SWIFT HYDRAULIC SYSTEM

THE RED STUFF...
My experience with other aircraft has demonstrated to me that periodic replacement of the hydraulic fluid is probably best. It gets very ugly looking after a few years. I can easily do on the brake system, but what is the best way to do on the landing gear/flap system? Is there a point to force fluid in which will force it through the system to be expelled at another point (the reservoir)? Steve Roth (stevenroth@aol.com)

Steve,
The gear/flap system on the Swift is self-bleeding, with the pressure/return lines reversing function upon retraction/extension. If water accumulates in the hydraulic fluid, due to condensation or leaking into the bleed hole in the reservoir, it will be necessary to crack a fitting on each gear, and at the flap actuator and cycle the gear and flaps until the water is purged. The brakes are a "dead end" system, and the brakes should be bled periodically. Read Dick Collins report on this on the Swift Home Page.  --  Jim

FLAP ACTUATOR O-RING REPLACEMENT CAN CURE HYDRAULIC BLEED DOWN... (800100)
From: Al Andersen <72032.237@compuserve.com>
Subject: July #6 GTS Internet Update
Hearing about the hydraulic bleed down problem reminded me of a similar thing that happened in my Swift back 20 years ago or so. I was plagued with the cycling hydraulic pump in flight until I took the flap actuator out of the airplane and resealed it. It had O rings in it that looked original, and acted like they were 30 yrs old then. The landing gear tends to get resealed as leaks develop, as they are usually external. The flap actuator usually leaks internally, and therefore seldom gets attention.

Once I got on my back,& pulled the flap actuator out of the airplane, (it's not the easiest thing to do, and kind of messy) and resealed it, the problem with the cycling hydraulic pump went away, and the pressure stayed up remarkably well in the system. This doesn't totally address the overcenter up linkage problem, but will tighten up your hydraulic system so it won't be so noticeable. AL

HARRY SAYS...(110300)
From: Harry Asbury <gypsyone@tds.net>
Subject: Just something I learned many years ago
Hi Denis,
I enjoyed the newsletter very much and was very curious about the comments on wing tips. Do I detect a tendency to ground loop the Swift a lot with the present generation? I don't know if many people are aware of this but I will throw it in just for information. On any hydraulic system, brakes, flaps, servos, utility systems, if you let them set for four months or longer without activation, the condensation that is mixed in with the hydraulic oil will turn to water and settle to the lowest point in the system. The first warning you will have of this will be a leak around the seals at the lowest point of the system. What you will find is corrosion from the water on the aluminum castings has caused pits in the castings. The only recourse is to replace the casting. This could be wheel brake cylinders and etc. The best course of action when putting an aircraft, and even your car with power steering, up for a long period of time, is to drain the system completely, and reservicing the system before storage, to remove the water that has formed from condensation in the system. Keep this in mind when buying an aircraft that has been sitting in one spot without running during this dead storage time. One other thing I noticed now. The owners of the Swifts seem to love to polish the birds. Great, but don't polish the chrome on the oleo landing gear struts. If you do this, you will cause the landing gear struts to wear the seals out at a very rapid rate and then have leaking landing gear. I learned this on working with the Marines on the Presidential Helicopters. They polish everything and we had a very high rate of leakage of the oleo struts on the VH3D helicopters. I got curious and watched them polish them one day and figured out the problem right away. I very light coat of hydraulic oil will prevent this. Yes I know it accumulates a lot of dust, but to wipe the struts with an oily rag is a lot easier than replacing seals. I hope this piece of information will help someone with their Swift if they haven't already experienced this kind of problem. -- Harry Asbury

LANDING GEAR PROBLEMS? BLEED THE AIR OUT..(120300)
From: Harry Asbury <gypsyone@tds.net>
Subject: Re: December #2 GTS Internet Update
Dear Jim, I'm not up to date on the Swift's hydraulic system, but I've had a lot of experience on other hydraulic systems and one that has happened to me quite often was to have some part of the system not to work under load, such as the gear retracting in the air, but works fine on the ground. I have found in most cases when I can't find anything else wrong with the system, that there is a little air in the system and it will compress enough to stop the actuator from performing to it's maximum limits under load. The solution was always to bleed the system simply by jacking the aircraft and actuating the gear at least twenty times. The way the actuator is mounted in the aircraft sometimes lead it to trap air and it's awful hard to get it out. Just a thought on the gear retracting problem. -- Harry

Harry,
Good point. If I were working on Steve's aircraft I would have cycled the gear numerous times on jacks. I assume Steve and Ray also did this. When I am trying to help via email I don't know if they for a fact did that. Air in the system will indeed cause symptoms like what they are experiencing. The Swift system will usually bleed itself out after a few cycles. -- Jim

