Today's Message Index:
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1. 07:02 AM - FW: Flutter (nick)
2. 07:59 PM - Re: Flutter (N1BZRich@AOL.COM)
Message 1
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-----Original Message-----
From: nick [mailto:nick@flylightning.net]
Sent: Monday, September 12, 2011 8:53 AM
Subject: RE: Lightning-List: Flutter
I would be curious to see a picture of the "feathers" under the tail.
These are certainly not something we would have suggested here and most
likely something the builder "experimented" with.
So send some pictures on.
Also a good check of the bellcranks and pushrods in the systems is in
order.
Make sure all jam nuts are tight and bolts are installed correctly. One
place I have seen slop is in the bellcrank at the seat bulkhead. IF the
picot area is drilled porrly this will elongate over time. Also there is
supposed to be a bronze bushing there, I have seen builder omit this for
some odd reason and than the bolt rides on the aluminum wearing it out.
We have tested the lightning design extensively at speeds well above Vne
for flutter and other problems and found none. IT most likely is
something else.
Nick
-----Original Message-----
From: owner-lightning-list-server@matronics.com
[mailto:owner-lightning-list-server@matronics.com] On Behalf Of Ralph
Leach
Sent: Saturday, September 10, 2011 8:35 PM
Subject: Lightning-List: Flutter
<lerch268@bellsouth.net>
Folks, Just bought N8938T, serial #62. The aircraft has a total of 150
hours.
Today two of us made the first flights since purchase. All went well
until we
got up to about 125 IAS and encountered some light turbulence. At that
point we
started getting a low frequency, high amplitude flutter in the
elevator. This
lasted for 3-4 seconds. Each time we hit a thermal it would happen
again. It
does not occure below 90 IAS. This bird has "feathers" on the underside
of the
horizontal stabilizer. Could thesecause this condition? Has anyone
encountered or heard of some one that has? Any info would be
appreciated. We
suspect an out of balance elevator. Thanks in advance, Ralph Lerch
lerch268@bellsouth.net cell 828-266-2064
Message 2
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Ralph,
Congratulations on your Lightning purchase. I know when you get this
current issue fixed, you will really enjoy the airplane. But to start out
with - what the heck are "feathers"? With over 40 years in aviation, I
have never head that term associated with airplanes - other than feathering a
propeller, and I'm sure that has nothing to do with your concern. What am
I missing here?
Nick has already mentioned checking for possible "slop" or looseness
in the elevator control system, and this is the first thing to check. But I
have some other questions as to your airplane's elevator set up. First,
do you still have the original artificial pitch trim set up with bungees, or
does your Lightning have the new trim tab set up. If so, also make sure
the trim tab hinge is not sloppy or loose.
Also, does your elevator have the original set up with the aerodynamic
counter balance outside the outside hinge. This aerodynamic counter
balance was good to lighten elevator forces (too light for some pilots) and as
a
result, it was eliminated early on. If you do still have this counter
balance it would tend to make any looseness or sloppiness in the control
system that Nick talked about much more noticeable.
As long as I am asking questions (like what are feathers), let me also
ask if the stick was moving when you felt what you described as flutter?
With worn hinges you can sometimes get what I would call a vibration or
"buzz" instead of an actual flutter. But the stick does not move or vibrate.
So my bottom line is exactly what Nick said - check for looseness or
sloppiness in the control system. If the airplane was built according to
plans and the control system is intact, you should not have any concern about
flutter in pitch or roll. Again, as Nick mentioned, he and I both tested
for flutter to well above the airplane's VNE.
Blue Skies,
Buz Rich
In a message dated 9/10/2011 9:38:02 P.M. Eastern Daylight Time,
lerch268@bellsouth.net writes:
--> Lightning-List message posted by: Ralph Leach <lerch268@bellsouth.net>
Folks, Just bought N8938T, serial #62. The aircraft has a total of 150
hours.
Today two of us made the first flights since purchase. All went well
until we
got up to about 125 IAS and encountered some light turbulence. At that
point we
started getting a low frequency, high amplitude flutter in the elevator.
This
lasted for 3-4 seconds. Each time we hit a thermal it would happen again.
It
does not occure below 90 IAS. This bird has "feathers" on the underside
of the
horizontal stabilizer. Could these cause this condition? Has anyone
encountered or heard of some one that has? Any info would be appreciated.
We
suspect an out of balance elevator. Thanks in advance, Ralph Lerch
lerch268@bellsouth.net cell 828-266-2064
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