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User currently offlinebeeweel15 From United States of America, joined Nov 2003, 1741 posts, RR: 0
Posted (1 year 10 months 2 days 17 hours ago) and read 3655 times:

I dont know if this was discussed before but I will ask again. I have noticed that the US-NAVY Poseidon aircraft they feature raked wings like the 787 and the 78i plus there is a small antenna on the top of the tail which i have seen on several BBJ's. My question is are thsoe options available to the regular 737's or only for the military and BBJ's.

US-Navy Poseidon


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Photo © Alevik
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Photo © Mark Carlisle



BBJ (Notice the antennat on top of the tail)


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Photo © Dennis Muller
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Photo © Matteo Stella - Malpensa Spotters Group



7 replies: All unread, jump to last
 
User currently offlineBMI727 From United States of America, joined Feb 2009, 15719 posts, RR: 26
Reply 1, posted (1 year 10 months 2 days 16 hours ago) and read 3533 times:

Quoting beeweel15 (Thread starter):
I have noticed that the US-NAVY Poseidon aircraft they feature raked wings like the 787 and the 78i

As far as I know those are not available on the BBJ. With the new winglets coming, I don't think there's much reason why they would want them.

Quoting beeweel15 (Thread starter):
is a small antenna on the top of the tail which i have seen on several BBJ's.

That could probably be applied to commercial models. I want to say that it's a VHF antenna, which is unnecessary for commercial 737s.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 2, posted (1 year 10 months 2 days 14 hours ago) and read 3426 times:

Quoting beeweel15 (Thread starter):
My question is are thsoe options available to the regular 737's or only for the military and BBJ's.

For sufficient money, Boeing will engineer anything the customer wants That said, they're not currently available options so it's going to cost a lot. There are mission-specific reasons for the raked tips on the P-8 that don't apply to the general military or BBJ missions.

Quoting BMI727 (Reply 1):
That could probably be applied to commercial models. I want to say that it's a VHF antenna, which is unnecessary for commercial 737s.

I think you mean UHF...commercial 737's certainly need VHF.

Tom.


User currently offlineBMI727 From United States of America, joined Feb 2009, 15719 posts, RR: 26
Reply 3, posted (1 year 10 months 2 days 14 hours ago) and read 3374 times:

Quoting tdscanuck (Reply 2):
I think you mean UHF...commercial 737's certainly need VHF.

You're right, it's UHF.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9509 posts, RR: 52
Reply 4, posted (1 year 10 months 2 days 12 hours ago) and read 3269 times:

The raked wingtip extensions are on the 737 since the original winglets did not perform well in the P8A flight envelope. The P8A is designed for low altitude conditions, so it is required to handle icing, etc which doesn't work well with the existing aviation partners winglet.

Also the navy doesn't care much about wingspan, so the raked wingtips don't impact them as much since they don't have to fit in tight gates.

The navy is paying enough and getting the airplane so customized that they can get anything they want. The 737NGs for the Air Force have winglets.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineDocLightning From United States of America, joined Nov 2005, 19415 posts, RR: 58
Reply 5, posted (1 year 10 months 1 day 20 hours ago) and read 3085 times:

Quoting tdscanuck (Reply 2):
For sufficient money, Boeing will engineer anything the customer wants That said, they're not currently available options so it's going to cost a lot. There are mission-specific reasons for the raked tips on the P-8 that don't apply to the general military or BBJ missions.

Can you discuss those? I know that the increased span is the main drawback of raked tips (and the increased bending moment, but they seem to have solved that). Let's assume a BBJ customer doesn't care about span so much. Is there a barrier? Like not certified for civilian use or something?


User currently offlineRoseflyer From United States of America, joined Feb 2004, 9509 posts, RR: 52
Reply 6, posted (1 year 10 months 1 day 16 hours ago) and read 3035 times:

Quoting DocLightning (Reply 5):
Can you discuss those? I know that the increased span is the main drawback of raked tips (and the increased bending moment, but they seem to have solved that). Let's assume a BBJ customer doesn't care about span so much. Is there a barrier? Like not certified for civilian use or something?

The way the military works is that if a design is used jointly for commercial and military, then it can be used freely under typical export regulations. When a part is exclusively used on a military plane it often falls under ITAR Military Only export restrictions. Those regulations can be overcome but they make it very difficult to develop technology on the P8A and then move it to commercial operations. Usually technology goes the other way to help with red tape.

From what I have heard the winglet has no anti-ice which poses a problem for flights with ice build up. The normal 737 is not flying continuously in icing conditions so it isn’t much of a problem to have some extra drag on the winglet. However the P8A has to be able to continuously operate at low altitudes as a part of its mission since it isn’t necessarily cruising at altitutde. It has to have on location low altitude performance. From what I understand a raked wingtip does better for icing conditions.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 7, posted (1 year 10 months 1 day 12 hours ago) and read 2969 times:

Quoting DocLightning (Reply 5):
Can you discuss those?

Nope.

Quoting DocLightning (Reply 5):
I know that the increased span is the main drawback of raked tips (and the increased bending moment, but they seem to have solved that).

The P-8 carries external wing stores and has a bomb bay...they had to redo a ton of structure anyway. Tweaking it to handle the raked tips couldn't have been that big a deal once they "opened the box."

Quoting DocLightning (Reply 5):
Let's assume a BBJ customer doesn't care about span so much. Is there a barrier? Like not certified for civilian use or something?

It's not certified on the 737 for civilian use but that's just a testing thing. There's no technical reason you can't fit them or certify them, there just hasn't been any demand or business case to do it.

Tom.


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