rampil
Joined: 04 May 2007
Posts: 870
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 Posted: Thu Jun 21, 2007 6:31 am Post subject: Flutter Note from Bud Yerly |
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Everyone,
I've been in communication with the FAA, John Wheeler and the Europa staff assisting them where possible on the latest accidents.
In my aviation career I have lost too many fellow aviators, and the loss of Ken and William hurt a lot.
One thing I have learned as an aviator, supervisor, and accident investigator, we all must learn from these accidents.
The US Europa Fleet is not grounded but, it is imperative that we inspect our aircraft ASAP.
Ira Rampil mentioned to me about the Matronics site, and normally I don't keep up with it as I get plenty of emails of my own from builders. I was glad to see the important emphasis you all have about the need to check our aircraft thoroughly on pre-flights as well during building and periodic inspections.
In my building and flight testing, I have come across some great aircraft and some in need of TLC. One thing that can kill without warning, is flutter. I've included below an email discussion with Ron Parigoris about flutter:
It is absolutely imperative that you have your tailplane torque tube pins (TP-14s) tight. Should the supplied pins not be absolutely tight, I ream the holes and machine new pins to zero tolerance. I use dry ice to shrink the pins to slide them in if necessary. ( A few firm taps is normally needed with warm pins) Any movement between the stabs is cause to inspect and remedy. Europa has the Mod 62 which enlarges the holes to 3/8 inch giving the careful builder a chance to get firm stabs and reduce the load on the pins, minimizing the chance of wear later on. Also, the TP-13 and TP-16 bushes for the drive pins and trim tabs must be snug and well secured. Should flight be attempted with the TP-16s missing, and or a sloppy torque tube or drive pin assembly, the trim tabs could begin to flutter and the stab will cause such loads on the fuselage and tailplane attach points that the aircraft could destroy itself. Remember, the stabs are not individually balanced but are balanced via the torque tube and mass balance arm. Imagine one stab fluttering exactly out of phase with the other and the forces it would put on the fuselage. No glue joint or stiffening can hold up to that!
On a side note, I have also notice two aircraft where the TS-05 was left with the bearing nut loose. Again, a small amount of play in the TP-12 Drive Plates due to loose TP-14s may cause a small flutter (all flutter is bad), and in combination with a sloppy TS-05 the trim tabs can begin to oscillate out of phase with one another because of the T shape of the TS-05 rocking up and down. Again, causing the other stab to oscillate 180 degrees out of phase with the loose one. A little flutter would eventually become big flutter and eventually lead to inflight breakup. When checking movement on preflight and during inspections, the stabs and trim tabs are fiberglass and you can bend the stabs and get movement. I am talking about movement where you feel a definite bump as the stabs move. Call it a jiggle check. The slight movement of the hinges on the trim tab feels like a lot on the end of the trim tab. Hold your finger on the hinge pin and then check for up/down slop of your bushings.
To have the luxury of a removable stab and wing, we then have the responsibility to ensure all the parts which affix our controls and move them, are inspected and 100% serviceable.
If you have not seen the PFA FSBs they are also posted on my customflightcreations.com website. We will have more on the Europa website once reviewed by the accident board.
As for the turning back to the runway. Speed is life. I'm committed to straight ahead (+-15 degrees) until 600 feet. All my patterns have lead me to the conclusion that an XS, with me flying it, won't make it back to the runway from below 400 feet with a 3 second pilot delay time (yea, I'm old and slow). Practice at altitude, fully loaded, and test yourself.
Bud Yerly
Custom Flight Creations
US Europa distributer.
Phone: 813 653-4989
email: budyerly(at)msn.com
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Ira N224XS |
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