I love the idea of an STC of any other type of hydraulic fluid other than Skydrol. Surely there has to be something out there that is compatible with Skydrol o-rings without the paint eating qualities of skydrol!

Flammability is the reason. 5606 might as well be diesel oil. I think Boeing switched to it after a 707 caught fire due to a high pressure hydraulic leak.

And if Textron had no stock of said line, then what?

Most of the lines I looked up from the parts diagram were zero stock. Indeed, the one line I needed was in stock, and now isn't since I got the last one.


Flammability. 5606 is oil based and will burn especially under high pressure as a spray.

Once you lay out all the requirements for a hydraulic fluid, it is actually quite hard to find ones that work really well.

Mike C.

Then you break out the flaring tool and tube bender. I probably got the last one too and the next time someone checks stock the lead time will be 8 months and the price will be $4000.

Think it has higher heat/fire resistance. The Commanders used it when they had the early 3000psi hydraulic pressurization system (a stupid idea), but when that got upgraded to bleed air, then they could reduce it down to the 1000psi for the gear flaps etc and also move over to 5606.

Time for a final report on this event.

I have flown the plane four times and everything has worked perfectly. The hydraulic system shows no change in fluid level, so seems to be leak free. I had my local mechanic visually inspect all the other lines and nothing concerning was found. So for now, it feels like things are fully repaired.

About 10 days after the event, I got an invoice from JetEast for $8358. I was expecting a high number but not THAT high. Ouch.

That total represented 21 man hours on the airplane work itself, 14 hours of travel, 2 hours of work order prep and paperwork, $588 of hotel, per diem, and mileage, and $370 in shop supplies. Labor is $200 per man hour.

I had inquired if they needed to send two people since really, only one can actually work in the tail at a time. But they insisted on sending two. One would have been enough in reality.

Actual hours on site at the airplane was 0930 to 1400 first day, 0800 to 1100 second day. Add that up and it is 15 man hours on the airplane itself. So 21 hours was a bit excessive.

The 14 hours travel time was really out of line. I had chosen JetEast over the Textron MSU because they were a 30 minute drive from KBED to KLWM. So why did it take 14 hours of travel time? Found out they sent one guy from fairly far away instead of from KBED. So much for the local advantage.

All total, there was 35 hours of AOG team on the invoice over a span of a day and a half. It just wasn't possible to book that much time, 17.5 hours per man.

After some discussion with JetEast, I negotiated an adjustment of 9 hours less than invoiced. Final invoice was $6558. I still think that was more hours than they actually spent, but given where we started, I think that was the best I could do.

Further, they charge 3.5% for credit card transactions, so we wired them the money to save about $230 in credit card fees.

JetEast rates are for Gulfstream operators. For those guys, this amount is a rounding error. For me, this is was a fairly big expense for what amounted to a single 1/4" line that I could have made from about $30 in parts given the right tools. My entire phase 1 to 4 inspection was only $13K, to put this into perspective.

All together, the JetEast cost, the line, the extra overnight, misc expenses, this was about an $8000 event. Obviously I can manage an expense like that given the plane I fly, but that's still a pretty big number.

I don't know what it would have cost to have the Textron MSU come from KSWF to do the work. Maybe it would have been the same, maybe worse, maybe better. I don't know, but I will be more inclined to give them a try next time. At least they know it isn't a Gulfstream. I will always prefer a local guy if I can since I can provide the manuals, background, and expertise they may lack.

It would not take a very extensive set of tools to be able to handle this issue. A tubing bender, a flaring tool, a small hand pump for the hydraulic fluid, and a bottle to catch the overflow. The bender and flare would make the line using AN818/AN819 fittings and raw line stock. The hand pump would refill the reservoir until you got overflow, then bleed the system down to the full mark which vents the air.

I probably will never need to do this again, so I have not acquired said tools, but I think about it.

Since I have invested so much time in fixing up the airplane, I have noticed I tend to be very careful when flying the plane so I don't damage it. I don't want my time investment to be lost over some brief moment of stupidity.

I don't expect issues like this will be common, thankfully.

Mike C.

Thanks for the epilogue.

I wonder if it was a manpower availability issue that pulled the guy in from the more distant location. That would have gotten under my skin a bit, too.

How much in additional expenses related to the event? Hangar, hotels, etc?

Have you considered, if you did not have a schedule to keep, how many extra days to fix "economically"?

