Flight Simulators Come of Age

Although these analog computers, once calibrated, provided reasonably accurate simulation, they did have some technical shortcomings. Calibration was complicated and lengthy, maintenance was costly and time consuming and modification was difficult, often entailing the rewiring of the entire system.

The majority of these shortcomings were eliminated with the development, in the 1960s, of the digital computer. This made it possible to solve all the aerodynamic and logical equations needed for flight simulation, provided the program could be repeated fast enough for the pilot to experience no delay in receiving information on his instruments.

As is common with any technical advance, transition from analog to digital computation was not made without some initial difficulties. Early digital simulators suffered from reliability prob- lems, simulation engineers had to be retained and software programmers either had to be trained or lured away from other industries which had already embraced the digital computer.

Once these problems were solved, the digital computer became the first choice for manufacturers of flight simulators. The next technical advance came in the area of motion simulation, driven by the need to improve training for the new wide-bodied aircraft of the late 1960s, Motion systems up to this time. had only provided three “degrees of freedom” (types of movement): pitch, roll and heave. The advent of wide-bodied aircraft necessitated better training to enable the pilot to also be able to cope with power loss.

Training was later improved by adding left and right motion to the existing three degrees. Various approaches were developed. including a system which employed a hinge at the rear of the sim- ulator around which the whole machine would rotate when left or right motion was required. The final result of development efforts was the device in common use today- the six degrees of freedom motion system which provides upward, downward, foward, backward, left and right movement as well as the rotational motions of roll, pitch and yaw.

The six degrees of motion system was established as the standard about 20 years ago; there has since been a considerable amount of refinement, although the exterior appearance of simulators has changed little. One major concern was to reduce friction levels within the hydraulic actuators, which are the major components of the modern simulator motion system. For the pilot in training, this friction reduction results in more realistic and smoother simulation of an aircraft’s motion performance.

However, despite all the advances in motion technology, the maximum movement of a motion system is still only about 1. 5 metres in any direction. This limitation means that, while the pilot is flying the machine, the simulator engineer has to spend a great deal of time adjusting the motion response to obtain the most realistic performance. “Motion tuning” is more an art than a science; it combines actual data with special effects to convince the pilot that he is really flying an aircraft rather than sitting in a simulator bolted to the floor.

Early flight simulators could only be used for instrument flight training, since they had no visual attachments to replicate the “outside world”. This meant that the simulator could not be used for any realistic training in the landing or takeoff phases of flight. This situation changed with the introduction of closed circuit television model board visual systems in the mid 1960s. These devices consisted of a TV camera mounted on a gantry which traversed a model board of an airport area. Driven from the main computer simulator, the camera was positioned over the topographical board in such a way that its lens acted as the pilot’s eyes. Images from the camera were then projected onto a screen in front of the pilot.

Model board visual systems had only limited success, since they suffered from the same problems that had plagued analog computer systems. However, they proved it was feasible to use a simulator to train pilots in the critical landing and takeoff phases. It was the development of the fast digital computer and computer graphics which made it possible to present the pilot with a picture of approach and runway lights at an airport.

Early visual systems had limitations and suffered from such problems as “pilot induced oscillations”. This was caused by delays in the rate at which the picture presented to the pilot was updated, he tended to go faster than the visual system and when trying to correct this made the simulator oscillate. The problem was solved by speeding up processing of the light points on the screen in front of the pilot.

Today’s flight simulators embody all the elements reviewed here-fast digital computers, low friction (hydrostatic) motion systems and day/dusk/night wide angle visual systems. They are used for both checking and training airline pilots worldwide.

Since the early flight simulators could only be used for Instrument training and practice, the approval process by civil aviation authorities was relatively simple. After initial evaluation, the simulator would be annually checked to make sure it had not “deteri orated”. Advances in computer, motion and visual technologies by the late 1970s made it apparent that all airline pilot training and checking could be accomplished In a flight simulator. With this in mind, the US Federal Aviation Administration developed the “Advance Simulation Plan”.

In essence, this Plan permitted airlines to transfer training from actual aircraft to simulators in a specified manner, on the understanding that the carrier would commit itself to upgrading its simulators, using the latest technology, in a given period of time. It proved to be a great success and by the mid 1980s a large proportion of pilot training and checking was undertaken in flight simulators. With the transfer of pilot training into the simulator, the testing and evaluation process for the machine had to be made more rigorous.

An approval test guide has been developed which checks the simulator’s performance and response against that of an actual aircraft. A comprehensive approval test is made at the time of installation and then on an annual basis. Additional tests are run every three months. The period between evaluations has gradually been extended as confidence has grown in the “repeatability” or maintained precision of the simulation.

Flight training-the decade of technology The development of the flight simulator presented the airline industry with a new example of the traditional challenge: man- agement and use of technology. The task facing flight training managers in the 1970s was to adapt instruction techniques to include the effective handling and processing of information, In the early days of flight training, the emphasis was on flying the aircraft (“stick and rudder”) and on developing the necessary instrument flight rules (IFR) skills, all centred around one person the captain. Training was mostly technical, lecturers stood up in front of trainees like schoolmasters, using chalk and blackboard, while flight training took place in the actual aircraft. Subsequently, flight engineers, navigators and radio operators were brought into the flight crew, but training methods were not very efficient and, when using actual aircraft, involved a relatively high risk factor.

Information and the resulting Intelligence flow was “front loaded” and built on the captain’s base of experience. Communication amongst the flight crew was minimal, with the result that individual crew members wanted to “know everything” and had to be trained to this end.

