The Big Picture and Red Herrings



I’ve often heard the phrase, “Don’t miss the big picture.” Sometimes it’s even referred to as “target fixation,” and there are documented cases of pilots on bombing or strafing runs seemingly getting so fixated on the target that they fly right into it, with disastrous consequences. I thought I would share some personal cases of big picture experiences I have had with a few airplanes, and one with a car.

The first involved the second owner (non-builder) of a rather new RV-10. The aircraft had about 80 hours on it, and the owner contacted me and asked for some help solving a few nagging problems. The worst was an annoying noise in the electrical system that could be heard in the intercom, and constantly spiking EGTs and CHTs. He also casually mentioned that he would like me to install a rudder trim mechanism, as it needed right rudder pressure in flight in order to maintain coordinated flight.

Bundling the CHT and EGT wiring with the spark plug wires can cause fluctuating readings on the temps. It is better to route them from behind and away from the plug wires.

As he taxied up to my hangar, I noticed that the wheels were tracking in an unusual manner, almost wobbling in fact. After he shut down, a more careful inspection showed that the axle nuts were missing the cotter keys, allowing the axle nut to back off to the point that the only thing keeping the wheels on the bearings were the brake calipers! Yikes. Luckily, that was an easy fix, but it gave me some pause about the rest of the build quality.

Airshow coverage sponsor:

Sure enough, a much more thorough inspection of the aircraft revealed missing cotter keys in a few other places, the most critical being the nuts on the Lord engine mounts. That’s right—no cotter keys and the nuts came off in my hands! The spiking on the EGTs and CHTs was due to the sensor wiring bundled with the spark plug wires, along with some intermittent connections due to poor crimps. This was not the first or last time I have seen wires routed that way, causing the same problems.

Another issue involved the autopilot lurching intermittently while in altitude hold mode. This turned out to be an improperly installed static system, which was allowing water into the static plumbing. Rerouting the static system to prevent water ingestion, as well as installing a cockpit-controlled alternate static source (required for IFR), should ensure no more problems in this area. Yes, there was a substantial amount of water in the system that I blew out, and the problem has not recurred, so the autopilot itself was not the culprit.

Rudder Trim Problems

Next, I installed an internal rudder trim system from M.L. Skunk Works, as per the owner’s request. Once I was finished with the rest of the inspection, I buttoned up the aircraft and took it for a test flight. To say the aircraft required right trim in cruise for coordinated flight was the most dramatic understatement I think I have ever heard. My right leg actually cramped after about 20 minutes of flight. I had adjusted the rudder trim so far to the right that I thought the trim cable was going to snap, and eventually it did! I also noticed that the trim forces subsided at lower airspeeds, but I needed to land and figure this one out.

This fairing was installed crooked and protruded about 3/8-inch off to one side, which caused it to act as a fixed trim tab (left). The resultant forces were almost impossible to trim off, and the airplane flew quite crooked. A new fairing fixed the problem (right).

On most Amateur-Built aircraft there are many builder areas that require attention to detail in order to have a properly trimmed aircraft. Specifically on the RVs, misalignment of the gear leg fairings and wheelpants can have a real adverse impact on drag and yaw. Setting them correctly requires jacking the aircraft so that all of the weight is off of the wheels and the gear legs are in the “flight” position. During the building process I usually accomplish this task prior to installing the wings, as it is much easier to jack the lighter fuselage than a completely built aircraft. And I am always nervous around aircraft that are sitting completely on jacks. All it takes is one thoughtless moment of walking to get a tool and bumping into a wingtip to cause some serious damage. So, I set about leveling the RV-10 on jacks and did discover that the left and right leg fairings were slightly out of trail. Great. I adjusted them, fixed the broken rudder trim cable and felt confident the problem was solved.

So much for that line of thinking. I wasn’t even close! On the next flight the rudder trim forces were just as high, and the airplane actually flew so crooked that my son who is not even a pilot, but lives on the end of the runway and witnesses a lot of takeoffs, mentioned that it was the most crooked-flying airplane he had ever seen! By the way, when I engaged the autopilot, it would track a heading with one wing substantially lower than the other, verifying it was not an AHRS alignment problem. And my own view out the window, along with the feel of my seat, told me it was still substantially yawed.

So, back on the ground I thoroughly inspected every other thing I could think of, carefully measuring the vertical fin offset, along with horizontal and vertical stabilizer alignment. I even went to the detail of dropping plumb bobs to verify the wings and tail feathers were properly aligned to each other and the fuselage. I didn’t find any smoking gun, and seeing as the RV-10 is pre-punched in these critical alignment areas, I really didn’t expect to find anything. I even checked the engine mount for alignment, using my own RV-10 as a guide. Still nothing.

