales... but they perform well.

There are factors beyond just being a double-stretch (and therefore less optimized for wing/engines/etc), usually timing and more-optimized competition. It's not a simple answer.

I was just about to say the same, the engineering reasons for double stretches not working seem less important than the timing reasons. The double stretch seems to be used when an aircraft has gained performance over its life and has a bit in the bank with which to stretch and has also a new competitor on the block which means a cheap, quick to market option is viable.

Those double stretches mentioned might now have been stellar sellers but the customers seem to be hanging on to them.

Fred


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GalaxyFlyer
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Re: Double stretches of an aircraft, why don’t they work?

Sat Apr 07, 2018 10:46 pm

Perhaps, they run out of wing—the ever-increasing weights start becoming too much for the wing and performance becomes a problem.

GF
 
jupiter2
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Re: question, may be a touch technical...

Sun Apr 08, 2018 9:39 am

LAX772LR wrote:
Obviously, this isn't an absolute, as the 739ER is doing just fine. The 779 will likely be a winner as well.

But yes, the likes of the 764ER, 753, A346, 748i were total dogs in terms of sales... but they perform well.

There are factors beyond just being a double-stretch (and therefore less optimized for wing/engines/etc), usually timing and more-optimized competition. It's not a simple answer.


Neither the 753 or the 748i are double stretches. The 737 has been built at 7(?) different lengths, the DC8 had 3 different lengths. Some of the aircraft mentioned were poorly timed, some came up against a better competitor and the 748i has sold poorly, the freighter is doing ok and will be around a while yet.
 
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LAX772LR
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Re: question, may be a touch technical...

Sun Apr 08, 2018 7:31 pm

jupiter2 wrote:
Neither the 753 or the 748i are double stretches.

Incorrect on the 757

You're forgetting about the 757-100 (7N7-100); which wasn't delivered, but did form the baseline for the 757's design.
The 752, despite being the first (and for a long time, only) to market, was a stretch of 751 platform, the latter which continued to be offered after the model's 1978 design freeze... making the 753 a double-stretch on an engineering basis.

The 763 escaped this fate because the 761 variant was dropped in 1978 after the first orders but before design freeze, with engineering efforts modified to make the 762 the baseline platform for the 767.

As for the 747, I keep forgetting that the 748i isn't a double-stretch... just junk that nobody wants. :razz:
Alas, it still suffers from the same market issues as the double-stretches: too little, too late, and poor timing against more optimized competition.


jupiter2 wrote:
and the 748i has sold poorly, the freighter is doing ok and will be around a while yet.

The context spoken was obbbbbbbbbbbbviously in reference to pax variants, as model selection in freighters (where the likes of MD11s and 744s are still prized) is quite different.
I myself, suspect a more prosaic motive... ~Thranduil
 
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Re: question, may be a touch technical...

Mon Apr 09, 2018 12:47 am

jupiter2 wrote:
LAX772LR wrote:
The 737 has been built at 7(?) different lengths, the DC8 had 3 different lengths. Some of the aircraft mentioned were poorly timed, some came up against a better competitor and the 748i has sold poorly, the freighter is doing ok and will be around a while yet.

Hmm, the 737 is a good one, I count 9 total (11 if you want to be super pedantic):

100
200
300/700 (same fuse, different tail feathers)
400
500/600 (IIRC a foot longer than the 200, 600 has same fuse but longer tail feathers)
800/max8
900/900ER/max9
max-7 (slightly longer than 700)
max10 (eventually)

LAX772LR wrote:
jupiter2 wrote:
Neither the 753 or the 748i are double stretches.

Incorrect on the 757

You're forgetting about the 757-100 (7N7-100); which wasn't delivered, but did form the baseline for the 757's design.
The 752, despite being the first (and for a long time, only) to market, was a stretch of 751 platform, the latter which continued to be offered after the model's 1978 design freeze... making the 753 a double-stretch on an engineering basis.

The 763 escaped this fate because the 761 variant was dropped in 1978 after the first orders but before design freeze, with engineering efforts modified to make the 762 the baseline platform for the 767.


