Wright State University CORE Scholar International Symposium on Aviation International Symposium on Aviation Psychology - 2009 Psychology 2009 Proposing Attitude Indicator Modifications ot Aid in Unusual Attitude Recovery Nathan B. Maertens Follow this and additional works at: https://corescholar.libraries.wright.edu/isap_2009 Part of the Other Psychiatry and Psychology Commons Repository Citation Maertens, N. B. (2009). Proposing Attitude Indicator Modifications to Aid in Unusual Attitude Recovery. 2009 International Symposium on Aviation Psychology, 349-354. https://corescholar.libraries.wright.edu/isap_2009/57 This Article is brought to you for free and open access by the International Symposium on Aviation Psychology at CORE Scholar. It has been accepted for inclusion in International Symposium on Aviation Psychology - 2009 by an authorized administrator of CORE Scholar. For more information, please contact [email protected]. PROPOSING ATTITUDE INDICATOR MODIFICATIONS TO AID IN UNUSUAL ATTITUDE RECOVERY Nathan B. Maertens University of Illinois at Urbana-Champaign Savoy, Illinois Pilots’ inability to recover from unusual attitudes (UA) is a major factor in loss of control in-flight (LOCIF) accidents, the largest cause of commercial aviation fatalities (Boeing, 2008). One study found 58% of professional pilots and 72% of general aviation pilots were unable to recover from LOCIF upsets (Regional Aviation News, 2008). Statistics also show that LOCIF is the only fatal aviation accident type not to appreciably decrease over a 21 year period ending in 2002 (Sumwalt, 2003a). A revision of the attitude indicator (AI) is proposed to examine if this would reduce the problem by keeping pilots from flying into UA, accelerate UA identification and enhance recovery. The proposed modifications are: add triangles filled with graduated colors to indicate horizon position, roll and pitch indicators that inform pilots of UAs and corrective procedures, and a thrust indicator that indicates throttle action to maintain adequate energy for aircraft recovery. Loss of control in-flight (LOCIF) is the primary cause of worldwide aviation fatalities. A LOCIF is classified as a failure or an inability to get an aircraft’s wings level and usually results from an unusual attitude (UA) (Schlimm, 2005). An UA condition is defined as greater than 45o bank, 25o pitch up, 10o pitch down or flying at speeds inappropriate for conditions while within the above parameters (Sumwalt, 2003a). Failure to recognize and promptly recover from such an UA can easily result in a plane crash. Over the ten year span from 1998-2007 LOCIF resulted in the greatest number of aviation fatalities for the commercial jet fleet, 22 fatal accidents and 2051 lives lost (Boeing, 2008). For corporate aircraft accident data from 1982 to 2002 LOCIF is the only mishap type that had not appreciably decreased (Sumwalt, 2003a). General aviation (GA) numbers are equally dismal. In 2000, there were 261 GA LOCIF accidents, 111 of these were fatal with 179 lives lost (NTSB, 2001). This accounted for 14% of all GA mishaps that year. 2001 saw 233 mishaps from LOCIF, 13% of all mishaps that year (NTSB, 2002). Although the LOCIF rate went down slightly, it still caused 111 fatal crashes with 190 lives lost. These numbers have not improved; in 2005 18% of all fatal GA accidents were due to a LOCIF (FAA, 2006). Several studies have examined how well certification requirements ensure that pilots are capable of recovering from an UA. According to one study 58% of professional pilots and nearly 72% of general aviation pilots were unable to recover from LOCIF upsets (Regional Aviation News, 2008). "As evidenced by our research results, pilots are ill-equipped to deal with loss of control scenarios beyond the accepted limitations of their training requirements during pilot certification and recurrent simulator training” (Regional Aviation News, 2008, p. 1). Another study corroborated these findings by noting that unusual attitude recovery training for commercial pilots was inadequate (Gawron, Berman, Dimuskes and Peer, 2003). In particular, it was noted that the stress of the unexpected scenario as well as the demand for immediate and correct analysis of the situation and correct action were overwhelming for many of their participants, directly inhibiting their ability to recover the aircraft. According to a director of flight operations for a major U.S. based carrier another key skill that has been reported missing from the aviation industry’s efforts to reduce LOCIF is training pilots to be able to “recognize potential upset conditions” (Sumwalt, 2003b, p 14). Unfortunately, one of the primary instruments designed for pilot orientation, the attitude indicator (AI), has been indicted