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 Post subject: My Citation V AOG event
PostPosted: 13 Jan 2023, 13:27 
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Company: Ciholas, Inc
Location: KEHR
Aircraft: C560V
I've had great fortune with my MU2 and Citation with regards to mission reliability. I can recall only one time the MU2 didn't go when I wanted it to over 13 years and 1600 hours, a failed squat switch, which was fixed the next morning.

I've had my first AOG event in the Citation. My mission was to fly from KEHR (Henderson, KY home base) to KLWM (Lawrence, MA) on Sun Jan 8. The plane was full, 9 people, first time ever. This consisted of myself and 2 employees for business meetings, my sister-in-law's family of four traveling to Boston, and my copilot and his wife. We were to spend Mon in meetings and return Mon evening.

As part of taking so many people, I had removed my tools, spares, and ballast rocks from the nose just in case I needed the useful load or needed the baggage space. Turns out, I needed neither in the end. This would be the very first flight I made in the Citation without my tools and spares aboard. Warning sign number one!

When I preflighted the airplane on Sun, I noticed that my hydraulic reservoir was about 1/4" lower than I expected. Warming sign number two!

The reservoir has a linear scale that is about 5 inches long, so 1/4" isn't much change from the full mark, and it was colder than usual so I attributed this to the temperature change. I even told my copilot about the hydraulic level being a touch low but that I wasn't concerned. This is what normal looks like, it tended to run about 1/8" under "FULL" mark (level gets set every time the hydraulic system gets inspected).
Attachment:
hyd-reservoir-1.png

There is a microswitch on the plunger that trips a low fluid caution, and above the plunger is a relief valve that vents the reservoir if it is overfilled or manually to set level.

The flight to KLWM went without a hitch, got a really nice tailwind, saw 537 knots GS at once point. Whee! Had no indications or concerns during the flight.

After landing, no obvious faults were seen on the plane but I did not check the reservoir. It was dark, so I didn't see much in the tail, just disconnected the battery as usual. The plane was parked on the ramp. The various folks dispersed and did their thing. My folks to a hotel and then had meetings Mon, the copilot and wife went to visit family, my SIL family are staying (both kids are MIT students) and not returning with us.

When we got back to the plane on Mon at about 1800 ET, we found a large pool of fluid under the tail. This is what it looked like the next morning:
Attachment:
skydrol-pool-1.png

It became clear this was Skydrol, the hydraulic fluid used in my airplane. Inside the tail, there was dripping Skydrol and standing pools of it in some bays. What a mess. To those who don't know, Skydrol is nasty stuff. You don't want to touch it, and it ruins paint.

The reservoir was just under the "REFILL" line, so most of the fluid had leaked out, but it was clear the leak was still going due to the steady drip rate. I was at Falcon Air, the CAA FBO at KLWM, and their mechanic, Dylan, came out to look that night. As best as he could determine, it was coming from a 1/4 inch line where it passed through a grommet.

It was not safe to fly the plane in this condition as we'd likely be out of hydraulic fluid by the end of the trip home. The issue is not so much the loss of the systems (flaps, gear, TRs, and speedbrakes) which I can handle and was trained for, but that the engine driven hydraulic pumps could run dry and ruin them, plus when Skydrol gets overheated, it turns into an acidic fluid that can damage the rest of the hydraulic system. There was no clearly satisfactory way to patch the line, nor did Falcon Air have the means to put fluid back into the airplane.

Since I did not know how long the repair would take, my two employees got airline flights Tue morning and returned. The copilot and wife decided to stick it out with me while I got the plane fixed.

I needed to find someone who can come to the plane, diagnose the problem with certainty, clean up the mess, and fix it.

Textron factory service center was at KSWF (Stewart, NY), and their MSU (mobile service unit) was also based there. Ironically, the previous owner had all the maintenance for my plane done at KSWF from 2012 to 2000 when I bought it, so they would know the airplane. Having tried to use the MSU once before, I knew it would be expensive since they will charge drive time, about 7 hours round trip. So I sought other options first.

