Air University Review, November-December 1969
Major Donald J. Kutyna
Flight-testing of piloted aircraft has been going on since the day the Wright brothers made their first flight more than sixty-five years ago. Just as "the proof of the pudding is in the eating," so also must the proof of an airplane be in the flying, for engineering will always remain in part an empirical science, subject to verification by actual test. Thus, although the aeronautical sciences have undoubtedly enjoyed vast development during the past fifty years, this development has not eased but rather has intensified the need for flight-test work and, in turn, the need for trained flight-test and research-test pilots.
Flight-test training in the Air Force originated as an in-house activity in Test Operations at Wright Field, Ohio, about 1943. It progressed to formal school status, with its own staff and aircraft, and in 1951 moved to Edwards AFB, California. Events of the late 1950s disclosed the need for aerospace pilots trained for work in advanced aircraft and manned space research programs. Thus in 1961 the research pilot or "aerospace training" phase was added to the Test Pilot School’s curriculum. Now called the Aerospace Research Pilot School (ARPS), it is constantly changing to keep its course of instruction, test methods, and training vehicles ahead of the anticipated needs of future test programs. People who were associated with the school just a few years ago would hardly recognize it today.
The purposes of any flight-testing of piloted aircraft are to determine the actual characteristics of the machine (as contrasted to the computed or predicted characteristics); to provide developmental information; and to obtain research information. The particular mission of the Aerospace Research Pilot School is to train experimental test pilots to supervise and conduct flight tests of research, experimental, or production-type aerospace vehicles; and to train aerospace research pilots for flight test, engineering design, and/or management in advanced aerospace research programs.
To enlist the highly capable pilots desired to work eventually in the field of flight test, the school and the Air Force maintain an exceptionally rigid selection process. The minimum eligibility requirements are a bachelor’s degree in engineering, physical science, or mathematics; application to be made before 32d birthday and the course entered before 33d birthday; applicant must be an active duty pilot in the grade of major or below, with a minimum of 500 hours as instructor or first pilot in jet or turboprop bomber or transport aircraft, in supersonic fighter or trainer aircraft, in helicopters, or in a combination of these.
While these minimum requirements must be met even for consideration, the large number of applicants allows final selection of pilots with much higher qualifications. In the last four graduating classes the average backgrounds of the 16 military members of each class included ten bachelor’s degrees, five master’s degrees, and one doctorate; average age of 31; and 2300 hours’ flying for the average fighter/trainer pilot (11 pilots per class), 2800 hours’ flying for the average bomber/transport pilot (5 pilots per class).
Diversity of experience is an important (and in today’s Air Force a rare) attribute sought for in a prospective test pilot. The majority of the pilots selected for the school have extensive operational experience in three or more aircraft. In addition, experience and subsequent assignment considerations dictate the desirability of a combat tour in Southeast Asia prior to assignment to the school. Thus almost all recent entrants have completed Vietnam tours.
Phase I — Experimental
Test Pilot Course
The eight-month Experimental Test Pilot Course is designed to train pilots in the latest methods of testing and evaluating aircraft and related aeronautical equipment. The academics, simulation, and flying training are designed to give the student the theoretical and practical background required to supervise and conduct flight tests of research, experimental, or production-type aircraft.
Phase I is divided into two major segments, Performance, and Stability and Control; they are approximately three and five months in duration, respectively.
The Performance subphase progressively develops the theory, flight-test techniques, and data-reduction methods associated with performance flight-testing.
Academics.The academics are conducted at the level of an undergraduate aeronautical engineering course, beginning with a brief review of calculus, physics, thermodynamics, and aerodynamics and progressing through the detailed theory of aircraft and engine performance and testing. The time allotted some of the subjects is extremely limited. The calculus review is just two hours long and in reality consists only of a final exam covering an entire year’s course in calculus. Physics-thermodynamics is allotted only six hours to cover all applicable concepts. This brevity of the basic courses is dictated by the ever increasing complexity of flight-testing and the greater number of subjects to which a new test pilot must be exposed to prepare him to understand and perform his work. The factor which allows pushing the student through the basics at this rapid pace is the students own high-level academic background—most of those accepted for the school had a B± or better average in related courses at the undergraduate or graduate level.
Flying.Performance flying closely parallels the academic curriculum and teaches the student the basic methods of performance data gathering. Airspeed and altimeter calibration, takeoff, climb, range, acceleration, turning, and descent performance are all investigated. To apply his knowledge to a practical exercise, each student flies a limited performance flight-test program in either the T-33, T-38, or B-57 and documents his results in a formal written report. Individual oral briefings on the progress of the test program give each student the experience to practice this form of reporting.
