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dsavarese0812(at)bellsout
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 Posted: Fri Oct 05, 2012 5:42 am Post subject: Pneumatic Nonsense |
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Rico,
What work, if any, did you do on the gear actuators? You said you
overhauled the shuttle valves. But did you overhaul the actuators?
Put the rear gear selector in the DOWN position and then put the front
gear selector in the NEUTRAL position, do you get the same air leak from
the rear gear selector?
Go to each gear actuator (one at a time) and remove the B nut on the 90
degree elbow on the UP side of the actuator. Turn the main air on. Now
with the B nut removed, put your finger over the opening on the 90
degree elbow. Putting a little bit of saliva on your finger helps you
'feel' the leak, if there is one. If there is air coming out of the 90
degree fitting, the seals in the actuator need to be replaced.
Dennis
A. Dennis Savarese
334-285-6263
334-546-8182 (mobile)
www.yak-52.com
Skype - Yakguy1
On 10/5/2012 8:22 AM, Rico Jaeger wrote:
| Quote: | OK, guys...put your thinking caps (helmets) on:
A couple months ago I had a series of air system problems
introduced after opening the emergency air. Upon re-setting the system
back to primary, the emergency relief valve - located on the floor of
the front cockpit - hissed loudly every time I opened the system. I
was told to go through my gear shuttle valves - which I did. When
I completed re-installation of all 3 valves last evening, I refilled
the primary system (emergency was still 100%) and opened the main air
shut-off to find the emergency relief valve now completely silent, but
a very audible hiss emanating from (what appears to be) the front gear
selector. As predictable, the hiss fades to nil after shutting off the
air. Unpredictably, it also sporadically re-appears w/o turning the
air on and crescendos to higher volume than ever - albeit for short
periods - maybe 1 minute. But it REALLY hisses, as in "RUN! THIS
BABY'S GONNA BLOW!" The emergency side of the air guage stays put. But
you can watch the primary side bleed off. When reassembling the
valves, I did not pre-position the rubber balls - as I assumed, with
the emergency system closed, opening the primary system would blow the
ball to the correct side of the valve. I'm not certain now if a
valve(s) is leaking, but as I said, the emergency relief valve is
silent. Based on the idea that I possibly opened the primary shut off
too gently to position the ball(s), I refilled the system and opened
the shut off aggressively to try to seat them. While the level of air
escaping did appear to vary - this seemed to have no significant
effect. Using a listening device, I am not able to detect air escaping
/ passing through any of the gear areas. But - amplified, the gear
selector sounds like a gale. Flaps and brakes seem to function
normally. I did not cycle the gear or attempt a start. Thank you for
chewing on this one. The "coolest plane" at my small airport has been
a lawn ornament for far too long now...
--
Rico Jaeger
Choir / East High
General Music / Mann
*
*
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mark.bitterlich(at)navy.m
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| Posted: Fri Oct 05, 2012 6:24 am Post subject: Pneumatic Nonsense |
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Not that my advice is needed here, Dennis already said anything I might
have. I will add my vote to his conclusion though if I may. I have had
the exact same thing happen with the exact same result in my YAK-50.
The normal gear extension bleeds air into the gear actuators through a
small orifice that is drilled in a cone type sleeve that is inserted
into the hose line coupling to the actuator. This controls the speed of
gear movement as high pressure air is applied through the gear actuator
lever.
When the emergency valve is opened, it comes in via a different hose,
with no air flow regulation, which is intentional. Full high pressure
(about 730 +/- PSI or so) is applied as in RIGHT NOW to the actuators.
If the seals on those actuators are anything less than perfect ... they
can let go.
Once that happens, air bleeds through the actuator as soon as you apply
pressure to it. That bleed air comes right back to the gear actuator
lever and bleeds out.
I had no one to ask when this happened to me, and it took a lot of head
scratching to figure it out.
Good luck.
Mark
--
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rijaeger(at)wausau.k12.wi
Guest
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| Posted: Fri Oct 05, 2012 8:30 am Post subject: Pneumatic Nonsense |
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Gentlemen,
First of all - it's very reassuring to receive coaching from 2 of the "heavy-hitters" in the Yak World. Thank you for the time and consideration - as well as the education.
Secondly, as I mentioned before, there is no detectable / audible leakage at any of the gear - even w/ electronic listening enhancement. Wouldn't a leaking actuator be pulling an audible draw through the line? (Not arguing at all here - just attempting to establish dilema parameters) I understand that just because the hissing emanates from the selector that the selector is not necessarily at fault. The emergency system was opened when the gear was already extended (it hadn't been retracted except in prior retraction tests) and the Yak was on landing roll out / runway overrun - if that affects anything...?
I will follow Dennis' elimination / confirmation procedure and see where that leads this weekend. But meanwhile, if this is ringing a bell w/ anyone else w/ similar experiences, I'm always happy to hear from you.
Thanks much!
Rico
On Fri, Oct 5, 2012 at 9:21 AM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:
[quote]--> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
Not that my advice is needed here, Dennis already said anything I might
have. I will add my vote to his conclusion though if I may. I have had
the exact same thing happen with the exact same result in my YAK-50.
The normal gear extension bleeds air into the gear actuators through a
small orifice that is drilled in a cone type sleeve that is inserted
into the hose line coupling to the actuator. This controls the speed of
gear movement as high pressure air is applied through the gear actuator
lever.
When the emergency valve is opened, it comes in via a different hose,
with no air flow regulation, which is intentional. Full high pressure
(about 730 +/- PSI or so) is applied as in RIGHT NOW to the actuators.
