SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 9 - MAY 5, 2006

08 AIRCRAFT STABILITY AND CONTROL
Includes flight dynamics, aircraft handling qualities, piloting, flight controls, and autopilots.

For related information see also 05 Aircraft Design, Testing and Performance; and 06 Avionics and Aircraft Instrumentation.

20060011586 Saab Aerospace, Sweden

Flight Test of the Autonomous Take Off and Landing Functions of the SHARC Technology Demonstrator

Duranti, SImone; Malmfors, Viktor; Flight Test: Sharing Knowledge and Experience; May 2005, pp. 18-1 - 18-18; In English; See also 20060011579; Original contains color and black and white illustrations; Copyright; Avail.: CASI: A03, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

The Saab s unmanned technology demonstrator SHARC has completed in August 2004 a third flight test campaign, at the NEAT test range, in northern Sweden. For the first time the SHARC conducted fully autonomous missions, including Autonomous Take Off and Landing (ATOL). The focus of the test campaign has been in verifying the newly developed ATOL functionalities. Simulator and Hardware-In-the-Loop test sessions paved the way to flight testing. The importance of reliable dynamic models has been once more highlighted. Ground roll dynamic and ground effect aerodynamic models had been refined ad-hoc in order to predict the behaviour of the aircraft during the critical phases of rotation and touch down. In preparation to the flight test campaign, ground rolls have for the first time been performed at the Saab's flight test centre in Link ping. The flight test campaign has been fully successful. The autonomous landing functionality is operationally invaluable, since it lowers the risks embedded in manual remote piloting during high-gain tasks. A number of specific functionalities had been designed into the avionics to allow safe and effective flight testing of the new capabilities; most of them regarded the possibility of the UAV operator to condition the behaviour of the aircraft in order to limit the authority of the onboard autonomy. Author

Flight Tests; Aerodynamic Characteristics; Autonomy; Simulators; Rotation; Roll; Pilotless Aircraft; Takeoff; Landing

20060011592 Test Wing (0412th), Edwards AFB, CA, USA

Unmanned Air Vehicles: A New Age in Human Factors Evaluations

Moisio, Deborah A.; Spravka, John J.; Payton, Mary G.; Flight Test: Sharing Knowledge and Experience; May 2005, pp. 5A1 - 5A16; In English; See also 20060011579; Copyright; Avail.: CASI: A03, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

As the role of the aircraft pilot transitioned from a nearly total manual controller in early manned aircraft to one of supervisory control and/or cooperative functioning in unmanned aircraft, the human factors flight test approach and the associated test methodologies have necessarily changed. Piloting air vehicles evolved from using cockpit instruments and manual controls to fly the aircraft, to monitoring the cockpit instruments which fly the aircraft nearly automatically, to using ground station instruments to fly the aircraft remotely.

While most, if not all, of the physical stressors of the cockpit are absent from the typical ground control station, many of the cockpit stimuli that provide invaluable aircraft health and status information are also absent. Increased levels of automation have induced new types of failures. These include failure to monitor, vigilance decrement, over reliance on standard values, automation-induced complacency, and increased latency in detecting problems. Consequently, these failures often lead to reduced operator performance due to information shortfall.

As the pilot-aircraft relationship evolve, the focus of human factors evaluations moves from what the pilot physically perceives and processes in the cockpit, to what the pilot mentally perceives and processes on the ground. Physical information from the aircraft, such as vibration and sound cues, must be transformed into usable information on the ground station displays. This includes keeping the level of automation appropriate so the pilot on the ground can be aware of and adequately handle emergency situations. Since pilot workload for an Unmanned Air Vehicle (UAV) is mostly mental, maintaining situation awareness is paramount.

This paper identifies some critical components of new human factors approaches for evaluating UAV human-system interfaces and compares them with approaches traditionally used to evaluate manned air vehicles. Author

Pilotless Aircraft; Human Factors Engineering; Flight Tests; Ground Based Control; Ground Stations; Aircraft Control

20060011593 Ministry of Defence Boscombe Down, Salisbury, UK

Assessing Human Factors in UK Military UAVs

Greenbank, Chris; Ayliffe, Alec; Flight Test: Sharing Knowledge and Experience; May 2005, pp. 5B-1 - 5B-12; In English; See also 20060011579; Copyright; Avail.: CASI: A03, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

Automation is a key attribute of modern UAV systems. In the UK, for example, one of the most common user requirements is for launch and recovery to be completely automatic, which is the case with QinetiQ's Observer UAV. But the Human has an important role that varies in detail according to the type of UAV. The level of detail and the assessment philosophy must be adapted to the size and role of the UAV. Clearly, a 5 kg mini- UAV will present different challenges than a large, High Altitude Long Endurance UAV. The assessment will need to take into account the complexity of the system but the underlying principles of the assessment of different UAVs will be similar. Some of the common human roles that are likely to be essential to safety include: a) Planning; b) Managing Failure/Emergency states and other non-nominal situations; and c) Supervision/control. The design of the UAV system impacts on the ability of the Human to fulfill the required role without undue error and is often the main focus of any assessment, but operational and maintenance issues cannot be ignored Derived from text

Human Factors Engineering; Errors; Emergencies; Safety; User Requirements; Failure; Pilotless Aircraft

20060011601 Murphy (Ryan), Patuxent River, MD, USA

T-45 Stability Augmented Steering System

Murphy, Ryan; Wiseman, Reid; Stack, Christina; Flight Test: Sharing Knowledge and Experience; May 2005, pp. 1-1 - 1-5; In English; See also 20060011579; Original contains color and black and white illustrations; Copyright; Avail.: CASI: A04, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

The ground handling characteristics of the T-45 Goshawk (a U.S. trainer variant of the Hawk aircraft) were identified as problematic since the early days of flight testing. Deficiency report SA-162 addressed the overly sensitive directional control characteristics of the T-45 during landing rollout. This Part IK deficiency was not corrected during initial developmental testing and has presented itself in over 12 runway departures or loss of controls within the last two years.

The runway departures typically occur when students who are not familiar with the landing characteristics, make large corrective inputs for aircraft heading during the landing rollout. The lowest region of directional stability has been observed in the 60-85 kt range. A variety of potential solutions were attempted to remedy the deficiency over the years.

Initially, full time nose wheel steering (NWS) was added to the aircraft. Although some improvement was noted, directional control during landing rollout remained an issue. Following the incorporation of full time NWS, several iterations of pulse width modulation NWS and active yaw damping during landing rollout were evaluated. None of these solutions provided sufficient improvement for fleet incorporation.

Following these unsuccessful attempts to finding a ground handling solution, NAVAIR and Boeing initiated a ground handling study. This study resulted in a proposal to provide yaw rate feedback to the NWS to improve ground handling during landing rollout. This system became the Stability Augmented Steering System (SASS). An engineering company that primarily investigates the handling qualities of racecars, Systems Technology, Inc., completed the study. Study results determined the geometry of the landing gear on the small airframe, combined with the material composition of the tires, created the unstable ground handling characteristics of the aircraft. Unable to practically redesign the geometry of the landing gear and the lack of suitable tire material to remake the tires, it was necessary to design a new system that could limit the departure characteristics by trying to limit the yaw that may be experienced during the landing rollout. This system had to operate in both the T-45A and the T-45C aircraft, and therefore designed as an independent system requiring limited information from the aircraft. Derived from text

Systems Engineering; Directional Control; Directional Stability; Aerodynamic Characteristics; Flight Tests; Steering; Damping; Controllability

Source: NASA