Can one very cold start destroy my 912ULS gearbox?

[3kdscf]

Last week I did a 27F start without pre-heating (lesson learned), took three tries over 30 minutes and it was very rough but it finally started. On way home, engine ran smooth at all rpms and started quickly and easily when warm. At home, just to see if I screwed anything up I measured the gearbox friction torque and it was startlingly low, 230 in-lbs. Just 80 hours prior at my 200hr engine service it measured 465 in-lbs. I was incredulous and remeasured the friction torque both cold and at normal operating temp but its really 230 in-lbs now. Everything *seems* normal. Engine cold starts fine at 60F and runs normally.

Is this real? Can one low temp rough start destroy the gearbox?

What are the risks of running a gearbox with the minimum acceptable gearbox friction torque?

I have the old gearbox without the weep hole that requires inspection every 600hrs, is it worth the cost to upgrade to the new model that only requires inspection every 1000hrs?

My engine pre-heat kit has already been ordered

Engine Serial Number: 6785083
Engine Type: ROTAX 912 ULS
Engine Version: 912 ULS2-01
Model Number: 309120110
Production Date: 08-Oct-2015

[Av8r3400]

As someone who runs their 912 in cold weather often, I highly doubt that this one cold-start damaged your gearbox.

My followup questions: Is there any possibility that the previous measurement was erroneous somehow? What is the total time on the gearbox?

If the friction torque measurement that you are currently measuring is still acceptable, keep running the engine and monitor it to see if it changes.

[3kdscf]

As someone who runs their 912 in cold weather often, I highly doubt that this one cold-start damaged your gearbox.

My followup questions: Is there any possibility that the previous measurement was erroneous somehow? What is the total time on the gearbox?

If the friction torque measurement that you are currently measuring is still acceptable, keep running the engine and monitor it to see if it changes.

My first thought was that I had an erroneous measurement too. I re-checked my fish scale that I use for the measurement with a dumbbell plate and it was still accurate.

The gearbox has 800hours on it and I sent it to Motive Aero at 600hrs for the required inspection and it was fine. Even if my measurement at 720hrs was in error, theirs during the 600 hour service would have been accurate. I suppose its possible that it was just normal wear that kicked in after the 600hr inspection.

[Dave S]

I have to agree with Larry. Minnesota isn't any warmer than Wisconsin; and, I have no reason to believe that temperature could affect the durability of the slipper clutch. The torque/friction on my first engine never went out of the limits, although readings were never identical. New engine is too new to know yet.

How warm the engine is when measuring may have an effect on the reading - oil gets thinner and metals expand when hot - and they do the opposite when cold. Measuring hot vs cold engine is worth thinking about - I try to adhere to the same conditions when doing this measurement.

[Slyfox]

I have the 912uls. Over the last probably 4 years I've been through hell with my setup. I had several issues with starting my 912uls. Had carb problems, right carb ended up having a seat problem in the left carb, replaced the carb and now that's good. Had module problems, went to soft start modules both sides (2008 motor). Than I had problems with the sprag clutch, replaced that. I still had start up problems so I went with an earth x battery (the smallest one) I also replaced all cables to I think 6 guage or better. I last year switched to the e prop with inflight adjust. Now that was a real nice move. Now I can start without heat at 30 degrees and it starts with one blade. How's that. I love this plane more than ever. Nice and smooth at all rpm's and very predictable. I look forward to flying it every time. Did the cold start hurt your gear box. I can't say so, maybe your prop did something through time. What prop do you have? Before the e prop I had the medium IVO, nice prop, but hated the motor for inflight, piece of work.