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TOPIC: amp meter "bounce" while flying

amp meter "bounce" while flying 5 days 8 hours ago #1286

  • STEVE ELLS
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When there's a small leak in the system (powerpack, actuating cylinders) the pressure in the system bleeds off untll the pressure (sensing) switch mounted on the powerpack closes. This completes an electrical circuit that closes the landing gear motor solenoid, which turns on the pump motor/pump assembly to build the pressure up to 1500 psi.
This “re-charging” is not abnormal but “re-charging”10 to 20 times an hour indicates the leak is larger than desired.
There is a detailed procedure for this problem in the troubleshooting page of Chapter 5 of the airplane service manual. The troubleshooting guide describes the problem as regular “re-charging” of the system and landing gear doors sag open between flights. The manual cites leaks in the door close system as the problem.
If, after walking through the steps in the troubleshooting guide, or if the doors and actuating cylinders have been removed in accordance with an approved modification, the leak may be internally in the power pack or by internal leakage in one or more of the landing gear system actuating cylinders.
The power pack leakage can be a bad thermal relief valve, check valve or check valve o-ring. The parts manual shows where the o-rings for the “self-relieving check valve” and the “thermal relief valve” are located and the part numbers for the o-rings.
If there is still a bleed down, one or more of the main or nose landing gear actuating cylinders has internal leakage. Remove the fluid return lines on each cylinder—fluid dripping out of the return line port when the system if pressurized indicates an internal leak in that cylinder.
Removing, disassembling, repacking and reassembling the cylinders is not difficult but should only be done if your mechanic has the service information about the dimensions of the parts and the equipment to test the cylinders after rebuilding. This information is in the service manual for your airplane.
All work on the hydraulic landing gear system components is very detailed and “clean room” procedures should be followed. Almost all of the rebuild and refurbishment procedures are in chapters 5 and 5A of the service manual.
Good luck and post what you find so we can all benefit from your experience.
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amp meter "bounce" while flying 1 week 2 days ago #1263

  • STEVE ELLS
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Joey;
That is probably the cause of your jumping ammeter. 10 to 20 times per hour is a little excessive. Obviously there's a small leak in the system (powerpack, actuating cylinders) that lessens the pressure in the system untll the pressure switch is closed, which turns on the pump motor/pump to build the pressure up to 1500 psi.
There are a couple of things that can be done to locate the leak.
One of the first things I would do, because it's easy is to change the O-rings in the "self relieving check valve" and the "thermal relief valve" assemblies.
I've attached a drawing to show you where they are.
If this easy trick doesn't do the trick, then it's time to rebuild the main and nose gear actuating cylinders. There are illustrations and a procedure in the service manual that can be used to block off the cylinders one at a time to check for leaks.
Rebuilding them is pretty easy but should only be done if your mechanic has the service information about the dimensions of the parts and the equipment to test the cylinders after rebuilding. This information is in the service manual for your airplane.
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amp meter "bounce" while flying 1 week 3 days ago #1259

  • DOUGLAS VINCENT
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Sorry for delay in replying, but just saw the post.

Problem sounds like when the hydraulic pump runs to pump up the system keep the gear up. May be a little excessive and needs looking into if frequent.

When the needle bounces and goes back to normal do you hear the gear motor running? Mind does to every so often. At first it scared me, but occasional pumping up the gear pressure is normal.
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amp meter "bounce" while flying 8 months 1 day ago #937

  • STEVE ELLS
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Hey Joey;
I'm glad your 210 is running well.
I would start by conducting a good visual inspection of the connections at your alternator. Grab them and try to pull them loose; see if they wiggle. If that's all good, go to the voltage regulator and pull the wiring plug out of the regulator; hit the contacts with some contact cleaner.
Lastly, I would think about buying a new master/alternator switch to replace the one that's installed; especially if it's the original switch.
The original master/alternator switches are not very robust and have been the source or more than one charging system problem

Please let me know what you find
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amp meter "bounce" while flying 8 months 5 days ago #931

I have a 1978 T-210 that fly's great, great temps on the cylinders and very comfortable cruiser. plane has less then 4,000 hours and engine is near TBO but has great oil analysis, and is smooth as a turbine.

i have a issue with my amp meter bouncing every one and a while to discharge for a moment and then goes right back to where it should be. it just happens 10 to 20 times per hour in flight.

has anyone had this type issue? my mechanic finds every thing in working order. this is very concerning especially when flying at night or in IFR conditions.

thanks for any advice.

Joey
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