The prediction of VTOL periodic loadings... Where do we stand?
Periodic loading prediction on rotating structural components of helicopters and VTOL aircraft
White, R. P., Jr.↗
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The effect of constraints on optimum approach and departure paths for VTOL terminal operations
Approach and departure paths of VTOL aircraft under constraints of noise, traffic, safety, and economy for optimum trajectory
Hollister, W. M.↗
Evaluation of terminal constraint on error state vector for VTOL landing guidance
Error state vector for VTOL aircraft landing guidance considering terminal constraints
Joglekar, A. N.↗
A review of lift fan propulsion systems for civil VTOL transports
Lift fan propulsion systems for civil VTOL aircraft
Lieblein, S.↗
Decision processes in the adaptive behavior of human controllers
Decision algorithms simulating human controller adaptive behavior in controlling VTOL aircraft in hover following stability augmentation system failure
Bekey, G. A.↗
Optimum VTOL flight paths under constraint
Minimum fuel takeoff and landing paths for VTOL aircraft with constraints on state and control, determining optimal trajectories
Hollister, W. M.↗
Identification of a nonlinear system using a combined algorithm
Parameter identification algorithm for nonlinear equations describing VTOL aircraft longitudinal response
Denery, D. G.↗
Mechanical stability augmentation system Patent
Mechanical stabilization system for VTOL aircraft
Garren, J. F., Jr.↗
The reduction of VTOL operational noise through flight trajectory management
Prop rotor and lift fan VTOL aircraft ground noise level reduction, using flight trajectory management
Schmitz, F. H.↗
Bonding titanium to Rene 41 alloy
Pair of intermediate materials joined by electron beam welding method welds titanium to Rene 41 alloy. Bond is necessary for combining into one structure high strength-to-density ratio titanium fan blades and temperature resistant nickel-base alloy turbine-buckets in VTOL aircraft lift-fan rotor.
Scott, R. W.↗
Empirical expressions for estimating length and weight of axial-flow components of VTOL powerplants
Simplified equations are presented for estimating the length and weight of major powerplant components of VTOL aircraft. The equations were developed from correlations of lift and cruise engine data. Components involved include fan, fan duct, compressor, combustor, turbine, structure, and accessories. Comparisons of actual and calculated total engine weights are included for several representative engines.
Sagerser, D. A.↗
Operating systems in the air transportation environment.
Consideration of the problems facing air transport at present, and to be expected in the future. In the Northeast Corridor these problems involve community acceptance, airway and airport congestion and delays, passenger acceptance, noise reduction, and improvements in low-density short-haul economics. In the development of a superior short-haul operating system, terminal-configured vs cruise-configured vehicles are evaluated. CTOL, STOL, and VTOL aircraft of various types are discussed. In the field of noise abatement, it is shown that flight procedural techniques are capable of supplementing ?quiet engine' technology.
Cherry, G. W.↗
A model following variable stability system for the NASA ARC X-14B.
A description of the basic design concept, hardware design, and flight evaluation of a Variable Stability System (VSS) installed on the NASA ARC X-14B is presented. The NASA ARC X-14B is a twin-engine, single-seated VTOL aircraft. The VSS is unique in that it employs a general purpose airborne digital computer as an integral part of the hybrid model following flight control system. The system design, analysis and testing phases are discussed in the paper from the application of optimal control techniques in the preliminary design of the system, through the flight demonstration of the VSS hardware.
Gallagher, J. T.↗
A pilot's opinion - VTOL control design requirements for the instrument approach task.
This paper presents pilot opinion supported by test data concerning flight control and display concepts and control system design requirements for VTOL aircraft in the instrument approach task. Material presented is drawn from research flights in the following aircraft: Dornier DO-31, Short SC-1, LTV XC-142A, and Boeing-Vertol CH-46. The control system concepts and mechanizations employed in the above aircraft are discussed, and the effect of control system augmentation is shown on performance. Operational procedures required in the instrument approach task are described, with comments on need for automation and combining of control functions.
Patton, J. M., Jr.↗
A performance measure for manual control systems
A new performance measure is introduced for multivariable closed loop experiments with a human operator. The essential feature of the phase margin performance measure (PMPM) is that the performance of each control loop can be determined independently, with prescribed disturbance and error levels. A variable filter parameter is used as the PMPM within the loop and it assures a high workload at the same time. There is a straightforward relationship between the PMPM and the inner loop feedback augmentation that can be utilized in trade-off studies. An adjustment scheme that seeks the PMPM automatically is described as employed in a single loop control task. This task applies directly to the experimental study of displays for helicopters and VTOL aircraft.
Dukes, T. A.↗
Aero-acoustic design and test of a multiple splitter exhaust noise suppressor for a 0.914m diameter lift fan
A lift fan exhaust suppression system to meet future VTOL aircraft noise goals was designed and tested. The test vehicle was a 1.3 pressure ratio, 36 inch (91.44 cm) diameter lift fan with two chord rotor to stator spacing. A two splitter fan exhaust suppression system thirty inches (76.2 cm) long achieved 10 PNdB exhaust suppression in the aft quadrant compared to a design value of 20 PNdB. It was found that a broadband noise floor limited the realizable suppression. An analytical investigation of broadband noise generated by flow over the treatment surfaces provided very good agreement with the measured suppression levels and noise floor sound power levels. A fan thrust decrement of 22% was measured for the fully suppressed configuration of which 11.1% was attributed to the exhaust suppression hardware.
Stimpert, D. L.↗
Steady state analysis of Energy Transfer Control (ETC) and compressor bleed concepts of remote lift fan control
Two new concepts of control for VTOL aircraft remote lift fans are analyzed and discussed. Both concepts employ flow transfer among lift fans located in separate parts of the aircraft in order to obtain attitude control moments in hover and low-speed flight. The results presented are from a digital computer analysis of the YJ97/LF460 remote drive turbofan, although qualitative conclusions should apply to any remote fan system. The basic operating principles of the two systems are described, and their steady-state moment generating capabilities are discussed. Lift-recovery strategies for component failures are also analyzed.
Sellers, J. F.↗
A manual-control approach to development of VTOL automatic landing technology.
The operation of VTOL aircraft in the city-center environment will require complex landing-approach trajectories that insure adequate clearance from other traffic and obstructions and provide the most direct routing for efficient operations. As part of a larger program to develop the necessary technology base, a flight investigation was undertaken to study the problems associated with manual and automatic control of steep, decelerating instrument approaches and landings. The study employed a three-cue flight director driven by control laws developed and refined during manual-control studies and subsequently applied to the automatic approach problem. The validity of this approach was demonstrated by performing the first automatic approach and landings to a predetermined spot ever accomplished with a helicopter. The manual-control studies resulted in the development of a constant-attitude deceleration profile and a low-noise navigation system.
Kelly, J. R.↗