TM817-48

Abstract:  TM817-48: Tail Wheel Fork Extension file location and discussion.

Subject: TM817-48
From: "schwenn109b" 
Date: 1/2/11 8:18 AM
To: G109_Pilots@yahoogroups.com

Anyone have a copy of TM817-48 related to the tail wheel fork extension? I need to change my tail wheel tire and will probably have to make this modification. I have looked on the 109B group site under files and can't find this TM. I have looked at the Photos posted of this modification.

Are the extension plates used for this modification steel or aluminum alloy? From the photos they appear to be aluminum.

Anyone who has done this modification know of the impact on weight and balance? It has to add some weight and the moment arm is long.

Thanks,

Ron

Subject: Re: TM817-48
From: "Pierrot" <pierrot.greff@zFF9l9Y-4fIaHUmIK6xY607s1J09GQ9Xa06U_5ks783LXbtBIouC5NkfCQxfErEdllmmmzIiP2Vr-CYwm1L5WbAD.yahoo.invalid>
Date: 1/3/11 11:05 AM
To: G109_Pilots@yahoogroups.com

Some answers for you Ron

--- In G109_Pilots@yahoogroups.com, "schwenn109b" <schwenn109b@...> wrote:

Anyone have a copy of TM817-48 related to the tail wheel fork extension?

(PRG)I did the modification and will upload the TM on this site. Unfornately it is written in German :-)

I need to change my tail wheel tire and will probably have to make this modification.

(PRG) Certainly you will need to do it unless to found the 1985 model tir on the after market. The current tire sizes are a bit larger.

I have looked on the 109B group site under files and can't find this TM. I have looked at the Photos posted of this modification.

Are the extension plates used for this modification steel or aluminum alloy? From the photos they appear to be aluminum.

(PRG) I am not sure if steel or aluminium. The weight is 235gr. You have to redo the balance. It was favorable for my bird which is heavy from the nose.

Anyone who has done this modification know of the impact on weight and balance? It has to add some weight and the moment arm is long.

Thanks, Ron
(PRG) You are wellcome

Subject: TM817-48
From: "Ron Lee" <schwenn109b@ujIbxsXNgnN_8EWqdK_823NaMfbqD-1enIuRFWfeDpY6JoR5G6_xDEGmRxW5GOZjU-ptOF1evY-odDZ60w.yahoo.invalid>
Date: 1/3/11 11:17 AM
To: G109_Pilots@yahoogroups.com

Pierrot,

Did you purchase the parts for the tail wheel modification from Grob or other, or did you fabricate them from the information in TM817-48?

Thank you,

Ron

Subject: Re: [G109_Pilots] Re: TM817-48 Tail Wheel Fairing
From: Kent Hermsmeyer
Date: 1/4/11 11:11 AM
To: G109_Pilots@yahoogroups.com
CC: dimerarkh <rkh986@oiwQBlHRSWgfit1eoeWd0EO51oVd8wwWFP5LDCwb6wsjmVpbN5jGDJGc1AEQDo3kjATPA0mAGA.yahoo.invalid>

The tailwheel fairing makes no difference to the practical L/D, despite the good intentions. As former owner of both the G109 and G109B, I may have performed among the few systematic glide ratio still air testing of the action of the tailwheel fairing, and am thus responding. Esthetically, the fairing looks sleek. However, the tailwheel apparently flies in a disturbed airflow in which streamlines along the fairing do not make an aerodynamic difference within the flight envelope. Unless you are after appearance only, you might better concentrate on tailwheel integrity and function. The tailwheel is easier to inspect and maintain with no fairing, in my opinion.

Kent

Kent Hermsmeyer
rkh986@8Lni1Td6ivX5bnmyMePD_KsdhZlds2t8AxA22aLLp5lU4FzW8y1yT8zu4OQDhoZLiFt-psQo4js.yahoo.invalid
rkh986@E1b3ZyKq8qoSDkiKnj5QxFjRkF0cPQ3piN2OuQHzllByww9PTn70xblCgbTJO9hX_06BvZ0QMopv.yahoo.invalid
Portland OR

From: pop hop <philphil_99@BDeJdvePCXFrzS_3HDgBc4dclHjOZk7Tnb13uAJ_bFPwurebcHdKSmAPyEp_QUJws7Or3OC_AyOF7m5cnA.yahoo.invalid>
To: G109_Pilots@yahoogroups.com
Sent: Tue, January 4, 2011 7:14:35 AM
Subject: Re: [G109_Pilots] Re: TM817-48

Great idea assuming the "filler" will hold up.

