I’ve got a O-360 A1A with a fixed pitch Sensenich metal prop (76EM8S5), I’ve only got about 6 hours on it now since overhaul and it’s been running great but I feel like it could be running smoother. This engine/prop is on a converted cessna 175, the STC paperwork I have doesn’t mention prop indexing so I used the manual for the piper Cherokee 180 which uses the same engine (o-360 anyways) and prop combination. It has you run the #1 piston to TDC then install the prop at the 2:00-8:00 position.

I just did a dynamic balance, which brought the vibes from .35 down to .04 per the ACES box I used but honestly I don’t think I can tell any difference when flying it, maybe a tiny bit.

Now I’ve been scouring the forums and see that many people with 4 cyl lycomings and fixed pitch props index the prop horizontally when the #1cyl is at TDC. This puts the blades parallel with the crank throws, and puts the prop in a better position for hand propping. Supposedly there is a Lycoming SB talking about indexing the prop as such on certain aircraft but I haven’t read it.

Anyone have any input on how they index props or any tips? I’m half tempted to try one of Sensenich’s new(ish) ground adjustable 72” composite props although they are not certified and are advertised for faster airplanes 150+mph (not sure why that would really matter so much?).

Lycoming O-360 A-1As (and every other O-360 Ive met) propellers should be indexed such that the propeller stops at the 10 and 4 o'clock position (viewed from the front facing aft) when the engine shuts down. So, if you are standing behind the airplane on it's right side, one blade should be one stroke above horizontal. The prop should NOT be horizontal, or vertical, as Aviat tries to tell everyone.

One of the reasons for the indexing I noted is that it enables one to hand prop the airplane in the event of a dead battery.

And by the way, O-360s (except angle valve O-360s) are kinda shakers in any case. Composite propellers really smooth them out, but barring that, you are most likely going to have some vibration regardless with that engine/prop combo.

MTV

Thanks for the reply. I have not noted where the prop stops but have heard it mentioned in other places as well. I never really payed any attention to it and never really thought it would stop in the same place every time but I guess with a 4 cylinder you are probably right. I plan on calling Lycoming and Sensenich tomorrow to see if I can get a solid position from either of them.

Ummm, go to airport. Look at prop position. If you didn’t move it after shitdown, that’s where it’s indexed.

Yes, 99 % of the time, the engine will shut down at the same place.

MTV

I don’t know if I moved it since last shutdown so I’ll just start paying attention to where it stops, but I’m pretty sure it doesn’t stop in the same position it was installed in. I’m gonna try and get a passenger or two with O-360’s in their planes to ride along, maybe what I’m feeling is totally normal and it just makes more vibes than I’m used to like you said. I did remove a GO-300 engine to put this O-360 on.

Newbizor wrote:I don’t know if I moved it since last shutdown so I’ll just start paying attention to where it stops, but I’m pretty sure it doesn’t stop in the same position it was installed in. I’m gonna try and get a passenger or two with O-360’s in their planes to ride along, maybe what I’m feeling is totally normal and it just makes more vibes than I’m used to like you said. I did remove a GO-300 engine to put this O-360 on.

I guarantee you that most any O-360 is going to vibrate more than just about any O-300. Four cylinder vs six, to start, and those O-360 pistons are big ones by comparison. Indexing does also make a difference, as well. Most of my experience with these engines has been with constant speed props.

MTV

Here's another indexing wrinkle. My IA took my CS prop off to have it resealed, and when he put it back on, he admitted that he had it indexed wrong. It looked fine to me, but he said that although it was at the 10 and 4 position, it was the wrong way, based on an index mark. So he said to fly it, see if I noticed any additional vibration, and if so, he'd pull it and reinstall it correctly. I couldn't tell any difference at all, so I told him to leave it be. And that's where it still is, several years later.

So apparently there's some obscure requirement to have a particular blade at 10 and the other at 4, but it makes no noticeable difference to me.

