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Condition Inspection Questions from an A&P

Champ837

I'm New Here
I'm doing a condition inspection on a 9-A and see a note in the log from a previous inspection that the break-away of the nose wheel was checked. I'm familiar but don't know this particular procedure or how much force is needed and where it's measured from. Photos if possible. Can someone share and enlighten me.
 
Construction manual from a 7 (I think it's the same for 9) - Section 10 -

SETTING THE BREAKOUT FORCE OF THE NOSEWHEEL

When installing the nose wheel/fork assembly for use, tighten the nut down so it requires 14 ft/lbs of torque to swivel the fork on the axle. Measure this by rigging a small tension scale (like a fish scale) to pull in-line with the axis of the axle. DWG C1 shows this arrangement. Progressively tighten the axle nut while swiveling the fork and taking readings with the scale as the ‘‘break out’’ force increases. When the scales measure 22 pounds, temporarily safety the axle nut. Swivel the fork several times from stop to stop. Measure the pull both to the right and to the left. Be sure the scale is perpendicular to the wheel when pulling. If the sale reading varies significantly from one direction to the other, re-adjust the axle nut as required.

After the breakout force is correct, drill the gear leg for the cotter pin with the nut in place. You can drill from each side. Start with a drill that just fits the slot in the nut and drill just deep enough to get a drill point started. Then switch to the correct drill size for the cotter pin.​

Dan
 
The RV-9/9A plans list a break out force, the owner may have these plans or you can get a plans CD from Vans. As an A&P maintaining several RVs, I went ahead an bought CDs for the 6, 8, 9. I would have to check the plans documents, but I believe the break out force should be in the 22-24 lbs range. The plans show how to measure it. The break out force is crucial in preventing nose wheel shimmy. There are several key inspections that need to be done on the A models pertaining to nose wheel. Make sure the tire pressure and wheel bearing drag forces are correct. If in doubt, search the VAF forum for info. Another inspection is to jack up the nose wheel and check the gear leg attachment bolt on the engine mount for looseness.
 
Construction manual from a 7 (I think it's the same for 9) - Section 10 -

SETTING THE BREAKOUT FORCE OF THE NOSEWHEEL

When installing the nose wheel/fork assembly for use, tighten the nut down so it requires 14 ft/lbs of torque to swivel the fork on the axle. Measure this by rigging a small tension scale (like a fish scale) to pull in-line with the axis of the axle. DWG C1 shows this arrangement. Progressively tighten the axle nut while swiveling the fork and taking readings with the scale as the ??break out?? force increases. When the scales measure 22 pounds, temporarily safety the axle nut. Swivel the fork several times from stop to stop. Measure the pull both to the right and to the left. Be sure the scale is perpendicular to the wheel when pulling. If the sale reading varies significantly from one direction to the other, re-adjust the axle nut as required.

After the breakout force is correct, drill the gear leg for the cotter pin with the nut in place. You can drill from each side. Start with a drill that just fits the slot in the nut and drill just deep enough to get a drill point started. Then switch to the correct drill size for the cotter pin.​

Dan

The owner isn't the builder. He has the plans but hasn't studied nor have I. Is the point you pull from, the wheel axle?
 
Construction manual from a 7 (I think it's the same for 9) - Section 10 -

SETTING THE BREAKOUT FORCE OF THE NOSEWHEEL

When installing the nose wheel/fork assembly for use, tighten the nut down so it requires 14 ft/lbs of torque to swivel the fork on the axle. Measure this by rigging a small tension scale (like a fish scale) to pull in-line with the axis of the axle. DWG C1 shows this arrangement. Progressively tighten the axle nut while swiveling the fork and taking readings with the scale as the ??break out?? force increases. When the scales measure 22 pounds, temporarily safety the axle nut. Swivel the fork several times from stop to stop. Measure the pull both to the right and to the left. Be sure the scale is perpendicular to the wheel when pulling. If the sale reading varies significantly from one direction to the other, re-adjust the axle nut as required.

After the breakout force is correct, drill the gear leg for the cotter pin with the nut in place. You can drill from each side. Start with a drill that just fits the slot in the nut and drill just deep enough to get a drill point started. Then switch to the correct drill size for the cotter pin.​

Dan

Once set and drilled. does it vary much over time? If it's drilled and pinned, is it changed easily?
 
