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Technical Paper

Numerical and Experimental Study of Drag Characteristics of HLFC Airfoils in High Subsonic, High Reynolds Number Flows

1994-03-01
940034
Hybrid laminar flow control (HLFC) is one of the most practically promising aircraft drag reduction technologies. We have investigated both numerically and experimentally aerodynamic characteristics of HLFC airfoil and wing at high subsonic, high Reynolds number conditions. In this paper we report the result of a wind tunnel test on drag characteristics of two-dimensional HLFC airfoils with porous and slot suction approach under some adverse factors against laminar flow, and a numerical analysis of the wind tunnel data, which is based on the boundary layer calculation with new transition prediction method allowed for the adverse factors and the Squire-Young drag formula.
Technical Paper

In-Flight Simulator Evaluation of a Flight Reference Display for Powered-Lift STOL Aircraft

1994-03-01
940013
A new flight reference display for powered-lift STOL aircraft was proposed and evaluated in actual flight environment. The display was developed to provide a simple monitoring system of STOL safety margins with good handling characteristics in place of a speed indicator. Using this display, pilots repeated simulated approaches of the experimental jet STOL “ASKA” using the VSRA as an in-flight simulator. In the evaluation, emphasis was placed on agreement between the display and the motion cues experienced by the pilot. Pilot comments and flight data confirmed satisfactory control characteristics and safety margin presentation of the display.
Technical Paper

A Preliminary Evaluation Test of GPS/DGPS Navigation System

1994-03-01
940012
The National Aerospace Laboratory (NAL) has been conducting basic research on the future landing navigation system of airplanes and a proposed future unmanned reentry space vehicle, using NAL research airplane Dornier Do-228 in which a Collins NAVCORE- I GPS C/A receiver was installed. A ground-to-air data link system was developed in order to realize the real time DGPS operation which improves accuracy. In this paper, experimental evaluation test results of not only GPS stand-alone operation but also DGPS operation are discussed. Since the navigation algorithm in the NAVCORE- I receiver could not be modified, this paper mainly discusses the difference of the two operations. In fixed point ground tests, ground and onboard GPS receivers were connected to the same antenna in order to avoid common errors, and both receivers output positions were compared with a reference map position. In the flight tests, approach/landing flights were conducted.
Technical Paper

Flight Path Control for the Approach and Landing of the Quiet STOL Experimental Aircraft ASKA

1994-03-01
940001
The Upper Surface Blowing STOL experimental aircraft ASKA, was developed and flight tested by the National Aerospace Laboratory of Japan. The ASKA operated well on the backside of the drag curve, and because of this flight path control was accomplished with the throttle lever (thrust) during approach and landing. To compensate for the sluggish flight path response caused by the thrust response lag, the flight path control law put in stability and control augmentation system. Flight tests were conducted to evaluate flight path and airspeed response characteristics. This paper describes ASKA's flight path and airspeed response characteristics, as well as construction of the flight path control system.
Technical Paper

Aerodynamic Development of Boundary Layer Control System for NAL QSTOL Research Aircraft ‘ASKA’

1991-09-01
912010
“ASKA” developed by National Aerospace Laboratory (NAL) is a quiet, short take-off and landing (QSTOL) research aircraft adopting upper surface blowing (USB) concept as a powered high lift system. To achieving sufficient STOL performance by augmenting stall angle of attack and roll control power, blowing BLC technique was applied to the outboard leading edges and ailerons.Supplied high pressure air to save the BLC piping space,the BLC system which was fit for use of high pressure air was developed. The BLC system, in which BLC air is discharged by a series of discrete jets from small drilled holes (0.8 ∼ 3.0 mm in diameter) arranged in a raw, is one of the unique features of the aircraft. In this paper, the summaries of aerodynamic development of the BLC system are described except for the air piping system.
Technical Paper

Wind Tunnel Investigation of an Improved Upper Surface Blown-Flap Transport Semi-Span Model

1991-09-01
911993
The ASUKA was based upon the airframe of the home produced C-1 tactical transport which was modified into an Upper Surface Blowing (USB) powered high lift STOL aircraft. But the wing configuration was not changed. Therefore, this Experimental Aircraft doesn't always have the optimum configuration of a USB type aircraft. This paper describes the investigations which have been conducted to improve the aerodynamic characteristics of a subsonic jet transport semi-span model with an Upper Surface Blowing Flap system which has been newly designed using the NAL STOL-CAD program. The tests were conducted in the NAL 2- by 2-meter Gust Wind Tunnel and results were obtained for several flap and slat deflections at engine thrust coefficients from 0 to 1.85. As compared with the aerodynamic characteristics of the ASUKA model, we obtained the possibility of reduction of the airframe weight and significant improvement of the aerodynamic characteristics.
Technical Paper

HUD Guidance for the ASKA Experimental STOL Aircraft using Radar Position Information

1992-04-01
921041
The paper describes a high performance Head-Up Display (HUD) guidance system installed on the experimental powered-lift STOL aircraft “Aska”. Since the maiden flight in October, 1985, the HUD system has been used in all the flight tests. The HUD has an accurate flight path symbol generated by inertial velocity from the IRS which is updated by up-linked precision radar position data. The flight path symbol is very useful for precise approach and flare control for Aska which has large ground effects. A synthetic runway is also presented, which is conformal with the real runway, using the position data from the ground tracking radar system. Under Instrument Meteorological conditions (IMC), the pilot can approach and land using the HUD synthetic runway as well as in Visual Meteorological Conditions (VMC). The HUD system proved to be a valuable aid to the pilot for all the Aska flight tests.
Technical Paper

Limit Cycle in the Longitudinal Motion of the USB STOL ASKA - Control System Functional Mockup and Actual Aircraft

1992-04-01
921040
The Japanese Quiet Short Take Off and Landing experimental aircraft named ASKA was developed and flight tested during 1977 till 1989. The control system hard and software were examined by the functional mock-up with using the actual hardware. The small longitudinal limit cycle was observed in the closed loop test when the Pitch Control Wheel Steering software was on in the mock-up testing. In this paper, first, the method to analyze and to expect the limit cycle based on the describing function was shown. The limit cycle was induced due to the nonlinearities in the automatic control mechanism. The nonlinearities in the hardware were examined to make the model to simulate the system on the computer. The method was shown effective to predict the limit cycle in the mock-up. Second, with using the flight measured dynamics, the limit cycle was concluded as on border line between existing and not, which coincides with the actual flight result.
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