Also does anyone have a tailwheel fairing on their ship? I see them on some old drawings.
Does it help? Where can I get one?
If none are avail I can make up some molds and fabricate a few for others.

Thanks,
Phil G109B

From: saberraider24 <saberraider24@LWu4_H9pYOVbI2Q5k9k9tKI50gQ1671jus8CtJ2OEffv2dgQz40DVSC0CtvDt-OItkfK9pDuWgLrS3UU.yahoo.invalid>
To: G109_Pilots@yahoogroups.com
Sent: Tue, January 4, 2011 10:04:35 AM
Subject: [G109_Pilots] Re: TM817-48

A much simpler solution and by far superior to the tail wheel fork extension is to simply elongate the axle bolt hole. The required elongation is very slight and does not affect the structural integrity of the fork.

The extension adds significant stress to the mounting plate structure which is already a marginal design.

There are several methods to accommodate the elongation and keep the axle bolt "centered".

1 – Rely on clamping pressure of the axle bolt to keep it from slipping in the elongated hole once installed.

2 – Fabricate a filler for the top portion of the elongated hole

3 - Tack weld a washer on the exterior face of the fork

I will post two pictures of the result

Subject: Re: [G109_Pilots] Re: TM817-48
From: Robertmudd1u@sw5iSZ5XGHdCUuhDEw55aJRCDzh6_lkB-py77jYPU3S7B4IfuwJcFKe3c8hmVhYQmGAYcze8T4yhl0D9.yahoo.invalid
Date: 1/4/11 11:16 PM
To: G109_Pilots@yahoogroups.com

I have been following the discussion about the tail wheel fork extension closely. If your glider is registered in the USA in the Standard Category, as I see from the FAA registry many are, then elongating holes or welding washers on to the fork will invalidate your airworthiness certificate.

If you aircraft is in the Experimental category then, legally, you should be able to get away with it.

In the Standard Airworthiness category If you want what ever advantages that come from extending the forks of the tailwheel assembly then the doing the work and using the parts called for in TM 817-48 is the only legal way to proceed. The parts are available.

If you think your A&P I.A. is not sharp enough to spot the un-authorized mod during the Annual Inspection then you should consider using a higher quality inspector. What else will they miss that could be critical?

I know this stuff is expensive, I order parts for Grobs every week. It pains me to total the costs for the invoices but aviation is not cheap but any measure.

I do not mean to come across as a scolding nag but this is serious business. Mess up the fork and replacing it is most likely your only option as I doubt that Grob will authorize a repair.

I do not normally post to this group but do monitor it, I have learned a lot from it, so in a way I see my advice as giving back. You are obviously a dedicated group of owners, I only want to keep you safe and legal, which I fully understand is not always the same thing.

Robert J. Mudd
A&P I.A, Comm. Pilot Airplane/Glider CFI Airplane/Glider
Composite Aircraft Repair LLC
Grob parts and support
Moriarty New Mexico 87035 USA

Subject: Re: TM817-48
From: "saberraider24" <saberraider24@aL8lYlxipHjzKNttt2B3sJN5xKOt0ger1ItM0vgVS06Itf642bPSj1ABDNqh27y21QKHS7-NdZgAhax9DmF3.yahoo.invalid>
Date: 1/4/11 8:42 AM
To: G109_Pilots@yahoogroups.com

There is very little "slotting" required. It would not even be necessary to use a filler as the normal axle bolt clamping would be totally adequate. The only reason for the "filler" is to preclude the need to "center" the wheel when replacing, probably not a big deal considering how seldom it is removed.I added a few more pictures to aid visualizing the slot.

