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Lighter tailwheel

 
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Duncan McFadyean



Joined: 18 Jan 2011
Posts: 129

PostPosted: Tue Oct 13, 2020 8:35 am    Post subject: Lighter tailwheel Reply with quote

I'm exploring options for losing some weight from behind the CG, because my payload is limited by balance rather than all-up weight. A few pounds at the tail should do it.
Has anyone fitted a light(er) tailwheel, and what make was it/how did it perform?
There's a standard mod for RVs that achieves the same, but I'm hoping for cheaper options.
Any leads?

Duncan McF
Quote:
On 05 October 2020 at 11:40 JohnFrance <77alembert(at)gmail.com> wrote:




Hi Erik, I am following the evolution of the play in my tailplane and this is what I have observed.
In my case the play is between TP5 and TP4 almost certainly due to play in the clevis pin on the starboard side.
You can check this by marking the junction between TP5/TP4 with a marker pen.
The edge of TP5 is just visible in your photo exiting the nylon bush TP10. The movement will be very small but should be visible. Check both sides and the same thing for the junction TP4/TP9.

The good news is there are several modifications available to fix this, one being to use Loctite between TP4/5/9 and various clamping methods are available too which are fine.
As Pete pointed out however, the bolts in yours (appear to) clamp directly on the Nylon TP10 and that is not good.

If Loctite has already been used but failed to hold on one of the components you will have to find a way to dis-bond the others to remove TP4 from the aircraft to carry out the mod!
I have a theory on that but not yet put it into practice! If anyone has done that please share your experience?

Here is a text written by the late Nigel Graham on the subject.

Firstly, please find attached, the details of the tailplane clamp arrangement I developed (and you requested) ...... it could be relevant to your problem. I have also attached another mod that I developed to prevent the possibility of a dis-bonded TP5 or TP6 bush (these are built into the tailpanes – refer to the online manual for details)

…. and on that note …

There are two possible reasons for slop in the tailplanes, one is benign and relatively easy to fix and the other is a lot more serious and could kill you if not addressed immediately.

First, an overview of the pitch drive train; the pitch pushrod transfers pitch linear motion into the TP9 arm, this rotates the TP4 (torque tube) via the TP14C pins.

The rotating shaft transmits the motion back out to the TP12 drive plates via the TP14D pins and hence to the tailplanes.

The first thing to check is the cumulative play in the TP14 drive pins.

This is a well-documented issue and was addressed by the factory by increasing the diameter of the pins. This was not a good engineering solution as it only delayed the eventual re-occurrence of the problem.

Pat Tunney’s “clamp block” mode (that you commented on), my clamp mod (attached) and squirting Locktite into the gap were all far better solutions designed to solve the problem of relative movement.

You can test if this is your problem by sliding the tailplanes off the torque tube and placing two long lever bars (gently) against each drive plate (TP12) pin and the torque tube and trying to rotate port and starboard in opposite directions. There should be NO movement. If there is, this is your problem. This is non-critical and can be solved by any of the above mentioned solutions.

If you detect no movement here, then the problem lies in the tailplanes – and this IS serious and the A/C should be grounded immediately until repairs are made.

The problem lies in the way the tailplanes were built. The build instructions called for the two supporting stainless steel bushes to be bonded into the soft blue foam of the TP cores. If you read the attached mod document “070625 – Tail-plane drive pin mod” there is a fuller description of the problem and solution.

Very little supports these bushes laterally, and if they should become dis-bonded, the tailplane can slide laterally until, in extreme cases, it disengages from the two drive pins on the TP12 plate. At this point one tailplane will rotate/flutter with ferocious force and the back of the fuselage will most likely break away – the aircraft will break up in flight.

This happened to G-HOFC in 2007, I passed my information on to the LAA and who subsequently issued mandatory Mod 73 (attached).

--------
Europa mono Nr 192




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=498675#498675




Attachments:

http://forums.matronics.com//files/tail_plane_drive_pin_mod_196.pdf








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John Wighton



Joined: 18 May 2010
Posts: 187

PostPosted: Thu Oct 15, 2020 12:30 am    Post subject: Re: Lighter tailwheel Reply with quote

Not cheap by any means but a Ti leg and wheel is about as light as you will get.

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John Wighton
Europa XS trigear G-IPOD
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PostPosted: Thu Oct 15, 2020 5:29 am    Post subject: Lighter tailwheel Reply with quote

Hi John, can you give more details on this? Ti leg?

Sent from my iPad

Quote:
On 15 Oct 2020, at 09:30, John Wighton <john(at)wighton.net> wrote:



Not cheap by any means but a Ti leg and wheel is about as light as you will get.

--------
John Wighton
Europa XS trigear G-IPOD




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John Wighton



Joined: 18 May 2010
Posts: 187

PostPosted: Thu Oct 15, 2020 11:59 pm    Post subject: Re: Lighter tailwheel Reply with quote

No details to hand but it could be a new design and manufacture - is not impossible.

It would also be possible to replace the (Mod 43) tailwheel spring with a carbon fibre version. This would require testing off aircraft (to match spring rate and test strength) but could save a considerable part of the 10.2 lbs of the total mass (which may include the additional reinforcements installed anyway).

I would probably go with a moulded CF version myself - UD tows inside wrapped with woven. Using a Ti bush for the attachment bolt.

A Ti tailwheel could be made using a copy CNC machine.


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Duncan McFadyean



Joined: 18 Jan 2011
Posts: 129

PostPosted: Sat Oct 17, 2020 2:52 am    Post subject: Lighter tailwheel Reply with quote

John,
<<...A Ti tailwheel could be made using a copy CNC machine....>>
What's the elastic differential between Ti and spring steel?

Duncan McF

Quote:
On 16 October 2020 at 08:59 John Wighton <john(at)wighton.net> wrote:




No details to hand but it could be a new design and manufacture - is not impossible.

It would also be possible to replace the (Mod 43) tailwheel spring with a carbon fibre version. This would require testing off aircraft (to match spring rate and test strength) but could save a considerable part of the 10.2 lbs of the total mass (which may include the additional reinforcements installed anyway).

I would probably go with a moulded CF version myself - UD tows inside wrapped with woven. Using a Ti bush for the attachment bolt.

A Ti tailwheel could be made using a copy CNC machine.

--------
John Wighton
Europa XS trigear G-IPOD




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=498854#498854











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John Wighton



Joined: 18 May 2010
Posts: 187

PostPosted: Sun Oct 18, 2020 1:09 am    Post subject: Re: Lighter tailwheel Reply with quote

D,
You don't need to match the 'spring' properties for the Ti tailwheel. For the spring part for sure - that is why l suggested a carbon version - can be customised to suit.


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