The Day the Trim Died
Updated: Dec 21, 2020
9/6/19 - Once again the weather consisted of far too many clouds. The coast was completely covered so Forks, my first choice was out. The clouds increased to the south so going too far afield was out. There were towering cumulus over the cascades, and it was in the 90s east of the mountains, so that direction was out. That left north or near south. We considered Orcas Island, but the temperature was higher than usual and very humid so the walk into and from town would have been pretty uncomfortable.
The ceiling at Chehalis was only 2,100', but it was mostly clear north of that so we thought we could make it in, also it was supposed to be improving as the day wore on. We decided to try for Chehalis and if that didn't work we would back track to Orcas.
Departing Arlington and climbing to cruise altitude was relatively uneventful, if a little warm. Once we leveled off at 4,500' it was dead calm, just a wonderful ride. Granted, we couldn't see too far to the south (OK, 20-30 miles, but when you're used to 50 or better, this is "low-vis").
Over the southern tip of Whidbey Island I saw an Embraer departing Paine Field. It was showing up as Sky West, so I guess it must have been United, the Alaska flights use Horizon identities. We were converging at about a 45o angle, but I expected him to keep climbing and go well over me. As a result I turned further west to parallel his course and try not encounter his wake. He leveled off at what appeared to be 4,000' (he was a little below me). Once I saw that I turned back toward the south to pass behind and above him. After another minute or so he resumed his climb. I wasn't really a conflict, but he seemed to be waiting for me. Nice guy.
We made the usual turn and climb at Bremerton and headed toward Olympia. There was a band of clouds just to the north of Olympia, but there was what looked like a large hole behind it so I stayed at 5,500' hoping to be able to get down on the other side without back tracking.
The hole I expected was there, but it did not extend as far as I had hoped. I was hoping to be able to clear the top of the Olympia Class D and stay below the clouds until clearing the Class D to begin a descent to get below the clouds that were still at 2,100' over Chehalis.
In this instance, the clouds did not cooperate and they lowered directly over the Class D sending us out to the west of Black Lake to stay outside. Sure, we could have called up the tower and gotten clearance to fly through the Class D (it's not like there is much traffic at Olympia [that isn't snark, there really isn't]), but anyone can do it the easy way.
Clearing the Class D it was time to slow down and get configured for landing. As I brought the power back and slowed below about 140 MPH I needed to start adding some nose up trim. I hot the coolie-hat switch for nose up like always and it didn't seem to be enough. I bumped the switch over and over and it didn't seem to help, if anything the nose seemed to be getting heavier. Then I held the switch for a much longer time than I would have ever had to before. I started looking around to figure what was wrong and why it was taking so much nose up trim. Afraid that the trim motor may be running backwards I bumped the nose down switch to see what that would do. Bad idea, more nose down.
It became pretty obvious that I had an issue and couldn't do anything about at the moment. Rule #1 - Fly the airplane. I had full control and nothing was really amiss, so I continued to land. I had to hold a pretty hefty amount of back pressure to keep the nose up, but it was manageable (I've heard that the Blue Angels have their airplanes rigged to require a 26 lb pull to maintain level flight). I knew it would take even more to flare when I got to the runway so I tried to prepare myself. I got it down for a respectable, if a little more solid that I would have preferred, landing.
Once in the parking spot and shut down I tried the trim switch again. Still no response in the nose up direction, but it did still work in the nose down position. NO! Now I have even more nose down. How am I going to get home? Carl was kind enough to offer me a ride home if I wanted to leave the airplane, but since that wouldn't really help anything and there was rain coming in the following week, I decided to limp home.
After lunch I tried a few things, like wiggling the wire at the base of the stick while hitting the switch, hoping that maybe a loose wire would move the trim tab back toward neutral. This did not work, but then, I really didn't think it would.
My plan was to shorten the trim push rod to move the tab back toward neutral. I had just enough tools on board to do this, but when I pulled the cotter pin out that held the clevis pin that held the push rod to the trim tab one ear broke off, and the other most certainly would have broken off trying to bend it if I reused that pin. Fortunately the on-field airplane shop was open and I was able to get a cotter pin from them.
Thus emboldened I sallied forth for the homeward journey. Where the trim tab was set I figured I would have to hold some nose down in cruise on the way home and then nose up to land.
As it happened, the clouds hadn't hardly moved at all since we came in, they were mostly where we had left them. That is only remarkable in that we were expecting a clearing trend through the afternoon. Once again we had to stay below the clouds and go west of the Olympia Class D until the clouds broke and we could climb up. The only real problem with that is that it was pretty bumpy down there.
