vance atkinson
Member
On my last flight my Trio autopilot with NavAid servo got the jitters.
Trio was nice enough to talk with me about the problem but pretty much determined the head was not the problem as all the test readings were good.
A week later, I was able to come up with another low time NavAid Servo (250 hours) to check against mine, and noticed the servo arm on the almost new one, rotated to its limits a LOT smoother and not as nearly as hard to move as mine.
So I took The little critter home and examined all the gears and gizmos and wound up taking a middle gear out thus creating two separate gear trains independent of each other. The servo arm became smoother. I then ran an entire rattle-can of brake cleaner through it and a LOT of dark liquid and Itty-bitty bits of junk came out. When nothing but clear was streaming out the other end I stopped and examined every thing again. The servo arm became even smoother. I put the gear back in that I took out.
I then took some very fine lubricating oil and carefully put tiny amounts on the bearings and shafts that contacted the gears.
Viola' Now the arm REALLY moved silky-smooth. You can hold the servo up by its side and the arm will almost rotate downward on its own weight. Re-installed the unit in the plane, and NO jitters.
So guys, clean the servo more often. Mine has never been cleaned or apart for 25 years. I bought the NavAid new in June of 1992. So if you have a servo with unknown history. Look on the bottom of it. There will be a number stamped on it and mine is 312 .....that will give you an idea how old it is.
Vance Atkinson
Trio was nice enough to talk with me about the problem but pretty much determined the head was not the problem as all the test readings were good.
A week later, I was able to come up with another low time NavAid Servo (250 hours) to check against mine, and noticed the servo arm on the almost new one, rotated to its limits a LOT smoother and not as nearly as hard to move as mine.
So I took The little critter home and examined all the gears and gizmos and wound up taking a middle gear out thus creating two separate gear trains independent of each other. The servo arm became smoother. I then ran an entire rattle-can of brake cleaner through it and a LOT of dark liquid and Itty-bitty bits of junk came out. When nothing but clear was streaming out the other end I stopped and examined every thing again. The servo arm became even smoother. I put the gear back in that I took out.
I then took some very fine lubricating oil and carefully put tiny amounts on the bearings and shafts that contacted the gears.
Viola' Now the arm REALLY moved silky-smooth. You can hold the servo up by its side and the arm will almost rotate downward on its own weight. Re-installed the unit in the plane, and NO jitters.
So guys, clean the servo more often. Mine has never been cleaned or apart for 25 years. I bought the NavAid new in June of 1992. So if you have a servo with unknown history. Look on the bottom of it. There will be a number stamped on it and mine is 312 .....that will give you an idea how old it is.
Vance Atkinson
