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RV-14A SB-00027 published: Nose gear modification and part change

greghughespdx

Well Known Member
Advertiser
Van's has published RV-14A Service Bulletin SB-00027, which describes a change to be made to the exiting nose gear leg assembly as well as the addition of either a new washer or replacement cap part. Please refer to the service bulletin document for the details.

Data from an incident in the field shows that under certain circumstances the RV-14A nose gear leg, if it was to fail due to extreme overload, could fail in such a way that the mechanism would strike the fitting/hose on the fuel pump attached to the engine, potentially breaking the fitting and/or hose, increasing the risk of a fire.

Van's has designed a modification to the existing nose gear leg weldment (removal of a small amount of material for clearance). The steps to complete that modification are described in the service bulletin document.

In addition, Van’s has released a new replacement washer, which modifies the loads spread across the nose gear cap in an extreme overload scenario. As an alternative to the washer, one can choose to replace the existing cap with a new version of the part. Either of these changes (new washer or new cap) will result in the same outcome: In the event of a complete gear leg failure, the nose gear attach point will break lower, at the threads rather than at the top cap. This lower breaking point results in a motion path in which the fuel pump fitting/hose would not be struck by the top of the rotating gear leg.

The new washers are available from Van's at no charge (including free shipping), or the updated version of the cap can be purchased if desired. Again, either part results in the same design outcome. It is only necessary to use either a) the new washer in combination with the existing cap, or b) a new cap without the washer.

These parts are available for use in compliance with a portion of RV-14A SB-00027. Please choose one or the other, as both are not needed. The same result is obtained by using either part.

The parts are available to order on the Van's web store, in the Airframe Maintenance section under the SB-00027 name.
 
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Hello Greg,
Another great job by the Team at Van's Engineering.

Can u provide the dimensions of the new thick washer, WASHER-00023 , so that we may be able to order it here locally in Australia?
Or is it a custom part we need to order?

Cheers,
 
A while back I bought this carbide burr for some aluminum shaping:
https://www.aircraftspruce.com/catalog/pnpages/12-00591.php

Is this gear leg "soft steel"? Or should I get something else?

I would recommend you get a different cutter.

It is an overly general statement that doesn't universally apply at all times, but in general terms you can think of a selection of this type of cutter to be the same as selecting saw blades.

Cutting of soft materials like wood (and aluminum) works best using blades with a course (wide spacing, fewer teeth per inch) tooth pitch, and harder materials cut best with a finer pitch (more teeth per inch) blade.

What you have would probably work but it is a higher risk for the tool operator because it will have more tendency to grab and will be more difficult to get a nice finish which would mean spending a lot more time working by hand with a file.
 
Thought as much. Another chapter to my tool and workmanship education!

Could someone please post a link to the suitable attachment for either my die grinder or dremel?

I'm really good with all things aluminum. Steel not so much...

Of course I suppose I could buy a new gear leg but I'll leave that for after I screw up the one I have!!!

thanks!
 
I'm also wanting all the info on the "incident in the field" if it is sharable.

I'll share what's available.

The two photos you see in the SB document are from that incident in the field. The aircraft was involved in an accident in a farm field. It was stalled high during the approach to landing and "dropped in" a significant distance to the ground, with enough height force from the vertical drop that the main landing gear flexed and the wheel pants struck and damaged/tore the underside of both wings. The nose gear was also severely over-stressed on impact, and responded to the specific over-stress event as designed, meaning it the nose gear link arm separated at the top and the leg pivoted/rotated aft, under the forward fuselage. We discovered that the broken U-01416 Nose Gear Link assembly, which attaches to the nose gear leg (you can see this in the Figure 2 diagram in the service bulletin), struck the fuel pump fitting while the nose gear leg assembly rotated on its pivot point and under the fuselage. The hardware located at the top of the nose gear link assembly pulled through the U-04120 cap. There was no actual fire as a result of this accident, but this incident and our subsequent review, analysis, and testing is what led to this change.

We made the two changes (outlined in the service bulletin) to modify the critical failure mode of the nose gear in the event of a severe overstress failure. The purpose of these changes was to ensure any moving components will not strike the fuel pump, fitting or hose during an overload/failure mode incident.

First, the addition of the "slot" in the U-01406 Nose Gear Leg specified in the service bulletin allows the link arm to swing further back during an overload failure, which in turn moves the top of the U-01416 Nose Gear Link Assembly further away from the fuel pump fitting/hose as the leg rotates under the aircraft during an overload/failure incident.

Second, the use of either the larger WASHER-00023 or the new U-01420-1 cap (which is heat-treated to a greater relative strength than the original cap) increases the relative strength of that location in the Nose Gear Link Assembly and transfers the critical load from the top of the cap to the bottom of the threaded portion of the link arm, where testing proved it will fail/break during an overstress event, rather than at the top of the cap. This, in turn, results in a shorter post-failure link assembly arm as the leg rotates (as designed) under the aircraft.

