737 main gear

[BLWME]

question that is constantly being asked.

Why does the 737 look crooked when taxing behind it.

Is the main gear some what gimbled/ or able to pivot for crosswinds.

Is the hull off set

Just an optical freakdom from the right seat view point?

 

[KLJ]

I'm not a systems guy by any stretch of the imagination, but ...

It's my understanding all the 737s prior to the -700 do have a bit of flex or gimble to the main landing gear. The -700 does not which is one of the reasons it is a little harder to land smoothly.

This is anecdotal at best or perhaps a common excuse for a bad landing in the -700!

KJ

 

[BLWME]

Thank you for the response,

Ive talked with pilots for 2 years now and no one has the diffinative answer, but the most common one is that it has some flex or gimble in the gear.

again thanks

 

[firstthird]

I've only got 40 hours in the 737 so take it with a grain of salt but from what I've read in our manuals and been told, here is how I understand it.

The 737 has landing gear that can castor to the direction of motion up to the full crosswind limit (36 knots for our plane). So, one of the 4 crosswind landing techniques is to fly the approach in a crab and land in a crab, the gear will swivel. When this happens, the gear stay canted until the next takeoff when they are able to straigthen back out. This has been discussed before and I'm pretty sure what I'm saying is consistent with the previous replies. The optical illusion is in fact a 737 where the tube is pointed slightly different than the direction of motion down the taxiway since the last landing was apparently in a crosswind with a crab still in at touchdown. I think part of the rationale is so that the autopilot can do an autoland up to some pretty hefty crosswind limits (20 knots for our plane) since I doubt the autopilot kicks out the crab, I think this was the solution. That is speculation though on my part.

Any systems experts feel free to pile on if I screwed something up.

 

[justApilot]

That's pretty much how it works.

 

[Sammy@US]

On 737-300's and 400's, there is a +/- 3 degree (if I remember the correct angle) pivot play in the main gears to ease the stress in crabbed landings. And yes, they are taxiing crooked, so your observation is correct!

Good question!

 

[firstthird]

That could be but I'm pretty sure the design is the same from the -100s on up and the 100/200 had the low profile engines rather than the CFM-56s on there now.

 

[Groucho]

737 Main Gear

The fact is there is no gimble, what ever a gimble is, but there are shimmy dampers on both main gears.

If you can imagine a straight main gear shock strut cylinder and the main landing gear axels and wheel assembly connected directly below it. The main shock strut handles the up and down but on a dual bogey wheel assembly you need a way for wheel imbalance, or uneven breaking to not be transmitted to the airframe.

Enter the horizontal shimmy damper. This device sits on the rear fork assembly that connects the wheel bogy to the shock strut. If the wheels pick up a rapid vibration they cannot transmit it to the airframe. This prevents that "shopping cart wheel syndrome" when you get a bad or unbalanced shopping cart.

I have had a praticular intrest in this little device ever since I slid down the runway in Huntinton, W. VA. in an F-28. The F-28 did not have this type of device on its main gear and wheel imbalance eventually caused a fatigue crack in the upper fork.
On landing the fork seperated and due to wheel vibration we lost the left main gear tires and went down the runway on the strut.

On touchdown the insturment panel disapeared in a vibratory fit and all the crap in the galleys was on the floor. It's when I saw one of the main gear tires bounding off into the boondocks that I figured this was not my day.

I look kinda close at that stuff now.