LANDING GEAR ACTUATOR OVERHAUL...
Subject: Gear actuators
From: Steve Wilson <teveWlson@aol.com>
What is your secret for sealing gear actuators? I just took both out of
N77753 and rebuilt them again. About 125 hours since last rebuilt and
they pee out fluid much of the time when the wx is near or below freezing.
After getting them done and back in, the right one seems tight, but the
left one is really leaking worse than before with pressure applied to
hyd system. The fluid comes out of the rear of the actuator. None from
any other location. I suspect that it is coming out of the actuating arm
seal rather than the large seal on the outside of the brass bushing. What
do you think? Charlie told me one time that he has used two "O" rings
instead of one. I don't know what that might do except move the "O" ring
away from the small corrosion area on most of the shafts. I suppose if
you did that you would have to leave out the leather packing, no? I do
not think the shaft would stand much smoothing as it would reduce the
diameter of the shaft and work against sealing. Any suggestions you have
would be great. I feel like I am shoveling sh** against the tide. Steve
If there is corrosion evident on the shaft, I have eliminated the back
up ring and installed two "O" rings also. I also assemble the "O" rings,
in all locations, using plenty of Vaseline. I don't know if this is any
secret but I have had pretty good success. For a couple of years, my 31B
left actuator would drip fluid in the winter, making a mess on the lower
centersection skin and hangar floor. Pressurizing the system, (running
the hydraulic pump) would make it stop for a while. Statically, with no
pressure on it, it would then seep fluid again in a week or so. During
the summer, it would not leak a bit. I had rebuilt the actuators in '91
or '92, and only had about 125 hours time on them. Last summer, I bit
the bullet, and pulled the left one out and replaced the "O" rings with
fresh ones. The ones which were in there looked perfect, except they were
maybe a little hard and flat. It hasn't leaked a drop since. Perhaps the
secret is the age of the "O" rings. -- Jim
MORE ACTUATOR OVERHAUL DISCUSSION...
From: Don Bartholomew <email@example.com>
Organization: The Aeroplane Factory
Subject: Re: Leaking gear actuators...Fix???
The secret is to do the proper dance to the actuator gods. Unfortunately,
I have not found that dance or they don't like the way I do it! So......
these are things I have tried, sometimes successful, sometimes not. Good
Luck and let me know if any work for you. (I also have sub freezing temps
and see similar problems)
> Hi fellows... What is your secret
for sealing gear actuators? I just took
> both out of N77753 and rebuilt them again. About 125 hours since
> rebuilt and they pee out fluid much of the time when the wx is near
> freezing (actually they weep most of the time, but not as bad when
This part is understandable since
the o-ring is less pliable in the cold.
> Now please don't tell me to
move south, I want to do that too, but I
> REALLY would like to solve this problem once and for all. After getting
> done and back in, the right one seems tight, but the left one is
>leaking worse than before with pressure applied to hyd system. The
> comes out of the rear of the actuator; none from the front. I suspect
> it is coming out of the actuating arm seal rather than the large
seal on the
> outside of the brass bushing.
This you would have to determine
by inspection, and possibly pressurizing the system after the actuator
> What do you think? Previously
> & Montague both told me that they have used two "O" rings instead
> I've never tried this, have you?
I have tried this once and it did
seem to work. I used the second o-ring in place of the leather packing.
The o-ring is wider than the leather, so when things are assembled, there
is pressure on the side of the o-ring which tends to push them tighter
to the shaft.
> I don't know what that might
do except move
> the "O" ring away from the small corrosion area on most of the shafts.
> suppose if you did that you would have to leave out either the leather
> packing or the steel ring, no? If so, which? I do not think the shaft
> stand much smoothing as it would reduce the overall diameter of the
> if it is that sensitive, probably wouldn't stand much of that.
I have had some success with using
a very thin piece of emery cloth and polishing just the pitted area. This
leaves a slight grove, but gives a better surface for the o-ring to ride
on. Don't polish the entire shaft, this would make it loose in the bushing.
I have found that worn bushings definitely aggravate the problem. Typically
I would like to see .0005" to .001" shaft/bushing clearance. If there
is more than this (typically I find .003 to .007" when I take them apart)
the o-ring has a hard time staying in contact with all surfaces, especially
in cold weather.
