Stinson

It has been said that a smart man learns from his mistakes, and a wise one learns from the mistakes of others. I have benefited greatly from stories of other pilots who choose to talk about mistakes they have made. After an event I experienced in early May of 2020, it was immediately demonstrated to me that I am susceptible to the same factors as any other pilot that I have heard about in their stories. There’s just something about experiencing a scenario yourself that etches the lesson in your mind.

At the time, I was a 250-hour pilot with around 50 hours of tailwheel time, and I was flying my beautiful 1946 Stinson 108 that I love. I had purchased it in 2019 with a fresh restoration and a fresh overhaul of the Franklin 150hp engine. The weather was gorgeous that Saturday morning, and the day’s activities began with a flight of about 40 minutes from KBVX to 4M3 for a fly-in breakfast. I had decided last minute to make this trip, so I was alone.

After a great breakfast and admiring some great airplanes, I received a call from a friend who was also my flight instructor for my primary training years ago. We had been talking about going to see a Piper Apache for sale that wasn’t too far from our location, and he was ready to go have a look. He was back at the home base, but on such a beautiful day, I certainly didn’t mind picking him up and going right back past 4M3 to the grass strip where the Apache was located.

Stinson

A Stinson is a simple airplane, but it still demands discipline.

Back at the home airport, I didn’t even have to shut the engine down; I just loaded my passenger and we departed immediately. I was excited, as I had never landed my Stinson on a grass strip before. The flight was uneventful, and we made a pass over the strip to have a look and then landed. After looking at the old twin for a while, it was time to depart, and this was where I made my first mistake.

It happens that in my real job, one of my responsibilities is to establish standard operating procedures (SOPs). Relating this to my flying hobby, I recognize preflight inspection is an SOP that I definitely follow. I am normally very methodical about it. First flight of the day, the airplane gets a thorough preflight. Making a quick stop for breakfast or something like that, I always at least do a walk-around and also check gas and oil. When we left the grass strip that day, I did not.

The Stinson 108 has two piano hinges on the top cowling for easy access to the engine. Departing the grass strip, reaching about 2500 feet, I noticed one of the hinge pins had migrated out about three inches. It was bothering me, and I was considering making an unplanned stop to fix it. That’s when I happened to look down and saw a bit more pressing issue. My oil pressure was dropping fast! Of course, the two problems were unrelated, but the hinge pin already had me thinking about options for a quick landing. I reached down and pecked on the pressure gauge with my finger. Nothing changed.

It was that moment, in hindsight, that I experienced a thought that could have led to an off airport, forced landing. A thought that was so subtle it was almost not even in my conscious mind. We were at 2500 feet. I had an engine with less than 100 hours. We were probably less than thirty minutes from home base. These facts probably contributed to that insidious thought that could have led to a very different outcome. The thought was that it was probably a gauge malfunction. I wanted to believe it was only the gauge.

I’ve heard and read a lot of good advice from others when it comes to flying. Things like “stack the deck in your favor,” and, “if more than one factor about the flight is bothering you, abort.” That pesky piano hinge pin might have saved the day. That pin had migrated out a few inches toward the spinning propeller. Sure, it probably had a several inches to go (and many flight hours) before it interfered, but I didn’t like it. So I had two factors that were bothering me very much. Because of that pin, I was well aware of an airport (4M3) that was nearby to the east, and I thought it was probably within gliding distance. I pulled the power to idle and made my turn to a long final for runway 9.

I made the landing without incident, taxied off the runway, and shut down. We got out of the airplane and saw just how serious the problem could have been. Oil was everywhere! My friend, flight instructor, and passenger is also an A&P mechanic. We searched the best we could for the problem, thinking it might have been the oil pressure sensor, lines, and so on. We never could figure it out, so the airplane had to go into the shop for a closer look. It turned out to be a cracked cylinder base flange. Thankfully, that was the only damage, and a new cylinder was the extent of the repair.

Cylinder

That’s a bigger problem than just a hinge.

I’ll always think about what might have happened. More than that, I think about the subtle pressures that can creep into a pilot’s mind, like not wanting to believe there is a problem. When hearing about aviation incidents and accidents, one often hears reference to the causal chain, where it is usually a chain of events with several decision points that lead to the outcome. At any one point in the chain, if another course of action would have been taken, the outcome would have been different.

My event began with failing to adequately preflight the airplane before leaving from our short stop at the grass strip. I’m not certain, but there may have already been oil leaking at that point. Yes, I did try looking over the airplane as we were approaching it, but I didn’t open the cowling and check the oil like I normally do. I think one reason for this is I had my old flight instructor with me, who is basically retired, with probably 40,000 hours or so of PIC time. Naturally, I feel very comfortable when he is with me because of his enormous amount of experience. Maybe that led me to be a little more relaxed on the preflight.

