Fun with Maintenance


First, let me say that our Viking has been remarkably trouble-free.  Also, I maintain our airplane with a no-expense-spared philosophy - meaning, if I find something wrong or heading south, I either fix it or have it fixed.  The problems I describe below have occurred over the course of almost 800 hours of flying time in 3 1/2 years.  I have to admit that I've grown tired of electrical problems, but I now have a great understanding of the system and it is actually pretty simple and well designed.  It's just that the Viking has a lot of systems with things to break.  Based on my experience the Viking is no worse than any other retract or multi-systems airplane from a maintenance perspective and better than a lot of them because the things that break tend to be relatively inexpensive (in airplane terms) and routine to fix.

The following are the things that seem to trouble Viking owners:

Nose gear collar fractures in pre-'79's

Gear motor (pump) and actuator leaks

Gear leg cracks that won't hold strut pressure

Squat switch and related wiring problems

Autopilot computers

Voltage regulators

Vernier engine controls (they just get old and need replacing after 25 years!)

Avionics noise

Fuel gauge sender units in earlier models

Gear scissors pivot bolt in some older applications (now known as the "Nixon" bolt)

Strut seals

Shimmy dampener seals in 1979 and later models (easy to reseal)

Fuel cap seals - these shrink and harden about every 2 years and are costly from BAC.  Some people use replacements from the same manufacturer BAC uses but they arenít the same Butyl rubber and the soak up the fuel.

Following are some of my experiences:


Table of Contents

  1. Voltage Problems - round 1

  2. What's that hissing sound?

  3. Tunes over the I/C

  4. Autopilot gyrations

  5. Roll over Beethoven (and AI)

  6. Prop nicks

  7. Whole lotta shakin' goin' on

  8. What's that squealing sound?

  9. Voltage Problems - round 2

  10. What's that red stuff streaming over the flap?

 


Voltage Problems - round 1

Shortly after buying N28067, I began to notice a flicker in the ammeter gauge.  At night, the panel lights would flicker which I had to work hard to ignore to avoid a vertigo effect.  After a particularly disturbing event of this in night IMC, I grounded the airplane until I could determine the problem.

The previous owner had the alternator replaced the year before I purchased the airplane. I suspect he was trying to solve the same problem.  I don't like the troubleshooting by replacement method (I'm too cheap!), so I set out to measure every voltage drop and resistance from the battery forward.  I read quite a bit about acceptable drops/common problems from information from Zeftronic (a PMA supplier of replacement parts) and Cherokee Hints and Tips, an invaluable aircraft maintenance guide.  Both indicated voltage drop of over .5v across any switch, breaker or wire lead indicated a possible problem.

I measured voltage at the battery, bus bar, bat side of master switch, alternator side of master switch, field breaker, OV relay, alternator, and regulator.  I also measured resistance across these various components and the leads between them.  None of the measurements indicated a conclusive problem and the total voltage drop was .9v from the battery to the voltage regulator.

I replaced the master switch because the contacts were somewhat pitted (20 year old part remember).  Reading the article in the Cherokee book really caused me to suspect that to be the problem (Christmas tree light effect it would cause was exactly what I was having) - besides, its only a $10 part.  No help at all.

I tried adjusting the pot on the regulator (original TCM part).  That increased the voltage alright, but still didn't kill the flicker problem.  I finally decided it couldn't be anything else so I replaced the regulator with an STC'd Zeftronics solid state part.  Voltage and amperage were rock solid.  So much for not just following my gut in the first place...

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What's that hissing sound?

Flying along IFR to Dallas and I can't figure out what all the hissing is! All the vents are off (it's January and COLD and 9,000 ft). Headset off and follow my ear.  Funny, seems like it's right in my left ear.  Oh my goodness, there's a 1/4" gaping break in the left window from the cutout down to the bottom !  On landing, the gap closed back up as the pressure equalized (mental note, that stuff about alternate static adjustments really is right).  Maybe that new fancy seal I put on the cutout that was a little thicker than the original wasn't such a good idea after all !  I temporarily taped it with some very heavy clear tape and that worked for a few flights I needed to make that week.

