VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 11-05-2018, 04:36 PM
catmandu's Avatar
catmandu catmandu is offline
 
Join Date: Dec 2005
Posts: 680
Default Tail buffet at stall?

Uncharacteristically, after reading a few threads and not finding a similar situation, I am going to shoot from the hip with less than total information available. Please be gentle.

I flew an RV-9a with a relatively dirty aerodynamic snapshot: less than streamlined but secure cowl, rough paint, no fairings or pants on the gear, yet to be calibrated (by me, anyway) pitot static system. When I stalled it with full flaps at altitude to set my indicated airspeed for landing, it was an as advertised docile stall, but enough noise behind me to take a look. Seemed as if the upward deflected trailing edge of the elevator was rather, ahem, excited. Not much feedback in the stick.

Typical for the configuration?
__________________
Mike C.
Maryland's Eastern Shore
stuck in 1/5th of an Arrow, my partners won't let me go
RV-6A bought flying
Reply With Quote
  #2  
Old 11-05-2018, 05:16 PM
grubbat's Avatar
grubbat grubbat is offline
 
Join Date: May 2012
Location: Ga
Posts: 577
Default No mine

Ive never experienced this on my -9.
Scott may comment more precisely on the factory model.
__________________
Craig

RV-3 Sold
RV-4 Sold
C-140 In a barn
Maule MXT-7 Sold
RV-6a Sold
Twin Comanche - Sold
RV-9 IO-360 CS, Built and Flying
J3-65 Cub - low and slow stuff
Comanche 260 - poor mans RV-10
Reply With Quote
  #3  
Old 11-05-2018, 05:34 PM
ALagonia ALagonia is offline
 
Join Date: Jul 2017
Posts: 99
Default

I haven't had my 9 very long but have done at least 20 stalls and have not experienced what you describe. Docile stall characteristic requiring just a slight bit of rudder to raise the left wing.
Reply With Quote
  #4  
Old 11-05-2018, 05:39 PM
JohnInReno's Avatar
JohnInReno JohnInReno is offline
 
Join Date: Jun 2005
Location: Prescott Valley/Chandler AZ
Posts: 296
Default Not mine

Nothing like that - ever. First 10 hours was dirty with no wheel pants or legs.
__________________
John Morgensen
RV-9A N946PM 600+ hours since 2013
Nevada/Arizona
Reply With Quote
  #5  
Old 11-05-2018, 06:30 PM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,097
Default

I have a bit of time in a friends 9A and spent much of it exploring the stall. This airplane behaved just as you describe. With the stick held full back and floating down, the tail shakes like a wet dog. The -8 and the Rocket are similar, but not as bad as the 9.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI instalation in work
RV-8 - Flying
1940 Taylorcraft BL-65 -flying
Reply With Quote
  #6  
Old 11-05-2018, 08:55 PM
William William is offline
 
Join Date: Nov 2006
Location: Wimauma Airpark, Florida (FD77)
Posts: 407
Default

Quote:
Originally Posted by catmandu View Post
Uncharacteristically, after reading a few threads and not finding a similar situation, I am going to shoot from the hip with less than total information available. Please be gentle.

I flew an RV-9a with a relatively dirty aerodynamic snapshot: less than streamlined but secure cowl, rough paint, no fairings or pants on the gear, yet to be calibrated (by me, anyway) pitot static system. When I stalled it with full flaps at altitude to set my indicated airspeed for landing, it was an as advertised docile stall, but enough noise behind me to take a look. Seemed as if the upward deflected trailing edge of the elevator was rather, ahem, excited. Not much feedback in the stick.

Typical for the configuration?

Hi Mike nice meeting you today, this is Bill with Davis Aviation. I just remembered the last RV9A I finished a few months ago that we rebuilt the tail section on also had a loud noise in the lower speed range. It was loud enough to have me concerned. It was found to be the rear skirt on the sliding canopy. The owner Added a piece of weather stripping and the noise is gone. It definitely wasn’t a sound I would have attributed to the canopy. It was a loud buffeting sound just as you describe. Perhaps when you come down next week to pick the plane up we will experiment with the weather stripping.

Take care
Bill
__________________
RV6A flying as of November 8, 2016. N717WK

Last edited by William : 11-06-2018 at 05:17 AM.
Reply With Quote
  #7  
Old 11-06-2018, 11:26 AM
catmandu's Avatar
catmandu catmandu is offline
 
Join Date: Dec 2005
Posts: 680
Default

Thanks, folks. It was probably noise coming in through the skirt as Bill said which first got my attention. And I do tend to go deeper into stalls due to spending a lot of time at 35* AOA back in the day, so the wet dog theory may apply. I will put this in the "look further into it but probably nothing" brain file for now, maybe set up some video on it later.

Always nice to get a warm fuzzy from the VAF collective.
__________________
Mike C.
Maryland's Eastern Shore
stuck in 1/5th of an Arrow, my partners won't let me go
RV-6A bought flying
Reply With Quote
  #8  
Old 11-06-2018, 12:05 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,792
Default

Quote:
Originally Posted by catmandu View Post
Thanks, folks. It was probably noise coming in through the skirt as Bill said which first got my attention. And I do tend to go deeper into stalls due to spending a lot of time at 35* AOA back in the day, so the wet dog theory may apply. I will put this in the "look further into it but probably nothing" brain file for now, maybe set up some video on it later.

Always nice to get a warm fuzzy from the VAF collective.
If you deeply stall an RV-9 (easy to do because it is very docile... depending on C.G. position) you can ride the stall down hill with the stick full back with the nose bobing up and down as the wing flow attaches and detaches.
This disturbed airflow will cause a lot of dirty flow over the tail making it shake a lot. With no gear leg or wheel fairings the flow over the tail is probably even dirtier making what you are seeing, even worse.
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #9  
Old 11-06-2018, 05:32 PM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
 
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,783
Default

Quote:
Originally Posted by rvbuilder2002 View Post
If you deeply stall an RV-9 (easy to do because it is very docile... depending on C.G. position) you can ride the stall down hill with the stick full back with the nose bobing up and down as the wing flow attaches and detaches.
This disturbed airflow will cause a lot of dirty flow over the tail making it shake a lot. With no gear leg or wheel fairings the flow over the tail is probably even dirtier making what you are seeing, even worse.
ditto this
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 600+ for all

Simplicity is the art in design.

see Amanda Melton for www.rvplasticparts.com
Reply With Quote
  #10  
Old 11-06-2018, 08:39 PM
simpkinsona simpkinsona is offline
 
Join Date: Dec 2010
Location: Vacaville, CA
Posts: 131
Default Curiosity

I was intrigued by this thread. Id heard of stall buffet being caused by the tail but never investigated it. My 9A has a noticeable buffet just as it breaks in the stall. Today I went out to investigate and sure enough the buffet is from the tail. I watched the tail over my shoulder during the stalls and it definitely shakes and is causing the buffet. It was more pronounced with the flaps up, but present either way.

-Andy
__________________
Andy Simpkinson
RV-9a Subaru engine.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:26 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.