The pinnacle of turboprop trainer-combat aircraft developed by Pilatus Aircraft is the Pilatus PC-21. The prototype made its first flight on July 1, 2002, and since then the PC-21 has steadily expanded its presence in global markets. What are the key features of this aircraft, and what is the secret behind its success?
TABLE OF CONTENT:
Concept
Historically, the training of military pilots required at least two different types of aircraft: a piston or turboprop trainer for basic instruction and a jet aircraft for advanced training of future fighter pilots. In the mid-1990s, Pilatus Aircraft began exploring the possibility of combining these two roles using a high-performance turboprop aircraft. Achieving this would not only reduce procurement costs but also preserve the operational economy typical of turboprop platforms.
During the conceptual design stage, Pilatus engineers did not rule out the creation of a jet trainer. However, they ultimately concluded that modern aerodynamics combined with a sufficiently powerful turboprop engine could deliver the required performance. The new aircraft was expected to reach a maximum operating speed of 685 km/h (Mach 0.72) and a cruise speed of at least 555 km/h. It also needed acceleration comparable to the jet trainer BAE Systems Hawk and a roll rate similar to that of the fighter Lockheed Martin F-16 Fighting Falcon.
Development work on the new trainer began in the mid-1990s using the Pilatus PC-7 MkII as a test platform. This aircraft was fitted with a much more powerful Pratt & Whitney Canada PT6A engine producing 1,600 hp and equipped with a five-blade propeller. It also received an experimental wing shortened by two meters and fitted with spoilers to compensate for the shorter ailerons. The heavily modified PC-7 took to the air in November 1997, demonstrating that a significant increase in roll rate and improved straight-line acceleration to levels comparable with jet aircraft was achievable.
Despite the encouraging results of the test aircraft, it became clear that simple upgrades to existing Pilatus designs would not deliver the technological breakthrough the company was aiming for. As a result, the PC-XX program was launched in November 1998.
Pilatus engineers were tasked with creating a training system superior to any existing trainer aircraft, whether turboprop or jet. The aircraft had to offer significantly better aerodynamic performance than existing turboprop trainers while maintaining low life-cycle costs. The ambitious goal was for this single model to handle the entire pilot training cycle, replacing the traditional combination of turboprop and jet aircraft. Even if the Pilatus PC-21 could not completely eliminate the need for advanced jet trainers, it was expected to raise the transition threshold to more expensive aircraft and reduce the number that would need to be purchased.
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Design
Although the RS-21 bears an external resemblance to the RS-9, it is essentially a new aircraft. It is powered by a significantly more powerful RT6A-68V engine, rated at 1,600 hp. The onboard systems have been substantially updated. Each crew station features three large and two smaller multifunction displays. The front cockpit includes a head-up display, while the rear cockpit is equipped with a repeater for its output. A digital fly-by-wire control system allows a wide range of adjustments to the aircraft’s handling characteristics, supporting pilot training from initial instruction to advanced stages. The aircraft can carry a payload of up to 1,150 kg on a fuselage-mounted hardpoint and four underwing hardpoints.
All previous models from the company featured an all-metal construction, and Pilatus opted to continue this approach rather than adopting widespread use of composites, allowing the PC-21 to be produced on the same assembly line as the PC-7 and PC-9. Some composite components, such as fairings, were still incorporated. A key design consideration was the use of modular components that could be quickly replaced, reflecting Pilatus’s goal of minimizing turnaround time and reducing maintenance costs per flight hour.
The most significant innovation was the wing design. Pilatus moved away from the constant-sweep wing characteristic of the PC-9 in favor of a higher-performance configuration, featuring a swept leading edge, a straight trailing edge, and wingtip devices. Compared with the PC-9 wing, it was smaller and carried a higher wing loading, enhancing maneuverability in turns to a level more typical of high-speed jet aircraft.
Additionally, the PC-21 wing eliminated the straight central section, resulting in a reduced wingspan (by 1.013 m) and a correspondingly smaller wing area. Like the concept demonstrator, the PC-21 incorporates hydraulically actuated interceptors that complement the shortened ailerons and engage after their initial deflection. This arrangement provides sufficient structural strength for the installation of flaps, enabling a stall speed of 150 km/h.
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Service
Despite its relatively high cost, the PC-21 has gradually established a presence in the training aircraft market. The Swiss Air Force received eight units, with deliveries beginning in April 2008. From January 2008, the PC-21 was delivered to the Republic of Singapore Air Force, which acquired 19 aircraft. These aircraft are operated by a private company under a public-private partnership and are permanently based at RAAF Base Pearce in Australia.
In November 2010, the first of 25 aircraft ordered by the United Arab Emirates took flight. Deliveries to Saudi Arabia and Qatar began in 2014, with those countries acquiring 55 and 24 aircraft, respectively. In 2015, Australia placed an order for 49 PC-21s, with deliveries completed by 2019. Jordan purchased eight aircraft in 2016 and subsequently added four more between 2016 and 2017.
A significant milestone for Pilatus was the PC-21’s selection in 2017 by the French Air Force to replace the Alpha Jet. The initial order was for 17 aircraft, with an additional nine acquired in 2021. Deliveries were completed in 2023. Spain also procured the PC-21 in two batches – 24 aircraft in 2020 and 16 in 2023 – with all units delivered by the end of 2025. Notably, Princess Leonor, heir to the Spanish throne, completed her flight training on the PC-21. Two aircraft are operated by Quinetic in the United Kingdom to train students at the Empire Test Pilots’ School. The most recent firm order was placed by Canada in November 2024 for 19 aircraft, designated CT-157 Siskin II, intended to replace the CT-156 (Beechcraft T-6A).
Potential customers for the PC-21 include Croatia, Bulgaria, Malaysia, Sweden, and several other countries. The aircraft continues to be purchased predominantly by financially capable nations for training purposes. In the light attack and trainer market, lighter aircraft such as the EMBRAER EMB-314 Super Tucano and Beechcraft T-6/AT-6 Texan II remain dominant, while the PC-21 occupies a higher-performance training niche. The PC-21 is replacing both turboprops – for example, substituting the PC-9 in Saudi Arabia and Australia – and jets, such as the Hawk in Switzerland and the Alpha Jet in France. A clear example is Spain, where the PC-21 has replaced two classes of aircraft: the piston-powered ENAER T-35B Pillan for initial training and the jet-powered CASA C-101 Aviojet for advanced training, in line with the aircraft’s original design concept.
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