The Image. 85% of information processed by the brain is visual. Therefore it is essential that in any synthetic training environment the visual medium be as realistic as possible, otherwise, the image would not support the illusion. Let’s face it. It would be hard to convince someone they were flying circuit training at Oakey if the buildings and runways didn’t look like those at Oakey and the terrain was tropical rainforest like the region south of Cairns!
To achieve this realism the images produced for the out-the-window visual display in the FF&MS are Computer Generated Images (CGI) as this is the current industry standard. Dedicated special purpose computers that run within the system called Image Generators (IGs) produce CGIs and send them to the projectors once they are corrected for position and orientation within the FOV. IGs are rather like the graphics boards on your PC, just on a larger scale. For example, your graphics board will perform texture calculations within the chips mounted on the board itself. By comparison, the IGs of the FF&MS’s visual system contain complete boards allocated just to performing the equations relevant to an object’s texture.
The images produced are essentially a series of shapes, or polygons, that are grouped together to form recognisable objects such as runways, buildings, tanks etc. To enhance the realism of the polygons, photo-realistic textures and shadings are draped over them in real time. In the FF&MS these polygons are stored within databases that are referenced to particular geographic locations. For example, when the runway at Oakey is selected, the computer only loads the polygons that will be seen from the position of the aircraft, thereby freeing up memory for other calculations.
Once selected from the database, the images are then presented to the aircrew in the appropriate size, perspective and position, thereby creating the impression of being within the familiar location of Oakey.
The most difficult part of creating this illusion is making the two dimensional world of the projected image appear as if it were indeed three dimensional. This is essential, as all of our flight operations require the intrinsic elements of depth and distance estimation for successful execution. To enable the visual system to create a realistic scene, the image is built to include real world elements such as: shading, static and dynamic shadowing, overlapping contours and known object sizing, to name a few.
But the structure of the visual scene is only one part of the illusion. The other element is, of course, the visual environment. Clouds, reduced visibility, storms, moving vehicular traffic, lighting, blowing sand etc., are all added to a scene as special effects. These are all created in the same fashion as any visual object, and they are selectable by the Instructor, as required to support the illusion required for the training sequence.
Overall the results are astounding and when combined with the appropriate digitally scanned and reproduced terrains the sense of flying in the real world visual environment is very realistic and quite powerful.In this area the FF&MS really is at the forefront of current capability and technology.
Motion. Historically, the motion system has been the most controversial sub-system in any debate about simulator fidelity. The effectiveness of motion on the maintenance of the illusion of flight will always be questioned, as these systems will never be able to reproduce sustained G. As this ability is not relevant to S-70A-9 operations, what has occurred instead is the development of two complementing sub-systems that faithfully reproduce the low G, short term, unstable environment of helicopter operations. The first, the Motion System, is designed to emulate the gross, rapid movement of the aircraft, whilst the second, the Vibration System, provides the finer vibratory cues associated with all rotary flight.
The Motion System. This sub system consists of large, rapid moving hydraulic actuators that are mounted in a series of three inverted "V"s, as can be seen below.
This configuration is common to most modern motion systems and affords the device the freedom to move in six distinct directions: Pitch, roll, yaw, heave (vertical plane), surge (fore and aft) and sway (side to side). Hence, this is known as a six DOF (Degrees of Freedom) system. A dedicated computer that acts in response to commands from the host provide the movement commands. Like all simulator systems, the motion system is designed to enhance the illusion of flight. This is achieved by inducing movement at a rate above the sensory thresholds of the human proprioceptive system, otolith organs and semi circular canals that is in tune with the movement of the visual scene. Basically, the brain senses the motion and the eyes confirm it, therefore you are moving at the rates and amounts demanded by your control inputs.
The problem with this set up, however, is that the motion system has an extremely limited travel when compared to that of an aircraft in flight. In the case of the FF&MS, this range of travel is approximately 36 inches. The limitation is overcome by washing out the rate of actuator movement immediately following the initial input to move comes from the computer and then returning the motion platform to its rest or neutral position. The deceleration and return of the motion platform is made at a rate that is beneath the human movement detection threshold and is made so as to prepare the system for the next movement trigger from the aircrew.
To illustrate this concept, imaging that you have just commanded a right roll to 900 AOB from straight and level unaccelerated flight. The motion platform would move at the necessary rate to allow the sense of movement commensurate with the control input and the movement of the visual scene. It would then immediately wash back to neutral. Thus, the appearance in the cockpit would be that you were at 900 AOB, but the motion platform would be at neutral if viewed from outside. It is this iterative process of movement that supports the illusion of flight despite the travel restriction of the actuators.
The vibration system. No one would deny that helicopter vibrations are essential to any faithful reproduction of the rotary environment. So, the FF&MS superimposes finer vibratory cues on the gross cues of the motion system. These cues are representative of the vibration patterns felt at the pilot seats of the S-70A-9 for all in flight and on ground sequences and are provided by the vibration system. Essentially, the vibration system is an extremely limited travel motion system that is mounted underneath the cockpit and on top of the motion platform. The sole purpose of the vibration system is to generate appropriate vibrations in response to the prevalent in flight conditions. With the system activated, the cockpit "floats" on small actuators that react to triggers sent from the Host computer.