My estimate was correct and I had to hold some forward stick to maintain level flight. It worked just about right in a climb. Once leveling at 6,500' I put both hands on the stick and it was pretty comfortable to maintain altitude. To keep the stick forces down I slowed down somewhat from normal. I was running 22 inches at 2,400 RPM. That gave me about 160 MPH indicated, but I still had a ground speed of 192 MPH.
Descending was a little different. Even pulling back to 20 inches and keeping a 500'/minute descent I had to increase the forward pressure. It was still manageable, but my arms were getting a little tired. I wouldn't want to have to do this for a really long time. As expected, as I slowed near the airport the stick forces increased requiring a very noticeable pull on the stick. Again, while not excessive, it isn't something you would want to do for a long time.
I made it down and actually pulled off a passable landing. By the time I got out of the airplane my right arm was really tired.
The first thing I did was to pull the tail faring off to see if I could find a broken wire at the servo and/or a way to access the wires for the servo so I could test it by itself with a 9-volt battery. I ended up pulling the servo out of the left elevator, but all of the wires looked solid and intact with no sign of damage anywhere.
By this time I was pretty uncomfortably warm (and muggy) in the hangar so I decided to call it a day. Once home I started doing some research because Carl had had a similar problem in the past. It is so nice to buy an airplane from someone who is even more a stickler for documentation that I am. It didn't take me long to find a log book entry from 2011 (991 hrs). Chris had replaced the old REL1 servo on the roll trim servo with the newer REL2 relay, also from Ray Allen. I also found a VAF post from Paul Dye that (among other Google hits) shows this to be a pretty common problem.
The first post is below.
07-06-2009, 10:15 AM
Well, the good news is that once I change out the pitch trim relay in Louise's RV-6, I should never have to deal with the older "dash 1" RAC trim relays ago - I'll have everything up to "dash 2" (the larger, newer) relays in both airplanes.
For those not familiar, the earlier relays have a tendency to start getting sticky, and fail so that you get no function in one direction. Generally, if you blip them the other way, you can then get it to work the way you want. My past experience has been that you have some time to change it before it quits completely, but this time, Louise had one problem a couple weeks ago, and this morning, it was pretty much dead - made for an interesting morning commute...
My advice for anyone that has the "dash 1' relays and still has access to them if you're building - change them now....unless you like having stuck trim in flight...
Full thread here: http://www.vansairforce.com/community/showthread.php?t=45307.
Fortunately the REL2 relay is only $60, pretty cheap in aviation terms. I will order one and replace it next weekend. Unfortunately, no more flying until I get it fixed.
9/13/19 - The repair begins. I got the new relay from Aircraft Spruce as promised, only to find out that my Dad had one in his hangar the whole time. I was able to locate the trim relays pretty easily. Locating them and getting access to them, very different things.
OK, it was bundled up a lot neater than this and I had to cut about a hundred (slight exaggeration) zip ties to get this level of access.
Since there was no single point of connection, the wires go a number of different direction, my idea of installing a connector at this point would have just created a lot more work. I just want to get it working again. I had decided to use D-Sub pins for connectors. Most of the wires were (I thought they all were) 24 gauge. I got the right pins and crimping tools for 24 gauge wire and starting working.
I want to label things as much as possible and do as much as I could outside the airplane at the bench so I installed female pins to all the wires on the relay itself. This turned out to be a joy with the proper tools. I made the unknowing mistake of assuming (yes, I know) that all of the wires were 24 gauge. As it turns out, the wires going to the tail are apparently 26 gauge as I could come up with no way to make a crimp that would hold, even thought the pins were supposed to be for 24-26 gauge wire and the crimper was for 24-28 gauge pins.
I must have burned through $10 worth of pins trying to get one to hold. When that failed I thought I could solder the connector and then crimp it. Sounds good in theory, not so much in practice. In the end I had to just solder the wires together and forget the idea of any kind of crimp device at all.
Though it took a day and half in all to get all of that sorted out, I felt pretty good when I got it all together. In order to make sure that the motor turned the proper way for up and down trim I just twisted the to wires that move the servo and would solder them when I knew all was correct.
Moment of truth - try nose down trim. Works. Yeah!. Nose up trim. Silence. Yep, still no nose up trim. RATS!
Now what? Electrical troubleshooting is not my strong suit, not even a little, and I don't enjoy it. Somehow I need to determine if the problem is the servo itself or the switch in the stick, or (please no) a broken wire somewhere in between.
I pulled the servo back out of the elevator to test it at the source. Fortunately I had another trim kit from another project so I was able to play with it to figure out how to get the servo to move with just a battery. I had to cut the heat shrink off the two white wires at the servo (soldered by the way). I hooked the battery to it and got the servo to move in both directions. Not the servo. Too bad as I had a spare and it would have been very easy to replace. OK, so what about the wire from the relay to the servo?