--- In G109_Pilots@yahoogroups.com, pop hop <philphil_99@...> wrote:
>
> Great idea assuming the "filler" will hold up.
>
> Also does anyone have a tailwheel fairing on their ship? I see them on some old
> drawings.
>
> Does it help? Where can I get one?
> If none are avail I can make up some molds and fabricate a few for others.
>
> Thanks,
> Phil G109B
>

Subject: Re: TM817-48
From: "Ron Lee" <schwenn109b@TnuMp56SgvLRXsBMIq5_CSAmJDYfoOawYWkAtWpQ1hj5ZuVwewo5sEAouPak4rrfdUYfz3WNDdPWBZ9znQ.yahoo.invalid>
Date: 1/4/11 7:11 PM
To: G109_Pilots@yahoogroups.com

I like the idea of using the elongated slot to shift the axle bolt down and rearward. Which of your three methods did you employ? It appears that perhaps you welded the washer in place? How much did you actually shift the centerline of the axle bolt?

It appears that you are also not using the Grob tow bar to move your ship around as I do not see the axle bolt extension on the tail wheel? I have only had my 109B for a short while but find the tow bar a real asset. Is it common to eliminate the use of the axle bolt extension and tow bar, or am I missing something?

Thanks,

Ron

Subject: Re: TM817-48
From: "saberraider24" <saberraider24@NjKGfBdEUZ1q6d-pNSz0-wkIs2REea8TPrL6nyZMEhS2l5OTN51zh5Rk8GjyzibQXjYCY6Ni58e2wGUKlg.yahoo.invalid>
Date: 1/4/11 10:08 PM
To: G109_Pilots@yahoogroups.com

Ron,

I tacked a washer on but I already had the fork on the workbench otherwise I would have simply welded a "Button" on the back side of the washer to locate it in the slot.

A significant advantage to moving the axle location the minimum amount is to minimize the strain on the tail wheel assembly. It has been a while since I modified it and I don't recall the amount moved, but it was about one axle bolt diameter. There was still adequate material on the fork that it would safely retain the axle bolt without welding any material. I only tacked the washer on to provide a fixed location.

To be considered with the other proposed modification using extension plates is the increase in the loading on the mounting plate. The mounting plate laminated into the fuselage is only 16 gauge, 3.5" x 4" with a 2.25" hole in it.

The axle bolt is the original one that was on the plane when I bought it. I have no tow bar but generally only move very short distances on concrete.

Stu

Subject: Re: [G109_Pilots] Re: TM817-48
From: "Fly" <fly@kByTir44oOnt2viFfKAkHteFVEYQKmd1nyEz7gTpg1t2S8nPVVDMVV8F8tGpX2E98Lh7bgDb8vio7o0.yahoo.invalid>
Date: 1/5/11 7:40 AM
To: <G109_Pilots@yahoogroups.com>

Robert
I have been following these conversations myself without being involved, some people like to look for so superficial things having nothing to do withflying the machine
Happy new year
JP

Jean-Pierre C. Ducos
cfig/mg
fly@
210-667-3716

Subject: Re: [G109_Pilots] Re: TM817-48
From: Robertmudd1u
Date: 1/5/11 8:17 AM
To: G109_Pilots@yahoogroups.com

In a message dated 1/5/2011 7:17:49 A.M. Mountain Standard Time, schwenn109b writes:

How long would it take to get this kit? Do you have a copy of the TM in English that you could post?

Thanks,

Ron

I'll check on that today and let the group know as soon as I learn something.

Robert J. Mudd

Subject: Re: TM817-48
From: "Ron Lee" <schwenn109b@6TyMNHdfNJUQrm19jkhwymK4Pkssq-w2RChdD_BFFcgQpmhleJRh4huGRWYB9eVgeGlM4T6mtLayNuYcWBgc.yahoo.invalid>
Date: 1/5/11 7:17 AM
To: G109_Pilots@yahoogroups.com

Robert,

What is the total cost of the Grob extension plates (with shipping, duty, etc)? Do they include the all of the bolts and washers, etc listed in the TM? Do you have one in stock in the US or does it have to come from Grob? How long would it take to get this kit? Do you have a copy of the TM in English that you could post?

Thanks,

Ron