2016 - Wichita, KS
Stability and Control Testing of an
Autonomous Remotely Piloted Aircraft with Artificial Ice Shapes
Ryan D. Finlayson
Global Vigilance CTF
Edwards AFB, CA
Jonathan J. Kim
Global Vigilance CTF
Edwards AFB, CA
This paper discusses the flight test techniques and data analysis methods used to perform flight test validation of stability and control margins for the RQ-4 Block 20 Global Hawk—a semi-autonomous remotely piloted aircraft (RPA). This RPA was configured with simulated ice shapes attached to the full-span wing and tail leading edges. This type of testing was the first of its kind accomplished at Edwards AFB; no other program previously accomplished artificial ice shape flight test at the Air Force Test Center. Results from modeling and simulation and flight test are presented and compared.
AUTONOMOUS AERIAL REFUELING DEMONSTRATION INTEGRATING THE UCAS-D X-47B
WITH A MANNED TANKER IN LIMITED SCOPED AERIAL REFUELING TESTING
David E. Owens
Patuxent River, MD
The purpose of this paper is to provide a brief overview on the UCAS-D X-47B AAR demonstration program which was performed to demonstrate the technical feasibility of Navy probe/drogue UAS autonomous aerial refueling. The three objectives of the demonstration were to complete 3 autonomous engagements, transfer 3,000 lb of fuel, and accumulate 5 minutes of time engaged. These objectives were met through 16 total flights between March and April 2015 for a total flight time of 26.1 hours at NAS Patuxent River. After a short description of the X-47B and AAR system, this paper detail the build-up testing that led to formation flight with the Omega KC-707 tanker and the completion of the three demonstration objectives. This paper also highlights important lessons learned that benefited and ensured the success of the AAR demonstration program and are applicable to future UAS aerial refueling test programs.
FLARE: AN OPA FOR TECHNOLOGY VALIDATION USED AT THE ITALIAN
AEROSPACE RESEARCH CENTER
P. De Matteis
M. Di Donato
Validating aircraft technologies at high Technology Readiness Level (TRL) is usually a very high cost and risky activity. In order to satisfy its flight validation needs for RPAS enabling technologies, CIRA set up a multipurpose flying platform named Flight Laboratory for Aeronautical REsearch (FLARE), exploiting the possibilities offered by the Optionally Piloted Aircraft (OPA) paradigm. FLARE is based on the certified version of the P92 Echo Super aircraft produced by TECNAM and modified to integrate proprietary experimental set-ups. The flight experiments are performed in Optionally Piloted flight mode with the attendance of the pilot in command (PIC) which can always take back the control of the aircraft simply overriding the flight commands. FLARE has already been used successfully in the National Program for Aerospace Research (PRORA) framework and it is expected to be used in the framework of European projects for RPAS technology validation. Due to its characteristics of flexibility and low operational cost, the FLARE OPA offers a broad spectrum of uses for technology validation in aeronautics such as avionics, aero-structural, propulsion and sensors technology.
The paper will provide a technical description of the FLARE vehicle configuration and its performance, the modification applied to the baseline vehicle, the description of the payloads carried on board and the description of the process to get the Permit to Fly from the Italian Airworthiness Authority (ENAC) including the relevant test plan. The paper will also describe the configuration and performance of the dedicated Ground Control Station (GCS) hosting an innovative data-link system which ensures communication tasks between the Ground Control Station and the on board payload (digital data exchange, on board video transmission and vocal communications). The GCS allows test engineers both to monitor the flight experiments and to interact with the on-board payloads. In conclusion, the paper will provide technical information on how an OPA may represent a valid flight platform for technology validation..
Flight Testing Commercial UAVs in the Era of Autonomy
Recent innovations in robotic technology are creating new business opportunities in the commercial, manufacturing, and defense industries. A particular area of interest is in the use of unmanned aerial vehicles (UAV) for professional applications. The UAV platform offers fantastic potential for these applications because of its ability to easily reach locations where it is difficult, expensive or dangerous for humans to operate. UAV systems are revolutionizing the photography, surveying, and inspection industries. The application set is continually expanding and opening markets in infrastructure, agriculture, transportation, security, mining, telecommunications, insurance, and media and entertainment industries.
