The 40-year-old commercial and instrument rated pilot of a Piper Cherokee Six launched on a business trip from the Lincoln (Nebraska) Municipal Airport (LNK), to the Howard County Airport in Nashville, Arkansas (M77), with five passengers aboard. Although the pilot had logged more than 600 hours total time, including more than 80 instrument hours, he was ill-prepared for the events that occurred that August morning.
It was around 11:30 a.m. local time, and already the temperature had climbed above 80 degrees Fahrenheit. There was an eight-knot breeze blowing out of the southwest, and ceilings were 1,300 broken. Visibility was five miles in haze when the controller cleared the pilot for the localizer approach at the Texarcana (Arkansas) Regional Airport (TXK). The pilot canceled his IFR flight plan and said he would continue VFR to Nashville, about 32 nautical miles north over relatively flat terrain. Nashville had no instrument approach procedure. A short time later, the pilot called ATC to report that he was in trouble. He was in the clouds, his vacuum system had failed, the turn coordinator did not work, and he was on the verge of vertigo. The controller tried to vector the pilot back to Texarcana, but the pilot was having difficulty maintaining headings. The aircraft broke up in flight, crashing and killing all six people on board. The post-crash investigation revealed that the vacuum pump had indeed failed, but it was impossible to determine whether the turn coordinator had failed on that flight or at some time prior to departure. Flying an aircraft on partial panel is a demanding task. On most light general aviation aircraft, when the vacuum system fails, the attitude indicator and directional gyro become inoperative. The altimeter, vertical speed indicator, airspeed, and power setting must then be used to monitor pitch attitude. The pilot must rely on a swinging, swaying magnetic compass for heading and use the electric turn coordinator to keep the wings level and to make turns. Sharp instrument-scanning skills are needed to stay ahead of the game. Add a failed turn coordinator to the partial-panel picture, and controlling the aircraft can be nearly impossible. Struggling to stay upright with no gyro instruments, the pilot can quickly fall victim to vertigo and overstress the airframe in an attempt to regain control. Instrument pilots are trained to make a number of checks before departing into gray skies. Indeed, these checks should be performed by every pilot before any flight, even in VFR conditions. During the before-takeoff runup, the pilot should verify proper operation of the vacuum or instrument air pump by noting the proper suction or pressure reading. During taxiing turns on the ground, the attitude indicator should show level wings, while the turn coordinator, directional gyro, and magnetic compass indicate turns in the proper direction. If any of these instruments are operating improperly, the flight should be canceled until repairs can be made. In fact, unless the aircraft?s minimum equipment list or FAR 91.213 specifically allows it, the aircraft can?t even be flown in VFR conditions with an inoperative gyro instrument. Gyro failures can make a pilot?s head spin. They, along with other instrument problems, can sneak up on a pilot. That?s what happened to the 3,000-hour ATP-rated pilot of a Piper Archer II on an IFR flight to the Westerly State Airport in Westerly, Rhode Island (WST). Ceilings were about 1,200 feet, and the pilot had been given a vector to intercept the localizer approach for Runway 7 from the southwest. Just as the localizer needle centered, the controller instructed the pilot to report established on the localizer. Although he thought it was odd that the controller, who had him in radar contact, should ask him to report established when he was already lined up on the localizer, he replied that he was established. The controller cleared him for the approach. A few minutes later, the reason for the controller?s question (actually a subtle cue) became obvious. Breaking out of the overcast, the pilot realized he was at least half a mile north of the localizer course, even though the number-one navigation radio indicated he was centered on the localizer course. The correct localizer frequency had been tuned in, the station had been properly identified, and a little white flag indicated that the receiver was operating normally. That white flag was little more than a white lie. The final approach fix for the WST Localizer 7 approach can be identified by DME, or by the intersection of either of two VOR radials with the localizer course. The pilot had tuned the number-two receiver to a cross-radial to back up his DME in identifying the final approach fix. When he tuned the number two navigation radio receiver to the same localizer frequency, it indicated full scale deflection to the right. Prior to the flight, a VOR check had indicated the two navigation receivers were operating within required limits. Although a sensitivity check is not required, it?s unclear whether the sensitivity of the number one navigation receiver had been tested. (See the sidebar.) Had the pilot inquired as to the nature of the controller?s request, or tuned his second navigation receiver to the localizer, he might have detected the error much sooner. Fortunately for him, the ceilings were high, and he was familiar enough with the area to recognize the error. Two pilots flying a VOR approach in a non-radar environment were not so fortunate. It was an almost imperceptible mistake that cost them their lives. A single button on their navigation receiver could switch modes between area navigation (RNAV) and VOR, and small letters on the face of the receiver indicated which mode the unit was in. The pilots were flying in mountainous terrain in instrument meteorological conditions, and the VOR receiver had mistakenly been set in the RNAV mode instead of the VOR mode. The aircraft was miles off course when it slammed into terrain, killing all aboard. While pilot error was listed as the cause of the accident, the design of the receiver certainly played a part in the events leading to the crash. Had the display been better designed, the pilots might have realized their mistake before they attempted the approach. Many navigation receivers aren?t designed to account for basic human factors. The VOR or localizer and glideslope needles of many receivers are designed to center when the receiver is turned off or not receiving. If the signal is lost or the receiver fails during an instrument approach, the needles may center, indicating to the pilot that he is precisely on course. The only hint of a problem might be a red warning flag indicating the receiver is not receiving. As these receivers are exposed to years of sunlight, the red flag can fade so much that it appears white, especially in the dim red cockpit lights on a night flight. Such a problem might easily lead a pilot to crash short of the runway. One of my flying mentors perhaps said it best: If the instruments look good, look again. Check everything, and cross check again. Even the little white lies told by our instruments can put us far off course and squarely in the face of danger.