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Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sat Oct 24, 2009 12:39 pm Post subject: Nose wheel fork failure

During high speed taxi runs at around 50knots  lifted the nose wheel off  and the mains maybe yes or no [ spectators not sure either] on lowering via elevator input [in hind site should have just pulled more elevator  nose up for a smoother transition]  the nose wheel  come down and  bumped  back up[the runway has a couple of bumps as well] and on going down again the fork bent side ways as it hit the runway [due to a small right rudder input the wheel would have been pointing to the right].Basically the fork just collapsed/folded  to the right jammed the nose wheel  thus causing  a prop strike,bent axle,firewall,and nose wheel  strut. So it's back to the hangar for repairs and I'll look at strengthening  the fork so it will resist the side loads better. Sitting here with a gnawing feeling in the pit of my stomach and trying to asses what went wrong. Cheers T87

chris Sinfield

Joined: 28 Nov 2006
Posts: 270
Location: Sydney Australia

Posted: Sat Oct 24, 2009 1:06 pm Post subject: Re: Nose wheel fork failure

Allan

If you need to borrow some parts till yours are ready / fixed give me a call. Sorry for your troubles.. 

Chris

Terry Phillips

Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT

Posted: Sat Oct 24, 2009 1:59 pm Post subject: Nose wheel fork failure

Bummer, T87



That is everyone's worst fear. I hope that your crankshaft is OK. The 

linkage between the rudder and the nose wheel has long been one of my 

concerns about the basic design. I wish there was an option for a castering 

nose wheel. I'd love to just cover over those slots in the fire wall with 

solid steel. Keep us informed about the repair process.



Terry

At 01:39 PM 10/24/2009 -0700, you wrote:



 	  Quote: 	
		  During high speed taxi runs at around 50knots  lifted the nose wheel 

off  and the mains maybe yes or no [ spectators not sure either] on 

lowering via elevator input [in hind site should have just pulled more 

elevator  nose up for a smoother transition]  the nose wheel  come down 

and  bumped  back up[the runway has a couple of bumps as well] and on 

going down again the fork bent side ways as it hit the runway [due to a 

small right rudder input the wheel would have been pointing to the 

right].Basically the fork just collapsed/folded  to the right jammed the 

nose wheel  thus causing  a prop strike,bent axle,firewall,and nose 

wheel  strut. So it's back to the hangar for repairs and I'll look at 

strengthening  the fork so it will resist the side loads better. Sitting 

here with a gnawing feeling in the pit of my stomach and trying to asses 

what went wrong. Cheers T87  


	




Terry Phillips  ZBAGer

ttp44~at~rkymtn.net

Corvallis MT

601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons 

are done; waiting on the wings

http://www.mykitlog.com/N47TP/

_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings.

ter_turn(at)yahoo.com
Guest

Posted: Sat Oct 24, 2009 1:59 pm Post subject: Nose wheel fork failure

First, sorry for your mishap..but it could have been worse!  I'm sure there are other 601 XL drivers thinking about their up coming test flights..and I'm wondering  (1) did you get any time in a 601XL prior and (2) are you going to reconsider high speed taxi runs based on your experience? I hope the damage is not too costly in time or money!  Thanks.



Terry



--- On Sat, 10/24/09, Thruster87 <alania(at)optusnet.com.au> wrote:

[quote]

From: Thruster87 <alania(at)optusnet.com.au>

Subject: Zenith601-List: Nose wheel fork failure

To: zenith601-list(at)matronics.com

Date: Saturday, October 24, 2009, 3:39 PM



--> Zenith601-List message posted by: "Thruster87" <[url=/mc/compose?to=alania(at)optusnet.com.au]alania(at)optusnet.com.au[/url]>



During high speed taxi runs at around 50knots  lifted the nose wheel off  and the mains maybe yes or no [ spectators not sure either] on lowering via elevator input [in hind site should have just pulled more elevator  nose up for a smoother transition]  the nose wheel  come down and  bumped  back up[the runway has a couple of bumps as well] and on going down again the fork bent side ways as it hit the runway [due to a small right rudder input the wheel would have been pointing to the right].Basically the fork just collapsed/folded  to the right jammed the nose wheel  thus causing  a prop strike,bent axle,firewall,and nose wheel  strut. So it's back to the hangar for repairs and I'll look at strengthening  the fork so it will resist the side loads better. Sitting here with a  gnawing feeling in the pit of my stomach and trying to asses what went wrong. Cheers T87  





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=269254#269========================http://www.matronics.c --> http========================

           [quote][b]

Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Sat Oct 24, 2009 2:08 pm Post subject: Re: Nose wheel fork failure

First off did you have the fork doubler in place?



Second 50 kt taxi runs are way too fast.

