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Stressmerchant
Joined: 28 Oct 2014
Posts: 22
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 Posted: Sat Jul 06, 2019 10:25 pm Post subject: Pneumatic system - lubrication |
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How much maintenance is generally required on the Yak-52 pneumatic system, and does the lubrication level play a role?
The background to this is that I shipped my Yak from South Africa to Australia. I'd run the Yak in South Africa for about 10 years, with the annual maintenance being done by an expatriate Russian. During that time we never had a single hassle with the pneumatic system. The Russian technician did tell me that they lubricated the various undercarriage actuators in accordance with the original manuals, which called for a fairly large amount of lubricant. I recall that after annual services, operation of the undercarriage usually resulted in a fine mist of oil in the cockpit which looked a bit like smoke.
Now the aircraft is in Australia. At reassembly, the Licensed Aircraft Maintenance Engineer (LAME) insisted that the pneumatic system be completely overhauled - including all seals and o-rings within the system. Since the aircraft had been in a non-flying condition for a fair amount of time, I could understand that some corrosion could have developed. (FWIW the aircraft was held up in South Africa for 18 months due to customs issues, and it then took the local LAME almost 3 years to reassemble).
At the first annual service after returning to flight, the LAME (different one) reported that the pneumatic system was in very poor condition, and has replaced all the seals in the actuators. I am rather confused by this, since a) it gave years of faultless service in South Africa, and b) it was completely overhauled a year ago.
My suspicion is that the system was not properly lubricated at the reassembly overhaul. What is the experience of the List members regarding the reliability of the pneumatic system? Is it common to have to redo the seals annually, or is there something in the system that could be causing the problem?
Thanks
Mike
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Harv
Joined: 01 Jul 2010
Posts: 172
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| Posted: Sun Jul 07, 2019 12:22 am Post subject: Re: Pneumatic system - lubrication |
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Sounds to me like your new LAME in Australia may not be the right guy for you. Does he have much experience with these types of AC?
I've had similar problems with engineers and like you use a Russian guy who maintains the CJ in accordance with the yak52 procedure for lubricating the pneumatic system. When I first moved to him I was skeptical about the amount of lubrication that was going into the system especially after experiencing the misting in the cockpit after annuals when doing the first few gear retractions in flight.
A few things I've noted since, the main and emerg air bottles don't seem to get any surface corrosion in them as noted by the borroscope inspections (where as they did before with the old LAME who didn't believe in adding lubricant to the system) and the system has been faultless.
I've done a few mods to try and improve the systems reliability such as fitting the stainless balls and springs (from Doug Sapp) to all the check valves on the firewall and always keep a close eye on the dessicant condition in the moisture filter. As we know water in the system is the factor that will determine if it's last or not.
Did your current LAME explain why he believes the system is shot?
Just my 2p worth, hope you get a resolution
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