It was only after I backed away from the airplane a good 30 feet to look at the big picture, that I saw something amiss. The fairing at the top of the vertical fin was installed somewhat crooked, and protruded about 3/8-inch out on the left side of the aircraft. Hmm? Could that be acting as a fixed trim tab on the vertical fin? The more I looked at it, the more I convinced myself that it was the problem. I had a quick discussion with Paul Dye, our editor in chief, and he agreed. The problem now was convincing the owner I needed to cut off the fairing and install a new one, which could mess up his really nice paint job, as the fairing was blended into the paint and not removable. As I thought, he was not real open to cutting it off. However, I was not comfortable with this airplane continuing to fly with that much constant force on the vertical fin, and I politely stated I would not sign off the condition inspection without fixing the problem. After all, it is supposed to be in a condition for safe operation, right?

So, I did order a new fairing from Van’s and very carefully removed the original fairing, trying to disturb as little of the paint as possible. I made the new fairing removable with nutplates, so when completed it looked original, and the vertical fin required no paint except for the new fairing. On the subsequent flight I was rewarded with a wonderfully flying RV-10, along with a rudder trim system that works as well. Lesson learned!

Red Herrings

The most recent big-picture fiasco occurred on another RV-10 as well. The customer was coming to see me for some upgrades and called to inform me the aircraft wouldn’t start. Luckily, we were able to use FaceTime, and I had him show me the volts reading while engaging the starter. The reading dropped off enough that it looked like a weak battery, even though the aircraft was only about eight months old, with 90 hours on it and an Odyssey PC925 battery. He charged it, and it started, but then wouldn’t start again after taxiing over to the fuel pumps. Well, we all know such a short taxi probably wouldn’t charge a weak/dead battery enough for a start, so let’s charge it again. Yep, that worked and he was on his way. Let’s call this Red Herring #1. Once here, it wouldn’t start again, and upon inquiry, he stated the alternator showed 13.6 volts for the entire 2-hour flight. Hmm. So, the alternator is working, but we all know the Odyssey brand of batteries likes a higher charging voltage, something like 14.3 volts, and if not charged at that voltage, they will die an early death. Clearly the regulator needed adjusting. Let’s call this Red Herring #2.

I find a battery tester that puts a load on the battery to be an invaluable tool for troubleshooting electrical problems. Here is a reading after a 12-second load on the battery, clearly indicating that the battery was not the source of the starter problems.

I checked the battery with a battery load tester, and surprisingly it tested really well, twice in fact, and showed an open circuit voltage of 12.8, which is just right for an Odyssey battery. Hmm. I then put a voltmeter on the battery and at the starter while I engaged the starter. The starter did not engage, but there was a substantial voltage drop. Must be the aircraft wiring or the starter solenoid, so I checked both of them and couldn’t find any reason for the voltage drop. Bypassing the starter cable from the solenoid to the starter showed the same voltage drop, but I also noticed the cables got hot, as did the starter. So, off came the starter to be bench tested. Of course, it bench tested fine with a battery and cables on the bench. But after 25 or so attempts, it finally failed. I found a poor crimp on the jumper wire at the starter, fixed it, and could not make it fail again, so I reinstalled it on the aircraft. Red Herring #3! After the fifth start, it actually failed again, so I removed it and, sure enough, I could make it fail on the bench only after many attempts. The solenoid on the starter was intermittently hanging up. Discussions with “TJ” Jenkins at B&C Specialty Products confirmed the diagnosis, and they fixed it the same day under warranty. Of course, I did adjust the regulator to improve the life of the B&C battery, but I didn’t expect such an early failure of the B&C starter, as they are so reliable.

Car Trouble

The last big picture experience actually happened with my daughter-in-law’s car. My son was out of town, so she called me to say her car wouldn’t shift out of low gear after she stopped at the mailbox on the way home. Must be the transmission, right? I got in the car, and after starting the engine I looked at the instrument panel for what few gauges are there anymore, and the voltmeter didn’t look right. No range marks, of course, but it was reading about 12 volts as best I could tell, and I know most new cars run about 14.5 volts. I was guessing she thought I didn’t know the difference between the transmission and the alternator when I asked her if the volts always read that low! Unfortunately, she couldn’t remember what it normally read. A quick drive up the street confirmed the transmission wouldn’t shift, but I couldn’t get past the voltmeter reading. I checked the battery, and it was quite low, and there wasn’t any change with the engine running. I was convinced the alternator was bad, so I charged the battery. Lo and behold, the transmission shifted with a fully charged battery. A quick call to the auto shop confirmed a bad alternator would put the car into “limp-home” mode, not allowing the transmission to shift. This time, paying attention to the big picture really worked, and sooner rather than later!

What good is a voltmeter without range markings? When the alternator failed, the owner wasn’t sure as to what it normally read, and the failed alternator put the car in “limp-home” mode, which acted like a failed transmission.

By the way, this limp-home mode is not something I would want in an aircraft with an auto conversion! Something to think about for those of you experimenting with auto conversions. I am aware of at least one RV-10 with an auto conversion that had a hard landing due to a temperature parameter exceeding the limits in the ECU, causing a reduction in power.

I bet some of you have some similar stories.


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.