Harford County Airport
Aircraft Accident/Incident Report

Jacksonville, Maryland 21131
Saturday, March 24, 2007 9:19 EDT

The instrument-rated private pilot obtained a weather briefing and filed an instrument flight plan for a personal flight that would occur the following morning to attend a stock car race. On the morning of the accident, the pilot contacted air traffic control (ATC) to obtain an instrument clearance. The pilot was given a clearance and was told that it would be void in 10 minutes. Two minutes prior to the expiration of the ATC void time, the pilot departed. Recorded non-volatile memory (NVM) data from the electronic cockpit flight display system were downloaded and analyzed by investigators, and these data greatly aided in the investigation. Analysis of the data indicated that, while climbing in instrument conditions, and most likely using the autopilot, the pilot attempted to increase the airplane’s climb rate by using the vertical speed bug on the electronic (glass) Primary Flight Display (PFD) in the cockpit. However, the NVM data revealed that the PFD had failed to “align”, and was not fully functional. As a result of the PFD not being aligned, the bug settings (altitude and vertical speed) were suppressed, and not transmitted to the autopilot computer. Therefore, when the pilot attempted to increase the airplane’s vertical speed using the PFDs vertical speed bug, the changes were not transmitted to the autopilot computer and the autopilot did not command an increase to the rate of climb. Subsequently, the rate of climb momentarily increased twice, most likely due to pilot control inputs via the control wheel. (A review of the PFD Pilot's Guide revealed that it does not provide information to the pilot regarding the suppression of the bug settings when the PFD is not aligned.). Soon after the last vertical speed bug change, the airplane’s vertical speed began to fluctuate (and oscillate between climbing and descending) significantly. These fluctuations continued for the remainder of the flight (about 9 minutes). During this period, the airplane completed three left-hand orbits at varying altitudes. The pilot then reported an “autopilot problem” to ATC, and he requested a clearance to divert to a nearby airport. The airplane’s course deviated again to the left, after which the pilot again reported a problem with the autopilot. The airplane continued to fly for another 4 minutes as the vertical speed continued to oscillate. The airplane’s ground track remained erratic and was not consistent with a course toward the diversion airport. The airplane entered an uncontrolled descent, impacted terrain, and was destroyed. Examination of the wreckage revealed that the pitch trim jackscrew was in the full nose-down position. No preimpact malfunctions of the autopilot or flight control systems were discovered. The nose-down trim condition likely resulted from the pilot pulling on the control wheel with the autopilot engaged which would have resulted in the trim running nose down. Exams of the airplane’s other systems, structure and engine did not reveal any evidence of preimpact malfunctions or failures. Risk factors for spatial disorientation were present at the time of the accident, including IMC and maneuvering flight. Analysis of the airplane’s flight path during the accident flight, and the pilot’s communications with ATC, indicates that the pilot became spatially disoriented while attempting to maneuver with reference to a degraded PFD. The pilot was instrument current and qualified and he had accumulated about 291 hours operating the electronic flight display system. He had received formal training in two models of airplanes equipped with the same flight display system, and also experienced a failure of the display system on a previous airplane. Thus, the pilot was likely familiarized with the functionality of the PFD. Analysis of the NVM data from the PFD revealed that the PFD had not aligned during its “power cycle” of the accident flight, nor had it aligned on the previous power cycle that occurred on the day of the accident. The recorded data do not explicitly indicate the reason for the failure to align on either cycle; however, the previous power cycle was 333 seconds in duration, and the data indicate that the airplane was moving (taxing) at that time. Movement during this initial, critical alignment phase hinders the system’s ability to align as it attempts to calculate the steady state bias of its rate sensors, and the PFD screen will display a message that states: “INITIAL AHRS ALIGNMENT / REMAIN STATIONARY / OK TO TAXI in xx SECONDS”. After the 333-second power cycle, the system was shut down and restarted for the accident flight. No movement was recorded during the critical alignment period of this power cycle, although the airplane did taxi during the “OK TO TAXI” period of the alignment sequence. The investigation could not conclusively determine why the PFD would not align; however, the airplane departed 375 seconds after the PFD power cycle start-up, which may not have been sufficient time for the system to align. Typical time to align while remaining stationary is 166 seconds. The time to align when taxiing during the “OK TO TAXI” period varies considerably, based on the taxi motion and duration. During a previous taxi event that was similar to the one on the day of accident, the time to align was 416 seconds. According to the flight display manufacturer, the failed alignment in both power cycles would have resulted in red X’s being displayed on the PFD. Based on the information recovered from the accident unit, it is likely that red X’s were displayed at the time of the takeoff. Regardless, the airplane was equipped with traditional standby flight instruments (specifically an attitude indicator, an altimeter, an airspeed indicator, a magnetic compass), and dual global positioning systems, which should have provided sufficient information for the pilot to have maintained situational awareness to allow for continued safe flight after failure of the PFD. The investigation revealed a history of numerous failures of multiple types that affect the flight display system’s reliability. Additionally, examination of the accident airplane’s magnetometer also revealed evidence of fretting corrosion in flight critical components which could result in further malfunctions and failures. However, the investigation did not confirm whether any malfunction or failure of the electronic flight display system was present at the time of the accident takeoff, other than the PFD’s failure to align prior to departure.

The pilot's failure to maintain control of the airplane which was a result of spatial disorientation after takeoff into instrument conditions with an operationally degraded electronic primary flight display. Contributing to the accident were the pilot’s failure to properly utilize the airplane’s standby flight instruments, the electronic primary flight display system’s unaligned state prior to takeoff for undetermined reasons, and the pilot’s lack of knowledge of degraded autopilot functions with an unaligned primary display system.