You’ve learned that the rudders on Twin Commanders are disconnected from the steering, and because of this you should always install the rudder gust lock on the ground. Here’s what happens when you don’t…
Because the rudder has no physical restrictions other than the modest cable friction between the pedals and the actual rudder, even a light puff of wind will deflect the rudder on the ground if it isn’t restrained. So, on every Twin Commander it’s critically important to install the rudder gust lock as soon as the aircraft is secured on the ground. This simple precaution will prevent what happened to my airplane, N690GG.
Last year I leased the plane to the owner of a firm and its two professional pilots for flight instruction. My insurance company approved dual flight instruction in the aircraft, done under the tutelage of an approved instructor, during the short-term lease. The arrangements and insurance coverage completed, I delivered N690GG to the destination airport. I left it on the ramp at with all gust locks, pitot tube covers, and sun screens installed.
The training pilots and instructor took possession of the aircraft early the next week and flew for about seven days. I came the following week to pick it up. During the visual inspection I noticed in the interior neither the elevator/aileron lock nor sunscreens were in place, but on the exterior the pitot covers and rudder gust lock were. I did not notice anything wrong, but it turned out there was substantial hidden damage, including a broken rudder torque tube and buckling of the rudder skin.
You cannot see into the rudder, nor inspect the attach points to the rudder torque tube, because they are hidden from view. I did not see buckling of any exterior skin at that time.
In retrospect, on the preflight I would not have noticed any buckling as I wasn’t looking for it specifically, and unless you looked at the rudder skins in a certain light the buckling was nearly invisible.
I moved the rudder and didn’t feel any binding, but also didn’t feel any resistance.
In retrospect, the torque tube, which was half broken off, could have been completely broken off and the rudder might have felt the same way as I pushed it back and forth with my hand. Since there is no connection between ground steering and the rudder system, the slight resistance felt when you move the rudder by hand is due to cable connections between the rudder pedals and the rudder itself.
Taxiing a Twin Commander does not invoke the rudder as steering is controlled by pressing the top of the pedals, which brings the hydraulic nosewheel steering into play. Thus, while taxiing, the rudder is not used or involved, and you get very little rudder feel unless there is a stiff crosswind or tailwind. There was none that day.
In retrospect, even if the entire torque tube had been broken, on that day no amount of taxiing or pushing on the rudder pedals would have revealed any damage on the ground.
Winds were very light, about six miles per hour straight down the runway, so takeoff was uneventful. Use of the rudder in the air was an entirely different matter, however. As I climbed out and trimmed the aircraft, I noticed less rudder authority than was normally available.
In retrospect, it was at this time that I first became aware of something going on with the rudder, even though I didn’t know what it was.
I continued to notice limited rudder authority at cruise speed, about 200 KIAS. More rudder authority was available as I landed at my home airport.
In retrospect, this made sense, as decreased air loads on the rudder made it easier to deflect into the slipstream.
So what the heck happened? Any experienced Twin Commander mechanic will tell you a competent pilot won’t break the torque tube in flight from bashing the rudder against the stops, because air loads prevent this at cruise speeds. At slower speeds, such as in the landing pattern, stomping on the rudder may skid the aircraft to a point of stall, but normally it still won’t break the torque tube connection.
While under my control, N690GG was not subject to jet blasts, strong gusts, strong tailwinds, or any other unexpected side loads on the rudder at any point from preflight to takeoff. I didn’t forcibly stomp on the rudder pedals while taxiing, as that has no effect on steering.
Once on the ground at my destination, I attempted to examine the rudder and check its travel limits. A lineman observed the rudder travel, which was not to the stops.
In retrospect even while looking carefully at the rudder surface, I didn’t notice buckling or, if I did notice it, I never thought there was anything out of the ordinary. Furthermore, by myself I couldn’t ascertain if the rudder was damaged, even with the visual help of the lineman.
How did I finally notice it? I called my experienced mechanic, who walked me through a specific diagnostic and visual inspection. It was then that he, not me, made the determination that the torque tube was partially broken. Even after my nearly 200 hours in the plane, I didn’t diagnose the problem, even on a very calm, non-eventful flight. I simply suspected there might be something wrong.
How did the rudder get snapped off from the torque tube? The severity and nature of the damage points to a blast of wind on the ground, not ham-fisted flying. It happened apparently because of failure to install the gust lock during the time the aircraft was not in my possession. Does that make me feel any better? No. Does not being able to diagnose a potentially very dangerous situation make me happy? Absolutely not.
The only good thing to come of the incident was having the right insurance through NationAir, and a competent and attentive Twin Commander Authorized Service Center to come to my rescue.
My service center sent a plane over with mechanics who inspected the rudder, made temporary repairs, then flew it to their shop for complete inspection and permanent repairs. What service! I hope and trust you will have the same level of support and service from your service center.
The moral of the story: Don’t forget your gust lock. Otherwise, you may be torqued off, too!
Glenn Kautt is vice chairman of a wealth management firm with offices in Virginia, Illinois, Wisconsin and Florida. He received his MBA from Harvard Business School and is a President’s Distinguished Scholar graduate of Purdue University. Named repeatedly as one of the nation’s top investment advisors by Barron’s, Worth, Mutual Funds, Washingtonian, and Medical Economics magazines, Kautt is a regular columnist for Financial Planning magazine and has written and spoken professionally on business and advanced financial planning topics for over 30 years. He received his ATP in his Twin Commander almost 40 years to the day after his private certificate. He also holds a commercial ASES certificate. He considers his Twin Commander to be a fantastic business tool.