landing gear transition on takeoff
 

I have my plane being looked at right now for a landing gear issue, but so far they haven't figure out anything. I thought I would post the symptoms, and get extra input on possible items or see if others have had and solved a similar issue.

On landing, the gear transitions down fine, locks into place, and the handle kicks back to the neutral position.

On take-off, the gear appears to transition up, but the handle never kicks back down to neutral. I put it back into neutral on my own, after waiting about 30 seconds or so for it - so that the pump didn't keep pressurzing the system and maybe causing me not to have enough fluid for it to tranition down when it came time to land. Tower calls and says that it looks like th gear doors didn't fully close. I try putting it up again, and then wait 30 seconds to a minute and put it back into neutral on my own (because it does not kick down). Same comments from tower. I put it in the down position, and it tranistions down and locks into place with no issue, handle kicks back to neutral. I put it up again, and this time the handle kicks back to neutral on its own, tower says it all looks good on flyby, and I'm on my way.

This has happened a couple of times recently. Topping off the hydraulic fluid doesn't reflect anything unusual in terms of amount.

Mechanic has it up on jacks now, and using hand pump to pressurize (they don't have mule). Says it transitions properly in both directions.


I am going to replace all the hydraulic hoses, just because they are really old.

Any suggestions, thoughts, or comments?

-robert
rmorris@agsi.us
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BUY GLASS BONG

Mine did the exact same thing. The microswitch on the power pack had a small crack in it. I changed that and it solved the problem. The switch is only about 15 dollars from Cessna.

Had the same exact problem, cleaning and adjusting the up lock switch on each of the main gear cured it, and the problem has gone away.

Buy some electronic cleaner in a spay can (it's like brake cleaner, only you can use it on electronics). Pump the doors open and spray all of your door switches and locks. Then blow them off with air. That should more than likely fix it. I am however surprised that you have to ask the tower if your doors are closed. You should instal a mirror or two so you can always be sure. Good Luck

Let's see, the aircraft in question is a 1968? Is that correct Robert? Tony, are you referring to the electric power pack? The 68 is gear pump on the accessory case of the front engine. Just to keep things straight let's make sure which aircraft model we are troubleshooting. It sounds like the main gear switches are not functioning properly or have a short, crack, etc. That's usually the case as Hank pointed out.

I would not use the E pump for the testing while on jacks. The E pump is not for continuous use. I agree that it is a good idea to at least lower the gear once in a while with the E pump but retracting it will not give you the same operation as the gear driven pump on the engine. You don't need a mule to do this function. Contact Owen Bell and he has a socket bit that is the female to the gear pump. Simply remove the pump from the front engine and use an electric powered drill to transition the gear. It works great. And you will own the tool for the rest of the time to swing your gear for each annual. It's well worth the money.

See my video on you tube http://www.337skymaster.com/messages...ead.php?t=2656

I'm referring to the switch on the hydraulic power pack.

Here's a pic from the 1965-1969 parts catalog. The switch I'm referring to is #16.

2200 later and still not working
 

First, Herb - wish i had seen your post a couple of days back - I would have easily bought one from owen, or paid to rent yours. I was leery the entire time of them using the hand pump,

In any case, they t-shot (17 hrs of charged labor) and said it was a leaking door actuator, two leaking hoses, and a leak around the hand pump. OK, fix em all I said, but please remember that I have to fly out on Sunday Oct 5 for my yearly trip to NM - small window to go, so need plane ready (said this to them a week and half ago when i made original post).