I had already tried from the cockpit wiring and couldn't get it to work. Once I was able to remind myself that I just need to apply power to the two white wires coming out of the servo and reverse the polarity to reverse the direction I tried it again in the airplane. I still had the wires going to the servo temporarily connected to the wires for the relay. I thought I should be able to apply power at that joint and move the servo, but it wouldn't move. I disconnected those two wires from the servo and tried it again and the servo worked in both directions. OK, not the wire through the fuselage.
By now I am starting to get a sinking feeling. About the only thing left (the most difficult thing to replace) was the switch in the stick grip (Infinity). Carl thought it was the switch from the beginning, but the last time he had a trim problem it was the relay and other people had had a lot of relay problems, so I really thought it was the relay. So much so that I didn't do any troubleshooting at all before replacing it. Mistake #1. In the Air Force we called that "troubleshooting from the truck". In other words, the last time I had this problem I replaced this and it worked, so do that again. Sometimes that works, sometimes it doesn't. This time it didn't.
Fortunately I also have another Infinity stick grip laying around and I was able to open it up to look at the guts. The switch is soldered in and it looked tricky enough to un-solder and re-solder on the bench, but would be a real bear in the airplane. Before getting into this I wanted to make good and sure that the switch was the culprit. How? Fortunately Carl had bought a new switch back when he had his trim problem so I had one available to play with. It didn't take long to figure out that a simple continuity test through the switch should tell me if it is working or not. I tried with the new switch first. Ground probe of the meter to the center pin and then the power probe on each of the other 4 terminals in turn, activate the switch and if there is continuity there switch is good.
The first thing I noticed was a seemingly broken black wire, but I can't find anything that it looks like it goes to. I tested the continuity of the switch and sure enough, in one position there was no continuity. It is the switch that is bad. One thing that has me a little concerned is that before removing and opening up the stick grip the aileron trim worked both ways and the nose down worked. Now, with the switch out it doesn't work in any direction. The PTT works and the flap switch works, but not the trim. I hope I didn't break something else.
I needed to come up with some way to hold the switch so that I can remove the wires from the old switch and solder them to the new switch, a process that requires at least 2 hands in and of itself. With the way the stick grip is wired in, taking it out to work on it on the bench is out of the questions. Fortunately, Rube Goldberg to the rescue. With some scrounging and fiddling with things I was able to come up with a relative simple method to hold the switch secure enough to work on. It may not be elegant, but it is cheap and it should work. Unfortunately, by the time I got it all rigged up it was too late to start in on the switch. That will have to wait until next weekend.
9/20/19 - Let's try this again. I managed to come up with a better holding mechanism and what is shown below is what I actually used.
Getting the old switch out and the new switch back in wasn't as difficult as I had expected. It did, however, require working in a pretty uncomfortable position. When finished I had no feeling left in my legs and had a hard time getting out.
With the new switch in I tried it again and I still get nothing in any direction. WHY! I noticed that the red wire was cut almost all the way through, probably from removing a zip tie. I soldered that back together thinking that was probably the problem so I expectantly tried it again and still nothing. WHAT?!
Just for giggles I put the whole stick grip back together (took 3 tries) just to see if that would do anything. After all, 3 out of 4 positions worked before I took it apart. No joy (but none expected).
I spent a lot of time thinking about it and talking it over with Carl and the only thing I can come up with is that it has to be a ground problem as that is the only thing common to all four positions on the hat switch. So, the next thing I tried was to run a separate ground from the center terminal directly to a known ground and try it again. Still nothing.
The next thing I tried was to check continuity of the ground wire from the switch to the bottom of the stick and it is indeed continuous, so the ground wire probably isn't broken. I once again went through all of the wires and connections looking for something disconnected or broken and found nothing.
Next I wondered if maybe I fried the switch when replacing it (yes, I got all the wires back in the same places, thanks for asking). I went back to doing a continuity test on the switch itself. I got interesting but useless (to me) results. In three of the four positions with the switch open my meter reads 50 (on the 20K) setting. I would have expected it to read infinity, or open. When actuating the switch it does go to zero, except for the green wire. When I put the probes on the ground and the green wire I get zero with the switch not actuated. Actuating the switch does nothing. No, I do not have any of the wires touching on the back of the switch (thanks for playing).
I also double checked the leads to the meter and no, they are not touching either (keep those ideas coming).
I also tried checking continuity of the four wires from the switch to their other ends at the stick base. Again, I get a reading of about 50 on the meter and when actuating the switch it went to zero. Don't know what, if anything, that means.
I am literally out of ideas. What if I were to replace the entire stick grip assembly?
Help Mr. Wizard!
