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Are The 737 Wheels On The Outside In This Picture?  
User currently offlineSuseJ772 From United States of America, joined Aug 2005, 820 posts, RR: 1
Posted (6 years 3 weeks 6 days 15 hours ago) and read 11922 times:


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Photo © Gary Shephard - LightSketch Photography

When the main wheels on the 737 are retracted are they still exposed to the outside of the plane? I didn't think so, but the above picture sort of looks like it in both the -200 and the -300. If they aren't, what are the black circles under the body?


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User currently offlineKLASM83 From United States of America, joined Aug 2005, 631 posts, RR: 0
Reply 1, posted (6 years 3 weeks 6 days 15 hours ago) and read 11926 times:

It is a cool pic, is it not?  . As I remember, the 73's do not come with a MLG door, saving on weight, thus making it so that the tires make an aerodynamic seal with the fuselage. Hope that helps!


->Edited for spelling. And Grammar. This post talk gooder now.

[Edited 2008-09-24 12:24:59]


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User currently offlineLAxintl From United States of America, joined May 2000, 25719 posts, RR: 50
Reply 2, posted (6 years 3 weeks 6 days 15 hours ago) and read 11888 times:

The 737 does not have main gear bay doors.

discussed in these threads
http://www.airliners.net/aviation-forums/tech_ops/read.main/198556
http://www.airliners.net/aviation-forums/tech_ops/read.main/146495



From the desert to the sea, to all of Southern California
User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 3, posted (6 years 3 weeks 6 days 15 hours ago) and read 11896 times:



Quoting SuseJ772 (Thread starter):
When the main wheels on the 737 are retracted are they still exposed to the outside of the plane? I didn't think so, but the above picture sort of looks like it in both the -200 and the -300. If they aren't, what are the black circles under the body?

That would be the tires. They lie flush with the fuselage of the aircraft when retracted, and there is an aerodynamic "hubcap" in the middle of the outboard wheel to minimize drag. It saves on weight and landing gear system complexity. IIRC, there is even a piece of rubber trim inside the wheel well to keep the seal tight once the gear are retracted.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineSuseJ772 From United States of America, joined Aug 2005, 820 posts, RR: 1
Reply 4, posted (6 years 3 weeks 6 days 15 hours ago) and read 11889 times:

I found these pictures too and they all look like the wheels are exposed to the outside.


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Photo © Patric Borg
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Photo © Nigel Pengelly




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Photo © Kas Van Zonneveld
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Photo © Galen Burrows




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Photo © K.L.Yim
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Photo © Paul Kanagie



Quoting KLASM83 (Reply 1):
thus making it so that the tires make an aerodynamic seal with the fuselage

This would seem to be real prone to problems.

I can't believe I never knew this. I guess you learn something new everyday.



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User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 5, posted (6 years 3 weeks 6 days 15 hours ago) and read 11852 times:



Quoting SuseJ772 (Reply 4):
This would seem to be real prone to problems.

I can't believe I never knew this. I guess you learn something new everyday.

Less prone to trouble than an additional hydraulically actuated door that has to be closed when the gear is both retracted and extended  Smile (not to mention the weight of the additional aluminum in the door, additional hydraulic tubing, electronic sequencers, etc. etc.)



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineDfwRevolution From United States of America, joined Jan 2010, 984 posts, RR: 51
Reply 6, posted (6 years 3 weeks 6 days 15 hours ago) and read 11823 times:



Quoting SuseJ772 (Reply 4):
I can't believe I never knew this. I guess you learn something new everyday.

Same design philosophy is used on the E170/E190 series


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Photo © Gabriel Widyna



User currently offlineSeptember11 From United States of America, joined May 2004, 3623 posts, RR: 21
Reply 7, posted (6 years 3 weeks 6 days 15 hours ago) and read 11743 times:

Even better pictures ...


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Photo © Konstantin von Wedelstaedt
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Photo © Christian Mueller



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Photo © Paulo Herren




Airliners.net of the Future
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9665 posts, RR: 52
Reply 8, posted (6 years 3 weeks 6 days 15 hours ago) and read 11629 times:



Quoting KLASM83 (Reply 1):
It is a cool pic, is it not? . As I remember, the 73's do not come with a MLG door, saving on weight, thus making it so that the tires make an aerodynamic seal with the fuselage. Hope that helps!

Just a correction, but there are main landing gear doors. They just don't cover the tire and wheel. The main landing gear doors cover the strut as it moves into the wing/body/wing to body fairing.

Quoting KELPkid (Reply 5):
(not to mention the weight of the additional aluminum in the door, additional hydraulic tubing, electronic sequencers, etc. etc.)

