Tail Shake

Pat Stewart · #1 03-31-2014, 07:00 PM

This weekend me and a friend went out for a little practice. While doing a stall the aircraft had a vibration and when I looked back at the tail I was surprised to see how significant the tail was shaking. Anyone else experienced this, it just does not seem like that should be so severe and I wonder what damage it can create. At a minimum I don't think I will ever stall the airplane again.

flightlogic · #2 03-31-2014, 07:06 PM

Yeah... I craned my neck around the other day... while in a deep stall in my (new to me) 9A. The shaking back there made me glad I added the stainless steel straps to bridge the join at vertical and horiz. Hope the rest of the parts hang in there too. Not a habit forming maneuver.
But in the Lancair's some guys never do a stall... for fear that their little tail will let them down and they will die.

Geico266 · #3 03-31-2014, 07:08 PM

Any videos of this?

Pat Stewart · #4 04-01-2014, 06:32 AM

No videos I have run across. I'm sure others have noticed this.

9GT · #5 04-01-2014, 07:34 AM

The RV-10 plane that I used for transition training also did this. I could barely feel it but my instructor told me to look back and sure enough it was bouncing up and down slightly. I have not experienced it in mine as I have not done deep stall testing yet.

crabandy · #6 04-01-2014, 07:39 AM

Not sure about the RV, but during my multi training I had several hours facing backwards (club seating) in a Baron and the tail shook a LOT during stalls.
Checkout the flutter video and watch how much the tail wiggles!
http://www.youtube.com/watch?v=qfkkiDsEXUA

ppilotmike · #7 04-01-2014, 08:28 AM

Someone with a flying RV-10 should use their Go Pro camera facing backwards and do some stalls, so we can see the shake. Is this normal? Is the "buffeting" we feel before an airplane stalls caused by the tail shake? Hopefully, someone smarter than me will help describe what's going on, and perhaps even provide video (excellent)..??

rocketman1988 · #8 04-01-2014, 08:29 AM

The tail shake during the stall is likely due to aerodynamic buffeting caused by the separated flow from the wing. Much different animal than the flutter testing on the comanche in the video. There are numerous articles and videos out there that show, quite graphically, the result of flutter. It is something that has happened a little too close to home...years ago, one of my professors worked for Beech when they were doing flutter analysis. He was an engineer, on the ground watching what happens when a divergent flutter mode occurs. Long story short, the airplane crashed and the pilot didn't make it.

More recently, my Dad was flying a C-421 on the first flight after an annual. Everything was fine climbing through 17k when he heard a bang and the airplane was vibrating violently. Long story short, he was able to get it on the ground safely...with one elevator. Apparently the shop had either used the wrong sized cotter pin or didn't use one in the trim tab linkage. It came loose and the tab flew the elevator back and forth until the bolts holding the two elevator together sheared.

Not pleasant. Flutter is nothing to fool around with...

tadsargent · #9 04-01-2014, 08:35 AM

I am curious to know what is the difference between a Stall and a Deep Stall. I have never heard this reference before today.
Thanks

ppilotmike · #10 04-01-2014, 08:40 AM

Quote:

Originally Posted by rocketman1988

The tail shake during the stall is likely due to aerodynamic buffeting caused by the separated flow from the wing. Much different animal than the flutter testing on the comanche in the video.

That's what I thought. Boy, if 10 pilots were experiencing more "shake" than normal, it could be a real issue. Thanks for clearing this up...