MORE FROM HARRY ON THE IMPORTANCE OF BLEEDING THE HYDRAULIC SYSTEMS...(120300)
From: Harry Asbury <gypsyone@tds.net>
Many a time I would ask the military did they bleed the system and all ways they would say yes! I have found that they would give it a half hearty try and in some cases on the larger hydraulic systems they would never get all of the air out. I know on the SH3s and HH53s this was a problem with the landing gear. I've even seen it in the rescue hoist systems. In that case it would cause a chattering on the up cycle with a weight on the hook. The big internal winch system wouldn't even pull the cable in if there was the slightest air in the system. I've even investigated fatal crashes where the control system wasn't bleed properly and this caused the pilot to get out of sync with the cyclic stick to the response of the aircraft to the controls. It got so bad as that he was 180 out with the response and crashed into the sea. I didn't figure that one out until four years later when the same thing happened to another of the same type aircraft and believe it or not, the co-pilot on the fatal crash was the command pilot on the one we got back. Once on the ground, I tried the controls in a low hover and right away I could feel the spongy respond and knew it was air, due to a auxiliary servo change in the aircraft the day before. They had failed to bleed the complete system. This gave me the answer to the fatal crash. The same type of maintenance had been performed on the fatal crashed aircraft. I guess if you stay in this business, you will eventual see the same thing occur again down the line. Pardon my long winded message, but I have always loved working and solving the little mysteries of maintenance. -- Harry

YUCKY YELLOW... (040101)
From: Al Andersen <72032.237@compuserve.com>
Just a little insight into the strut oil on the ELI Gear being a different color (yellowish). 5606, along with automotive brake fluid is hygroscopic, which is a fancy word to say that it absorbs water over time. It is very common in airplanes, (which seldom have the hydraulic fluid changed) to see the 5606 hydraulic fluid turn a yucky yellowish color when it becomes saturated with water. This is bad for the system because water creates corosion in the calipers of the brakes, and in the interior areas of the strut. The first time I saw this yellow fluid I thought that there must bea different type of oil used in the older airplanes. Probably not. It is more likely just old 5606 saturated with water. There is something to be said for changing the brake and strut 5606 aboutevery 5-7 years or so to prevent internal corrosion problems from happening to your airplane as the fluid eventually saturates with water. AL

SOME ADVICE FROM MONTY... (050101)
Checking hydraulic quantity is a preflight item. I usually check before every flight. If you have flown 30 some hours and not checked the hydraulic fluid I can almost guarantee it is low. A full hydraulic reservoir is probably the quickest, cheapest fix for slow gear retraction.

The early Swifts had a filler hole in the top of the reservoir with a dipstick to check quantity. Later airplanes had a pipe elbow in the front of the reservoir and you just filled it to that level. The early setup was almost always overfilled and any spillage from filling ended up with hydraulic fluid leaking thru openings in the firewall and running down the gear and flap selector rods. Overfilling doesn't really hurt anything, but when cranking the gear down on jacks, an overfilled system will blow fluid thru the vent and all over the pilot's windshield.

LEAKING HYDRAULIC FLUID RESERVOIR...(030102)
Subj: Emergency Pulldown
From: Brian Silcox (briansilcox@harbornet.com)
Hi Monty,
I am doing my annual on N46GS, had a strange thing happen when I pulled the gear down with the cable this time. I have been doing this each year since I got the plane ten years ago, and never had this: As the second (left) gear is reaching the stop limit, the reservoir over fills and squirts several ounces of hydraulic fluid out the cap vent. Thinking it was a transient anomaly, I reset the cable, refilled the reservoir and recycled the gear up and down.... no problems. fluid level remained at the proper level. I once again pulled the gear down manually (cap off, cowl open) and watched the gusher a second time. I repeated the above one more time to ensure I wasn't seeing things, and once again same! It works fine in both the normal, hydraulic powered cycle, and extends fine manually. I am suspecting a port problem in the powerpack... return fluid is moving back to the reservoir, but not vice versa through the down lines during the pulldown. When the overflow occurs, the reservoir is absolutely full, and stays that way till you activate the system hydraulically, and then it indicates the fluid loss on the stick. Ever seen this one? Thanks, Brian Silcox

Brian
Unusual? No, that is a very USUAL happening. This is the first time in 10 years that that happened? You must run very low levels of hydraulic oil in your reservoir. Ordinarily, when the gear is cranked down it is quite common to have hydraulic oil spray out the vent and over the windshield. Rather than repeat myself, go to the "Monty the Answer Man" archive and read about "Landing Gear - Emergency Extension". I think Charlie Nelson even talked about that same thing in this months newsletter. Jim

