propilot83
Posts: 618
Joined: Sat Jan 27, 2001 2:41 am

Boeing 737 Landing Gear Doors?

Mon May 04, 2009 5:14 am

Does anyone know why Boeing designed the 737 without any landing gear doors for the main landing gear? Its kind of cool seeing the landing gear in its up position from the ground sometimes, and also doesnt it pose some type of safety hazard without having landing gear doors for the main gear on the 737? Doesnt the cold freezing atmosphere conditions at 25,000+ feet have any type of hazards for the main gear?
 
kleinsim
Posts: 21
Joined: Wed Jan 24, 2007 1:59 pm

RE: Boeing 737 Landing Gear Doors?

Mon May 04, 2009 5:35 am



Quoting Propilot83 (Thread starter):
Does anyone know why Boeing designed the 737 without any landing gear doors for the main landing gear?

a. Complexity issues and weight savings associated with the doors.

Quoting Propilot83 (Thread starter):
doesnt it pose some type of safety hazard without having landing gear doors for the main gear on the 737? Doesnt the cold freezing atmosphere conditions at 25,000+ feet have any type of hazards for the main gear?

b. Even if there were landing gear doors, the space where the wheels are is not heated. Hence on a four hour cruise the temperature inside the wheel well is the same as not having the door open. Hence there is no problem. I'm sure somewhat would have noticed one in 40+ years of service.  Smile



Kleinsim
 
speedracer1407
Posts: 330
Joined: Fri Dec 24, 2004 4:19 pm

RE: Boeing 737 Landing Gear Doors?

Mon May 04, 2009 6:10 am



Quoting Propilot83 (Thread starter):

Kleinsim has it right. MLG doors add complexity and weight. And they don't shield the tires from cold cruising temperatures anyway.

The 737 was designed in the 60s, and was initially intended for relatively short flights. At the time, whatever aerodynamic penalties for a door-less MLG were outweighed by the weight and added complexity MLG doors added to the overall design. Over the years, Boeing has had the opportunity to add MLG doors. But because even the relatively long-range newest 737s haven't incorporated this added complexity, it's safe to say that it doesn't buy operators enough efficiency to be worth while in cost, maintenance, or efficiency.
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: Boeing 737 Landing Gear Doors?

Mon May 04, 2009 3:21 pm



Quoting Propilot83 (Thread starter):
Doesnt the cold freezing atmosphere conditions at 25,000+ feet have any type of hazards for the main gear?

It is less a problem for the tires as it is for all the components in the wheel well. On a 737, real estate is tight, so most of the hydraulic and flight control systems components are in the wheel well. It is a very harsh environment for those components. Temperatures get as low as -65C. Air pressure obviously is only a few PSI. Worst of all, tire spray from runway deicing fluids and any other contamination on a runway gets kicked up in the wheel well which causes corrosion. It is very difficult on valves, pumps and other components. Tires, wheels, and landing gear are more structural components that don't have the tight tolerances and moving parts that make them as susceptible to those conditions.

Quoting Propilot83 (Thread starter):
Does anyone know why Boeing designed the 737 without any landing gear doors for the main landing gear?

Saves weight and reduces complexity. With the aerodynamic hub cap, there isn't that much of a drag penalty.

Quoting Speedracer1407 (Reply 2):

The 737 was designed in the 60s, and was initially intended for relatively short flights. At the time, whatever aerodynamic penalties for a door-less MLG were outweighed by the weight and added complexity MLG doors added to the overall design.

There have been options studied to reduce drag like partial wheel covers, but finding a way for them to fold out of the way when the gear is down is quite complex on a plane as low to the ground. The weight penalty is also a big hit that is hard to justify with drag reductions.
If you have never designed an airplane part before, let the real designers do the work!
 
propilot83
Posts: 618
Joined: Sat Jan 27, 2001 2:41 am

RE: Boeing 737 Landing Gear Doors?

Mon May 04, 2009 9:00 pm

Thanks for the info guys, WOW! I didnt think adding main landing gear doors would cause so much more weight and drag for the plane in flight. Yea, it also makes sense that the plane is real low to the ground to have landing gear doors for the main gear!
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Boeing 737 Landing Gear Doors?

Mon May 04, 2009 9:18 pm

The 737 originally had an inflating seal which filled the gap around the outer mainwheel tyre in the stowed position. This proved maintenance-hungry and didn't make much difference to the drag, so was replaced by the multi-petal rubber flap system which seals the gap ever since.

The Cessna 210 originally had main gear doors, but later models didn't for the same reasons as on the 737.

Regards - musang
 
User avatar
HAWK21M
Posts: 29929
Joined: Fri Jan 05, 2001 10:05 pm

RE: Boeing 737 Landing Gear Doors?

Mon May 04, 2009 10:24 pm

Actually each MLG on the B737 has a Outboard ,mid & Inner Landing gear door,mechanically attached to the gear & operated by it.
True there is no door covering the exposed wheel & a hub cap is provided for aerodynamic reasons.
Considering the weight saved & non use of sequence valves and added components,this MLG construction has served well for the B737.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
RandWkop
Posts: 99
Joined: Sat May 05, 2012 10:56 pm

RE: Boeing 737 Landing Gear Doors?

Sat Aug 24, 2013 8:52 pm

If a manufacturer tried to certify the same system, on a new design aircraft, would the FAA / EASA pass it?
 
User avatar
Starlionblue
Posts: 17212
Joined: Fri Feb 27, 2004 9:54 pm

RE: Boeing 737 Landing Gear Doors?

Sat Aug 24, 2013 9:19 pm

Quoting RandWKOP (Reply 7):
If a manufacturer tried to certify the same system, on a new design aircraft, would the FAA / EASA pass it?

They have and the will. There's nothing inherently unsafe about having the gear exposed.

Case in point, the Cessna Citation X, one of the fastest civilian jets around. Exposed mains.

http://home.iwichita.com/rh1/hold/av/avhist/csn/cx_dayr.jpg
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Viscount724
Posts: 19287
Joined: Thu Oct 12, 2006 7:32 pm

RE: Boeing 737 Landing Gear Doors?

Sat Aug 24, 2013 9:39 pm

Another low-slung aircraft, the CRJ (and Challenger business jet predecessor), also lacks landing gear doors.


View Large View Medium
Click here for bigger photo!

Photo © Petr Gorbunov

 
yeelep
Posts: 730
Joined: Mon Apr 04, 2011 7:53 pm

RE: Boeing 737 Landing Gear Doors?

Sun Aug 25, 2013 12:47 am

Quoting HAWK21M (Reply 6):
Actually each MLG on the B737 has a Outboard ,mid & Inner Landing gear door,mechanically attached to the gear & operated by it.

To be really picky, the outer gear door is attached to the wing and connected to the gear by a operator rod.
 
User avatar
HAWK21M
Posts: 29929
Joined: Fri Jan 05, 2001 10:05 pm

RE: Boeing 737 Landing Gear Doors?

Thu Aug 29, 2013 7:54 pm

This is one oldie........

No sequencing valve needed  
I may not win often, but I damn well never lose!!! ;)

Who is online

Users browsing this forum: m1m2, RetiredWeasel and 13 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos