FlyingGuide

Anti-feathering pins is the correct term for the pins.

NE_Pilot

The thought is that as long as the RPM does not drop below 950 it will feather, but once it drops to or below 950 it will be impossible to feather.

They engage at 950 RPM and are called Feather Locks, according to the Seminole POH (might be something you might want to look into investing in). The locks will move into place automatically when the RPM reaches 950, the only way to prevent the locks from moving into place is to keep RPM above 950 on each engine. If you have the Prop Lever in the feather detent the Prop will feather no matter what the RPM is, unless it is 950 or below when you move the prop lever to feather. The locks PREVENT the Propellers from feathering.

When you do the feather check you are making sure that the propellers will feather, the reason they do not feather on you is because you go to the feather position for a short period of time before moving them back to full forward. If you were to leave the prop lever in the feather position it would feather, what is preventing it from feathering is that you are only going to feather for a moment, then right back to full forward, not allowing the oil pressure to drop enough to completely feather the propeller.

The oil pressure helps in allowing you to change the pitch of the propeller. A lack of oil pressure will move the props toward a feather position.

The feather locks prevent the propellers from feathering when shutting down and starting up the engine, because oil pressure may not be enough to prevent the propeller from feathering.

burns629

During the run-up check when you set the RPMs to 1500 and do your feather check, you're actually testing the lift rod - the mechanism in the governor that overrides the entire system and allows you to set the prop in the feather position. The reason you do this at 1500rpm and not at 2000 with the rest of the run-up sequence is because the tremendous loads that the blades in the feather position impose on a running engine.

undflyboy06

Actually, the prop won't feather. My MEI instructor one day set the RPM to 1500 and slowly brough the Prop control to feather. The RPM dropped to below 950 and the props were still spinning in a lower pitch higher RPM, they were not feathered.

burns629

2 things could have happened there.. obviously even if it did feather in that situation the prop would still be spinning: its connected to a running engine.

Or if it didn't get anywhere near a feather position it would mean something was wrong with the feathering system. It could possibly be there wasn't enough of a N2 charge, or that the oil wasn't able to completely drain out of the system. Doubt you were missing the spring inside the hub, or that the counterweights fell off the prop (would imagine that would create a noticeable off-balance situation).

burns629

So just thinking about it still, I suppose if he brought the throttle back slow enough he could have gotten the engine RPM to drop below the anti-feather lock engage speed before he passed the feather detent...

but according to piper when you do the feather test/lift rod test, you should quickly move the prop control back... to me that would mean you get the selector in the feather position before the engine has a chance to slow down like it would if you very slowly brought the blue knob back.

Laxrox43

Mista,

I have a "Smokin' hole" POH out in front of me...so here we go!

These prop locks that we have talked about are called "Feathering Locks." These locks are operated by centrifugal force, and make it impossible to feather the propeller once the RPM has dropped below 950 RPM.

Now the second topic...not 100% sure...so I will leave that up to someone else:P

poor pilot

950 is the magic number its set that way so when you are on the ground or ready to shut down it won't feather. Oil pressure send the prop to low pitch high rpm the exact opposite of a pipper arrow if you loose oil pressure the spring gives you the ability to feather when you don't have oil pressure. I always called them lock out pins. when you are exercising the props you are checking three things 1) decrease in oil pressure 2) decrease in RPM and 3) a increase in manifold press.

mistarose

If you loose oil pressure fast, the pins wont have a chance to engage and the prop should feather. If it is a slow leak, the feathering locks will have time to engage and will unless you manually feather the prop before the RPMs decrease to 950.

Everyone agree? Thanks for the input!

ImperialxRat

I may be reading this wrong, but I think you got confused...you stated that he was moving the throttle lever...

The throttle is set at 1500. the only lever after this being moved is the feathering one. you bring it down nice and slow to the detent, move it into the feather position, then back out.

As stated previously, we're mainly just making sure that the prop will go into feathered mode, so that in the case of an emergency we are able to feather the prop.


As im sure we all have done, I recall when we shut down an engine in flight, the RPM was below 950, meaning the anti-feather locks would be engaged. however, ya run through your checklist, and the last item is to feather the engine...which indeed it did feather.

So does the feather knob over-ride the anti-feather locks?...or was i just mistaken that the windmilling prop was below 950rpm? Its been awhile since ive feathered an engine in flight.