James: Thanks for passing this on...
Regards, Dan
WHIRLWIND PROP ALERT
Please pass this on to anyone who operates a Whirlwind propeller (specifically Series 151 3-blade composite)
I have built and have been flying a Lancair-360 with a Lyc IO-360 / Whirlwind 151 prop combination for approximately 2.5 years and on December 17th of 2007, following a routine 45-minute flight, I experienced medium to severe front end vibration which ultimately resulted in an off-airport forced landing.
While turning onto a deep base leg to allow for slower traffic on final at my home airport I made my final prop pitch adjustment and almost immediately vibration began and intensified within 2-3 seconds. Engine responded appropriately to throttle input, however vibes only got worse with the throttle pushed up. At this point I realized I was flying a 1000 fpm flying speed brake. At 900’ and one and a half miles from the intended runway, no way was I going to make the airport. Saw an available field straight ahead, contemplated the gear-up/gear-down option and chose to take my chances with the gear down (leaving the gear down, in this case, actually proved to be the better choice). Touchdown was approximately 80-85 KIAS (with slight tailwind = 100mph), and rollout was approximately 450’. The nose gear ultimately failed halfway through the rollout as it attempted to muscle through the rain-saturated ground. I was very fortunate in that the ground was relatively flat with no berms, etc. Reality check: sometimes these things happen quickly; the actual time from the moment of failure to the point I’m popping the canopy open on the ground was 45 seconds (no exaggeration, I did the math). Soapbox: advice I can offer; continue to fly the airplane; straight ahead is usually better then attempting a tight turn. We’ve all been taught from day one: aviate, navigate, communicate, in that order. My only mistake was not communicating; a simple “178DM going down” would have sufficed. As it turned out, there were no witnesses on the ground, so the situation could have been dire had I been trapped. Other than a new prop, engine inspection, NG assembly, and cowl work, damage was minimal. Here’s a tidbit; for those who are thinking of incorporating the outback gear; don’t need it in my opinion…the real stresses are on the nose gear.
Back to the prop: post flight analysis revealed that one of the pitch link pins to one of the blades (particularly the pin that fits into the blade ferrule) had pulled itself out, causing the blade to go negative pitch. There were also other stress marks indicating excessive and uneven wear and tear of the bottom of the ferrules where the pins make contact. In addition, this prop had approximately 39 hours (185 hrs total) since the overhaul generated by a Whirlwind service letter (#SL-151-042607) dated 5/4/2007.
The primary reason I solicit this post is to alert anyone who may be operating a Whirlwind series 151 prop with aluminum ferrules. For now, Whirlwind is treating this event as an isolated incident, therefore an AD or some sort of service difficulty letter may or may not be forthcoming.
Please note that since I am not a metallurgist I will not, therefore, comment or formulate an opinion on the design of the prop. The original design is a steel pin fitted into an aluminum blade ferrule (the base which houses the blade). There had been other issues with premature wear and tear of the aluminum ferrules as well. Whirlwind has since begun to manufacture and use steel ferrules blades, in which you have a steel pin fitted into a steel ferrule.
Bottom line: if you have a series 151 aluminum ferrule prop, I would recommend to at least pull the front hub plate and inspect the pins frequently, else bite the bullet and get the steel ferrule blades.
I you have any questions regarding this incident, the manufacturer, lessons learned (i.e. what you can expect following an incident or mishap), pix of the incident (google my name Daniel Lukschander, link WMCTV), or pix of the prop hub, opinions, don’t hesitate to contact me via phone or email.
Respectfully submitted,
Dan Lukschander
[email protected] (901) 218-7401 cel
L-360, N178DM
PS. I’m getting a Hartzell