Falcon Air recommended JetEast out of KBED (Bedford, MA) which is only about 25 minutes away. I posted on the CJP (Citation Jet Pilots) forum and they also said JetEast and another shop at KBED. The other shop said they couldn't do it, and also recommended JetEast. Okay, JetEast. They have an extensive AOG service fleet.

https://jeteastgama.com/aog-maintenance/

I reached out to JetEast and they could send a team and insisted on sending two people. There was a lot of paperwork I had to fill out Mon evening, signing the final authorization about midnight. The costs would include travel time, lodging if needed, and each person would be $200/hour, or $400/hour for the team. Oh well, I need the plane fixed and there's not a lot of ability to shop this around.

On Tue morning, we went to a store and bought gloves, rags, and some basic tools. I didn't know when the JetEast guys would show up (they didn't tell me) so I figured I'd make some head start on things. We got to the airplane on the ramp at about 0800 ET. I started taking apart the baggage compartment walls since that greatly increases access to the hydraulic system. I had that done about 0930 ET and then the JetEast guys showed up. They started on the issue. They also thought it was this particular line that was leaking. They took out some other structure in the way to make things easier.

The reservoir had not bled down to "EMPTY" just yet, but it was close. The spring in the reservoir keeps about a 4 PSI pressure on the system, so the dripping was still going one. This means we can still find the source of the leak, which would get much harder when the reservoir goes dry.

The JetEast guys first cleaned up the major pools of fluid inside the tail. The plan was to clean up the line as best we can, then observe where the fluid first starts to appear to confirm the leak location. The fluid doesn't necessarily drip from the leak since it runs down the line. After we did this, it was 100% certain the leak was in this 1/4 inch line that was first suspected. Once that was determined, the hydraulic system was drained to stop the leak.

About this time, we got use of a heated hangar so we spent 20 minutes moving the plane from 30 degree ramp to the hangar. Kind of an expensive move at $400/hour, but the increase in productivity would make it worthwhile.

Next came the clean up. The approach is to mop up any pooling fluids, then to spray it all down with alcohol and wipe that up. In places they can't reach, they sprayed a lot of alcohol and let it drain out the same path the Skydrol was taking. They did a pretty good job of this and you really can't tell where the Skydrol was.

Next the line got removed. The line is pretty easy to remove at each end, but the clamps along its route were very difficult. They spent most of the time on that. The line runs from a tee fitting where the hydraulic pressure joins from each engine to the reservoir. Here is the like indicated:
Attachment:
hyd-line-3.png

The two purple things are flow switches that indicate low flow from one engine or the other. The flow joins at the tee fitting which then services all four hydraulic subsystems.

If you look carefully, you can see a drop of fluid above the left flow switch and you can see how the left flow switch is wet looking.

I'll continue this story in my next post.

Mike C.


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Last edited on 13 Jan 2023, 14:37, edited 2 times in total.

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 13:27 
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Company: Ciholas, Inc
Location: KEHR
Aircraft: C560V
The hydraulic line was removed.
Attachment:
hyd-line-1.png

It became pretty obvious it had a hole in it right where it pass through a grommet.
Attachment:
hyd-line-2.png

That pin hole was created seemingly by corrosion or maybe a piece of grit in the grommet rubbing on the line. I could see residual fluid coming out even after it was removed, so the cause was very clear. Had we flown again, there is no doubt we would have emptied all fluid and lost the hydraulic system entirely.

I have had similar failures over the years in other planes. My T210L, for example, had a slight smell of avgas in the cabin and that was finally traced to a pin hole in a similar type line. Don't let anything touch these lines as that creates failures. It would be a good idea to inspect them very carefully at all grommet and clamp locations.

The line is made from 5052-0 aluminum line with AN819/AN818 fittings. This is common stuff, the fittings are $2 each end and the line is $4/ft, so there is not much material here. Most homebuilders probably have the flare tool and bender to make it. Unfortunately, no mechanic nearby had the material and tools to do it. Also, JetEast folks said they aren't allowed to make lines, we have to buy the prefab one. Sigh.

Okay, looked in the IPC (illustrated parts catalog) for my plane and it is just not clear what the PN (part number) is for this line. though I had picked out a likely one. I ended up sending my photo to Team Legacy at Textron, and they confirmed my choice was the right PN. Textron had 1 in stock. Yeah! It was $647. Oh well. I paid for first overnight FedEx (by 0800 ET) delivery and ordered it. That cost $342 because Textron used a huge box to send it that weighed only 5 lbs. I later quoted the same shipment as if I was doing it and it came to $550! Shipping is a major cost these days for airplane parts so anything you can do to go ground helps a lot. Small bonus: Massachusetts does not charge sales tax on aircraft parts, so that saved me a little.

