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Bent Elevator Rod End


youngmic

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Hi All,

 

Thought I'd post this as a heads up to other VE owners.

 

Aircraft Details:

 

Plans built VE standard configuration

1050 hrs TT

First flew 1987

3rd Owner 750 hrs on type (This one)

 

During an avionics up grade (to Dynon) I took the time to disasemble the control circuit through the cabin area for inspection, this may well be the first time some of the rod ends have been detached since being built, as they are difficult to remove but appear easy enough to visualy inspect and grease in situ.

 

All are HM 3 rod end spherical bearings except the rod end bearing at the elevator which is a HM 4. I suspect this was done as called for by RAF years ago in light of a bent rod end discovered as a result of rough handling during rigging.

 

I discovered damage to rod end bearings as follows:

 

The elevator HM 3 bearing at the control stick, this is the elevator push rod from stick to forward bellcrank. This HM 3 bearing was bent approx 5 degrees at the base of the male thread, also the 3/16 attach bolt was bent 7 degrees.

 

The HM 3 at the other end of the push rod ie. at the bell crank end was undamaged except for a slight tight spot in the bearing itself.

 

All other rod ends, torque tubes, push rods, bellcranks and attach bolts in good condition.

 

My aircraft has always suffered a lack of trim range in pitch, ie. full back trim will trim to only 95 knots and full forward trim to about 150 knots.

 

This means during approach I am holding some back pressure, perhaps as much as 2 kg (4.5 lbs) and during rain whilst flying at 100 kts maybe double and more again whilst on approach in rain.

 

It appears the angular relationship of the push rod from control stick to bellcrank is such that the force between the stick and the elevator can be multiplied many times. The 3/16 bolt needs many hundreds of pounds to yield in the mode/manner it has.

 

I will be correcting this trim problem before further flight in the hope that this is the root cause of the problem.

 

I would strongly suggest that anyone flying with a similar trim issue or has HM 3 rod ends still in the circuit to inspect very carefully, I only noticed mine when I actually dissasembled the rod end from the stick. The inspection should also extend to the security of the trim springs, how many owners replace a trim spring when they look externally fine, none I suspect. Talking to a spring manufacturer recently revieled a lot I was unaware of regarding spring manufacturing techniques and the effect on longevity. Suffice to say I will be looking at custom built high quality springs for the trim system.

 

It is hard to be critical of Burts design but it does appear that the design is such that if a nose up extension spring in the trim system failed that the force generated at the stick to over come the elevator forces could be such that the control circuit would most likely be overloaded. Perhaps even with HM 4 rod ends installed.

 

It goes without saying that a rapid negative G pitch forward close to the ground following a failure of a rod end could be catastrophic.

 

I would be very interested to hear the thoughts of others on this matter.

 

I would have liked to post this on the EZ squadron sight as well but since the sight upgrade awhile back I have been unable to log on or contact anyone who can assist. Any one who could help me out with a direct email address to a moderator, I'd be grateful.

 

Regards

Mick Young

Australia

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  • 4 weeks later...

I'm a relatively new owner of a VE. I've had it about 3 years and never flown it. It originally had a RW-100 engine in it and I couldn't come up with the courage to fly it. I put in a new C-85 stroker in it last month and finishing up a few things.

 

My question is. Do ALL the heim joints (HM-3) need to be replaced in the plane or just the elevator?

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Appearantly the bending and possible breakage of these bearings caused the change to -4s. Probably some broke.

 

These are not very important bearings, heck in a cozy, if one breaks you can always reach over to the other side for elevator control. If it Jambs, you won't need to reach at all.

 

In Summary-------------

 

CHANGE ALL TO -4S:irked:

I Canardly contain myself!

Rich :D

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