You overestimate the 737. There aren't electronic sequencers. It's manually driven by cables, solenoids and a transfer valve.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25626 posts, RR: 22
Reply 9, posted (6 years 3 weeks 6 days 15 hours ago) and read 11631 times:



Quoting DfwRevolution (Reply 6):
Same design philosophy is used on the E170/E190 series

Also the CRJ.


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Photo © Pierre Cester
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Photo © Javier Gonzalez - Iberian Spotters



User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 10, posted (6 years 3 weeks 6 days 15 hours ago) and read 11578 times:



Quoting SuseJ772 (Thread starter):

This topic is well covered and comes up all the time. Along with the B737 there are several other jets that have wheels exposed.



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User currently offline113312 From United States of America, joined Apr 2005, 573 posts, RR: 1
Reply 11, posted (6 years 3 weeks 6 days 14 hours ago) and read 11513 times:

When the B737 first went into service, it had an inflatable skirt to seal the main gear wells after the gear was retracted. It was later decided that this was too complex and not worth the small drag advantage. From then on, the 737 series has had a simple exposed wheel with a smooth hubcap on the outside wheel.

User currently offlineSpeedBirdA380 From United Kingdom, joined Jul 2008, 539 posts, RR: 1
Reply 12, posted (6 years 3 weeks 6 days 14 hours ago) and read 11461 times:



Quoting KELPkid (Reply 3):
It saves on weight and landing gear system complexity.

Why is it only a few aircraft that do this and not all of them?


User currently offlineRwessel From United States of America, joined Jan 2007, 2368 posts, RR: 2
Reply 13, posted (6 years 3 weeks 6 days 13 hours ago) and read 11267 times:
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Quoting SuseJ772 (Reply 4):
This would seem to be real prone to problems.

What trouble? It's a bit of rubber around the gear well to help smooth out the airflow.

You can see it at the bottom edge of this:


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Photo © Michael Carter



Quoting SpeedBirdA380 (Reply 12):
Why is it only a few aircraft that do this and not all of them?

A "real" gear door will result in better aerodynamics. But it will be heavier and more complex. For a short range aircraft a small cruise aerodynamic penalty may be outweigh by the extra weight and complexity.

OTOH, given that the range of the 737 has increased rather significantly since the early days, I'd not be at all surprised to see its replacement have "real" gear doors.


User currently offlineUnited787 From United States of America, joined May 2005, 2728 posts, RR: 2
Reply 14, posted (6 years 3 weeks 6 days 13 hours ago) and read 11174 times:



Quoting SuseJ772 (Reply 4):
I can't believe I never knew this. I guess you learn something new everyday.

I saw the same pic and wondered why I never knew that either.

Although the more I look at the picture, the odder it looks...gives another meaning to hanging dirty...too exposed...but some underpants on that thing for pete's sake...


User currently offlineDocLightning From United States of America, joined Nov 2005, 19924 posts, RR: 59
Reply 15, posted (6 years 3 weeks 6 days 12 hours ago) and read 11036 times:



Quoting United787 (Reply 14):

Although the more I look at the picture, the odder it looks...gives another meaning to hanging dirty...too exposed...but some underpants on that thing for pete's sake...

And so being endowed with the rather filthy and yet amusing organ that occupies my skull, I immediately flashed to mental images of various retractable...

...never mind.  angel   duck 


User currently offlineAV8orWALK From United States of America, joined Nov 2006, 186 posts, RR: 0
Reply 16, posted (6 years 3 weeks 6 days 11 hours ago) and read 10887 times:

I honestly can't believe that I've looked at THOUSANDS of pictures of 737's on a.net, let alone worked on every a/c in WN's fleet when I was a FA 6 years ago, and failed to realize those were the tires themselves, not a bay door.

Wow, that's the one thing I've learned today!


Cheers!
Drew MCO



The safest place to be in an airplane crash is on the ground.
User currently offlinePilotboi From United States of America, joined Sep 2007, 2366 posts, RR: 9
Reply 17, posted (6 years 3 weeks 6 days 11 hours ago) and read 10799 times:



Quoting SuseJ772 (Reply 4):
This would seem to be real prone to problems.

Really? So why is the 737 the most popular commercial aircraft in the world?  Silly


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5873 posts, RR: 11
Reply 18, posted (6 years 3 weeks 6 days 7 hours ago) and read 10635 times:



Quoting AV8orWALK (Reply 16):
let alone worked on every a/c in WN's fleet

Totally thought you were about to say you'd been a WN mechanic and never noticed a lack of doors.
Glad that's not the case!!!!! Lol.

Quoting Pilotboi (Reply 17):
Really? So why is the 737 the most popular commercial aircraft in the world?

Calm down- the most popular aircraft in the world isn't without design flaw (trust me, I work on them). But the gear door thing is really a non-issue.