The RV-9/9A plans list a break out force, the owner may have these plans or you can get a plans CD from Vans. As an A&P maintaining several RVs, I went ahead an bought CDs for the 6, 8, 9. I would have to check the plans documents, but I believe the break out force should be in the 22-24 lbs range. The plans show how to measure it. The break out force is crucial in preventing nose wheel shimmy. There are several key inspections that need to be done on the A models pertaining to nose wheel. Make sure the tire pressure and wheel bearing drag forces are correct. If in doubt, search the VAF forum for info. Another inspection is to jack up the nose wheel and check the gear leg attachment bolt on the engine mount for looseness.


Is there a jack point under the fuselage?
 
Once set and drilled. does it vary much over time? If it's drilled and pinned, is it changed easily?

The nosewheel uses a castellated nut to adjust the breakout tension. It should be checked yearly as the belville washers can wear. Also the nose fork has a zerk fitting for grease.


Is there a jack point under the fuselage?
I use weights on the rear tiedown to pull the nosewheel up.
 
First, good for you in coming to a great resource like VAF. But, would you do a 100 hrs inspection on a certified airplane without a maintenance or parts manual? Hopefully not.

For amatuer builts, the maintenance manual and parts manual are replaced by the kit instructions and print package. You need them to have some idea how to maintin the aircraft. Even then homebuilders will deviate from the plans. At that point it is up to you to have enough understanding of the airplane construction and systems to properly and safely maintain the airplane, including performing the condition inspection.

No harm in asking here though, but know the free advice is sometimes very good and sometimes not so good.
 
The nosewheel uses a castellated nut to adjust the breakout tension. It should be checked yearly as the belville washers can wear. Also the nose fork has a zerk fitting for grease.



I use weights on the rear tiedown to pull the nosewheel up.

I did and it worked quite well. I'm seeing your note now after I finished doing it this morning. I checked the friction and it was good too. While looking things over and remembering what someone else mentioned about checking the nose strut bolt at the top of the strut, I noticed that the bolt must have been installed before the engine mount was attached to the firewall as one could not remove the bolt as it would hit the firewall. It was installed from the bottom with the nut on top. I guess if it ever needs replacing it must have the head cut off first. Thanks!
 
ThE plans for the RV-6a have the bolt installed the same way. A hole is cut in the firewall so you can remove the bolt in the future. A plug is installed in the hole to cover it.
 
I have a comment about the nose gear leg and the bolt that retains it in the motor mount sleeve. Sometimes, a hole in the firewall adjacent to the bolt head is made to insert the bolt into the sleeve and leg component from the pax side of the firewall. The hole is then sealed with a snap button and RTV. You might want to double check for that snap button mod before attempting to cause hacksaw failure of that bolt in future inspections. Dan
 
That bolt on the nose gear leg

For a proper condition inspection the nose gear leg should be removed and the bearing surfaces cleaned and re-greased. The bolt does install up from the bottom per the plans. The bolt washer and nut should be replaced with new. The plans call out the hole in the firewall and to use a metal closure. There is obviously a torque requirement. The gear leg gets a fair amount of lateral loading which tends to wear the bolt and washer. If the bolt gets loose the gear leg can rotate in the mount causing the thru hole to elongate.

Was this your first condition inspection on an RV? There is a SB for the nose gear fork. Confirm that the SB has been accomplished

The jack points are the wing tie down points with a proper support bolt in the tie down threaded fitting. The tail will require a tie down or weight to support the nose.

Tyler
Builder N174MT, A&P
 
Remove nose gear????

For a proper condition inspection the nose gear leg should be removed and the bearing surfaces cleaned and re-greased. The bolt does install up from the bottom per the plans. The bolt washer and nut should be replaced with new.

Tyler
Builder N174MT, A&P

Do you really remove your nose gear leg at every annual? Is this for just -6A's or for all A models? Yes, you need to check torque on the bolt (nut) but remove the leg just to grease the mating surface?
 
