In 1998, pilots from several professional pilot unions stated in public forum that the current ASOS paradigm is inadequate for providing the accurate temperatures necessary to maximize the payloads of today's commercial airliners. This study addresses the question of the adequacy of current practices in which ASOS provides an official temperature for the airport based on hourly observations. Although the ASOS samples and records the temperature many times during the hour, only the last official observation is available to the pilot, and this temperature is then used at the airport for takeoff performance computations for all aircraft. There is no criterion to issue a special observation for a large temperature change. Frontal passages and diurnal heating and cooling can create temperature differences between the actual temperature and the last observation that exceed the parameters for some aircraft performance computations. In that situation, operational impacts of planning takeoff based on the last hourly observation range from unsafe conditions that, in the extreme, may preclude takeoff, to loss of cargo capacity and passenger revenue. This study documents these impacts on civilian aviation and extends the study to consideration of military cargo aircraft. During the summer of 1998, temperature records were collected for a selection of airports with joint military and civilian operations, limited runway lengths, and high operational counts. The authors recorded the magnitude of temperature changes between hourly observations and worked with military and civilian aviation organizations to document operational impacts of the current practice of providing only hourly temperature observations to pilots. Results suggest the safety and cost-effectiveness of aircraft operations may be enhanced by providing pilots with access to real-time ASOS temperature data
The 8th Conference on Aviation, Range, and Aerospace Meteorology