Stability and Control
The Stability and Control subphase is designed to prepare the student to test and evaluate the handling qualities of an aircraft.
Academics.Background theory courses in vector analysis, differential equations, operational math, and dynamics prepare him to derive the basic equations of motion of an aircraft. The equations are examined in detail, with in-depth studies of each of the important terms that influence aircraft stability. Considerable time is spent on the theory behind roll coupling, spin testing, and aeroelastic effects. The expanding role of electronic and hydraulic systems to aid or completely implement the stability and control of modern aircraft has dictated the inclusion of an extensive group of subjects related to linear and nonlinear control theory. More than fifty hours are allotted to this area of study. In all, the student spends 475 hours in the classroom during the Phase I Performance and Stability and Control portions of the curriculum.
Flying.The uniqueness of the APRS curriculum lies in the coupling of the academic courses with the school’s computers, simulators, and aircraft. As an example, to investigate the stability and dynamics of an aircraft, the student first derives the basic aircraft equations of motion and becomes familiar with the variables involved. These equations are placed on an analog computer, where the effects of varying basic frequencies and damping ratios can be observed visually. The school’s static aerodynamic simulator is then used to allow the student to vary individual stability parameters to see how they change an aircraft’s handling characteristics. Having acquired this basic familiarity with the parameters involved, the student takes to the air in Cornell Aeronautical Laboratory’s B-26 variable stability trainer and the two ARPS NF-106 variable stability aircraft. These flying laboratories allow an infinite variance of aircraft handling qualities and control systems, and they give the student firsthand in-flight experience in observing a vast range of flight characteristics that could never collectively be found in individual test or production vehicles. Finally, the student applies his newly gained experience to the planning, conducting, and reporting of a relatively complete stability and control investigation of the F-104 and either the T-33, T-38, or B-57. In addition to the basic stability measurements, the investigation includes an examination of the "engine out" characteristics of the B-57, the spin characteristics of the T-33, and the high supersonic mach number handling characteristics of the F-104 V/STOL. The Stability and Control portion of ARPS training also includes an extensive introduction to the emerging field of vertical-and short-takeoff-and-landing technology. Both helicopter and V/STOL theory are coupled with helicopter flight in the H-13 and UH-1F, and V/STOL flight simulation in the Ryan XV-5 simulator. Future plans call for advanced helicopters and V/STOL training aircraft to be added to the curriculum.
Another area which receives heavy emphasis in Phase I is qualitative flight-testing. Each student is briefed on the optimal techniques to be employed and then performs a one-flight evaluation of one or more aircraft that he has never flown before. Aircraft available for evaluation span most of the Air Force inventory and even include some Navy and allied vehicles.
Finally, the pilots are given a two-hour introductory glider flight program to complement their high-performance experience with very high-lift flight. The introduction consists of eight flights in the Schweizer 2-32, 2-33, and 1-26 at a nearby gliding facility. In addition to gaining a basic familiarity with aircraft of this type, the student gathers limited data on glider handling and performance.
Probably the most tedious yet one of the most necessary parts of the curriculum is the written and oral report program. In addition, the individual analysis of the test data required to prepare a report is a powerful tool in helping the student develop a critical eye for the effects of flying accuracy on test results. A test pilot who cannot clearly and accurately report his findings would be wasting valuable time and effort in flying a test program. Thus opportunities are given the student to practice and develop his writing and speaking abilities.
As the end the Phase I curriculum approaches, the student begins to gain considerable understanding of the language, theory, techniques, and problems of flight-testing. Thus at this time he is given increasing opportunities to learn through a series of lectures by various experts in fields associated with flight test. In addition, each class is given field trips to various test activities and aircraft manufacturers, and one class each year travels on a two-week visit to study the flight-test centers and schools of our allies in Europe.
The end of Phase I of the Experimental Test Pilot Course signals the departure of the foreign and civilian students. As graduates of this phase, they have been trained to perform as test pilots, engineers, and managers on atmospheric test programs of research, test, and production-type aircraft and V/STOL vehicles. The U.S. military students remain at the school for an additional four months’ training in the Phase II Aerospace Research Pilot Course.
