Should be prop balanced after overhaul?

[MooneyBob]

I got my plane today after long annual. One of the items on the list was overhauled prop and governor ( the reason was more than 16 years since new and leaking governor). I had my prop ( 3 blade McCualey) balanced last year and it was pretty smooth. I noticed today that I can feel more vibration than before annual. Specially at lower RPMs. 

1. Should be the prop balanced after the overhaul? 

2. My take off RPMs were 2610 compare to 2670 before the annual? Is it too low? Does it affect the take off performance?  Can governor be adjusted to higher RPMs? 

Thanks.

[carusoam]

Cody is our prop guy...

But, until you get an answer from a qualified person, I'll start the conversation...

The prop gov is an easy adjustment.  There is probably a procedure to set it while static on the ground.  Ideally, 2700 while in motion. Ask your mechanic to bump it up to where it belongs.

Being off 100rpm is approximately being short 5% hp.  Better to have it, than not.

Sounds like dynamic balancing is called for each time bolts get changed on the prop.  Let us know who you use for this.

Best regards,

-a-

[MooneyBob]

14 minutes ago, carusoam said:

Cody is our prop guy...

But, until you get an answer from a qualified person, I'll start the conversation...

The prop gov is an easy adjustment.  There is probably a procedure to set it while static on the ground.  Ideally, 2700 while in motion. Ask your mechanic to bump it up to where it belongs.

Being off 100rpm is approximately being short 5% hp.  Better to have it, than not.

Sounds like dynamic balancing is called for each time bolts get changed on the prop.  Let us know who you use for this.

Best regards,

-a-

 

My MSC sent it to East Coast Prop Services. I just checked the logbook and it says it was dynamically balanced. But I don't think they did it while attached to the plane. I think it has to balanced together with spinner and bulkhead.  Not an expert on the props.  

Cody?

Thanks. 

[Jeff_S]

If you take it to a prop shop they can at least run the analysis and tell you if an imbalance in the prop is causing your vibration. The problem with a dynamic balance on the plane is that in most cases, the only way to correct it is to drill holes in the spinner bulkhead and apply a screw with some washers to get the right amount of weight in the right spot(s). People have been doing this for years and it's an accepted practice, but some (myself included) don't like the idea of altering an otherwise perfectly good airplane part. It really is up to you how comfortable you feel about it.

Of course, if doing so is the only way to reduce vibration that may otherwise shorten the life of your engine mounts, avionics, etc., then perhaps the trade-off is worth it. But getting the analysis done will at least arm you with the info on what is possible.

[Bob_Belville]

I've had H&H Prop @ KBUY dynamically balance props several times. It is done on their ramp at cruise RPM, takes less than 1 hour. If the machine indicates that the prop needs no adjustment H&H charged $125, about half their price for balancing. My last viisit was with a brand new Scimitar Top Prop which needed no adjustment.

FWIW, PowerFlow Exhaust thinks balancing is helpful to their fancy pipes and extends their warranty if prop gets dynamically balanced. 

But I'll be interested in Cody's input!

 

[Guest]

Propellers are normally statically by the prop shop after overhaul.  Your installer would normally reinstall the prop in the same position on the crankshaft. Normally old dynamic balance weights are removed and the prop and engine are dynamically balanced again.

If you are worried about drilling weight attachment holes in your spinner bulkhead, your  Lycoming engine stater ring gear has 12 bolts which hold the spinner bulkhead, they can be used to add balance weights.

Clarence

[Shadrach]

47 minutes ago, M20Doc said:

Propellers are normally statically by the prop shop after overhaul.  Your installer would normally reinstall the prop in the same position on the crankshaft. Normally old dynamic balance weights are removed and the prop and engine are dynamically balanced again.

If you are worried about drilling weight attachment holes in your spinner bulkhead, your  Lycoming engine stater ring gear has 12 bolts which hold the spinner bulkhead, they can be used to add balance weights.

Clarence

We had an RV Builder on the field that was doing balances for $100 with his new machine. I found an A&P that said he would sign it off. Long story short, we got the thing balanced but he said he was no comfortable with us using the bolts on the spinner bulkhead. I was not comfortable drilling the bulkhead and starting over for no reason. We ended up removing the weights returning to its pre dynamic balance state.

