Hartzell back from the shop and ...

[DakotaHawk]

I just had the prop shop inspect my prop, clean up the blades, and lube up the internals on my CS Hartzell. The prop looks great!

Today, I began fitting the spinner onto the prop, and found that when the forward spinner bulkhead is attached with the 4 bolts in the hub, the bulkhead nutplates are no longer aligned with the spinner.

I'm assuming that the hub cover was rotated while at the prop shop, but now I need to get everything lined up again. There's a large nut (maybe 9/16"?) on the front of the prop, but I'm hesitant to try to loosen it or attempt to rotate the prop hub cover if it's going to screw up something internal.

Any suggestions are welcome!

 

[asav8tor]

If you are talking about what I think you are talking about there is a allen hex on the bolt. You can put an allen in there, loosen the nut, move your plate, tighten nut, all the while keeping that bolt in the same spot. Moving it (the bolt) will change the flat pitch limit blade angle.

 

[rocketbob]

The prop dome is threaded on to the forward hub forging, and its threads are sealed. When the prop shop removes the dome they take a big wrench about 4' long, and bolt it to the four diagonal bolts. It usually takes two guys to get the dome off. In other words, you're not going to be able to adjust the position of the dome. You're going to have to order and fit a new forward bulkhead, of if the spacing allows it, remove the existing nutplates and reposition them.

 

[Wes Hays]

Same Problem!

I had the same problem when I had my prop overhauled. They weren't off much, but enough to not line up. I ended up ordering a new front bulkhead and installing it before I had the prop dynamically balanced.

If I understand correctly, you cannot rotate the cap by loosening the nut on the front. That is just keeps the fine pitch setting in place.

YMMV,

 

[DakotaHawk]

Clarification of language

I should have called the part that the forward bulkhead attaches to the "dome" instead of the hub. The dome is out of alignment about 20* from previous position.

If I understand correctly, I should NOT loosen the nut, I should NOT loosen the hex bolt, and I SHOULD purchase a new forward bulkhead and index it to the new position of the dome. Is this correct?

 

[rocketbob]

If I understand correctly, I should NOT loosen the nut, I should NOT loosen the hex bolt, and I SHOULD purchase a new forward bulkhead and index it to the new position of the dome. Is this correct?

Correct. The hex bolt and stop nut are the low pitch stop, it only needs to be adjusted if you can't get 2700 rpm on takeoff.

 

[Wes Hays]

If I understand correctly, I should NOT loosen the nut, I should NOT loosen the hex bolt, and I SHOULD purchase a new forward bulkhead and index it to the new position of the dome. Is this correct?

I would not loosen the nut or the hex bolt if your fine pitch is set correctly. That is the only thing that the hex bolt and the nut control.

If it is off 20* you probably would be able to use the old bulkhead and redrill and install new nutplates. (I did that the first time I had the prop worked on). If you don't have the room to install the new nutplates because they are so close to the old holes, (That is the way it was the second time when the prop was overhauled), then order a new bulkhead and drill new holes and nutplates to match the existing spinner. Bob is absolutely correct. You would be ill advised to try and unscrew or tighten the dome in order to get the holes aligned again.

Just my $.02. Good luck. It really isn't so bad either way.

 

[Kevin Horton]

Correct. The hex bolt and stop nut are the low pitch stop, it only needs to be adjusted if you can't get 2700 rpm on takeoff.

Actually, it would be better if you couldn't quite get 2700 rpm early in the take-off roll. If you can get 2700 rpm in the early part of the take-off roll, your low pitch stop is set finer than it needs to be. This would increase the windmilling drag during an engine failure, and increase the rpm that the engine will go to if the prop governor ever fails, or if you have a loss of oil pressure. According to Hartzell, during a full power static runup, the rpm should be somewhere between 2650 and 2700.

I believe that it is best to have the low pitch stop no finer than it needs to be. If the low pitch stop is set to give 2650 rpm in the initial part of the take-off roll, the rpm will increase as the speed increases, and you should have 2700 before the aircraft becomes airborne.

 

[osxuser]

Certified aircraft installations typically don't use nutplates on forward bulkhead but rely on a bit of pressure exerted on the forward bulkhead when the spinner is installed and screwed onto the rear. Hard to explain, but basically the last 16th inch or so of the spinner has to be forcefully pressed over the forward bulkhead, so the rear holes will line up. This interference fit prevents the majority of any chaffing. Typically install a little anti chaff tape on the forward bulkhead to tighten up the install works.

I've modified one of the RV's I've worked on to this after it's prop overhaul with positive results.