In his memoirs, Gen. Chuck Yeager relates to a story where the flight didn’t go according to plan, or his expectations. As a young USAF test pilot, he was asked to fly the then new F-86 Saber to determine why several had unexpectedly crashed. Several Sabers had last been seen flying at low altitude, inverted before crashing with no survivors. Yeager mounted his Saber to determine the cause of these tragic accidents. I short order, he had his answer. Once inverted, the ailerons on his Saber would lock up and become immovable. Once the aircraft was rolled right-side-up, he regained aileron control. Upon detailed inspection after the flight, it was determined that a crucial bolt in the aileron assembly process had been installed incorrectly, leading to the jamming of the controls when inverted. When the manufacturing process was inspected at North American Aviation, it was determined that a factory worker was installing the bolts upside-down, because they were installed that way on every other NA aircraft he had built in his lengthy career at NA (P-51, T-6, etc.).
How often do we simply activate a system in our aircraft, program a procedure into our FMS/GPS, or select an AP function without truly verifying that action did indeed take place? Or, did we just assume that it acted as we expected because “it’s always worked that way before”! As an instructor in a variety of aircraft, I’ve recreated issues for customers to see if they will catch a problem before is becomes critical. One of my favorites to recreate is a flap failure. In many aircraft, there is no warning to inform the pilot that his/her flaps did not deploy or retract as expected. We simply move the lever and expect the flaps to work because they always worked in the past. Yet, most of us never check to ensure that the flaps moved to the desired position. Furthermore, despite mounting indicators that something is amiss (unusually higher airspeeds, unusually flatter approach attitudes, etc.) we press on thinking everything is fine. In fact, we’re so certain that everything is fine, we’ll logically explain away the abnormalities to cross winds, heavier loads, density altitude, or some other convenient excuse.
Last week, I fell into this very trap while flying a TBM. A fellow instructor was flying right seat and had my permission and encouragement to challenge me during our flight. He slyly waited until I was fully engaged on a GPS approach. He pulled my ADC #1 circuit breaker, my gear pump circuit breaker, and my flap circuit breaker. Then, he sat back to watch what would happen. I caught the ADC and gear issues immediately, but completely missed the flaps! Sure, I did the GIFY check three times during my approach. I called flaps TO and flaps LAND when they were so selected. I even convinced myself the aircraft had decelerated, as expected. However, it wasn’t until I was well into the maneuvering portion of a circle-to-land approach into MIE that I began to get that funny feeling that something was amiss. The TBM was faster, was turning wider, felt heavier, and was very flat pitched. While comfortably above Vs and with altitude to spare, the landing was completed without difficulties. However, I can only imagine where my stall speeds were as I maneuvered for the landing. Probably closer than I would have preferred.
I had been bit by the expectancy of the flaps’ operation. I moved the handle, they surely worked! I even called out the appropriate checklist for landing; and completely missed my non-existent flap settings. I placed myself and my aircraft much closer to the stall regime than I should have while maneuvering in the circle-to-land.
The moral of the story is this, don’t just assume your actions have occurred as you planned. Confirm your action has happened. Visually verify the flap handle, indicator, and flaps themselves have moved. Examine the flight plan page to ensure it is the routing your expected and/or have been cleared to fly. Ensure the AP is doing exactly what you expected it to do. If you’re not sure about a clearance, ask for a clarification. Are the deicing systems working as designed, properly sequencing thru their allotted timers? Does my fuel consumption and remaining load make sense? Does my aircraft and engine performance make sense for a given flight condition. If so, great! If not, then why not?
As has been said in the past, “Trust, but verify”!!
- Todd Shoup