The current uses of UAV systems are limited from their full potential due to the requirement for a trained UAV pilot to operate each system and provide clearing and collision avoidance functions. Current commercially available UAV controllers are not able to safely function in a dynamic environment without a human operator.
Introducing civil autonomous UAVs into the National Airspace System (NAS) is a new challenge. Developing and testing new UAV technologies becomes difficult. It started with a required exemption from the Section 333 of Public Law 112-95 to fly for commercial small UAS under Title 14 CFR. However, new guidance was recently released and will be discussed further. Small UAS are still required to fly with visual line of sight, but there is a waiver process that may aid in allowing small UAS technologies to mature through open-air flight test.
Fire-by-Wire: F-35A Gunfire Testing
William J. Norton
The Joint Strike Fighter (JSF) conventional take-off and landing (CTOL) F-35A incorporates a 25mm gun under a ’canoe‘ fairing above the port intake. This supports the air-to-ground mission with an expected three firing passes and a total 181 rounds. The low-observable installation has a port door normally concealing the barrels and a purge door that permits ram air to facilitate gun gas evacuation from the gun bay. Fundamentally, ground and flight test were intended to demonstrate gun system compliance with specifications and so requirements, especially defining any high-altitude/low-speed ’pinch point‘ where insufficient airflow through the bay could exist to evacuate explosive gases safely for ’stutter‘ firing. The test planning from the earliest date adopted a new approach. This began with a risk reduction measurement of gun bay ventilation during non-firing flights to inform the predictive Computational Fluid Dynamics (CFD) analysis of the gun bay internal flow. This was followed by further measurements and gun gas sampling during ground gunfire that also verified proper gun system operation and suitable structural support. A suction fan provided the predicted minimum essential airflow through the bay. The gas samples were used to quantify the constituent elements. This permitted airborne gunfire with multiple firing events per flight without gas sampling provided the airflow instrumentation indicated suitable ventilation. Past programs had captured gas samples in flight with only one shot event per sortie. There was no room inside the F-35A for sample bottles and the program sought greater test productivity. Apart from validating this new approach to gunfire testing, the eventful testing provided other lessons learned from which future programs will benefit.
LEVERAGING PLC TECHNOLOGY TO INTERFACE NETWORK SENSORS
AND SUBSYSTEMS ON LEGACY PLATFORMS
John G. Kurkjian
Power line communications (PLC)-based transceivers provide an alternative to establishing dedicated, aircraft Ethernet networks. Adding new aircraft functionality or installing special purpose instrumentation often requires significant engineering and aircraft down time to complete. PLC based networks can reduce project cost and schedule by enabling localized aircraft modifications and leveraging existing aircraft wiring for the Ethernet medium. PLC standards continue to evolve and achieve greater throughput rates and noise mitigation. Ethernet communications have been tested over AC and DC power busses, data busses, and discrete wiring. PLC networks have been successfully demonstrated in avionics test beds and aircraft (including live video transfers), without causing interference to the basic systems or the underlying wiring functionality. PLC transceivers provide a cost effective solution to permanent or temporary installations of Ethernet-based sensors, payloads, and data acquisition equipment to existing aircraft.
Stores Compatibility Testing on the T-38C
Capt. Matthew M. McCormack, USAF
Holloman AFB, NM
The 586 Flight Test Squadron (FLTS) at Holloman AFB, NM transitioned from operating AT-38B aircraft to modified T-38C aircraft. The T-38C aircraft were modified to allow the aircraft to carry a centerline store similar to the AT-38B. The 586 FLTS has been performing store compatibility flight profile (CFP) testing to clear heritage stores flown on the AT-38B for flight on the T-38C. It was predicted that the minimal differences between the AT-38B and the T-38C would result in the stores having no differences/impacts to the T-38C; while this was mostly the case, two major findings were noted. First, the store‘s impact on aircraft gross weight limits and single engine rate of climb capabilities. Second, the loss of aircraft trim authority on final approach while within the approved aircraft CG envelope.