> Any suggestions you have would
be greatly appreciated. I am about to pull out
> what little hair I have left... Steve W
First, check bushing clearance next
time they are apart. Sometimes I have to make custom size bushings to
account for worn shafts and housings. The bushings are made from Navel
Second, Locally polish as much pitting
as possible. Spin the shaft in a lathe and use a thin strip of crocus
cloth to polish the affected area. Do not exceed .002" max local polishing.
Third, Sometimes Granville strut seal helps keep the seals more pliable
in cold weather. Forth, Pray and Dance a lot to the Actuator Gods. If
you find the right combination, let me know what it is!
Good Luck, Don and Helo
IN SEARCH OF RARE EARLY OPEN RACK
LANDING GEAR ACTUATOR... (11699)
From: Pete King <firstname.lastname@example.org>
The early gear retraction actuator was an open rack and pinion assembly.
It was vulnerable to icing and was therefore replaced with the actuator
we all know. Does anyone know what it looked like ?? have a drawing??
have one??? I would really appreciate anyone's help. Many thanks, Pete
In 1969 we had a flyin at Santa Paula, CA . The featured speaker was Eugene
Clay who was hired by Globe in late 1945, after WW2 career as a design
engineer for North American. He was proud of the fact that his major accomplishment
was the redesign of the P-51 fuselage to the bubble canopy configuration
of the P-51D. If you look at many of the drawings of the Swift you will
see the name "Eugene Clay" in the corner. He related that arriving in
Ft Worth, he was met by (Globe Chief Engineer) Bud Knox and others who
told him, "We have a problem". They were flying several GC-1A's at that
time, and with just a few hours on the airplanes, the gear actuators were
failing to operate. It turns out the open rack and pinion was quite succeptable
to dust, dirt, debris and water, not to mention snow and ice. I don't
think you want one! They never did work very good. Plus - N80518 never
had them. I think there were only about 5 airplanes built and flying with
NX licenses when they changed them. According to Mr Clay, he had
a major part in the redesign of the actuator, which was then produced
in CA by Adel. Others who attended that flyin who are still around include,
Charlie Nelson, Pat Moore, Rod Daulton, Jess Myers, Mark Holliday and
perhaps several that I forget, maybe their memories of Mr Clay's talk
include more detail. -- Jim
EVEN I HAVE A QUESTION ONCE IN
From: Denis Arbeau <email@example.com>
Subject: Leaky downlock
Came back from flying today and found some hydraulic fluid streaming back
along the top of the left flap. Traced it forward under the wing to the
wheel well where it seems to be coming from the downlock. Why do downlocks
leak and what must be done to fix them? Thanks, Denis
It happens. "O" rings get old and hard and start to leak. Refer to the
Cummings Hydraulic Manual before starting repairs. The "O" rings are included
in the actuator kit. To further expound....if you overhaul your downlocks,
be careful when you remove the "port A" hydraulic fitting, there is a
spring and two check balls underneath there which can easily be lost.
From memory, if you do lose one or both, the diameters are .125 and .1875
The latch pin must be pressed out. See the schematic in the Cummings book.
Note there are three "O" rings in the downlock. Pick the right sized ones
from the kit. -- Jim
REBUILDING A LANDING GEAR ACTUATOR...
Subject: Re: Swift Gear actuator
From: Jose Ocampo <Planemex@aol.com>
Hi Monty, My name is Jose Ocampo I'm an IA based at Georgetown KY ( 27K
) Im currently doing an Annual Inspection on a Globe Swift GC 1A S/N 8
and during the landing gear retraction test I noticed that while the gear
is in the up position a considerable amount of hydraulic fluid is leaking
out of the R/H main gear actuator, and since this is the first Swift I
have ever worked on I'm not familiar with the procedures and parts required
to rebuild this actuator, the information on the manual that I have is
very vague and incomplete and I would like some advice on this matter
as well as any information about publications out there that may be helpful.
I'm very impressed with the Swift web site as well as yours keep up the
good work and please let me know if I can be of any help here in KY.
