Today's Message Index:
----------------------
1. 02:02 AM - Re: Negative Flaps (aerosiam)
2. 02:26 AM - Flap failure - broken wires (aerosiam)
3. 02:36 AM - Front suspension noise (aerosiam)
4. 02:43 AM - Inner tubes (aerosiam)
5. 04:54 AM - Re: Negative Flaps (Thom Riddle)
6. 07:09 AM - Re: Flap failure - broken wires (Hugh McKay)
7. 09:01 AM - Re: Re: Negative Flaps (Brad Kramer)
8. 12:39 PM - Re: Negative Flaps (Thom Riddle)
Message 1
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Subject: | Re: Negative Flaps |
My 2006 Allegro has negative flaps. A few thoughts....
The design is for neg flaps. If the flaps are set 0, then about 5 degrees is added
to the flap settings (unless the microswitch positions are altered). That
means take off at 20 deg not 15 which may lengthen the run. Also full would be
53 deg which suggests the Vfe should be reduced. Are the hinges etc designed
to allow for that extra force with 10% more full flap?
Neg flaps improve the performance by reducing drag ( exactly in the opposite way
to having flaps down.) Climb, cruise, glide and economy will be better.
Althoug neg flaps are more associated with gliders, more SLAs have them such as
the good-performance Virus and CT2
One downside is that neg flaps reduce the washout. In theory, the aileron span
will stall earlier (in a clean stall) than the flapped span because it is at a
higher angle of attack. In practice, the Allegro design has enough washout built
in so this does not happen. However, I fitted vortex generators to my plane
with closer spacing outboard and this noticably reduced the wing drop at the
stall.
My suggestion is don't alter a basic design parameter.
Paul
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http://forums.matronics.com/viewtopic.php?p=291384#291384
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Subject: | Flap failure - broken wires |
There is a vertical post next to the flap motor with 3 microswitches to control
flap travel. A computer ribbon with 9 wires is used to connect to it.
I have had 2 flap failures because of broken wires.
The problem is that the gage of the wire in the ribbon is very small . I fly from
a grass strip that is not smooth and the solder joints can break especially
the top ones which are longest and most affected by vibration.
One solution is to connect the ribbon to heavier 18 gage wire and solder that to
the terminals which have a hole so they can be well secured.
When I checked all the joints before repairing, another joint broke just by touching
it. This may be an issue for older planes or those not operating from smooth
runways.
Paul
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http://forums.matronics.com/viewtopic.php?p=291386#291386
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Subject: | Front suspension noise |
The climate in Thailand is not good for rubber products. On our 4 year old plane,
the rubber on the nose leg has worn or shrunk so there was a clonking noise
whenever the suspension moved.
The solution was to insert a 1 mm brass spacer ring between the rubber block and
the collar underneath it. It is an easy job. After unbolting the nose fork,
the rivetted collar above can be removed and the spacer inserted.
Paul
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I have had problems 4 times with inner tubes.
2 punctures, 1 valve failure and 1 where the side of the tube wore through.
The inner tubes are made in Vietnam and I am not sure the quality is good. I always
had difficulty attaching footpump hoses to them and replaced them with new
inner tubes with valves at 90 degrees which also solves the problem of getting
to the the valves with wheelpants on.
Paul
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Subject: | Re: Negative Flaps |
Brad,
Have you actually measured the flap position when set to "0"? When I owned N221FA
I checked the flaps in "0" position and they looked slightly reflexed to me,
but I didn't actually measure them. 4 1/2 degrees is pretty small amount visually
on a short chord flap but enough aerodynamically on a clean airframe to
make a difference.
If you decide to measure them, you might want to consider putting a little upwards
pressure on them when measuring to take out the slack in the control system.
Not sure which way the aerodynamic forces will push them in the "0" position
but a little bit of slack would affect the measurement noticeably. Unless the
manual says to make this measurement by comparing to the ailerons, I think it
would be more appropriate to measure against the bottom camber of the wing just
ahead of the flap. One reason for this is that the aileron rigging could be
uneven from one side to the other for fine tuning of roll trim.
Thom
--------
Thom Riddle
Buffalo, NY
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
An ounce of action is worth a ton of theory.
- Friedrich Engels
Read this topic online here:
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Message 6
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Subject: | Re: Flap failure - broken wires |
Paul, Jim, Brad, Thom, et al,
Paul, thanks for your insight concerning the negative flap question I
posted. Mine will stay at 4.5 degrees negative.
Concerning the broken wire problem on the electric flap drive; I too fly out
of a turf runway and I have had the same broken wire problem, but only
once. However, another problem that I have had is related to the screw drive
for the flaps and the flexible metal plate that trips the micro switches.
