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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

A hingeless rotor XV-15 design integration feasibility study. Volume 1: Engineering design studies

A design integration feasibility study was carried out to investigate what modifications to the basic XV-15 were necessary to accomplish a flight demonstration of the XV-15 with a Boeing hingeless rotor. Also investigated were additional modifications which would exploit the full capability provided by the combination of the new rotor and the existing T53 engine. An evaluation of the aircraft is presented and the data indicate improved air vehicle performance, acceptable aeroelastic margins, lower noise levels and improved flying qualities compared with the XV-15 aircraft. Inspection of the rotor system data provided shows an essentially unlimited life rotor for the flight spectrum anticipated for the XV-15.

Magee, J. P.↗
NASA NTRS1975

NASA/Army XV-15 tilt rotor research aircraft familiarization document

The design features and general characteristics of the NASA/Army XV-15 tilt rotor research aircraft are described. This aircraft was conceived as a proof-of-concept vehicle and a V/STOL research tool for integrated wind tunnel, flight-simulation, and flight-test investigations. Discussions of special design provisions and safety considerations necessary to perform these missions are included in this report. In addition to predictions of aircraft and engine performance for the hover, helicopter, and airplane flight modes, analytical estimates of the structural and dynamic limitations of the XV-15 are provided.

Source record↗
NASA NTRS1976

Evaluation of XV-15 tilt rotor aircraft for flying qualities research application

The results of a design review study and evaluation of the XV-15 Tilt Rotor Research Aircraft for flying qualities research application are presented. The objectives of the program were to determine the capability of the XV-15 aircraft and the V/STOLAND system as a safe, inflight facility to provide meaningful research data on flying qualities, flight control systems, and information display systems.

Radford, R. C.↗
NASA NTRS1977

The influence of pitch-lag coupling on the predicted aeroelastic stability of the XV-15 tilting proprotor aircraft

The predicted dynamic stability of the XV-15 tilting proprotor aircraft in cruise flight is updated, using a reduced increase in the pitch gimbal coupling with collective, and a higher nominal control system stiffness. The major influence of the pitch-lag coupling of the XV-15 gimballed, stiff-inplane rotor on the aircraft stability is shown. The influence of the blade pitch dynamics is found to be contained primarily in the quasistatic pitch-lag and pitch-gimbal coupling, although the complete dynamics is retained in the analysis for an accurate quantitative calculation of the stability boundary.

Johnson, W.↗
NASA NTRS1977

Status report on XV-15 Tilt Rotor Test Program

The XV-15 Tilt Rotor Research Aircraft Program has progressed from the design and fabrication stage to the test phase and is now beginning that portion of the program which will culminate in the determination of the viability of this promising concept. This paper will review the joint Army/NASA/Bell Helicopter Textron (BHT) XV-15 program as it currently stands, including the results of the experience gained during the design and fabrication phases and testing to date. Highlights of the overall Tilt Rotor Program will be discussed exploring the potential of this concept to result in a new generation of highly productive VTOL systems.

Brown, J. H., Jr.↗
NASA NTRS1976

Predicted dynamic characteristics of the XV-15 tilting proprotor aircraft in flight and in the 40- by 80-ft. wind tunnel

Pretest predictions of the dynamic characteristics of the XV-15 tilting proprotor aircraft are presented. The data for the aircraft in flight include: trim conditions, flight dynamics, gust response, aeroelastic stability and the wing response to control. The data for the aircraft in the Ames 40- by 80-ft wind tunnel include aeroelastic stability and the wing response to control. The calculations were made for pylon tilt angles of 0 deg (airplane mode), 0.1 deg (pylon unlocked), 30, 60, and 90 deg (helicopter mode).

Johnson, W.↗
NASA NTRS1976

Preliminary simulation of an advanced, hingless rotor XV-15 tilt-rotor aircraft

The feasibility of the tilt-rotor concept was verified through investigation of the performance, stability and handling qualities of the XV-15 tilt rotor. The rotors were replaced by advanced-technology fiberglass/composite hingless rotors of larger diameter, combined with an advanced integrated fly-by-wire control system. A parametric simulation model of the HRXV-15 was developed, model was used to define acceptable preliminary ranges of primary and secondary control schedules as functions of the flight parameters, to evaluate performance, flying qualities and structural loads, and to have a Boeing-Vertol pilot conduct a simulated flight test evaluation of the aircraft.

