A recent policy change from the Federal Aviation Administration has eased the way for installation of Angle of Attack indicators in small, privately owned aircraft throughout the U.S.
The indicators, which are widely available from multiple manufacturers, can be used by pilots to help avoid loss of control, the leading cause of aircraft fatality accidents in the U.S. The indicators constantly display the aircraft's angle of attack, or the angle of the aircraft's wing relative to oncoming air -- information that can help a pilot avoid an aerodynamic stall and subsequent loss of control.
In Alaska, loss of control has led to 13 fatality accidents since 2009 including at least three last year. Several probable cause accident reports from 2013 are still pending, which may result in a revised number of loss of control accidents. Such a loss of control at low altitude is commonly referred to in the state as a "moose stall," referring to the practice of flying low and slow while looking for moose. Aircraft stalls at low altitude nearly always result in a crash.
"The only way to avoid loss of control at low altitude is to prevent it," explained Harry Kieling, chairman of the board of the Alaska Air Safety Foundation in a recent email. "The problem with attempted recovery is it is unlikely at low altitude regardless of skill and proficiency."
Studying loss of control is nothing new in the field of aviation safety.
"Loss of control has been around a long time," explained National Transportation Safety Board member Earl Weener, from Washington, D.C. "Pilots have often regarded it as something they would not do personally."
This tendency to believe loss of control is something that happens to other pilots means that after basic pilot training, recovery from loss of control is rarely practiced in the air or flight simulators among general aviation pilots. But the overwhelming number of fatality accidents attributed to it -- 444 general aviation accidents between 2008 and 2012 -- has made it a primary target for groups determined to increase aviation safety nationwide and led to the recent policy change.
The General Aviation Joint Steering Committee was initially formed as part of the Safer Skies initiative in the mid-1990s. It had gone dormant in the intervening years, however, and was re-established in 2011. The JSC then formed multiple specific working groups of aviation professionals which included representatives from government, industry and user groups like the Aircraft Owners and Pilots Association and the Experimental Aircraft Association. The Loss of Control Work Group studied 30 different accidents and came up with 28 different safety enhancements.
The group's report was released in September 2012 and included the recommendation that "To reduce the risk of inadvertent stall/departure resulting in LOC accidents, the GA community should install and use AOA based systems for better awareness of stall margin."
Angle of Attack indicators are not new technology, but in the past they have required an extensive and time-consuming amount of paperwork like a Supplemental Type Certificate or 337 form to install, all at a prohibitive cost. Consequently, few general aviation pilots utilized them in their aircraft.
"The working group found that Angle of Attack systems have great influence on loss of control accidents but the cost was prohibitive," explained Weener. "The EAA pointed out that it was cheaper however for experimental aircraft. It worked, but wasn't being used (by general aviation) because of cost."
"The group had to figure out a way to improve safety using this system and discussed how that required policy change at the FAA who worked to accomplish that."
In the press release announcing the policy change the FAA stated:
"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."
Now the indicators, which can be mounted easily within the line of sight on the glareshield, are much more affordable and can take only a few days to install by a certified mechanic. By alerting pilots when they are nearing a critical angle of attack either by color changes and/or audible messages, the AOA gives pilots time to adjust the angle before an aircraft stall occurs. It is unnecessary to input any information into the indicator reflecting changes in payload from trip to trip; the indicator automatically compensates for those changes and any others relating to pitch, bank and other factors.
Adam White of the Alaska Airmen's Association likened the recent policy change process to the work done to ease the installation of shoulder harness seatbelts in general aviation aircraft several years ago.
"The safety benefits couldn't be ignored," White said in a phone interview. "Now we need to fight the public perception [about AOA] that it is still complicated to install."
"It's a great technology," he continued. "It really gives you the ability to instantly know what you are doing."
Aircraft owners and maintenance professionals who have questions about Angle of Attack indicators after reviewing the FAA policy change, should contact their local Flight Safety District Office for assistance. Aviation Week & Space Technology has also written extensively on the policy change.
By COLLEEN MONDOR