I take it you have the "Cummings" hydraulic manual. If not, get it! There
are a couple of things I might add, or stress. When disassembling the
actuator DON'T drive the arm out until you remove the woodruff key. And
before you remove the gear from the rack, centerpunch both the rack and
the gear, (if not all ready done). This may save you a lot of time on
reassembly. When assembling remember, the backup ring goes on near atmospheric,
then the "O" ring, then the steel ring. Use Vaseline on the "O" rings
on assembly. After you get the arm in position, the woodruff key must
be placed in it's keyway before sliding the gear in. Again, be sure the
gear and rack are indexed properly. Sketch or photograph the assembly
before starting. The downlock has a pin that must be pulled or driven
out. Be aware that there are two check balls and a spring under the 1/8"
pipe x AN4 hydraulic fitting. The diameters, if you lose them are .187
and .279. I think the book covers the rest. -- Jim
DRESS FOR SUCCESS... (070200)
From: Don Duke <firstname.lastname@example.org>
Jim, Any suggestions on how to best dress out scratches in hydraulic
cylinders? I used a dremel polishing wheel which seems to have worked
well, but took off the anodized layer (?) in some areas - is this a problem??
It depends. If you just removed a thousandth or so of material, the "O"
ring should cover that. If too much of the wall is removed the internal
leakage by the "O" ring will be too great and the gear operation will
be sluggish. There are still a fair amount of actuators around, if your
gear operation is not satisfactory perhaps you can find one. If the cylinder
walls are "wavy" you will probably have to replace the "O" ring more often
than normally. -- Jim
HYDRAULIC FLUID LEAK... (070200)
Subject: Venting Hydraulic Fluid From The Powerpack
From: Miguel Nelson <email@example.com>
Monty, Any suggestions as to what I can do about venting hydraulic
fluid from the powerpack? I always seem to get a small amount of hydraulic
fluid on the left side of the fuselage, just aft of the firewall particularly
after doing aerobatics, although I may add that I still get some fluid
even after straight & level flight. I am not sure what type of powerpack
I have, but I do not believe it is stock and the previous owner said it
had been modified. My system is tight though and the landing gear raises
in 8 seconds even with the P-51 style doors. I do know that the fluid
comes out of the pinhole vent aft of the motor and the powerpack is not
overserviced. I had heard that the new Bosch powerpack did not have a
vent and eliminated the problem, but I have also heard that new Bosch
powerpack is just a motor change and used the original reservoir which
obviously won't fix the problem. I don't think I can just replace that
vented bolt with a non-vented one without causing other problem. Any suggestions?
Your reservoir is probably overfilled. There are two fillers from different
production times. The earliest had a filler on top of the reservoir with
a knurled knob and a little dip stick. This one was deleted and the later
airplanes had a 1/8" pipe elbow on the front of the reservoir. It is located
only about half way up so there is a lot of air space above the fluid.
If you don't have this setup you can copy it from another airplane or
just be really careful not to fill your reservoir over 1/2 full. You can
also look for obvious stuff like perhaps someone put an oversize vent
hole in there. You might consider putting in a check valve to prevent
negative "g" fluid loss. You can easily make a check valve with a pipe
fitting and a small ball bearing which will only weigh a fraction of an
ounce. Say you are using a 1/8" pipe fitting made out of brass, drill
it with a #10 drill about half way thru from the bottom, then drill thru
from the top with a a # 60 to #50 drill. Put a .187 ball bearing in the
hole, then peen the brass so the ball bearing is captive. It is normal
to overflow the reservoir when cranking the gear down on jacks. Overflow
is normal when cranking the gear down because the volume of fluid on the
down side is forced back into the reservoir and the "up" volume is not
being balanced by going out to the actuator. The Merlyn motor should make
no difference, unless the gasket is leaking at the top of the reservoir,
maybe a new gasket would fix you right up! -- Jim
"WUN HUNG LOW"... (070600)
Subj: Hydralic Pressure Loss
From: Fred Latremore <Spears@snowhill.com>
Hello Jim, I just completed disassembly and reassembly of L/H landing
gear actuator to repair a seep between pulley assembly and housing. I
now have a situation that the hydraulic pump will activate during flight
for a brief instant. After raising the A/C on jacks, I observed that both
actuators will bleed down from the over-the-center position in the up
gear selection and, the flaps will also lower enough to activate the pump.