_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sat Oct 24, 2009 2:46 pm Post subject: Nose wheel fork failure

Does your nosewheel fork have the doubler? My early plans did not show  

a nosewheel doubler, and it didn't come with the kit. I bent my fork  

on my first landing.  The nosewheel fork doubler was added to later  

plans.



I would suggest that anyone who attempts to lift the nosewheel off  

during taxi tests should be prepared to cut the throttle immediately  

and continue to hold the nose up and let it settle instead of trying  

to push forward to set it back down. The elevator is surprisingly  

responsive until you get used to it. I had a prop strike on mine  

during my taxi tests by making the same mistake. The fact that I had a  

70 inch prop instead of the current 68 inch prop didn't help either.



On Oct 24, 2009, at 4:39 PM, Thruster87 wrote:



 	  Quote: 	
		   

 >



 During high speed taxi runs at around 50knots  lifted the nose wheel  

 off  and the mains maybe yes or no [ spectators not sure either] on  

 lowering via elevator input [in hind site should have just pulled  

 more elevator  nose up for a smoother transition]  the nose wheel   

 come down and  bumped  back up[the runway has a couple of bumps as  

 well] and on going down again the fork bent side ways as it hit the  

 runway [due to a small right rudder input the wheel would have been  

 pointing to the right].Basically the fork just collapsed/folded  to  

 the right jammed the nose wheel  thus causing  a prop strike,bent  

 axle,firewall,and nose wheel  strut. So it's back to the hangar for  

 repairs and I'll look at strengthening  the fork so it will resist  

 the side loads better. Sitting here with a gnawing feeling in the  

 pit of my stomach and trying to asses what went wrong. Cheers T87  


	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sat Oct 24, 2009 4:38 pm Post subject: Re: Nose wheel fork failure

I have the latest fork with the doubler installed, but it still folded side ways.I'd done about 3hrs of taxi runs prior two days at around the 40 knot mark and wanted to get near the lift-off envelope to see it would behave.We also did a couple of runs with two up at 45-50 knots and we lifted/lightened [not of the ground] the nose with no problems  again to see how it would perform with the extra weight.It was just fine.On the day with two on board there was a 10knot cross wind and it weather cocked in a very predicable way  and easy to handle.Just prior to the incident it had just passed the final inspection as well. Got the plane now back home and will start the repairs.In Hind site I'd just keep the stick back and use engine power to settle it down just like in a landing.   ASAP Cheers Alan

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Sat Oct 24, 2009 7:08 pm Post subject: Re: Nose wheel fork failure

Sorry to hear about that.  



I have been considering spring loading the front wheel so it can track separately from the rudder.  The front wheel really does need a good caster angle for this to work, but I have been thinking about it.

_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
https://sites.google.com/site/corvairenginedata/

jeyoung65(at)aol.com
Guest

Posted: Sat Oct 24, 2009 7:10 pm Post subject: Nose wheel fork failure

I just did some high speed taxi runs. Because my rudder and nose wheel were not inline I had a hard time keeping the aircraft on the runway untill I corrected it. I did not see the misalignment until the son pointed it out.I also was able to check the airspeed indicator during this taxi runs using the GPS, within 5 MPH up to 50 MPH. Would suggest all make hight speed taxi to see if the rudder and nose wheel are align  Jerry of GA 

 

 

 --

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sat Oct 24, 2009 7:25 pm Post subject: Re: Nose wheel fork failure

Don't have any pics of the collapsed fork as we straightened so we could move the aircraft

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Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sat Oct 24, 2009 7:28 pm Post subject: Re: Nose wheel fork failure

And this

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craig(at)craigandjean.com
Guest

Posted: Sat Oct 24, 2009 8:03 pm Post subject: Nose wheel fork failure

Does your fork have the doubler (6G1-5 on an XL)? Any photos?



-- Craig



--

craig(at)craigandjean.com
Guest

Posted: Sat Oct 24, 2009 10:36 pm Post subject: Nose wheel fork failure

On the photo of the front gear is that extra stepped rod resting in the V

block (below the main cross tube that links to the rudder pedals) your own

addition or something from the factory? I'm guessing you had to add it when

the cross tube on the factory part didn't reach the V because to the stop

plate on the top of the gear. I think I can also see an extra shim fitted

into the V of the black nylon part.



-- Craig



--

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sun Oct 25, 2009 1:18 am Post subject: Re: Nose wheel fork failure

 	  craig(at)craigandjean.com wrote: 	
		  On the photo of the front gear is that extra stepped rod resting in the V

block (below the main cross tube that links to the rudder pedals) your own

addition or something from the factory? I'm guessing you had to add it when

the cross tube on the factory part didn't reach the V because to the stop

plate on the top of the gear. I think I can also see an extra shim fitted

into the V of the black nylon part.



