Today's Message Index:
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1. 09:14 AM - Re: Low frequency vibration noise (theo van duin)
2. 09:28 AM - Re: Low frequency vibration noise (Brad Kramer)
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| Subject: | Re: Low frequency vibration noise |
Fellow Allegro-Listers,
Talking with a light aircraft owner, I was told that some of his friends
experienced
a low frequency noise in the headset that appeared to be related to the
flashing action
of the strobe lights during flight. I will soon find out if this is true in
my case also.
Did anyone have this experience with an Allegro aircraft?
Theo (in France)
Allegro 2000 (71MM)
2009/10/30, theo van duin <t.j.vanduin@gmail.com>:
>
> Hugh, Amy and Brad,
>
> Thanks for your comments. I will check on the items you mentioned. It's
> obvious that the propeller tracking check is a must and rather
> easy to perform.
>
> Theo (in France)
> Allegro 2000 (71MM)
>
>
> 2009/10/28, Hugh MCKAY III <hgmckay@bellsouth.net>:
>
>> Theo:
>>
>> Just "Google" the words *Propeller Tracking* and you will find the first
>> listing to be a video of how to track a wooden propeller. The principal
is
>> the same for a three blade prop. It is easy to do. For the 912 UL engine
I
>> would suggest you remove one of the plugs from each of the four cylinder
s to
>> relieve the cylinder compression before you track the prop. You can also
>> check with one of your airplane mechanic friends and he can explain trac
king
>> further if you need help.
>>
>> The full take-off power of your engine (5200 rpm) is somewhat low due to
>> the coarse pitch of the blades, but acceptable. Rotax's maximum engine
>> take-off speed is 5800 rpm for no more than 5 minutes, and the maximum
>> continuous engine rpm is 5500 rpm. The maximum rpm for your Woodcomp 3 b
lade
>> prop is 2700 rpm. At your maximum engine rpm of 5200 rpm, the prop speed
is
>> only 2291 rpm which is well below the maximum allowed by Woodcomp. To
>> increase the maximum take-off speed of your engine you would need to
>> decrease the propeller pitch slightly. Unless you have someone who knows
how
>> to do this, and has done it in the past, I would not attempt it yourself
.
>>
>> However, you can check the tracking of the blades, and I would recommend
>> that you do so.
>>
>> Hugh
>>
>> --- On *Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com>* wrote:
>>
>>
>> From: theo van duin <t.j.vanduin@gmail.com>
>> Subject: Re: Allegro-List: Low frequency vibration noise
>> To: allegro-list@matronics.com
>> Date: Tuesday, October 27, 2009, 11:21 AM
>>
>> Hugh,
>>
>> The noise was there from the first time we flew with the plane however
>> remarkably it did not attrack Andr=E9's
>> attention, as he told me. Andr=E9 checked the pitch of the blades and th
ese
>> were found to be O.K.
>> However, an experienced pilot/instructor told us once that to his opinio
n
>> the pitch of the blades was adjusted too coarse. At full power
>> the tachometer reaches something like 5200 r.p.m.
>>
>> I don't think that the tracking was checked and honestly I'm not quite
>> sure what "tracking" exactly means and
>> how this checking could be done.
>>
>> About propeller damage: initialy there was none. At one occasion, the
>> engine was started over a gravel path
>> and after that I found damages on two blades: 3 small holes of the size
of
>> a match head.
>>
>> Maybe you are right about the cause of the vibration noise being somethi
ng
>> electric. This brings me to the next problem I'ld like to resolve by put
ting
>> it on the Allegro list. My radio.
>>
>> Thank you Hugh for your comments,
>> Theo van Duin
>> (France)
>> Allegro 2000
>> (71MM)
>>
>>
>>
>> 2009/10/27, Hugh MCKAY III <hgmckay@bellsouth.net<http://us.mc838.mail.y
ahoo.com/mc/compose?to=hgmckay@bellsouth.net>
>> >:
>>>
>>> Theo:
>>>
>>> When did you first begin to hear this noise? I may be wrong, but at one
>>> to two Hz, I don't think it would be related to an out of balance prop
>>> because the Woodcomp prop blades were balanced at the factory and match
ed to
>>> the hub by numbers 1 thru 3. Because of their construction, they have l
ittle
>>> rotational mass relative to the rotating mass of the engine. Therefore
they
>>> would have little effect unless one has been damaged, or one is severel
y out
>>> of pitch. Have you checked the tracking and pitch of your prop? If thos
e two
>>> items are correct I would begin to look elsewhere for the cause, such a
s an
>>> electrical problem, but at such a low frequency it is hard to imagine t
he
>>> problem being electrical. Others on this forum may have some better ide
as.
