The tail wheel cable housing is a 12 inch length of special conduit that clamps to the lower tube on the rear of the fuselage and to the tail wheel trunnion on both sides.

Each end of this housing is held in a clamp with a micarta fairlead around it. The fairlead captures the flange on the end of the housing.

As the tail wheel trunnion moves up and down as the strut expands and compresses, this housing provides a flexible path for the tail wheel cable traveling inside the housing.

Now, the position of the clamp on the trunnion is not at the point of trunnion rotation, so the clamp moves back and forward about 1/2 inch as the strut goes from fully extended to fully compressed.

Fig.1 - 2 of the 3 clamps. The one with the cap on the bottom is on the plane and not available for the picture New and old housings.

Fig.1 – 2 of the 3 clamps. The one with the cap on the bottom is on the plane and not available for the picture New and old housings.

Fig.2 - Trunnion clamp with strut fully extended.

Fig.2 – Trunnion clamp with strut fully extended.

The picture above shows the aft position of the clamp with the strut fully extended, as it would be in flight. The housing is pretty straight with a slight belly in the up direction. Now during landing when the strut compresses, the clamp moves about 1/2 inch forward. Since the front end of the housing is fixed in its clamp, the housing must go into a pretty severe bend as shown in the next picture. The housing has been forced into an up-bend, and any movement of the tail wheel control cable follows the same path. This is a somewhat strange design, but it does keep the cable path length the same, so that the cable does not change tensions when the trunnion moves.

Fig.3 - Another angle of the trunnion clamp with the strut fully extended.

Fig.3 – Another angle of the trunnion clamp with the strut fully extended.

During this up-bend time, there is certainly a lot more friction on the tail wheel cable.

In installing the housing, the position of the clamp on the trunnion is fixed. The position of the housing support clamp on the fuselage tube becomes pretty important.

You have to put the trunnion and tail wheel assembly in place to get the positioning right.

Fig.4 - The aft position of the clamp with the strut fully extended.

Fig.4 – The aft position of the clamp with the strut fully extended.

It should be positioned so that the housing is almost straight when the trunnion is in the position of maximum strut extension.

Now when the strut compresses on landing, the housing will distort into the bend shown.But what happens if the fuselage clamp is positioned and tightened for a straight housing, when the strut is partially or fully compressed?

Now at lift off, the trunnion clamp will try to move its 1/2 inch aft, restrained only by the housing, which is now too short.

It might force the micarta blocks to slip in their clamps, and it might move the clamp along the fuselage tube. With the rubber covered housing and the swedged on ends, it also can pull the swedged fitting right off the rubber housing.

Fig.1 - The housing has been forced into an up-bend.

Fig.1 – The housing has been forced into an up-bend.

With the older style housing made of all metal, it can act as a stop and keep the tail wheel strut from extending. So it is important to position the fuselage clamp with the trunnion and tail wheel assembly in place and the strut fully extended.

There are probably some indexing screw holes for self-tapping screws that determine where that clamp should be. They may or may not be in the proper position for the housing that you are using or the design of the clamp. The old metal housing may be about 1/2 inch longer than the later rubber covered housing.

In addition, the clamps that are welded to the trunnion may have different distances to the pivot point. Therefore you need to check each side individually.

To further complicate matters, there are three designs of clamps for that position. One clamp has the cap which attaches with two screws on the bottom of the tube. Another has the cap on the side. A third has a regular tube spring clamp with the standoff welded on. All will probably do the job, but their indexing holes are in different spots on each.

It is clear that this clamp and the fairlead clamps must be fully tightened down.

Since the cable has to drag its way through the humped back housing, a good lubrication on the part of the cable that goes into the housing is a must.

Fortunately, after landing the strut extends back down some, and so the hump in the housing is not as pronounced during taxiing. Inspecting the clamps and housings at annual time is also a good idea.