• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • There is no better time to show your support for SuperCub.Org than during our annual calendar campaign! All the details are HERE

Prop Indexing

stewartb

MEMBER
A typical 2-blade prop has the bolt holes drilled so two holes align the the prop blades. TDC, index at 1:00-7:00 (from the front) and it'll stop at the typical 10:00-4:00 position, right? My Whirl Wind hub holes are 30* off from the standard position. I can index it to stop at 9:00-3:00 or 11:00-5:00. Which is best and why? And why is my constant speed indexed differently?

IMG_0962.JPG

IMG_0194.JPG
 

Attachments

  • IMG_0962.JPG
    IMG_0962.JPG
    135.9 KB · Views: 224
  • IMG_0194.JPG
    IMG_0194.JPG
    124.1 KB · Views: 242
Does Whirlwind give any installation instructions?lots of times the position of the prop impacts vibration characteristics.


Sent from my iPad using Tapatalk
 
None that I've seen mention prop installation position.

As I look at Husky pics I see props horizontal and vertical. Maybe I'll look into their instructions.
 
Stewart,

Early Huskys came with props indexed at 10/4, which made them easy to hand prop if need be. I took delivery of the first production A-1B, which came with the prop (Hartzell 76 in. CS) indexed at 12/6. This A/C also had a crappy gel battery, which didn’t like cold. A few episodes of having to prop that engine in places I REALLY didn’t want to sleep prompted me to investigate Aviat’s reasoning for this indexing.

In short, it was found that the O-360 A-1P engine had “slightly” better vibration characteristics with the prop (again the 76 inch Hartzell) indexed at 12/6. I discussed this with both Hartzell and Lycoming tech reps, both of whom said that re-indexing the prop to 10/4 would not produce significant or harmful vibration issues, particularly if we dynamic balanced the assembly.

As to the legality, the Husky TCDS shows both indexing, so Aviat said as far as they were concerned there was no problem re-indexing. Since you’re Ex, that’s not an issue.

Thats what we did. But re-indexing these props requires moving the indexing pins. Hartzell recommended having spare indexing pins on hands when doing so, since it’s somewhat likely that the pins be damaged in the process. In my experience with a couple of these cases, maintenance folks were able to move the pins without damage.

The take home I got from Hartzell and Lycoming was they were amazed that this indexing was a problem. Apparently, they believe that every airplane out there only lands at airports with maintenance facilities. So, they saw an opportunity to “slightly” improve vibration characteristics and went there.

They also noted that in general, very few prop/engine assemblies are dynamic balanced in the real world. They felt that doing so would be equally or more effective in reducing vibration. In any case, none of the vibration this move was intended to treat was considered “destructive”.

WE RE-indexed most of these props after that. Since these are Part 23 aircraft, Aviat verified that either indexing was “legal” since early airplanes were indexed at 10/4.

I still recall one episode with the plane on straight skis in really deep snow, and -30 temps and a dead battery. One of the few times I wished I was six foot six inches tall, with arms like an orang.....

Oh, and we also replaced those POS gel batteries with Odyssey batteries, which also reduced the liklihood of a repeat.

MTV
 
Last edited:
Hand propping without the 10/4 index is nearly impossible for me, even though I've been hand propping since 13 years old as the line boy at the old Tew-Mac Airport in Massachusetts in he 1950's. The blades on an MT or Hartzell CF make it even more difficult. It was very difficult to get good info on this when I operated Huskies, but it sure felt good after, to know that you could actually fire up if (when) it didn't want to crank. As another note, ever try to get a jump start with a small plane? Mismatched plugs, Piper pins, 3 prong....At best it's usually jumper cables in an awkward and potentially dangerous situation. Safer to hand prop. I can't imagine propping a seaplane with 12/6 set up, unless you had Dr. Seuss arms..
 
No indexing pins on my plane. All positions are available. 10:00-4:00 isn't an option. The closest I can get is 11:00-5:00 or 9:00-3:00.

I have a Balance Master installed. Whirl Wind is adamant about prop balancing and they liked the Balance Master idea when I spoke to them about it.

Anyone know why a CS is indexed differently than a fixed pitch?

Jumping an airplane? I carry a Jump Pack. Not specifically for the plane but I'd use it if needed.
 