9/21/19 - With no progress to show for my efforts Carl and I went and talked to Terry Burch, a long time RV builder and mechanic, to see if he might have any insight. He did provide some information and made me rethink my troubleshooting direction. He suggested both powering the relay right at the relay with a battery (I used an electronic power supply) and also jumping each pin from the hat switch directly to ground with aircraft power on (thus taking the switch out of the equation and seeing if the system will work at all). He also suggested potentially removing the switch entirely and just manipulating the wires.
I unsoldered the brown and green wires from the switch and then confirmed continuity for all wires from the switch to the base of the stick (all good). Next I tried turning on the ship's battery and running a jumper from each outboard terminal to ground (same effect as closing the switch) and nothing moved. I tried it on both the wires connected to the switch and those freed from it. No difference.
Next I took my power supply and put power to the red/blue wires (power to the relay) and the black wire (ground). When I turned on the power I could hear a) the relay contacts closing (click) and b) the elevator trim motor turning (in the direction that it didn't before). That's something. I don't know what, but it is something. The only head scratcher is why did it move just by putting power to the relay? Is something shorted? Only the elevator motor turned, although I'm not sure which direction of aileron was still connected, the servo is at its travel limit and shut off, so that may not mean anything.
Next I tried connecting the meter to the power and ground on the relay (both relays use a common power and ground) and turned on the ship's battery. Two things happened, or more precisely didn't happen: 1) there was no click of the relay and 2) there was no reading of voltage at the relay. OK, if the relay(s) is/are not getting power, that would explain why it doesn't work in any direction (now). It doesn't however, explain what the original failure was or why it went from only one direction not working to all of them not working.
I was able to confirm that the ground to the two relays is good, so it appears that is really not getting power. Why? Well, that's the question for the prize. I still can find no reason why there is no power. Of course, it would be too simple to have a dedicated trim circuit with its own breaker. No, there weren't any breakers popped and just for grins I reset them all.
I don't think it will do any good to contact Infinity because it now doesn't seem like it is their product that failed.
I think it is time to seek professional help. Of some kind.
9/22/19-After talking to Terry yesterday Carl noticed that the wiring diagram for the REL1 called for a 1 amp fuse in the power line. I didn't see a fuse anywhere and didn't think one had been used,. I'm sure they relied on the circuit breaker for circuit protection.
I didn't think much of it, but then started thinking about it again this morning and it certainly made sense that if there was a fuse and if I had shorted a couple of wires it could have blown the fuse and that would certainly explain why I wasn't getting power.
I was able to find where the power wire goes into the gear tower, but I had no way to see where it actually gets power from . There are two rows of circuit breakers at the bottom right of the panel. Only the bottom row is accessible from the bottom, access to the top row requires dropping the whole panel, basically having it sit in your lap, to get to them. It became pretty evident that further disassembly was going to be required to find out where the power wire goes. To that end, I took the cover plate off the right side and made ready to remove the panel.
In preparation for being pretty well stuck in the airplane while doing this, I made a little diving board to put things on.
Once I got the panel in my lap it became clear that it would be even easier if the VM1000 screen was out of the way, adding more light and access. Since it is held in with 4 screws and a ribbon cord it was easy to get out, plus with it out of the way I am less likely to damage it.
Once I had the panel in my lap I saw, much to my surprise, a wire with an in-line fuse in it. I thought :could it really be this easy?" Well, of course not, I should have known better. I managed to get it apart and get the fuse out and it was indeed a 1 amp fuse, but it wasn't blown (confirmed with the meter). It looks like it goes to the clock, or chronometer if you are so inclined.
Once again, no easy answer jumped out at me so I will have to go through the process of chasing that one wire all the way to its other end.
At this point it seems like it wouldn't take that much longer to rip it all out and start over with a new stick grip. In order to do that, however, I still have to figure out where it is getting power from.
9/24/19 - With nothing else working I did go ahead and buy a new stick grip. The only thing I don't like about this one is that the flap switch will stay in the up position instead of springing back to off, so I have to remember to turn it off after the flaps come up and also I sometimes kick it getting in or out so sometimes the flaps will start up as soon as I turn the battery on.
I tried to make the swap as easy as possible by labeling the various wires and crimping pins on while it was on the bench and accessible. Sure looks nice, doesn't it?
Have you identified the flaw with this idea yet?
There is a roughly 9/16" hole at the bottom of the stick for wires to exit. They can't go out the bottom due to the control linkage there. The diameter of the hole is barely larger than the diameter of the wire and it has to make an abrupt 90 degree turn to exit. I thought it wouldn't be too hard, I could just pull the wires out a few at a time. Long story short, that doesn't work and I had to cut all of that stuff off in order to get the wire through the hole. Once all the wires were routed, hooking everything back up was relatively easy.
While it took entirely too long to figure out and repair, I was back in the air by 9/29.