 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
scott-p(at)texas.net
Guest
|
 Posted: Mon Jul 03, 2006 6:59 pm Post subject: Yak 55M Air Start |
 |
|
Hi All,
Have an interesting and troublesome problem. For the last several weeks I have had trouble with the starting the Yak. The scenario is always like this: go out, check the air (650-750 psi), turn the prop through (15 blades), prime, pull the prop through (15 blades), get in, prime, start without any trouble. Go fly acro, mostly working on Advanced-level figures, rollers, inverted spins, half-snaps, with the occaisional run through an Intermediate Known or Free, land, taxi to the pump, fill gas, check the air (again 650-750 psi), get in, prime, hit the starter and nothing happens. I mean NOTHING, no hiss of air, no prop moving, and certainly no start. Rarely I can get the prop to just barely move (less than 1/3 blade), but otherwise nothing. Pulling the prop through in this condition demonstrates that it isn't hydro-locked.
My troubleshooting has run like this: 1) There is air in the system. 2) The prop is not hydro-locked. 3) The primer works. 4) The air start valve is clean and in good condition (took it out, cleaned and inspected it last week...).
Now I have run out of ideas. Could the air distributor be at fault? If so how, and how do I check it, and how do I sort it out. Ideas? Voodoo spells? Secret Russian code words? I'm up for anything that will work here...
Thanks,
Scott
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
 |
cjpilot710(at)aol.com
Guest
|
| Posted: Mon Jul 03, 2006 8:13 pm Post subject: Yak 55M Air Start |
|
|
In a message dated 7/3/2006 11:00:43 PM Eastern Daylight Time, scott-p(at)texas.net writes:
I am not an expert on the 55M but it sounds like to me that your air solenoid might be bad or very weak. It may operate OK when cold but not so after exposed to heat. The solenoid may be just weak enough to work OK cool but not be able to open the valve when it has been heated up and the valve expanse.
Jim "Pappy" Goolsby
| Quote: | Hi All,
Have an interesting and troublesome problem. For the last several weeks I have had trouble with the starting the Yak. The scenario is always like this: go out, check the air (650-750 psi), turn the prop through (15 blades), prime, pull the prop through (15 blades), get in, prime, start without any trouble. Go fly acro, mostly working on Advanced-level figures, rollers, inverted spins, half-snaps, with the occaisional run through an Intermediate Known or Free, land, taxi to the pump, fill gas, check the air (again 650-750 psi), get in, prime, hit the starter and nothing happens. I mean NOTHING, no hiss of air, no prop moving, and certainly no start. Rarely I can get the prop to just barely move (less than 1/3 blade), but otherwise nothing. Pulling the prop through in this condition demonstrates that it isn't hydro-locked.
My troubleshooting has run like this: 1) There is air in the system. 2) The prop is not hydro-locked. 3) The primer works. 4) The air start valve is clean and in good condition (took it out, cleaned and inspected it last week...).
Now I have run out of ideas. Could the air distributor be at fault? If so how, and how do I check it, and how do I sort it out. Ideas? Voodoo spells? Secret Russian code words? I'm up for anything that will work here...
Thanks,
|
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
|
scott-p(at)texas.net
Guest
|
| Posted: Tue Jul 04, 2006 5:17 am Post subject: Yak 55M Air Start |
|
|
Hi Pappy,
Unfortunately, there is no solenoid. The valve is direct actuated, as the one in the Sukhois (in fact it's the same valve...).
Scott
[quote] ---
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
|
rvfltd(at)televar.com
Guest
|
| Posted: Tue Jul 04, 2006 8:16 am Post subject: Yak 55M Air Start |
|
|
Scott,
Have you done this test yet? Next time the problem occurs:
Disconnect the hose which runs FROM the start solenoid TO the start spider on the engine, then hit the button and confirm that the start solenoid is functioning and you DO have air at the start spider. If you do have air at the start spider then timing in the start spider has somehow slipped or changed enough to not allow the air to pass and for the engine to start, if you don't have air at the start spider you most likely have an intermittent start solenoid, which is not all that uncommon. To prove this check to make sure you are in fact delivering air pressure TO the start solenoid. My guess it that you will find that your start solenoid is intermittent.
If the problem turns out to be timing I am sure that Dennis can help, if the problem is in the start solenoid I have them for the CJ6 and I do think they just might be the same.
Hope this helps.
Always Yakin,
Doug Sapp [quote] --
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
|
mark.bitterlich(at)navy.m
Guest
|
| Posted: Wed Jul 05, 2006 3:23 am Post subject: Yak 55M Air Start |
|
|
Doug, I do not believe that the YAK-55 uses an electrically actuated air start solenoid, such as the 50 and 52 does. Instead I believe it uses the same manually activated valve as do the Sukhoi's.