AND, folks, it makes things WAY more convenient and even SAFE when you're servicing things in the wheel well. On other aircraft, you have to drop the doors to service those systems. I've had coworkers (in the past) been given concussions when they didn't hear the warning that the doors were about to drop open. No exaggeration.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 19, posted (6 years 3 weeks 6 days 1 hour ago) and read 10473 times:

http://www.b737.org.uk/images/wheelwellboth.jpg
Lower view.
The Hub cap present helps reduce drag by providing a smoother surface.
The b737 has got Three Doors per MLG....Inner/outer & Middle.These doors are attached to the strut directly or via linkage depending on the door & move with it.

regds
MEL



Think of the brighter side!
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 20, posted (6 years 3 weeks 5 days 19 hours ago) and read 10375 times:

From what I remember the drag-penalty of the gears being exposed was actually less than the weight-penalty of having doors that covered the whole landing gear.


Blackbird


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 21, posted (6 years 3 weeks 5 days 18 hours ago) and read 10348 times:



Quoting Blackbird (Reply 20):
From what I remember the drag-penalty of the gears being exposed was actually less than the weight-penalty of having doors that covered the whole landing gear.

Any idea,what caused this......I thought Weight saving & simple mechanism overruled complicative sequencing & added weight.

regds
MEL



Think of the brighter side!
User currently offlineG4Doc2004 From United States of America, joined Feb 2004, 123 posts, RR: 0
Reply 22, posted (6 years 3 weeks 5 days 15 hours ago) and read 10280 times:

The fastest business jet flying right now is the Citation X (Mach .92) and it's wheels are exposed a-la the B-737 as well. When retracted, the edge of the tire sits just below the fairing.


"Failure to prepare is preparing to fail"--Benjamin Franklin
User currently offlineRedFlyer From United States of America, joined Feb 2005, 4349 posts, RR: 28
Reply 23, posted (6 years 3 weeks 5 days 15 hours ago) and read 10266 times:



Quoting HAWK21M (Reply 19):

Great pic, Hawk!

RoseFlyer - look at the photo in Hawk's post. I think you were right on the issue of extending the wheel well on the thread in CivAv on the GTF. While there might be room for a gain of a couple of inches, I don't think it would be enough to overcome the issues faced by a longer LG strut because of the keel structure.

Regards



My other home is a Piper Cherokee 180C
User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 24, posted (6 years 3 weeks 5 days 14 hours ago) and read 10247 times:

Didn't hear brush seals mentioned.

I know there is a specific purpose (hence the name brush SEAL) but what exactly? I first noticed it working for a regional on the CRJs. I asked a mech and he gave me a pretty detailed response but this was 2 years ago so I don't really remember Big grin .



What gets measured gets done.
25 Starlionblue : Bigger aircraft have more space for a door and the related mechanism. Also, widebodies have big bogies, meaning it's not a simple round shape in a ro
26 KELPkid : Ahem....
27 Pilotpip : The Global Express has exposed mains as well. BTW, on Embraers the brushes can't be deferred.
28 HAWK21M : Whats the reason stated? On the B737,there is a tolerance to the amount of wear permitted on the rubber seals. regds MEL
29 Post contains images 2H4 : Some airplanes leave their main gear hanging out in the wind even after they're retracted: 2H4
30 Rwessel : True, although I'm almost tempted to make a distinction based on why you move the gear. In those cases it's not for drag reduction in flight, rather
31 2H4 : And to get out of the way of the radar, sure. I was just pointing out some fun and quirky exceptions to the usual objective of retractable landing ge
32 JetMech : This is what happens when you do land on water with the wheels extended ! Regards, JetMech
33 Post contains links and images 2H4 : That guy just needs more practice. Here's what you can do if you've got proper technique: 2H4
34 JetMech : True. I bet the plane was not the only thing hung out to dry after that incident! I remember those pictures! I think there was great debate at the ti
35 2H4 : No, I don't even recall that discussion. I know what those airplanes are doing can be done, though, and I can't imagine someone would go to such Phot
36 JetMech : Fair enough. A little bit of Googling and Youtubing brought up this. Regards, JetMech
37 Don81603 : Holy ***!!! Talk about no room for error! This has to be a pucker factor of at least 250. Thanks for sharing though. .
38 KELPkid : Here's one for you all to consider (and I ask this innocently, since I'm a single-engine piston GA pilot, and darn near 100% of the time, we'd be able
39 HAWK21M : On the -NGs the "frangible fitting" will avoid that gear to retract.If its a tire burst,to protect the wheel well components. regds MEL
40 MD11Engineer : To elaborate, it is a thumbsize piece of pipe sticking outfrom the outer edge of each main wheel well, which is close at one end and with the other e
41 Mender : When the gear retracts the pressure to the retract actuator applies the brakes. This is known as retract braking. The frangible fitting only prevents
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