AT-6C Semi-Prepared Testing Operations
Lionel D. Alford
This paper documents the Beechcraft Defense Company‘s flight test program to demonstrate and provide company certification of the AT-6C Wolverine aircraft for operations on a semi-prepared surface. The test program was conducted in three phases. The first phase determined and ocumented safe procedures to conduct semi-prepared operations. The second phase provided a confirmation of structural loads on the aircraft and gear system on a semi-prepared surface, and gathered data to develop performance charts for semi-prepared operations. The third phase provided a confirmation of sonic and vibration aircraft characteristics in a semi-prepared environment. Based on this testing, the AT-6C Wolverine was shown to be a capable semi-prepared aircraft up to full combat loads (10,000 pounds) and drag configurations.
E-2D AERIAL REFUELING AUXILIARY STABILITY AUGMENTATION SYSTEM
THE POOR MAN‘S FLY-BY-WIRE
Jacob A. Rohrer
LCDR Shane L. Ehler
LT Joe A. Breeden
Nathan D. Atkinson
Aerial Refueling (AR) receiver capability for the E-2D is a developmental effort by the Navy and Northrop Grumman Corporation (NGC) to provide persistent Airborne Early Warning (AEW) and Command and Control for the Navy‘s carrier strike groups. The E-2D update results in numerous system and structural modifications. During AR risk reduction flight tests in 2011, the highly-coupled pitch and yaw response to power was highlighted as a risk to successfully executing AR. With a 1960s vintage, cable-and-pulley mechanical flight control system, coupled with a limited-authority Automatic Flight Control System (AFCS), the high workload during AR was not a surprise. It was apparent that an additional stability augmentation mode would be needed to aid the pilot during AR; however, with the existing Stability Augmentation System limited to a simple yaw damping/roll coordination mode, it requires a more comprehensive rewrite of the existing augmentation control laws.
The E-2 Integrated Test Team (ITT) set out to determine how to get an aircraft with a 1960s-era flight control system and level II handling qualities to reliably conduct day/night AR—a task the aircraft was never designed to do. In the late 1990s the E-2/C-2 Airborne Tactical Data System Program Office (PMA-231) implemented a digital Flight Control Computer (FCC) in the E 2C for the first time, replacing the legacy analog computer. This 1990s technology forms the foundation of the E-2D‘s Auxiliary Stability Augmentation System (AUX SAS) flight control mode. By combining the capability of the digital FCC with some creative engineering, the AFCS functionality was modified to create the first generation of the AUX SAS. The first generation AUX SAS consisted of a 3-axis stability augmentation mode that adjusted pitch, roll, and yaw damper algorithms. First flight tested in 2013, the first generation AUX SAS showed marked improvement in handling qualities over the unaugmented aircraft, especially in the longitudinal axis; however, handling qualities deficiencies remained. The control input to aircraft response proved to be almost 160 degrees out of phase, causing the pilot to easily excite a longitudinal pilot induced oscillation (PIO), especially during high-gain control input maneuvers like AR. With the fourth generation AUX SAS software, which includes a feedback loop for pitch attitude using the Embedded Global Positioning System Inertial Navigation System (EGI), phase lag is effectively reduced by changing the longitudinal control input from a rate command to an attitude command controller. The fourth generation AUX SAS will enter AR developmental tests in the last quarter of 2016.
Use of the Naval Air Warfare Center‘s Manned Flight Simulator (MFS) proved critical to deficiency analysis and the rapid development of the AUX SAS versions. Analysis and piloted MFS sessions demonstrated vast improvements in expected handling qualities over the original AUX SAS design. Flight tests during the developmental test period will be the final word..