[N601RX]

2 hours ago, Shadrach said:

We had an RV Builder on the field that was doing balances for $100 with his new machine. I found an A&P that said he would sign it off. Long story short, we got the thing balanced but he said he was no comfortable with us using the bolts on the spinner bulkhead. I was not comfortable drilling the bulkhead and starting over for no reason. We ended up removing the weights returning to its pre dynamic balance state.

I have a spinner backplate that was drilled at some point before I got it.  I think it was a bad idea, but was also concerned about the legality of it. After much looking I found some FAA guidance which said balancing was a minor change and was a logbook entry. I believe it was the form of an AC which mostly said follow the directions provided by the balance manufacturer company.  After looking at a couple of balance manuals I found one that said to drill and countersink screws into the spinner backplate.  I believe it was a Chadwick manual that said this.  The other manuals said use extra washers which seems like a much better option.

AC 20-37E

[Shadrach]

2 hours ago, N601RX said:

I have a spinner backplate that was drilled at some point before I got it.  I think it was a bad idea, but was also concerned about the legality of it. After much looking I found some FAA guidance which said balancing was a minor change and was a logbook entry. I believe it was the form of an AC which mostly said follow the directions provided by the balance manufacturer company.  After looking at a couple of balance manuals I found one that said to drill and countersink screws into the spinner backplate.  I believe it was a Chadwick manual that said this.  The other manuals said use extra washers which seems like a much better option.

AC 20-37E

We were using a Chadwick device. A&P wanted to use the guidance that came with the balancing equipment and I wanted to utilize existing hardware (which is what all of the EXP guys that did not need a signature used).

[Cody Stallings]

Dynamic Balance! Yes Sir.

To clear up any confusion, with a 400 Series McCauley like the one you have there is no drilling on the backing plate. Your propeller has a balance ring on the front of the propeller just for balancing purposes.

Dynamic balance is highly recommended for marrying all of the rotating components together. Smooth is good.

 

Now the Crazy part!!!!!!! 

Your propeller leaves the repair station static balanced, when the dynamic is performed on the plane you are taken the propeller out of Balance. Yes out of balance!!!!!

The propeller is the only thing rotating you can manipulate the balance on. With that being said, the velocimeter has no idea what it's balancing. Crank,Cam,Prop,Mags,Ect.

It only feels IPS(Inches Per Second).

By Moving/Adding/Removing weights on the prop will bring the IPS down.

Your engine bearings, engine mounts, avionics,exhaust, intake tubes an passengers will thank you.

Give me a call if you have any questions or concerns.

Shop 870-208-8882

Cell 870-208-5198

[carusoam]

It is good to have you on our team, Cody!

Thanks for sharing all the prop details.

Best regards,

-a-

[Cody Stallings]

I belive the Advisory Circular talks about balancing a propeller coupled with a 500HP must have a 337 filed.

Just like any FAA instruction, it covers a wide spectrum of topics, but is specific about nothing. Leaves a lot of room for interpretation.

The Manufatures Approved(which is also FAA Approved) data is what the balancing should be done with.

I use Chadwick-Helmuth equipment so I do everything IAW the 9511-2 manual. It's drawn out very clearly what needs to take place when balancing a propeller.

Lets he honest. If you have 5 guys standing around trying to figure out what "exactly" the AC is trying to say, you will get 5 different answers.

 

[bonal]

Lets he honest. If you have 5 guys standing around trying to figure out what "exactly" the AC is trying to say, you will get 5 different answers

 

Kind of like Mooney Space

[Cody Stallings]

Yes. Sorta like that!!!....:)

Wait, no. We are all seasoned professionals here.....lol

[MooneyBob]

5 hours ago, Cody Stallings said:

Dynamic Balance! Yes Sir.

To clear up any confusion, with a 400 Series McCauley like the one you have there is no drilling on the backing plate. Your propeller has a balance ring on the front of the propeller just for balancing purposes.

Dynamic balance is highly recommended for marrying all of the rotating components together. Smooth is good.