HYDRAULIC SYSTEM QUESTION...(800402)
Subj: Hydaulic system
From: Pat Waters <GPWATERS@aol.com>
I have a question as to the hydraulic system. When I bought my Swift, it had this elbow and glass fitting which vented and upon use of the flaps, would project fluid out onto the cowl. I called the office in Athens for help and was told that the system did not need a 'vent hole' as was in the top of the elbow. I also have a bolt/plug in the after part of the pump housing which is not real tight, but I do not see fluid emitting from it. My question, is does this system need to have a vent as in the elbow or is it a closed system. Athens said to just put a #10 plug in where the elbow was and go flying. I have done this a little, but fear I am building a pressure somehow on the system that may cause it to burst. Please advise as I am grounding myself until I am sure. Also, if the elbowis requires, my glass was broken when I dropped it. How or where do I find a complete glass elbow? One more question, is the cylinder resovor next to the pump/resivor for the breaks or a reserve for the pump? Thanking you in advance, Pat Waters

Pat
I'm not sure I follow you entirely, but the hydraulic reservoir should be vented. The vent is just a simple small hole (#50 or smaller) in the dip stick on the top of the reservoir. The later reservoirs had an elbow on the front of the reservoir with an 1/8 pipe plug which is removed for filling with mil 5606. This is located to prevent overfilling. These later reservoirs had a small vent hole just aft of the motor. If you have an early style reservoir with the plug on top, just drill it. If you have the later style with the filler at the front you should have the vent hole on top. The problem that can arise is when the late reservoir is used with the early top and a plain pipe plug is installed in the dip stick hole that is not drilled. To solve that problem, just drill it. You may be overfilling the reservoir. It is common to have fluid come out the vent when cranking the gear down, but not when simply operating the flaps. There is supposed to be a baffle in the reservoir to minimize fluid loss thru the vent, maybe somone has removed it. The reservoir next to the hydraulic package is the brake reservoir. Keep it near full and also, it should be vented. -- Jim

HYDRAULIC FLUID ALL OVER THE BELLY...(OCT 02)
Subj: Hydraulic leak
From: Marvin Homsely <marvin@accesstoledo.com>
Jim, more stuff that may be of interest to someone. I landed last weekend and had hydraulic fluid all over the belly. It turned out that I had a pin hole in a hydraulic line where it goes thru the bottom of the firewall. On my plane there is a phenolic block there that all six hydraulic lines go thru. After removing the block and inspecting the lines five of the six had severe wear from that block. One line had no wear at all. I decided to replace all of the lines. After further study it looked like it would be very difficult if not impossible to pull the line out of the belly of the plane. It is one piece and there is just not enough room to pull it out with that 90 degree bend in it. It is just too close to the motor mount. I ended up replacing just the damaged tubing. Just cut the tubing several inches above the bottom of the firewall and again several inches back inside the belly. Make a new piece with a simple 90 degree bend in it and splice it in the line. I do not believe this new line will ever need replaced but it would be an easy job if necessary. Bleed the lines real good, cycle the gear and flaps several times and it is as good as new, maybe better. Total cost was around fifty dollars. I wonder what a shop would have charged for this. Marvin Homsley N80740 marvin@accesstoledo.com

Marvin
Yes, that is a common problem. On Mick Supina's Swift we installed AN833-4D elbows in the firewall for those lines. That is not an original idea, Temco did the same with the Buckaroo. -- Jim

WHAT BRAND OF FLUID? (APRIL 04)
Subj: Hydraulic Fluid and Filling Tips, Etc.
From: James Cummiskey <jccummis@yahoo.com>
Hello, Jim. Can you clarify what brand and type of hydraulic fluid I should be using in my Swift? Also, I read in the archive that it is easy to overfill the older style reservoir with the filler hole and dipstick on top. Do you have a recommended procedure to avoid overfilling? Is Par-al-ketone a good choice for lubricating the emergency gear cables? I had one of my cables jump the pulley on me (I have the cable guards installed), and I intend to drill the actuator pulley per the Swift Association "Maintenance and Operation Information for the Swift." Finally, do you recommend the GAMI injectors for the IO-360? Looks like I'll be flying N3800K with her new paint job out to the Nationals in Athens. See everyone there! Regards, Jim N3800K

Jim
The hydraulic oil is 5606, Mil-H-5606, made by just about every major oil company. (Shell, Texaco etc.) The early reservoir should have a dip stick and you should not fill above the top hole. If you don't have a dipstick they might have one at Swift Parts or you could make one. Paralketone is fine for any cable. Several of my friends have the GAMI injectors and swear by them, although one of them has a fuel injection problem right now, if it turns out to be the GAMI injectors I will let you know! -- Jim