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BW 350 PSRU Failure, please share the word!

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Andreas K

Member
Joined
Aug 18, 2016
Messages
23
Location
Beautiful Wisconsin
Fellow Pilots,

I’d like to share the gearbox failure that I recently experienced in my Vans RV-10.

https://drive.google.com/open?id=0B_...0RTM280TzAyaDg

https://drive.google.com/open?id=0B_...mlmVjJWdEVibUk


My setup:

Airframe: Vans RV-10
Engine: GM LS 7 (approx. 400 hp, 800 ft/lbs of torque @ 2700 prop RPM, WOT @ SL)
PSRU: BW 350 (Bud Warren, Geared Drives), Cast Aluminum Case, 1:1.75 reduction ratio
Propeller: Whirlwind Aviation RV-10 composite prop, 80 inch, 46 lbs

I was in phase one at around 33 hrs. when I experienced a total thrust failure shortly after takeoff. As it turns out the prop shaft of my PSRU broke and caused a disconnect between the engine and the prop.
In my third flight a couple month back I made a 3 G turn for 20 seconds as part of my flight testing.

Several conversations with the manufacturer of the BW350a and BW350b at AUTOPSRUS revealed that this turn caused the gearbox case to flex and misalign the supporting bearings. The prop shaft bent slightly and possibly cracked at this time.
I could fly another 30 hrs. before the shaft finally broke. The shaft is splined at the area of breakage and the core of the shaft is 1.25 inches thick (compare that to a Lycoming main bearing).

I believe a combination of the 3 G turn and torsional vibrations caused fatigue and subsequently shaft failure.
I never used more than 75% of the available power and flew the airplane like an airliner (minimum G’s) except for that one turn.

I am reaching out to you in order to spread the word. Maybe you know somebody who is flying or building an airplane with this PSRU. I destroyed my gearbox because I was unaware that a 3 G turn could do such harm.

Please remember, that I am not an engineer and every setup is different. I CANNOT provide a G-limit that is safe.

I can only suggest to STAY AWAY FROM ANY G’S and STAY OUT OF TURBULENCE

Many Happy Landings

Andreas K
 
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