This occurs with the flap selector in the up, neutral, or down position.
I remember reading about this situation, but, I can't remember where.
Your help will be greatly appreciated. -- Fred S. Latremore N3285K
If the actuators bleed down from gravity, or if the gear can be pulled
down after being up for some time on jacks, the rack and gear are probably
mis-indexed by one tooth in the actuators. The first time the actuators
are disassembled these parts should be marked with a centerpunch. There
are assembly directions in the Cummings hydraulic manual, but it is a
lot easier just to line up a couple of marks! Evidently, you need to start
from scratch. Back the emergency pull down cable off and make sure the
problem is still there. With the gear up, check again if it will come
out on its own, it may take 15 minutes or so for the hydraulic pressure
to bleed off. Remember, the "uplock" is simply the fact the gear goes
over center and gravity locks it "up." If the flaps bleed down, there
is some internal leakage, either at the "O" ring in the flap actuator
or the brass plates in the hydraulic package. -- Jim
FLAP ACTUATOR O-RING REPLACEMENT
CAN CURE HYDRAULIC BLEED DOWN... (800100)
From: Al Andersen <firstname.lastname@example.org>
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
LANDING GEAR ACTUATOR... (110200)
Subj: Out of time actuator?
From: Bob Dopita <email@example.com>
Hi Jim, I finally got the wiring & the plumbing figured out and the
micro switches adjusted when I noticed when the gear is up the right leg
seemed to hang about 1/2" lower than the left. Further investigation
showed that when in the up position the right gear can be "jiggled"
up and down about 1/2" and the left is solid. I tried re-adjusting
the up limit switch but the gear wouldn't go any higher, it just didn't
shut off the pump. I am thinking that the actuator gear is out of time
a tooth or two. Am I on the right track, or is there something else that
I am overlooking? When in the down position both sides lock down securely.
Thanks again for your help. R.A. Dopita <firstname.lastname@example.org>
Bob, I would say you probably have
figured it out. The gear in the actuator is probably mis-indexed by one
tooth. -- Jim
LOOKING AT A LEAKY ACTUATOR BUT
HAS NUT PLATE CONCERNS...(120300)
Subj: Actuator nut plates
From: Ron Williamson <email@example.com>
Jim, I'm looking at a leaky actuator (I know, that's redundant . . .)
but I'm avoiding resealing it because the 1/4-28 nut plate behind the
bulkhead is just about out of threads and it won't survive another remove/install
cycle. Is there any way to get to it without pulling the wing and end
Well maybe. Remove the actuator, if the bolt goes round and round you
may have to pry it out with a screwdriver. Upon reassembly you may have
to try several things. If the nut plate is secure on its rivets but has
worn threads you can just put the bolt in "very carefully".
(low torque) If the threads are completely gone or the nut plate is missing
you can cut about a 1" hole in the skin right behind the bulkhead
and fish a 1/4" nut or nut plate up and catch it with the bolt. A
nut plate will work if you get the bolt tightened up. Next time it will
be necessary to keep it from rotating, but you can worry about that later!
Or you can remove the whole gear box bulkhead, which is really not too
bad a job. Remove the 8-32 screws at the bottom, the 1/4" bolts on
the sides and drill out the 1/8" rivets across the top, which will
allow you to remove the bulkhead and replace any nut plates or otherwise
return it to original condition. -- Jim
ON THE LOOSE... (080201)
Subj: down lock
From: Ed Clegg <firstname.lastname@example.org>
I was in the wheel wells yesterday, tightening anything that was loose.
I came upon the top bolt on the down lock on the left side that will not
tighten. This bolt goes through into the wing. As I turn the head of it,
it seems like it is tightening, but then it becomes easier for a couple
of turns and then the process begins again. The down lock itself is not
loose so it must be a broken nut plate???? Do you have any suggestions.