as part of the problem. Numerous studies have shown that the western AI variant may lead to pilot misinterpretation and subsequently a recovery in the incorrect direction, complicating the problem and robbing the pilot of precious time. This situation is known as a roll reversal. Interestingly, the Soviet AI variant utilizes a different display type and has been shown in multiple studies to be more intuitive and less likely to induce roll reversals (Previc and Ercoline, 2000). LOCIF consistently costs hundreds of lives and millions of dollars annually. Something must be done to help improve pilots’ abilities to recover from UA and prevent these disasters. Some of this problem can be attributed to pilot disorientation, some to instrument misinterpretation and some to pilots failing to identify the developing situation. This paper proposes a comprehensive and intuitive solution to this problem by improving pilot awareness of developing aircraft attitude problems, reducing the opportunity to misinterpret their instruments, providing guidance for an expeditious recovery and in accomplishing these objectives reduce the threat of loss of control in-flight. 349 Proposed Solution The solution proposed is to make modifications to the AI that will help improve its interpretation and have it provide corrective guidance in throttle settings as well as in the roll and pitch directions. Three specific modifications are being proposed: a horizon indicator that improves ability to discern horizon location, roll and pitch guidance and throttle guidance. These modifications should be compared with both the Western and Soviet AI displays to determine which combination improves performance best. Horizon Indicator The horizon indicator is designed to help pilots more readily discern the horizon’s location. Isosceles triangles drawn into the ground and sky of the AI can meet this goal. The apices of these triangles would meet at the horizon line to form an hour glass with their opposing lines residing on their respective 90o pitch lines. To further elucidate horizon location the inside of the triangles would be colored with a gradient that is dark near the 90o pitch lines but pale near the horizon line. In this way, regardless of the orientation displayed on the AI, the pilot will always be able to discern the horizon location by following the visible triangle’s contours and color gradient to its apex. This intervention seeks to mitigate conditions such as seen in Figure 2 where no horizon line is evident, which can easily lead to a roll reversal. Figure 1. Horizon indicator Figure 2. Extreme unusual Figure 3. Extreme unusual at horizon. attitude without horizon attitude with horizon indicator. indicator. Roll and Pitch Indicator The second modification is to add roll and pitch correction indicators. Roll and pitch correction indicators would flank the perimeter of the AI (Figure 4). These indicators would illuminate with a green hue in the direction of correction necessary to recover to straight and level flight. These indicators are designed to illuminate to improve their salience. Not only do they instruct a pilot of correct recovery inputs but also promptly raise awareness of a hazardous situation as it develops, thereby compensating for the cognitive deficit experienced by a task saturated, complacent or distracted pilot. Figure 4. Roll and pitch indicators commanding a right bank and a pull up. To prevent human misuse of automation (e.g., overtrust) these indicators would only illuminate when the aircraft attitude is approaching a situation that could devolve into danger. Should the pilot fail to recognize these warnings and the attitude become worse, the appropriate roll and pitch indicators would blink to further increase their salience. The turn off threshold should be set at a value less than the turn-on threshold. This gap would prevent issues where a pilot flying on the cusp of the roll indicator’s 350 illumination settings would cue the indicator to turn on and off with slight changes in bank. This type of situation could lead to a detriment in safe flight performance as it might result in annoyance, distraction or complacency. Another item to be considered with the roll guidance indicators is an inverted attitude. In this situation the wings would be straight and level so the bank indicators would not be illuminated. This could be extremely dangerous because if the plane concurrently had a nose low attitude the pilot’s roll and pitch indicators would instruct the pilot to pull back on the controls—in effect complicating the situation and flying the aircraft to the ground. To prevent this, the system could be programmed to account for inversions. Should an inversion occur the roll indicators should instruct the pilot