For a proper condition inspection the nose gear leg should be removed and the bearing surfaces cleaned and re-greased. The bolt does install up from the bottom per the plans. The bolt washer and nut should be replaced with new. The plans call out the hole in the firewall and to use a metal closure. There is obviously a torque requirement. The gear leg gets a fair amount of lateral loading which tends to wear the bolt and washer. If the bolt gets loose the gear leg can rotate in the mount causing the thru hole to elongate.

Was this your first condition inspection on an RV? There is a SB for the nose gear fork. Confirm that the SB has been accomplished

The jack points are the wing tie down points with a proper support bolt in the tie down threaded fitting. The tail will require a tie down or weight to support the nose.

Tyler
Builder N174MT, A&P

Yes, this is my first RV inspection. Since posting my observation about the gear leg bolt I've gotten a number of answers pointing me to the drawing that shows how it's done. Thanks. I'll check on the SB.
Where do I find the criteria for determining the condition of the previously mentioned nose gear bolt. There is a very slight side to side movement of the strut shaft and I can see the bolt move slightly.
 
I have no advice to offer re: your nose wheel inquiry, but would like to applaud your conscientious approach to conducting a thorough inspection.

A&Ps such as this gentleman do us all a favor by being willing to work with homebuilt aircraft. I have several friends who would like to own an RV, but are concerned that they won't be able to find a mechanic who's willing to work on it and/or inspect it when necessary.

Kudos sir!
 
ThE plans for the RV-6a have the bolt installed the same way. A hole is cut in the firewall so you can remove the bolt in the future. A plug is installed in the hole to cover it.

Tom is correct, but it was not always this way.
When the RV-9A was introduced in the late 90's this was a standard part of the kit and it was incorporated into the RV-6A at that time.
Any RV-6A built prior to then probably does not have the access hole in the firewall.

If the RV-9A being inspected was built per plans, it will have a hole in the firewall that would allow the bolt to pass through the firewall while removing or installing it.
 
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There is a very slight side to side movement of the strut shaft and I can see the bolt move slightly.

There is no published criteria, but any movement of a major structural member like a nose gear leg is not good.

If the movement is very slight, it is not necessarily a safety of flight issue at this point, but once movement is happening, it will only get worse and likely become more difficult to correct.

Sometimes it can be resolved with a new bolt (close tolerance may help if regular bolt is still loose). If that doesn't do it then a tapper pin is an option.

Doing a condition inspection on an RV should of course include researching compliance with Service Bulletins, but a loose nose gear leg warrants taking a specific look at THIS ONE.
 
Where do I find the criteria for determining the condition of the previously mentioned nose gear bolt. There is a very slight side to side movement of the strut shaft and I can see the bolt move slightly.

Any movement is call for investigation. There can be no play in the socket or the bolt.

Here is how I test mine... With the nose wheel holding it's normal weight, place your finger on the top of the leg and the top of the socket. Gently create a side load by pushing on the motor to rock the nose left and right and feel for any movement. Place your finger on the bolt and repeat.

The bottom of the gear mount can be checked by thumping the gear leg just above the bend. With the faring off and the wheel clear of the ground, give the gear a good thump with your fist..... you will hear any play.

When you replace the bolt, make sure the shank extends beyond the mount wall. Measure the bolt and you will find that the bolt tapers just before the threads. That will cause play. I had to go to the next longer and added an extra washer under the head to come out just right.

My bolt is installed from the top. It was replaced without too much effort. I do not remove the leg during my annual inspection.
 
For a proper condition inspection the nose gear leg should be removed and the bearing surfaces cleaned and re-greased.
Tyler
Builder N174MT, A&P

Really! Guess I haven't been doing a "proper" condition inspection all these years. Would it be safe to assume that you also remove the main gear legs for greasing?

I think it great if you elect to do that on your own aircraft every year but I've not heard of or seen any reason to perform that task on an annual basis on a typical RV.
 
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Any movement is call for investigation. There can be no play in the socket or the bolt.

Here is how I test mine... With the nose wheel holding it's normal weight, place your finger on the top of the leg and the top of the socket. Gently create a side load by pushing on the motor to rock the nose left and right and feel for any movement. Place your finger on the bolt and repeat.

The bottom of the gear mount can be checked by thumping the gear leg just above the bend. With the faring off and the wheel clear of the ground, give the gear a good thump with your fist..... you will hear any play.

