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GSC prop torque service bulletin

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Jeffrey Dill

Joined: 23 Jul 2007
Posts: 52
Location: Pleasant view, TN

Posted: Wed Oct 27, 2010 8:33 pm Post subject: GSC prop torque service bulletin

I am having to replace a 2 blade - 68" GSC prop because I cannot reach torque without the hubs coming together. A gap between the hubs is mandated by a 1999 GSC service bulletin. I got this prop from a high school with less than 5 hours on it. I suppose there is quite a risk that they over-torqued it at some point. Rick, at GSC said I could mill the hubs if I was sure the prop was never over-torqued, but I am not. I am sure I torqued it correctly when I installed it, with a gap in the hub. At condition inspection a year and 20 hours later, the bolts were loose; and when re-torqued, I could no longer get a feeler gage between the hubs. I would like to hear speculation about what happened. Has anybody had the same experience? Torque is supposed to be 75 - 100 inch-lbs; I think I will torque the new prop on the lower end of that range.

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Jeff Dill
Model 2

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Thu Oct 28, 2010 4:41 am Post subject: GSC prop torque service bulletin

Jeff,

  If it was my prop I would take the hub to a machine shop and have the  hub halves "flat plated" (milled) a small amount in order to allow more room  between the halves for torquing the prop (per the mfg recommendation). Also make  sure you are using new prop bolts !

  I am not that familiar with the GSC as I am using the Kiev,but as I  understand it, it is wood. Wood "moves" more than carbon fiber ,composites etc.  You will have to re torque more often with a wood prop. I have had to do that  with every wood prop I have owned (and that's a bunch !)

                                              Dick Maddux

                                              Fox4

                                              Milton,Fl

  

 [quote][b]

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Thu Oct 28, 2010 4:54 am Post subject: Re: GSC prop torque service bulletin

I've had my 3-blade GSC for 20 years.  A couple of years ago, I re-torqued the bolts and also didn't have a gap. Sent the blades to GSC and they inspected and re-balanced them after which I sanded off about .004 inches from the faces of the hub using a belt sander and everything has held together just fine since.



My take on it is that there's no way to tell whether the wood that's inside the neoprene sleeves at the roots of the blades has been crushed by over torquing although I was the original owner of my prop and knew it's history.  GSC's inspection was nice peace of mind though.



Having said that, not knowing the history of yours is the primary problem and by strict logic should be grounds for not trusting it. 



Chris

Model 2, 582, C box, GSC 66" 3-blade

Sioux Falls, SD

Jim Feldmann

Joined: 01 Sep 2008
Posts: 54
Location: Burbank, CA

Posted: Thu Oct 28, 2010 8:02 am Post subject: Re: GSC prop torque service bulletin

I purchased a Kitfox IV with a two year old GSC three blade prop.  The hubs came together at just under 100 in/lb.  After researching the problem, I had the hubs milled .005, then torqued the bolts to 80 in/lb, which left a .010 gap.



Approximately 15 hours later, all three blades departed the airplane in flight.  The resulting off-runway landing resulted in no injuries, although the airplane was destroyed.  The NTSB examined the prop, including all three blades, and found no anomalies.  Their conclusion was that it may have been over-torqued at some time in the past.



I STRONGLY recommend that you DO NOT attempt to save that prop.



Jim

Last edited by Jim Feldmann on Thu Oct 28, 2010 9:39 am; edited 1 time in total

Jeffrey Dill

Joined: 23 Jul 2007
Posts: 52
Location: Pleasant view, TN

Posted: Thu Oct 28, 2010 9:29 am Post subject: Re: GSC prop torque service bulletin

Thanks to all. Fortunately my birthday is coming up soon.

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Jeff Dill
Model 2

kerrjohna(at)comcast.net
Guest

Posted: Thu Oct 28, 2010 9:46 am Post subject: GSC prop torque service bulletin

recently decided that the 500 hour/5 year replacement limit from GSC should be applied to the 800+ hour/12 year old 3-blade.  Keeping the original hub, the replacement cost was about half the cost of original. 

  

peace of mind-priceless. 

  

John Kerr 

Kitfox Classic IV, 912ul 



---

taildragon(at)msn.com
Guest

Posted: Thu Oct 28, 2010 12:53 pm Post subject: GSC prop torque service bulletin

Where are you getting these numbers? Do they apply equally to a hangared plane in CA as well as an unhangared plane in NY?

Date: Thu, 28 Oct 2010 17:43:18 +0000

From: kerrjohna(at)comcast.net

To: kitfox-list(at)matronics.com

Subject: Re: Kitfox-List: Re: GSC prop torque service bulletin

   .ExternalClass p {;} recently decided that the 500 hour/5 year replacement limit from GSC should be applied to the 800+ hour/12 year old 3-blade.  Keeping the original hub, the replacement cost was about half the cost of original.

 peace of mind-priceless.

 John Kerr

 Kitfox Classic IV, 912ul

---

kerrjohna(at)comcast.net
Guest

Posted: Thu Oct 28, 2010 2:11 pm Post subject: GSC prop torque service bulletin

the numbers came from the GSC site.  I rationalized along the same lines you are questioning and after near doubling the recommended life decided to make the change a quit thinking about it.  I have a set of really good used blades that have alway been hangared for anyone who wants to roll the dice. 

  

  

John Kerr

---

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Oct 28, 2010 5:01 pm Post subject: Re: GSC prop torque service bulletin

First off I like GSC props and on the 582 they work pretty close to any IVO or Warp all properly set. On the 912 I find the IVo kicks the GSC in the rear. 



I have thousands of hours to back up my statements. 



GSC- DO NOT screw around milling the blocks - They get old and fatigue like all of us.  Most GSC damage comes from OVER -TIGHTENING. 



BUT they do rot and get weak, some more than others. 



Here is one that WAS NOT Over tightened. 

http://www.cfisher.com/gsc/



New blades are cheap - DO not screw around. Most of us have little troubles if common sense is used.

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napierm(at)cisco.com
Guest

Posted: Mon Nov 01, 2010 7:11 am Post subject: GSC prop torque service bulletin

Only reason I would stick with that GSC prop is if I had the 582 with

the 3:1 gear box.  That is a great prop for that combo.  Even then

*replace* the blades.



Otherwise....



Mark Napier

Time: 09:05:21 AM PST US

Subject: Re: GSC prop torque service bulletin

From: "Jim Feldmann" <feldesign(at)earthlink.net>

I purchased a Kitfox IV with a two year old GSC three blade prop.  The

hubs came

together at just under 100 in/lb.  After researching the problem, I had

the

hubs milled .050, then torqued the bolts to 80 in/lb, which left a .010

gap.



Approximately 15 hours later, all three blades departed the airplane in

flight.

The resulting off-runway landing resulted in no injuries, although the

airplane

was destroyed.



I STRONGLY recommend that you DO NOT attempt to save that prop.



Jim

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