-- Craig



-- 	
It was a mod I did to allow the nose wheel to move more freely.It  has a stainless steel rod with phosphor bronze bushes resting on a crom-moly plate bolted thru the bearing material for the V.It really made the rudder pedals  free up and smooth to operate and self centering the same as the original.As you can see it stayed intact even thro the nose leg tube bent. Cheers

aussiech650

Joined: 04 Oct 2009
Posts: 25
Location: Sydney, Australia

Posted: Sun Oct 25, 2009 1:36 am Post subject: Re: Nose wheel fork failure

Alan, I have an XL601 nose leg that I will not be using. Give me a call if you would like it.

Greg 0415610593.

larry(at)macsmachine.com
Guest

Posted: Sun Oct 25, 2009 7:10 am Post subject: Nose wheel fork failure

Ron,

That fork has a logical reason for failing and I'm sure it'll reveal 

itself eventually.

The steerable linked nose gear is more asset than liability. To be able 

to steer around potholes and rough fields is

a major improvement over differential braking. I've experienced both 

types. For the tail dragger, it's logical, but for tri-gear

it would be detrimental to add a free-caster nose-wheel to side braking 

mains. I know it's done in some aircraft, but

it's a much lesser solution to the steerable nose wheel.

Curious how the nose wheel steering got sideways far enough to fail the 

fork. Or it would seem

there was not enough attention to where the nose wheel was at the time.



Larry McFarland 601HDS at www.macsmachine.com



Ron Lendon wrote:

 	  Quote: 	
		   



 Sorry to hear about that.  



 I have been considering spring loading the front wheel so it can track separately from the rudder.  The front wheel really does need a good caster angle for this to work, but I have been thinking about it.



 --------

 Ron Lendon, Clinton Township, MI

 WW Corvair with Roy's Garage 5th bearing

 Zodiac XL, ScrapBuilder 

 http://www.mykitlog.com/rlendon

 Corvair Engine Prints:

 http://home.comcast.net/~rlendon/site/

tigerrick(at)mindspring.c
Guest

Posted: Sun Oct 25, 2009 7:43 am Post subject: Nose wheel fork failure

Not to pick a fight here, Larry, but after flying close to 5000 hours in Grumman American airplanes with free castering nose gear, I have to object to your post.



Besides the obvious simplicity and ease of maintenance of the free castering design, its 180 degree pivot allows for incredibly tight turns while parking or simple maneuvering around objects. Assuming the airplane doesn't have a draggy brake on one side or the other, taxiing is a breeze with an occasional tap on the brake to maintain directional control.



The only negative I can see is replacing brake pads slightly more often, but pads are cheap and there's no linkage, springs, holes in the firewall, or any of the other hoopla associated with a steerable nosewheel. And best of all, the nose wheel alignment to the runway self corrects automatically upon landing, so any worry about side loads is moot.



Your claim that it's "a much lesser solution" needs some qualification. I'm curious, in what way?



Best,



Rick Lindstrom

ZenVair N42KP



--

jeyoung65(at)aol.com
Guest

Posted: Sun Oct 25, 2009 7:58 am Post subject: Nose wheel fork failure

Could it be possible that the "free-caster nose wheel" is the problem? I do not understand how this was accomplish!!!!Landing in with a crosswind would indicate the nose wheel as cocked so when the nose wheel came down a side load was appllied to it. Now with a caster nose wheel, the nose wheel would be forced to turn to it's limit. Thus the fork could bend. My $0.02   Jerry of GA

 

 

 --

jeyoung65(at)aol.com
Guest

Posted: Sun Oct 25, 2009 8:02 am Post subject: Nose wheel fork failure

Rick, you are talking about a gear that is design to have a castering gear. The 601 nose gear was not designned for a castering nose wheel. On a castering nose wheel the strut is in front of the wheel center so the wheel is drag down the runway not pushed.  Jerry of GA

 

 

 --

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sun Oct 25, 2009 8:09 am Post subject: Nose wheel fork failure

I don't think you should try to strengthen the fork any more than it  

is. If you make it too strong, in a hard landing it would shift the  

first point of failure to some other component. From the looks of  

those photos, the nose gear must have come down very hard and it  

wouldn't have helped much if the fork had stayed intact. That fork  

absorbed a lot of energy before it failed. It won't do much good to  

make the fork indestructible if it causes the strut to shear off and  

you plant the nose on the runway at 40 mph.



At 50 mph and full throttle, that elevator has a whole lot of  

authority, you have to use a light hand on it. At full throttle, once  

that nosewheel comes off, that airplane wants to get airborne in a  

hurry. Be ready to chop the throttle and let it settle in.

-- 

Bryan Martin

CH 601 XL

Builder No: 64003

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

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