Pin Knock

scottyboy75

scottyboy75

Well-Known Member
So I was teaching a lesson on mast bumping the other day when I questioned pin knocking with the chief. I thought that it was the same as mast bumping and was told no mast bumping only occurs in semi rigid underslung rotors. It is now clear as mud and any help will be grateful.
Shane
 
Mast Bumping is a condition where the yoke contacts the mast, a flapping action, which is not possible on an articulated system or a rigid system...

Semi Rigid system - if one blade goes up then the other goes down...so if it is underslung one blade might travel so far up that the opposite blade (downward side of yoke) contacts the mast... if it were not underslung the the yoke would not be able to contact the mast because it is above the mast...

Articulated system - Each blade can flap independently so if one goes up the other does not go down...which eliminates possibility for mast bumping...

Rigid System - has no flapping action so cannot contact the mast either.

Spike Knock - Is a complete oscillation of the rotor system, mast, and transmission.

Does that help any?
 
On the 206 there is an actual spike attached to the mast of the rotor system. Below the spike is a metal plate. When you get the rotor system oscillating enough (usually back and forth) from say, a hard landing, the spike contacts the plate and makes a loud noise which tells the pilot he screwed up, and that a maintenance inspection is required.

It's been 6 years since I flew a 206 - how'd I do skywestseth? ;)
 
That helps. Now just not sure how to tell my chief he don't know what he was talking about. Can the mast seperate form the rotor when it strikes?
 
Ian J said:
On the 206 there is an actual spike attached to the mast of the rotor system. Below the spike is a metal plate. When you get the rotor system oscillating enough (usually back and forth) from say, a hard landing, the spike contacts the plate and makes a loud noise which tells the pilot he screwed up, and that a maintenance inspection is required.

It's been 6 years since I flew a 206 - how'd I do skywestseth? ;)
Click to expand...

LOL, well I was actually waiting for you to say I was right on...but since we agree< I'd say we got it right, after I typed that I was like, "wow, I think I know something!"

Holy run-on sentence batman!

PS- Aircraft Selection on the 17th, 7 days to go, I'm gunning for 47's
 
scottyboy75 said:
That helps. Now just not sure how to tell my chief he don't know what he was talking about. Can the mast seperate form the rotor when it strikes?
Click to expand...


YES!!, my "CFI" (or IP) was a huey driver, and he said that they could not have "mast bumping" in the Huey, it was called Mast Bump, because as soon as it bumped it was gone!!
 
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