Thought I would see if there is any insight here regarding a problem were having with a 68' Arrow 180hp. Long, long story shorter...

After airplane was landed on freeway a number of years ago and was purchased by our company as salvage, it has been put back together and runs strong with everything else seeming to work besides the gear not wanting to come up fully. After a few tests flights noticed some things starting to play out with the ammeter and volt meter. Basically it seems as high rpm is applied it trips the system, so from take off right away it trips.

We have replaced the over voltage and the regulator, the circuit breaker and bench tested the alternator. One of our A&P's said the alternator checked out fine on the bench. We have had it up on stands and previously had the gear coming up and locking multiple times in a row. Then test flown without success. First we need to fix the electrical issue, thinking this is tied to why the gear wont come up and lock but at the same time it has came up multiple times on the stands without the engine running...I would think that with a full charge on the system even with it having an over voltage issue that the gear would still come up and lock at least once if not a few times.

So two separate issues but thinking the electrical issue is behind it not allowing enough current to drive the pump to pull the gear up and lock?

Ideas from here pleassssse? The owner is about to light the thing on fire

Thanks

Doesn't come up fully or doesn't come up at all? When new these had a auto gear extension you had to over ride if low thrust or airspeed. May be miss adjusted if still operational. Could also be air loads on the nose gear doors overloading the gear motor.

Tim

bat443 wrote:Doesn't come up fully or doesn't come up at all? When new these had a auto gear extension you had to over ride if low thrust or airspeed. May be miss adjusted if still operational. Could also be air loads on the nose gear doors overloading the gear motor.

Tim

Doesn't come up fully. On the stands it was inconsistent at first. Then they were swinging and coming up as they should. The battery is basically brand new as well. On the stands you have to put the throttle forward and hold the gear over-ride up until it locks up. We have tried slowing the airplane down a bit as well no change.

We want to make sure we have the electrical on lock before assuming the gear has issues but it seems as though its tied together some way. We swapped the pump on the power pack with another as well making sure it wasn't that. Maybe could be an alternator issue after all we were thinking end of today because it was showing up around 16v on the volt meter at one point taxing back, which doesn't make sense because of the over voltage before it to me..

Is it tripping the C/B? If so, is it only when the gear is in transit or is it anytime the RPM is up?

This may not be pertinent and it's been many years since I taught in Arrows, but iirc, the gear never locks up. It's simply held up by hydraulic pressure. As the gear retracted, once it hit the up limit stops, the pressure would spike, and at some number (1900 psi or something similar) the pump shuts off. If there was a slow leak, it would occasionally run the motor for a split second until the pressure was back up, and the pump would again shut off.

If the pressure switches were screwed up, it could wreak havoc with the system, but generally they were pretty reliable.

On gear extension, the pump ran until all three gear were down and locked (they DO lock down) and the pump shuts off - no residual pressure required.

Also, if you need to hold the override, it sounds like the 'magic hand' system is still functional. It was disabled on all of our aircraft because it made engine out situations more complicated - the gear would automatically extend well above best glide speed. That kinda defeated the purpose of going to best glide.

Cannon wrote:Is it tripping the C/B? If so, is it only when the gear is in transit or is it anytime the RPM is up?

This may not be pertinent and it's been many years since I taught in Arrows, but iirc, the gear never locks up. It's simply held up by hydraulic pressure. As the gear retracted, once it hit the up limit stops, the pressure would spike, and at some number (1900 psi or something similar) the pump shuts off. If there was a slow leak, it would occasionally run the motor for a split second until the pressure was back up, and the pump would again shut off.

If the pressure switches were screwed up, it could wreak havoc with the system, but generally they were pretty reliable.

On gear extension, the pump ran until all three gear were down and locked (they DO lock down) and the pump shuts off - no residual pressure required.

Also, if you need to hold the override, it sounds like the 'magic hand' system is still functional. It was disabled on all of our aircraft because it made engine out situations more complicated - the gear would automatically extend well above best glide speed. That kinda defeated the purpose of going to best glide.

It does trip the gen field CB eventually every time. At this point it seems to be full throttle, trips the system but the CB doesn't pop right away, try the gear and by downwind the CB pops. If you push it back in and rest the master it will all come back online again but the gear wont come up and will eventually pop again.

You are correct as it is just help up by pressure and the pump stops running. It is sounding more and more like a pressure switch issue coupled with an electrical issue as well to me.

One thing to consider on the electrical front is the master switch. I don't remember all the details, but I remember reading in the piper owners association book (I think that's what it was, it was a while ago... It was a compilation of letters about maintenance issues) that the master switch (the alternator side) would slowly degrade, and increase in resistance. This would cause weird problems with the alternator regulation, and they would go away when the alternator was on the bench. The good news is that it's easy to verify, and cheap to replace.

I would consider all grounds/bonding on the engine, airframe and pump circuit. The vibration when flying maybe causing a poor ground that does not show up in the hanger. Many electrical problems are traced to a bad ground in my experience.

The other possibility is a damaged part in the retraction system that is binding when the added air pressure while flying is putting on different components. Could there be a bad hinge/bearing, bent cylinder, broken bushing, thrust washer missing during repair, bent doors etc. I am not familiar with your specific model but I would look closely at all the mechanical parts and verify they are correct.

Is there any way to put a pressure gage on the pump to see what pressure is being delivered before the circuit breaker trips? If the pressure climbs above the maximum working pressure then I would think it would start to heat up the motor and trip the circuit breaker. The fact the breaker trips indicated a problem with the pump, either electrical or hydraulically, IMO.