Washers on Tail Rotor Pitch Links
Although I have never experienced such an event
on the tail rotor pitch links, it is possible for the rod end bearing
retainer to fail allowing the rod end outer casting to slip over
the bolt head that secures it to the tail rotor mechanism. A simple
safety modification is to install a washer under the head of each
of the four bolts with a large enough diameter to prevent the rod
end casting from being able to totally come off the bolt. If the
bearing retainer should fail then the pilot would feel a vibration
from the tail rotor area but the rod end should remain functional
for enough time to allow an emergency descent and landing
above photo is typical and you can see that the washers are
not installed under the bolt heads.
tail rotor pitch pins above have the washers installed.
- It has been suggested that the builder install
a large enough washer that the washer OD will not fit through
the outer casing of the rod end should the rod end bearing keeper
- The bolt's safety wire will pass around washer
The Slider rails on the Rotorway
helicopter will wear with use and can become quite sloppy. I have
seen them worn to the point of failure on at least one Rotorway
helicopter. The factory plans direct the builder to drill a hole
through the slider and the slider rail once the belts were stretched
to firmly secure them from movement. I have seen this done and when
I checked the tail rotor belt tension it was way on the loose side.
The builder did not think that he needed to make any more adjustments
after the initial stretch—Wrong! If this method is followed it is
possible to end up with a series of holes drilled on the slider
from multiple adjustments over the life of the belts. It is not
a bad method but it takes additional time to remove the screws and
nuts in order to adujust the tail rotor belt tension.
One of my students had what he felt was a better
solution that is pictured below. This aviation cable turnbuckle
was purchased from Aircraft Spruce and Specialty and has forks on
each end. The forks slip onto the rail and are bolted on beyond
the 1” furthest adjustment mark. To adjust the belt tension he clips
the safety wire that passes through the hole in the turnbuckle and
is wrapped around the all thread rod. He then loosens the turnbuckle,
tightens the belts, tightens the turnbuckle to clamp the rails against
the slider firmly, installs new safety wire to prevent the turnbuckle
In the photo above you can also see
that the builder installed a tubular bushing on the rear portion
of the all thread rod behind the jam nut. This gets the jam nut
out in front of the rear aluminum angle where it can be easily reached
with your 1/2" wrench each time you adjust the tail rotor belt
tension. You will be glad you installed this simple modification.
Below is a photo of the Aircraft Spruce and Specialty catalog
where he ordered the turnbuckle. It is an AN
150-8S turnbuckle assembly.
You can click on this link that I have provided to go directly to
their order page for this turnbuckle. Remember that each builder
is responsible for any alterations that he makes. I am simply sharing
what others have done on their own helicopters.
Once again I am posting an account from
my personal experience to help you guys become aware of another
issue that has surfaced from poor workmanship on the part of a builder.
If you are aware of these issues, you will know what to look and
listen for on your own ships before disaster strikes.
Just yesterday I was providing phase one
hover training with a student who purchased a partially assembled
kit. He finished it himself and the work that HE DID was excellent.
I had gone over this ship very carefully and found a number of small
issues that we corrected before beginning hover training.
After we landed following the 4th hover
hour I noticed a slight ticking coming from the tail rotor area.
I could not pinpoint the source of the ticking but it was in a rythmic
pattern of sound with each revolution. When I asked my student if
he has assembled the tail rotor shaft assembly he said that those
components were already put together by the former owner.
I told my student that it would be prudent
to take the tail rotor assmebly apart to inspect the mechanism before
further flight. We pulled it into my hangar and pulled it apart.
We found that the former owner had drilled
misaligned holes in the pulley and shaft and then had attempted
to straighten out the misaligment by through-drilling which resulted
in oblong holes. As the ship was now hovering the forces were allowing
the pulley to wobble on the 3/16 bolt making the clicking noises.
The hole in the pulley was a3/16 by5/16" oval by the time we
found it and the bolt was severely worn and nicked by the relative
movement of the TR drive shaft against the bolt in sheering action.
The pulley to shaft bolt was certainly
about to fail and the shaft would most likely have cracked in a
short time if the bolt has not gone first- either happening during
flight could have been disasterous.
Keep an ear tuned to all parts of your
ship. I find that it is helpful to listen to the rotorating components
on run-down as the blades coast to a stop as sometimes an unusual
sound will signal big trouble brewing.
This is one more case of poor craftsmanship
buy a former owner that is hidden and passed on to an subsequent
unsuspecting builder who is an A&P with IA credentials and who
teaches at an A&P training technical school. If it can escape
my inspection and his inspections, it may not have passed your own
Listen and learn.
We are ordering a new shaft and pulley