British pilots are pushing for true headings to replace degrees magnetic when expressing aircraft direction and bearing. The British Airline Pilots Association and the Royal Institute of Navigation are working to persuade authorities to replace the magnetic reference system because they believe true headings are more accurate and are more cost effective operationally. Aeronautical chart provider Jeppesen (Hall 3 Stand A14) would support the change but is not actively seeking to persuade the authorities.
Today’s airliners get their direction data from computers that use inertial input. The computerized values of true headings are then modified by synthesized values of variation to give degrees magnetic, Richard Parker, vice chairman of BALPA’s aircraft design and operation group, explained to Aviation International News.
One problem with this approach is that erroneous data in the algorithms used can introduce misleading displays or data into the flight management system. Also, the continued use of magnetic direction generates costs in publishing and amending aeronautical charts, realignment of radars and navigation beacons and renumbering of runway threshold designators. “The adoption of true headings as a reference system would result in increased accuracy and substantial cost benefits to all,” said Parker.
Nonetheless, adopting true headings would entail corrective scheduled maintenance for existing legacy aircraft and some revision by chart companies.
Historically, aircraft used wet-type compasses as the sole means of navigation. Later, an indicating system using magnetic sensing was introduced to correct the output of gyros.