Hydraulic Help!

J

JackFulford

New member
Well, the wings are back on the old bird (1957 14-19-2) but when we went to perform the retract test, the gear retracts about 20 degrees, the pressure jumps to 900psi, the gear lever goes to neutral and every thing stops. With the gear selector lever in the gear down position, the gear goes into the down and locked position, pressure goes to 900 psi, and handle pops to neutral. I am hoping it is just air in the lines and not the power pack. Does any one know where I can find the procedure (hopefully online) to bleed the lines? Does any one have any thoughts as to what it might be if it is not air in the lines? Diagnostics we have performed so far include:
- Disconnecting the hydraulic cylinders from the gear and cycling the pump. Result: Shafts extend and retract fully
- Disconnect one hydraulic cylinder and leave the other connected. Result: The connected gear retracts about 20 degrees and everything stops.

Any help would be GREATLY appreciated.

Jack
 
The hydro pack bleeds itself. You do not have to bleed the lines. Did you hold the gear lever up until the wheels were in the well as you pump the hand pump? When I had the wings off the crate, I had to cycle the gear about 5 times until all went to normal. If your facing the power pack, the Piper Aztec is basically the same model but has a different pressure. Be sure you have no binds in the trunnions. You should be able to put the gear in the well by hand and then it should drop free into the overcenter position. How about the flaps? Lynn the crate :D
 
Hold the handle in position until the gear goes up, that power pak triggers at too low of a pressure. Watch the pressure gauge, when the lights come on and the gauge jumps up over 1000 you're home. (I think it might have actually gone close to 2000). I had to hold it down when extending too.
 
All,
Thanks for your advice and help. We have made progress but, unfortunately success was not complete. After bleeding both manually and through the method described below here is where we are:
1) With the gear selector in the DOWN position, pumping the emergency handle pushes the gear into the down and locked position. The pressure guage goes to about 900-1000psi and pops into neutral. (Life is good)
2) With the gear selector in the UP position, pumping the emergency handle pulls the gear about 20degrees up, the pressure guage goes to roughly 700-800psi and the selector handle pops into neutral leaving the gear partially retracted. I can feel the tension on the manual pump handle increase as I approach that point.
3) With the gear selector physically held in the UP position, I can pump the gear up. At 20 degrees retract, I can feel the pressure build, the guage goes to 700-800psi but then decreases to roughly 100psi until the gear is fully retracted after which it goes back up to roughly 1000psi. If I perform this same process again, I hit a tough spot at about 20 degrees retract (guage shows 700-800psi), then at 45 degree retraction, the pressure spikes to roughly 950 psi before fully retracting. If I do it a 3rd time, I hit some kind of block at the 45degree point and I can pump the handle no more.
In summary, the pressure valve is popping at 950-1000psi for gear down and 700-800psi for gear up. I am thinking that the pressure relief valve is broken or out of adjustment. What do you guys think? If this is the problem, is there a field fix or does it need to go into the shop?

Thanks,
Jack
 
I ask again, What about the flaps? Sounds to me like you have a bind in the gear system. Did you swing the gear by hand? It should go into the well and then when you let go it should fall and lock into the extended position with no help. Getting the power pack serviced will be a challange. AirParts of Lock Haven (in PA) does power packs. I also assume that the gear was working fine before you removed the wings. If you can consistantly retract the gear by holding up the gear lever while you pump you don't have a problem with the pack.Lynn the crate :?
 
Sorry, I forgot to mention the flaps. They work fine both up and down. re: How it was working prior to removing the wings; this is/was Bill's beautiful green and white -2 N7655B that had the off-airport about a year and a half ago. Concern is that the off-airport and resulting gear collapse may have damaged the power pack. In talking to Dick this morning at Pifer Airmotive who has been "rebuilding these things for the past 30 years", the gear collapse may well have sent a pressure spike through the pack resulting in unseen damage.
Also in talking to Dick, he chastised me big time for using the manual hand pump to work the gear up and down. His position was that the emergency handle was to only be used in emergencies and then only to get the gear down. Retract tests per Dick should only be performed with the use of a hydraulic mule....
Also the gear swing well and freely.

Jack
 
Well Jack, it looks now like the pack needs attention. Since the gear is free the only thing left is the pack. I disagree with not using the hand pump. The Piper Aztec swings the gear on jacks the same as I swing the crate on jacks. It has now been 10 yrs that I have had it. We are growing old together. You do have a very nice plane and GET UR DUN ! Lynn :D
 
Hey Lynn, I think you may be right. I will probably try to send it off tomorrow. BTW I checked Loch Haven and they told me they can only rebuild 750B and don't handle 750N. Does anybody know of a rebuild shop beside Pifer?
 
I doubt there was any crash damage to that unit. The behavior you're describing is exactly the way it behaved before the crash.
During my checkout ride, the previous owner was quite specific in that you had to hold the gear selector in position until the gear reached it's intended position. Not knowing any better at the time, that's what I did. You can imagine my surprise when I first flew the -3 I have now when I discovered the way it was *supposed* to behave.
SInce the gear departed the plane sideways, I also doubt any "spike" was sent back to the control unit.
The previous owners (there were actually 2 guys that owned the plane during the time it was being restored) sent that unit back to Dick for rework before they flew the plane. They too thought you had to hold the handle in position - they didn't have any other intel to tell them otherwise.
Next time you talk to him, ask him exactly how you're supposed to connect a mule to the plane. I'd be very interested it what he has to say about that.
 
Hi all,
Problem appears to be solved! When the power pack was removed from the plane, my buddy noticed that a bolt was missing from one of the adjustment screw hold downs. Replaced the bolt, re- installed and now works like a champ. Pix attached.
Jack
 
Over exuberent optimism. Subsequent tests gave inconsistent results. Must be more wrong than originally expected. Pulled the power pack out today and sending it to Pifer tomorrow.
 
Thought I would keep everyone posted. Dick Pifer called and essentially told me my power pack was trashed. We had to provide a replacement dome and base I am still looking at a roughly $3,000 bill. Per Pifer, the previous overhauler welded the dome which is not legal and over bored the case by 10 thousands and replaced the cams with custom made oversized cams. He also said the high-pressure check valve was missing, all poppets need to be replaced, and replace cams. The bolts that were used to attach the power pack to the mounting plate were too long and stripped out the threads in the bottom of the base. Pifer had already put in the new helicoils before he found out the base was not serviceable. And the saga continues....

Jack
 
Jack, I just noticed a power pack listed on Ebay under Bellanca for $1,200 buy it now price. I hope this helps.
 
Hi all,
The power pack listed on eBay is electric for a Viking 17-30. Is there an STC or a group of approved 337's to put this in a 14-19-2?
 
..."Is there an STC or a group of approved 337's"...

There are none. It would be more trouble than it's worth to try to get that one approved... What you're doing is probably the best path towards success..

the power pak and Hartzell prop AD are the banes of owning a Bellanca, at least there's a solution to most of the prop issues (at least on -2s).
There's a 3a at my homefield that's a derelict but has a perfectly good landing gear system. I'm working on aquiring it just to get the good stuff out of it. They keep putting it up for auction calling it a Viking :)
 
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