Earlier this year, the National Transportation Safety Board (NTSB) added the prevention of loss of control accidents in general aviation to its Most Wanted List, a list of advocacy priorities the organization releases yearly.
Loss of control accidents (stalls, spins, etc.) made up 40 percent of fatal fixed wing general aviation accidents between 2001 and 2011, according to NTSB statistics. More than 25 percent of all fatal general aviation accidents occur during the maneuvering phase of flight, and more than half of these maneuvering accidents result in a stall/spin scenario. The NTSB continues to emphasize an industry-wide need to focus on preventing these accidents in order to reduce the accident and fatality rates for general aviation pilots. Preventing loss of control accidents should include awareness, as well as educating and training pilots, says the NTSB, and the organization is taking their own advice - in October the agency will host a forum to discuss some of the ways the industry can improve. The topics of discussion will include a statistical review, new training techniques, and equipment and technology improvements, and will most certainly include the installation and use of angle of attack (AOA) indicators in light general aviation aircraft.
Over the past few years, the NTSB, FAA and General Aviation Joint Steering Committee (GAJSC), with support from industry groups like AOPA, have been working together to advocate the use of AOA indicators in light airplanes as a way to encourage recognition and prevention of stall accidents. In the past, pilots and aircraft owners haven’t been all that eager to install them, though, based on cost and the red-tape problems associated with the installation process. In 2014, the FAA streamlined the process of installing AOA indicators, making it easier for aircraft owners to enjoy their benefits.
We know that a stall will occur any time the wing’s angle of attack - the angle between the chord line and the relative wind – exceeds its critical limit. But historically, pilots have been trained to monitor and fly precise airspeeds in order to prevent stalls. This is helpful, but only when the aircraft is in straight and level, coordinated, unaccelerated flight, when the aircraft’s stall speeds are quite low and where they are known and familiar for that particular flight configuration. But an aircraft can – and will - stall at any airspeed, any weight, any configuration, and any attitude when the critical angle of attack has been exceeded. While airspeed is a good guideline to use, it shouldn’t be the only one. Pilots should understand that the angle of attack, which is invisible, matters much more than the airspeed.
Enter the much talked about angle of attack indicator. It’s designed to help pilots determine the aircraft’s true angle of attack in real time, allowing the pilot to “see” the angle of attack in a way that’s not possible otherwise. This will be especially valuable to new pilots, who, through its use, will better understand the concept of angle of attack as it relates to different aircraft configurations and phases of flight.
So what will it take to install an AOA indicator? According to this article on AvWeb, not much. After the FAA approved the more streamlined process, most general aviation aircraft will not require an STC and the modification can be done by any A&P mechanic with just a logbook entry. AOA indicators for small general aviation aircraft like the Cessna 172 cost between $400 - $2000, depending on whether it’s electrical or mechanical, heated or not, pressurized or not, and other variables.