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tigerrick(at)mindspring.c
Guest

Posted: Sun Oct 25, 2009 8:23 am Post subject: Nose wheel fork failure

Yes, I know, Jerry.



My 601XL has a steerable nosewheel, just as designed. I was just responding to Larry's assertion that free-castering nosewheels are inferior in some way.



The ONLY way you can impart a side load to the nose fork on the 601 is to land with it cocked significantly to one side. This means either full rudder deflection or something not right in the initial rigging. But it's just speculation at this point, until the facts are in.



Rick



--

psm(at)att.net
Guest

Posted: Sun Oct 25, 2009 8:53 am Post subject: Nose wheel fork failure

Hi Rick,



One problem I have had with "Yankee" type planes has to do with the 

lack of nose wheel steering when taking off in a crosswind.  I found 

I had to apply brakes to one side while using takeoff power to keep 

the plane pointed down the runway for the initial takeoff run.  I 

suppose the rudder will keep it pointed down the runway when enough 

speed is reached for rudder effectiveness, but in the beginning you 

are applying opposing forces, throttle and brakes, at the same time 

in order to perform a normal operation.  (My brief experience with 

this problem was in a rented AA5 many years ago.)



I agree with your point about taxi control with the brakes.  It works 

just fine.  However, I prefer the steerable nose wheel for taxiing 

too.  It is true that the free castering nose wheel can make a 

tighter turn, but I have found the typical Cessna arrangement turns 

tighter if you use both differential braking and nose steering together.



I am currently flying a Tecnam Echo that has a brake handle and nose 

steering.  This turns OK, but I find it won't turn quite as tight a 

circle on the ground as I would prefer.  It takes a little planning 

to turn into the wind for run-up and then get back to the heading for 

getting to the runway.  This wouldn't be a problem with a large 

run-up pad, but that is not what you find at my home airport.



Best regards,



Paul

XL awaiting engineering changes

At 08:42 AM 10/25/2009, you wrote

 	  Quote: 	
		  

<tigerrick(at)mindspring.com>



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.

Ron Lendon

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

Posted: Sun Oct 25, 2009 3:38 pm Post subject: Re: Nose wheel fork failure

 	  larry(at)macsmachine.com wrote: 	
		  

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,



As I recall the XL plunks down the nose wheel right down after touching the mains in a full stall landing (only flew one once).  It also had the main gear reversed from the design position.  The photo guide has many pictures of the main gear in the reversed position, it is noted that the pictures are not correct but many people have followed those pictures and have a heavy nose wheel as a result.  Don't know if this is the case here but it merits discussion.

_________________
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/

jfowler120(at)verizon.net
Guest

Posted: Sun Oct 25, 2009 4:20 pm Post subject: Nose wheel fork failure

I've stayed out of this but -- a couple of  comments.  

  

 We've had one or more hard landings because of the  nose thump-down habit -- more than one in gusty conditions.  This  eventually led to a firewall and stiffener replacement -- along with the  phenolic block in the lower main gear.

  

 We've changed a few things, besides the  repairs.  Half flap approaches, full nose up trim, 60 kias on final to  touch down.  Makes for a much smoother landing and virtually no touchdown  nosegear thump.  Also, BTW, hold the stick back with some nose up trim on  takeoff -- it takes the pressure off a weak point in this airplane.

  

 As to this incident -- it certainly appears that  you had rudder in you didn't realize or something was really wrong with the  rudder-nose gear pushrods after taxi started. Prop strike -- hope you are  getting an engine teardown to check the interior!

  

 Karl

 [quote]   ---

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sun Oct 25, 2009 4:36 pm Post subject: Re: Nose wheel fork failure

A follow up on the discussion so far,main gear reversed to lighten loads on to nose gear.As aircraft was starting to drift to the left a SMALL amount of right rudder applied to straighten back to center of runway [sealed] .As the nose was a foot or so off the ground when down elevator applied,I never dreamt that  it would bounce and thump from that hight. But I do now.Repair bill including prop around $2000.00   Cheers T87

mhubel

Joined: 05 Sep 2009
Posts: 141

Posted: Mon Oct 26, 2009 4:40 am Post subject: Re: Nose wheel fork failure

I might add that I had a slightly similar event. It was on the second landing. The aircraft clearly "landed" very nose heavy. One seasoned observer said he thought no aircraft could survive un-damaged.

