REFLECTOR: exceeding Vne and Airventure cup race

[TimRhod at aol.com]

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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