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Helio H-550

Helio AU-24 Stallion



The Stallion is specifically designed for operation from unprepared fields and is equipped with a full complement of STOL devices. Design of the Stallion began in 1963, and the first models were produced in 1966.
The Stallion is powered by a single 680-ehp turboprop engine driving a three blade reversible-pitch prop and fed by wing tanks with a capacity of 120 gallons.
Its all-metal cantilevered wings are equipped with high lift slotted all-metal flaps, fabric-covered balanced ailerons, and full-span automatic leading-edge slats. The tail unit features a one-piece horizontal surface with combined trim and antibalance tab. The cabin is protected by a crash-resistant tubular frame. The Stallion’s accommodations provide for a pilot and copilot up front with either eight passengers on bench seats or six passengers seated individually. Access is made through a door on the port side near the pilot, an optional starboard door, and a double cargo door on the port side. The double door is in two sections—the forward half hinges and the rear half slides. The rear half can be opened during flight for cargo drops or parachutists.

The Credible Chase programme, an off-shoot of Pave Coin, in which a number of aircraft were evaluated by the USAAF at Eglin AFB in order to come up with a new light-strike attack aircraft for the South Vietnamese Air Force, resulted in a 15-each order for the Helio Stallion and Fairchild Peacemaker. These aircraft, carrying the designations AU-24 and AU-23 respectively, are militarised versions of their commercial counterparts, but have increased gross weights, underwing and fuselage hardpoints and Gatling guns firing from the cabin doors.
In the case of the Helio AU-24 the prototype was modified and tested by Kaman Aerospace under contract from Helio, although Helio supplied the test pilot. Kaman has stressed the aircraft to a new gross weight of 6,300lb, 2,860kg as well as adding two hardpoints under each wing and one fuselage centreline point. The AU-24 can carry 300lb, 135kg on the outboard pylons and 600lb, 270kg in-board, plus 500lb, 225kg on the fuselage centreline. Ordnance can include single bombs, cluster bombs, FFAR launchers and machine-gun pods. The AU-24 is powered by a UAC PT6A-27 of 680 shp, 508kW. The AU-24 has a speed range of from 42 mph, 68km/hr to over 200 mph, 320km/hr.
The Stallion is basically the same aircraft as the Courier - the wing planform is identical but span is increased from 39ft / 11.9m to 41ft / 12.5m.

H-550A Stallion
Engine: P&WAC PT6A-27, 680 hp.
Seats: 10.
Wing loading: 21.1 lb/sq.ft.
Pwr loading: 7.5 lb/hp.
Gross wt: 5100 lb.
Empty wt: 2860 lb.
Equipped useful load: 2090 lb.
Payload max fuel: 1280 lb.
Range max fuel/cruise: 360 nm/1.9 hr.
Range max fuel / range: 483 nm/ 3.5 hr.
Service ceiling: 25,000 ft.
Max cruise: 179 kt.
Max range cruise: 140 kt.
Stall: 36-41 kt.
1.3 Vso: 47 kt.
ROC: 2200 fpm.
Min field length: 750 ft.
Takeoff distance (50') 660 ft
Landing distance (50') 750 ft
Fuel cap: 810 lb.
Ceiling 25,000 ft


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