Power Pack

G

gzlf3p

New member
Since I have owned the plane (14-19) I have had to add oil to the hydraulic system. Every preflight I have one of three situations. One time I have oil spouting out of the plug on top reservoir, on top of the engine, an other time I need to add about a half-pint. Other times the oil level is fine.
The theory I have is, air is getting into the system and settling in the bottom reservoir.
Everyone tells me that can’t happen. Sunday I tried to go for a ride in my old 6558N and guess what, I can’t get the flaps to extend. The manual pump feels like, no oil. There was oil in it Saturday, because I did a preflight and a startup and it was fine then. When I checked the top reservoir oil started to come out from around the threads.
Now I do believe there must be air in the manual pump.
Obvious question how do I stop this?
 
I know to well of what you speak. Our aircraft is N6RJ 14-19 S/N 2062

The first order of business is to thourghly inspect the whole system for leaks. Gear retract cylinders, flap cylinder, all associated lines and hoses and the reservior under the seat, leaking might be at the hand pump or anywhere on the pack. I just replaced a section of tubing under the instrument panel that had a whole chaffed in it from a scat hose, this was in the return line. I would put the aircraft up on jacks. With no leaks anywhere in the system the reservior under the seat should be filled first, then the tank on the engine should be filled half full. I would then cycle the gear a number of times with the hand pump as well as the flaps. During one of these cycles with the gear up I would inspect the retract cylinders to see if they are leaking, pressure is the only thing that holds it up, this is also a good time to look at the hoses that are attached to the cylinders. With the bird on the jacks this is also the time to check the free fall of the gear without using the hand pump. Push the gear handle down and the gear should free fall down and locked. If you have the system overserviced it will be apparent during this test as fluid will come out of the reservior on the engine. It is also a good idea to check the drain on the hydraulic pump to see if the pump is leaking the fluid.

I would also check the outlet fitting on the engine tank,as well as the inlet fitting. These fittings were originally AC fittings with a 45 degree flare, and somewhere down the road the inlet fitting was changed to an AN, but the outlet fitting with the screen was not, and the hoses were replaced at sometime which had the AN fittings with the 37 degree flares. Now trying to mate a 45 degree fitting to a 37 degree fitting is going to cause problems.The outlet line is not under pressure but could be a possible source of air being sucked into the system if it is still the AC fitting connected to an AN fitting on the hose. I changed the tank outlet fitting to a current AN fitting and modified it to accept the screen.

With no leakes in the system you should not have to add any fluid.

Dan
 
Dan:

Thanks for the quick response. You have given me some things to look for.
I will need to make some jacks to do the tests then do the tests then I could let you know what I find.

Jerry c.
 
I'd pay special attention to the "1/2 full" comment. The reservoir fills as the gear is retracted. Good luck!
 
Oops - I can't verify my last statement on this plane. Wish I could have checked that out yesterday when I was on jacks. - Glenn
 
It don't change up or down it stays where it is UNLESS there is a leak in the system. The power pack is like the Piper Aztec but at a different pressure, The Aztec svc and parts manual have a pretty detailed description of what it does and how it works with pictures ie: Principles of Operation. Sent this to Russell to fix JB's power pack problem. Still working on wings got them half epoxyed and flipped then the stinkin Pissburgh weather returned! 100% humid cold and rain (Seattle Sunshine)Lynn :evil: :x
 
It sounds like your 14-19 uses the same Electrol power pack as does the 14-19-2 and the Apache.

It sounds to me like you may have some O-rings giving up the ghost in the power pack. As mentioned by another, hyd pressure holds the gear up in lock position. Your description of fluid backing up in the upper res does sound like a seal problem. Can you determine whether or not the LG is bleeding down when in flight. Or better yet, check for this happening when you get her up on jacks. Years ago in my -2 I had a leak down problem. Burbank tower told me that my gear was not retracting all the way. I landed and checked and found a leak. I had a medical team on board with a trip to Baja. So I put the gear down, and made the trip that way.

There are a whole hand full of O-rings in that poewer pack. I've overhauled the one I had in 9801B 14-19-2 and the one I now have in my Geronimo. It is not too hard to change all the seals in the pack. Just don't screw around with the pop off valves or the temp relief valve settings. The push-pull rod-valves have several rings on each one. Be sure to use vasoline or Parker O-lube when pushing them back into the power pack body. I had the main lower resavoir seal to go out a few years ago. It's a large diameter but a small width. If you can't find one you can make one from several kits found on the market. They furnish a long string of material, you cut it and glue it together with Super Glue.

I actually bench tested it after replacing all the seals. I bolted it to a bench, connected hyd gauges to the ports and checked for proper relief pressures. You don't need flow to do that.

That power pack is a pretty good system. The main reservoir has a stand pipe that keeps you from totally loosing all the fluid. In normal use of the system the valves get their fluid from the stand pipe. If you have a leak outside the system there will be enough fluid in the main reservoir to allow you to pump down the gear, because the hand pump gets it's fluid from below the stand pipe. That is not a for-certain senario though, depends on where the leak is that lost all your fluid.