Phase II –Aerospace
Research Pilot Course
The 3 ½-month Aerospace Research Pilot Course is designed to increase the qualifications of the Phase I graduate to enable him to participate in the flight-testing, engineering design, and/or management of the various Air Force advanced aerospace research programs. The course includes (1) academic instruction in subjects related to performance and operation of advanced aircraft and space vehicles, (2) practical test flying in aircraft and simulators exhibiting the characteristics of research aircraft and manned space vehicles, (3) familiarization with the physiological and psychological aspects of high-performance and space flight, and (4) field trips to various government and civilian facilities engaged in the development, testing, and employment of present and future advanced aircraft, space vehicles, and related systems and components.
Much emphasis is placed on the intensive Phase II academic program. The subjects are presented at the graduate level and consist of background studies in astronomy, digital computers, bioastronautics, space environment, and the supporting mathematics. The mechanics and performance aspects of advanced aircraft and space flight are investigated in courses on rocket propulsion, space flight mechanics, and atmosphere re-entry heating. Finally, aircraft and space vehicle guidance and control capabilities are studied in space navigation and inertial guidance courses.
An extensive simulation curriculum bridges the gap between classroom theory and practical application. The missions are keyed to progression in academics and range from small part tasks in fixed base devices to full mission simulations including complete propulsion, control, guidance, visual cues, instrument displays, sound, heat, pressure suit facilities, vibration, and simulated motion and g levels, etc., of a specified space system in real time. Most major maneuvers of the current and near-future space programs are duplicated by simulation, using currently three kinds of simulation equipment:
used to simulate any aerodynamic vehicle, including those with rocket propulsion and reaction controls, at any altitude and velocity, from re-entry to light aircraft environment.
Static Aerodynamic Simulator --
Control Systems Simulator--used to simulate any aerospace mission part task from attitude orientation and control evaluation to launch, rendezvous, and re-entry.
T-27 Simulator—Until the recent cancellation of MOL, the school used the complex T-27 space simulator, which included a visual system for portraying the earth, stars, and a rendezvous vehicle, plus special effects such as heat, pressure suit facilities, sound, and vibration and vestibulary cues. The instrumentation, controls, and displays allowed simulations ranging from light aircraft to complex space missions. This facility is still present, but in "flyable storage" condition.
All simulations take place under normal gravity; however, motions and attitudes are used to place the gravity vector so as to best simulate the g forces of the mission. Actual zerogravity experience is provided in an Air Force Systems Command C-135, flying zero-gravity and moon-gravity profiles. Heavy g profiles (up to 15 g) are experienced in the centrifuge at the School of Aerospace Medicine, Brooks AFB, Texas, where actual space-program g profiles are flown, including launch, abort, and re-entry.
The Phase II flying curriculum fortifies the flight-test training of Phase I by providing additional experience in high-performance and unusual aircraft. It also provides space- and research-related flight experience by using special and conventional aircraft in configurations with research-vehicle handling qualities in typical research flight profiles. This experience includes exposure to zerogravity, pressure suit survival, rocket propulsion, reaction control handling, energy management, variable stability, and lifting-body flight profiles and landing characteristics.
Included in missions flown in the Phase II curriculum are low lift-to-drag ratio (L/D) patterns and landings. In a series of about a dozen flights the student examines the handling and performance characteristics of an F-104 in various low L/D configurations designed to simulate X-15 and lifting-body vehicles. Several profiles are flown to include the X-15 landing pattern and high- and low-speed lifting-body landing approaches. In addition to becoming familiar with the limited performance characteristics and precise energy management requirements of low L/D vehicles, the student derives practical experience in determining the L/D’s of variously configured aircraft; he can then predict the critical parameters for vehicle maneuvers and landing patterns. Although only a few graduates of the school will be fortunate enough to fly or test vehicles such as the X-15 or the lifting bodies, a much larger number will be associated with advanced aircraft programs in support, chase, and managerial positions. These considerations, in addition to the test pilots’ enhanced capabilities resulting from the varied experience, make the low L/D program an extremely useful portion of the curriculum.
NF-106.The NF-106 variable stability trainer (mentioned in the Phase I discussion) is designed for extensive application in the Phase II curriculum, which is oriented towards advanced aerospace research vehicles. It is a two-seat F-106B with major modifications that allow it to be used as a "model follower" in-flight simulator of a variety of aircraft or flight vehicles. The modifications include a 144 amplifier analog computer, which stores the model to be followed, a stability parameter programmer, a force feel system for the aft cockpit center stick, a front and rear cockpit side-arm controller, and an auto pilot that follows three parameters—vertical acceleration, side acceleration, and bank angle under cruise conditions—and automatically flies the NF-106 in such a manner that the model and actual aircraft parameters are equal.
