kevin752
Topic Author
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737 Wheel Covers

Mon Apr 18, 2016 10:54 am

So this might be a stupid question but it seems that the 737 is the only type to have those wheel covers on the center landing gear does anyone know why they are there and why is it the only Boeing type to have that add on??

[Edited 2016-04-18 03:55:34]
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RRTrent
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RE: 737 Wheel Covers

Mon Apr 18, 2016 10:57 am

I think they are to help reduce drag from the airflow under the wheels as there are no main gear doors covering the wheels themselves
 
LSZH34
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RE: 737 Wheel Covers

Mon Apr 18, 2016 11:55 am

Quoting kevin752 (Thread starter):
why is it the only Boeing type to have that add on??

It's not only Boeing. The Embraers and Cseries also don't have gear doors and use this additional cover to reduce drag.
 
aviationaware
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RE: 737 Wheel Covers

Mon Apr 18, 2016 12:03 pm

The others have basically answered it already - many smaller airliners, most prominently the 737 series, don't have covers over their main landing gear to save weight. As uncovered landing gears produce additional drag, those gear bogeys are equipped with 'hubcaps' to minimized added drag - an endeavor that is completely unnecessary in larger aircraft because their gear is covered in flight, anyway.

The 737 is the only Boeing type to have this because all other types have vastly larger main bogeys that would make not covering them extremely impractical. Also, generally, the larger the bogey the smaller the weight penalty of a gear well door becomes.
 
starrymarkb
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RE: 737 Wheel Covers

Mon Apr 18, 2016 12:17 pm

I wonder if the A320 would have this too if it wasn't for double bogies being an option.
 
nikeherc
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RE: 737 Wheel Covers

Mon Apr 18, 2016 12:27 pm

The 737 also has an inflatable seal around the edge of the wheel well to fill the gap between the outer tire and the airframe. This further reduces drag.
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larshjort
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RE: 737 Wheel Covers

Mon Apr 18, 2016 1:25 pm

Quoting nikeherc (Reply 5):
Quoting starrymarkb (Reply 4):

The double boogies does not preclude the landing gear from being flush like on a 737. It is just a different design strategy. The 727 also have a single main wheel axle on each gear and it's gear is also fully enclosed when retracted.

/Lars
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FlyHossD
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RE: 737 Wheel Covers

Mon Apr 18, 2016 2:24 pm

Quoting nikeherc (Reply 5):
The 737 also has an inflatable seal around the edge of the wheel well to fill the gap between the outer tire and the airframe. This further reduces drag.

I don't remember that. Instead I remember a ring of brush-like fibers surrounding the main gear wheel well. That is, the ring isn't inflatable.
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nikeherc
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RE: 737 Wheel Covers

Mon Apr 18, 2016 2:55 pm

Quoting FlyHossD (Reply 7):
I don't remember that. Instead I remember a ring of brush-like fibers surrounding the main gear wheel well. That is, the ring isn't inflatable

Geez, my age is showing again. Apparently the original design had the inflatable seals, but that design was soon dropped for a simple rubber seal. The original design was considered to complicated. This is according to a UK 737 technical information site.
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kanban
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RE: 737 Wheel Covers

Mon Apr 18, 2016 4:04 pm

I believe the brush type have gone away in favor of segmented hard rubber seals..
 
AA737-823
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RE: 737 Wheel Covers

Mon Apr 18, 2016 5:17 pm

Quoting nikeherc (Reply 5):
The 737 also has an inflatable seal around the edge of the wheel well to fill the gap between the outer tire and the airframe. This further reduces drag.

Correction: HAD. I don't know ANY operator that still has these- we certainly didn't. What a nightmare!

Quoting FlyHossD (Reply 7):
don't remember that. Instead I remember a ring of brush-like fibers surrounding the main gear wheel well. That is, the ring isn't inflatable.

See above. And, now, below!

Quoting kanban (Reply 9):

I believe the brush type have gone away in favor of segmented hard rubber seals..

Indeed. Even the -200s I worked on had what we call Blade Seals.

Quoting RRTrent (Reply 1):
I think they are to help reduce drag from the airflow under the wheels as there are no main gear doors covering the wheels themselves

The hubcaps have also been proposed for the INBOARD wheels, to reduce noise generated by them during approach phase, as heard from the ground. This was most recently discussed at the time when the CFM56-7BE engine was fitted, the red beacon lens was streamlined, and the A/C Pack outlets were returned to their louvered state (ugh!), so maybe around 2008. But I have yet to see one with an extra pair of hubcaps. Don't know what happened there.
 
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rikkus67
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RE: 737 Wheel Covers

Mon Apr 18, 2016 6:13 pm

AC.WA.CP.DL.RW.CO.WG.WJ.WN.KI.FL.SK.ACL.UA.US.F9
 
kdhurst380
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RE: 737 Wheel Covers

Mon Apr 18, 2016 6:53 pm

Quoting starrymarkb (Reply 4):
I wonder if the A320 would have this too if it wasn't for double bogies being an option.

Very unlikely. The A320 has traditional gear doors so the gears themselves don't have to be aerodynamic whilst stowed.

The A320 family also has the option of brake fans which most airlines opt for, especially airlines with short turnarounds. It means you can do your landing roll on idle reverse and step on the wheel brakes, let them heat up a bit knowing that you can quickly cool them. Saves on fuel.

You may notice if you fly with a 737 operator like Ryanair who operate very short turnarounds, they tend to be fairly light on the wheel brakes and apply full reverse thrust, this is because the aircraft cannot self-cool its own wheel brakes.
 
trnswrld
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RE: 737 Wheel Covers

Tue Apr 19, 2016 4:56 pm

Obviously Boeing did their homework on this over and over again, but what kind of differences would there be aerodynamically if the 737 had main gear doors? I suppose with the wheel hub covers and a seal around the tire its gotta be pretty good as is otherwise they would have added doors long ago or had them right from the start. I cant imagine main landing gear door system adding much weight, but I suppose obviously it was more beneficial to not have doors. Intersting stuff for sure!

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