If the seals on those actuators are anything less than perfect ... they
can let go.
Once that happens, air bleeds through the actuator as soon as you apply
pressure to it. That bleed air comes right back to the gear actuator
lever and bleeds out.
I had no one to ask when this happened to me, and it took a lot of head
scratching to figure it out.
Good luck.
Mark
--
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mark.bitterlich(at)navy.m
Guest
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| Posted: Fri Oct 05, 2012 9:14 am Post subject: Pneumatic Nonsense |
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Reply to Rico:
| Quote: | Secondly, as I mentioned before, there is no detectable / audible
leakage at any of the gear - even w/ electronic listening enhancement.
|
Wouldn't a leaking actuator be pulling an audible draw through the line?
No idea if it would be detected or not. Leak detectors of that type
usually are picking up ultrasonic noise from the leak, not from internal
flow. Otherwise they would be kind of useless, because you'd just hear
flow as well as leaks when using them.
| Quote: | (Not arguing at all here - just attempting to establish dilema
parameters) I understand that just because the hissing emanates from the
|
selector that the selector is not necessarily at fault.
If it hisses at the selector the selector is not necessarily the fault.
Correct. In fact it would be highly unusual for the selector to be at
fault. However, I would not make any bets either way, because it is too
easy to find out for sure.
| Quote: | The emergency system was opened when the gear was already extended (it
hadn't been retracted except in prior retraction tests) and the Yak was
|
on landing roll out / runway overrun - if that affects anything...?
Ok. That does not change the fact that when you opened the emergency
valve, unless you did it very very carefully and very very slowly, you
as a result put an instantaneous air load onto the seals. If you have
ever injected any air tool in those cylinders like has been suggested by
some in the past, that can also influence this kind of thing.
To be perfectly candid, I am not saying that opening the emergency air
valve caused your seals to blow. I am saying that opening the emergency
air valve on an already unpressurized system CAN cause the seals to
fail. In this specific case, you opened the emergency air valve and
subsequently heard air hissing. Over time and with other fixes, you now
are hearing air coming out the landing gear selector valve. Air hissing
out of the landing gear selector valve is usually caused by a gear
actuators with an internal leak allowing air to flow completely through
the actuator, back through the other hose to the internal vent in the
landing gear selector valve. 2+2= ???
| Quote: | I will follow Dennis' elimination / confirmation procedure and see
where that leads this weekend. But meanwhile, if this is ringing a bell
|
w/ anyone else w/ similar experiences, I'm always happy to hear from
you.
Until you run specific tests, anything anyone writes is a guess. What
has been written so far is based on similar experience that rang a bell.
All it takes is a wrench and taking off a few hoses (one at a time) to
determine if the cause is leaking internal seals in the actuators or
not.
Good Luck.
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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rijaeger(at)wausau.k12.wi
Guest
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| Posted: Fri Oct 05, 2012 10:49 am Post subject: Pneumatic Nonsense |
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|
Thanks, Mark. I will see what I can find...
On Fri, Oct 5, 2012 at 12:12 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:
| Quote: | --> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
Reply to Rico:
| Quote: | Secondly, as I mentioned before, there is no detectable / audible
leakage at any of the gear - even w/ electronic listening enhancement.
|
Wouldn't a leaking actuator be pulling an audible draw through the line?
No idea if it would be detected or not. Leak detectors of that type
usually are picking up ultrasonic noise from the leak, not from internal
flow. Otherwise they would be kind of useless, because you'd just hear
flow as well as leaks when using them.
| Quote: | (Not arguing at all here - just attempting to establish dilema
parameters) I understand that just because the hissing emanates from the
|
selector that the selector is not necessarily at fault.
If it hisses at the selector the selector is not necessarily the fault.
Correct. In fact it would be highly unusual for the selector to be at
fault. However, I would not make any bets either way, because it is too
easy to find out for sure.
| Quote: | The emergency system was opened when the gear was already extended (it
hadn't been retracted except in prior retraction tests) and the Yak was
|
on landing roll out / runway overrun - if that affects anything...?
Ok. That does not change the fact that when you opened the emergency
valve, unless you did it very very carefully and very very slowly, you
as a result put an instantaneous air load onto the seals. If you have
ever injected any air tool in those cylinders like has been suggested by
some in the past, that can also influence this kind of thing.
To be perfectly candid, I am not saying that opening the emergency air
valve caused your seals to blow. I am saying that opening the emergency
air valve on an already unpressurized system CAN cause the seals to
fail. In this specific case, you opened the emergency air valve and
subsequently heard air hissing. Over time and with other fixes, you now
are hearing air coming out the landing gear selector valve. Air hissing
out of the landing gear selector valve is usually caused by a gear
actuators with an internal leak allowing air to flow completely through
the actuator, back through the other hose to the internal vent in the
landing gear selector valve. 2+2= ???
| Quote: | I will follow Dennis' elimination / confirmation procedure and see
where that leads this weekend. But meanwhile, if this is ringing a bell
|
w/ anyone else w/ similar experiences, I'm always happy to hear from
you.
Until you run specific tests, anything anyone writes is a guess. What
has been written so far is based on similar experience that rang a bell.
All it takes is a wrench and taking off a few hoses (one at a time) to
determine if the cause is leaking internal seals in the actuators or
not.
Good Luck.
List Un/Subscription,
www.matronics.com/Navigator?Yak-List" target="_blank">http://www.matronics.com/Navigator?Yak-List
ronics.com/" target="_blank">http://forums.matronics.com
Matt Dralle, List Admin.
=====
|
--
Rico Jaeger
Choir / East High
General Music / Mann
[quote][b]
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