jashah
Topic Author
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Joined: Thu May 04, 2006 1:36 pm

737-900 vs 900ER

Tue Aug 29, 2017 3:51 am

The performance limitations of the 737-900 (limited climb, high Vref on landing) have been discussed here before. I read in passing on another forum that the 900ER does not suffer as badly from these limitations. Does anyone know if this is true and if it is can you explain how this was accomplished?

Thanks
 
FlyHossD
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Re: 737-900 vs 900ER

Tue Aug 29, 2017 7:21 am

Though it's been a few years since I flew them, as I recall, the biggest operational difference was in the structural operating weights. For example, and without looking it up, the max landing weight for the -900 was 147K and for the -900ER was 10K heavier at 157K. It seemed to me that we often were limited by the max landing weight in both the -900 and occasionally by the original max landing weight of the -800 (144K which was increased to 146.3K(?)).

There were other differences, too*, but essentially the -900ER could operate at substantially heavier weights due to the increased structural limits and that allowed for more payload and/or more fuel in a typical flight.

*like the two additional exit doors behind the wing.
My statements do not represent my former employer or my current employer and are my opinions only.
 
Chaostheory
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Re: 737-900 vs 900ER

Tue Aug 29, 2017 10:16 am

jashah wrote:
The performance limitations of the 737-900 (limited climb, high Vref on landing) have been discussed here before. I read in passing on another forum that the 900ER does not suffer as badly from these limitations. Does anyone know if this is true and if it is can you explain how this was accomplished?

Thanks


You're making the same mistake as many by conflating takeoff and climb performance. They are not the same. I won't rehash the numerous takeoff performance limitations as they've been covered many times. Once you get her arse off the asphalt, the -900/er doesn't have any issues with climbing. Going back to a BBJ3
procurement evaluation we did many years ago, the -900/er will happily climb at 80t+ until you hit isa15.
 
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keesje
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Re: 737-900 vs 900ER

Thu Sep 07, 2017 9:36 am

The 900ER weigh a lot more than the -900 amongst because of the aft wing exit door, flat bulkhead.

The biggest limitation of the -900 is the exit door limited 180 passengers. In real 2 class configuration that wasn't really a problem. Single class it is an unwelcome operational limitation.

This one has 192 seats but can take 178 passengers. https://www.seatguru.com/airlines/KLM/KLM_Boeing_737-900.php
"Never mistake motion for action." Ernest Hemingway
 
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Polot
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Re: 737-900 vs 900ER

Thu Sep 07, 2017 12:36 pm

keesje wrote:
The biggest limitation of the -900 is the exit door limited 180 passengers. In real 2 class configuration that wasn't really a problem. Single class it is an unwelcome operational limitation.

The 739A exit limit is 189 seats, same as the 738. Hence why as you said it was useless for single class operators as you can easily put 189 seats in the 738 without even having to turn to 28" pitch.
 
FrmrKSEngr
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Re: 737-900 vs 900ER

Sat Sep 09, 2017 4:31 am

The -900 was originally designed to give more leg room for Alaska over the -800 for the same load. Contiental also appreciated the lenght (the days before the majors started cramming in as many people as they could into the tube). The IT operators liked the extra length to cram in more people, but were disappointed in the field performance due to the rotation angle reduction from the -800. The IT operators wanted to get back the -800 take-off length on the -900. This was a design consideration when we started designing the -900ER. To get back the field performance while also increasing the MGW, Boeing redesigned the leading devices, made other changes to the wing structure and rescheduled the flaps. The first major change to the 737NG wing. The wing guys had it easy as we in fuselage were designing the minor models from -700, -800, -600, -701, -702 and -900. Up to that point wing changes were limited to three wing box configurations: -600, -700 and -800/701/702/900.
 
Newbiepilot
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Re: 737-900 vs 900ER

Sat Sep 09, 2017 11:39 am

FrmrKSEngr wrote:
The -900 was originally designed to give more leg room for Alaska over the -800 for the same load. Contiental also appreciated the lenght (the days before the majors started cramming in as many people as they could into the tube). The IT operators liked the extra length to cram in more people, but were disappointed in the field performance due to the rotation angle reduction from the -800. The IT operators wanted to get back the -800 take-off length on the -900. This was a design consideration when we started designing the -900ER. To get back the field performance while also increasing the MGW, Boeing redesigned the leading devices, made other changes to the wing structure and rescheduled the flaps. The first major change to the 737NG wing. The wing guys had it easy as we in fuselage were designing the minor models from -700, -800, -600, -701, -702 and -900. Up to that point wing changes were limited to three wing box configurations: -600, -700 and -800/701/702/900.