OK, parts came in yesterday, they 'notified' me the plane was ready by sending the invoice via email around 4 yesterday. I went out to test fly it today at noon. same problem - landed and mechanic said I needed to cycle the gear a few more times, might be an air bublle, so up in the air I go again. cycle a bunch of times, same issue. land, line guy pushes it back into maint hangar, sole mechanic sits in a nother airplane 'buttoning it up' for the next hour and half - despite my pleas to make sure my plane is fixed. Fianlly comes over about 4:20 and looks, then goes in offices to look at schematics, then comes out again. i keep metnioning the switches, per above posts - as I had previous week when I saw the posts. He cleaned off the main up switches, and slightly adjusted the nose up switch and cleaned it off, and told me to go fly it again to see. I did, and then he closed the doors and left while I was in the air 9needless to say the problem still exists). Charlotte Monroe Air Center, Neil is the mechanic and owner Mike Dickery aslo aware of situation, in case you all think they should be rewarded for this stellar customer service attitude.

at this point, the problem still exists, and my daughter is waiting in Atlanta for me to pick her up and fly out to NM for my whopping 5-day vacation. Told the main facility would be closed Monday for Labor Day.

So, they have my check for $200, which is mostly labor, and my problem still exists, and no way to get it fixed and make my trip that I can see.

Good news, tried topping it off again after the 30 or so cycles during 3 test flights, and it is still full - so the leaks are fixed :)

he did say they cycled it with the hand pump on the jacks and it worked fine in both directions.

At least if it is failing, it is in the up cycle, not down - thatt's the bright spot.

-Robert
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Iolite vaporizer

As I mentioned before, just go buy some electric cleaner and spray the switches yourself. Blow them off with air.

I don't know this for a fact but I have always felt that the reason the doors might close on jacks vs in the air, is because in flight when the doors are open they probably create a bit of a vacuum in the area of the gear bays.

This negative pressure could be drawing the gear back out/down and away from the locks util the doors are closed. Of course if the gear doesn't seat well enough to activate the switches, the doors will never close, therein aggravating the problem.

Just a thought on why it may only happen in the air.

switches cleaned
 

I had him clean the switches today, don't think he used electrical cleaner but some sort of solvent, then saw him blow them off and check with an ohmeter. said the switches were fine, but I went back and test flew - same symptom.

So, not sure it's not the switches, but don't think so on the door switches (mains and nose). He visually examind the microswitch on the powerpack last week, but not sure he did much else on that one - my money is there, since it seems to match previous posts as a culprit, and one of the few things not touched yet.
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Medical marijuana patients

When you cycle the gear to the up or down position are you getting a gear light indication. If you are getting a light but your handle is not returning to neutral it is the switch on the power pack. If your not getting a gear light indication it's probably a gear switch. When I visually inspected the switch on my hydraulic power pack it looked fine but after I took it off it was clearly cracked. A temporary fix I used was to just spray it with contact cleaner. Gently tapping the power pack with the toe of my boot worked too.

Light
 

The gear up light does not show on until the handle returns to the neutral position. It does this when I manually move the handle back to neutral, since it does not kick down on it's own. Gear down light works fine when it locks down in place.

I will buy some electrical contact cleaner tomorrow at auto zone, along with compressed air, and try the clean and dry again and go fly it. Will post results.
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Zoloft Prilosec Nexium

update
 

OK, went by autozone and bought electrical contact cleaner, then by CVS to get compressed air

Cleaned off all three door uplock switches (2 main, + nose). Nose one is kinda hard to find at first, located behind strut in the tunnel area. Cleaned off the microswitch on powerpack, plus any other electrical connections I could find under panel (hey, I was there anyway).

Flew the plane and the same issue. Then tried to see if the hand pump would close the doors in the air, and it does !

So, the symptoms appear to be this - gear down, no issues with gear coming down, locking place, and doors closing, get green light, all is good.
gear up, doors open, gear goes up and locks into place, doors close, up light comes on for a couple of seconds then extinguishes and handle does not kick back to neutral. You can manually move the handle back to neutral (and light comes on), and the gear doors open up slightly (kind of like in one of herb's videos). If you leave it in neutral but use hand pump you can feel it pump easy for a few strokes and then get stiff, a flyby confirms that the gear doors did go up and are staying in place.