Part of the answer may be as MTV said in todays world engineers may not consider hand propping in the design, thinking having the prop level to the ground gives better clearance. I see a lot of planes built/rebuilt design factors usually only involve how pretty it looks and how fast it can get done, no thought on how they will be maintained six months down the road. Stoddards has a hardwire jumper cable for the Earth X jump pack. I am changing motor mount and doing some firewall work at this time so I am going to run the cable into the pilot side glove box. If I need to use the jump pack we can plug it in from pilots seat. Cub is pretty simple to prop, I have not tried the 180, My buddy can prop his inject 185 but he had a lot of milk when he grew up.
DENNY
 
No indexing pins on my plane. All positions are available. 10:00-4:00 isn't an option. The closest I can get is 11:00-5:00 or 9:00-3:00.

I have a Balance Master installed. Whirl Wind is adamant about prop balancing and they liked the Balance Master idea when I spoke to them about it.

Anyone know why a CS is indexed differently than a fixed pitch?

Jumping an airplane? I carry a Jump Pack. Not specifically for the plane but I'd use it if needed.

Stewart,

So, the indexing is limited by the propeller, not the engine or has Lycoming developed a new flange?

And, what is a "Balance Master"? Is it a harmonic damper assembly, like Hartzell uses on some installations?

MTV
 
My flange has 4 bushings that stick out and the prop has reliefs at all 6 studs, so the prop can go on in any position.

The Balance Master is a mercury-filled dynamic balancer that fits over the flywheel.

A friend with the same prop called to remind me that my center of flange is 6' off the ground so 9:00-3:00 is the best position for hand propping. Coincidentally that's where I had moved it to on the old engine. I just wondered if there was a reason not to.
 
Last edited:
My flange has 4 bushings that stick out and the prop has reliefs at all 6 studs, so the prop can go on in any position.
That is interesting. My Whirlwind 200G will only go on one way, the wrong location for hand propping. The reliefs are only on four studs. I was under the impression that the hubs on the ground adjustable and constant speed were the same. I considered moving the crankshaft prop bushings but decided that due to age (the pilot's) it was safer to not be tempted to hand prop, particularly on floats.
 
I have heard (cough cough) that a few mechanics have pressed the bushings out of the crank�� to get the prop to index for hand propping.
 
When I did my Whirlwind prop I had to shorten some of the bushings anyway, so I just put them back in where I needed too to make it come out right.
 
I have heard (cough cough) that a few mechanics have pressed the bushings out of the crank�� to get the prop to index for hand propping.

Not a problem at all.....depending on the specs for engine/prop combination. This is what we did on Huskys. Lycoming and Hartzell approved with the only caveat that they recommended having spare bushing on hand in case one was damaged. We never damaged one in three or four of these.

MTV
 
Would.have bought a whirlwind a few years ago if not for the bushing deal. Folks at whirlwind didn't want to help me find the bushings. Can you say Catto!
 
Real question here.

It's been my experience that the bushings on a typical O-320 or O-360 have one 'locator' bushing to make sure the ring gear is indexed properly. The outer portion of all of the bushings are the same size. The way I learned to install a prop for hand propping was to hang it as per the military manual and then back it up one bolt hole. This leaves one blade handy for hand propping and if there was any vibration, it's usually cured by flipping the prop 180º. Is there a special bushing arrangement for these props like the Cato, Whirlewind, etc?

Web
 
Real question here.

It's been my experience that the bushings on a typical O-320 or O-360 have one 'locator' bushing to make sure the ring gear is indexed properly. The outer portion of all of the bushings are the same size. The way I learned to install a prop for hand propping was to hang it as per the military manual and then back it up one bolt hole. This leaves one blade handy for hand propping and if there was any vibration, it's usually cured by flipping the prop 180º. Is there a special bushing arrangement for these props like the Cato, Whirlewind, etc?

Web
My Whirlwind 200G on an IO-360B is at about 7 or 8 o'clock.
 
Seems like a lot of people index their props to make hand-propping easier.
I think at least part of the factory indexing position is due to harmonics issues.
Might be good to keep that in mind.
 
My Whirlwind 200G on an IO-360B is at about 7 or 8 o'clock.

Seems like a lot of people index their props to make hand-propping easier.
I think at least part of the factory indexing position is due to harmonics issues.
Might be good to keep that in mind.
In my case, my engine came from a high winged twin engine airplane. 7 or 8 o'clock would have been good for hand propping. And I do not know whether that was the determination for the position. But yes harmonics could be part if the decision, yet that would also involve the particular prop/engine combination.
 
Back
Top