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?
KELPkid From United States of America, joined Nov 2005, 6833 posts, RR: 3
Reply 3, posted (7 years 7 months 1 week 4 days 9 hours ago) and read 15471 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 :-)
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 (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 :-)
RoseFlyer From United States of America, joined Feb 2004, 11166 posts, RR: 52
Reply 8, posted (7 years 7 months 1 week 4 days 8 hours ago) and read 15204 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!
113312 From United States of America, joined Apr 2005, 620 posts, RR: 1
Reply 11, posted (7 years 7 months 1 week 4 days 8 hours ago) and read 15088 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.
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.
AV8orWALK From United States of America, joined Nov 2006, 204 posts, RR: 0
Reply 16, posted (7 years 7 months 1 week 4 days 5 hours ago) and read 14462 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!
The safest place to be in an airplane crash is on the ground.
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.
HAWK21M From India, joined Jan 2001, 31875 posts, RR: 54
Reply 19, posted (7 years 7 months 1 week 3 days 18 hours ago) and read 14048 times:
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.
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.
FlyASAGuy2005 From United States of America, joined Sep 2007, 7440 posts, RR: 7
Reply 24, posted (7 years 7 months 1 week 3 days 7 hours ago) and read 13822 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 .
What gets measured gets done.
: 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