To simulate a desired aircraft, the equations of motion of that aircraft are first programmed into the analog computer. The aft center stick is disconnected from the basic NF-106 and connected to the computer and force feel hydraulic actuator. As pilot control inputs are fed into the computer, the equations of motion are immediately solved, and the expected motion of the simulated aircraft appears at the output of the computer. The student’s instruments in the rear cockpit, which receive this computer output, then indicate the airspeed, altitude, attitude, etc., of the model. An electronic loop which monitors the vertical acceleration, side acceleration, and bank angle of the model automatically drives the flight controls of the NF-106 in such a manner that these three parameters are the same as in the model. The hydraulic fed actuator then works on the aft center stick to give the pilot the same forces he would feel were he actually flying the aircraft being simulated.
The stability parameter programmer can be used to change the handling qualities as a function of mach, airspeed, or altitude. This allows the NF-106 to simulate other aircraft for any portion of their flight profile.
The school’s two NF-106s are used in a unique series of missions. The Phase II portion of these missions includes investigation and evaluation of
NF-104 energy management and stability and control profiles
X-15 high-altitude profiles
X-15 high-speed profiles
X-24A lifting-body energy management flights
X-24A lifting-body stability and control flights.
The NF-106 enables the student to experience and evaluate the flight characteristics of the selected vehicle through any portion of its flight profile. For example, the X-15 high-altitude mission takes the student from launch at 45,000 feet altitude, mach .84, and a dynamic pressure of 145 pounds per square foot to a peak altitude of 250,000 feet, velocity of 4460 feet per second, and a dynamic pressure of .7 psf. The simulation then continues to a high-dynamic-pressure re-entry condition above 75,000 feet. Although the NF-106 itself will not approach this profile, the student experiences all the handling qualities, instrument readings, and visual and acceleration cues (within the limits of the NF-106) that he would experience in an actual X-15 flight. The simulation can be frozen at any point in the profile, to allow the student to perform a detailed examination of the handling qualities at that point. It is anticipated that the learning outcomes of these simulations will be of great value to pilots participating in present or future advanced research and space flight programs.
Zoom missions.Probably the most eagerly anticipated and rewarding missions in the Phase II curriculum are the zoom familiarization flights. In addition to the great benefits of broadened experience, these missions are designed to expose the student to the demanding requirements of flight in near outer space conditions. The basic program consists of seven missions flown in the F-104. During the first mission, pressure suit familiarization, the student flies a depressurized F-104 at high altitudes and high mach numbers to experience the techniques and limitations of flight in a fully inflated suit. The second mission, a demonstration of the basic zoom profile, is with an instructor and is flown in a two-place F-104D; it is limited to a 30° climb angle with a resulting peak altitude between 70 and 80 thousand feet. The remaining five missions, flown solo in an F-104C, are basically the same maneuver with climb angles increasing from 30° to a maximum of 45°. Resulting peak altitudes, which are a function of exactness of technique and meteorological conditions, average just below 90,000 feet. The engine is turned off at approximately 75,000 feet and restarted when descending through 60,000 feet, and a precautionary X-15 type pattern is flown to the Rogers lakebed runway at Edwards. In the eight years this program has been in existence, there has never been a case of failure of an engine to restart.
NF-104.For a portion of the class, completion of the F-104 zoom missions signals the end of the flying curriculum. However, a select few of the students in each class are given the opportunity to fly an additional three-mission NF-104 zoom program. The NF-104 is an F-104A modified by the addition of a rocket engine, extra wingspan, a larger tail, reaction control jets in the wingtips and nose, and a reaction jet controller in addition to the center stick. The aircraft is designed to fly basically the same zoom profile as the F-104 but with a significantly higher altitude capability. This higher altitude is reached with the help of a 6000-pound-thrust JP-4/ hydrogen-peroxide-fueled LR-121/AR-2 rocket engine, which is used on the run-in and during the climb portion of the mission. Thrust duration is approximately two minutes.
The altitude capability, using a mission-prescribed climb angle of 40°, is between 100 and 110 thousand feet. At these altitudes the dynamic pressures are low enough (20 psf) to allow precise aircraft attitude control through the use of hydrogen peroxide reaction control jets. Manual actuation of the jets is by a hand-operated reaction control handle.