These changes result in the Nose Gear Link Assembly arm distance from the pump/fitting/hose being increased, preventing the arm from striking the fuel system components.

And, to clarify: This issue applies only to the RV-14A, and does not apply to any other RV models.
 
Thanks for the detailed answers. Very interesting.

I was going to take apart the assembly soon and put the second washer on top of the shock absorbers as there is a little gap for it now. Should I expect the gap to recur and add yet another washer later or is the one all that is needed?
 
Cut'in out the notch?

I have not done anymore than order a new cap, reviewed the SB instructions and studied the top of the gear leg that needs to be cut.

Givens -
- fairly thick, hard steel.
- not much space behind the notch fitting area and the gear leg tubing, a reciprocating saw probably has too much of a blade throw to use there (?).
- A dremel cut-off wheel cuts straight paths fine but does not do radii cuts unless they are big radius.
- Van's recommended cut-out shape looks like close to impossible - at least very difficult. I am not familiar with any tool that would work to do that cut-out profile.

An approach -
- How about starting off by drilling a pilot hole in the fitting and then following up with a metal hole saw. The thing here is that a hole saw radius does not exactly match the curve shape of the Van's recommended cut-out. (?) - Van's feedback needed here for a recommend cutout circular shape that would be ok. - If the length of the straight side cuts are required, then the depth to the rear of a circle shape will be deeper. Or is the rearward depth of the notch the limit as shown on the notch diagram?
- After the hole is cut - then cut the straight lines with the dremel cut-off disc.

ANOTHER QUESTION - Has Van's accomplished this modification to the gear leg fitting? And what steps did they follow, with what types of cutting tools?

Van's feedback appreciated.
 
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Looking at the accessibility of the weldment, wondering if it may be easier to just remove the 2 hinge bolts and take the whole gear leg assembly off to do the metal cutting.....

Untitled4.jpg
 
I think it will be worth the effort to remove the gear leg and work on it on the bench. I am thinking of drilling a series of small holes to remove the bulk of material, then shape it with a Carbide Burr. Of course I will try the Carbide Burr first to see if that alone can do the job.

I have ordered the part and possibly next weekend will tackle this as my annual is due this month.
 
With the proper cutter in a die grinder on the bench it should not take more than a few minutes
 
Yep, looks to be a lot easier just removing the assembly and do the cutting on the bench, my plan :)
 
I might pull it off with the wheel and everything still on. Cut a notch, paint a little, reinstall.....
 
Please report how you cut the notch

When anybody does successfully finish cutting the notch - report your process and the tools that you found did the job, and any recommendations based on your experience.
 
Made the cut

Took about three hours (including a run to the hardware store) to make the cut with the landing gear installed on the plane. I pulled down the tail with a ratchet strap and weights in order to unload the front gear. Ended up lifting the tire about three inches off the ground in order to get better access to the bracket. I stuck an appropriately padded saw horse under the forward fuselage just in case the ratchet strap gave way and I used a bungee cord to hold the link assembly out of the way.

I made the cut with a Dremel equipped with a quick change metal cut-off disk. Due to the goofy access angle caused by the exhaust (Vetterman dual pipes) I ended up having to make a series of progressively wider cuts as I went deeper. If the exhaust wasn’t in the way, you could easily remove the bulk of the material with just two fore-and-aft cuts and an athwartship plunge cut (with a relatively small diameter cutting disc.)

In order to clean up the cut and expand it to final size, I used the Dremel with a newly acquired flex shaft attachment and a grinding stone. I ended up detaching one side of the exhaust hanger immediately above the bracket for better access. Cleaned it up and hit it with three coats of paint. Reassembly was straight-forward.

Not a particularly difficult mod with the right tools. A right angle die would have made it a bit easier but still doable with the Dremel. Not only did I get a new tool as a result of the SB, now that have the Dremel flex shaft attachment, I’m fully equipped to do some light dentistry work on the side.
 
Service bulletin question

A question for engineering from those of us who are in the process or have built the 14A using EFI. Since there is no mechanical fuel pump and associated fittings directly forward of the nose gear weldment/link assembly, there is nothing fuel related to contact. As such, the likelihood of any loss of containment of fuel directly related to the failure described in SB 00027, is very low, if present at all. Agreed, the failure mode would still exist. The consequence of failure would not. (wearing my RCM hat here)

As an Alternate Method of Compliance, can those in the above scenario, replace the washer (or cap) as a good practice, document the actions in the log and consider the SB addressed?

Any and all feedback encouraged and appreciated.
 