Here's my replacement saga with "what I learned" at the end.  This is an approved preventative maintenance procedure under FAR 43 by the way.:

My airplane was down for a month. I ordered an LP Aeroplastics window with cutout and insert assembly through Chief. About $190 if I remember correctly. I strongly recommend LP and going through Chief didn't seem to slow it down. They drop shipped from the factory and I got it in a few days. I didn't order express shipping. When I got it and took it out to the airplane I kicked myself about 5 times because I had not ordered tinted!!!! In fact, until then I had never even realized my windows were tinted, but it's a significant green tint. I called Chief and they didn't give me any grief over the exchange (other than the standard tint upcharge) and said to send it back direct to LP.

Also, the window is obviously a hand milled part and since the frame is obviously hand laid up, the milled edges didn't quite match. I've seen ones Miller has replaced and been unimpressed with the fit - nothing against Miller, because now I see why. Since I had to ship the clear one back for a tinted one anyway, I decided to ship the old one and tell LP to mill the new one to match. LP did mill the new one to match the old one and I got it back within a few days. Fit was perfect - The insert cutout is a different size from the original - not sure why that is, but it makes the original a scrapper.

I recommend two sets of hands to install. It just seemed easier with all that wet sealant to have someone help position it and hold it in place while I tightened the brackets (I had to fill and drill several of those holes as prep work by the way). If I had to do it again, I would use that body sealant Duane Mitchell has me using for the landing light. It seals pretty well and releases ok from plexi. I used a tan silicone to match the paint and it has been perfectly leak free, but it will be a bummer to get out if it ever cracks again. I think my 3M distributor later told me the body sealant can be ordered in colors.

I carefully masked the edges with easy release masking tape (blue) so I could pull the tape before the silicone dried. That worked well. I did make one prep mistake though. On the inside of the window, the old one was painted around the edge because, interestingly enough, the inside decorative frame is bigger than the fuselage window cutout so to make it so you can't see some exposed window frame edge through the window they paint the window. I was in such a hurry, I didn't notice why it was painted (all of mine are) and didn't paint it at home. I had to mask and hand paint it in the airplane after install which was a major pain in the ass. In retrospect, I should have masked and painted it at home before install - that way I could have done it with the protective plastic sheath still on and sprayed it which would have looked much smoother. I just painted with a tan auto touch up paint which has worked ok - if I had sprayed at home, I would have sprayed with an epoxy.

What I learned:

Don't even bother ordering a window off the shelf. Send them yours and have them custom fit it to match.

Leave the plastic sheathing on until fully installed. Just peel the edges back so you can mask.

Fully mask the outside and spray on the paint framing edge on the inside before install.

Mask right up to the milled edge on the outside for install - you don't want or need any sealant on the window. Also mask the fuselage right up to the edge of the frame.

When installing, do a full dry fit including screwing down the brackets to see where it doesn't push up tight. Mine had several places where even an extra screw still just didn't get it. Have several thin tapered wood shims ready to put between the window and brackets in places.

Only put a thin coat of sealant on the window. Put a full bead on the inside of the frame. Do not wipe off excess until the brackets are fully screwed down (with shims in place if needed) to push out the excess. Have a helper on the outside tell you where it doesn't look as tight and don't be afraid to drill and add a screw to the brackets if necessary (they are <90 bend deg "spring" steel, so screwing them down tightens the window against the fuselage.

Fully wipe off excess and smooth bead. Remove masking before sealant dries, but BE CAREFUL not to pull the outer paint layer off (pull slowly and carefully).

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Tunes over the I/C

[writeup to come...]

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Autopilot gyrations

[writeup to come...]

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Roll over Beethoven and AI

[writeup to come...]

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Prop Nicks

This one's easy.  Buy the PropGuard tape.  Put in on and instantly add years to your prop's life -  your prop will thank you.   I know, it's ridiculous to pay $60 for a strip of plastic tape, but the guy did go through the hassle of getting the STC and the tape says PMA on it so no pesky FSDO guy can give you any crap over it.  Buy one package.  I know they say it covers two blades, but it covered all three of mine with a couple feet to spare.  I now own a second package for replacement several years down the road.  With the tape on, the tip abrasion and small rock nicks I used to get are non-existant.  I know the stuff will not stop big rocks, but it has done perfectly repelling the minor stuff that used to drive me nuts.  Now, if I can just convince Duane NOT to do a runup check at annual until I have personally swept off the area around the prop maybe I'll be ok...

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Whole lotta shakin' goin' on

[writeup to come...]

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What's that squealing sound?

