Angle of Attack
Angle of Attack The “Angle of Attack” is the angle between a plane’s wing and the oncoming air (relative wind). 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.
More than 25% of GA accidents occur in the maneuvering phase of flight. Half of those accidents involve stall/spin scenarios. 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.
What is an AOA Indicator?
We often discuss stalls with respect to airspeed and that can be a problem. Part of that problem is that stall speed changes with the aircraft’s configuration (e.g., cruise, landing, etc.) Also, as an aircraft’s load or weight increases, so does its stall speed. Using an AOA indicator can help prevent a stall as it provides a more reliable indication of airflow over the wing, regardless of its configuration. Without it, AOA is essentially “invisible” to pilots.
An AOA indicator can help when used in conjunction with airspeed and existing stall warning systems, when available. It can be used to get the pilot’s attention (via audio and/or low cost stick shakers) even if the pilot is not looking at it. This focuses the pilot’s attention on where it needs to be to avoid the stall.
How Can I Equip with an AOA Indicator?
AOA indicators have recently become more available and affordable for GA aircraft. The FAA’s Small Airplane Directorate has helped with this by streamlining the process for production and retrofit approval of AOA devices.
A New Angle on Safety
AOA systems offer many benefits to safe flying so consider looking into one for the aircraft you own or fly. And if you do install one, make sure you’re familiar with its operation and limitations. It’s also a good idea to keep your skills sharp through practice of stalls and slow flight as well as pattern and instrument work with a CFI. Be sure to document your achievement in the Wings Proficiency Program too. It’s a great way to stay on top of your game.
Resources
FAA news release on streamlining the AOA installation process for small aircraft: http://go.usa.gov/cgu2Y
FAA policy on AOA installation: http://go.usa.gov/cgu95
Safety Enhancement Fact Sheet on AOA Systems: http://go.usa.gov/cgu8w
FAA Airplane Flying Handbook — Engine Inoperative Flight Principles for Multiengine Airplanes (Chap 12, pgs 23-31): http://go.usa.gov/cguEQ
“A Finesse for Vitesse: Mastering the Maze of V-speeds” May/June 2015 FAA Safety Briefing www.faa.gov/news/safety_briefing/2015/media/MayJun2015.pdf