Hope this helps.
 
Actually, the 14-19's original power pack was the Electrol 750B, not the 750N used on the -2 and onward. This is one - and perhaps only - mechanical fact I know well.

No one is overhauling the Bs any longer. No one has, or in some cases will admit to having, the overhaul manual for that pack. The later one, originally created for the Navion (B for Bellanca, N for Navion, P for Piper, etc) is indeed similar to the one on the Apache, though its orientation is different. You can get the N overhauled. Naturally you'd want to try the stuff others have suggested first before you think about switching to the later pack, as the switch is not trivial as the mounting plates and some other installation bits are different and you'd probably need to fabricate them. Getting field approvals could prove a problem. Most have gone with logbook entries for the switch.

If you have the original Lycoming O-435A the engine driven hydraulic pump can also be the source of some woe, and it too is difficult to overhaul or replace. Its engine fitting is non-standard.

All this means that I hope your problem lay elsewhere. I've not been as lucky, and I did not fully appreciate what owning an airplane with an orphaned engine could mean, even though it's a Lycoming. This is precisely the reason why soooooo many 14-19 owners swapped out the original engine for the O-470 Continental used on the -2.

Jonathan
 
I talked to Piefer's a couple months back and they said that they could still overhaul the 750B units, I believe the quote was 1400.00. 800-878-0909.

Dan
 
The air in the power pack has gotten so bad that I can only half extend the flaps.
I can still pump up the landing gear to get down and locked, but I don't dare fold up the wheels, they may not unfold.
So can I remove the power pack and reinstall it after rebuild and enter all of this in the airframe log as the owner or do I need an IA.
 
My reading is a mechanic must approve the aircraft for return to service because:

FAR 43 States - A person holding at least a private pilot certificate may approve an aircraft for return to service after performing preventive maintenance
However, The holder of a mechanic certificate may perform maintenance, preventive maintenance, and alterations as provided in Part 65 of this chapter.

A pilot may perform the folowing:
(c) Preventive maintenance. Preventive maintenance is limited to the following work, provided it does not involve complex assembly operations:

(1) Removal, installation, and repair of landing gear tires.

(2) Replacing elastic shock absorber cords on landing gear.

(3) Servicing landing gear shock struts by adding oil, air, or both.

(4) Servicing landing gear wheel bearings, such as cleaning and greasing.

(5) Replacing defective safety wiring or cotter keys.

(6) Lubrication not requiring disassembly other than removal of nonstructural items such as cover plates, cowlings, and fairings.

(7) Making simple fabric patches not requiring rib stitching or the removal of structural parts or control surfaces. In the case of balloons, the making of small fabric repairs to envelopes (as defined in, and in accordance with, the balloon manufacturers' instructions) not requiring load tape repair or replacement.

(8) Replenishing hydraulic fluid in the hydraulic reservoir.

(9) Refinishing decorative coating of fuselage, balloon baskets, wings tail group surfaces (excluding balanced control surfaces), fairings, cowlings, landing gear, cabin, or cockpit interior when removal or disassembly of any primary structure or operating system is not required.

(10) Applying preservative or protective material to components where no disassembly of any primary structure or operating system is involved and where such coating is not prohibited or is not contrary to good practices.

(11) Repairing upholstery and decorative furnishings of the cabin, cockpit, or balloon basket interior when the repairing does not require disassembly of any primary structure or operating system or interfere with an operating system or affect the primary structure of the aircraft.

(12) Making small simple repairs to fairings, nonstructural cover plates, cowlings, and small patches and reinforcements not changing the contour so as to interfere with proper air flow.

(13) Replacing side windows where that work does not interfere with the structure or any operating system such as controls, electrical equipment, etc.

(14) Replacing safety belts.

(15) Replacing seats or seat parts with replacement parts approved for the aircraft, not involving disassembly of any primary structure or operating system.

(16) Trouble shooting and repairing broken circuits in landing light wiring circuits.

(17) Replacing bulbs, reflectors, and lenses of position and landing lights.

(18) Replacing wheels and skis where no weight and balance computation is involved.

(19) Replacing any cowling not requiring removal of the propeller or disconnection of flight controls.

(20) Replacing or cleaning spark plugs and setting of spark plug gap clearance.

(21) Replacing any hose connection except hydraulic connections.

(22) Replacing prefabricated fuel lines.

(23) Cleaning or replacing fuel and oil strainers or filter elements.

(24) Replacing and servicing batteries.

(25) Cleaning of balloon burner pilot and main nozzles in accordance with the balloon manufacturer's instructions.

(26) Replacement or adjustment of nonstructural standard fasteners incidental to operations.

(27) The interchange of balloon baskets and burners on envelopes when the basket or burner is designated as interchangeable in the balloon type certificate data and the baskets and burners are specifically designed for quick removal and installation.

