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HawkerPilot2015
Joined: 10 Jan 2006
Posts: 503
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 Posted: Sat Jul 21, 2007 7:35 pm Post subject: Air system problem.... |
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I will try to be as specific as I can about the issue....
Yak-50....
A bit of history is in order. The primary side bottle failed and needed to be replaced. No Yak-50 size bottle (6 liters) on the planet so I opted for a -52 bottle (11 liters). Got said bottle and knew it was NOT going where the smaller bottle came from. SO......built up some structure forward of the batteries and mounted the bottle there. (Moved the batt's up too and built a cargo box where the batts were)
Anyway...We did a retraction test at annual and did not notice any leaks at the gear. No leaks elsewhere that we could find. So, a few weeks pass and the airplane develops an air problem. Here is what I am doing and what the airplane IS NOT doing.
Normal ops.
Prior to start:
* 50 atms PRIOR to opening the valve.
* Open the valve, the pressure drops about 30+ atms to around 20.
* Starts...slower due to lower pressure...but starts.
* Long Taxi.....pressure comes up slowly to about 30-35.
* Take off...gear nearly kills my pressure coming up. Drops back to about 20. (Today, I had to put some negative on the gear to get it to lock up)
*Fly around a bit and the thing makes air like its on crack. Great pressure and pop off valve works good.
* Gear down...and there goes about 30+ atms! (I now put the gear down a little sooner to make sure there is plenty of press for brakes and in the event I need to bring gear up for GA.)
Land.....Run the airplane up and let pressure build back up to about 50 atms, shut off the main valve (which reveals a climb in guage pressure), and kill the engine. Chocks in...off to the house.
A week or so later and I have about .5 less atms. Not a huge loss. But go to fly, and it is back to what I listed above.
Here are a few observations:
1.) No leaking sound near the rams.
2.) No hissing from the gear handle. (A fine mist of tool oil comes out from servicing)
3.) Holds air well after a few days of sitting. Very little loss.
4.) Gear down..takes some time making air. (low RPM?)
5.) Gear up, makes silly amounts of air. (high RPM?)
Now today, I had a slow left main. Positive and Negative g's were needed to get up/down lock. I am not sure if that is "lower" pressure issue OR a leak on that side.
Is that very clear?
Thanks in advance! I would get a simpler airplane but I am addicted to this problem child. I just cannot seem to kick the habit.
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viperdoc(at)mindspring.co
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| Posted: Sun Jul 22, 2007 5:42 am Post subject: Air system problem.... |
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Tim,
How old are your flexible brake lines. Both from the fitting to the brakes
that disappears into to the wing to the right and left of the gear well. It
then attaches to a flexible line that runs along the spar through the side
of the fuselage. Ultimately connecting to the proportionating valve behind
the fuel tanks in that hell hole in front of your rudder bar. I found that I
had a push rod rubbing on one of the aluminum airlines there.
Just one experience I have had with the air system on the 50.
Doc
--
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dsavarese(at)elmore.rr.co
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| Posted: Sun Jul 22, 2007 6:11 am Post subject: Air system problem.... |
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Doc's push rod rubbing could easily be heard when moving the stick left to
right. Quite apparent. Remove the lower wing root panel and look at the
aileron push rod going through the right side of the fuselage and you will
see where the potential problem is. The pneumatic lines are VERY close to
the aileron push rod.
As for Tim's problem, if you've never pulled the landing gear actuators, you
really need to do that and have them overhauled. With the pressure dropping
30+ ATM's when you cycle the gear, most likely the seals inside the actuator
have gone T.U.
If you want to do a bit of isolating the problem, put the airplane on jacks
and pull the flexible lines off one of the actuators and plug the flexible
hose ends. Bring the pressure in the system back to 50 ATM's. Open the
main air valve and see if the pressure drop remains the same. If it still
drops 30+ ATM's then do the same thing to the other side.
Dennis
---
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brian-1927(at)lloyd.com
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| Posted: Sun Jul 22, 2007 9:52 am Post subject: Air system problem.... |
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On Jul 21, 2007, at 11:35 PM, Tim Gagnon wrote:
| Quote: | * Take off...gear nearly kills my pressure coming up. Drops back to
about 20. (Today, I had to put some negative on the gear to get it
to lock up)
|
Just remember PV=nRT. Since the volume in the gear rams remains the
same but you get a much bigger pressure change, the overall volume of
the system may have changed. Look for a restriction between the
system and the air storage reducing the overall system volume. In the
CJ6A you can accomplish this set of symptoms very easily -- by
leaving the main air valve turned off. The result will be huge
pressure change with gear retraction followed by unusually rapid
pressure recovery.
--
Brian Lloyd 3191 Western Drive
brian HYPHEN 1927 AT lloyd DOT com Cameron Park, CA 95682
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry
PGP key ID: 12095C52A32A1B6C
PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
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yakplt(at)yahoo.com
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| Posted: Sun Jul 22, 2007 5:46 pm Post subject: Air system problem.... |
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Tim,
I hate to say it, but I am suspecting leakage through the gear actuators. You need to take the hose off the UP side of the actuator (the rear of it) on both gear when the thing is on the deck and has been sitting for awhile. Pull the hose off both the left and right side actuators at the rear.
