My KR2 ailerons are hinged along the top, flush with the top wing skin. What
is the best way to check for proper balance?
On Thursday, January 18, 2018, 10:01:46 AM MST,
<[email protected]> wrote:
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Today's Topics:
1. Flutter and flight testing (svd)
2. weather (Raymond Fuenzalida)
3. Re: weather (Jeff Scott)
4. Re: weather (Kayak)
5. Re: weather (wayne w delisle sr)
6. Re: weather (Randall Smith)
7. Re: weather (Noel McAvena)
----------------------------------------------------------------------
Message: 1
Date: Wed, 17 Jan 2018 11:31:10 -0800
From: svd <[email protected]>
To: "[email protected]" <[email protected]>
Subject: KR> Flutter and flight testing
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
HI All,
Finding your flutter speed sounds pretty important and I may try - carefully.
But we must not forget that flutter can happen at any speed - and can change.
Flutter inducing dynamics increases with speed, but flutter speed can decrease
dramatically with changes in rigging, weight, stiffness (including cracks or
even temperature changes), wear in hinges and bearings, and even rain.
Just two weeks ago I experienced flutter for the first (and hopefully last)
time - at ~80mph!
I have been fixing up a buddy?s Kitfox Model III. Its a fun airplane, but has
a remarkably complex control linkage system for its flapperons. Every linkage
has inherent slop and the the Model III has something like _eleven_ before
reaching the flapperon. Later models reduced the complexity a bit. Compounding
this, the wing design is strong but inherently flexible and the flapperons are
attached on long trailing edge extension of the ribs.
I?ve since removed a remarkable amount of slop from the control system - but as
you can imagine, with a 11 control linkage system there will always be some
slop. Haven?t flown it again yet - but soon perhaps.
How does this translate to the KR?
First of all is respect for the build and maintenance of your airplane. Ensure
the control system and hinges are in good nick with as little slop as possible.
Better to error toward friction (in the linkages) than looseness. That means
that the cables are taught, the pulleys, bell crank and rod linkages are taught
and not worn, and importantly they do not flex. If they flex, they will
eventually crack and fail. Many experimentals were originally designed with
too light bell crank brackets that later had to be modified to reduce flex.
Also, if your hinges are worn, fix or replace.
Balance and rebalance with any mods. And get familiar with the flex of your
ailerons and wing - so than on preflight you can stress them (a bit) and feel
for changes.
Additionally, I will second the depower yank and bank suggestion. But not
yank. As with all, firm but gentle. You may already be close to stress
limits, so easy but firm and decisive to quickly reduce speed.
Perhaps this is all a bit obvious or obsessive - but after a bit of sphincter
tightening flutter, understandable.
from:
https://www.faa.gov/documentlibrary/media/advisory_circular/ac%2090-89a.pdf
<https://www.faa.gov/documentlibrary/media/advisory_circular/ac%2090-89a.pdf>
1. OBJECTIVE. To understand the causes and cures of the condition known as
flutter.
2. DESCRIPTION. Flutter in an aircraft struc- ture is the result of an
interaction between aero- dynamic inputs, the elastic properties of the
structure, the mass or weight distribution of the various ele- ments, and
airspeed.
a. To most people, the word ??flutter?? suggests a flag?s movement as the wind
blows across it. In a light breeze, the flag waves gently but as the wind speed
increases, the flags motion becomes more and more excited. It takes little
imagination to realize if something similar happened to an aircraft struc-
ture, the effects would be catastrophic. The parallel to a flag is appropriate.
b. Think of a primary surface with a control hinged to it (e.g., an aileron).
Imagine that the air- plane hits a thermal. The initial response of the wing is
to bend upwards relative to the fuselage.
c. If the center of mass of the aileron is not exactly on the hinge line, it
will tend to lag behind the wing as it bends upwards.
d. In a simple, unbalanced, flap-type hinged control, the center of mass will
be behind the hinge line and the inertial lag will result in the aileron being
deflected downwards. This will result in the wing momentarily generating more
lift, increasing its upward bending moment and its velocity relative to the
fuselage. The inertia of the wing will carry it upwards beyond its equilibrium
position to a point where more energy is stored in the deformed struc- ture
than can be opposed by the aerodynamic forces acting on it.
e. The wing ??bounces back?? and starts to move downward but, as before, the
aileron lags behind and is deflected upwards this time. This adds to the
aerodynamic down force on the wing, once more driving it beyond its equilibrium
position and the cycle repeats.
f. Flutter can happen at any speed, including take-off speed. At low airspeeds,
however, structural
52
5/24/95
AC 90-89A
and aerodynamic damping quickly suppress the flut- ter motion. But as the
airspeed increases, so do the aerodynamic driving forces generated by the
aileron. When they are large enough to cancel the damping, the motion becomes
continuous.
