INTRODUCTION

This invention relates to an aircraft navigation trainer, and in particular it relates to a system cur¬ rently adapted for use in helicopters, but which can be used in other training situations where it is ad¬ vantageous to train in a fixed location instead of during actual flight.

It is already known to use apparatus for simulating radar displays and as an example we refer to the speci¬ fication of Canadian Letters Patent No. 948,314, issued May 28, 1974 of Adolfo Figueiredo granted to Redifon Limited of Great Britain, which is directed to the training of military and other service personnel, and which provides a simulated radar display of own and enemy craft, weapons and other targets and includes a digital computer to which is fed the data for display^ That device is not adapted for navigation training and is based on a conventional radar screen not suitable for navigation training as envisaged according to this invention.

There is in use a system known under the military equipment number AN/ASN-128 to which this invention relates and in which an aircraft receives flight data from sensors in the aircraft and combines this data with further data received from ground-reflected radar signals and combines this in a computer to give the navigator the necessary data for flight computation, and this AN/ASN-128 consists of three units - a Receiver- Transmitter Antenna which transmits four microwave beams to the ground and receives the Doppler-shifted returned

beams; a Signal Data Converter which derives Doppler shift frequencies from the four received beams, accumu¬ lates aircraft heading, roll, and pitch data from other aircraft sensors, and combines them to form composite flight data; and the Computer-Display Unit (CDU) which performs continuous navigation computations on the composite flight data, and provides the cockpit aircrew interface via its front panel control switches, key¬ board, and displays.

Because of the ergonomic complexity of some of aircrew interactions a long period of training is des¬ irable to establish and maintain aircrew efficiency in the use of the system.

The aircraft navigation trainer of this invention generates signal and power outputs equivalent to those supplied to the AN/ASN-128 CDU during flight by the Doppler radar components of the navigation system. When coupled to a CDU it will provide a self-contained ground training facility requiring only a mains power outlet. -=— Aircrew can then practice operator interactions with a Doppler navigation system driven by simulated flight conditions, including wind disturbance. Simulation of abnormal or fault conditions is also possible.

GENERAL DESCRIPTION

The Doppler Radar Simulator (DRS) which is the subject of this invention is preferably housed in a suitcase style carrying case, and is rugged enough for transport as baggage on a commercial aircraft. The arrangement is such that it is possible to simply and quickly couple a CDU both mechanically and elec¬ trically to the Doppler Radar Simulator (DRS)in the same frame or suitcase. The two units, which then form a navigation training station, may be operated, trans-

ported, and stored together. Such an arrangement may afford economies through the use of existing CDU stocks, e.g. spare units, in training stations. The permanent coupling of a DRS and a CDU as a portable training station is of course also possible. It is however not necessary to form a single mechanically integrated unit as the DRS may be housed in the suitcase, with connection to an external CDU via an electrical cable.

The DRS may be broken into a Flight Simulator and a Power Supply. In broad terms the Flight Simulator of the DRS allows the operator/trainee to set up desired flight conditions to be simulated via a control panel. These are transmitted to the CDU, which reacts exactly as it would to real flight data coming from the other elements of the present system. The CDU is thus exer¬ cised in a realistic way by the simulated flight, allow¬ ing the trainee to practise data entry and retrieval operations via the CDU front panel.

In its basic form the invention comprises an air- ^■*"" craft navigation trainer to simulate the data supplied to the cockpit aircrew of an aircraft, particularly a helicopter, arranged as a ground based unit and com¬ prising a Computer Display Unit (CDU) as used in the aircraft, an Operator Interface connected thereto and arranged for entry of flight data in the form of assumed aircraft and wind speed and heading, setting of aux¬ iliary input conditions, and display of system status, a Flight Data Processor arranged to convert user-entered flight data into appropriate form for acceptance by the CDU, a CDU Interface arranged to handle the serial transmission of flight data and auxiliary interfaces to the said CDU, a power supply, and means for support-

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ing the CDU, the Operator Interface, the flight data processor, the CDU interface and the power supply includ¬ ing mechanical and electrical interconnecting means.

THE DRAWINGS

To enable the nature of the invention to be fully appreciated an embodiment thereof will be described with reference to the accompanying drawings in which:

FIG. 1 shows the proposed packaging of the Doppler Radar Simulator and a CDU in a suitcase to form a port¬ able navigation training station.

FIG. 2 shows a typical keyboard entry panel for operator control of the simulated flight. Other data entry means may be used instead.

FIG. 3 is a block diagram of a navigation train¬ ing station using the aircraft navigation trainer (ANT) .

FIG. 4 is a block diagram of the Flight Simulator Unit within the ANT.

Referring to the block diagram of the navigation training station (FIG. 3):

The Flight Simulator 1 duplicates the flight data generation functions of the Receiver Transmitter Antenna (RTA) and the Signal Data Converter (SDC) of the AN/ASN- 128 Doppler navigation system and comprises; an Operator Interface 4 for entry of flight data in the form of aircraft and wind speed and heading, setting of auxiliary input conditions, and display of system status,

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a Flight Data Processor 5 which converts user- entered flight data into appropriate form form acceptance by a Computer-Display Unit (CDU) 3, a CDU Interface 6 which handles the serial transmission of flight data and auxiliary signal interfaces to the CDU 3, and affects the power switch on sequencing as required by the CDU.

The Power Supply 2; regulates the mains input to provide power to both the Flight Simulator 1 and the CDU 3.

The Computer-Display Unit 3; makes continuous navigation computations on processed flight data and displays navigation information via digital readouts, allows operator entry of navigation data, mode selection and control of data display via front panel switches and keyboard, outputs "TEST" signal to request transmission of test data in test mode, requests supply of regulated supplies via ON/OFF signal.