Mcveigh, M. A.↗
NASA NTRS1977

Performance and safety aspects of the XV-15 tilt rotor research aircraft

Aircraft performance is presented illustrating the flexibility and capability of the XV-15 to conduct its planned proof-of-concept flight research in the areas of dynamics, stability and control, and aerodynamics. Additionally, the aircraft will demonstrate mission-type performance typical of future operational aircraft. The aircraft design is described and discussed with emphasis on the safety and fail-operate features of the aircraft and its systems. Two or more levels of redundancy are provided in the dc and ac electrical systems, hydraulics, conversion, flaps, landing gear extension, SCAS, and force-feel. RPM is maintained by a hydro-electrical blade pitch governor that consists of a primary and standby governor with a cockpit wheel control for manual backup. The two engines are interconnected for operation on a single engine. In the event of total loss of power, the aircraft can enter autorotation starting from the airplane as well as the helicopter mode of flight.

Wernicke, K. G.↗
NASA NTRS1977

XV-15 tilt rotor test - Progress report

In a continuing effort to expand the versatility of their aircraft, VTOL designers have for many years tried to combine the desirable features of various concepts into a single aircraft. This is a formidable task and most efforts have met with limited success. This paper explores the need for an aircraft combining the efficient VTOL capability of a helicopter with the efficient high speed characteristics of a fixed wing turboprop. The ability of the tilt rotor concept to fill this requirement and examples as to its potential usefulness in both military and civil missions is discussed. The history of the concept and the status of the current Army/NASA/Bell XV-15 program and its role in proving the viability of the concept are reviewed.

Brown, J. H., Jr.↗
NASA NTRS1978

Evaluation of the tilt rotor concept: The XV-15's role

The need for an aircraft combining the efficient vertical takeoff and landing capability of a helicopter with the efficient high speed characteristics of a fixed wing turboprop is examined. The ability of the tilt rotor concept to fill this requirement and examples as to its potential usefulness in both military and civil missions is discussed.

Brown, J. H., Jr.↗
NASA NTRS1976

Analytical evaluation of tilting proprotor wind tunnel test requirements

Specific test requirements related to the wind tunnel testing of the XV-15 advanced tilt rotor research aircraft were determined. The following analytical tools were developed: (1) digital simulation of the XV-15, incorporating a simplified tunnel support model, control system loop, measurement lags, gust disturbances, and sensor noise, (2) specialization of existing data analysis programs to the high order XV-15 dynamical model (transfer function program, a time series analysis program, an advanced maximum likelihood parameter identification program), (3) several auxiliary programs to provide estimates of damping from transfer functions as well as calculations of model decomposition of system response. The following results were discussed: (1) modelling of the aircraft, instrumentation, and controls, (2) results of the rotor/cantilever wing model and coupled wing, (3) examples of data prediction with system identification techniques, and (4) detailed conclusions and recommendations.

Hall, W. E., Jr.↗
NASA NTRS1977

Pilot evaluation of an advanced hingeless rotor XY-15 simulation

A piloted simulation of an advanced hingeless rotor XV-15 tilt-rotor aircraft was carried out. The evaluation was made by a pilot from NASA-Ames who had previous experience flying a simulation of the current gimballed rotor NASA/Army XV-15. It was pointed out that some modifications to the force feel system were needed in order to provide rapid force trimming during rapid maneuvers. Some additional tailoring of the SCAS system was required to achieve good nap-of-the-earth performance. Overall pilot opinion on the hingeless rotor XV-15 tilt rotor was favorable. Brief discussion on the mathematical models and the simulator configuration are presented. The maneuvers and pilot comments are given along with some engineering comments.