g. Further SMALL INCREASES will produce a divergent, or increasing oscillation,
which can quickly exceed the structural limits of the air- frame. Even when
flutter is on the verge of becoming catastrophic it can still be very hard to
detect. What causes this is the high frequency of the oscillation, typically
between 5 and 20 Hz (cycles per second). It will take but a small increase in
speed (1?4 knot or less) to remove what little damping remains and the motion
will become divergent rapidly.
h. Flutter also can occur on a smaller scale if the main control surface has a
control tab on it. The mechanics are the same with the tab taking the place of
the aileron and the aileron taking the place of the wing. The biggest
difference are the masses involved are much smaller, the frequencies much
higher, and there is less feed-back through the con- trol system. This makes
tab flutter more difficult to detect. The phenomenon known as ??buzz?? is often
caused by tab flutter. Since flutter is more prevalent at higher speeds, it is
not recommended that the flight test plan call for high speed runs within 10
percent of red line.
i. What can be done about it? Having described how flutter happens, the
following sugges- tions should help reduce the possibility of it happen- ing to
the amateur-builder?s aircraft:
(1) Perform a mass balance of all flight controls in accordance with the
designer/kit manu- facturer?s instructions.
(2) Eliminate all control ??free play?? by reducing slop in rod end bearings,
hinges, and every nut and bolt used in attaching flight controls.
(3) Ensure that all rigging and cable ten- sion is set accurately to the design
specifications using a calibrated cable tensiometer.
(4) Re-balance any flight control if it has been repaired, repainted, or
modified in any way.
NOTE: If the pilot experiences flutter, or believes he did, reduce power
immediately and land as soon as possible. Do not attempt further flight until
the aircraft has been thoroughly inspected for flutter induced damage. This
inspection should include all wing/tail attach points, flight controls, their
attach points/hinges, hardware, control rods, and control rod bearings for
elongated bolt/rivet holes, cracks, (especially rod end bearings) and sheared
rivets.
------------------------------
Message: 2
Date: Wed, 17 Jan 2018 15:39:25 -0600
From: Raymond Fuenzalida <[email protected]>
To: KRnet <[email protected]>
Subject: KR> weather
Message-ID:
<cap94t4dq1anv6sl5thkcw+nrndhfehdsbqxxjm9e4jn2f03...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Just had to state this. You northern guys talk about flying in cold air -
better lift, smoother, no density altitude issues etc.
Well it got cold here and the place is shut down. Couldn't get to the
airport if I wanted to, much less go flying. Or even to work on anything
(work is closed, maybe tomorrow too). I always read those reports of you
guys flying and having a great time in cold air. We're paralyzed. Roads
and bridges are closed. Even the Interstate around here was closed.
There are differences between the north and the south.
Ray_pilot
New Orleans
------------------------------
Message: 3
Date: Thu, 18 Jan 2018 00:04:25 +0100
From: "Jeff Scott" <[email protected]>
To: [email protected]
Subject: Re: KR> weather
Message-ID:
<trinity-edfb24b8-7c46-4dbf-b5a8-bc57ae6cfee4-1516230265561@3c-app-mailcom-bs08>
Content-Type: text/plain; charset=UTF-8
The south isn't very well equipped to deal with snow and ice. I had
my KR out today. Pretty awesome performance in the cold air near sea
level.
-Jeff Scott
Cherokee Village, AR
-----------------
Just had to state this. You northern guys talk about flying in cold air -
better lift, smoother, no density altitude issues etc.
Well it got cold here and the place is shut down. Couldn't get to the
airport if I wanted to, much less go flying. Or even to work on anything
(work is closed, maybe tomorrow too). I always read those reports of you
guys flying and having a great time in cold air. We're paralyzed. Roads
and bridges are closed. Even the Interstate around here was closed.
There are differences between the north and the south.
Ray_pilot
New Orleans
?
------------------------------
Message: 4
Date: Wed, 17 Jan 2018 18:10:22 -0500
From: Kayak <[email protected]>
To: KRnet <[email protected]>
Subject: Re: KR> weather
Message-ID:
<caf6k7fsogf54zvdggfarh13hf7ztuuagxorizgcf+atdsy1...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
well that's all that too...
On Wed, Jan 17, 2018 at 4:39 PM, Raymond Fuenzalida via KRnet
<[email protected]> wrote:
> Just had to state this. You northern guys talk about flying in cold air -
> better lift, smoother, no density altitude issues etc.
> Well it got cold here and the place is shut down. Couldn't get to the
> airport if I wanted to, much less go flying. Or even to work on anything
> (work is closed, maybe tomorrow too). I always read those reports of you
> guys flying and having a great time in cold air. We're paralyzed. Roads
> and bridges are closed. Even the Interstate around here was closed.
> There are differences between the north and the south.
>
>
> Ray_pilot
> New Orleans
> _______________________________________________
> Search the KRnet Archives at
> https://www.mail-archive.com/[email protected]/.
> Please see LIST RULES and KRnet info at http://www.krnet.org/info.html.
> see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change
> options.