HAVE LIGHT - An Evaluation of Electro-Optic System Imaging Performance
Test Techniques and C-12J Utility as an Electro Optics Airborne Test Bed
Lt.Col. Brian J. Neff
Holloman AFB, NM
Ronald J. Hardgrove
Holloman AFB, NM
This presentation will document the results of the Electro-Optic System Imaging Performance Developmental Test and Analysis Techniques (HAVE LIGHT) program. Testing was conducted from 25 February 2016 to 04 March 2016 in conjunction with the HAVE LIGHT Test Management Project at the USAF Test Pilot School with expertise, analysis tools and support provided by the 775TS/ENVD. The two primary test objectives were to evaluate the developmental and operational electro-optics system flight test and analysis techniques and demonstrate the utility of the highly modified C-12J operated by the 96th Test Group / 586th Flight Test Squadron to support Electro Optic performance testing of an advanced targeting pod. An additional overarching objective was to capture the results and make them publicly available for further advancement and incorporation into the Test Pilot School curriculum. The results of this effort clearly highlight the strengths and weaknesses of legacy test techniques while also detailing an enhanced technique that enables sensitivity and resolution measurements throughout the field of regard.
IDENTIFICATION OF AERODYNAMIC MODEL UNDER GROUND
EFFECT WITH FLIGHT TEST DATA
Sergio Salzedas Vilela
Bruno Giordano de Oliveira Silva
This work proposes a way to use flight tests to determine the aerodynamic behavior of an aircraft flying into the ground effect making it possible to implement this influence in a flight simulator. In order to apply this methodology, flight tests were conducted, using the EMB-314 aircraft (military designation A-29, Super Tucano), comprising maneuvers for aerodynamic model estimation out of ground effect and landing approaches for incremental load estimation as function of height considering the ground effect. The model is based on theoretical results obtained from the image method and a vortex lattice formulation. The fight test data were analyzed using Flight Path Reconstruction and nonlinear output error parameter estimation techniques. The validation showed that the incorporation of the ground effect reduced the RMS error by 32.0%, 18.3% and 70.1% for the lift, drag and pitching moment coefficients, respectively.
PERFORMANCE MODEL VALIDATION FOR LONG-ENDURANCE UNMANNED
AIRCRAFT USING MACH VS. CL TEST METHOD
Patuxent River MD
Patuxent River MD
The standard method for fixed-wing aircraft performance testing uses a weight/pressure ratio (delta) method, however most wind-tunnel derived performance models are based on the relationship between Mach and lift coefficient (CL). In order to better correlate with established performance models, test points can be flown at Mach and CL intervals by adjusting altitude and airspeed profiles based on real-time aircraft weight. This method is well-suited for long endurance unmanned aircraft since they can be setup on condition using inputs from the test crew and then execute pre-programmed commands that hold the aircraft steady on condition. With proper coordination and training, this method may also be applicable to performance testing of manned aircraft.
Perspectives on U.S. Military
Commercially-Derived Aircraft Programs
Bombardier, Wichita KS
FULL ENVELOPE AIRSPEED CALIBRATION USING A SINGLE
TURNING ACCELERATION TECHNQIUE
Juan D. Jurado
USAF, Hurlburt Field FL
Clark C. McGehee
USAF TPS, Edwards AFB
Timothy R. Jorris
Virtually every performance or flying qualities flight test program begins with the calibration of either the aircraft‘s production Pitot-static system and/or a dedicated Air Data Boom (ADB). One of the main goals in Pitot-static calibration is to determine the Static Source Position Error (SSPE), or the error induced in Pitot-static instrument readings due to the disturbance of the local static pressure field by the aircraft itself . SSPE is typically manifested in errors in Indicated Airspeed (IAS) and altitude, both of which rely on accurate static pressure readings. Although there are currently many Flight Test Techniques (FTTs) designed to collect Pitot-static calibration data, they are all based on the general principle of flying the aircraft at known conditions such as Ground Speed (GS) and altitude, while simultaneously comparing the known conditions to instrument readings.