I bent the nose wheel assembly back under the fuseloge and of course broke the prop. Without going into all the details of how this happened as there are always multiple things that typically add up to cause such an event. My thoughts were that after flying 20 years in an AA-5, I am still convinced that the AA-5 with its long nose assembly and castering wheel,  just might have survived with a large bounce. This assumes that one did full power go-around. I still think the nose wheel of the 601 design is a weak point.

On the prop strike, Jabiru has a specific procedure to check the crank without engine the tear down. According to Jabiru USA, they have had over 20 prop strikes reported and none have resulted in damaged cranks so far. This includes the ones where an engine tear down was done. Check with Pete at Jabiru USA for the details. They are not available on-line. I have attached the procedure.

Prop Strike Check Crank Run Out.tif

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Prop Strike Inspection.pdf

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Prop Strike Inspection.pdf

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_________________
Mark Hubelbank
N708HU
CH601XL
Jabiru 3300
Rotec TBI 40-3 carb
Sensenich ground adj prop.
240 hr TAF
Pictures at photo.hubbles.com

Ianrat

Joined: 31 Mar 2008
Posts: 43
Location: Brisbane AUSTRALIA

Posted: Mon Oct 26, 2009 9:34 pm Post subject: Re: Nose wheel fork failure

Thruster 87 sorry to here about your plane. Glad to here that you are Ok 



Ianrat

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Tue Oct 27, 2009 12:11 am Post subject: Re: Nose wheel fork failure

It would be nice to come up with a mod to strengthen the fork to side loading especially for sealed runways which is not as forgiving as grass strips.My confidence in the design of the fork has been dented, and  as such would appreciate if anyone else has any ideas for improvements  or arguments to leave it as is, considering the number flying.Cheers T87

Gig Giacona

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

Posted: Tue Oct 27, 2009 5:33 am Post subject: Re: Nose wheel fork failure

 	  Thruster87 wrote: 	
		  It would be nice to come up with a mod to strengthen the fork to side loading especially for sealed runways which is not as forgiving as grass strips.My confidence in the design of the fork has been dented, and  as such would appreciate if anyone else has any ideas for improvements  or arguments to leave it as is, considering the number flying.Cheers T87 	




I may have missed it in a previous post, but did you have the fork doubler in place?

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

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Tue Oct 27, 2009 1:15 pm Post subject: Re: Nose wheel fork failure

 	  Gig Giacona wrote: 	
		   	  Thruster87 wrote: 	
		  It would be nice to come up with a mod to strengthen the fork to side loading especially for sealed runways which is not as forgiving as grass strips.My confidence in the design of the fork has been dented, and  as such would appreciate if anyone else has any ideas for improvements  or arguments to leave it as is, considering the number flying.Cheers T87 	




I may have missed it in a previous post, but did you have the fork doubler in place? 	
Hi Gig, Yes the gear was reversed and the doubler was installed.I'm now wondering if the lower bearing mod which allows smoother rotation [less friction] may have contributed?? Is the high friction an issue during flight?? I'll now properly go back to specs Cheers T87

Gig Giacona

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

Posted: Tue Oct 27, 2009 1:40 pm Post subject: Re: Nose wheel fork failure

Was the wheel bent to the left by any chance?



The reason I asked is that I've seen two fast taxi accidents in my 30 years of flying where pilots tried to "hit the brakes" buy slamming down on the left rudder.

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

paulrod36(at)msn.com
Guest

Posted: Tue Oct 27, 2009 1:42 pm Post subject: Nose wheel fork failure

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Gig, how about using a T-shaped outer piece?  The stem of the T  wouldn't need to be more than 3/4" or  create too much drag, but it ought  to greatly stiffen the fork to side loads. Naturally, it would need to be  tapered and ground off just above the axle bolt.