Cary

Cary wrote:Here's another indexing wrinkle. My IA took my CS prop off to have it resealed, and when he put it back on, he admitted that he had it indexed wrong. It looked fine to me, but he said that although it was at the 10 and 4 position, it was the wrong way, based on an index mark. So he said to fly it, see if I noticed any additional vibration, and if so, he'd pull it and reinstall it correctly. I couldn't tell any difference at all, so I told him to leave it be. And that's where it still is, several years later.

So apparently there's some obscure requirement to have a particular blade at 10 and the other at 4, but it makes no noticeable difference to me.

Cary

Constant speed props are indexed on these engines with an indexing pin. Unless you move that pin, the prop only goes on in one indexing. Why did your mechanic move the indexing pin? There’s no reason to move that pin unless you intend to change the index. Unless your prop doesn’t have said pin, which would be illegal.....

MTV

I just wanted to follow up to note a few observations.

The prop was indexed per the manual at 1-7 (as looking from the front). But every time I shut down it stops at 10-4.

I flew with another guy who has an archer with a similar engine and same prop, he claims the plane runs super smooth, so I guess I’m just manufacturing my own vibration in my head.

I am beginning to feel a lot more comfortable. I’ve got about 9 hours on the engine now and even though I can physically and audiably notice vibes at certain RPM’s, most RPM,s are very smooth. The first flight I made after the balance was something like 18 gusting 25+, so that may have had something to do with vibration perception.

mtv wrote:

Cary wrote:Here's another indexing wrinkle. My IA took my CS prop off to have it resealed, and when he put it back on, he admitted that he had it indexed wrong. It looked fine to me, but he said that although it was at the 10 and 4 position, it was the wrong way, based on an index mark. So he said to fly it, see if I noticed any additional vibration, and if so, he'd pull it and reinstall it correctly. I couldn't tell any difference at all, so I told him to leave it be. And that's where it still is, several years later.

So apparently there's some obscure requirement to have a particular blade at 10 and the other at 4, but it makes no noticeable difference to me.

Cary

Constant speed props are indexed on these engines with an indexing pin. Unless you move that pin, the prop only goes on in one indexing. Why did your mechanic move the indexing pin? There’s no reason to move that pin unless you intend to change the index. Unless your prop doesn’t have said pin, which would be illegal.....

MTV

No idea. My IA tends to be overly cautious about complying with "da rools", so I'd be surprised if he did anything illegal. And since I'm no mechanic and wasn't present when he reinstalled the prop, I don't know whether there was a pin or not. FWIW, it's a McCauley on the O-360--I know some Avcon conversions use a Hartzell--whether that makes any difference, I don't know.

Cary

Cary wrote:

mtv wrote:

Cary wrote:Here's another indexing wrinkle. My IA took my CS prop off to have it resealed, and when he put it back on, he admitted that he had it indexed wrong. It looked fine to me, but he said that although it was at the 10 and 4 position, it was the wrong way, based on an index mark. So he said to fly it, see if I noticed any additional vibration, and if so, he'd pull it and reinstall it correctly. I couldn't tell any difference at all, so I told him to leave it be. And that's where it still is, several years later.

So apparently there's some obscure requirement to have a particular blade at 10 and the other at 4, but it makes no noticeable difference to me.

Cary

Constant speed props are indexed on these engines with an indexing pin. Unless you move that pin, the prop only goes on in one indexing. Why did your mechanic move the indexing pin? There’s no reason to move that pin unless you intend to change the index. Unless your prop doesn’t have said pin, which would be illegal.....

MTV

No idea. My IA tends to be overly cautious about complying with "da rools", so I'd be surprised if he did anything illegal. And since I'm no mechanic and wasn't present when he reinstalled the prop, I don't know whether there was a pin or not. FWIW, it's a McCauley on the O-360--I know some Avcon conversions use a Hartzell--whether that makes any difference, I don't know.

Cary

Cary,

Please re-read my post: CONSTANT SPEED PROPELLERS installed on O-360 Lycomings must have an indexing pin.

Since you apparently have no propeller control in your plane, what I pointed out doesn’t apply to your installation.

