The Pobjoy Niagara is a British seven-cylinder, air-cooled, radial, aero-engine first produced in 1934. The design ran at higher speeds than conventional engines, and used reduction gearing to lower the speed of the propeller. This led to a noticeable off-centre mounting for the propeller. The Niagara was a popular engine for light and experimental aircraft, well regarded due to their small diameter, smooth operation, low noise and innovative engineering.
Variants: Niagara I Bore/stroke 77 x 87 mm (3.03 x 3.43 in) Swept volume 2,835 cc (173 cu in) Compression 6.25:1 Gearing 0.47:1 Normal continuous power 84 hp (63 kW) at 3,200 rpm at sea level.
Niagara II Bore/stroke 77 x 87 mm (3.03×3.43 in) Swept volume 2,835 cc (173 cu in) Compression 6.0:1 Gearing 0.39:1 Normal continuous power 84 hp (63 kW) at 3,200 rpm at sea level.
Niagara III Bore/stroke 77 x 87 mm (3.03×3.43 in) Swept volume 2,835 cc (173 cu in) Gearing 0.47:1 Normal continuous power 88 hp (66 kW) at 3,300 rpm at sea level.
Niagara IV Similar to Niagara III but with a higher operating rpm. Normal continuous power 98 hp (73 kW) at 3,500 rpm at sea level.
Niagara V Larger version of the basic Niagara. Bore/stroke 81 x 87 mm (3.19 x 3.43 in) Swept volume 3,138 cc (192.5 cu in). Compression 8.0:1 Gearing 0.47:1 Normal continuous power 125 hp (93 kW) at 4,000 rpm at sea level.
Cataract I-III De-rated, uncowled versions of Niagara I-III with simple inter-cylinder baffles for cooling and trickle-down lubrication for lower exhaust rockers. Compression 5.7:1 Gearing 0.47:1
Cascade Direct drive version of Cataract I. Normal continuous power 66 hp (49 kW) at 2,100 rpm.
Applications: Niagara – Aeroput MMS-3 Airspeed Fleet Shadower CLW Curlew Comper Kite Comper Swift General Aircraft Monospar ST-25 General Aircraft Fleet Shadower Lambach HL.I Pobjoy Pirate Saro Shrimp Shapley Kittiwake Short Scion Senior Short Scion Short Stirling (half scale prototype) Spartan Clipper
Cataract – British Klemm Swallow Hafner A.R.III Gyroplane Hendy Hobo
Cascade – Autogiro AC-35
Specifications: Pobjoy Niagara IV Type: 7-cylinder, air-cooled, radial engine Bore: 3.03 in (77 mm) Stroke: 3.43 in (87 mm) Displacement: 173 cu in (2.8 lt) Diameter: 26.5 in (673 mm) Dry weight: 130 lb (59 kg) Valvetrain: 1 inlet and 1 exhaust valve per cylinder Fuel system: 1 Claudel-Hobson carburettor Fuel type: 70 octane Cooling system: Air-cooled Power output: 98 hp at 3,625 rpm max at sea level Compression ratio: 6:1 Power-to-weight ratio: 0.75 hp/lb
The Pobjoy R was a British seven-cylinder, air-cooled, aircraft engine designed and built by Pobjoy Airmotors. Introduced in 1926 it was a popular engine for ultralight and small aircraft in the 1930s. A notable feature of the Pobjoy R was the propeller reduction gear which allowed the engine to operate at high RPM.