If this is indeed the case, Scott... your most likely cause is corrosion in the air start valve itself OR...and this is a real sneaky problem..... someone in the past has replaced the rubber pad in the air start valve with the wrong one! This problem will drive you NUTS and you have all the symtoms.
You really do not have to remove the whole thing to work on it.... although I have never worked on a YAK-55, so I am unsure of the mounting arrangement. If you can get to the back of the thing easily, you can just pull it apart from the rear and leave the main assy. in place. When you take the rear big nut off, you may have to reach into the hole with a tool to get the shuttle to slide out if there is corrosion. Anyway, pulling it that way allows you from having to remove the electrical contacts that activate your voltage booster assy. for the MAGS, which some people refer to as the shower of sparks... which it really isn't. If that is impossible, then simply pull the whole thing out of there and take it apart. Inside you will find a spring... which often breaks from corrosion..... a shuttle valve with ridges on the outside.... clean it and the barrel of the valve carefully.... and on the end of the shuttle you will find that one end is open... hollow, and the other end has a little metal tit sticking out right from the middle. The little metal tit should have a black rubber seal surrounding it. The seal should look like a hard rubber gasket.. not an "O" ring, but instead almost like a thick hard rubber washer. This piece MUST ... and I repeat MUST have a small hole right in the middle of it that allows the metal tit from the shuttle valve itself to stick through it. If you happen to have a hard rubber gasket... round but with no hole in the middle of it... you have found your problem. If it does have a hole in the middle of it... then check for broken weak spring, and/or corrosion in the valve body itself preventing the shuttle from moving freely.
Here is how this happens... There is an over-pressure relief valve on most Russian aircraft that works ALMOST exactly like the start valve on your YAK-55. The rubber bushing/seal in it is perfectly round with no hole in the middle and is on the end of a shuttle valve ALMOST but not exactly identical again to the start valve. There is a kit to replace the bushing on the over-pressure relief valve. Many people have mistakenly made the assumption that this same bushing/rubber seal can also replace the one in the start valve. Actually it can.... as long as you carefully put a hole directly in the middle of it so that the metal tit that sticks out from the end of the start valve shuttle can poke through.... otherwise you have symtoms very close to what you are experiencing. It's a long shot... but someone might have done this to your airplane.
I have never seen a spider distributor that worked cold, but won't work hot. Those things are devices made by the devil though.... so I guess it is possible! WARNING! Do NOT pull that thing out of your aircraft until you are DARN DARN SURE that it is bad. Expect a few DAYS worth of effort to get it back in and working again.
A quick check here would be to simply take the air line off right at the start lever that leads to the engine. Push the start lever. Got plenty of air? No? That pretty much answers your question.
Best of Luck,
Mark Bitterlich
[quote] --
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
|
scott-p(at)texas.net
Guest
|
| Posted: Wed Jul 05, 2006 4:40 am Post subject: Yak 55M Air Start |
|
|
Hi Mark,
Your description of the valve is perfect. That is indeed how the air start on the -55M works. The valve is located on the far lower left of the panel, with a bulkhead below it, and is accessible only through the hole where the floating panel attaches (and around a slightly more than 90 degree corner...), thus must be removed to service in any meaningful way (unless one is a three foot tall, double-jointed elf with extremely long fingers...<VBG>).
I've had this valve out, and apart and can report that the rubbers are correct, with the appropriate holes, and in good condition. As is in the inside of the valve and the spring--very minimal corrosion which came off with just a little bit of cleaning.I am guessing at this point that the problem is hose/line related. The valve connects to a hard line which runs forward to the firewall, and thence to a Russian hose from the firewall to the inlet on the distributor. I will try removing the connector at the firewall and see if I get air there next time I have the problem (I tried to recreate the problem yesterday, but of course, the engine starts perfectly now...). I am hoping at this point that the problem is hose related. I REALLY don't want to futz with the distributor...
Thanks,
Scott
[quote] ---
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
|
rkent(at)wlacrussianeng.c
Guest
|
|
| Back to top |
|
|
mark.bitterlich(at)navy.m
Guest
|
| Posted: Wed Jul 05, 2006 6:13 am Post subject: Yak 55M Air Start |
|
|
Scott, make sure you download Rob Kent's pictures, they make great reference material! Yes, I agree... it is much more likely that some foreign object is floating around in the hose, or you have a hose with a "flap" at one end someplace. Taking the lines off and checking for flow will indeed narrow this down.
Best of luck,
Mark
[quote] --
| | - 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:
http://www.matronics.com/Navigator?Yak-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
