FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1983
1983 - 0404.PDF
MILITARY HELICOPTERS calls the "S-38". Control response and feel remain virtually identical to that of the fully operational system, and no electrical services are lost. All systems are brought on line again, and Ed establishes a 15°-20° nose-down attitude and dives to 155kt. Ed then pulls 20° nose-up. When settled in the climb, he pushes cyclic forward rapidly to bunt the aircraft. As we go over the top, at an esti mated 0-5g, he applies left and right cyclic in turn, rolling the S-76 through a 60° arc to demonstrate that lateral control response is unaffected by less than lg conditions. I then take over, climb the aircraft to 2,500ft, and enter autorotation.The speed is reduced to 80kt to establish a rate of descent of some l,600ft/min at our weight of about 8,4001b. The aircraft is very manoeuvrable, although rotor r.p.m. requires careful monitoring during tight turns. Overshooting from 500ft, I feel quite confident that it would not be diffi cult to execute a successful engine-off landing in a small area. Five minutes at high speed brings us to Odiham's low-flying area, where I descend to 100ft. At 120kt, even in the moderate turbulence at low level, the ride is comfortable. Aircraft handling is crisp and precise. We then climb to 500ft and join the Odiham circuit. The aircraft is set up at 500ft and 70kt for a running landing on Runway 28. Ed warns me of the tendency of pilots new to the aircraft to overestimate the S-76's inherent drag and to overshoot the desired touchdown spot. The aircraft is clean and only decelerates slowly if left to its own devices. Running on at 40kt, it is easy to achieve a smooth touchdown, but the wheel brakes are not too effective. The ideal run-on speed is 35kt with a maximum of 45kt. We lift off and move clear of the runway to investigate handling in the hover. The S-76 is stable in the hover, even with both SASs disengaged. Control response in spot turns, sideways, and backward flight remain excellent, although yaw control is a little twitchy when hovering in a cross- wind from the right. Fixed undercarriage was planned, but Sikorsky has stayed with retracting gear The S-76 can achieve 35kt in sideways flight to the right, but to the left runs out of yaw control at around 15kt until trans- lational lift values are high enough to ease off, when 42kt is achievable. Rearwards, about 30kt can be maintained. Care must be taken in nose-high hovers as the helicopter has no tailskid. Sikorsky may fit one to later military S-76s, allow ing high-speed run-ons to be made with confidence. At present a tail-boom strike is possible, but the tail rotor is clear of the ground. About 45min after take-off we return to Farnborough for an out-of-wind approach to Runway 18. Shutdown is simple, although the rotor brake is rather coarse. The brake is switch-operated and is either fully on or fully off. With no fine control available, this stops the rotor quite effec tively, but is harsh in operation, causing a considerable jolt. My overall impression of the S-76 is a helicopter that is super fun and uncom plicated to fly. The controls are light and responsive throughout the flight envelope and the aircraft is stable. Perhaps a more sophisticated autopilot is desirable rather than the simple but limited SAS. The Mk II Plus has the same basic airframe, engines, and dynamics as the present civil S-76. An option is available with Pratt & Whitney PT6B-36s, confer- S-76 military prototypes have completed an extensive armament firing test programme ring 40 per cent more power over the exist ing installation, says Sikorsky. This option would be favoured by hot-and-high operators. Both the Mk II and Mk II Plus have sliding doors, 2001b/ft2 cargo floor, and high-strength, self-sealing fuel tanks. The flightcrew has armoured seats, and up to 12 troop seats can be fitted. Without the weapons fit, the S-76 Mk II utility has an empty weight of 6,0601b, with the Mk II Plus tipping the scales at 6,5101b, compared with the 5,6001b of the commer cial S-76. With 1,7401b of fuel and eight Hughes Tow anti-tank missiles, the gross take-off weight of the S-76 Mk II Plus is 9,4701b. Forward-firing armament is carried on a bolt-on, through-cabin beam which can be fitted by two men in 15min. Weapon options include podded 7 • 62mm machine guns, 7-62mm miniguns, or 0-5in machine guns. For soft-skinned targets and light armour, 20mm cannon pods and two 19-round canisters of 2-75in folding- fin unguided rockets can be used. Up to eight Tows are another option, and the sight can be mast- or roof-mounted according to customer preference. For self-defence against enemy helicop ter gunships, an air-launched version of the General Dynamics Stinger shoulder- launched SAM is under consideration. Sighting of all forward-firing weapons except Tow is via a projected-reticle ClA- 513 sight mounted on the righthand glareshield. The S-76 provides a stable weapons platform. For landing-zone fire suppression, 7-62mm miniguns, 7-62mm machine guns, or 0-5in machine guns can be door-mounted for use by the crewman. Flight's overall impression of the S-76 is of a fast, nimble helicopter which is fun to fly. There are, however, slight misgivings on the tactical side with the helicopter in its present form. The landing gear on the example flown does not provide sufficient ground clearance and the wheels are too small. Sikorsky has now decided on an increased-clearance retracting gear, but a tailskid would still be a useful addition for added crew confidence in high-flare, run- on assault landings. 606 FLIGHT International, 5 March 1983
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