The JetEast guys had done all they can do by 1400 ET and left. They would be back at Wed at 0800 ET.

The Great NOTAM Outage happened early Wed morning, but despite that, FedEx got the package to the FBO at 0807 ET, so pretty close. The JetEast guys were there and got right on it. The line was the correct one (one of my concerns) and fit. It took about an hour to get the stupid clamps on it, though. Once all in, things were wiped down and then fluid was pumped into the system using the drain valve on the service port. You do this until you get the reservoir to overflow. Since the reservoir is highest point in the system, that is where the air goes, so you manually relieve it down to about halfway between "FULL" and "OVERFILL".

We left it in that state a bit and no leaks were detected. This was about 4 PSI pressure.

The JetEast guys had no actual hydraulic mule, but had brought a "robo mule" which works by removing a hydraulic pump from an engine and rotating it with a motor. I decided that was stupid and instead we did an engine run instead. The idea is to cycle the hydraulic system to get air to the reservoir, then vent it back down to "FULL".

With the engines running but without using the hydraulic subsystems, you get about 60 PSI pressure. We ran this way for about 2 minutes. Once that was done, I selected "EMER STOW" on the TRs. What this does is push the hydraulic pressure up to 1500 PSI but doesn't actuate anything (if the TRs are stowed). We ran that way for about 1 minute and no leaks.

Also, this allows us to measure the compressibility of the system. If there is a lot of air, when you go up in pressure, the volume shrinks. By watching the plunger, we can gauge how much air there is in the system. Upon going to 1500 PSI, the plunger moved only 1/4" which is pretty good. This can be from lines expanding as well as some air.

I then exercised the hydraulic systems I can. With the plane on the ground, I can't cycle the gear. With only the right engine running, I can't cycle the left TR. Otherwise, I can cycle everything else, flaps, speedbrakes, right TR. It all worked as expected. I shutdown.

The reservoir was bled down to about 1/4" over "FULL" mark. This gave a little margin to bleed it down later to vent any air.

Paperwork was done and the plane was ready for flight by 1100 ET. We departed at about 1200 ET and the flight was no issue. It should be noted that I bought some tools and took them home with me, so I again had some tools onboard. Clearly, that is the secret to avoiding mechanical failure.

After landing, the reservoir was actually higher than before takeoff, probably due to having warm fluid. I'll check it carefully the next time I am at the plane.

All told, 42 hour delay from intended departure to actual. About $1K in parts and shipping. I don't have the invoice from JetEast, but at $400/hour, probably going to be high. Oh well.

Some things I have learned from this:

Skydrol comes in various "flavors". Team Legacy confirmed that Skydrol LD4 can be used and mixed with Skydrol 500B-4. JetEast had only LD4 and my pane was serviced with 500B-4 (at least, that is what I thought it was). I contacted Team Legacy just to be sure since the MM was slightly ambiguous. LD4 and 500B-4 have slightly different specs, so not identical.

Alcohol is the best clean up for Skydrol. A squirt bottle and lots of rags cleans it up pretty well. The JetEast guys did a pretty good job cleaning things up but I won't really know how badly the paint or other things are affected for a while. I was seriously happy not doing it myself.

JetEast guys had a roll of gray oil absorbent pads that worked very well to handle messy situations. Might be worth having some of that around. Works much better than the blue shop towels. Looked like this stuff:

https://www.amazon.com/Aain-LT010A-poly ... g=btalk-20

Never fly without my tools. Having them aboard prevents needing them. This was literally my first flight without the tools.

Falcon Air was very helpful. It is hard to imagine this going as well at any other FBO in the Boston area. We got to do most of the work in a heated hangar. The weather was pretty good these few days, though cold. Boston weather could have been much worse.

The Citation ecosystem is extensive. Lots of folks know about them, how to work on them, who works on them, etc. The MU2 ecosystem is far less extensive, but none the less quite responsive as well.

Making basic things like aluminum lines is not what mechanics do any more. That surprised me. A stock of lines and fittings would allow you to make any of the hundreds of such lines that are on my plane.

Mike C.


