Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Torque Values Variations.  
User currently offlineHAWK21M From India, joined Jan 2001, 31875 posts, RR: 54
Posted (10 years 11 months 3 weeks 1 day 5 hours ago) and read 2969 times:

On the Bolt-Nut Assy for the JT8Ds at the FCU Cross shaft to Start/Thrustr Cable attachment.The AMM states if a Locknut is used the Torque values of Bolt A is 50-70lb in[pound inch] & Bolt B is 100-140 lb in.
Whereas if a Castellated Nut is used the Torque Values reduce to 30-40 lb in & 60-85 lb in resp.
The question is Understandably that the Second method has a Split pin for added safety but why should the Torque values differ.
How is it determined that lower values will be needed for the Second method.

Think of the brighter side!
5 replies: All unread, jump to last
User currently offlineNORTHSEATIGER From United Kingdom, joined Sep 2003, 432 posts, RR: 4
Reply 1, posted (10 years 11 months 3 weeks 1 day 4 hours ago) and read 2958 times:

I would think that the higher torque will be to "run down" the lock nut which I would imagine will be either eliptical or have a nylon coating, so the extra tq will deform the nut/cut the nylon and ensure the correct tq and locking where as with the split pin the tq is applied then the pin put through for safety.

Regards NST

T's And P's look good....Rotate
User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 11 months 3 weeks 20 hours ago) and read 2897 times:


Quite simply the cotter key takes the place of the torque. As you know, the property of elasticity is what allows fasteners such nuts, bolts, screws, etc. to hold, in conjunction with the locking system used, when torqued to the appropiate value. When using a cotter key we do not need to torque anymore than that required to bring the components together, unless the AMM calls for anything different.

In fact I know of one application where the torque is zero. On the CFM56 the VBV feedback cable is attached to the MEC with a bolt, nut washer and cotter key. There is a line item step to inspect that the nut/bolt assy is free to turn by hand.

User currently offlineHAWK21M From India, joined Jan 2001, 31875 posts, RR: 54
Reply 3, posted (10 years 11 months 3 weeks 6 hours ago) and read 2873 times:

Quoting Air2gxs (Reply 2):
There is a line item step to inspect that the nut/bolt assy is free to turn by hand.

Why provide Zero Torque.

Think of the brighter side!
User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 4, posted (10 years 11 months 2 weeks 5 days 21 hours ago) and read 2832 times:

In this particular application (VBV feedback), you want the fastest and most accurate response to the position of the VBV's, especially when moving into reverse. The zero torque allows an almost frictionless connection.

User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 5, posted (10 years 11 months 1 week 5 days 6 hours ago) and read 2778 times:

You have friction in the locking in the lock nut, which reduces the torque actually working to put traction on the bolt.

Compare it with wet and dry torque. If you use oil when tightening, you need less torque as less is being used to overcome friction. It is a common pitfall to put a bit of oil on when tightening a nut which is supposed to be tightened dry and has a torque specified accordingly. There you are left staring at your stripped (but well oiled) threads and wondering what just happened.


I thought I was doing good trying to avoid those airport hotels... and look at me now.
Top Of Page
Forum Index

Reply To This Topic Torque Values Variations.
No username? Sign up now!

Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)

Similar topics:More similar topics...
Electric Motors And Torque posted Thu Jun 16 2005 03:13:04 by 2H4
Torque Checks posted Mon Apr 25 2005 12:31:26 by NORTHSEATIGER
Turbofan "Negative Torque"? posted Sat Oct 16 2004 20:19:09 by Francoflier
Aircraft Tugs: How Much Horsepower/torque? posted Mon Apr 5 2004 06:58:23 by Aguilo
Type Ratings, The Values... posted Sun Sep 21 2003 05:09:36 by Tarzanboy
Handy Bolt Torque Program posted Fri Mar 29 2002 20:48:02 by TechRep
Torque Vs RPM posted Sat Jul 21 2001 13:11:41 by Diego
B767 FMC Cost Index Values... posted Sat Jun 14 2003 22:59:41 by Windshear
MD-11 Performance Variations posted Sat Nov 3 2001 21:40:36 by VASI
Startup Torque posted Tue May 29 2001 01:40:55 by A/c train

Sponsor Message:
Printer friendly format