Aug 27, 2014

A recent Information for Operators (InFO) bulletin issued by the FAA emphasized the agency’s support for the voluntary installation of angle-of-attack (AOA) indicators onboard general aviation aircraft, in conjunction with airspeed indicators and stall warning systems, as an important step toward reducing fatal inflight loss-of-control accidents caused by aerodynamic stalls.

Once seen primarily on large turbine-powered aircraft, a variety of lower-priced AOA indicators have recently become available for installation in smaller general aviation aircraft as well. An AOA indicator provides a visual reference to the angle of the wing relative to the flow of air over the wing’s surface; exceeding the critical AOA, regardless of airspeed, may result in an aerodynamic stall.

The InFO builds upon earlier guidance from the agency’s Small Airplane Directorate and Aircraft Maintenance Division specifying that installation of AOA indicators does not require supplemental type certificate authorization in most cases.

“The objective of AOA-based displays is to provide input to the pilot as a crosscheck to standard required instrumentation,” noted the July 25 InFO bulletin. “AOA indication may improve pilot situational awareness to avoid exceeding the critical AOA, and thus reduce the risk of an inadvertent stall.”

Doug Carr, NBAA’s vice president for regulatory and international affairs, welcomed the availability of AOA indicators across a wider spectrum of general aviation.

“It is our strongly held belief that greater available information, and the proper training for pilots to disseminate that information, will help pilots to avoid stalls,” he said.

NBAA hopes that the FAA’s streamlined process [as outlined through the Small Aircraft Revitalization Act of 2013, legislation to dramatically enhance the certification process for new light GA aircraft and avionics] will aid the certification and installation of this safety tool benefitting the light end of GA, Carr added.

The move to install AOA indicators follows a review of 2,752 fatal GA aircraft accidents from 2001 through 2010 by the General Aviation Joint Steering Committee (GAJSC), of which NBAA is a member. The committee determined that inflight LOC accidents accounted for approximately 40 percent of those fatal accidents, and that AOA indicators could give pilots critical information needed to avoid an inadvertent stall.

“The availability and installation of these devices is only part of this process,” Carr reiterated. “This new policy also makes clear that pilots must receive the proper training to understand the information provided by AOA indicators at critical phases of flight.”