Tip: Cotter Pins - Am I the only one who didn't know this?

Nearly 50 hours on the Rocket, weather is lousy so a good time to do a full inspection. One of the things I found involved my rudder pedals. These run VERY close to the center tunnel. The bolt that pivots the bottom of the brake cylinder has to be installed with head toward the center tunnel and the castle nut and cotter pin inside the rudder pedal - where your foot could rub against it. During the inspection the cotter pin was found to be somewhat straightened out giving rise to the potential of it falling out. Today I was discussing this with the local AME (A&P in the USA) and he showed me a way to bend the cotter pin so my foot would not catch it. I thought this was a bit novel so I showed it to one of the other hangar rats, but it was nothing new to him.

Apparently this is standard practice in some circles. Maybe everyone knows this and I am just the last one to find out!

Anyway, in the picture below you can see how he locked the pin into the nut, and nothing is sticking out past the end of the bolt for my foot to catch.

This is "new to me" so THANKS!

It is know as the "French Curl" or at least that was what I was taught long ago.

Check with F1 boss. There was an early service bulletin about special bolt and procedures for the rudder pedals.

From you post it sounds like you are getting close to having the problem that the service bulletin addresses.

My pedals hung up shortly after a landing. 10 seconds sooner and it probably would have destroyed the plane.

When I had my airworthiness inspection the FAA guy showed me this trick.

From "DocThrocks" website

rudderpedalsinstalled3.jpg



**Service Bulletin: 8/05 a service bulletin was issued by TR to ensure adequate clearance between the outside lower brake pedal to rudder pedal attach bolt. It seems there have been problems with the bolt head hanging up on the firewall and disallowing full travel of the pedals. This could be an extremely dangerous situation in the air, and especially on the ground. It is recommended that you have at least 1/4 inch clearance between the bolt head and the firewall. Some builders have simply ground the bolt head down or used a pan head bolt, as well as taking a ball peen hammer to the firewall footwell junction and knocked it back. It has also been recommended that prior to pedal assembly that the rudder pedal cross tubing (horizontal part) be cut from the upright thin hangar, and reduced 1/4 inch. Then you can insert a spacer and shift the outboard part of the mechanism away from the firewall footwell and gain adequate clearance. It has also been recommended that if you cut this part to shorten it, when you re-weld the part it's a good idea to slightly rotate the flat upright so that the horizontal cross tube of the left and right rudder pedals are parallel.

*** Update 12/07:
Although I thought just changing the screw on the rudder pedal that was hanging up on the footwell would solve the problem, it DID NOT. I was taxi tesing my Rocket and the right pedal was hanging up badly on the lip of the footwell. Malletizing it just wasn't going to happen. So instead, I got a nice long thick bolt and nut, and a deepwell socket. I used the socket/bolt combination as a jack screw. I blocked the inboard side of the footwell with some wood, and then drove the head of the bolt into the area of the stainless firewall where the hang up was and dented it out. Not a very sophisticated method, but screwing the bolt out of the socket and bending the footwell about 1/8 inch or so gave plety of clearance. The tendency for your legs at an outboard angle and the pedals swinging at an outboard angle will predispose you to hanging up on that brake pedal screw at absolutely the wrong time. Go ahead and bend out the lip of the firewall footwell adjacent to that screw. Thank me later!

I used a pan head screw (actually a bolt). There is NOT enough clearance as is, even with the pan head. You can see in the pic that there is not much clearance. If you assemble the rudder and brake pedal assemblies trying to bias everything inboard, you should be able to get at least the amount of clearance shown. Mark recommends perhaps twice this much, which would mean cutting and welding the pedal and perhaps reshaping the brake pedal. If that bolt hangs up, you can get in some serious trouble! I went ahead and dented out the stainless firewall adjacent to the pan head.

I like it!

I did not know either, but I like the way it is contained!

Something new learned today, something useful.

Thanks!

Milt, thanks for posting that potential issue. The nut where I was catching my foot on the cotter pin is the one in the picture below. If the cotter pin fell out and the nut backed off, then the bolt could hang up on the side of the tunnel. If the bolt disengaged from the pedal then I would lose that brake.

This was a problem with the RV4 and is listed here in the SBs

http://www.vansaircraft.com/pdf/sb96-12-1.pdf

I use the .040 safety wire option and it has served well on all my aircraft.
Also there is a castlelated locknut available that I use in locations like this and at the rudder horns/ rudder cable location as an added level of security.

The loss of the cotter pin is not only a possibility, but real.
I noticed my flying shoes had a peculiar wear on the outside of the sole. During the night BEFORE a flight it came to me in my sleep.
Sure enough the cotter pin had come out, the nut unscrewed, and the bolt was simply dangling.
I now have turned the bolt facing out, and include it in my pre-flight.
No harm/no foul.

Daddyman

Tom Martin said:

This was a problem with the RV4 and is listed here in the SBs

http://www.vansaircraft.com/pdf/sb96-12-1.pdf

I use the .040 safety wire option and it has served well on all my aircraft.
Also there is a castlelated locknut available that I use in locations like this and at the rudder horns/ rudder cable location as an added level of security.

Click to expand...

3. Use .040 safety wire rather than a cotter pin. Safety wired as shown will prevent the castle nut from turning, will prevent the clevis bolt itself from rotating, and is less exposed to pressure from the pilot's show because there are no exposed ends as is the case with cotter pins.

Is there a missing picture? I can't find an "as shown" in Vans link.

I have seen a similar method used on backcountry planes. I was told it was a helicopter method on installing cotter pins.

I used .040 safety wire on my F-1. I pay extra special attention to the brake and rudder connections prior to every flight on taildraggers.

SMO said:

Maybe everyone knows this and I am just the last one to find out!

Click to expand...

Second to the last

040 safety wire

Does anyone have a pic to post of a properly saftied castle nut?

SMO said:

Click to expand...

This is the standard (and expected) method to bend cotter pins in my workplace. Also an acceptable alternate method per the Bell Helicopter Standard Practices Manual (BHT-ALL-SPM).

In the helicopter world, it makes reaching into a forest of control tubes & bellcranks a less-dangerous environment - there's fewer chances of getting hooked like a fish on a cotter pin leg. I've got several scars on my hands, wrists, and forearms from 20+ years of this...