(28) The installations of anti-misfueling devices to reduce the diameter of fuel tank filler openings provided the specific device has been made a part of the aircraft type certificiate data by the aircraft manufacturer, the aircraft manufacturer has provided FAA-approved instructions for installation of the specific device, and installation does not involve the disassembly of the existing tank filler opening.

(29) Removing, checking, and replacing magnetic chip detectors.

(30) The inspection and maintenance tasks prescribed and specifically identified as preventive maintenance in a primary category aircraft type certificate or supplemental type certificate holder's approved special inspection and preventive maintenance program when accomplished on a primary category aircraft provided:

(i) They are performed by the holder of at least a private pilot certificate issued under part 61 who is the registered owner (including co-owners) of the affected aircraft and who holds a certificate of competency for the affected aircraft (1) issued by a school approved under §147.21(e) of this chapter; (2) issued by the holder of the production certificate for that primary category aircraft that has a special training program approved under §21.24 of this subchapter; or (3) issued by another entity that has a course approved by the Administrator; and

(ii) The inspections and maintenance tasks are performed in accordance with instructions contained by the special inspection and preventive maintenance program approved as part of the aircraft's type design or supplemental type design.

(31) Removing and replacing self-contained, front instrument panel-mounted navigation and communication devices that employ tray-mounted connectors that connect the unit when the unit is installed into the instrument panel, (excluding automatic flight control systems, transponders, and microwave frequency distance measuring equipment (DME)). The approved unit must be designed to be readily and repeatedly removed and replaced, and pertinent instructions must be provided. Prior to the unit's intended use, and operational check must be performed in accordance with the applicable sections of part 91 of this chapter.

(32) Updating self-contained, front instrument panel-mounted Air Traffic Control (ATC) navigational software data bases (excluding those of automatic flight control systems, transponders, and microwave frequency distance measuring equipment (DME)) provided no disassembly of the unit is required and pertinent instructions are provided. Prior to the unit's intended use, an operational check must be performed in accordance with applicable sections of part 91 of this chapter.
 
Well I guess your telling me the removal and reinstallation of a rebuilt power pack is not an owner allowed chore.
Back to the IA.
 
You can do whatever you want, just don't log it. Like history it didn't happen unless written or photographed. Get the Aztec service /parts section of the powerpack and it works only on a different pressure the layout and parts are the same. Not rocket science more just common sense. If your unsure of yourself and most of us are ,use a digital camera to help you along. Worked for me and I'm encouraging you to give it a go. Lynn :mrgreen:
 
No Iw. I can’t just replace O-rings gaskets and seals, and put it back together just as I find it. Remember I am the guy that has been getting air in the hydraulic system since it was new.
 
Lynn - It seems that air would have to get in the system on the return side of the pump. I'd check for leaks carefully there? Seems the power pack should be under pressure keeping air from getting into it. I see where the power pack could leak fluid internally causing pressure losses, but that should not cause air to get into the system. What don't I understand?
 
Having recently just done JB's entire system I found the same problem with a system that has a 14-19-2 pack, stock factory engine-side reservoir, and an updated version of the 14-19 Easton gear-style hydraulic pump on the engine (my 14-19-2 has a stratopower swash-plate piston pump, but that won't fit onto the O-435's funky drive pad). I know it isn't leaking and all the tubing, hoses and fittings are new and have been pressure tested.

When I started it I originally filled the lower pack dome, then filled half-full on the upper reservoir. After running and shutdown, and after enough cycles to bleed the air out of the actuators and lines, the upper res was burping out fluid after each run. The fluid overflow stabilized and stopped after the lower pack emptied out to the standpipe level of fluid, so it has a nice air bubble in the lower dome.

The culprit is that I think the pump is sucking air with the upper res half-full, and of course the air bubbles are making the system run very slowly, groan loudly, and have air in the gear cylinders so they pop out of overcenter several hours after shutdown. There's nothing more confidence-inspiring in passengers than to turn on the master switch and have the gear alarm phone-ringer mechanical bell go off (hello? hello?). I think this may have something to do with the gear style pump having more flow than the piston pump. The only solution I can see to this is to try a bigger, deeper upper res so that it will have some capacity to cover the upper pump inlet even with higher flow rates swirling the fluid around.

My 14-19-2 doesn't have any problems with air intake or fluid overflow. Super-reliable.

Replacing O-rings in a 14-19-2 pack isn't a big deal as has been pointed out. Just make sure to carefully keep track of the parts, there are many balls, springs, plungers and miscellaneous parts waiting to spring out and hurl themselves into oblivion as you take it apart. It is almost as bad as working on an automatic transmission. I have a few pictures of what the inside looks like (this one coated with grime, pre-cleanup):

750n_pack_xsmall.jpg


The standpipe is on the right, the tall thing on the left is the thermal relief valve assembly. Each of the "posts" on the sides are relief valves for the outlets. The valve bodies run fore-aft as long "sticks" that have profiled cam surfaces to run spring loaded valve plungers that are placed vertically underneath the two roughly semi-circular plates.
 
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