Why is the rafale so slow?

Dassault's published maximum speed is Mach 1.8 at altitude, about 1,915 km/h (1,035 kn), and 1,390 km/h (750 kn) at sea level, where the airframe limit rather than thrust sets the ceiling. French test pilots have reported supercruise, sustained supersonic flight without afterburner, at about Mach 1.4 with a load of six air-to-air missiles. In useful, sustained speed the Rafale is therefore ahead of most rivals, even if its brochure figure is lower than the Mach 2.2 of the Mirage 2000 it replaced or the Mach 2.5 of the F-15.

Very high Mach numbers require variable-geometry intakes with movable ramps that slow the airflow before the compressor. They are heavy, complex and costly, and they only pay off above roughly Mach 2. The Rafale uses simple semi-circular intakes with no moving parts, which saves mass, reduces radar reflections and simplifies maintenance. The airframe is optimised for a different corner of the envelope: low-speed carrier approaches, high instantaneous turn rates from the canards and delta wing, and long range with heavy loads on 14 hardpoints. Engagements above Mach 1.5 have been almost nonexistent since the 1970s, because afterburner fuel consumption is enormous and external stores limit any fighter far below its clean speed.

Every fighter designed since the 1980s made the same trade. The F/A-18E/F tops out around Mach 1.6, the F-35 at Mach 1.6 and the Eurofighter Typhoon at Mach 2.0, while the Su-35 keeps Mach 2.25 thanks to larger, adjustable intakes. What matters to a modern air force is acceleration, transonic agility, missile range and sensor fusion, and in those areas the Rafale is regularly rated near the top of its class.