Boeing's MD902 Explorer was certificated to Category A standards on 11 February by the US Federal Aviation Administration, allowing the aircraft to continue flight after failure of an engine, even during take-off.

The helicopter is an upgraded version of the initial MD900 Explorer, with more powerful Pratt & Whitney Canada PW206E turboshafts, an upgraded transmission, improved integrated instrument display system software and additional fire protection in the upper deck engine compartment. The helicopter is also fitted with a NACA engine inlet, to provide additional engine air during forward flight at speeds of greater than 40kt (75km/h).

The 902 has a new fuel system which has been modified from that of the MD900 to feed off an auxiliary tank under the baggage bay floor, providing an extra 106 litres. The effectiveness of the No Tail Rotor (NOTAR) system is also improved, with better tip sealing. Internal changes include the provision of a new gyro which was originally part of optional avionics for the standard Explorer.

The enhancements translate into a 22°C engine temperature limit margin in one engine inoperative (OEI) conditions, which rises to 885°C from 863°C. OEI limits for 2.5min operation rise from 902°C to 930°C, while the engine rating under the same conditions rises from 485kW (650shp) to 505kW. Range increases from 520km (280nm) to almost 560km, while speed is boosted by 3kt to 135kt.

Boeing, which is selling its civil helicopter business, also plans further 900/902 improvements to reduce direct operating costs. These include tests to verify extended life cycles for the main rotor pitch case, flex beam and hub and NOTAR fan hub. These are expected eventually to increase inspection limits up to 10,000 cycles, more than double the current limits. Other improvements to the original MD900 are expected to yield a 115kg payload increase, taking gross weight to 2,840kg.

Boeing has begun a two phase programme to increase the landing and take-off weights of the MD600N in hot and high conditions. The first phase is aimed at increasing take-off weight to 1,750kg at 7,000ft (2,150m). It will primarily address the needs of tour operators, such as Grand Canyon-based AirStar, which has seen payload capability reduced as a result of installing an air conditioning system. The second phase will increase the weight beyond 1,750kg towards an eventual target of 1,865kg.

Source: Flight International