SUMMARY The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static clmax characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of single- element, multi-element, and variable geometry airfoils.

EVALUATION OF HELMET MOUNTED DISPLAY ALERTINGSYMBOLOGYJoe De MaioAeroflightdynamics DirectorateU.S. Army Aviation and Missile CommandAmes Research CenterINTRODUCTIONThe present research is aimed at developing tools to support the NASA Safe All-weather Flight Operations Research (SAFOR) program. The goal of our part ofthis program is to make dramatic reductions in the rate and severity of civilrotorcraft accidents through reduction in pilot error. This research is alsosupported by a cooperative agreement between the Army AeroflightdynamicsDirectorate and NASA Ames Research Center.A major factor in pilot error is the failure to apprehend critical information or tointegrate isolated facts into a coherent concept that can guide correct behavior.An important tool for improving pilot situation awareness is the helmet mounteddisplay. In its earliest implementations, the helmet display was used primarilyas a weapon pointing device. With the addition of sensor imagery it came to bean aid to flight in limited visibility.The benefit from a helmet mounted display increases when the pilot has alessened requirement to look back into the cockpit. Ultimately it is desirable tomake the helmet display the primary flight instrument. In fact the Army's RAH-66 Comanche will have the helmet display as its primary flight display. Thehelmet display needs to be well integrated with the panel instruments whenused in this way. It needs to present as much information as possible withoutbeing cluttered or obscuring the out-the-window view. It also needs to permit aneasy transition back into the cockpit when this is needed.Pilots face purely mechanical problems in shifting from the helmet display to thepanel display. They must refocus and reconverge their eyes from infinity tounder 31 inches (Hawkins, 1997, p 246). They must also adapt to a differentdisplay brightness. These problems compound the biggest problem, that ofswitching attention from the out-the-window task to the in-cockpit task.Switching from one task to another can be a slow process. It can take as much astwo to three seconds to switch from one attention demanding task to anotherdemanding task. Switching time can be reduced substantially by effectivealerting (De Maio, 1976).The research used two approaches to increasing the effectiveness of alerts. Onewas to increase the ability of the alert to attract attention by using the entiredisplay surface. The other was to include information about the requiredresponse in the alert itself.

Although use of the term situational awareness (SA) assists researchers in creating more fruitful environments for pilots to operate in, its true potential as a psychological construct remains untapped until a valid means of a priori predicting SA becomes available. Shively, Brickner and Silbiger (1997) proposed a computational model of SA (CSA) that seeks to do just that, and the current line of research is a series of studies aimed at validating that model. Originally developed for the Man-machine Integration Design and Analysis System (MIDAS), the CSA model is comprised of two features: situational elements and situation-sensitive higher-order nodes. Situational elements comprise what is known/perceiv ed about the environment (e.g. tank1 or waypoint3). Each is associated with a particular higher-order node, and as a group define the situation. Higher-order nodes are semantically related groups of SE's (e.g. threats or navigation) that are weighted based on their importance in the situation. One original aspect of the CSA model is the differentiation between perceived, actual and error SA, a proportion of which produces the operator's predicted SA. Initial validation studies using low-fidelity tasks supported the predictions of the model. Preliminary data analysis of a mid-fidelity, full-mission task completed in the Rotorcraft Part-Task Laboratory (RPTL) at NASA Ames also indicates support for predictions of the model.