The F-104 and NF-104 zoom missions give the student unique experience in a variety of disciplines oriented toward advanced aircraft and research vehicles. In addition to familiarity with basic X-15 type flight, re-entry, and landing profiles, the student gains a rare appreciation for the precision, energy management handling, and meteorological tradeoffs involved in safely reaching the maximum altitude capability of an aircraft. Aircraft response to normal and reaction controls at extreme altitudes is investigated. Zerogravity conditions are experienced. Pilot capabilities and limitations under full pressure suit operation are demonstrated. Finally, the missions serve as an evaluation of the pilot’s ability to react optimally under the demanding conditions of environment and vehicle performance to be found in present and future advanced aircraft research programs.
The end result of the zoom missions is a pilot who has experienced, as closely as economically and operationally practical, many of the conditions and exacting requirements of advanced research flight. This experience, added to his test pilot training, is an invaluable asset in the actual manning, support, or management of future manned or unmanned flight research and space programs.
As at the end of Phase I, the students finishing Phase II are taken on several field trips to industry and government agencies, to broaden their knowledge of the hardware and techniques of advanced aircraft and space operations. One of the major excursions is a week-long orientation at the School of Aerospace Medicine, Brooks AFB, Texas, to examine the physiological and psychological aspects of high-performance flight and space flight.
Graduates of the combined Phase I and Phase II course are uniquely qualified to take part in both atmospheric and space-oriented test programs. They are also thoroughly prepared to undertake the highly specialized training required for mission performance as astronauts in specific space vehicles.
Graduates of the Aerospace Research Pilot School have taken part in most of the significant flight-test achievements in this and several other countries. They fill assignments as research pilots, key crew members, and managers in Air Force programs, including every modern bomber, fighter and transport, the X-15, YF-12, and B-70, the lifting bodies HL-10, M2-F2, and X-24, and the Mercury, Gemini, Apollo, and Manned Orbiting Laboratory (MOL) programs. (In February 1966 ARPS developed a preliminary MOL crew training plan for the Space Systems Division of Air Force Systems Command. All MOL astronauts were to be graduates of ARPS and of the special 4- to 6-month postgraduate course in subjects directly applicable to the MOL. Three groups completed this training before cancellation of MOL in mid-1969.)
While 41 of the nation’s astronauts are graduates of ARPS, the majority of the school’s military graduates go on to positions as research pilots in the Air Force Systems Command. Typical of their assignments are positions in fighter or bomber test operations at the Air Force Special Weapons Center, Kirtland AFB, the Air Force Missile Development Center, Holloman AFB, the Armament Development Test Center, Eglin AFB, the Aeronautical Systems Division, Wright-Patterson AFB, and the Air Force Flight Test Center, Edwards AFB.
The staff of the Aerospace Research Pilot School consists of highly qualified Air Force test pilots, scientists, and engineers. Although none are specialists in every field associated with flight test, the overall composition of the staff ensures that each of these areas is covered by at least one instructor with expert qualifications. In addition to experience in bomber, fighter, transport, and V/STOL test operations, the staff as a whole has had considerable combat, scientific research, and educational experience. Total flying time per staff member averages over 3500 hours, and among the 28 working instructors there are twenty master’s degrees and two Ph.D.'s in related scientific disciplines.
The general aim that dictates the schools future direction is to maintain a dynamically progressive curriculum which will stay ahead of the anticipated needs of future atmospheric and space test programs. This requires continually changing courses of instruction, development of new test methods, and flight-test training in the latest state-of-the-art vehicles.
The school’s academic flight-test curriculum is progressively updated by selecting as staff members test pilots with recent scientific and/or graduate-school experience. An extensive series of guest lectures by experts from leading universities, civilian aerospace corporations, and government test facilities augments the modernization of the curriculum and provides an insight into new methods of flight-testing. Major new equipment under study includes a variable stability helicopter, a practical and reliable V/STOL training aircraft, a powered lifting-body trainer, and a universal aircraft simulator.
Proper direction in the selection of these new vehicles, the timely changes to the curriculum, and the development of new test methods are ensured through close and continuing contacts between the Aerospace Research Pilot School and the many branches of the aerospace profession.
USAF Aerospace Research Pilot School
Major Donald J. Kutyna(USMA M.S., Massachusetts Institute of Technology) is an instructor, USAF Aerospace Research Pilot School, Air Force Flight Test Center, Edwards AFB, California. He is a graduate test pilot, having completed the Research Pilot School course in 1966. Prior to his present assignment, he was a Select Air Crew Commander in the B-47, March AFB, California. Major Kutyna has more than 3300 jet flying hours, 1500 of which are in fighter aircraft, and has served as instructor pilot in F-104, B-57, T-33, and T-38 aircraft.
The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.
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