Aviat apparently decided at some point that the O-360 in the Husky (CS prop) has less vibration when indexes at 12/6 and started delivering new planes that way. Absolute bitch to hand prop that way, and first winter I flew one the POS sealed battery they installed (since corrected) gave up out in the middle of nowhere.

I’d been bitching to maint. To re index that prop, but they drug their feet, citing pain in butt to move said pin.

I propped the thing, barely (on skis to make it worse), flew to town and told Maint that the plane was unairworthy with prop indexed at 12/6 and that battery. Told the boss I was taking time off till it got done.

Flew it the next day, and could tell no difference in vibration at all.

MTV

mtv wrote: Please re-read my post: CONSTANT SPEED PROPELLERS installed on O-360 Lycomings must have an indexing pin.
Since you apparently have no propeller control in your plane, what I pointed out doesn’t apply to your installation....

I'm pretty sure Cary has a c/s prop.
Mike, you sure about the "indexing pin"?
My 470 Continental has such a pin, but I dunno if I've ever seen a Lyc with one.
But as I recall, the Lyc 320 in my C150TD had one slightly oversized and/or stepped bushing in the flange which served as an indexing guide.

hotrod180 wrote:

mtv wrote: Please re-read my post: CONSTANT SPEED PROPELLERS installed on O-360 Lycomings must have an indexing pin.
Since you apparently have no propeller control in your plane, what I pointed out doesn’t apply to your installation....

I'm pretty sure Cary has a c/s prop.
Mike, you sure about the "indexing pin"?
My 470 Continental has such a pin, but I dunno if I've ever seen a Lyc with one.
But as I recall, the Lyc 320 in my C150TD had one slightly oversized and/or stepped bushing in the flange which served as an indexing guide.

Yup, it's a CS McCauley. I'm no kind of aircraft mechanic, so I know nothing about an indexing pin. I only know what my IA told me when he reinstalled the prop after new seals had been put in it, because it had been leaking for a couple of years but had gotten worse.

Cary

hotrod180 wrote:

mtv wrote: Please re-read my post: CONSTANT SPEED PROPELLERS installed on O-360 Lycomings must have an indexing pin.
Since you apparently have no propeller control in your plane, what I pointed out doesn’t apply to your installation....

I'm pretty sure Cary has a c/s prop.
Mike, you sure about the "indexing pin"?
My 470 Continental has such a pin, but I dunno if I've ever seen a Lyc with one.
But as I recall, the Lyc 320 in my C150TD had one slightly oversized and/or stepped bushing in the flange which served as an indexing guide.

Hmmm, I have zero experience with McCauley CS props. I didn't even know they made such a thing for the O 360.

And, yes, while it's often referred to as an indexing pin, it's actually a force fit collar. In any case, you can't just remove the prop and rotate it one bolt. And, that collar can be a bitch to get off. They recommend that you have a new one on hand before you attempt removal, since they're often destroyed in the process.

MTV

Cary wrote:

hotrod180 wrote:

mtv wrote: Please re-read my post: CONSTANT SPEED PROPELLERS installed on O-360 Lycomings must have an indexing pin.
Since you apparently have no propeller control in your plane, what I pointed out doesn’t apply to your installation....

I'm pretty sure Cary has a c/s prop.
Mike, you sure about the "indexing pin"?
My 470 Continental has such a pin, but I dunno if I've ever seen a Lyc with one.
But as I recall, the Lyc 320 in my C150TD had one slightly oversized and/or stepped bushing in the flange which served as an indexing guide.

Yup, it's a CS McCauley. I'm no kind of aircraft mechanic, so I know nothing about an indexing pin. I only know what my IA told me when he reinstalled the prop after new seals had been put in it, because it had been leaking for a couple of years but had gotten worse.

Cary

Cary, my bad, I didn't even know Mac built a prop for those engines. The "Pin" is actually a collar on one stud, which has the same result as a pin, as Hotrod noted. Your mechanic must have removed and re installed that collar. That's a Lycoming thing, I believe, since it's used on Hartzell and MT props.

MTV