Eurocopter X3 Mystery Cache

The Eurocopter X³ (X-Cubed) is an experimental high-speed compound helicopter developed by Eurocopter (now Airbus Helicopters). A technology demonstration platform for Eurocopter "high-speed, long-range hybrid helicopter" or H³ concept, the X³ achieved 255 knots (472 km/h; 293 mph) in level flight on 7 June 2013, setting an unofficial helicopter speed record

General characteristics:

• Crew: 2
• Gross weight: 5,200 kg (11,464 lb)
• Powerplant: 2 × Rolls-Royce Turbomeca RTM322-01/9a[44] turboshaft engines, 1,693 kW (2,270 hp) each
• Main rotor diameter: 12.6 m (41 ft 4 in)
• Main rotor area: 124.7 m2 (1,342 sq ft)
• Propellers: 5-bladed (two tractor propellers gear driven from main engines)
• Main rotor: five-bladed from the Eurocopter EC155

Performance:

• Maximum speed: 472 km/h; 293 mph (255 kn) at roughly 10,000 ft (3,048 m)
• Cruising speed: 407 km/h (253 mph; 220 kn)
• Service ceiling: 3,810 m (12,500 ft)
• Rate of climb: 28 m/s (5,500 ft/min)
• Tip speed: 0.91 Mach
• Autorotation: 2,800 f.p.m