Alternator STC SA 10682SC belt replacement

[CaptainRamius]

I took off our Hartzell prop for long overdue overhaul and....... I might as well replace the alternator belt while off.  The replacement belt I bought from Aircraft Spruce appears to be the same (I used same part number as old belt) but it is slightly smaller (won't fit - locking arm won't take up slack without modification). The -325 at end of part number signifies (per Lycoming tech) that it is 32 1/2" long. IPC shows -325 as generator belt.  Lycoming IPC shows the belt for the alternator version to be 37A19773-376 OR 37 6/8" (last number is in 1/8ths or 37 3/4"  This is 5 inches longer than the one on there! Alternator locking arm cannot take up that much slack (due to dog house baffling and clearance).  I can trim the dog house a little but not much. I then called Hartzell Engines that owns the STC for the Alt conversion.  Belt calls for a Gates 9335XL. Gates makes belts for MANY applications (except aviation). They have a legal disclaimer that you cannot use their belts on planes/helicopters. I can buy the same belt at O'Reilly's for about $22.  Spruce has no cross reference. 

QUESTION:  As Hartzell owns the STC and it calls for a Gates drive belt (33 7/8" long), can I LEGALLY and SAFELY use a Gates belt bought at an auto parts store? 

Lycoming O-360-A1D

[EricJ]

15 minutes ago, CaptainRamius said:

I took off our Hartzell prop for long overdue overhaul and....... I might as well replace the alternator belt while off.  The replacement belt I bought from Aircraft Spruce appears to be the same (I used same part number as old belt) but it is slightly smaller (won't fit - locking arm won't take up slack without modification). The -325 at end of part number signifies (per Lycoming tech) that it is 32 1/2" long. IPC shows -325 as generator belt.  Lycoming IPC shows the belt for the alternator version to be 37A19773-376 OR 37 6/8" (last number is in 1/8ths or 37 3/4"  This is 5 inches longer than the one on there! Alternator locking arm cannot take up that much slack (due to dog house baffling and clearance).  I can trim the dog house a little but not much. I then called Hartzell Engines that owns the STC for the Alt conversion.  Belt calls for a Gates 9335XL. Gates makes belts for MANY applications (except aviation). They have a legal disclaimer that you cannot use their belts on planes/helicopters. I can buy the same belt at O'Reilly's for about $22.  Spruce has no cross reference. 

QUESTION:  As Hartzell owns the STC and it calls for a Gates drive belt (33 7/8" long), can I LEGALLY and SAFELY use a Gates belt bought at an auto parts store? 

Lycoming O-360-A1D

Yes, if it is the same part number and essentially the same part.   

Maybe, if it is the same part but a different part number.   In that case you need to be able to show that it is essentially the same part.   

Since you have to take the prop off to change it, it's worth making sure you get a belt that will hold up.

[N201MKTurbo]

Yes, I was told by an FAA inspector that you can use the autoparts belt, if you know it is the same belt that Lycoming is selling.

https://www.faa.gov/documentlibrary/media/advisory_circular/ac_23-27.pdf

https://www.eaa.org/eaa/news-and-publications/eaa-news-and-aviation-news/news/-/media/3d1238d3989f4e14856fbcec35b2ef0d.ashx

[PT20J]

The STC provides the approved data for the Gates belt. Keep a copy of the STC in the unlikely event it is ever questioned. 

[CaptainRamius]

Skip,

I have a copy of the STC. What page do you see Gates belt?  I don't see it. 

[PT20J]

41 minutes ago, CaptainRamius said:

Skip,

I have a copy of the STC. What page do you see Gates belt?  I don't see it. 

I was responding to your original post where you seemed to say that the STC calls for the Gates belt. What belt does the STC call out?

[CaptainRamius]

Just found it on page 18 under the note 1. FOR STANDARD 7.5 DIAMETER RING GEAR SUPPORT PULLEY USE PIPER V-BELT PlN 452-541 (GATES 9335XL). NOT SUPPLIED

Reading the AC from M201MKTURBO and talking with my friend who is an FAA inspector.  Think I'm good. Will chat with my IA tomorrow. Thanks Skip.

[CaptainRamius]

Thought I responded. I found it. Page 13 or 18 under Note 1:  For standard 7.5" ring gear............................. Use Piper V-Belt...............(Gates 9335XL), NOT SUPPLIED.  It's not supplied so you have buy it somewhere else.  O'Reilly's $21 or Aircraft Spruce (doesn't have it).   

[MB65E]

Slight caution on the belt. It’s trial and error.
The gates belt recommendation from the STC did not fit my airplane. These were some notes from my log entry when I did the Plane Power alternator. 

“Replace generator with plane power alt kit SAL-1270. Belt gAtes 9335xl. Not correct size. Installed 38 3/8" gates XL belt.”
 

Also during the conversion I found a cracked case. 

-Matt

[CaptainRamius]

Thanks Matt. I am very cautious. I'm all about SAFETY and LEGALLITY. Going to hangar this afternoon. My read from all comments is that as this belt is not supplied with the STC that you have to source what fits. Aircraft Spruce does have one that is 38 3/8" long however the current is 32 1/5.  Tension rod will not take up an added 6 inches of slack. Will report my findings later. Consulting also with my IA.   

The Gates 38 3/8" belt. Do you have the part number and where did you buy it?

Steve

[GeeBee]

If you go to the Gates web site, you can get the part number by filtering by size. Gates by the way is the finest v belt known to man. Do not substitute. Most good auto suppliers can get you any Gates belt not currently in their stock.

[MB65E]

Is the paperwork correct? Great, well it’s still broke! 
I’d be less concerned about the paperwork and get a belt that works.

Belt was purchased from O’Reillys. Back when they would let you go behind the counter! 
-Matt

[CaptainRamius]

Sooo......  I bought a 9335XL Gates belt per the STC. However, (comma) there isn't enough slop in the tension arm to get it tight. So tomorrow I'm buying at 9330 and 9325. (Last 3 numbers are length 335=33.5", 330=33.0" etc.  One of them will work.  The dog house baffling doesn't leave much to tighten even when trimming some of the aluminum. I WILL have a belt that works. Ironically Aircraft Spruce doesn't carry it. 

[A64Pilot]

Gates does manufacture very good belts, but like most everything else there are different grades.

I believe their green stripe line is best, if that part number can be had as a green stripe belt I think I’d go that route.

My data may be old, maybe there is something heavier duty than the green stripe now.

Normally I’d say a belt is a standard part, but if the STC calls out a specific part by manufacturer and part number you are likely only allowed to use what they specify