Referring to the block diagram of the Flight Simu¬ lator (FIG. 4):

The Operator Interface 4; allows operator entry of aircraft airspeed and heading, allows entry of a wind vector (speed and dir¬ ection) to simulate a realistic flight disturbance, passes the aircraft and wind velocities to the Flight Data Processor as "RAW FLIGHT DATA", displays essential system status,

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provides for operator entry of auxiliary CDU controls, including simulated fault conditions such as loss of Doppler data or an AN/ASN-128 mal¬ function.

The Flight Data Processor (5); exerts supervisory control over the Operator Interface, combines the aircraft and wind velocity infor¬ mation from "RAW FLIGHT DATA",

^* assembles "PROCESSED FLIGHT DATA" by manipu¬ lating airspeed and heading into the forms expected by the CDU, and adding dummy pitch, roll and an¬ tenna calibration data,

^* controls the transmission of "PROCESSED FLIGHT DATA" to the CDU via the CDU Interface, substitutes special test data for the normal flight data when so demanded by a CDU "TEST" mode. substitutes corrupted data, for normal flight or test data to simulate fault conditions.

The CDU Interface (6) ;

' accepts "PROCESSED FLIGHT DATA" and timing control signals from the Flight Data Processor and transmits the data to the CDU over the "SERIAL FLIGHT DATA" link, provides CDU discrete auxiliary signals (e.g. P.S. FAIL), communicates CDU "TEST" status, along with its own internal status, to the Flight Data Pro¬ cessor via "CDU INTERFACE STATUS" signals. switches power supplies to the CDU in response to the CDU power turn on control.

DETAILED OPERATION OF THE AIRCRAFT NAVIGATION TRAINER (Refer FIG. 4)

The heart of the ANT is the microprocessor based Flight Simulator 1, which comprises the Operator Inter-

face 4, a Flight Data Processor 5, and a CDU Interface 6, in which:

(a) The Operator Interface (4) allows operator entry of aircraft and wind velocities via a keyboard control panel (FIG. 2). He is able to enter aircraft airspeed in the range 0 to 999 knots in one knot steps and heading from 0° to 360° in one degree steps. A dis¬ turbing wind may be specified over the same range. Flight speeds much faster than real life may be of some advantage in the training environment to simulated flight times. Numeric displays of speed and heading provide feedback for the data entry operations. Other status lamps advise of successful acceptance of the data by the Flight Data Processor ("CURRENT FLIGHT" lamp), the current data type being entered (e.g. "WIND", "HEAD¬ ING") or advise against unusual operating states (e.g. failure detections during self test modes, an attempt to enter invalid data ("BAD INPUT")). Speeds and head¬ ings are entered in absolute values, although it would be possible to enter incremental changes from existing -te¬ states with a minor alteration of key designations on the keyboard. A typical key entry sequence for head¬ ing entry of 123° would be [HEADING] - [l]-[2]-[3]- [ENTER], The "CURRENT FLIGHT" indicator turns on to indicate acceptance of the new heading data by the Flight Data Processor. A rotary control switch allows the operator to choose between normal and abnormal simulated conditions. Abnormal conditions include the loss of Doppler radar returns or the occurrence of an AN/ASN-128 malfunction.

(b) The Flight Data Processor (5) forms composite flight data by combining the aircraft and wind veloc¬ ities from the Operator Interface and adding to it dummy conditions of roll and pitch (0° for both) . It then converts these into a form suitable for trans¬ mission to the CDU. One such conversion is the trans¬ lation of airspeed into the equivalent pattern of Dop¬ pler beam returns which

antenna in real flight. The Flight Data Processor con¬ tinuously passes this composite flight data to the CDU via the CDU Interface for use in navigation compu¬ tations.

(c) The CDU Interface 6 transmits the composite flight data to the CDU in a serial data stream whose timing and format are controlled by the Flight Data Processor. It also transmits minor discrete signal lines from the Flight Simulator to the CDU and vice versa, and passes switched power to the CDU.

The Flight Simulator 1, in addition, supports internal self test functions, and supplies special test data instead of flight data when the operator places the CDU in its "TEST" mode. Corrupted data is transmitted when Doppler loss or malfunction conditions are requested through the Operator Interface 4.

Both the CDU and the Flight Simulator are provided with regulated dc power by the Power Supply 2 function of FIG. 3. This derives regulated supplies from mains input and provides protection against failures within those supplies.

PHYSICAL REALIZATION

The Flight Simulator comprises:

(1) The Operator Interface 4, consisting of a front panel 7 with keyboard 8 displays 9 and control switch 10 controlled by a dedicated microprocessor. The control switch stations may be successively RESET, RESERVED, WATER MOTION, NORM DOPPLER LOSS and MAL¬ FUNCTION while the displays show AIR SPEED, HEADING WIND EFFECT and BAD DATA. In the experimental version accord¬ ing to this invention this communicates with

the Flight Data Processor 5 via a parallel link whereas a serial data link may be used in the operational model;

(2) The Flight Data Processor 5 which may be built from standard 8 bit microprocessor modules;

(3) The CDU Interface 6, comprising a specially designed transmitter circuit board and a matching re¬ ceiver used for self test purposes, and a power supply switching card which controls the turn on sequence of CDU voltage supplies.

The power supply 2 may be built from commercially available voltage regulators.

The two units, namely the Flight Simulator 1 and its associated components in the form of the Operator Interface 4 and the CDU Interface 6, and the CDU 3 are preferably mounted in a suitcase 11 having a pivot¬ ed frame 12, the unit 3 being also supported on the pivoted frame 12.

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