Historical and recent accidents and incidents have highlighted the risk associated with unreliable airspeed (URA) events. These events are normally transient in nature and can cause multiple, seemingly unrelated warnings and failures. The following philosophy and guidelines are provided to assist in reducing the risks associated with URA events.
URA Philosophy
- The keys to successfully dealing with a URA event are recognition, procedures, and training
- The aircrew’s recognition of and initial reaction to a URA event are critical
- Manufacturers should attempt to ensure unreliable airspeed events are clearly identifiable to aircrews
- The most important function of the aircrew during an in-flight URA event is to maintain control over the aircraft’s flight trajectory and energy situation by selection of attitude and power settings so that the aircrafts flight parameters remain within normal limits
- Crews should be aware of the instruments and critical systems that are not affected by a URA event (e.g. Attitude displays, engines)
- Procedures and training for URA events should include the effect of a URA event on other aircraft systems, and potential alerts/warnings and indication system inaccuracies that could be expected
- Crew coordination and communication are important elements in successfully addressing a URA event
URA Guidelines
- URA procedures should provide information on attitude and power settings that enable crews to maintain the aircrafts flight parameters within normal limits during in-flight unreliable airspeed events for all phases of flight
- URA procedures should address the availability and use of independent alternate sources of airspeed information (e.g. GPS, inertial, angle of attack, etc.)
- URA procedures should include memory items for critical immediate action steps
- Training programs addressing URA should exist at beginning (ab initio/MPL), initial, and recurrent levels
- URA training should include both simulator and academic phases