Crosswind landings- a structural discussion

[sailon]

I have read most (if not all) of the discussions on Mooneyspace about crosswind landings, and all have discussed pilot skill vs, aerodynamics.  However, I also have been studying the mechanics of the Johnson bar, especially its single point of failure (i.e., the weld of the bar to the linkages).  I was wondering if there is a correlation between the published / demonstrated low X-wind capabilities and the large side loads imposed on the J-bar during a perfect X-wind landing.  (Side loads will be imposed, at least due to the cocked nose wheel on nose wheel touchdown).  I know pilots can land in a 35 kt x-wind, however, it also makes me wonder if those same pilots are experiencing premature J-bar failures.

Thanks!

[N6758N]

Based on my experience, if a proper crosswind landing is made, the airplane should be pointing straight down the run way by the time the nose touches down. As far as the mains go, the down lock mechanism is what is taking the side load, not the retract mechanism- at least that is what i gather from working on my own aircraft. 

[N201MKTurbo]

Cross wind landings won't put side loads on the Johnson bar. If your preloads are correct it should put no loads on the actuation mechanism. It will put loads on the overcenter links on the main wheels, but unless they come off of overcenter, which they should never do, no load will be transferred beyond that.

[sailon]

Yes, the airplane will be pointing straight down the runway, however the crosswind correction applied by the rudder pedals will cock the nosegear.

 

Edited December 21, 2016 by sailon
spelling error

[N6758N]

8 minutes ago, sailon said:

Yes, the airplane will be pointing straight down the runway, however the crosswind correction applied by the rudder pedals will cock the nosegear.

 

The rudder is attached to the nose gear via springs, so therefore there would be no sideload on the gear. otherwise the airplane would dart off the runway.

[N201MKTurbo]

5 minutes ago, N6758N said:

The rudder is attached to the nose gear via springs, so therefore there would be no sideload on the gear. otherwise the airplane would dart off the runway.

There are no springs in the Mooney rudder or steering system. They are all directly connected.

[N6758N]

Just now, N201MKTurbo said:

There are no springs in the Mooney rudder or steering system. They are all directly connected.

No springs, but isn't the rudder on a bungee? Or is that the elevator only?

[N201MKTurbo]

Just now, N6758N said:

No springs, but isn't the rudder on a bungee? Or is that the elevator only?

There are springs in the rudder aileron interconnect and there are spring bungees on the elevator. There are no bungees on the rudder. The bungees add pressure to the tail so the elevator will stay in the most aerodynamic position during cruise.  

[sailon]

I know that all airplanes I have flown with a steering nosewheel, it will dart in the direction of rudder correction when the nosewheel touches down.  Something to be ready for.

[AndyFromCB]

13 minutes ago, sailon said:

I know that all airplanes I have flown with a steering nosewheel, it will dart in the direction of rudder correction when the nosewheel touches down.  Something to be ready for.

Never had that problem, but then those of us whom crab and kick have to be quick on their feet ;-)

Edited December 21, 2016 by AndyFromCB

[carusoam]

Skill keeps the side load from being high, no matter how the construction of the airplane is.

But, practicining 35kt X-winds takes on some additional risk, including how gusty that is.

on my best day, I could touch down with the upwind main, then the other main, then the nose.

Getting the weight onto the wheels happens pretty quickly.  If it doesn't you get the sideways movement of the plane.

On my worst days, there is quite a plop as the plane stops flying.

 

Like all things in the design of the airplane.  See where the load comes from, and see where it is transferred to.  Same with cars.  There is only so much side loading that you can create, before the skid marks appear right in line with where you left the road, or runway...

PP thoughts only, a CFI would be better at explaining this...

I never landed with 35kt winds unless they were straight down the runway...

Best regards,

-a-

[sailon]

Never did 35, but plan on taking an instructor up to get used to 20 which is what I was comfortable with in my Arrow.  Just wanted to check with the Forum to make sure we won't break the airplane!

 

Thanks all.

[Guitarmaster]

Never did 35, but plan on taking an instructor up to get used to 20 which is what I was comfortable with in my Arrow.  Just wanted to check with the Forum to make sure we won't break the airplane!
 
Thanks all.

I had the same worry when I first bought my airplane. Found gear is extremely Stout and I would be really surprised if you could break it in a side load.

Sent from my XT1585 using Tapatalk

[Bob_Belville]

I've gotten away with too many landings that should have busted something.  

[Yetti]

If you do the upwind main landing the force is pulling the gear to the outside which is away from trying to fold the gear.   By the time the nose wheel comes down, directional intent is established with the main wheels.  One main landings don't work on icy runways as my instructor found out when he went to fly in Alaska

[salty]

7 minutes ago, Yetti said:

If you do the upwind main landing the force is pulling the gear to the outside which is away from trying to fold the gear.   By the time the nose wheel comes down, directional intent is established with the main wheels.  One main landings don't work on icy runways as my instructor found out when he went to fly in Alaska

You're going to have to expound on that one. I don't see why ice would matter in a properly executed slip landing - not anymore than it matters on any landing that is. Keep in mind, this is coming from someone that's never landed in weather below 45 degrees.

Edited December 23, 2016 by salty

[Yetti]

as the plane levels out (slip is coming out, but wind is still trying to blow the plane downwind) to bring the other main down, it is the friction on the up wind main that holds the plane going straight down the runway.

[takair]

Sailon

as others indicated, each gear has an overcenter down lock mechanism.  They are held overcenter by proper gear rigging, which is the subject of an annual AD.  If done right, no force transfer to the Johnson bar due to ground loads.  Your rudder pedals are essentially directly linked to the nose gear. There is an interconnect spring between the rudder/nose gear and ailerons as well as bungees under the pilots legs.   Many Cessna aircraft are not directly connected to the nose gear, they have a spring between them.  The trailing link of the Mooney takes care of much of the alignment issues if you are not properly aligned.  The nose gear trail is critical to keep from having a twitchy nose gear.  I barely notice if my nose wheel is slightly turned on touchdown.  I find Pipers to be more harsh in feedback to the pedals if not aligned on touch down.....Cessna...with the spring is the most forgiving.

[flyboy0681]

Not related to Mooney's but crosswind landings, I was watching a video of extreme crosswind landings with a friend who flies 767's. I said that it never ceases to amaze me just how much punishment an airliner landing gear can take. Not sure if he is correct, but he said commercial aircraft need to withstand 3g's of side-load for certification. I found that statement incredible.

[Bob_Belville]

Don't think those things are made of white pine. 

[Yetti]

If you have ever flown SWA you would know how much a 737 gear can take.   I try hard not to ask if they get to count both landings....