(Radar Guidance by HUD for the STOL Experimental Aircraft ASKA)
INTRODUCTION
In recent years, the air transportation system of JAPAN has expanded rapidly but the building and enlargement of the airport system has been very difficult because of space and noise problems.
To help solve these problems the National Aerospace Laboratory(NAL), an annex institute of the Science and Technology Agency, started the Quiet STOL project in 1977. The goal was to develop a STOL experimental aircraft with Short Take off and Landing capability along with the reduction of community noise around the airport without sacrificing high speed cruising capability.
After a brief evaluation of several powered lift STOL concepts, NAL made a decision to develop an Upper Surface Blowing (USB) STOL experimental aircraft conversion of Kawasaki C-1 tactical transport using FJR710/600S engines as power plants. This engine was developed by NAL with funding from the Ministry of International Trade and Industry 1). * As a result of this selection, NAL started working on the first Japanese made four engine jet aircraft. The Aska was named after the ancient japanese era around the sixth and seventh centuries. Aska means flying bird and is shown in Fig.l.
In addition to the USB configuration and the FJR710/600S engines, the Aska has several other significant design features. Boundary Layer Control(BLC) avoids flow separation at the wing leading edge and over the aileron at high angles of attack. The Stability and Control Augmentation System(SCAS) provides good handling qualities for approach and landing at low speeds and steep approach and at low speeds and steep approach angles 2)3)
The Flight Path Control(FPC) system and the Pitch Attitude Hold/Rate Command modes of the SCAS are important for a powered lift aircraft such as Aska. The newly developed FPC lever is connected to the throttle drive motors and its position signal is also input to the SCAS for control of the spoilers. The spoiler signal is washed out to help compensate for the sluggish flight response of the aircraft 4).
*Numbers in parentheses designate reference at end of paper
Fig.1 Experimental Powered-lift STOL aircraft
"Aska"
In the landing approach, the air speed of Aska can be controlled by pitch attitude because of the back-side characteristics of powered lift aircraft. In this case a precise attitude control device such as SCAS and an accurate attitude display device such as a HUD become very important.
The HUD, which was developed since 1981 as a flight test support device for the experimental powered-lift STOL aircraft Aska, has been used as an accurate total flight instrument and as a precise landing guidance system 5)
Fig.2 HUD in the First Simulation Test
The HUD was developed by flight simulation and flight tests. The first flight simulation tests were done