Next, after departing, noticing the oil pressure was abnormally low, my mind was desperately trying to tell me the gauge was at fault. We weren’t far from home base and the engine had a low numbers of hours—both teamed up to convince my mind that nothing was really wrong. One official name for this is also “Plan Continuation Bias” or “get-there-itis.” It had been a great morning of recreational flying, and I was ready to put it in the hangar. At the rate of oil loss, I have no doubt we would have run out long before reaching our destination and would likely have had a forced, off-airport landing. In that case, even the best outcome would have been far worse than our unscheduled stop at 4M3.

I learned some valuable lessons that day. First, I will always, always, always, check the gas and oil after a short stop (like I normally do). I have never failed since to give the engine a quick look, no matter what. Second, if an engine gauge is telling me something is wrong, I’ll land immediately. A little inconvenience is a small price to pay to confirm the issue. We are trained to keep the engine gauges in our scan while flying. I think I always did, but now I am very intentional about it. Third, and probably most important, I learned that I (and I believe all pilots) are susceptible to these subtle external pressures, situations that cause us to act in a different way than we normally would. We are trained from the beginning about these things: the PAVE checklist, human factors, the five Ps, and so on. I had heard and read about them. I knew about them intellectually. But now, I have experienced just how those factors can creep up and just how much they should be at the front of my mind on every flight.

We all love aviation, the great rewards it provides, and we accept some amount of risk to be able to experience this passion. I’ve done a fair amount of review of the FAA literature on human factors and Aeronautical Decision Making since that day. Having experienced the event, I know I am more conscious of my own susceptibility to them. I hope it has made me a better pilot and that others can learn from my experience. Wishing everyone many more happy flights and blue skies!

Travis Hoggard
Latest posts by Travis Hoggard (see all)
9 replies
  1. Heinz Spielvogel
    Heinz Spielvogel says:

    Good decision Sir. The Stinson is a fantastic plane. I have a 108-3 now but had a -1 that also threw a jug also from cracking around the flange. The 165hp Franklins have shot peened cylinder bases and that stopped the cracking. Enjoy your Stinson Sir.

    Reply
  2. Mike Cupp
    Mike Cupp says:

    Thanks for sharing! Many lessons in your story…. Funny how complacent we can become when things “go right” over time.
    I am an Air Force Veteran- Vietnam era. Explosives and Demolition was a major part of my duties.
    It is AMAZING how flying and EOD have so many parallels! In either, if you are lucky, you might get one mistake or oversight without dire consequences.
    Everything in EOD was done by checklists, I lost friends, saw people get hurt – saying – “Ah we don’t need to check that, never had a problem before” famous last words!
    Every time I fly, I think about what skipping a step or “it’s ok – never had a problem before” can mean!
    Again…. Great lessons in your story and glad you shared it!
    Funny how lessons in life can teach us….if we will just listen!

    Reply
  3. Peter N. Steinmetz
    Peter N. Steinmetz says:

    Good lessons and nicely told. I was taught to always check tires, fuel, and oil before each flight, even after a short stop. Because if you have those and something goes wrong you will most likely survive. This story reinforces that even more for me now.

    Reply
  4. Roger Kubeck
    Roger Kubeck says:

    Travis, thanks for sharing a great learning experience. But, please, do not ever enplane or deplane anyone (even an experienced pilot) with the prop spinning. That could have been a grave error; I have read about way too many injuries in this regard.

    Reply
  5. Luis Maciej
    Luis Maciej says:

    Reminds me of the time I failed to check the air speed indicator on a preflight. The rented Piper Archer had just been washed and the person washing the plane had taped the inlet to the airspeed indicator. During taxi the air speed registered appropriately. However, few minutes after I departed and while I was practicing my IFR approaches to stay current, I lost my airspeed indicator. It registered 0 KPH. I contacted SoCal ATC and cancelled my practice approach. Fortunately I had a few hundred hours in Piper Warriors and Arches and was familiar enough with these planes where I could “wing” the plane to a landing without the absolutely needed airspeed indicator. I immediately landed at the closest airport. While at the airport I inspected the airspeed indicator inlet. What had happened was that the tape that was applied at the wash had unfastened on one side (this with the airstream configuration was not affected while taxiing initially) however while in flight the end of the tape had (flipped) covered the inlet therefore with no air flow to it, and registered 0 KPH.
    Don’t overlook any items on your pre-flight check.

    Reply

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