Air Force Test Pilot School Research Articles

Measuring Perceived Agent Appropriateness in a Live-Flight Human-Autonomy Teaming Scenario

United States Air Force Test Pilot School students ( N = 6) participated in a study involving an agent-directed human pilot (“Blue agent”) in dogfighting scenarios against an adversary (“Red agent”). The adversary used three levels of difficulty as follows: low, medium, and high. An agent appropriateness scale was developed to gauge how appropriate the Blue agent’s behaviors were during each dogfight. Results demonstrated that agent appropriateness varied by Red agent difficulty. These results suggest that agent appropriateness is an essential element in human-autonomy teaming research. Practitioners should seek to develop agent appropriateness measures suitable for the particular context and technology in question.

Business Jet Fly-by-Wire Control Laws Handling Qualities Flight Test Assessment

Fly-by-wire control laws for a business jet were developed and a handling qualities assessment flight test was conducted on the Calspan Variable Stability System Learjet-25. The control laws, which provide a blended normal acceleration and speed () command response type in the longitudinal axis and a stability axes roll rate and sideslip () command response type in the lateral/directional axes, were optimized to meet Level 1 requirements for a comprehensive set of stability, handling qualities, and performance specifications. The control laws were evaluated in flight by U.S. Air Force Test Pilot School and Textron Aviation test pilots using a series of handling qualities demonstration maneuvers, including pitch and roll capture and tracking tasks and an offset landing task. Quantitative performance metrics were collected, in addition to pilot handling qualities ratings and comments. Several modifications were made to the control laws based on initial pilot comments and ratings. The final results show that the optimized fly-by-wire control laws provided assigned Level 1 handling qualities for discrete tracking and offset landing tasks.

Design and Flight Evaluation of Primary Control System for Learjet-25B Aircraft

In this paper, a multi-input/multi-output servomechanism primary flight controller is presented. Also discussed are flight data related to the system performance and pilot assessments of handling qualities. The data were collected during flight-test experiments (March 2018) on the Calspan Variable Stability In-Flight Simulator Learjet-25B aircraft. Aircraft body angular rates and linear accelerations are used to enable decoupled command tracking in pitch, roll, and yaw axes. Angle of attack and angle of sideslip measurements are not required for the system to operate. The developed primary flight controller translates pilot controls into the corresponding pitch, roll, and yaw commands for the aircraft to track. The system consists of a gain-scheduled robust linear baseline augmented with a direct adaptive model reference output feedback. The baseline is designed via the Observer-Based Loop Transfer Recovery method. The adaptive component incorporates the closed-loop reference model, whereby a state observer from the baseline Observer-Based Loop Transfer Recovery system also acts as the reference model for the adaptive augmentation. In March 2018, the Observer-Based Loop Transfer Recovery controller was successfully flight verified on the Calspan Learjet-25B aircraft, at the U.S. Air Force Test Pilot School, Edwards Air Force Base, California. Flight-test results are discussed, and a brief summary is given at the end.

Numerical Predictions of Static-Pressure-Error Corrections for a Modified T-38C Aircraft

The objective of this work was to highlight modeling considerations for estimating the required static-pressure-error corrections using computational fluid dynamics. This work was performed to complement the U.S. Air Force Test Pilot School activities that used a T-38C aircraft with a previously untested Pitot-static system. Before the flight test, it is highly desirable to have an estimate of how any modifications will affect sensor performance, and to possess the capability to explain any discrepancies from previous test programs. Estimates of this kind are only obtainable via wind-tunnel tests or through modeling and simulation. This work presents the computational fluid dynamics requirements and methodologies needed to estimate the static-pressure-error correction of a T-38C in the subsonic, transonic, and low supersonic regimes. Estimates are validated with flight-test results, and proposed solutions for further reduction of static-pressure error via modifications to the flight-tested Pitot-static-probe geometry are included.

A Flight Test Evaluation of the Arc Segment Attitude Reference for Use as a Primary Flight Reference in Helmet-Mounted Displays

The objective of this evaluation was to determine if the use of the Arc Segment Attitude Reference (ASAR) symbology in a head-up display (HUD) in place of the legacy climb-dive ladder attitude reference aids in unusual attitude recovery (UAR) piloting tasks as specified in AFM 11–217 for use as a primary flight reference (PFR). Flight tests were conducted at the US Air Force Test Pilot School (TPS), Edwards AFB, California on the NF-16D Variable-stability In-flight Simulator Test Aircraft (VISTA). Five VISTA flight UAR test sorties were flown. The time for the pilot to initiate a recovery was measured in addition to the correctness of the recovery. The flight tests were conducted with the use of the HUD combiner on VISTA to examine three symbology configurations. Each of the symbology configurations, the Mil-Std-1787C HUD, dual-articulated (DA) HUD, and ASAR HUD were evaluated by five pilots for the UAR task. The flight test results revealed the ASAR resulted in faster stick input for correction of UARs then the Mil-Std-1787C HUD. This study along with other supporting research indicates that the configural design properties of the ASAR support the ability of pilots to quickly ascertain aircraft attitude.

Longitudinal Flying Qualities Prediction for Nonlinear Aircraft

An analysis tool is presented that predicts longitudinal e ying qualities of a piloted aircraft subject to elevator rate limiting and nonlinear stick gradient. The method produces an explicit mathematical pilot model for the pitch attitude tracking task. By performing pilot-in-the-loop simulation, e ying qualities metrics are computed for evaluationofthelevelof e ying qualities.Theproposedmethodisvalidated using thee ightexperimentcalledHAVE LIMITS e own at the U.S. Air Force Test Pilot School. Good agreement was obtained between our analytical e ying qualities prediction and Cooper ‐Harper pilot ratings obtained in-e ight for elevator rate limits of 10 ‐157 deg/s.

Development of the Probe-and-Drogue Handling Qualities Demonstration Maneuver

The development of the probe-and-drogueaerial refueling task as a handlingqualities demonstrationmaneuver is described. The probe-and-drogue task is an excellent test of handling qualities for precision  ying and is also a superb check for pilot-induced oscillation tendencies. The greatest difŽ culty with this maneuver has been in the deŽ nitionof the task itself including the deŽ nitions of speciŽ c performance limits. The task described herein differs from that described in the Notice of Change to Flying Qualities of Piloted Aircraft (MIL-STD-1797A) in that it requires precise drogue tracking in addition to a percentage of successful hookups. A task representative of that deŽ ned in MIL-STD-1797A that required at least three hookups in six attempts for desired performance was used as the evaluationmethod for theHAVEGAS project conducted by the U.S.Air Force Test Pilot School. This version of the maneuver, however, was found to be too easy even for poorly rated airplanes. Revised maneuver descriptions and performance requirements were developed and evaluated in the HAVE GAS II project that was undertaken as part of the U.S. Air Force Demonstration Maneuvers program and again conducted by the U.S. Air Force Test Pilot School. Three candidate tasks were evaluated in this test program: 1) the probe-and-drogue hookup task, 2) a new drogue tracking task, and 3) a new drogue pointing task. Although the drogue tracking task was found to be best for evaluating closed-loop handling qualities, it was limited by the fact that it would not reveal potential problems such as bow-wave effects that may be encountered within 5 ft of the basket. Thus it was concluded that a combination of the drogue tracking task and the probe-and-drogue hookup task should be  own to thoroughly evaluate closed-loop handling qualities in the aerial refueling mission.