Robinson TR pitch links

[Little Red 22]

How do you know when a TR pitch link is too tight? I encountered the most bar tight pitch link on a 44 today during preflight. Even the guys with a tough grip had difficulty moving it at all. The opposite pitch link was just about the most loose and free moving pitch link I have encountered.

 

I know the pitch links wear out unequally, and students wear them out pretty fast during training. How does one determine the limit of acceptable tolerance during the preflight?

[Guest pokey]

How do you know when a TR pitch link is too tight? I encountered the most bar tight pitch link on a 44 today during preflight. Even the guys with a tough grip had difficulty moving it at all. The opposite pitch link was just about the most loose and free moving pitch link I have encountered.

 

I know the pitch links wear out unequally, and students wear them out pretty fast during training. How does one determine the limit of acceptable tolerance during the preflight?

 

 

I know nothing about robbies, but a fair amount about pitch links. The links on the 300 are usually very tight, alot of times you can only "twist" it using both hands---this is OK on a 300. When they start to 'loosen up', then you need to measure the "play" in the link in both directions and compare it to the limits in the MM. The 206's are normally looser than the 300 and we used to put RTV silicone to limit the twisting, so it would not wear a groove in the crosshead. A final word of caution, do not lube the links with anything (unless the MM allows it) some have special bearing materials inside them that can be destroyed with lubricants.

[Flight1]

As a student I learned that you should be able to twist the pitch links on the preflight. However, as a CFI working at a school that has purchased three new aircraft though my time here, ALL the pitch links on the aircraft have been extremely tight. I cannot move them at all.

 

So if they come in from the factory like this, I guess that is fine. (I have only flown robbies)

[iChris]

How do you know when a TR pitch link is too tight? I encountered the most bar tight pitch link on a 44 today during preflight. Even the guys with a tough grip had difficulty moving it at all. The opposite pitch link was just about the most loose and free moving pitch link I have encountered.

 

I know the pitch links wear out unequally, and students wear them out pretty fast during training. How does one determine the limit of acceptable tolerance during the preflight?

 

There are many types of rod ends; however, the pre-flight inspection requirements are all about the same, free without play or looseness. Excessive play or loose fitting rod ends signals the need for more inspection and measurement (Per the Maintenance Manual) of the actual play. Tight internal fitting of the ball to the race is normal for some types of rod ends. You need to know which type you have.

 

For example: the Aurora's proprietary Precision Rod Ends with their PTFE liner, General Aviation, has a tight internal fit of the ball. Some model rod end are known as a “zero backlash” or “preloaded fit”. The bearing liner is permanently bonded to the race inside diameter, so the ball is very tight.

 

Just because it feels tight by hand (hard to move) doesn't mean it’s not free. Remember, its design to work under actual flight loads, which are much higher than can be applied by hand. Also, play or looseness causes additional vibrations in rotational members such as rotor systems.

 

R44II RFM pg. 4-4 13 May 2009:

 

7. Tail Rotor

 

Pitch links ............... No looseness

 

R44II RFM pg. 4-4 13 June 2005:

7. Tail Rotor

Rod ends ............... Free without looseness

 

In the S-64 tail rotor system below, you’re deal with four (4) pitch links; moreover, eight (8) rod ends were excessive play can have a cumulative effect on tail rotor vibrations that can lead to additional stress cracks at the tail pylon.

 

 

In the H-34 (S-58) tail rotor system below, you’re deal with eight (8) pitch links; moreover, sixteen (16) rod ends were excessive play can have a cumulative effect on tail rotor vibrations and stress cracks at the tail pylon too.

 

 

Edited July 4, 2013 by iChris

[Counterrotate]

If the tail rotor pitch links are tight on a 22 or 44 it just means they are new and have not broken in yet. It's when they start to get excessively loose that it is a problem. Tight is good. Loose is ok. Sloppy is bad. If you notice any lateral or axial play, have the mechanic measure it. There is a tolerance. If it's out of tolerance, the rod end needs to be replaced. A tight rod end is not going to hurt anything.