With the aid of computers, data highways, some relatively straightforward hardware and a year or two of programming, you can revolutionize life in the general aviation cockpit. It has already been done in fighters and airliners. Now it is the turn of the kind of light aircraft that a private pilot is likely to fly solo on airways. Virtually1 every pre-flight and in-flight job can be reduced to a keyboard routine and an integrated computer system can be organized to produce information, guidance and control in a volume altogether disproportionate to the amount of hardware used.
The reason behind the NASA exercise, called Demonstration Advanced Avionics System (DAAS), is that the general aviation pilot is going to have to live in a more and more complex airspace system, but may not have room or money to install all the new equipment which would make this safe and effective. Present moves towards reducing cockpit work-load are efforts to automate radio tuning and to integrate the autopilot and flight director. But NASA believes that modern computers, data highways and software, together with shared displays and controls, allow far more productive use of the basic information already available in light twins. Particularly, the navigation system can be made more responsive to flight planning requirements, and the navigation instructions in both horizontal and vertical modes can be passed directly to the autopilot.
In the DAAS system, the locations, call signs, frequencies and elevations of a set of VORs and DMEs are stored in the navigation computer and the computer will automatically select whichever of the navaids is best suited to2 define a succession3 of geographical waypoints inrerted by the pilot. DAAS will cause the navaids to be tuned automatically at the right moment. It will constantly compare the signals from the navaids by Kalman filtering to identify the best signals and ensure that they are adequate for navigation, and it will tell the pilot which aid is being used. Very little additional hardware is needed to do this job.
The navigation system can also take into account the safe or flight-planned altitude over the stored geographical area and can calculate descent angles required when changing altitudes. Hot fitted in DAAS, but foreseeable, is an autothrottle to automate the execution of climbs and descents. The DAAS system is designed to couple to ILS and to capture the localizer beam from acute4 angles. With a radio altimeter, the system could even be extended to automatic landing.
Extra help
The kind of extra help DAAS gives the pilot is that it will decide from the navaid frequency whether it should treat the appropriate altitude input as an airways minimum descent altitude at which it will level the aircraft off and sound the warning, or as a decision height, at which it also sounds a warning, but allows the aircraft to continue down towards touchdown. It will also automatically generate intermediate5 waypoints close to good beacons along the line between the starting and finishing waypoints of a long leg.
All the required information is inserted on individual "pages" in the display system of the main computer. The pilot selects from a "menu" of pages by pressing buttons beside the display and can select information for display on a separate key-board.
On two "flight status" pages, DAAS will, whenever asked, list true airspeed, groundspeed, wind speed and direction (calculated from TAS and groundspeed), percentage engine power (taken from engine indications), fuel remaining in pounds and in minutes of endurance, distance and time to next waypoint and estimated time of arrival overhead. Greenwich Mean Times6 is preset in the system.
On the cruise performance page, DAAS tells the pilot his propeller rev/min, manifold pressure and percentage power, fuel flow, miles/lb of fuel, TAS, groundspeed, ETA and fuel required to the next waypoint.
The checklist display is already a familiar feature in weather radars, but DAAS goes a long way further. After the pilot has inserted take-off gross weight and fuel load and detailed the location and weight of people and other items on board, DAAS tells him his centre of gravity location. This can be transferred to the Initial departure page and becomes available for use during cruise control. Similarly, DAAS will work out take-off speeds, normal and single-engined rates of climb and airspeeds, accelerate-stop distance, ground run and distance to 50ft for the actual aircraft weight, airfield elevation and temperature.
The DAAS warning system checks and warns of aircraft configuration items such as gear, flaps, doors, cowl flaps, trim settings and fuel pump settings, and also monitors that engine settings are within limits. It warns if low and high airspeed limits are reached and provides full altitude alert7 service. Conventional warning lights and sounds are supplemented by written messages in the electronic display.
The autopilot is actually based on a digital King general aviation system. Its main additional mode, apart from being integrated with the navigation system, is control wheel steering. The pilot can fly manually without disengaging the autopilot and the aircraft is brought back to datum attitude or settles at a new height when the controls are released.
4500 знаков
Notes:
1. virtually – in fact
2. to suit to – подходить к...
3. succession – последовательность
4. acute angle – острый угол
5. intermediate – промежуточный
6. Greenwich Mean Time (GMT) – среднее время по гринвичскому меридиану
7. alert – (зд.) быстрый
UNIT 17