A question for engineering from those of us who are in the process or have built the 14A using EFI. Since there is no mechanical fuel pump and associated fittings directly forward of the nose gear weldment/link assembly, there is nothing fuel related to contact. As such, the likelihood of any loss of containment of fuel directly related to the failure described in SB 00027, is very low, if present at all. Agreed, the failure mode would still exist. The consequence of failure would not. (wearing my RCM hat here)

As an Alternate Method of Compliance, can those in the above scenario, replace the washer (or cap) as a good practice, document the actions in the log and consider the SB addressed?

Any and all feedback encouraged and appreciated.

Our service information can only accurately determine needs for aircraft built and assembled per our plans and designs. When a builder makes a decision to vary, or to install something that is not part of our standard design, the builder takes on responsibility for determining applicability related to the changes that were made on his or her individual aircraft.
 
athwartship, say what?

When I first read through TangoUniform's post I went past it assuming it was the result of fast finger typo clutter but could not catch onto the word intended.

So I Googled it.
def: being across the ship from side to side athwartship and longitudinal framing.

Learn something new almost every day! I going to look for an opportunity to fit that word into a casual conversation and watch for a quizzical facial expression.
 
I finished this SB yesterday and it took about an hour or less. I removed the gear since it gave me a much better access. Made the bulk of removal using a dremel cut off wheel then cleaned it to the shame using a Carbide burr and finally polished it using sand paper. A matching paint is available on-line for about $11 which I used to match paint it.

All-in-all, fairly easy and straight forward.
 
I'm going to do it next oil change. Pulling it off seems smart; the sparks should be more manageable too. Good opportunity to look it all over and put a little grease on moving parts too.

I also have the touch up paint. I recommend the pen; pretty slick. But the jar of paint is cheap too if you have a nice brush (mine is borrowed from my daughters collection).
 
Hi,

Did mine yesterday (UK) removed the leg and marked out the cut, used a step drill and hacksaw rough outline. Then filed to accurate size and shape. Must be very difficult to do in position. John
 
I was able to do mine with the gear on (i.e. just the forward bolt removed). There was enough room to use a pneumatic die grinder to shape the notch by going back-and-forth slowly, followed by a Dremel with carbide burr, followed by files, sandpaper, primer and paint. Not as bad as I thought it would be. To manage the sparks, I put a good-sized layer of Gorilla tape in the path of the sparks, which worked well.

_Alex
 
We lucked out in that we are just shy of engine hanging time. Went fairly quickly, and just received the new washer yesterday. Size of the washer for those interested is 25.4 mm OD, 10 mm ID, and 1.8 mm thick. A bit of a loose fit on the 3/8 stud. Wanted to attach pics but don't know how to "manually resize file" to fit!:(
 
Matching paint

I finished this SB yesterday and it took about an hour or less. I removed the gear since it gave me a much better access. Made the bulk of removal using a dremel cut off wheel then cleaned it to the shame using a Carbide burr and finally polished it using sand paper. A matching paint is available on-line for about $11 which I used to match paint it.

All-in-all, fairly easy and straight forward.

Do you have a link as to where you found the matching paint?
 
Finished SB-00027

Took about 3 hours.
- Pulled the tail down and set saw house under the fuselage for backup support.
- Removed the gear leg from the plane.
- Tools: 1" dia metal saw drill, Dremel cutoff disc and grinding stone shaft, Rustoleum spray paint.
- Pilot drilled 1/16", then 1/8" for saw drill @ center-line and 3/8" from front edge of fitting.
- Drilled hole with 1" dia saw drill, back edge of 1" hole at 13/16" from front edge of fitting.
- Dremel cutoff the two straight sides.
- Ground and polished cuts with grinding stone shaft.
- Painted with spray paint.
- Reassembled with new U-01420-1 Link Assembly Cap.

SB00027 finish pic.jpg

Note the radius profile of the aft end cut of the gear leg fitting is not the precise curve as the Van's description. The aft 1/2" radius circular cut is all within the described Van's profile but does not include the left and right side 'shoulder' radii cuts.
The U-01416 Nose Gear Link tube dia is 1" so that the notch will allow it to go into the notch as is presumably intended to do in the case of a collapse.

The diagram below shows the modification compared to the Van's profile as interpreted from their diagram of the opening.
 

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Yes, I bought it from e-bay but other places have it.
Search for

NEW-Duplicolor-Scratch-Fix-2in1-Touch-Up-Paint-NG-CC-362

https://www.ebay.com/itm/NEW-Duplic...027208&hash=item3b4ce50da8:g:cxgAAOSwQ4Rdmt0y

That paint is no longer stocked that I could find, other than e-bay, and I was afraid the e-bay stock might be old and not work. So, I ordered the current stock Duplicolor pen in the same 362 paint code, bright white Chrysler, from Amazon. It matched perfectly and came with a clear coat on the opposite end of the pen. About $16. 🤗. In reality, you use so little and noone is likely to see it, so white rustoleum would probably be fine.
 
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