  

 Paul R     (Nose gear? We don' need no esteenkin' nose  gear!)

 [quote]   ---

Gig Giacona

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

Posted: Tue Oct 27, 2009 1:50 pm Post subject: Re: Nose wheel fork failure

 	  paulrod36(at)msn.com wrote: 	
		  <xml><xml><endif>  Gig, how about using a T-shaped outer piece?  The stem of the T  wouldn't need to be more than 3/4" or  create too much drag, but it ought  to greatly stiffen the fork to side loads. Naturally, it would need to be  tapered and ground off just above the axle bolt.

  

 Paul R     (Nose gear? We don' need no esteenkin' nose  gear!)

 	




Don't ask me about redesign issues. I don't know nothin' about design.

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

daveaustin2(at)primus.ca
Guest

Posted: Tue Oct 27, 2009 2:53 pm Post subject: Nose wheel fork failure

I cannot help wondering what piece of the a/c would have failed if the forks 

had not given way?  Would the leg have bent, or been torn from he firewall? 

How many 601s have bent the fork from the hundreds flying today?

Think about it, folks.  Chris knows what he is doing.

Dave Austin  601HDS - 912

chris Sinfield

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

Posted: Tue Oct 27, 2009 3:04 pm Post subject: Re: Nose wheel fork failure

Dave

Chris knows what he is doing. ?? Maybe Chris H knows what he is doing? My wife often says I don't know what I am doing.. But I am Chris S..



Its morning here Down Under

Chris S.

daveaustin2(at)primus.ca
Guest

Posted: Tue Oct 27, 2009 3:32 pm Post subject: Nose wheel fork failure

G'Day Chris,

Pom here in Canada.

My 1993 601 (not me) bent the fork rather quickly, so I fitted the doubler. 

But by then I'd managed to learn to keep the nosewheel off the ground until 

just enough elevator influence is left to lower it to the runway with NO 

brakes on.  I was glad the fork had bent.  Good lesson.



Dave Austin  601HDS - 912

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Tue Oct 27, 2009 3:57 pm Post subject: Re: Nose wheel fork failure

 	  Gig Giacona wrote: 	
		  Was the wheel bent to the left by any chance?



The reason I asked is that I've seen two fast taxi accidents in my 30 years of flying where pilots tried to "hit the brakes" buy slamming down on the left rudder. 	
To the right,it bent from the radius at the top.Left hand side of fork rubbing the ground and the right side bent up towards the nose leg.The nose leg held on very well and it bent about 5 deg  250mm up from the base,base plate twisted about 5mm and the brunt was taken by the structure aft of the lower bearing support.Cheers T87

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Tue Oct 27, 2009 6:51 pm Post subject: Nose wheel fork failure

Just remember to set the rudder cable tension with no weight on the  

nose wheel. Because the strut angles backwards at the top, tension on  

the rudder cables is reduced when the strut is compressed under load.



 	  Quote: 	
		   

 >



 Hi Gig, Yes the gear was reversed and the doubler was installed.I'm  

 now wondering if the lower bearing mod which allows smoother  

 rotation [less friction] may have contributed?? Is the high friction  

 an issue during flight?? I'll now properly go back to specs Cheers T87




	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

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

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Wed Oct 28, 2009 7:34 pm Post subject: Re: Nose wheel fork failure

Here's a question for the structural engineers out there,what affect did the wrong wall thickness[.035" instead of .058" ] of the engine mount have  on allowing the two lower mounting points to move towards the middle by 25 -30 mm [that was what the engine mount holes were out by and that is not taking into consideration of how much spring back there was on the engine mount during the max loads] to accommodate the the crushing of the firewall and lower bearing support structure as the nose wheel leg moved back due to the loads.The thin wall tube no.6-7 bent forward [the triangle piece connecting the two lower mounting points] In other words how much of the structural loads is carried by the engine mount itself  other then the engine loads.Cheers T87

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