 

Now the Crazy part!!!!!!! 

Your propeller leaves the repair station static balanced, when the dynamic is performed on the plane you are taken the propeller out of Balance. Yes out of balance!!!!!

The propeller is the only thing rotating you can manipulate the balance on. With that being said, the velocimeter has no idea what it's balancing. Crank,Cam,Prop,Mags,Ect.

It only feels IPS(Inches Per Second).

By Moving/Adding/Removing weights on the prop will bring the IPS down.

Your engine bearings, engine mounts, avionics,exhaust, intake tubes an passengers will thank you.

Give me a call if you have any questions or concerns.

Shop 870-208-8882

Cell 870-208-5198

Thanks Cody. I will get it balanced. 

[MooneyBob]

14 hours ago, Cody Stallings said:

Yes. Sorta like that!!!....:)

Wait, no. We are all seasoned professionals here.....lol

Cody,

my other question was about the T/O RPM. My CGR30 reads now 2610 RPMs on T/O. It was 2670 before the prop and governor overhaul. Is it way to adjust it?

Who should do that? Whoever overhauled the gov or any mechanic?

thanks 

[Guest]

Just now, MooneyBob said:

Cody,

my other question was about the T/O RPM. My CGR30 reads now 2610 RPMs on T/O. It was 2670 before the prop and governor overhaul. Is it way to adjust it?

Who should do that? Whoever overhauled the gov or any mechanic?

thanks 

Bob,

Adjusting the prop governor high speed stop screw is fairly easy, a small lock nut and a piece of safety wire. Cut the wire, loosen the lock nut and back the screw out, usually about 25-30 RPM per revolution.  In some cases the limiting factor is not the governor it's the setting of the prop fine pitch blade setting.  If you have a Hartzell its field adjustable, if a McCauley there is no field adjustment, it has to be done in a prop shop.

Clarence

[Jeff_S]

I admit that my experience and my above post was influenced by the dynamic balance I had done on my J, with a Lyc engine. Cody, if you're still around, on a Continental IO-550 with the Hartzel 3-blade prop, are there similar dynamic balance points that would preclude someone from drilling the spinner backplate? If so, then I may look into this again.

[Cody Stallings]

Bob, your A&P should be able to get your RPM dialed in with the governor.

 

Jeff, your hartzell uses screw on weights near the root of the blade.

You would just have to get with the person doing the balance to see if they have the weights needed to balance a compact Hartzell.

[Jeff_S]

Just to follow up this thread, I finally had a morning to get up to the Sensenich prop shop at KGVL and get a dynamic balancing done. Out of the gate my prop wasn't bad, with a reading of only .21 inches/second. I was told that this satisfies the factory spec, and that at that rate I probably wasn't feeling any vibration (I wasn't). But we worked on it, and had to give it six runs to find the magic number (yeah for hot starts!) but we got it to .10 and decided to call it a day.

And I don't know if this is luck or just good prescience on somebody else's part, but it turns out my spinner bulkhead already had holes with nut plates on it and one lined up perfectly with where we needed to apply the correction. The technician said he had NEVER seen pre-fabbed nut plates on a small airplane before...usually those are on the turbo-props. So once we found the right spot, applying the weight was super-simple.

As predicted, I also didn't notice any difference flying it home, but now I know at least that things are in good shape with the fan up front.

[KSMooniac]

We did my MT prop a couple weeks ago, and the MT manual calls for adding balance weights on the forward bulkhead, which of course is hidden by the spinner.  We used the Dynavibe system, and it worked great!  Highly recommended.  Got my installation down to 0.02 and it feels like a sewing machine again.

[kevinw]

I had my prop balanced about 2-3 years ago and got in down to .06. It was a very windy day and apparently the calmer the winds, the better. My question is how often should it be done? I had it done a few months after the factory remanned engine was installed and now 150 hours later it seems like some of the vibration has come back. It's not bad, just doesn't seem quite as smooth as it was after the balance.

[KSMooniac]

I'd say if you can feel a change, then you ought to at least get it measured.  Parts wear as things settle in... could be your mounts, engine bearings/crankshaft, etc.