Though Boeing did kick around the idea of the 751, the design was optimized around 180 seats by Eastern and BA's request, so I'd argue that the 752 was the baseline and the 751 a proposed shrink, a bit like the 343 was the optimized one and the 342 a shrink. Either way, the 753 wasn't so much a bad design as a victim of timing. Had they brought it to market in the early-90s, they probably would have sold a couple hundred.

viewtopic.php?t=338603
viewtopic.php?t=424213

Regarding double stretches being failures, I don't think there's anything inherently wrong with the idea, it's just the implementation. Let's think of some examples:
DC-8-61/63: pretty successful in their own right
707-300/400/300B/C: smashing success (yes, the 300 was a double-stretch, arguably a triple if you count the 720 as a "707." The baseline short 100 was only built for Qantas, PA/AA got theirs stretched by 10 feet, then the 300s were a further stretch, ref: http://www.707.adastron.com/qantas/138-length.htm)
A346: too heavy/stretch too far, too many compromises vs the optimized 343, hence the relative advantage of the 777 at the longer length
764: too late to market, wing too small, A332 had better payload/range
78J: looking ok so far
779: too early to call
733: huge success

The only thing consistent with these examples is whether or not the double-stretch was well executed as an aircraft in its own right.
 
jupiter2
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Re: question, may be a touch technical...

Mon Apr 09, 2018 7:25 am

LAX772LR wrote:
jupiter2 wrote:
Neither the 753 or the 748i are double stretches.

Incorrect on the 757

You're forgetting about the 757-100 (7N7-100); which wasn't delivered, but did form the baseline for the 757's design.
The 752, despite being the first (and for a long time, only) to market, was a stretch of 751 platform, the latter which continued to be offered after the model's 1978 design freeze... making the 753 a double-stretch on an engineering basis.

The 763 escaped this fate because the 761 variant was dropped in 1978 after the first orders but before design freeze, with engineering efforts modified to make the 762 the baseline platform for the 767.

As for the 747, I keep forgetting that the 748i isn't a double-stretch... just junk that nobody wants. :razz:
Alas, it still suffers from the same market issues as the double-stretches: too little, too late, and poor timing against more optimized competition.


jupiter2 wrote:
and the 748i has sold poorly, the freighter is doing ok and will be around a while yet.

The context spoken was obbbbbbbbbbbbviously in reference to pax variants, as model selection in freighters (where the likes of MD11s and 744s are still prized) is quite different.


Guess if you want to include paper planes, then sure the 753 is a double stretch.

Must've missed the memo that the thread is only about passenger aircraft, but then again, if the aircraft is the same length for the pax and freighter versions, I just don't see what your point is :sarcastic: It's not as though any manufacturer has built a stretched version of an aircraft just to be a freighter, at least not in the civil market.

There is another well represented multiple stretch in the DC-9 series of course. Strangely the Soviets/Russians/Ukrainians didn't stretch many, if any, of their designs.
 
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LAX772LR
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Re: question, may be a touch technical...

Mon Apr 09, 2018 7:52 am

jupiter2 wrote:
Guess if you want to include paper planes, then sure the 753 is a double stretch.

lack of sells doesn't change the fact that the design freeze was based on a variant smaller than the -200.


jupiter2 wrote:
I just don't see what your point is :sarcastic:

Even after it was explained? ...hmm, not sure how to simplify it even further.
I myself, suspect a more prosaic motive... ~Thranduil
 
jupiter2
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Re: question, may be a touch technical...

Mon Apr 09, 2018 9:29 am

LAX772LR wrote:
jupiter2 wrote:
Guess if you want to include paper planes, then sure the 753 is a double stretch.

lack of sells doesn't change the fact that the design freeze was based on a variant smaller than the -200.


jupiter2 wrote:
I just don't see what your point is :sarcastic:

Even after it was explained? ...hmm, not sure how to simplify it even further.


Why are freighters different ? Are they not based off the same commercial designs, same lengths, same wings, etc. Not exactly sure what you were supposed to have explained anyway, is it that you are just pissed that a model can continue to exist by freighter sales alone. Not sure where the problem is, but shan't bother anymore.
 
