Guy Norris/LOS ANGELES
Ajoint McDONNELL Douglas (MDC)/AlliedSignal effort to develop an instrument flight-rules (IFR) package for the MD900 Explorer has been delayed because of "greater-than-expected complexity".
The IFR package, announced at Heli-Expo in February, was due to be certificated by the end of April. MDC says, however, that "...it's a big and complicated project and we were optimistic in our original projection". Certification of a stability augmentation system (SAS), one of the key parts of the effort, is tentatively due later this month as an interim step to full IFR clearance with the entire avionics package. This has been set back to "probably the October timeframe", says MDC. It cautions, however,"...that there are still possibilities for more unforeseen things to cause delay".
Certification of the SAS as an interim "...will allow IFR customers early use of the aircraft", explains AlliedSignal manager of helicopter planning and programmes, Gerald Hiller. The SAS is a required item for IFR operation because it provides short-term workload relief for pilots flying in turbulence by electronically sensing gusts and then countering with control inputs. With SAS, the pilot still keeps hands on the cyclic control and feet on the rudder pedals.
The full IFR package, however, will include a digital auto-pilot and flight director. "Developing the flight-control system has taken us a lot longer than we'd expected. The amount of activity necessary has exceeded the expectations of both companies," says Hiller. "We thought we'd be attaching systems [to the basic Explorer architecture], but as we approached the certifying authorities, they've asked us to do more and this has led to changes in the detailed design."
The KFC900 digital auto-pilot and flight director of, which the SAS forms part, will provide longer-term attitude retention and directional control of the aircraft. With the full system, the Explorer will be certifiable for single-pilot IFR operations in the USA, although the package contains options for dual-pilot IFR operations as favoured outside the USA.
The single-pilot configuration has instruments in an "L" shape panel on the pilot's side only. Dual pilot configurations have a "T" panel with instruments on both sides, and a further option gives a choice of either electronic or electromechanical instruments on the co-pilot's side.
Other elements of the full-up IFR suite include the EFS 40 electronic flight-instrument display system and KLN 90B global-positioning system. Options include an RDR 2000 weather radar and Flexcom 2 frequency-hopping radio system suitable for medical- service and police use.
AlliedSignal now hopes to obtain the US Federal Aviation Administration supplemental type certificate for the package this year. MDC will offer it on new-build helicopters as an upgrade.
The first production MD 600N helicopter fuselage has arrived at MDC's Mesa site in Arizona, from Ayers in Albany, Georgia. The MD 600N, a stretched version of the MD 520N, is due to enter full-scale production this year.
Source: Flight International
