|The NTSB conducted a study of accident data between 2002 and 2008 noting that there were 266 total accidents of which 141 occurred with conventional instrumentation and 125 occurred with glass cockpits. This amount of data was deemed sufficient to make statistical comparisons. The first startling statistic was that 16% of accidents for light aircraft with conventional instruments resulted in fatalities while 31% of accidents for light aircraft with glass cockpits resulted in fatalities. Most of the conventionally equipped aircraft were being used for instruction with short, local flights under VFR conditions. On the other hand, glass cockpit aircraft were used more on longer flights with more being in IFR conditions. Being old school I had imagined that the most serious problem would be the screens going black; however, it appears that is not the real problem. Apparently the displays remain lit but the data received and displayed is either erroneous or missing. The image on the right shows the airspeed indicator is vibrating between 80 knots and 125 knots.
The NTSB report noted that because there is a wide variation in the design of glass cockpit avionics systems between manufacturers and software based systems can be modified easily, which may result in upgrades being installed without adequate training on the changes. On the left is an example of a Primary Flight Display which has experienced the failure of Airspeed, Altitude and Vertical Speed information. Imagine yourself flying along in instrument conditions and all at once this information disappears from your primary flight display. If it is on autopilot what effect does a failure of this kind have?
How quickly would the pilot notice the display is missing essential information? What if it happened during an approach to landing when the workload is heaviest? Do pilots get distracted from flying the aircraft trying to sort out what the display failure is? How quickly does the pilot move to backup instrumentation?
An additional issue is that the FAA has an SDR (Service Difficulty Reporting) system requirement for Part 121, 135 and 125 aircraft, but not for General Aviation aircraft. This makes it impossible to track equipment reliability for these aircraft. The report cited an accident that occurred on 1-15-2005 in which the PFD (Primary Flight Display) in the aircraft had been replaced multiple times, the pilot reported an unspecified avionics problem, and lost control of the aircraft in IMC (Instrument Meteorological Conditions) resulting in a fatal accident. This discussion will continue tomorrow, but in the meantime you can download the NTSB Glass Cockpit LSA Report here. If you have any experiences with glass cockpits, or have any comments, please share them with us in the comments section below. I am sure all of us would appreciate them. Until next time keep your wings straight and level Hersch! JetAviator7 The hard, inescapable reality is that anyone who flies may die in an airplane. — Stephen Coonts