7/21/2023 0 Comments Comanche helicopterAlso, it included a heads-up, eyes-out helmet-mounted display, and the ability to work in adverse weather conditions and with battlefield obscurants. The target acquisition system had the same advanced features as the pilotage system, with a second generation FLIR and a 40% increase in standoff and detection range. This resulted in 50% fewer gears, 40% fewer bearings, and 12% less weight. Here each of the two engines had a split path to the final reduction stage, resulting in four gears meshing with the final ring gear to transmit the high rotor torque without the use of a complex planetary gear stage. With LHX a simpler system was used using the concept of “split torque”. Years ago this problem was solved by using a planetary final stage, typically with five planet gears, to transmit the high torque to the rotor through five separate gears. A final reduction stage of a simple spur or bevel gear is impossible since the tooth loads on that single gear mesh are excessive. Since the rotor turns a relatively low speed (200 to 400 rpm) the torque in the final stage is very high. Transmission designers of even moderate sized helicopters face a difficult challenge designing the final reduction stage of the drive system. The transmission system also made use of major technology advances since the previous generation of helicopters. Use of a triplex (triple redundant) electronic architecture with wires in lieu of mechanical linkages provided greater flexibility in routing the wiring and reduced the probability of ballistic damage from threat weapons. Functions that were to be added in later stages of the program included envelope cueing and integrated fire and flight control. The system incorporated a number of automated features including a flight director and a fully coupled auto-pilot with advanced functions, including auto hover, pop-up, and return to mask. The Comanche FCS provided two highly augmented modes: rate command/attitude hold, which provided very responsive maneuver capability for day visual conditions, and attitude command/velocity hold, with more benign response for night and degraded visual conditions. Additionally, the digital fly-by-wire system promised to be more reliable and weighed significantly less than a redundant mechanical system. Several of the features greatly improved handling qualities and reduced pilot workload. The Comanche digital fly-by-wire flight control system (FCS) was the most advanced rotorcraft flight control system that had been developed at that time. Doors and access panels could then be placed in the most optimum positions, improving both radar signature and ease of maintenance for the internal components. An alternate approach was created to have a simple structural box beam internal structure with the outside skin unloaded from the primary structural loads. heavy and flexible) and difficult to design. It became apparent that a conventional fuselage would be very structural inefficient (i.e. Additionally, the Army’s emphasis on supportability required many access panels to simplify maintenance tasks. LHX also required a retractable landing gear for both low radar signature and for high speed. Because of the need for a low radar signature, the aircraft weapons had to be stored within the fuselage and then extended out when they were to be deployed. Unlike virtually all other helicopters (and fixed wing aircraft for that matter) it was decided not to use the exterior surfaces of the aircraft for the primary fuselage structure. After many conceptual design studies, the Boeing Sikorsky team chose an unusual design for the fuselage.
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