The F28 is powered by a pair of Rolls-Royce Spey turbojet engines; dependent on model, these would be were capable of generating up to 9,850lbf / 43.9kN of thrust. While the feature was available at the time, Fokker chose not to equip the engines of early F28s with a water-methanol injection system as they determined that the engines already possessed sufficient performance even when being flown under hot-and-high conditions. The majority of onboard systems are designed with simplicity in terms of operability and serviceability; there was no hydraulic system, actuation of the undercarriage and steering relied on pneumatic pumps instead. However, the F28 was outfitted with comparatively advanced electronics, as Fokker's design team viewed this factor as directly relating to overall competitiveness. One uncommon feature of the F28 was the movable split-sections installed upon the tail cone; these would be hydraulically-opened outwards to act as a variable air brake. A similar approach had also been used on the contemporaneous Blackburn Buccaneer strike fighter and on the later-built British Aerospace 146 regional airliner. The design is unique in that it not only slows the aircraft down rapidly, it can aid in rapid descents from economic cruising altitudes and also allowed the engines to be set at higher RPM which helped eliminate 'lag time'. This means the engines respond faster if needed for sudden speed increases or go-arounds on the approach to landing. The Fellowship had a retractable tricycle landing gear which used large low pressure tyres, enabling the use of unpaved airstrips. The use of anti-skid brakes on the main wheels of the undercarriage also contributed to a shorter landing run. A variant of the F28, equipped with an extended fuselage, was named "F28-2000"; this model could seat up to 79 passengers instead of the 65 seats on the F28-1000. The prototype for this model was a converted F28-1000 prototype, and first flew on 28 April 1971. The models "F28-6000" and "F28-5000" were modified F28-2000 and F28-1000 respectively; the main features of these models was the addition of slats, a greater wingspan, and the adoption of more powerful and quieter engines. Both the F28-6000 and F28-5000 failed to become commercial successes; only two F28-6000 and no F28-5000 were ultimately built. After being used by Fokker for a time, the F28-6000 were sold to Air Mauritanie, but not before being converted to F28-2000 standard.