29 Mar 2024, 09:33 [ UTC - 5; DST ]
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 19:06 |
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Joined: 10/05/09 Posts: 286 Post Likes: +130 Location: Portland, Oregon
Aircraft: MU-2F
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Username Protected wrote: Great write up. What type of hydraulic fluid would an MU2 use? The only thing that uses hydraulic fluid (5606) on the MU2 is the brakes. Landing gear and flaps all use electric motors and jackscrews. Flight controls are all mechanical as well. Pretty simple plane really, but stuff does have to be rigged properly and components inspected for wear. Lubrication of stuff is a big part of 100-hour inspections.
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 19:22 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23615 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: I know electric actuators weren't really an option when these things were designed Oddly enough, the 500, 501, and 550 models used electric flaps (with two coupled motors). The later S550, 560 models use hydraulic flaps. There are pluses and minuses to each kind of system. Hydraulics tend to be lighter and more reliable overall, but messier to fix. Electric motors fail more often, require gear trains, and can melt, but can't leak fluid. The MU2 was all electric except for brakes (which you don't use). I've seen numerous issues with motors, gear trains, relays that have affected those systems. Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 19:30 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23615 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: Ah yes. The $5000 pinhole! :bugeye: Probably more than that given all costs it caused. Quote: Is there a recommended aluminum line replacement timeframe? No, I don't think so. They last a very long time outside of external abrasion or corrosion. Quote: Are there other lines you may replace now just to avoid a similar cost and inconvenience? Not really. It is messy to replace them, too. The best treatment is a really serious visual inspection which might have found this before it leaked. Then you can replace any suspect lines at that time. This does not seem to be a common problem in the fleet, I seem to have just been unlucky. Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 20:05 |
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Joined: 11/08/12 Posts: 6232 Post Likes: +3735 Location: San Carlos, CA - KHWD
Aircraft: Piaggio Avanti
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Username Protected wrote: They last a very long time outside of external abrasion or corrosion. Since you mentioned where it passed through a grommet, I'm guessing yours was abrasion?
_________________ -Jon C.
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 20:25 |
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Joined: 04/06/11 Posts: 7895 Post Likes: +3908
Aircraft: Warbirds
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Username Protected wrote: They last a very long time outside of external abrasion or corrosion. Since you mentioned where it passed through a grommet, I'm guessing yours was abrasion? Photo didn't look shiny and chafed. Just a hole which suggests corrosion. A molecule of something foreign in the metal at a spot where moisture could be held against tube can start the localized process. Acid from the skin on the alum line, a dab of some chemical or talc from the factory on the grommet, lots of things can start this Many years ago it was a medium pressure rubber hose with cloth in the rubber that sat against an alum -4 line in the L/H Wheel well of the Aerostar 600 that did a similar failure. Rubber hose outer cloth layer corroded the alum tube on the back side. It wasn't seen till it was an issue. That started out oozing and stick due to 5056 fluid so was caught before a massive leak.
_________________ Be careful what you ask for, your mechanic wants to sleep at night.
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 20:27 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23615 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: Since you mentioned where it passed through a grommet, I'm guessing yours was abrasion? No, I don't think so. It looks like pit corrosion. If it had been abrasion, I'd expect to see clear lines of motion, but I just see a corroded pit. Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 22:31 |
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Joined: 11/25/19 Posts: 175 Post Likes: +85
Aircraft: Aerostar 601P, AS350
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This is exactly why I always bring a can of flex seal with me.
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 22:40 |
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Joined: 10/07/18 Posts: 2649 Post Likes: +1764 Location: Columbus, Ohio
Aircraft: Baron 58, Lear 35
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Username Protected wrote: The best treatment is a really serious visual inspection which might have found this before it leaked.
Mike C.
IMO, it’s not very practical to remove every grommet and Adel clamps to inspect hydraulic/pneumatic lines for corrosion. That would literally be hundreds of clamps per airframe on the equipment I maintain. Inspection when removed FOM is about the most realistic course.
Last edited on 13 Jan 2023, 22:42, edited 1 time in total.
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Post subject: Re: My Citation V AOG event Posted: 13 Jan 2023, 22:52 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23615 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: Mike, I wish you bought a 525 CJ so I could get your extensive follow up on maintenance issues. I believe the 525 hydraulic system is basically the same. Gear, speedbrakes, and flaps are hydraulic, as well as thrust attenuators on the early models. They use MIL-PRF-83282 fluid, a less nasty fluid than Skydrol. Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: My Citation V AOG event Posted: 14 Jan 2023, 01:05 |
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Joined: 11/08/12 Posts: 6232 Post Likes: +3735 Location: San Carlos, CA - KHWD
Aircraft: Piaggio Avanti
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Username Protected wrote: This is exactly why I always bring a can of flex seal with me. For hydraulic fluids and pressures? I don’t know the product but it seems unlikely that anything sprayed on the outside of a leaking hydraulic tube could seal it realistically enough for flight.
_________________ -Jon C.
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Post subject: Re: My Citation V AOG event Posted: 14 Jan 2023, 01:31 |
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Joined: 11/25/19 Posts: 175 Post Likes: +85
Aircraft: Aerostar 601P, AS350
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Username Protected wrote: This is exactly why I always bring a can of flex seal with me. For hydraulic fluids and pressures? I don’t know the product but it seems unlikely that anything sprayed on the outside of a leaking hydraulic tube could seal it realistically enough for flight.
Haha I’m just kidding
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