Alaska didn't order the 737-800 and eventually 737-900ER because 737-900 field performance was bad. Field performance was always known. AS bought the 737-700 for SNA, BUR and airports in Alaska that needed field performance. The 737-900 was for trunk routes on the west coast and transcons.

What made Alaska order the 737-800 was in 2004, the FAA increased passenger weights in weight and balance calculations from 170 summer / 175 winter lbs to 190/195 after the Air Midwest crash in Charlotte. The increased passenger weights effectively shortened the range of all planes. This prohibited Alaska from flying SEA-BOS and SEA-Florida with the 737-900 with a full load of passengers. They were expanding to the east coast back then and needed a plane that could fly nonstop. The initial 737-900s could, but once the passenger weigths increased, the airplane couldn't take a full load of passengers. It was restricted to closer to the 737-800 capacity (15 to 20 seats frequently) so Alaska went ordered the 737-800 and used it as the backbone of the transcon fleet and Hawaii until eventually ordering the 737-900ER. The higher MTOW of the 737-900ER allowed more fuel to give the plane more range.

The design changes you are referring to had two benefits. They increased MTOW of the plane for more range. The improvements also shortened takeoff distance for the same weight.
 
FrmrKSEngr
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Re: 737-900 vs 900ER

Sat Sep 09, 2017 11:31 pm

I can only relate what I remember designing fuselage structures in Wichita on the 737NG and working the the fuselage preliminary design for the -900ER and IGW.

The initial -900 was exit limited to the same passenger load as the -800. So the only reason to build the -900 was to get max -800 pax load with the normal seat pitch of the majors at the time. I thought the initial request came from Alaska, but I know Continental took quite a few.

in the -900 ER initial design meetings between Renton and Wichita, the IT operators desire for essentially -800 all around performance with higher passenger numbers were the scope of the discussions. Initially, besides Southwest, most 737-NGs were going to Eurpoe. Customers I remember included Maersk, Hapag Lloyd (I believe the first -800), KLM, TAV, Royal Air Moroc, SAS. American and Delta were relative late comers to the order book, USAIR & United went Airbus and TWA went MD-95/717 and were also looking at A320s.

I left BCA in December 2001 due to the down turn after 9-11 before we started detail design of the -900ER, and did not keep up with the program after that.
 
FlyHossD
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Re: 737-900 vs 900ER

Sun Sep 10, 2017 3:57 am

FrmrKSEngr wrote:
...Initially, besides Southwest, most 737-NGs were going to Eurpoe. Customers I remember included Maersk, Hapag Lloyd (I believe the first -800), KLM, TAV, Royal Air Moroc, SAS. American and Delta were relative late comers to the order book, USAIR & United went Airbus and TWA went MD-95/717 and were also looking at A320s.


CO - Continental - was another early North American 737NG operator.
My statements do not represent my former employer or my current employer and are my opinions only.
 
benbeny
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Re: 737-900 vs 900ER

Sun Sep 10, 2017 12:58 pm

How about it's braking performance? I heard more runway overrun than 737-800
 
FlyHossD
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Re: 737-900 vs 900ER

Sun Sep 10, 2017 3:55 pm

benbeny wrote:
How about it's braking performance? I heard more runway overrun than 737-800


Yes, the -900s and -900ERs need more runway than a -800 due to the higher weights and higher approach speeds. Having said that, the last few times through ORD - each in a -900ER - were landings on 7500' long runway 27R with what felt like normal braking.
My statements do not represent my former employer or my current employer and are my opinions only.
 
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Stitch
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Re: 737-900 vs 900ER

Mon Sep 11, 2017 1:11 am

keesje wrote:
The 900ER weigh a lot more than the -900 amongst because of the aft wing exit door, flat bulkhead.


The difference in OEM OEW between them is ~1700kg - about 4%. Not exactly "a lot".
 
FlyHossD
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Re: 737-900 vs 900ER

Mon Sep 11, 2017 2:50 pm

[photoid][/photoid]
Stitch wrote:
keesje wrote:
The 900ER weigh a lot more than the -900 amongst because of the aft wing exit door, flat bulkhead.


The difference in OEM OEW between them is ~1700kg - about 4%. Not exactly "a lot".


Is Operating Empty Weight the right standard to use here? I think max landing weight is a better point to judge from. IIRC, the max landing weight of the -900 is 147,300 pounds and it's 10,000 pounds greater for the -900ER (157,300) - a difference of 6 to 7 percent which is still not a huge difference.
My statements do not represent my former employer or my current employer and are my opinions only.
 
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Stitch
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Re: 737-900 vs 900ER

Mon Sep 11, 2017 3:59 pm

FlyHossD wrote:
Is Operating Empty Weight the right standard to use here?


Since we're talking structural weight, I believe it is.

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