Altitude calibration techniques pose significantly less challenges due to the ease and simplicity associated with flying the aircraft at a known geometric and pressure altitude using the prolific Tower Flyby FTT. In contrast, airspeed calibration techniques present additional challenges due to the common inability to measure (and differentiate between) IAS, GS, and wind speed during test execution. Additionally, since the static field disturbances that generate SSPE are produced by the act of flying the aircraft, the airspeed and altitude errors found during calibration tend to be functions of airspeed itself . Therefore, in order to characterize SSPE in both airspeed and altitude, a range of test points covering a reasonable portion of the aircraft‘s flying envelope must be flown.
This paper aims to provide a robust framework for the data collection, reduction, and processing of airspeed calibration data as well as a novel FTT for obtaining such data. The combination of the proposed data framework and method for obtaining data will be shown to drastically improve the test efficiency and data quality associated with the airspeed calibration of any flight test program. Prior to identifying the underlying gaps in the state of the art methods, it is important to briefly compare the existing methods.
Steep Approach – A Practical Guide
Gulfstream, Savannah GA
Steep Approach in the Part 25 arena is generally synonymous with the desire to operate into and out of London City Airport (EGLC) in the United Kingdom. Steep Approach is defined in AC25-7C as an approach angle of 4.5 degrees or more, and for certification the applicable requirements of Sections 25.119, 25.121, 25.125, and 25.143 of Title 14 CFR Part 25 and the corresponding EASA regulations must be met. This paper therefore deals with the practical requirements that need to be satisfied to operate at EGLC with its 5.5-degree approach angle and relatively short runway.
AIR DATA SYSTEM CALIBRATION,
ENHANCEMENTS OVER THE CLASSICAL GEOMETRICAL APPROACH
Luiz Antonio Algodoal Vieira
Vinicius Leite de Morais Veras
Many of the present commercial aircraft sales-contracts incorporate fuel efficiency related clauses. Aircraft specific fuel consumption (SFC) is commonly used in those contracts as fuel efficiency measurement. Since SFC is a function of airspeed, airspeed system errors associated to it play an important role in the specific fuel consumption measurement thus becoming a key commercial factor.
Several methods for airspeed error assessment are available. Those may be categorized in pressure or positioning methods, depending on the source used for airspeed calculation. The instrumentation needed for pressure methods is too intrusive to be installed in production aircraft. The geometric methods are more convenient in terms of intrusiveness, but usually do not result in a suitable precision for SFC monitoring purposes.
EMBRAER recently developed and validated enhancements over the classical geometrical methods in order to improve its precision. This article presents the proposed enhancements over the classical geometric methods and shows the obtained new level of precision, resulting in a precise enough method as to be suitable for production aircraft SFC monitoring, while remaining non-intrusive.
HANDLING QUALITIES EVALUATIONS OF UNMANNED AIRCRAFT SYSTEMS
Edwards AFB, CA
Since 1969, the Cooper-Harper Rating Scale has been used widely in flight test to qualitatively evaluate the handling qualities of manned aircraft. Within the past decade, the use and popularity of Unmanned Aircraft Systems (UAS) has expanded into military operations and commercial applications. Therefore, there is a need to understand the handling qualities of these systems when a pilot is required for in-the-loop control. Key differences in flight control systems, autonomous flight capabilities, and overall system latency in unmanned versus manned aircraft necessitate the development of approaches to enhance understanding of these systems. This paper identifies the need for Cooper-Harper evaluations of UAS, highlights the differences between manned and unmanned systems, and provides an approach to determining the Cooper-Harper evaluation of unmanned systems.
