Angle of Attack Probe for Small Planes

 



An airspeed indicator assumes a cumulative error that’s inversely proportional to speed. In other words, error increases as speed decreases. Finally, when an airplane is flying very close to stall, an ASI may be practically useless, a quivering needle bobbing near the bottom of the gauge, reading anywhere from five to 30 knots slow. Conversely, angle of attack indicators provide a continuous readout of margin above stall right down to the actual event.

Um indicador da velocidade aerodinamica assume um erro cumulativo que é inversamente proporcional à velocidade. Em outras palavras, o erro aumenta quando diminui de velocidade. Finalmente, quando um avião está voando muito perto do stall, umindicador de velocidade aerodinâmica  pode ser praticamente inútil, um ponteiro trêmulo oscilando na parte inferior do mostrador, apontando em qualquer lugar de 5 a 30 nós. Por outro lado, indicadores de ângulo de ataque fornecem uma leitura contínua da margem acima do stall até o evento real.

FAA Clears Path for Installation of Angle of Attack Indicators in Small Aircraft

For Immediate Release

February 5, 2014
Contact: Les Dorr or Elizabeth Isham Cory
Phone: (202) 267-3883 (Les)/(847) 294-7849 (Elizabeth)

Measure Could Improve Safety in Thousands of Aircraft

WASHINGTON – The Federal Aviation Administration (FAA) today took an important step to help improve safety in small aircraft by simplifying design approval requirements for a cockpit instrument called an angle of attack (AOA) indicator.  AOA devices, common on military and large civil aircraft, can be added to small planes to supplement airspeed indicators and stall warning systems, alerting pilots of a low airspeed condition before a dangerous aerodynamic stall occurs, especially during takeoff and landing.

“Safety is our top priority, and with today’s announcement we are improving safety by streamlining regulations and cutting red tape – a win-win situation,” said U.S. Department of Transportation Secretary Anthony Foxx. 

An “angle of attack” is the angle between a plane’s wing and the oncoming air. If the angle of attack becomes too great, the wing can stall and lose lift. If a pilot fails to recognize and correct the situation, a stall could lead to loss of control of the aircraft and an abrupt loss of altitude. Stalls can happen during any phase of flight, but they are critical when planes are near the ground and have less room to recover, such as during landing and takeoff.

AOA indicators may help prevent loss of control in small aircraft because they provide a more reliable indication of airflow over the wing. Although they have been available for some time, the effort and cost associated with gaining installation approval has limited their use in general aviation. The streamlined requirements are expected to lead to greater use of the devices and increased safety in general aviation.

“We have eliminated major barriers so pilots can add another valuable cockpit aid for safety,” said FAA Administrator Michael Huerta. “These indicators provide precise information to the pilot, and could help many avoid needless accidents.”

Under the new policy, manufacturers must build the AOA indicator system according to standards from the American Society for Testing and Materials (ATSM) and apply for FAA approval for the design via a letter certifying that the equipment meets ATSM standards and was produced under required quality systems. The FAA’s Chicago Aircraft Certification Office will process all applications to ensure consistent interpretation of the policy.

The FAA believes this streamlined policy may serve as a prototype for production approval and installation of other add-on aircraft systems in the future.