7-99 Sealing the Nose Landing Gear

This entry is part 39 of 39 in the series 07 - Landing Gear

One of the biggest comfort issues with the Velocity is heat (or lack thereof). There are numerous methods of increasing the amount of heat entering the cabin.  I won’t go into that here.  Beyond that, the reason for lack of a warm cabin is that the retractable gear Velocity’s are drafty.

In a Velocity with retractable gear, there’s a big opening in the front for the nose gear.  While there are doors which cover this opening when the gear is retracted, it’s not airtight. And when the gear is extended, the volume of air entering through that opening is impressive.

The area under the doghouse at the leading edge of the canard is open to the nose, and all of the air entering the opening for the nose gear. This is the primary path for outside air into the cabin.

Second, that nose gear opening extends aft of the canard bulkhead. Which means air is infiltrating into the keel.  Directly above this opening is where the elevator push-pull tube exits the keel into the cabin.  Some people have fashioned boots to seal the area around the push-pull tube to block this path of outside air entering the cabin. But even then, there are numerous paths from the keel to the cabin.

The final path for outside air getting into the cabin is through the openings for the rudder pedal push rods which go through the canard bulkhead to the bellcrank.

When I extend the landing gear, I am greeted with (literally) a blast of air.  In the summer, it’s welcome.  In the winter, not so much.

Blocking the primary air path has been solved for quite a while by creating an upper bulkhead between the leading edge of the canard and the top of the nose. What I will be addressing is stopping the air through the second and third paths.

For the rudder pedal pushrods, the factory has been using a box which covers the area on the forward side of the canard bulkhead.  I couldn’t use this approach as my oil cooler exit duct if closer to the canard bulkhead than the plans call for.  Fortunately, fellow builder and problem solver Andy Millin came up with a solution.  Grommets (which I would call small bellows type seals). One for each pushrod. These are available from McMaster-Carr for about $15 each.  The part number is 9280K62.  Andy says this can be done with the canard in.  My canard was out for service which made the job much easier. Once I had removed the pushrods and bellcrank, I had to enlarge the holes to accommodate the grommets.This created a bit of a challenge because a hole saw would be the perfect tool.  But the rudder pedals were in the way from the cabin side and the oil cooler exit duct was in the way from the nose side.So here’s what I did:  I took the hole saw bit and put a ratcheting wrench on the hex shaft.  Then a large area washer went over that to give me a larger bearing surface. Wedge the whole thing in position and start turning the wrench.  In just a few minutes, I had two perfectly sized holes.

Hole saw rig:

IMG_20180328_075112 Cutting the holes:


The next task was creating a flat surface for the grommets. Now I could have just globbed on the RTV and stuck them in place. But the holes where close to the edges and I didn’t want any chance of air leaking through.  So I took a piece of ¼” aluminum stock that I had, waxed it up, applied some Resin Research epoxy with cabo around the holes and clamped the aluminum in place. The next day, I removed the aluminum, cleaned up the holes and then I was ready to install the grommets.

Ready to install the grommets:

I could have used screws to install the grommets, but as there is very little tension on the grommets, I used RTV.  Once the RTV cured, I cut the tips of the grommets off and reinstalled the rudder pushrods.


Grommets installed


View from the cabin side:


Rudder pushrods installed


Blocking the air coming through the keel has always been a challenge.  Some have made a boot similar to those found on manual transmission shifters. Over the years, I’ve considered a couple approaches.  The one that I was most hopeful of was similar to what is found on many automatic transmission console shifters. Basically a slotted housing with a flexible, wide area washers.  But because of the size of the opening, I would need multiple wide area washers with slotted openings and that would require guides on the housing.  If I was still in the building stage, I would have explored that further.  But I wanted to get back in the air.  So I went with Plan A.

I had thought about this approach while still building but I abandoned it to get finished. Basically, it’s a pair of supports with baffle material being the final seal against the pivot shaft.  The disadvantage to this method is that there is a gap while the gear is in transit. But when the gear is up or down, it should provide a very good seal.  I took measurements and built up the concept in CAD to get the dimensions and validate the concept.

Here’s what it looks like:


There are two rigid components.  The upper (canard) and lower (floor) brackets.  One thing I did NOT want was one of these coming loose and preventing the gear from extending.  So on the canard bracket, the two center mounting holes go through the canard bulkhead with MS27039 screws and locknuts. Since there’s no way to do through-hole screws on the floor bracket, I used 5 T10 screws.

bulkhead floor

The material for the brackets is 1/8” aluminum.  This is a bit of a challenge to bend, but I didn’t want any possibility of it deforming.  The flexible material is standard 1/8” baffle material which is cut trial-and-error to get a tight fit against the gear leg in the retracted and extended position.

NOTE: I do not think it’s possible to install these with the canard installed. Also, the brackets are a little oversized.  They will require some trimming to fit.  This is intentional since you want a very tight fit to the sides of the keel.

In the first version, I attached the baffle material to the bracket using pop rivets. But I noticed buckling.  So on the second version, I used 1/16” aluminum stock as a backing surface.

I planned on using RTV to fill any gaps between the brackets and the keel but decided to try it out before doing that.

Gear up.  I could have made the floor baffle a little tighter, but then I would run into binding when the gear was down.


Gear down.  Very tight fit all around.  And that’s when it is really needed.


View from inside the keel with the gear up.  A little bit of gap here, but I’m more concerned with when the gear is down.


On the first flight after installing, when I lowered the landing gear, I was a little alarmed at first because I thought the gear wasn’t extending. There was no familiar rush of air when the gear was extending. Before, I could always feel a strong breeze around my lower legs.  Now, the only indication that the gear is down is the drag of the gear and the wind noise from the gear hanging out in the air.

I’m going to have to wait about six months for cold weather before I can claim total success. But at this point it feels promising.



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