Safe Landings - November 2011
Upside Down and Backwards
One of several versions of the origin of “Murphy’s Law” contends that the Law’s namesake was Captain Ed Murphy, an engineer at Edwards Air Force Base in 1949. Frustration with a transducer which was malfunctioning due to an error in wiring caused him to remark that—if there was any way that something could be done wrong, it would be.
Recent ASRS reports indicate that Captain Murphy’s Law was in full effect when several aircraft components managed to get installed upside down or backwards.
Pernicious Panel Placement
An aircraft Mode Selector Panel that “looks the same” whether right side up or upside down, and that can be readily installed either way, is a good example of a problematic design. Confronted with an inverted panel, this Cessna 560 Captain found out what happens when the wrong button is in the right place.
• During the takeoff roll, the First Officer called for rotation and I pulled back on the yoke and focused my attention on the V-bars. Instead of finding the bars above the horizon as expected, they were on it. I reached up and pushed the upper left Selector Panel button again, but the bars did not spring into place as anticipated. I glanced back at the panel and, for the first time, realized that it had been installed upside down. Looking across, I found the First Officer’s side was upside down as well. We returned to the airport and reported the discrepancy to our company.
Upon reflection, I realized that I’ve become so accustomed to the panel that I may no longer read the writing on the buttons; I just press the place where that button should be. Instead of pressing HDG, I pushed VS on the inverted panel. The faulty installation escaped the attention of two Avionics Technicians, one Quality Control Inspector and, of course, both pilots. The panel looks exactly the same whether right-side up or upside down except for the labels. I find it surprising that it was designed in such a way that it could be installed incorrectly.
Although the aircraft had just come out of maintenance, there seemed no logical reason for giving extra attention to the Mode Selector Panel since none of the maintenance directly involved avionics repair or installation. We later learned that the panels had been removed during the replacement of the nose fans.
If anyone had asked me if I observe the Mode Selector prior to pushing a button, I would have assured them that I do. Since this incident, I’ve come to notice how often I (and I suspect most people) rely on “standard position placement.” The lesson is obvious; be more observant. I also question the wisdom of manufacturing a part that is capable of being installed incorrectly.
The Downside of Upside Down
Without detailed instructions and clear notation, nearly symmetrical parts can be installed incorrectly. Faced with the replacement of such a part, this CRJ 700 Maintenance Technician wound up with a case of component “misorientation.”
• The aircraft returned to the field due to the landing gear not retracting. Previously, the nose landing gear torque links had been replaced to fix a nose wheel shimmy problem. While installing the torque links, the lower assembly was installed upside down. The lower torque link assembly looks similar upside down to the way it does right-side up. The Maintenance Manual does not specify anything about the orientation, nor is there any indication on the part itself. I feel that if there had been a specific note that the part is able to be installed upside down, I would have paid closer attention to the orientation. The operational check of the installation did pass, but it does not require a gear swing. A note should be added in the installation task noting that the part is able to be installed incorrectly and that it looks close to the correct installation.
Bonanza Blunder
In order to mount a Beech 33’s ailerons on the wrong wings, a resourceful paint shop crew had to mount the ailerons upside down and use incorrect hardware. The achievement may have been dubious, but the confirmation of Murphy’s Law was unambiguous.
■ After the rudder was balanced and reinstalled, I preflighted the aircraft and flew it back from the paint shop to [our base]. The only problem with the flight was that the aircraft wanted to make a shallow left bank when the controls were released.
I looked at this aircraft two days in a row and preflighted it twice. Our Chief of Maintenance walked around it and another Instructor Pilot from the flight school also looked it over and none of us realized that the ailerons were installed incorrectly. A Maintenance Technician noticed that the location of the static wicks was wrong. The wicks were attached to the top surface of both ailerons and should have been mounted on the lower surface. This made it obvious that the ailerons were installed wrong; the left aileron was installed upside down on the right wing and the right aileron was installed on the left wing. Incorrect hardware was also used for the installation. I did not believe you could install the ailerons incorrectly and still be able to control the aircraft properly.