Typically, ground school lasted four weeks, flight training was 16 to 24 hours in the aircraft, depending on which crew member was being trained. Line flying with an instructor took another 20 to 40 hours. On average, as many as three months could elapse before the pilot was retrained and gainfully employed in his new position. Strangely enough, lost productivity was not generally considered in the management of flight training. Today, by contrast, a pilot can be line flying with an instructor, having mastered the electronic aircraft, in as little as 24 working days.

The “high tech” jet transport, with its swept wings, high speed aerodynamics and routine high altitude operation led to an intensification of the technical aspects of flight training. Technology finally came to the rescue in the 1970s as a teaching aid and reinforcer of the theories still being taught in stand up lectures.

The arrival of widebody jets resulted in a major shift in training philosophy to the “need to know” concept and consequently a typical ground school course was shortened by about seven days. Technology in the Boeing 747, McDonnell Douglas DC-10 and Lockheed L1011 allowed the aircraft designer to deviate from the linear thinking process, by designing the many on-board systems to be “managed” through the use of small computers. As a result, the training process lagged behind the development of the aircraft and the airlines had to scramble to catch up. An immediate effect was the changeover to training merely what the pilot needed to know to actually fly the aircraft, that is to say, only the elements of the system that he was able to control or correct. The availability of the Audio Visual Computer Assisted Tutor (AVCAT) and the first visual systems for simulators greatly aided this process. Unfortunately, aircraft technology again advanced rapidly in the1980s and training again fell behind. Nevertheless, the gap is beginning to close through advances in the way information is now processed.

Ground schools will in future be able to use technology to teach 90-98% of all the “need to know” systems, their normal and abnormal operating procedures and limitations, as well as show in a real time manner, the internal mechanisms and operation of the systems. This will be done using PC driven Computer Based Training (CBT) systems, which make it easy to amend course material. High quality monitors (480+ lines per screen) make it possible to design plans for aircraft systems lessons with all cockpit instrumentation working at the same size, rate and colours as in the real aircraft.

Technological advances will result in visual systems that provide full colour, seamless, wraparound 200 degree lateral vision and approximately 20 degree vertical vision, as well as details such as shadows, textures, skid marks, snow or ice covered runways, drifting snow or sand, thunderstorms, dawn, dusk, “fog bank” weather and gate and ramp information.

Data processing technology can use mini computers to manage more sophisticated full flight simulators (FFS) with six axis motion systems as well as the integration of the complex interface to the visual systems.

Finally, technology has brought forward the development of low cost cockpit and flight management system (FMS) trainers, now named flight training devices (FTD). These will augment the actual flight simulatoras a “training reinforcer” and offer the possibility in the future of lowering training and capital acquisition costs.

Computer based training, in concert with flight management system trainers are the tools currently necessary for a properly phased approach to learning, prior to moving on to the flight simulator itself. The latest technology aircraft, such as the Airbus A320 and Boeing 747-400, enable this approach to learning to be applied with great success. However, it is in the newly emerging area of the FTD that the greatest changes are occurring.

The FTD is a computer driven trainer which uses manufacturer’s data to emulate the specific flying characteristics, flight management and aircraft systems of a given type. Updating or modification can be made by simple software redesign and installation is easy because of the system’s modular concept. Maintenance training and troubleshooting can also be added to the unit if required. The introduction of the “electronic” aircraft has training managers asking whether there is really a need for additional capital intensive simulators. With the difference in fidelity between a top grade FTD and simulator almost indistinguishable, training could be transferred to the FTD.

Airlines will now be able to develop individual programs depending on their own philosophies. Some will no doubt opt for greater emphasis on FTDs and reduced time in the more expensive full flight simulators. Greater skills in “resource management” and information processing are now required because the pilot can find himself out of the loop.

The latest generation of aircraft is unique and should be acknowledged as such. Prior to the advent of the electronic, or “glass cockpit” aircraft, the pilot was directly in the operating loop. Aircraft like the A320 and 747-400 make it possible to offload the pilot to the extent that he or she is in more of a management role. The workload of the pilot is reduced with respect to monitoring displays and physical control, enhancing effectiveness. On the other hand, pilot workload can be increased in a constructive fashion at crucial times because of the capabilities of the flight management systems. Consequently, pilots no longer need the same degree of training in the physical handling of the controls to operate the electronic aircraft effectively but need a training system that allows more time to reinforce their flight management skills. A simple, effective and reasonably priced solution to this has arrived in the form of the FTD.

Technology has impacted on the management of training and the allocation of resources in a variety of ways:

• Ground school time can be shortened, while allowing a balanced mix of in-depth technical and need-to-know information to be presented through computer based training;

• Flight training devices can be used to improve and reinforce the knowledge transferred during CBT based ground school, allowing expensive full flight simulator training to be reduced;

• A higher quality training product can be offered, despite the greater technical complexity of modern “electronic” aircraft;

• Time spent on training can be reduced, thus improving line pilot productivity;

• The upgrade of first officer to captain, second officer to first officer and the training of newly hired pilots to line competent status can be undertaken without actual aircraft flying time;

• Actual aircraft flight training can be eliminated;

• A pilot can experience personal satisfaction in fulfilling his role on a new technology aircraft;

• The flight safety risk factor will be reduced; and

• The impact of pollution, noise and aircraft movements on the environment will be lessened.

We are now able to use technology to train pilots on modern aircraft to a higher standard than was previously attained on older generation equipment. The pilot’s role has changed from being a linear thinking “operator” to a non linear “manager”, integrating a greater volume of high quality data at lower cost, with higher productivity and enhanced safety levels. Reprinted courtesy ofthe IATA Review.