The control loading system. Having the motion and the visual delivered to aircrew that are surrounded in a true to life cockpit may go a long way to supporting the illusion that the aircraft is actually flying. But the performance of the aircrew will suffer, as will the credibility of the device, if the control forces are not realistic.
The Control Loading System provides the forces at the primary flight controls to simulate the feel of the aerodynamic loads and artificial devices experienced in the aircraft. Essentially this is a series of hydraulic actuators, mounted beneath the floor of the cockpit, that respond to computer generated signals that emulate the forces felt at the controls of the aircraft for a given sequence. The basic configuration is shown below.
The control loading system provides all of these forces for normal and abnormal S-70A-9 operations
The flight deck. The flight deck system is mounted on the motion platform and contains the cockpit and the on-board Instructor Operating Station (IOS). The level of fidelity required for the S-70A-9 FF&MS stipulates that the cockpit must be a one to one reproduction of the real cockpit and that anything that aircrew interacts with must be functional.
For example, when the aircrew change a radio frequency, they would do it as they would in the real aircraft. The only difference being that when the radio frequency is changed at the radio control head in the cockpit, a command is sent to the host computer, which then generates responses which allows their calls to be "heard".
Some of the limitations to the design of the FF&MS cockpit design include fixed doors and windows and non-functional windscreen wipers. The cockpit doors and windows are fixed to protect the mirror system, which is mounted outside the cockpit, and it was not considered necessary to actuate the wipers as long as an appropriate visual solution was provided for flight in rain. (Which it was)
The on board IOS the S-70A-9 FF&MS is a contractor innovation. It consists of a forward facing electrical chair with front mounted touch screen computer interfaces. This configuration allows for a greater level of supervision for any on board instruction conducted from this station and allows comfortable access to all of the simulation controls.
The Instructor/Operator Station. The IOS is the control interface that enables the simulator to be used for training. Generally, its design incorporates all of the switches and monitors necessary to initiate and affect any of the sequences and environments for which the device has been developed. Whilst there are few legislative controls on the function and design of an IOS, it is a general rule that ease of operation and good ergonomics are essential to provide the operator the ability to monitor the sortie and operate that device simultaneously.
The FF&MS incorporates three stations from which the device may be operated: one on board and two off board. In addition there are also two hand held units which offer limited control for use in the cockpit. It is essential that the flexibility and control afforded by this design provide the ability to operate or instruct a mission from any seat, consequently, each of the three stations offer graphically oriented touch screen interfaces that allow control of both the simulator and training.
The software supported by the IOS offers the possibility to select from any pre programmed training mission or to develop "on the fly" sortie profiles. It is also possible to monitor the progress of a sortie, an individual radio frequency or crew station, insert a specific malfunction at a pre determined event or change configuration and environmental effects such as temperature or pressure, wind direction and speed or cloud layers and types.
The FF&MS IOS also provides the ability to record segments of the sortie for playback in the cockpit or on video, to print hard copies of aircraft tracks or screen displays, to display reference material onto the mirror system (ie. UFOs or Flight Manual) and to develop real time tactical missions.
The Future
A level 5 device is a very sophisticated training tool and it can be argued that, for training purposes, the current state of the art is close to the evolutionary pinnacle. After all, they will never actually replace the real aircraft. There is, however, continued development and as with all things computer this seems to be hardware driven. Bigger, faster, cheaper computers translate directly into more realistic software models, faster response times and larger information databases, all of which would further enhance the realism of the current environments. As computers and software modelling techniques will always be improving this doesn’t necessarily address what is often seen as the real limitation of today’s devices. The visual system.
Current image generation is provided through polygonal based images and colour light projectors, often presented onto a large mirror surface through a refracting screen. This provides the viewer with comparatively blocky, diffuse images for the visual representation of known terrains and objects. Advancements that show great promise and that are currently under development include pixel based images, which give the developer more control over shape, colour and shading and colour laser projectors that offer higher outputs, crisper lines and greater image control. Combined, these developments would provide a significant increase in the realism of the visual scene and therefore the total training environment.
Developments in Virtual Reality environments should also be considered as future training solutions. Poor visual presentations and cumbersome human interfacing presently limit the capability, but there is a significant effort being directed to increasing the realism of these devices with an eye on future aviation training.
Summary
The delivery and acceptance of the FF&MS into our training system only represents the beginning of the Corps’ transition to the synthetic training environment as all future acquisitions will rely heavily upon this form of training. It is therefore vital that, as users of these devices, we understand and embrace the capability, utilising it such that it enhances our current standards and methodologies, thereby ensuring that t does not merely supplant the use of aircraft within our current practices.
The illusion has arrived. We must now use the experience to compose our wisdom.
END