> To UNsubscribe from KRnet, send a message to [email protected]
------------------------------
Message: 5
Date: Thu, 18 Jan 2018 08:16:22 -0500
From: wayne w delisle sr <[email protected]>
To: [email protected]
Subject: Re: KR> weather
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8; format=flowed
I love lift! I remember the old Cherokee 140 I trained with. Cold
January days made the 140 into a magic carpet. G
Wayne
oldmoparguy
> KR> weather
>
> Jeff Scott jscott.planes at gmx.com
> Wed Jan 17 18:04:25 EST 2018
> The south isn't very well equipped to deal with snow and ice. I had
> my KR out today. Pretty awesome performance in the cold air near sea
> level.
>
> -Jeff Scott
> Cherokee Village, AR
---
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------------------------------
Message: 6
Date: Thu, 18 Jan 2018 07:51:04 -0600
From: Randall Smith <[email protected]>
To: KRnet <[email protected]>
Subject: Re: KR> weather
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
If you look at the highways up north they?re not doing too well themselves. I
don?t care where you live you can?t drive on ice very well. I drove 18 wheelers
for many years up they?re not that bad driving on snow it?s the ice that Will
get you
Sent from my iPhone
> On Jan 17, 2018, at 5:04 PM, Jeff Scott via KRnet <[email protected]>
> wrote:
>
>
> The south isn't very well equipped to deal with snow and ice. I had
> my KR out today. Pretty awesome performance in the cold air near sea
> level.
>
> -Jeff Scott
> Cherokee Village, AR
>
> -----------------
> Just had to state this. You northern guys talk about flying in cold air -
> better lift, smoother, no density altitude issues etc.
> Well it got cold here and the place is shut down. Couldn't get to the
> airport if I wanted to, much less go flying. Or even to work on anything
> (work is closed, maybe tomorrow too). I always read those reports of you
> guys flying and having a great time in cold air. We're paralyzed. Roads
> and bridges are closed. Even the Interstate around here was closed.
> There are differences between the north and the south.
>
>
> Ray_pilot
> New Orleans
>
>
> _______________________________________________
> Search the KRnet Archives at
> https://www.mail-archive.com/[email protected]/.
> Please see LIST RULES and KRnet info at http://www.krnet.org/info.html.
> see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change
> options.
> To UNsubscribe from KRnet, send a message to [email protected]
------------------------------
Message: 7
Date: Thu, 18 Jan 2018 16:16:44 +0000
From: Noel McAvena <[email protected]>
To: KRnet <[email protected]>
Subject: Re: KR> weather
Message-ID:
<cy4pr22mb087173aca5caf2dffec37cb7bc...@cy4pr22mb0871.namprd22.prod.outlook.com>
Content-Type: text/plain; charset="Windows-1252"
I don't know about that, some of us think driving on ice is a great way to
spend your week-ends this time of year:
https://youtu.be/R1sjKhpdoOI?t=2m27s
[https://i.ytimg.com/vi/R1sjKhpdoOI/maxresdefault.jpg]<https://youtu.be/R1sjKhpdoOI?t=2m27s>
Ice Racing NASCC 2016 Ice Race #5-2 Limited Stud / Neon
Studded<https://youtu.be/R1sjKhpdoOI?t=2m27s>
youtu.be
Canadian NASCC WMCA Ice Racing in 2016. Race day 5, race number 2. In car cam,
go pro.
Of course we also make highways out of ice in this country too.
-Noel-
________________________________
From: KRnet <[email protected]> on behalf of Randall Smith via KRnet
<[email protected]>
Sent: January 18, 2018 1:51:04 PM
To: KRnet
Cc: Randall Smith
Subject: Re: KR> weather
If you look at the highways up north they?re not doing too well themselves. I
don?t care where you live you can?t drive on ice very well. I drove 18 wheelers
for many years up they?re not that bad driving on snow it?s the ice that Will
get you
Sent from my iPhone
> On Jan 17, 2018, at 5:04 PM, Jeff Scott via KRnet <[email protected]>
> wrote:
>
>
> The south isn't very well equipped to deal with snow and ice. I had
> my KR out today. Pretty awesome performance in the cold air near sea
> level.
>
> -Jeff Scott
> Cherokee Village, AR
>
> -----------------
> Just had to state this. You northern guys talk about flying in cold air -
> better lift, smoother, no density altitude issues etc.
> Well it got cold here and the place is shut down. Couldn't get to the
> airport if I wanted to, much less go flying. Or even to work on anything
> (work is closed, maybe tomorrow too). I always read those reports of you
> guys flying and having a great time in cold air. We're paralyzed. Roads
> and bridges are closed. Even the Interstate around here was closed.
> There are differences between the north and the south.
>
>
> Ray_pilot
> New Orleans
>
>
> _______________________________________________
> Search the KRnet Archives at
> https://www.mail-archive.com/[email protected]/.
> Please see LIST RULES and KRnet info at http://www.krnet.org/info.html.
> see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change
> options.
> To UNsubscribe from KRnet, send a message to [email protected]
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