Galenkillam
Member
I will be a newbie to IAC competitions this summer and understand I need drilled bolts with castle nuts on the control surfaces. Can anyone confirm that AND are there any comments about replacing mine on my 8?
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Flight control attachment bolts/nuts?
- Thread starter Galenkillam
- Start date
It's my understanding that if the bolt goes thru something like a rod end bearing, and that the nut can be torques, i.e. the rod end tightens on the mounting ears that a lock nut can be used. If the bolt can actually rotate freely because the install has no bearing surface then the nut cannot be torqued then a castle nut and cotter pin is required. Van's aircraft have some of both installations.
climberrn
Well Known Member
Follow the plans
Was told by the FAA during my inspection that the "standard" used to be castle nuts on control surfaces and linkage, but vans calls out for nylocks in many places. It is best to stick with what the manufacturer calls out.
Of course, if you are the builder, than you can do whatever you want. Would not suggest it though.
Was told by the FAA during my inspection that the "standard" used to be castle nuts on control surfaces and linkage, but vans calls out for nylocks in many places. It is best to stick with what the manufacturer calls out.
Of course, if you are the builder, than you can do whatever you want. Would not suggest it though.
Lucio I-NLCM
Active Member
+ casle
Hi
all my control bars are locked with this: http://www.aircraftspruce.com/catalog/hapages/ms17825.php
I don't want never think about it
here the pitch control idler arm
Hi
all my control bars are locked with this: http://www.aircraftspruce.com/catalog/hapages/ms17825.php
I don't want never think about it
here the pitch control idler arm
This is a bit like primer wars. I know an A&P who won't sign an annual unless all lock nuts are replaced by castelated nuts on drilled bolts with cotter pins. Then again I've seen cotter pins fail.
I thought 43.13 said that if the bolt doesn't rotate a lock nut is appropriate. It's probably a question that is difficult to get agreement on.
I thought 43.13 said that if the bolt doesn't rotate a lock nut is appropriate. It's probably a question that is difficult to get agreement on.
lucaperazzolli
Well Known Member
I choosed MS17825 self-lock castle nut for pitch control line, three small plexy windows (one in the baggage area and two for the elevator horns bolt) complete my pre-flight check.
Pay attention in the central control column where pins may be worse than nothing. Pal nuts (MS27151) are another option (maybe).
MS17825 self-lock castle nut:
There has often been controversy over the requirement for the use of castellated nuts on flight controls and for small airplanes, certified under part 23. 23.607 addresses this. The origin of the rule is all the way back to the CAR's from the 30's. But even better, AC23.607-1 provides more details. Specifically it requires castellated nuts to be used where movement of the joint may result in motion of the nut and or bolt. So the idea is that if there is a solid stack up of the bolt through a bearing, bushing or brackets where the bolt is tightened and no rotation of the bolt (or on the bolt) is intended as a part of the joint design, a castellated nut is not required. In this type of joint rotation occurs on a inner bushing or a spherical bearing, or other bearing and the bolt is through the inner race in a solid stack up. In contrast if the joint is designed to rotate on the bolt so that the bolt itself is actually a moving part of the joint, (rotation of parts relative to the bolt) then a castellated nut is required. The principle concern is that the rotation of the bolt or nut will put enough torque on the nut to loosen a self locking nut.
In helicopters, there is a requirement for double safeties (27.607) that says that if a joint is critical to safety, it must have 2 locking devices. That requirement is driven by vibration (helicopters shake a lot), where it has been found that certain vibratory frequencies will loosen a stop nut and others will break cotter pins, but the 2 frequencies are normally significantly different. So what you find in most helicopters flight controls is the castellated nut with an elastic self locking feature. This often gets confused with the airplane requirement.
In any case, the use of a castellated nut in our airplanes is always OK, but not always required. The use of double locking devices is never required, unless there is some specific environmental issue that would drive that and incorporated into the design. It won't hurt anything to use a double locking nut though.
In helicopters, there is a requirement for double safeties (27.607) that says that if a joint is critical to safety, it must have 2 locking devices. That requirement is driven by vibration (helicopters shake a lot), where it has been found that certain vibratory frequencies will loosen a stop nut and others will break cotter pins, but the 2 frequencies are normally significantly different. So what you find in most helicopters flight controls is the castellated nut with an elastic self locking feature. This often gets confused with the airplane requirement.
In any case, the use of a castellated nut in our airplanes is always OK, but not always required. The use of double locking devices is never required, unless there is some specific environmental issue that would drive that and incorporated into the design. It won't hurt anything to use a double locking nut though.
Raymo
Well Known Member
What RVDan said. I opted to install castellated nuts and cotter pins in all moving control areas.
From 43.13:
7-64. SELF-LOCKING NUTS. These nuts
are acceptable for use on certificated aircraft subject to the aircraft manufacturer?s recommended practice sheets or specifications. Two types of self-locking nuts are currently in use, the all-metal type, and the fiber or nylon type.
a. DO NOT use self-locking nuts on parts subject to rotation.
b. Self-locking castellated nuts with cotter pins or lockwire may be used in any system.
From 43.13:
7-64. SELF-LOCKING NUTS. These nuts
are acceptable for use on certificated aircraft subject to the aircraft manufacturer?s recommended practice sheets or specifications. Two types of self-locking nuts are currently in use, the all-metal type, and the fiber or nylon type.
a. DO NOT use self-locking nuts on parts subject to rotation.
b. Self-locking castellated nuts with cotter pins or lockwire may be used in any system.
On most of the bolts holding the surfaces on the access is limited. Putting the nuts and washers is difficult. I can't imagine trying to get my fingers in there to safety wire all those nuts.
Good practices to follow, but as already mentioned (numerous times) most of the fasteners in the control system or used to attach the control surfaces on RV's are not subject to rotation. The ones that are (such as clevis ends on rudder cables) specifically specify cotter saftied bolts.
There is a location on a couple of models where bolts as designed aren't subject to rotation but sometimes people don't torque fully because depending on the level of fit precision in the bushing, fully torquing can induces system friction (the bolt for the control stick pivot bushing is one I can think of right now) so castellated nuts are specified on those.
Other than a few places, all other control system related fasteners get fully torqued; clamping a bushing, bearing, or rod end ball, where something else rotates around it. There is nothing rotating on the bolt it self (that is what subject to rotation means).
If builders feel better about having cotter safetied bolts, go for it (but it is not necessary for good safety nor is it "more correct" from a standard practices standpoint).
Just keep in mind that in some circumstances, a cotter safetied bolt can actually be less safe because the cotter pin can be vulnerable to damage (being accidentally opened up by a rag snagging on it while washing, etc.)
Last edited:
