REFLECTOR: exceeding Vne and Airventure cup race

[gpoole]

What an interesting read Tim - thanks!  Would you care to fill us in on the
advice you received from Duane on the rudder flutter fix?

 

Greg in Sydney

STd RG E

 <mailto:gregpoole at saaachapter11.com> gregpoole at saaachapter11.com 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of TimRhod at aol.com
Sent: Thursday, 3 August 2006 4:46 PM
To: Reflector at tvbf.org
Cc: TimRhod at aol.com
Subject: REFLECTOR: exceeding Vne and Airventure cup race

 

I have read quite a few comments on the speeds of the velocities in the
airventure cup race an also discussion on exceeding the factory Vne. For
what it is worth I would like to share my experience with both .  I have a
XLRG with a continental IO-550 with 10 to 1 compression pistons  and duel
plasma 3 electronic ignitions. Rated horsepower is 370HP   During my initial
test flying phase I tested flutter characteristics to 210 knots Indicated
with no adverse effects. After 70 flight hours now I entered the airventure
cup race and so in preparation for that I did some more high speed testing.
Knowing that this race would be flown at minimal altitude I first did a full
power level run at 1000ft AGL. I indicated 217Kts straight and level. No
sign of flutter.  Then knowing I would be diving to the pylon turns in the
race I decided to push the indicated speed higher a few knots at a time
shaking the controls to try to induce flutter. I tested to 230Kts indicated
in a straight shallow full power dive. No Adverse effects.   Having decided
I would not fly the plane any faster I was satisfied with the testing.  Next
I started to practice diving to the pylon and banking to turn around a
pylon.  In my first diving turn at about 600 ftAGL right over the airport
all hell started shaking the airplane like a buzzing bee at about 220 kts  I
immediately pulled power and nosed up and the vibration stopped. I was
pretty shook up by the vibration and wanted to get on the ground immediately
in case something decided to come off. So I made a quick high sink nose too
high landing which after getting out of the plane I noticed about 1/2 inch
of my MT prop missing on each blade. UGGGG....  Then I discovered that the
vibration had come from flutter of the left rudder. It was beat up enough
that I had to fill and sand where the rudder meets the fuselage but there
was no apparent sign that it was going to come off at the hinges. If the
flutter had continued it probably would just of destroyed itself  leaving
the hinges attached. Time to  push the plane back into the hanger and  drag
my sorry butt home.  Next day Email MT, Velocity, and Reflectoites what to
do about the prop. All told me to cut it off equally on each blade, epoxy
and or glass the ends, sand and countor, run it and if no vibration it
should be ok. That's what I did.  Now its the day before the race.  I
tightened the return spring on both rudders and decided not to fly faster
than 215 kts level and 200 kts diving and turning.  Race day brought great
weather. On take off as I passed through 210 kts the left rudder started to
flutter again. Pulled power  an it stopped. It was not near so violent this
time probably because of tightening the rudder return spring. Put foot on
left rudder pedal and held pressure then gradually increased speed up to
215kts indicated flying straight and level. As long as held rudder pressure
there was no flutter. So I held left rudder pressure for the entire two hour
race and pulled power and slowed to 200 kts for diving an turning around
pylon turns.  The race ended and I finished with a speed of 230 MPH for the
500 mile race. WE had about a 15mph head wind. The prop worked fine with no
adverse  effect of being an inch shorter.  At Oshkosh I talked to Duane
Swing at length about the rudder flutter and he recommended some diagnostic
work and a fix which I am presently doing. So Next year I should be faster
in the race.   Watch out Pat   I'm on your tail and closing. Congrats this
year on 247MPH . We had a great time at the race an I would encourage lots
of us Velocities to take part next year.  It was really fun, exciting and
memorable.  

 

 Tim Rhodenbaugh

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