When the screw drive motor engages the round vertical screw housing that
holds the flexible metal plate rotates slightly (slack) as the screw
engages. This slight rotation of course causes the attached flexible metal
plate to shift slightly. In my case this slight rotational slack caused the
metal plate to shift out of position just enough to cause the micro switch
to catch on the edge and bend the switch arm and break the switch. This
happened two times before I figured out what was happening. The flexible
metal plate was not wide enough to compensate for this rotational slack. My
solution to the problem was to fabricate a wider flexible metal plate. This
took care of the problem.
The original tires for the Allegro 2000 are cheap thin wall tires that have
poor rigidity, and yes the inner tubes are poor quality. I have had only one
flat tire in 3 years of flying, and that was a slow leak down over night
while sitting in the hanger. Thank goodness it was slow and while I was on
the ground. After taking the tire off and checking the tire and tube I found
that the side wall of the tire was cracked in three small places at the
points where the tire mould came together to form the outer shape of the
tire. One of the other tires was also beginning to crack at the mould seams.
This slight crack, combined with the already weak side wall strength which
allowed the tire itself to flex more than it should on normal on landings,
created a situation that allowed a slight pinching to occur on the inner
tube where the crack was located. This flexing of the side wall, the slight
crack in the side wall, and the resulting minute pinching on the inner tube
over time worked it's way through the tube resulting in the final leak down
over night.
As a result of this I changed all of my tires to 8 ply tires with tubes. I
suggest that everyone who has the original tires on their Allegro check them
carefully and on a regular basis before every flight. If you find any
visible cracking of the side wall, get new tires!
Hugh McKay
Allegro 2000
Rotax 912
N661WW
--------------------------------------------------
From: "aerosiam" <pk@aero-siam.com>
Sent: Tuesday, March 23, 2010 5:26 AM
Subject: Allegro-List: Flap failure - broken wires
>
> There is a vertical post next to the flap motor with 3 microswitches to
> control flap travel. A computer ribbon with 9 wires is used to connect to
> it.
> I have had 2 flap failures because of broken wires.
>
> The problem is that the gage of the wire in the ribbon is very small . I
> fly from a grass strip that is not smooth and the solder joints can break
> especially the top ones which are longest and most affected by vibration.
>
> One solution is to connect the ribbon to heavier 18 gage wire and solder
> that to the terminals which have a hole so they can be well secured.
>
> When I checked all the joints before repairing, another joint broke just
> by touching it. This may be an issue for older planes or those not
> operating from smooth runways.
>
> Paul
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=291386#291386
>
>
>
Message 7
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Subject: | Re: Negative Flaps |
Hi Thom,
Somehow I just KNEW I should ask you about our plane, instead of firing o
ff answers when I'm in a hotel and not at the airport. You're right... 4.
5 degrees is very little to see given the length of the flaps. So... Hugh
, let me retract my answer and defer to others who have actually made som
e measurements.
Thom... hoping you make it to OSH. I'm 80% sure I'll be there working dep
arture briefings and being a tent rat again. (Hopefully with the Allegro,
instead of Delta Airlines).
...brad.
-----Original Message-----
From: Thom Riddle [mailto:riddletr@gmail.com]
Sent: Tuesday, March 23, 2010 06:54 AM
Subject: Allegro-List: Re: Negative Flaps
measured the flap position when set to "0"? When I owned N221FA I checke
d the flaps in "0" position and they looked slightly reflexed to me, but
I didn't actually measure them. 4 1/2 degrees is pretty small amount visu
ally on a short chord flap but enough aerodynamically on a clean airframe
to make a difference. If you decide to measure them, you might want to c
onsider putting a little upwards pressure on them when measuring to take
out the slack in the control system. Not sure which way the aerodynamic f
orces will push them in the "0" position but a little bit of slack would
affect the measurement noticeably. Unless the manual says to make this me
asurement by comparing to the ailerons, I think it would be more appropri
ate to measure against the bottom camber of the wing just ahead of the fl
ap. One reason for this is that the aileron rigging could be uneven from
one side to the other for fine tuning of roll trim. Thom -------- Thom Ri
ddle Buffalo, NY Kolb Slingshot SS-021 Jabiru 2200A #1574 Tennessee Prop
64x32 An ounce of action is worth a ton of theory. - Friedrich Engels Rea
d this topic online here: http://forums.matronics.com/viewtopic.php?p=2
=============
Message 8
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Subject: | Re: Negative Flaps |
Hi Brad,
Now my curiosity has been piqued. When you get back home and have a chance, it
would be nice to know if your Allegro does have reflexed flaps as I suspect it
does.
Without a digital angle instrument it is very easy to determine the reflex (if
any) by simply measuring the distance from the top of a straight edge laid along
the bottom camber of the wing up to the trailing edge of the flap. That divided
by the chord of the flap gives you sine of the angle you are looking for.
Arcsine of that number gives you the angle. It would not surprise me to learn
that there is some difference between the two flaps because that is another
way to adjust roll trim.
Thom
--------
Thom Riddle
Buffalo, NY
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
An ounce of action is worth a ton of theory.
- Friedrich Engels
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=291465#291465
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