DISTRIBUTED TEST OPERATIONS:
LESSONS LEARNED FROM GEOGRAPHICALLY SEPARATED CONTROL ROOMS
Capt Stephen J. Miller
Eglin AFB FL
Maj Jennifer P. Hines
Eglin AFB FL
FLTLT Timothy G. White
Eglin AFB FL
The Air Force Test Center (AFTC) has constructed the Inter-Range Data System (IRDS) to allow for remote control of Air Force test missions across the United States Major Range and Test Facilities and Bases (MRTFB). The IRDS has the potential to increase effectiveness and efficiency and reduce costs of test missions by combining engineering expertise of geographically separated personnel without requiring travel to the test location. The operational aspects and development of IRDS have largely been sponsored by The Air Force SEEK Eagle Office (AFSEO), located at Eglin AFB, FL. AFSEO is the Air Force‘s primary source of technical knowledge and center of expertise on aircraft store compatibility and is currently expecting a dramatic increase in workload as 5th generation fighter testing requirements transitions from the System Development and Demonstration phase of testing. This paper will address the background of the IRDS project to include reasons behind development, technological specifications, past mission experiences, lessons learned, and future leadership considerations for the AFTC enterprise. The primary focus will cover the difficulties presented by a control room that is both geographically and organizationally split. The test team has successfully streamed six F-16, two F-22 and eight F-35 missions from Edwards Ridley Control Center (RCC) to the Eglin Central Control Facility (CCF)., A full F-16 flutter test mission was controlled by test personnel at Eglin AFB utilizing an F-16 flying out of Edwards AFB. The team will also address the mission success rate of tests planned and the difficulties in scheduling geographically separated tests.
Teaching an Old Aircraft Some New Tricks
Lessons learned in the evaluation of Anti-Skid Brakes in the C-2 Greyhound
Ms. Justine Roemer
Mr. Joshua Cooper
The C-2 Greyhound is a high-wing, twin-engine monoplane cargo aircraft manufactured by the Northrop Grumman Corporation to satisfy the Navy‘s need for the Carrier Onboard Delivery (COD) mission. Celebrating its 50th anniversary in 2014, the current-day COD aircraft has undergone myriad improvements to overcome both obsolescence and safety deficiencies. Although currently slated to be phased out during the next decade, there is still significant time and effort being expended to teach this old aircraft some new tricks.
To accomplish its mission within restrained deck-space, the COD aircraft embodies all of the aerodynamic compromises of a twin-engine turboprop. It should be no surprise that the aircraft exhibits deficiencies in directional stability and coupling in all axes associated with power changes and response. These deficiencies also affect aircraft handling dynamics during landing roll-out. Early test flights of the C-2 more than 50 years ago identified a desire for an antiskid braking system (ABS). The addition of ABS to the C-2 would mitigate landing difficulties due to directional excursions. Although the COD mission requires nearly fifty percent shipboard landings without ABS, the remaining fifty percent require operations from remote, and often austere, locations. Because of variability in aircraft loads and runway conditions, the C-2, in performing the COD mission, would benefit tremendously from the increased safety and flexibility of an ABS.
The extreme sensitivity of the C-2 wheel brakes has often caused inadvertent main tire failures during landing roll-out. Due to this sensitivity, it has become common practice to avoid the use of brakes at all costs during normal flight operations. New pilots are imbued with an unhealthy fear of brake application which has created a systemic limitation in COD aircrew knowledge of how to properly use brakes. During landing events in which directional control is compromised or in emergency situations when brakes are needed the most, the aircrew can‘t rely on the brakes as a safe and suitable control effector. To address the safety implications of this deficiency, the Navy initiated a program, which is currently being tested, to implement an ABS which would allow the use of brakes without experiencing main tire failures.
LESSONS LEARNED FROM FLY-BY-WIRE:
HAZARDS AND MITIGATIONS WITH NEW TECHNOLOGY
Mark R. Updegrove
Bombardier, Wichita KS
Bombardier Aerospace certified its first Fly-By-Wire aircraft in December 2015. This paper will use specific test campaign events as examples to highlight the challenges and learning opportunities associated with anticipating and defining the unique Test Hazard Analyses pertaining to the introduction of new company technology (fly-by-wire flight controls) into an already highly integrated aircraft design philosophy.