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Re: question, may be a touch technical...

Mon Apr 09, 2018 1:03 pm

LAX772LR wrote:
Even after it was explained? ...hmm, not sure how to simplify it even further.



LAX772LR wrote:
The context spoken was obbbbbbbbbbbbviously in reference to pax variants, as model selection in freighters (where the likes of MD11s and 744s are still prized) is quite different.


obbbbbbbbbbbbviously isn't an explanation. You can't simplify it any further, because you haven't given a reader any reference as to why it was so obbbbbbbbbbbbviously restricted to pax variants only.
The fact that you aren't the OP that restricted the replies to pax only further muddies your point.
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flyingclrs727
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Re: Double stretches of an aircraft, why don’t they work?

Mon Apr 09, 2018 5:21 pm

Well the 737 has been stretched six times and will be stretched a seventh time.
Last edited by flyingclrs727 on Mon Apr 09, 2018 5:27 pm, edited 1 time in total.
 
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LAX772LR
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Re: question, may be a touch technical...

Tue Apr 10, 2018 5:12 am

jupiter2 wrote:
Why are freighters different ?

Because you're dealing with different weights, different performance, different depreciation scales, sometimes different components, sometimes different regulations, etc etc etc.

Or, for an even simpler approach, just look around: the likes of AB6s and M11s have been borderline worthless on the pax market for nearly two decades, yet were heavily sought for freight. In the freight market, smaller base models are typically of greater value than stretches of any type; the exact opposite of pax.

Plenty of others, but that should at least give you the idea.



SAAFNAV wrote:
obbbbbbbbbbbbviously isn't an explanation. You can't simplify it any further, because you haven't given a reader any reference as to why it was so obbbbbbbbbbbbviously restricted to pax variants only.

So apparently you were too stunted by consonant repetition to finish the rest of the sentence? That wasn't asking much.
I myself, suspect a more prosaic motive... ~Thranduil
 
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Re: question, may be a touch technical...

Tue Apr 10, 2018 6:22 pm

jupiter2 wrote:
LAX772LR wrote:
Obviously, this isn't an absolute, as the 739ER is doing just fine. The 779 will likely be a winner as well.

But yes, the likes of the 764ER, 753, A346, 748i were total dogs in terms of sales... but they perform well.

There are factors beyond just being a double-stretch (and therefore less optimized for wing/engines/etc), usually timing and more-optimized competition. It's not a simple answer.


Neither the 753 or the 748i are double stretches. The 737 has been built at 7(?) different lengths, the DC8 had 3 different lengths. Some of the aircraft mentioned were poorly timed, some came up against a better competitor and the 748i has sold poorly, the freighter is doing ok and will be around a while yet.

I count six lengths for the 737:

- 100
- 200/500/600
- 300/700
- 400/800
- 900
- Max10 (and that is still just a paper plane, at this point)

Anything I'm missing?
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novarupta
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Re: Double stretches of an aircraft, why don’t they work?

Tue Apr 10, 2018 8:32 pm

AA777223 wrote:
jupiter2 wrote:
LAX772LR wrote:
Obviously, this isn't an absolute, as the 739ER is doing just fine. The 779 will likely be a winner as well.

But yes, the likes of the 764ER, 753, A346, 748i were total dogs in terms of sales... but they perform well.

There are factors beyond just being a double-stretch (and therefore less optimized for wing/engines/etc), usually timing and more-optimized competition. It's not a simple answer.


Neither the 753 or the 748i are double stretches. The 737 has been built at 7(?) different lengths, the DC8 had 3 different lengths. Some of the aircraft mentioned were poorly timed, some came up against a better competitor and the 748i has sold poorly, the freighter is doing ok and will be around a while yet.

I count six lengths for the 737:

- 100
- 200/500/600
- 300/700
- 400/800
- 900
- Max10 (and that is still just a paper plane, at this point)

Anything I'm missing?


The 737-800 is a slight stretch over the 737-400...they’re not the same length.


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Stitch
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Re: Double stretches of an aircraft, why don’t they work?

