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912ul 912uls gearbox inspection

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6 years 6 days ago #5483 by cc13675
912ul 912uls gearbox inspection was created by cc13675
Please, I would like some information regarding Propeller Gearbox Inspection for 912UL/912ULS Engines. My local Aviation Authority is requesting me to obtain this information straight from the manufacturer, so I would appraciate if you can help me with the following questions:



1.- What is the correct TBO for the gerboxes installed on 912UL and 912ULS Engines?

2.- Which document/onformation should we use to determine the Gearbox inspection/overhaul applicability and procedure?

3.- Are this gearbox inspections mandatory or recomended? which criteria do we use to determine if the inspection is mandatory or not?

4.- If we are performing the gearbox and porpeller shaft inspection, IAW Heavy Maintenance Manual, do we have to remove and replace the Shatf seal and roller bearing? is this mandatory or recomended?

Thank you very much for your time and good efforts, I will really appreciate or the information that you can provide us, as I mentioned, I have to provide this information to uor local aviation authority here in Korea, for them to ensure compliance of the applicable procedures to the Rotax Owners and operator in the country, which are still not very clear to them. Thanks again, I hope to hear back from you soon with a positive reply.

Best Regards,

Jaepil Kim

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6 years 6 days ago #5484 by Roger Lee
Replied by Roger Lee on topic 912ul 912uls gearbox inspection
Hi Jaepil,

Some of your questions are hard to answer since many of us don't live in Korea and the rules and regulations may be different. The time line for the inspection also depends on your engine MFG date and serial number. The information for the time line is in the Line Maint. manual.
The inspection may be 600 hrs if you have a 1500 hr TBO engine or use 100LL more than 30% of the time in a 2000 hr.TBO engine. If you have a 2000 hr. TBO engine and use less than 30% 100LL and use mostly 91 Oct. auto fuel then the gearbox inspection is 1000 hrs. At this point I usually toss the bellville washers and just put new ones in, inspect the gearbox as per the Heavy Maint. manual and re-shim. At the TBO (1500 hrs. or 2000 hrs) time I would go ahead and put a new bearing and oil seal in too. It's cheap and easy enough.
The Heavy maint. manual section 72-00-00 address the gearbox inspection and limits on some parts.
As far as being mandatory in a country other than the US I don't know your rules and regs.
It's highly recommended and smart to do, but may not be mandatory

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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6 years 6 days ago #5485 by kotsa
Replied by kotsa on topic 912ul 912uls gearbox inspection
Hi Roger,

From your post above, I understand that you usually do not remove a propshaft, do not replace the bearing and oil seal with new ones during the 1000H (or 600H) gearbox inspection.
Then how can I check a propshaft's condition (or wear limits) described in heavy maintenance manual section 3.9.10 without removing propshaft and bearing from a gearbox?
And is this common procedure in the Rotax service centers for the gearbox inspection?
Thank you for your supports.
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6 years 6 days ago #5486 by Conrad
Replied by Conrad on topic 912ul 912uls gearbox inspection
Jaepil,
The maintenance intervals & requirements vary depending on the engine type, the gearbox configuration & the fuel used. The gearbox tear down is a heavy maintenance job & you should get training if you are going to tackle this.
There is an error in the current 912 Line Maintenance Manual & the referenced chapter for the work required is incorrect. In 2 places 12-00-00 section 14.1 should refer to section 14.2

My interpretation of the manuals is the work/measurements required are as follows:
The references (such as GB18) can be found in the Heavy Maintenance Manual.

Cleaning & visual inspection of all components during dismantling.
Backlash GB18
Friction torque
Propshaft run out GB04
Crankshaft diameter CS04
Crankshaft spline CS07
Drive gear spline GB14
Drive gear & dog gear pitting
Bush diameter GB01
Clearance GB01-CS04
Adjust preload of disc springs (note there are 2 different methods depending on gearbox type
Bearing seat diameter GB02
Bearing seat diameter GB03
Bore diameter GB05
Spigot diameter GB06
Clearance GB05-GB06
Propshaft spline GB15
Clutch hub/dog spline GB16
Free height of disc springs GB13
Thrust washer thickness GB11
Axial clearance GB07
Wear on dog hub GB08
Slipping torque
Slipper clutch dismantle & clean to remove lead contamination
Inspect fuel pump plunger & eccenter
Inspect step collars
Inspect steel bush
Replace bearing 832235
Replace ring 1/2's
Replace serrated washer
Measure crankshaft run out with & without gear installed

You will require some special tooling.
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6 years 5 days ago #5494 by Roger Lee
Replied by Roger Lee on topic 912ul 912uls gearbox inspection
Hi Conrad,

Talked to some of the distributors here in the US. For us the gearbox inspection is just that an inspection. The one you posted is for a prop strike inspection. We pull the box apart. Inspect all the parts for any problems, excessive wear and or spalling and pitting, ect.... The shaft stays in, no new oil ring or bearing. If the Bellville washers are within tolerance specs you could leave them, but I always just put new ones in. Check the clutch break away torque and then just re-shim. If it has been run on 100LL then of course the clutch comes apart for lead removal. It should be good then for another 600-1000 hrs.depending on the engine serial # and 100LL use.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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6 years 5 days ago #5495 by Conrad
Replied by Conrad on topic 912ul 912uls gearbox inspection
Hi Roger,
Looks like there are some differences in the interpretation of the manuals. The line maintenance manual cites the Heavy Maintenance manual section 72-00-00 section 3.9, but the line maintenance manual does mention that crack testing is not normally planned (for the 600/100hr gearbox inspection anyway).
There are a number of items such as measurement of the propshaft spline that will not be influenced by a propstrike, but will wear in normal service.

Take a careful read of section 72-00-00 3.9 in the Heavy Maintenance Manual & see what you think afterwards. Sections 3.9.10, 3.9.11 & 3.9.12 give the gearbox inspection items. (this is what we have been carrying out for years & teaching.)

I would be interested in YOUR interpretation after carefully reviewing the Heavy maintenance manual.

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6 years 5 days ago #5496 by Roger Lee
Replied by Roger Lee on topic 912ul 912uls gearbox inspection
Hi Conrad,

I'll be happy to take a look and re-read those sections. I have a call into Rotax for a little interpretation too.

Rob,

If you read this chime in with your thoughts.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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2 months 1 week ago #21471 by Marcpa
Replied by Marcpa on topic 912ul 912uls gearbox inspection
Hi is there an outcome on this subject, what is the right procedure?
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2 months 1 week ago - 2 months 1 week ago #21476 by Roger Lee
Replied by Roger Lee on topic 912ul 912uls gearbox inspection
The 600 or 1000 hr. is just an inspection. No crack checking or integral measuring. With some experience you can see if there is enough wear to be a concern for a more detailed check. Some boxes look in really great shape and then occasionally you see some with badly worn dog gears or splines. There is one up north of me where they just found a drive gear (small gear on end of shaft) with 2 broken teeth at about 2200 hrs..

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last edit: 2 months 1 week ago by Roger Lee.

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