When you replace the bolt, make sure the shank extends beyond the mount wall. Measure the bolt and you will find that the bolt tapers just before the threads. That will cause play. I had to go to the next longer and added an extra washer under the head to come out just right.

My bolt is installed from the top. It was replaced without too much effort. I do not remove the leg during my annual inspection.

Thanks, Your detail is what I was looking for. Please explain "When you replace the bolt, make sure the shank extends beyond the mount wall." The shank being the smooth part of the bolt or the grip length. This should be exposed past the engine mount sleeve so that the smooth part of the bolt not the threaded part is in contact with the engine mount sleeve, RIGHT?

In another post someone mentioned this bolt/nut being torqued, is it and what is the torque?
 
Thanks, Your detail is what I was looking for. Please explain "When you replace the bolt, make sure the shank extends beyond the mount wall." The shank being the smooth part of the bolt or the grip length. This should be exposed past the engine mount sleeve so that the smooth part of the bolt not the threaded part is in contact with the engine mount sleeve, RIGHT?

In another post someone mentioned this bolt/nut being torqued, is it and what is the torque?

Right.

It is an AN bolt, torque per proper specs for that size AN bolt. The nut is just to keep the bolt from falling out of the hole.....
 
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Oversize bolt option

If replacing the bolt on the upper nose wheel does not remove all the slop, you could replace it with a 1 oversize NAS bolt. Any movement is too much. The reamer was pricey, but better than a prop strike if that bolt fails! Genuine Aircraft Hardware out of California was very helpful in finding the right part. Have the part numbers at the hangar if interested.
 
There is no published criteria, but any movement of a major structural member like a nose gear leg is not good.

If the movement is very slight, it is not necessarily a safety of flight issue at this point, but once movement is happening, it will only get worse and likely become more difficult to correct.

Sometimes it can be resolved with a new bolt (close tolerance may help if regular bolt is still loose). If that doesn't do it then a tapper pin is an option.

Doing a condition inspection on an RV should of course include researching compliance with Service Bulletins, but a loose nose gear leg warrants taking a specific look at THIS ONE.

Thanks for including the link to the SB. I had already finished the nose wheel servicing and checking the break away force and lubing the fork pivot. I'd looked at the pivot stop mechanism but thought nothing of the orientation of the stop arms. It WAS backward.
 
A backwards stop brackets causes much higher twist loads on the nose gear during sharp turns. This alone can cause a loose bolt.

A good condition inspection includes researching AD's and SB's that might be applicable/beneficial. I suggest you search the Van's web site for others that might apply to the airplane you are inspecting.
 
Any movement is call for investigation. There can be no play in the socket or the bolt.

Here is how I test mine... With the nose wheel holding it's normal weight, place your finger on the top of the leg and the top of the socket. Gently create a side load by pushing on the motor to rock the nose left and right and feel for any movement. Place your finger on the bolt and repeat.

The bottom of the gear mount can be checked by thumping the gear leg just above the bend. With the faring off and the wheel clear of the ground, give the gear a good thump with your fist..... you will hear any play.

When you replace the bolt, make sure the shank extends beyond the mount wall. Measure the bolt and you will find that the bolt tapers just before the threads. That will cause play. I had to go to the next longer and added an extra washer under the head to come out just right.

My bolt is installed from the top. It was replaced without too much effort. I do not remove the leg during my annual inspection.
Is there any problem with installing the bolt from the top? I purchased my RV-9A used and no hole is drilled for the gear bolt to be installed as the plans show.
 
Is there any problem with installing the bolt from the top? I purchased my RV-9A used and no hole is drilled for the gear bolt to be installed as the plans show.

The purpose of it being specified inserted from the bottom is because it makes it much easier to remove if needed, and because a properly installed bolt (full diameter of the shank, through the entire diam. of the socket) often interferes with the firewall. Because of very tight clearance, installed form the top also usually requires turning the bolt to torque the nut (a less than ideal situation on a bolt that we want a very tight fit on).
If there is not bolt interference (or a slight dent is added to remedy the interference), and you are willing to possibly have to accept turning the bolt to get the nut torqued, then installing from the top is fine.
 
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