How to access? Best way,etc. Thanks for your help. Best Always, Ed Clegg
I presume the nut plate or maybe the nut plate and bolt are worn. A new
bolt may give just enough larger thread diameter so it will tighten up.
(Don't overtighten!) An NAS bolt may be several thousandths bigger than
an AN bolt. Likewise a close tolerance bolt. If this fails, a small (1"or
a little less) hole can be made in the .025 aluminum on the back side
of the gear box bulkhead, in line with the nutplate. Tape a nutplate to
a screwdriver and have a helper turn the bolt while you try to get the
nutplate to engage on the bolt. A slightly longer bolt may be necessary.
Once you get the bolt started in the nutplate you may need the screwdriver
to keep it from turning. To change the original nutplate, the gear and
actuator must be removed, then the 4 or 5 - 1/4" bolts on each end
of the bulkhead, then drill out the row of 1/8" rivets across the
top and remove the 8-32 screws across the bottom. Then the bulkhead can
be removed. -- Jim
From: Ed Clegg <email@example.com>
A question. After flying Sunday I noticed the downlock on the right side
not engaged. But when I went back yesterday it was. I jacked it up and
spayed it with wd-40, cycled the gear and it seems to be getting faster.
Have you seen these stick before and short of pullin it apart is there
some simpler remedy?
That happens where there is an "O" ring with hydraulic fluid
on one side and air on the other side -- the "O" ring hangs
up on the dry shaft. You did the right thing in lubricating it -- 5606
would have been a better lubricant, but they don't supply it in spray
cans to my knowledge! I suppose just a squirt with an oil can would work.
STICKY DOWNLOCK PART II...(040201)
From: Ed Clegg <firstname.lastname@example.org>
Spraying the downlock has helped but it is still slower than it should
be. Am I correct in thinking that hyd press retracts it and it is spring
actuated to the lock pos.? If so could the spring be weak. I ordered a
seal kit from Swift parts but it dose not include a spring. Why are there
two hyd lines to it? Thanks, Ed
Try getting some Vaseline worked in there. Look at the schematic in the
Commings hyd. manual. The spring helps move the piston in one direction.
When fluid under pressure enters thru port "B", the downlock
retracts, compressing the spring and unseats the check ball and allows
pressure to exit port "A" and to the actuator. To get a better
idea of this, study the manual and/or the actual downlock. -- Jim
SLOW TO RETRACT PROBLEM SOLVED... (APRIL 03)
Subject: Re: April #3 GTS Internet Update
Just wanted to tell everyone that my "slow to retract" landing
gear problem is solved! Jim Thomason reckoned that one of my gear actuators
was by-passing, and even though there were no leaks or outside discrepancies
in either gear well, the actuators were suspect to him. Well, he was correct...
and after he overhauled both actuators the landing gear problem is solved.
Thanks, Bill Tiley (N131W).
DOWN & LOCKED... (SEPT 03)
Subj: Down lock "o" rings
From: Grahame Gibson <email@example.com>
I'm hoping this Saturday to pull down the right side gear actuator. This
one has a leaking down lock assembly. The left down lock assembly was
fitted with new "o" rings some years ago and did not require
service when we did the left actuator overhaul. We are doing one side
at a time as we do not have break down drawings, or another swift to view.
Could you please give me the "o" ring MS numbers for the down
lock. I wrote down in the parts book these numbers when I serviced the
left down lock. now I don't understand what I have written, As follows....."o"
rings, 2 x 2.010, 1 x 2.020, od. 3/8" x 1/32" od. 1" x
1/8" Hopefully you can clarify these "o" ring sizes, and
I'll write them up in my parts book for future reference. Kind regards,
Grahame, Australian Swift VH-BYB
Before starting on the downlocks you should have "The Swift Hydraulic
Manual" by WE Commings. The "O" rings in the downlock are
16404-5 (2 ea.) and 16405-15 (1 ea.) I don't know if those a regular AN6227
"O" rings or not. I usually just order seal kit S-148 from Swift
Parts. The actuator "O" rings are AN6227-29, AN6227-14, AN6227-18
and AN6227-27 and the seal kit number is S-147 from Swift. Be sure you
don't lose the little check balls when taking the AN fittings out of the
downlocks. -- Jim