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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 15:00 
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Great write up, thanks for taking the time to do so. I learned a few things about hydraulic systems.

AOG maintenance events are expensive! I will for sure carry tools as a preventative measure!

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 15:02 
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Username Protected wrote:
Great write up, thanks for taking the time to do so. I learned a few things about hydraulic systems.

AOG maintenance events are expensive! I will for sure carry tools as a preventative measure!

I'll echo what Jon said. Really a great write up with excellent photos to match. Makes me think about all those aluminum tube fuel lines in my Baron....

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 15:26 
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Thank you Mike for writing this up.

It’s interesting that JetEast won’t make lines. I can see why not - liability. Still a little surprising.

I have a couple of flight schools and our own maintenance shop with two full-time mechanics. And a huge parts inventory. Including complete, built-up QEC spare engines. I HATE AOG. We maintain 14 school planes (mostly Cessna) and eight or nine personal or friends’ planes (all sorts of stuff - wooden Falco F8L, Marchetti SF260, Waco ZPF-7, Great Lakes, Cessna T303, T-6 Texan, Pitts Model 12, Decathlon). It’s a varied fleet. We make our own lines and hoses.

Z.


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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 15:51 
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Ahh, yes. The corroded line syndrome. I guess that’s the one advantage of pulling on the ramp where the Dinosaur Doctors work; they’ll know how to fabricate lines. On the last 12K hour I personally made 8 or 10 for the wing center section and other guys replaced long sections of the climate control system pneumatic lines in the cabin.


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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 16:01 
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Was there something in your tools/spares kit that would have addressed this? Just curious if that was a simple omen or legitimate foreshadowing at work.


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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 17:44 
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Company: Ciholas, Inc
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Aircraft: C560V
Username Protected wrote:
Was there something in your tools/spares kit that would have addressed this?

Yes, the general protective cloak that carrying tools has on preventing away from home disasters.

Humor aside, no, not really. I didn't have the tools to make a line, nor the materials.

Having JetEast make a line from raw stock would cost as much, probably, at $400/hour.

My local shop has the tools and could have made it for $100 probably. I could buy the tools (flare, bender) and do it myself, but I'm likely not to need that in the future. My brother has the tools in Wichita, too, along with likely the line and fittings.

If Textron had no stock of the line, I would have ordered the materials from Aircraftspruce and made the line personally under the "owner produced parts" rule, or even claim these are "standard" parts. It would be like using a spool of wire to make a cable assembly versus buying one premade. It is still approved parts to use the same line and fittings.

I almost did order the materials and tools as a backup, but decided not to based on JetEast being uneasy about it.

Quote:
Just curious if that was a simple omen or legitimate foreshadowing at work.

The omen was the slightly low hydraulic reservoir indication at preflight before flying to KLWM. If that occurs again, I'm checking things out more thoroughly.

Mike C.

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 17:46 
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Username Protected wrote:
Ahh, yes. The corroded line syndrome.

I've seen a number of examples of this, so do pay particular attention to anything that touches these lines and creates the potential for dissimilar metal or moisture based corrosion.

Mike C.

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 18:22 
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I hate hydraulics. I understand why they're used, but in an environment where everything shakes and moves, it's bound to fail eventually. And in fact, every single AOG occurrence I've had (except for my engine failure), was hydraulics related. I know electric actuators weren't really an option when these things were designed, but it seems new planes use them more and more. Good riddance to hydraulics.

As a side - all the forklifts I've ever owned always leave a little pool of fluid under them. Is there a single hydraulic system that doesn't leak a somewhere?

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 18:26 
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Great write up. What type of hydraulic fluid would an MU2 use?


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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 18:27 
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Great write up and seems as if the best anyone in your position and place could have done. Very professional approach.

Regards, Tom

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 18:35 
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Username Protected wrote:
Great write up. What type of hydraulic fluid would an MU2 use?


5606


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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 18:49 
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Username Protected wrote:
Was there something in your tools/spares kit that would have addressed this?


Duct tape. :D

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 Post subject: Re: My Citation V AOG event
PostPosted: 13 Jan 2023, 18:51 
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Ah yes. The $5000 pinhole! :bugeye:
:D

Is there a recommended aluminum line replacement timeframe? Are there other lines you may replace now just to avoid a similar cost and inconvenience?

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