I’d like to share my experience with the MTV-12-B MT prop on my Lancair 360. The prop has 696 hours. I bought my LNC2  almost 5 years ago from the original builder here in Arizona. Shortly after the purchase, I noticed some grease seepage around the seals at the base of the blades. The builder said MT had said this was normal and not unusual. Unfortunately, it got worse to the point it was getting on the canopy. The prop went to the prop shop here in Tucson (he’s certified by MT) and he sent it to Florida and I was down for 6 weeks. This was quite an expensive ordeal. The seepage has occurred each year I’ve owned the plane but the shop here has fixed it under “warranty” with MT’s latest “fix” (obviously they are using a trial and error method). This year there was seepage again but not too severe, so I didn’t remove the prop during the conditional inspection (first time in 5 years). The test flight after the inspection went without a flaw. Two days later I went to breakfast and after returning was cleaning the plane and noticed more grease than previously and that one of the seals had split which indicated relative motion between the blade and the seal. I also noticed a small crack in the paint and what looked like stress marks above the crack. Being Sunday, I waited till the next morning to call the prop shop and he came out to look at the prop. He said I shouldn’t even start the engine let alone fly the plane. He surmised by looking at the blade that one or more of the lag screws had broken or had come out. I removed the prop and took it to his shop. Upon disassembly, he found the head of one of the lag screws on the blade with the split seal had sheared off and was bouncing around in the hub. Upon further inspection, a second lag screw in that blade was found to have sheared off at its midpoint and all the remaining lag screws in all three blades were found to have loosened by at least ¼ of a turn. I was told had I flown to Colorado, instead of breakfast, as I was planning to do in two days, there was a good possibility the blade would have come off the hub in flight, which is a rather sobering thought. I am awaiting the decision from MT as to what they will do to rectify the situation.
In the mean time, I have ordered a Hartzell prop from Lancair and refuse to put the MT prop back on my plane no matter what MT does or says.

Len Spina

N15EG

Tucson