Now get two buddies and put one in each wheel well and have them put their finger on the outlet of the actuator. Not the hose... the fitting on the actuator itself.
Now open the valve in the cockpit. My guess is that you are going to get a significant amount of air out of the actuators past the guys fingers in either the left or right side, then it will stop. Again, my guess is that the seal is leaking to begin with and then sealing.
It is common to lose air out of the gear system as it sits there over time. Then when you open the valve your air system drops about 10 atmos. More than that, and something is bad wrong.
So ok, you tried that and you got NOTHING out of either actuator? Ok, then the next thing to take a close peak at is your starter select valve. Disconnect the line coming out of the starter valve going to the air distributor, and repeat same test as above. See if it is by-passing at that valve and then stopping.
It pretty much has to be one or the other... I think. Hmm. Well... just to be on the safe side add one more test. Open snot valve. Let all air out. Now open valve in cockpit and leave it open. Go back to snot valve and open it. If any air comes out you have a bad check valve.
I can't think of anything else.
Mark Bitterlich
Tim Gagnon <NiftyYak50(at)fuse.net> wrote:
[quote]--> Yak-List message posted by: "Tim Gagnon"
I will try to be as specific as I can about the issue....
Yak-50....
A bit of history is in order. The primary side bottle failed and needed to be replaced. No Yak-50 size bottle (6 liters) on the planet so I opted for a -52 bottle (11 liters). Got said bottle and knew it was NOT going where the smaller bottle came from. SO......built up some structure forward of the batteries and mounted the bottle there. (Moved the batt's up too and built a cargo box where the batts were)
Anyway...We did a retraction test at annual and did not notice any leaks at the gear. No leaks elsewhere that we could find. So, a few weeks pass and the airplane develops an air problem. Here is what I am doing and what the airplane IS NOT doing.
Normal ops.
Prior to start:
* 50 atms PRIOR to opening the valve.
* Open the valve, the pressure drops about 30+ atms to around 20.
* Starts...slower due to lower pressure...but starts.
* Long Taxi.....pressure comes up slowly to about 30-35.
* Take off...gear nearly kills my pressure coming up. Drops back to about 20. (Today, I had to put some negative on the gear to get it to lock up)
*Fly around a bit and the thing makes air like its on crack. Great pressure and pop off valve works good.
* Gear down...and there goes about 30+ atms! (I now put the gear down a little sooner to make sure there is plenty of press for brakes and in the event I need to bring gear up for GA.)
Land.....Run the airplane up and let pressure build back up to about 50 atms, shut off the main valve (which reveals a climb in guage pressure), and kill the engine. Chocks in...off to the house.
A week or so later and I have about .5 less atms. Not a huge loss. But go to fly, and it is back to what I listed above.
Here are a few observations:
1.) No leaking sound near the rams.
2.) No hissing from the gear handle. (A fine mist of tool oil comes out from servicing)
3.) Holds air well after a few days of sitting. Very little loss.
4.) Gear down..takes some time making air. (low RPM?)
5.) Gear up, makes silly amounts of air. (high RPM?)
Now today, I had a slow left main. Positive and Negative g's were needed to get up/down lock. I am not sure if that is "lower" pressure issue OR a leak on that side.
Is that very clear?
Thanks in advance! I would get a simpler airplane but I am addicted to this problem child. I just cannot seem to kick the habit.
Read this topic online [quote][b]
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yakplt(at)yahoo.com
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| Posted: Sun Jul 22, 2007 5:50 pm Post subject: Air system problem.... |
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Who the heck is Brian Lloyd?
Hey my friend, nice to hear from you.
Hey Tim. I forgot about the brakes. Oops. Easy mistake to make, mine are hydraulic.
Mark Bitterlich
Brian Lloyd <brian-1927(at)lloyd.com> wrote:
[quote]--> Yak-List message posted by: Brian Lloyd
On Jul 21, 2007, at 11:35 PM, Tim Gagnon wrote:
| Quote: | * Take off...gear nearly kills my pressure coming up. Drops back to
about 20. (Today, I had to put some negative on the gear to get it
to lock up)
|
Just remember PV=nRT. Since the volume in the gear rams remains the
same but you get a much bigger pressure change, the overall volume of
the system may have changed. Look for a [quote][b]
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HawkerPilot2015
Joined: 10 Jan 2006
Posts: 503
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| Posted: Tue Jul 24, 2007 6:39 pm Post subject: Re: Air system problem.... |
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Brian, nice to see you again and thanks for the advice.
I ran the test Mark recommended today and if I simply had better hearing, I could have avoided all of them and found the problem. I did figure out that I have a good check valve and started valve though.
Right main is leaking from the front cap where the rod end goes. They come out tomorrow and will be shipped for overhaul.
Thanks for the input fellas!
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mark.bitterlich(at)navy.m
Guest
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| Posted: Thu Jul 26, 2007 12:14 pm Post subject: Air system problem.... |
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Good find. If you want, you can rebuild them yourself, it is not too
hard. Carl Hays has kits I believe.
Mark Bitterlich
--
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viperdoc(at)mindspring.co
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| Posted: Thu Jul 26, 2007 1:00 pm Post subject: Air system problem.... |
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He does. I have a set for my 50 sitting on the shelf currently. I got them
from Carl and Jill.
Doc
--
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