>>>
>>> Hugh McKay
>>> Allegro 2000
>>> N661WW
>>> Rotax 912
>>>
>>> --- On *Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com<http://us.m
c838.mail.yahoo.com/mc/compose?to=t.j.vanduin@gmail.com>
>>> >* wrote:
>>>
>>>
>>>
>>> From: theo van duin <t.j.vanduin@gmail.com<http://us.mc838.mail.yahoo.c
om/mc/compose?to=t.j.vanduin@gmail.com>
>>> >
>>> Subject: Allegro-List: Low frequency vibration noise
>>> To: allegro-list@matronics.com<http://us.mc838.mail.yahoo.com/mc/compos
e?to=allegro-list@matronics.com>
>>> Date: Tuesday, October 27, 2009, 6:28 AM
>>>
>>> Fellow Allegro listers,
>>>
>>> When flying my Allegro I regularly do hear a low frequency vibration
>>> noise (about 1 to 2 Hz)
>>> in my headphone, especially during climb. The motor is a Rotax 912 UL.
>>> The prop is a
>>> Woodcomp Klassic 160/31R.
>>> It might not be a motor vibration, but coming from somewhere else. I'm
>>> very curious to
>>> find out from where. Could it be related to an unbalance of my propelle
r
>>> or an incorrectly
>>> adjusted pitch of the blades?
>>>
>>> Thanks for any comment on this,
>>>
>>> Theo van Duin, France
>>> Allegro 2000 (71MM)
>>>
>>> *
>>>
>>> rel=nofollow target=_blank>http://www.matronics.com/Navigator?Alleg
ro-List
>>> et=_blank>http://forums.matronics.com
>>> llow target=_blank>http://www.matronics.com/contribution
>>> *
>>>
>>> *
>>>
>>> target="_blank" href="http://www.matronics.com/Navigator?Allegro-Li
st">http://www.matronics.com/Navigator?Allegro-List
>>> target="_blank" href="http://forums.matronics.com/">http://forums.m
atronics.com
>>> target="_blank" href="http://www.matronics.com/contribution">http:/
/www.matronics.com/contribution
>>> *
>>>
>>>
>> *
>>
>> rel=nofollow target=_blank>http://www.matronics.com/Navigator?Allegr
o-List
>> et=_blank>http://forums.matronics.com
>> llow target=_blank>http://www.matronics.com/contribution
>> *
>>
>> *
>>
===========
===========
===========
===========
>> *
>>
>>
>
Message 2
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| Subject: | Low frequency vibration noise |
If I listen carefully with the engine at idle I can hear a small click
when
the strobes flash, but otherwise I don't notice anything. I can also
hear a
slight noise sometimes when the transponder replies.
Of course that could be different for each plane depending on the radio,
intercom and headsets you're using.
In my case I'm using an iCom A200 radio, Flightcom intercom, KT76A
transponder and Telex ANR4150 headset.
...brad.
N221FA
Bismarck ND
-----Original Message-----
From: owner-allegro-list-server@matronics.com
[mailto:owner-allegro-list-server@matronics.com] On Behalf Of theo van
duin
Sent: Thursday, December 10, 2009 11:14 AM
Subject: Re: Allegro-List: Low frequency vibration noise
Fellow Allegro-Listers,
Talking with a light aircraft owner, I was told that some of his friends
experienced
a low frequency noise in the headset that appeared to be related to the
flashing action
of the strobe lights during flight. I will soon find out if this is true
in
my case also.
Did anyone have this experience with an Allegro aircraft?
Theo (in France)
Allegro 2000 (71MM)
2009/10/30, theo van duin <t.j.vanduin@gmail.com>:
Hugh, Amy and Brad,
Thanks for your comments. I will check on the items you mentioned. It's
obvious that the propeller tracking check is a must and rather
easy to perform.