I got back on ground after many cycles of replicating above, and cleaned again, then repeated above - everything consistent. At least I can now put up my gear and shut my doors (using hand pump) and fly to a better mechanic.

If anyone has thoughts, please feel free to share.

In any case, I will post again once I figure out resolution.
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003

You might check that the nose strut is properly serviced. Since the strut retracts forward the aero load on the strut will collapse the strut a small amount if not serviced properly and cause a problem with the uplock switch.

Gear problem
 

Start thinking about the engine driven pump.

Had very similar problems. All symptoms same as yours. Only think different was that I am not so brave to keep bringing the gear up and down like that. Like you, we started with the actuators, which were leaking and in desperate need of rebuild. After spending lots of money on that, and everything testing fine with the hand pump, we still had the same problem in the air. With no other alternative, my mechanic took off the engine driven pump. It was scrap metal, amazing it worked at all. It built enough pressure to drop the gear, but not enough to reliably bring it back up and close the gear doors. Got a rebuilt, changed the screen (screen was clogged with molten bits of the pump) and now it is fine.

Of course, there is always more to the story than what I can post here. In fact, my problem featured prominently in Don Nieser's presentation about O-2 maintenance at Oshkosh this year.

Long term under carriage problem
 

Hi all I would like to explain a problem and after sometime how I over come this
Problem.
My undercarriage would retract up light would come on for moment then off. Rear doors would be partially open.
Would check fluid level and might be bit low, top up and bleed system. All would be well for a while then same thing this went on and off for couple of years. But each time we jacked plane and tested all worked fine.
The problem turned out to be the left rear up switch not adjusted correctly but close enough that if you tested it it would mega as a closed switch.
Only in flight would the switch not close and only occasionally.
Hope this helps anyone with similar problem in the future.

Possible explanation - squirt your uplocks
 

It has been decades, but....

The doors will not close until all the uplock micro switches are all closed (wired in series),
which also turns the UPLOCK light ON.

This makes sure everything cycles in sequence correctly
and prevents doors from closing while gear still in transit (or not all the way up).

As I recall,
that uplock light circuit also allows the system to pressurize to 1200-1500 PSI.
When it hits that pressure limit it pops the gear handle down.
The handle goes down, the system at rest,
and all is well in the land....

In your case
the the gear comes up,
the uplocks close UNDER PRESSURE (but not solidly!!!),
the microswitches are closed (under UP CYCLE pressure)
the uplock light comes on (briefly),
your doors close,
then the light goes off
but the down handle never occurs.

I would bet a nice doughnut against a dollar your uplocks not solidly going 'CLICK'

So under UP-CYCLE pressure they the uplocks in position
CAN AND DO close the microswitches,
but wont keep the switches closed without the UP CYCLE pressure.

So the final pressurization needed to pop the handle never occurs.

-------

ANSWER #1: Check /squirt get to know your uplocks.

ANSWER #2: If the system cannot hit the 1200-1500 PSI to shut off,
it wont lock the system UP correctly.

Yes, a leak or air will do this.
ON THE GROUND, try cycling the gear DOWN CYCLE position.
If system can hold pressure it will pop the gear handle 'up'
from DOWN-CYCLE to the DOWN LOCKED position.
No leaks.

The system is 'self-burping' so a bunch of cycles will burp out the air.

I will accept any decent chocolate-covered doughnut as reward.

EXTRA CREDIT

I have replaced those little beasts with tiny screw in 24 volts LEDs
Nice, cool, will never burn out (again).

D

So, having flown only the "G," what model did the gear handle stop reacting to system sequencing? The "G" is easy, up/down, nothing moving or in-between.

Need to know what model you are dealing with here please

The original Skymaster thru model F had a mechanical gear handle that actuated the system
When Cessna built the G (1973) model it was changed to an electric motor to operate the hydraulic pump, therefore now the gear handle is just a mouse click