At annual '98, Miller changed the alternator pulley and put on a new belt.  According to Duane Mitchell, AP/IA there, the pulleys quite frequently wear and have to be replaced (aluminum pulley PMA part costs $178 !).  All seemed well for the first five hours or so. Then, Sharon and I were flying along and we both felt the engine/airplane "skip a beat".  I wasn't sure what the problem was and everything seemed normal for the next couple hours.  Then I began to notice that the ammeter would occasionally dip way low for a few seconds.  I pulled the cowl and noticed the belt was "glazed".  I chalked it up to too loose of a belt install and put on a new one.  Several hours later I retightened the belt (but not overtight - a good test is if you can twist the belt inside out at the middle of the span.)

In May, we made the trip to Santa Fe for the annual IVOG get-together.  Trip up was great IFR fun battling a significant TS system over most of West Texas and New Mexico.  Fortunately we had no airplane problems.

On Saturday we piled into the airplane for the IVOG fly-out to Gunnison.  We taxied to the runup area and did a runup.  After pulling the throttle back, the alternator belt started squealing loudly for a few seconds, then stopped and the ammeter gauge was showing no charge.  We taxied back and pulled off the cowl.  The alternator pulley was completely frozen and the belt was very hot.  Remember, this was Memorial Day - fortunately one of the IVOG members (Tom Russ) had an alternator in his hangar back in Tucson (2 hours away) and is an A&P so we hopped in his airplane to go get it (his airplane developed a problem on the way back so we asked Carter DuBois to fly down to bring us back to Santa Fe - thanks Carter!)  I put the new alternator on the next morning and we flew home with no further problems.

My guess is when Miller put the new pulley on they overtightened the belt and caused the bearings to wear.  In retrospect, I think the ammeter indications I was seeing were the alternater momentarily binding rather than the belt just slipping.  I should have seen the impending failure coming but didn't.  Lesson learned is DO NOT OVERTIGHTEN the alternator belt. Also, be very careful tightening the alternator mounting bolt that threads into the housing.  The housing is aluminum and strips very easily.  The OH'd unit I received (so I could remove and send Tom's back) had threads that were almost completely stripped - I had to drill out and use a through bolt instead.

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Voltage Problems - round 2

After the alternator problem in May, the light flickering problem came back - *!#&*, I thought I fixed the flickering problem !  Since I now had a new VR and alternator I pretty quickly concluded it had to be a battery problem.  The symptoms didn't really make sense, but I've seen charging systems do weird things when they didn't have a good battery in the loop.  I replaced the battery with a new fully charged Gill and still had the problem.

I simply fly too much IFR and night flying to have an iffy electrical systems, so, once again, I stood on my head with a multitester and check voltage drops looking for a wiring problem - it HAD to be wiring since the alternator and VR were new right?  I checked everything and again, everything looked ok.  Then, I noticed that when I wiggled one of the terminals on the OV relay (original factory unit - I did not get the Zef VR with OV) that the resistance across the switch increased.  Ahah!  I pulled it, and disassembled it.  The terminal was riveted to the circuit board inside (no solder) and the rivet had loosened.  I drilled out the rivet, reinstalled the terminal, cleaned all the connections and put it back together.  Looked good, and I felt accomplished at having found the problem.  I reinstalled and went flying.  *!#&*, the problem's still there!  Next, I connected the two terminals around the OV relay to verify that definitely wasn't the problem.  Still had the flickering

Ok, wiring all tests ok, OV isn't the problem, new alternator and new battery.  Could the old alternator have fried the VR when it died in Santa Fe?  In spite of my distaste for troubleshooting by replacement, this simply had to be the problem so I ordered another VR.  Several days later I received the new VR and put it on.  Ground tests looked good so I went flying.  The flickering was gone from the ammeter and the lights and hasn't returned since.  Chalk up $180 more to the costs of an overtighted altenator belt!

Actually, since then I've learned that several people that got Zef units around that time have had problems with them.  I now believe that the unit simply crapped out on its own.  But, since the unit is out of warranty (and was by the time this happened too) I haven't sent it back.  Everyone that has gotten a replacement Zef unit seems to be running fine and mine has been in over a year now and is working fine so I guess Zef just got a bad run of a component back then.

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What's that red stuff streaming over the flap?

[writeup to come...]

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Craig Gifford
All information herein is for for entertainment only.  Do NOT rely on this for any maintenance procedures on actual aircraft.
Revised: March 04, 2001 .