While on a different scale, this reminds me of losing my alternator in St. Paul, and, 2-3 years later, my voltage regulator over Dalton, GA. Both cost me a day, but diligent scrounging, decent people, and a willingness to get my hands dirty all turned them into stories to add to my imaginary journal, "Adventures in Aircraft Ownership".

Thank you Mike - all very useful information as I consider our next aircraft.

Similar to you - we do time spent extra personal time to bring our aircraft up to a level.

I paid Falcon $300 to cover what their mechanic did, parking, and the use of the hangar. Seemed more than fair given my plane made a mess in their hangar and their mechanic spent at least an hour on my plane looking things over.

Extra hotel, food, car, etc, about $250.

Oh, forgot the airline tickets for my employees to get home, about $1300.

So the entire event is pushing $10K. This goes to show you how valuable it is to find issues early, so when I am in inspection or in the shop for other reasons, I look around for other things to fix and get them up to shape.


Probably 1 or 2 more.

I'd need to buy the line from Textron, or the materials to make it and the tools. I'd need to buy the materials to clean up the Skydrol, the absorbent mats, the alcohol spray, etc. I'd need some Skydrol. All of that could be acquired overnight.

I'd then need a hand pump to fill the system back up. That's harder to come by, something specifically rated for Skydrol. I've been on the lookout for such a thing and have not found the exact right thing.

And then I'd hire a local mechanic to do the work if I could find one. The mechanic at Falcon could probably do it, but that presumes they were available, which wasn't clear. I'm not personally small and agile enough to do the work myself, I'm too old and too big to be an aircraft mechanic. It was pretty nasty work cleaning up Skydrol, so the 3-4 man hours doing that was worth every penny.

Had this been found at my home base, the cost would have been maybe $2-3K to fix after the fact, and a lot less if discovered before it leaked.

Another option would have been some sort of field repair. Find the leak, cut the line, and put in an AN815 union. I'd still need the flaring tools, a way to clean things up at least a bit, and then I'd have to do the real repair later. I'd still need a way to replace the Skydrol lost. The break was in a place that the union wouldn't have fit, too. SO it wasn't much less work to replace the line properly. No other field repair seemed sufficiently airworthy considering the line sees 1500 PSI at times.

Another thought was flying it as is without using any hydraulics to someplace like KSWF where the Textron service center is. The idea is to fly gear down, flaps in approach, and not use TRs. The flight would be short, like 30 minutes, there was still some fluid in the system, so the hydraulic pumps would survive that. In the end I rejected this as too stupid, a way to make a bad situation worse.

Mike C.

Mike C
I purchased a hand pump to put skydrol in my plane . I still have the box for it & will send you an email this afternoon.

Thanks!

Mike C.

On the 501, there's a port in the door. Basically, it looks like a $1000 metal garden sprayer that pushes the fluid up. Some airplanes have the hydraulic hand filler in the little hatch in the bottom that has an antenna looking overflow port.

You can also refill the tank with a mule.

Nasty stuff, I wish we could switch fluids. I'm willing to fill up a junk airplane with some other fluid and do some testing if anyone wants to provide some data on Citation oring compatibility with the fire retardant version of 5606. This STC needs to be given to humanity for free or close to it.

I'll need a picture to understand what you are saying.

I do have a hydraulic hatch on the bottom right of the fuselage with fittings where the mule attaches. There's nothing like a hand filler there that I can see.


Yes, but hard to find shops with one.


The conversion effort is very high since basically every hydraulic valve, filter, actuator, pump, and seal would need to be changed. This would come at extreme cost.

The ideal strategy would be to find a new nicer fluid that is compatible with existing Skydrol seals so you could drop it into the system without changes. Alas, if such a thing did exist, we would have probably heard about it.

In the end, if you keep the fluid in the system, the issues are not that significant.

Mike C.

If you have a tubing flare tool and tube cutter a possible get home-temporary fix could be-
Once the corroded area was found, cut the original tube on either side of the frame. Place an AN nut and collar on the line and flare. Install a -4 Union and then make a filler line to fit between the unions.
If there isn't any AN parts around many Hydraulic Hose shops, such as Parker Stores, have JIC collars and nuts, as well as the unions in Steel. JIC is the same as the AN standard for the angle of the flare. Another source of these JIC parts is McMaster Carr.

I had to educate my mechanic on that. Even though he had heavy machinery experience, he was not familiar with JIC or the fact that it was compatible with AN. Makes temporary repairs very easy.