Tue Apr 10, 2018 10:39 pm

And the MAX-7 is around 2 meters longer than the -300 / -700.
 
LH707330
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Re: Double stretches of an aircraft, why don’t they work?

Wed Apr 11, 2018 12:00 am

The 200 is also about a foot shorter than the 500, which gives us 8 lengths, 9 with the 10, and up to 12 if you count LOA and not just fuselage length.

100
200
300/700 (same fuse, different tail feathers)
400
500/600 (IIRC a foot longer than the 200, 600 has same fuse but longer tail feathers)
800/max8
900/900ER/max9
max-7 (slightly longer than 700)
max10 (eventually)
 
seat1a
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Re: Double stretches of an aircraft, why don’t they work?

Wed Apr 11, 2018 3:31 am

What about the DC-8? How many stretches were there?
 
LH707330
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Re: Double stretches of an aircraft, why don’t they work?

Wed Apr 11, 2018 4:30 am

seat1a wrote:
What about the DC-8? How many stretches were there?

2. the base versions 10-50 were 150 feet, the 62 was a slight stretch to 158, and the 61/63 were 187.
 
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TWA772LR
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Re: Double stretches of an aircraft, why don’t they work?

Wed Apr 11, 2018 4:44 am

If you think about it, the 737 has had 7 stretches.
100<200<300<400<7MAX<800<900<10
Not including the 500, 600, or 700 because those are technically shrinks.

And then the DC9 with 6 stretches:
10<30<50<80<81<82<90

A340 with 3
200<300<500<600

And the 777 with 3
200<8<300<9
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novarupta
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Double stretches of an aircraft, why don’t they work?

Wed Apr 11, 2018 5:06 am

TWA772LR wrote:
If you think about it, the 737 has had 7 stretches.
100<200<300<400<7MAX<800<900<10
Not including the 500, 600, or 700 because those are technically shrinks.

And then the DC9 with 6 stretches:
10<30<50<80<81<82<90

A340 with 3
200<300<500<600

And the 777 with 3
200<8<300<9


Regarding the DC-9 series/descendants, with the exception of the MD-87, all the MD80s (-81,82,83 & 88) share the same length, so you can’t list them as separate. A more accurate number would be 5: DC-9-30, -40, -50, -80 (MD80) and MD90. The MD-87 shares a length with the DC-9-50 (albeit with different proportions forward and aft of the wing), hence I didn’t count it as a “stretch” (similarly for the MD-95/717).

Also the 737-700 isn’t a shrink in the truest sense of the word (shares a fuselage with the 737-300, and isn’t a shortened 737-800, like what the A319 is to the A320)


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LH707330
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Re: Double stretches of an aircraft, why don’t they work?

Wed Apr 11, 2018 6:32 pm

TWA772LR wrote:
A340 with 3
200<300<500<600

The 342 is a shrink of the baseline 300, they were planned as a two-member family with the 200 as a payload/range trade.
 
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keesje
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Re: question, may be a touch technical...

Fri Apr 13, 2018 2:30 pm

LAX772LR wrote:
The 779 will likely be a winner as well.


I too hope so, 30-40 Sales of the last 3-4 yrs, while economies / airlines are booming. I hope Emirates doesn't catch a cold. http://money.cnn.com/2017/05/11/investing/emirates-airline-profit-slump-trump/index.html
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LAX772LR
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Re: question, may be a touch technical...

Fri Apr 13, 2018 3:14 pm

keesje wrote:
LAX772LR wrote:
The 779 will likely be a winner as well.

I too hope so, 30-40 Sales of the last 3-4 yrs, while economies / airlines are booming.

But like most alarmists on that front, you're also completely disregarding that 1) the replacement cycle it's aimed for is nowhere near in full (ordering) swing and 2) the aircrafts' capabilities are still not completely defined, and with good reason by Boeing.

A half-decade from now, when the first 77Ws are approaching an age when "normal" airlines will likely want to start thinking about divesting them? THEN it'd be reasonable to worry about slow sales of this aircraft. Not now.
I myself, suspect a more prosaic motive... ~Thranduil

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