Mcveigh, M. A.↗
NASA NTRS1976

Wind Tunnel Test Results of 25 Foot Tilt Rotor During Autorotation

A 25 foot diameter tilt rotor was tested in the 40 by 80 foot large scale wind tunnel. The test confirmed the predicted autorotation capability of the XV-15 tilt rotor aircraft. Autorotations were made at 60, 80, and 100 knots. A limited evaluation of lateral cyclic was made. Test data indicate a minimum rate of descent of 2,200 feet per minute at 60 knots at the XV-15 design gross weight of 13,000 pounds.

Marr, R. L.↗
NASA NTRS1977

Aerodynamic interference effects on tilting proprotor aircraft

The Green's function method was used to study tilting proprotor aircraft aerodynamics with particular application to the problem of the mutual interference of the wing-fuselage-tail-rotor wake configuration. While the formulation is valid for fully unsteady rotor aerodynamics, attention was directed to steady state aerodynamics, which was achieved by replacing the rotor with the actuator disk approximation. The use of an actuator disk analysis introduced a mathematical singularity into the formulation; this problem was studied and resolved. The pressure distribution, lift, and pitching moment were obtained for an XV-15 wing-fuselage-tail rotor configuration at various flight conditions. For the flight configurations explored, the effects of the rotor wake interference on the XV-15 tilt rotor aircraft yielded a reduction in the total lift and an increase in the nose-down pitching moment. This method provides an analytical capability that is simple to apply and can be used to investigate fuselage-tail rotor wake interference as well as to explore other rotor design problem areas.

Soohoo, P.↗
NASA NTRS1977

Simulation study of gust alleviation in a tilt rotor aircraft, volume 1

The response to vertical turbulence in cruise of the HTR XV-15 design is studied using simulation techniques. This design is a modified version of the XV-15 with a hingeless fiberglass soft-in-plane rotor system. The parameters of a gust alleviation system are determined and the performance of the system is evaluated over a range of cruise velocities and altitudes.

Amos, A. K.↗
NASA NTRS1977

Tilt-proprotor perspective

The general tilt-proprotor concept is discussed, and a more detailed look at the XV-15 aircraft is taken. The special features of the two-engine system, engine control system, and flight control system are mentioned. The main objectives of the XV-15 program are to (1) verify rotor/pylon/wing/dynamic stability and aircraft performance over a representative operational envelope, (2) assess the handling qualities and establish a safe operating envelope, and (3) investigate gust sensitivity, effects of downwash, and hover operation. With regard to rotor/pylon stability, one challenge is to be able to predict a parameter's value and then build hardware to match. The analytical program has gained some respect through aeroelastic and full-scale XV-3 demonstrations. Special concern centers around the thrust and power management system when flying at high speed when very small changes in rotor collective pitch represent large changes in thrust and power. Demonstration of the system awaits wind-tunnel and flight testing.

Few, D. D.↗
NASA NTRS1974

Measurement of tilt rotor VTOL rotor wake-airframe ground aerodynamic interference for application to real time flight simulation

The hover and low speed rotor wake-airframe-ground aerodynamic characteristics of the XV-15 tilt rotor research aircraft were determined in wind tunnel tests of a scale model. Results of the wind tunnel tests were applied to real flight time simulation. The principal findings of the wind tunnel tests are summarized. The effect of aerodynamic interference on the handling qualities of the aircraft is analyzed. It was determined that aerodynamic interference effects are significant in hover and at low speeds, with the influence being more pronounced in ground effect than out of it. At airspeeds above 60 knots, aerodynamic interference does not have a significant effect on handling characteristics.

Gaffey, T. M.↗
NASA NTRS1976

Flight Flutter Testing of Rotary Wing Aircraft Using a Control System Oscillation Technique

A flight flutter testing technique is described in which the rotor controls are oscillated by series actuators to excite the rotor and airframe modes of interest, which are then allowed to decay. The moving block technique is then used to determine the damped frequency and damping variation with rotor speed. The method proved useful for tracking the stability of relatively well damped modes. The results of recently completed flight tests of an experimental soft-in-plane rotor are used to illustrate the technique. Included is a discussion of the application of this technique to investigation of the propeller whirl flutter stability characteristics of the NASA/Army XV-15 VTOL tilt rotor research aircraft.

Yen, J. G.↗