Synopsis of the flight:
1 mile out of the FAF, gear down. Gear motor is running, but no greens and nothing down. Cycled and still no avail after checking circuit breakers. Fly by the tower and no gear. Go to the practice area to 2k and try again with no avail. Manually put them down per the checklist. Two green, Right main and Nose wheel. Left is not down. Per the checklist.. Yaw abruptly still no left main. At this point I'm still pushing the extender down. Do another breaker check and the breaker popped. I push it in and push the extender down again and the left main drops. Fly by to confirm and land on the secondary rwy with no problem.

In the hangar on jacks:
No external power, lift the handle and they come half way up and stop with the gear motor still running. Kill the master. Hook up external power. Turn the master on and they suck up. Put the handle down, gear motor running with nothing dropping. Manually put them down and get three green. Lift them up again, works perfectly. In-transit light is on and then goes off with the three green. Gear handle down, motor is running but nothing is dropping.

So now everything goes up like it should, but will not drop the gear. I cannot mimic the gear getting stuck in manual. All three drop as should.

The motor was an OH'd unit installed in 2010. So I'm leaning toward that. What keeps me up at night is why the left main hung during the manual drop!??

Any help is greatly appreciated as always!

You should have an HYC5005 power pack correct? I'd go to a pressure test and work from there. Well known point of failure/most common aside from micro switch adjustments. If that checks, I'd go to the micro switches, then the condition of the gear bushings.

When is the last time the gear was serviced?

Hi Adam,

your troubleshooting is likely to lead to shopping for a new power pack. If that becomes the case, I can't recall if the arrow is 12V or 24V. If it is 12V you might find that the piper powerpack looks an awful lot like a mercruiser outdrive trim pump that is a fraction of the piper price. They might even look similar right down to the part number that you find underneath the piper decal.

good luck

Correct on the Power Pack PN.

The pump has failed even though I hear it running and operates normally going up? I'm assuming the reverse side is failing?
Def will do the pressure check first.

Nose gear was serviced in Oct 2011
Installed new Micro switch Jan 2011
Installed OH Power pack in Dec 2009

12V. I noticed the boat power packs when searching the web!

yeah the motor can still run, but with enough internal leakage having developed that you don't get there

I used to apprentice with a mechanic that also had a boat business, we were working on a Seneca.... and he says.


Edit for this oldy goldy high drama....
https://www.youtube.com/watch?v=T-_eEYamuNw

Same power pack sans the PMA cert.

As far as the left main gear not extending, I would take a look at the emergency extension spring that pulls the gear into full extension. They are well known for getting "old" and not exerting enough pressure to complete the extension. I found out the same way you did... They are a cheap replacement, relatively speaking.

It's a relatively simple gear system, and the trick is that there are no uplocks. Hydraulic pressure alone keeps them up. In a loss of hydraulic pressure, such as an oil leak, the gear should fall and lock on their own if you're under gear extension speed. The solenoids that feed electricity to the power pack reverses the motor direction and that should cause a shuttle valve in the pump body to allow the reverse flow of pressure, thus extending the gear.

The power pack is a prime suspect, but depending on which PA28 you have, there are various iterations of the automatic extension system, and iterations of a service bulletin that allows for its disablement and another that allows for its restoration. There are a few components involved there that can also cause issues with gear operation.

My experience is that the microswitches are frequently the source of bad indications. For some reason, people can't seem to resist bending the tabs on the switches, which makes them unreliable in the long run, though perhaps seeming to correct whatever problem temporarily.

You may have just had a bad switch which didn't indicate downlock due to slow gear transition from whatever was causing the other issue.

Weak, worn, bent or otherwise questionable downlock springs should be replaced. Also all the various bearings and bushings need looking after. The gear should drop smartly and lock up on jacks when the free-fall (emergency) valve is opened.

If you don't have it, here is a link to the Service Manual. Section 2D3 has a good discussion on how the system works. http://www.mikeg.net/library/files/pa28-service.pdf

So the pump started to kick on and off yesterday in the up position. At the same time the gear was slowly coming out. I yanked the pump out.

Anybody know where I can find an 8130'd HYC-5005 for cheaper than the yahoo's that are charging $1400!!!

It sounds like this is an Oildyne pump like on my Lancair. If that's the case, they have a spool piece with O-rings between the high and low side, and a metal check valve on either end. There are also relief valves that can relieve pressure back to the reservoir. If any of these get worn or contaminated, the pump won't put out pressure. Everything you wanted to know is here: http://www.n91cz.net/Hydraulics/Lancair ... aulics.pdf