Theo (in France)
Allegro 2000 (71MM)
2009/10/28, Hugh MCKAY III <hgmckay@bellsouth.net>:
Theo:
Just "Google" the words Propeller Tracking and you will find the first
listing to be a video of how to track a wooden propeller. The principal
is
the same for a three blade prop. It is easy to do. For the 912 UL engine
I
would suggest you remove one of the plugs from each of the four
cylinders to
relieve the cylinder compression before you track the prop. You can also
check with one of your airplane mechanic friends and he can explain
tracking
further if you need help.
The full take-off power of your engine (5200 rpm) is somewhat low due to
the
coarse pitch of the blades, but acceptable. Rotax's maximum engine
take-off
speed is 5800 rpm for no more than 5 minutes, and the maximum continuous
engine rpm is 5500 rpm. The maximum rpm for your Woodcomp 3 blade prop
is
2700 rpm. At your maximum engine rpm of 5200 rpm, the prop speed is only
2291 rpm which is well below the maximum allowed by Woodcomp. To
increase
the maximum take-off speed of your engine you would need to decrease the
propeller pitch slightly. Unless you have someone who knows how to do
this,
and has done it in the past, I would not attempt it yourself.
However, you can check the tracking of the blades, and I would recommend
that you do so.
Hugh
--- On Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com> wrote:
From: theo van duin <t.j.vanduin@gmail.com>
Subject: Re: Allegro-List: Low frequency vibration noise
Hugh,
The noise was there from the first time we flew with the plane however
remarkably it did not attrack Andr=E9's
attention, as he told me. Andr=E9 checked the pitch of the blades and
these
were found to be O.K.
However, an experienced pilot/instructor told us once that to his
opinion
the pitch of the blades was adjusted too coarse. At full power the
tachometer reaches something like 5200 r.p.m.
I don't think that the tracking was checked and honestly I'm not quite
sure
what "tracking" exactly means and
how this checking could be done.
About propeller damage: initialy there was none. At one occasion, the
engine
was started over a gravel path
and after that I found damages on two blades: 3 small holes of the size
of a
match head.
Maybe you are right about the cause of the vibration noise being
something
electric. This brings me to the next problem I'ld like to resolve by
putting
it on the Allegro list. My radio.
Thank you Hugh for your comments,
Theo van Duin
(France)
Allegro 2000
(71MM)
2009/10/27, Hugh MCKAY III <hgmckay@bellsouth.net
<http://us.mc838.mail.yahoo.com/mc/compose?to=hgmckay@bellsouth.net>
>:
Theo:
When did you first begin to hear this noise? I may be wrong, but at one
to
two Hz, I don't think it would be related to an out of balance prop
because
the Woodcomp prop blades were balanced at the factory and matched to the
hub
by numbers 1 thru 3. Because of their construction, they have little
rotational mass relative to the rotating mass of the engine. Therefore
they
would have little effect unless one has been damaged, or one is severely
out
of pitch. Have you checked the tracking and pitch of your prop? If those
two
items are correct I would begin to look elsewhere for the cause, such as
an
electrical problem, but at such a low frequency it is hard to imagine
the
problem being electrical. Others on this forum may have some better
ideas.
Hugh McKay
Allegro 2000
N661WW
Rotax 912
--- On Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com
<http://us.mc838.mail.yahoo.com/mc/compose?to=t.j.vanduin@gmail.com> >
wrote:
From: theo van duin <t.j.vanduin@gmail.com
<http://us.mc838.mail.yahoo.com/mc/compose?to=t.j.vanduin@gmail.com> >
Subject: Allegro-List: Low frequency vibration noise
<http://us.mc838.mail.yahoo.com/mc/compose?to=allegro-list@matronics.co
m>
Fellow Allegro listers,
When flying my Allegro I regularly do hear a low frequency vibration
noise
(about 1 to 2 Hz)
in my headphone, especially during climb. The motor is a Rotax 912 UL.
The
prop is a
Woodcomp Klassic 160/31R.
It might not be a motor vibration, but coming from somewhere else. I'm
very
curious to
find out from where. Could it be related to an unbalance of my propeller
or
an incorrectly
adjusted pitch of the blades?
Thanks for any comment on this,
Theo van Duin, France
Allegro 2000 (71MM)
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