My legacy 12 is approaching 900 hours and it is recommended to do a gearbox inspection at 1000 hours. How many have done the inspections at that interval, and what have your findings and/or actions been? To date I have not experienced any of the symptoms some have described online, and it has been smooth and quiet. Thanks for your input.
Van's Air Force
The definitive Van's Aircraft support community! Buying, building or flying an RV? Join our exclusive family of mentors and enthusiasts!
Gearbox Inspection Findings/Actions
- Thread starter n74846
- Start date
We have done three (on two different engines). The first was expensive because the "dog bone gear" had to be replaced due to wear. The 2nd and 3rd were just the normal consumable parts needed to do the inspection and re-shim.
Lockwood gave the feedback that they would rather see the gearbox sooner (and more often) than Rotax suggests, to help prevent expensive internal wear (like we had the first time).
It depends on workload, but Lockwood has been able to turn the gearbox quickly 2 (ready next-day, or two days after receipt).
Pulling/reinstalling it was not that hard. On one of the three overhauls we have needed to replace the seal behind the gearbox.
And don't break a gear like this:
Make sure you have the tool/plan to pitch your prop correctly on reinstall.
Lockwood gave the feedback that they would rather see the gearbox sooner (and more often) than Rotax suggests, to help prevent expensive internal wear (like we had the first time).
It depends on workload, but Lockwood has been able to turn the gearbox quickly 2 (ready next-day, or two days after receipt).
Pulling/reinstalling it was not that hard. On one of the three overhauls we have needed to replace the seal behind the gearbox.
And don't break a gear like this:
Make sure you have the tool/plan to pitch your prop correctly on reinstall.
Lockwood has done all of my engine work and to my knowledge it was not done at 500 hours. They definitely recommended it for the next service. I will confirm my service records.
I did mine at 1000 hrs. Lockwood had to replace the dog gear and the crank connecting gear. The gears and shipping were the big expense.They said if you let it go to long you might have to replace the prop. shaft which would be real expensive.
Jetguy
Well Known Member
Sounds like you should do the inspection around 1000 hours then.
Good luck!
Piper J3
Well Known Member
A data point for reference…. I have an early S/N (1200058) RV-12 with 997TT and no gearbox issues since new. I will continue to operate the gearbox "on condition”. Slip clutch is within torque spec and I have almost no metal slivers on the magnetic plug. When I burb the engine I often turn the prop backwards to “feel” how smooth the transition is between ramps on the dog drive plate. I have been using Mobil1 4T 10W-40 full synthetic oil since new with oil changes at 75 hrs. Fuel is Costco 93E10. I start and run engine at a high idle ~2800 rpm for warmup to reduce engine roughness when cold.
All that said…. at 970TT I changed from the Sensenich 2-blade to a 3-blade Carbon E-Prop. Entire prop assembly (hub, blades, spinner, pitot tube, and all hardware) weighs 4.4 lbs. This low moment of inertia is very good for the gearbox. The prop is dynamically balanced at the factory and is incredibly smooth.
I think some of the Rotax 912 gearbox failures are attributable to improper heat treatment of internal parts at the factory and/or incorrect surface finish – rough gear hob / grind finish on internal parts. My friend had gearbox failure at 400TT on his RV-12. The prop shaft / clutch basket spline was heavily worn – I think improper heat treatment. Carbs were synched well since new and engine operated very conservatively.
All that said…. at 970TT I changed from the Sensenich 2-blade to a 3-blade Carbon E-Prop. Entire prop assembly (hub, blades, spinner, pitot tube, and all hardware) weighs 4.4 lbs. This low moment of inertia is very good for the gearbox. The prop is dynamically balanced at the factory and is incredibly smooth.
I think some of the Rotax 912 gearbox failures are attributable to improper heat treatment of internal parts at the factory and/or incorrect surface finish – rough gear hob / grind finish on internal parts. My friend had gearbox failure at 400TT on his RV-12. The prop shaft / clutch basket spline was heavily worn – I think improper heat treatment. Carbs were synched well since new and engine operated very conservatively.
My 12 is also an early model and I changed the oil every 50hrs.and only used clear 92 fuel. Always kept the carbs synched and the prop dynamic balanced. Slipper clutch always checked good and no metal on the magnetic plug. I went back and forth on if I should have the 1000 hr. Inspection. As it turned out I’m glade I did so that it didn’t damage the prop shaft and other gears. Your new e-prop looks like it should be great! I land at a few grass strips and will be following your post as to how it holds up to abrasion.
My legacy 12 gearbox was serviced at 600 hrs. and required no service other than consumables. When serviced I was told by doing this service I would be more likely to have dependable performance of the 912. I believe much of the the services Rotax lists at various hourly intervals do make operations more dependable. However some do seem excessive and based on some of the harshest operating environments. IMHO
I have 1350 hrs on my 12 . gearbox since new still smooth and clutch specs are good. Never had any metal on magnetic plug at oil changes. . Burn all mogas .
I been thinking about doing the inspection.
Brad Stiefvater
124bj First customer built Rv 12 to be airworthied and fly. Maiden Flight Sept 2009
i
I been thinking about doing the inspection.
Brad Stiefvater
124bj First customer built Rv 12 to be airworthied and fly. Maiden Flight Sept 2009
i
I have almost 600 hours on my 2010 RV12...I've been noticing increased chatter/rattle starting the past two years, it is gone when past 3500 rpm. most notable during warm up. After landing it's a lot quieter. Carbs always kept in sync. and prop balanced dynamically, Chip det. always clean, oil filter is too...going to send to Lockwood this winter for IRAN
