A new development programme from Pilatus Aircraft uses the latest technology to reduce pilot and weapons-system-operator training costs
The new emphasis is on a structured progression towards mission-system management. On 11 November 1998, Pilatus Aircraft Limited launched a new development programme aimed at using the latest technology to reduce pilot or weapons system operator (WSO) training costs. The programme was to produce an integrated training system that included a completely new aircraft and the associated synthetic training environment. Key targets were to maintain parity with the purchase price and operating costs of current turboprops while pushing training capabilities into the jet-trainer arena. The training system was to be easily upgradeable to reflect the new emphasis on a structured progression towards mission system management.
A completely new programme was considered because of recent substantial technical advances in displays and computing and because of the different transacting framework of large markets. The result is the PC-21 training system.
Frontline demands
The PFI transaction framework will impose an additional set of demands on training-aircraft development.
The skills required of a graduate pilot should be a direct consequence of frontline demands, varying considerably between air forces and roles within them and changing as new tactical doctrine and new equipment is introduced. Unfortunately, new equipment is expensive, budgets are reducing and training is subordinate to operational activity in many air forces.
To generate an airborne war-fighting capability at the lowest possible cost, the training aircraft will have to be available, unobtrusively, for 30 years and be able to accommodate changing training need. This is no small task, compounded by demographics, equal-opportunities legislation and the recruitment pool insofar as input standards are widening to accommodate these changing expectations.
Of course, outputs to various roles must be consistent regardless of input. Long-period demand will vary as a function of recruiting and the weather will affect short-period demand if graduation dates are to be achieved. Demand can be satiated by capacity, changing needs by major upgrades and longevity achieved by mid-life structural modifications so nothing new so far.
Pilot-training throughput is not often subject to violent fluctuations, outputs can be measured, contracts can be long-term and there is plenty of scope for innovation and third-party involvement. Most importantly, flying training is bankable just the ticket for a partnership or PFI if the decision is not to commit to a traditional transaction.
A PFI-transaction framework is centred on providing a service where large fleet sizes and costly in-service support is an expense rather than a revenue stream. Demands on the development of training aircraft are very different from those of their predecessors.
A new platform
Technology has changed and value for money from a training aircraft can be achieved only by addressing the platform and the avionics fit together.
Clearly a change in priority from pure handling skills to systems management places less emphasis on aerodynamic performance and more on the avionics fit. So why develop a new platform? From a financial perspective, whole-life cost and associated risk is minimised if the platform is easily repairable, maintainable and predictable. Dimensional accuracy across a fleet can be achieved by using modern fabrication techniques.
If a modification were required, the part should fit every airframe in the fleet, minimising repair cost and downtime. The latest maintainability concepts are easy to design into a new platform but almost impossible to retrofit into existing designs. Improved accessibility, better component selection and smart relationships with suppliers reduce turn-round times and maintenance man hours per flight hour. They also minimise the risk and impact of an aircraft on the ground.
For industry, perhaps the most important aspect of PFI is predictability. How the aircraft will hold up in service has to be known before a life-cycle cost and risk premiums are calculated. Old designs rely on structural fatigue tests using a specific loads spectrum. If the mission spectrum changes, a new test may be conducted or extrapolation considered. For a new design, finite element modelling allows longevity and structural harmonisation to be incorporated. A structural fatigue test is used to verify predictions and extrapolation becomes less of an art and more of a science with a reduction in risk. Modern, rather than exotic, materials add to predictability and low life-cycle costs.
The avionics architecture and hardware should be configured to survive the test of time. Much new thinking in flying training is about training for systems management but requirements will change as the syllabus adapts to serve the frontline. Open-architecture mission computers and large, active-matrix liquid crystal displays (AMLCD) confer a number of advantages over previous technology. First, they have higher mean-time-between-failure (MTBF) rates than their predecessors and are much more flexible. If a front-line aircraft has a particular display format or even analogue displays, then that format can be projected onto a large glass AMLCD. In other words, avionics architecture and hardware should be carefully configured to survive the test of time.
The great enabler
When processor technology changes, software should not have to be re-written. When analysis calls for a change in functionality, it should be quick and inexpensive. Screens should be able to change as display technology advances and all should keep pace with processor technology, the greatest enabler in this field.
Current training aircraft have avionics systems capable of performing a very specific function without scope for rapid and inexpensive change. Modern avionics architectures using open-system computers allow training system designers great scope for innovation, adaptation and upgrade. Developments will extend the horizon farther and designers’ architectures will have to cope.
The PC-21
The concept of PC-21 is value for money; push the low-level speed and climb rate of the turboprop into what was exclusively jet territory. Make it handle benignly for basic students and in a representative sense for advanced and tactical training. Incorporate a state-of-the-art avionics system that will remain so. Use the latest technology in development, fabrication and assembly to control cost and quality.
The PC-21 development programme was launched in 1999 after two studies, the first a market survey that identified a clear niche for this type of aircraft basic and advanced flying training, including mission-systems management, at turboprop operating costs. In parallel, a proof-of-concept aircraft (POC) was built to test the engine, power-management system, handling and, later, the avionics system. The result was very positive. A PC-7 MkII was converted to accept development systems. Engine power was increased from 750 to 1500SHP and then to 1600SHP. A five-blade aluminium prop was fitted, replaced later by carbon fibre and then graphite/titanium. Such power would be difficult for a student pilot to handle but a sophisticated engine-management system regulates power as a function of airspeed. This gives a benign take-off performance but moves the aircraft into a different category of low-altitude cruise speed.
The programme is on target to make a PC-21 fleet available to a launch customer in 2004. In addition to a powerful engine, configurable for the appropriate training stage, the aircraft has selectable automatic yaw compensation. The wing loading is high to improve low-level ride and to provide representative handling for simulated attacks and formation manoeuvring. It is swept to cope with high-dive velocities and has an aileron/ spoiler combination that gives a roll rate equivalent to the latest generation of front-line fighter aircraft. The powerful flap system keeps the stall speed low.
The avionics system is based on open architecture computers that far exceed the performance of most front-line fighters. There are three large AMLCD displays in each cockpit and, of course, HOTAS, a HUD and an up-front control panel.
The greatest innovation is in the software load that minimises student time in the training system and also copes with syllabus and role changes. Much thought has gone into the instructor/student relationship and into optimising instructor solo time.
Focus on quality
The PC-21 does not replace the PC-7 MkII or PC-9 that are being continuously developed to serve the market segment for which they were designed. Instead, PC-21 encompasses the role set of the current range of turboprops while extending well into traditional jet- trainer territory. There will be a substantial saving for every flying hour the PC-21 takes out of a jet syllabus. In two studies on large air forces, the cost to take a student to wings graduation was reduced by over 50 per cent.
Technological advances have extended employment for turboprops, it is time jet trainers moved to the right in capability and took the pressure off front-line aircraft.
