MT Prop delaminated

[stogie17]

Yesterday after 2 trips around the pattern didn't notice anyting but got bad feeling so taxied back and checked over AC. My MT composite prop on constant speed 0=360 had delamed and peeled up on blade from blade root about 6" or more up on trailing edge of blade. Could look inside and see 6" of wood core. I had a few light surface cracks that were only finish and had noticed very similar small cracks in root area but at annual we determined they were just surface too which is common and sealed as Mt instructions. Must not have been. I was amazed blade stayed together and amazed had no vibration. Laminated epoxy and spruce core I guess stronger that imagined but discering to say least. Checking options. A tip delamed on Husky in USF&W a week earlier. Any one else flying Composite props had problem? Not interested in arguement for or against Mt or Hartzell at this point just interested in other similar situations from those actually flying them.

[Ryan Smith]

Yesterday after 2 trips around the pattern didn't notice anyting but got bad feeling so taxied back and checked over AC. My MT composite prop on constant speed 0=360 had delamed and peeled up on blade from blade root about 6" or more up on trailing edge of blade. Could look inside and see 6" of wood core. I had a few light surface cracks that were only finish and had noticed very similar small cracks in root area but at annual we determined they were just surface too which is common and sealed as Mt instructions. Must not have been. I was amazed blade stayed together and amazed had no vibration. Laminated epoxy and spruce core I guess stronger that imagined but discering to say least. Checking options. A tip delamed on Husky in USF&W a week earlier. Any one else flying Composite props had problem? Not interested in arguement for or against Mt or Hartzell at this point just interested in other similar situations from those actually flying them.

I find it crazy that props on 170s and Huskys are delaminating, but those on aerobatic airplanes generally don't have that problem.

No first-hand experience with MT props on 170s, but curious how old the prop is (age and time in service). Have you contacted your dealer? I've never heard of surface finish cracks in the blades either.

Hope you get to a resolution soon. Glad you didn't have a bigger problem on your hands if the blade separated from the hub!

[flyingredyeti]

Out of curiosity Stogie, can you explain what may have led to your uneasy feeling that prompted the check; are there any symptoms you can connect after the fact? It could save someone a forced landing in the future.

[DaveF]

I've only got about 25 hours on my MT, so not much of a sample size, but no problems. I hope it stays that way, because I'd sure hate to go back to the Hartzell. The MT outperforms the Hartzell in every way, almost unbelievably so.

[stogie17]

mt2.jpg

I will try to send a picture. I don't know what caused my uneasiness but have been at it for 50 years and 10,000 hrs of field helicopter work taught me if I ever feel uneasy land now till it is reconciled. I think maybe your subconscious can pic up something maybe our conscientious mind doesn't. Has saved me several times.
/Users/Krista/Desktop/mt2.jpg

[stogie17]

Every composite prop I have seen has had surface cracks on finish from flexing. Mt addresses this in their inspection manual.I have sent them macro photo of this for their opinion and they always say nothing to worry about. Bubble looking area on flat surface can happen too from pitch seeping from wood. Wood is not a bad medium as it actually is very good in flexing hence the bow. Small nicks are repaired with two part epoxy. I had some very small cracks and wrinkling of finish in the root area where major cracks are now. They were exactly like a few near tip. At annual last week we inspected, talked about them sealed and watched. Obviously not enough is know about that to inspect them. Having done many major glass jobs myself as in hundreds of gallons of epoxy and polyester resins it appears to me that their was not good bond to wood. A good bond will tear out wood itself not peel away.

[canav8]

Every composite prop I have seen has had surface cracks on finish from flexing. Mt addresses this in their inspection manual.I have sent them macro photo of this for their opinion and they always say nothing to worry about. Bubble looking area on flat surface can happen too from pitch seeping from wood. Wood is not a bad medium as it actually is very good in flexing hence the bow. Small nicks are repaired with two part epoxy. I had some very small cracks and wrinkling of finish in the root area where major cracks are now. They were exactly like a few near tip. At annual last week we inspected, talked about them sealed and watched. Obviously not enough is know about that to inspect them. Having done many major glass jobs myself as in hundreds of gallons of epoxy and polyester resins it appears to me that their was not good bond to wood. A good bond will tear out wood itself not peel away.

Stogie17, I have seen delams in MT props early on. Do you know when this prop was produced? not the date it entered into service. The early MT props had a rash of these problems. They also had a problem with blade erosion. I would hit MT up with a manufacturers defect claim and follow up with a service difficulty report(SDR) with the FAA. D

[stogie17]

Though has 500 hours since 09 overhaul it was older prop and Mt has since changed the lay up at back of blade now wrapping glass around trailing edge and other improvements. MT Usa has been super nice admitted should not have happened and are trying to get me back in air quickly. FSDO did look at prop and according to my maint facility who spoke with them said reported their opinion that the structural integrity of blade did not appear to be compromised which is actually the wood core as Mt says.

[bagarre]

How bad was the delamination?
My dad had about 2 inches lift up on a prop tip (not an MT prop) and he said it felt like the motor was going to come off before he got the power back. Luckily, was was in the pattern.