Howling noise from nose vent

[toad]

I have a Grob 102 and it's making a very loud noise when flying fast
with the nose vent closed down. The noise comes from the nose area
and goes away when I open the vent.

I would like to be able to close the vent sometimes, because it gets
cold :-)

Any ideas what might be happening ? It didn't always do this.

Todd Smith
3S

[[email protected]]

On Feb 20, 7:17*am, toad > wrote:
> I have a Grob 102 and it's making a very loud noise when flying fast
> with the nose vent closed down. *The noise comes from the nose area
> and goes away when I open the vent.
>
> I would like to be able to close the vent sometimes, because it gets
> cold :-)
>
> Any ideas what might be happening ? * It didn't always do this.
>
> Todd Smith
> 3S

I had a similar problem with my canopy not sealing up front. I added
foam weather-stripping and the problem went away. Nice and quiet now.

[jcarlyle]

Probably what's happening is that the weather sealing around the vent
flap has failed, leaving a small gap when the vent is closed. Have you
checked the sealing of the vent when it's closed?

-John

On Feb 20, 8:17 am, toad > wrote:
> I have a Grob 102 and it's making a very loud noise when flying fast
> with the nose vent closed down. The noise comes from the nose area
> and goes away when I open the vent.
>
> I would like to be able to close the vent sometimes, because it gets
> cold :-)
>
> Any ideas what might be happening ? It didn't always do this.
>
> Todd Smith
> 3S

[[email protected]]

On Feb 20, 8:35*am, jcarlyle > wrote:
> Probably what's happening is that the weather sealing around the vent
> flap has failed, leaving a small gap when the vent is closed. Have you
> checked the sealing of the vent when it's closed?
>
> -John

I'll check that seal if I can. I'm going to try an re-create the
issue on the ground with a shop vac or leaf blower. Of course I might
not be able to hear the vent noise over the motor then :-)

It's not the canopy seal. That used to whistle right by my ear until
I replaced the seal and added foam.

Thanks
Todd

[Eric Greenwell]

wrote:
> On Feb 20, 8:35 am, jcarlyle > wrote:
>> Probably what's happening is that the weather sealing around the vent
>> flap has failed, leaving a small gap when the vent is closed. Have you
>> checked the sealing of the vent when it's closed?
>>
>> -John
>
> I'll check that seal if I can. I'm going to try an re-create the
> issue on the ground with a shop vac or leaf blower. Of course I might
> not be able to hear the vent noise over the motor then :-)
>
> It's not the canopy seal. That used to whistle right by my ear until
> I replaced the seal and added foam.

Be really careful with blowers if the pitot is in the nose and will see
the blower pressure.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

On Feb 20, 6:26*pm, Eric Greenwell > wrote:
> wrote:
> > On Feb 20, 8:35 am, jcarlyle > wrote:
> >> Probably what's happening is that the weather sealing around the vent
> >> flap has failed, leaving a small gap when the vent is closed. Have you
> >> checked the sealing of the vent when it's closed?
>
> >> -John
>
> > I'll check that seal if I can. *I'm going to try an re-create the
> > issue on the ground with a shop vac or leaf blower. *Of course I might
> > not be able to hear the vent noise over the motor then :-)
>
> > It's not the canopy seal. *That used to whistle right by my ear until
> > I replaced the seal and added foam.
>
> Be really careful with blowers if the pitot is in the nose and will see
> the blower pressure.
>
> --
> Eric Greenwell - Washington State, USA
> * Change "netto" to "net" to email me directly
>
> * Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
> * * * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more
>
> * "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

Thanks for the warning, I had not though of it, but I do think that
the pitot in my Grob is from the tail probe. I'll make sure before I
power up the blower. My goal would be about a 120 knot flight
pressure anyway, but might not have the ability to fine tune the
blower.

Thanks
Todd
3S

[[email protected]]

On Feb 20, 10:36*am, wrote:
> On Feb 20, 8:35*am, jcarlyle > wrote:
>
> > Probably what's happening is that the weather sealing around the vent
> > flap has failed, leaving a small gap when the vent is closed. Have you
> > checked the sealing of the vent when it's closed?
>
> > -John
>
> I'll check that seal if I can. *I'm going to try an re-create the
> issue on the ground with a shop vac or leaf blower. *Of course I might
> not be able to hear the vent noise over the motor then :-)
>
> It's not the canopy seal. *That used to whistle right by my ear until
> I replaced the seal and added foam.
>
> Thanks
> Todd

Todd,

When I had my problem, it was the same symptom as yours. When I opened
my vent, the howling noise subsided. When closed, it came back...loud!
Once I sealed the canopy up front, the noise went away and the vent no
longer had any effect (other than the minimal noise from the incoming
air). The only thing I could come up with to explain this is the vent
was having some effect on the pressure differential between inside and
outside of the cockpit. Although I could be wrong on that. All I know
is sealing the canopy fixed the problem.


Dave

[[email protected]]

On Feb 20, 5:17*am, toad > wrote:
> I have a Grob 102 and it's making a very loud noise when flying fast
> with the nose vent closed down. *The noise comes from the nose area
> and goes away when I open the vent.
>
> I would like to be able to close the vent sometimes, because it gets
> cold :-)
>
> Any ideas what might be happening ? * It didn't always do this.
>
> Todd Smith
> 3S

Todd,

Put a bunch of drinking straws 3" to 4" in length fill the hole in
the vent from the rear.

That solved the problem for me in a ventus b

Richard
www.craggyaero.com

[TonyV[_2_]]

wrote:
> Put a bunch of drinking straws 3" to 4" in length fill the hole in
> the vent from the rear.

Yes, but be sure to pack them tight. don't ask me how I know :-).

Tony V.

[[email protected]]

The only thing I could come up with to explain this is the vent
> was having some effect on the pressure differential between inside and
> outside of the cockpit. Although I could be wrong on that. All I know
> is sealing the canopy fixed the problem.

Sounds like your letting more air in than your allowing to exit. Many
ships have this problem and need a bigger air exit hole in the rear
which should be 1.5 X the entry vent size. One way to check this
situation is with your altimeter NOT hooked to the static system, the
altimeter reading will change slightly as the vent is opened and
closed.
I have been able to find the bad area on a noisy canopy by pulling
down on the frame in several locations while in flight. When back on
the ground check all around the canopy with a feeler guage (strip of
paper works) the feeler guage will move freely in the bad area.
Hope this helps,
JJ