Applications: British Aircraft Swallow Comper Swift Cosmopolitan Light Plane Couzinet 101 General Aircraft Monospar Hendy Hobo Kay Gyroplane Lippisch Delta IV Mauboussin M.121P Corsaire Major Miles Satyr Pander Multipro Pobjoy Special Short Scion Short Scion Senior Spartan Clipper
Pobjoy R Type: 7-cylinder air-cooled, radial, left-hand tractor Bore: 3.03 in (77 mm) Stroke: 3.43 in (87 mm) Displacement: 173.05 cu in (2.84 L) Diameter: 25.5 in (647.7 mm) Dry weight: 135 lb Oil system: Dry sump Cooling system: Air-cooled Power output: 85 hp Specific power: 0.5 hp/cu in Fuel consumption: 4.9 imp. gallons per hour Power-to-weight ratio: 0.63 hp/lb
Until 1935 Pobjoy Airmotors Ltd had not previously built an aircraft, but concentrated successfully on engines. In June 1935 the company name was changed to Pobjoy Airmotors and Aircraft Ltd and at the same moment they introduced their only original aircraft design, the Pobjoy Pirate, aimed at the Leopard Moth market. They chose to power it with one of their own seven cylinder radial engines. At the time, the most powerful variant was the 90 hp (67 kW) Niagara III, much less powerful than the 145 hp (108 kW) Gipsy Major 10 of the Leopard Moth. The Pobjoy, though was less than half the weight of the de Havilland engine and Pobjoy believed that with the advantage of this weight saving (about 160 lb or 73 kg) they could build a lighter and smaller aircraft that would perform as well.
The designer of the Pirate was the experienced Harold Boultbee, who had recently produced the Civilian Coupé, and construction began early in 1935. The high wings were straight edged, but tapered, slightly swept on the leading edge and fully slotted. The trailing edge carried differential ailerons and interacting flaps. A pair of V shaped lift struts ran from the two wing spars down to the lower fuselage side where there was a universal joint to facilitate wing folding. The folding mechanism was unusual: unlocked, the wings slid forward and tipped leading edge down, so that when the front spar was released from its fitting the wings could fold rearwards and downwards about the rear spar. Because of the initial forward movement, the folded length was less than it would have been with conventional geometries.
The fuselage was of wooden construction, plywood covered and tapering strongly in elevation to the tail. The fin was triangular and carried a semicircular rudder moving above the tailplane and elevators. The main undercarriage oleo legs were attached close to the fuselage end of the lift struts. A glazed cabin placed the pilot ahead of the two side-by-side seated passengers. Ahead of them, the Niagara, under a characteristically neat Pobjoy cowling with “helmet” exhaust ports drove a two-bladed propeller.
In mid-1935 Pobjoy were collaborating with Shorts over the Pobjoy powered Short Scion, so Short’s test pilot, John Lankester Parker was available to try the Pirate. It first flew on 25 June and by 10 July had been in the air for a total of 70 minutes. Parker reported that the machine was underpowered and uncompetitive and it was never flown again. It was registered as G-ADEY but never carried these letters; it was broken up the following summer.
The Pirate was lighter and smaller than the Leopard Moth: the span was 3 ft 6 in (1.07 m) or 10% smaller and the all up weight 624 lb (283 kg, 28%) lighter, but this did not make up for the 38% decease in power.
Engine: 1 × Pobjoy Niagara III, 90 hp (67 kW) Wingspan: 34 ft 0 in (10.36 m) Wing area: 180 sq ft (17 sq.m) estimate Gross weight: 1,600 lb (726 kg) Maximum speed: 125 mph (201 km/h; 109 kn)
UK Founded 1930 as Pobjoy Airmotors Ltd., engine manufacturer. In 1935 became public company and enlarged scope to include aircraft manufacture. Chairman Oswald Short, managing director Arthur Gouge. Built Pirate high-wing monoplane 1935, but performance disappointing. Acquired license to build Short Scion and Scion Senior light transports. Short Bros took over all Pobjoy’s issued shares in 1938. Company was subcontractor for aircraft parts in Second World War.
Little Audrey, built by Paul Poberezny, was derived from Benny Howard’s Pete racer, after rebuild as the Baker Pete / Special.
It was bought by EAA in 1953, and redesigned as Pober Little Audrey with a replica fuselage and Luscombe shoulder-wings. The original fuselage and tail, plus some miscellaneous parts, went into a rebuild of the 1930 configuration by Repeat Aircraft, Riverside CA.
Engine: Continental, 75 hp Wing span: 18 ft Weight: 800 lb Top speed: 140 mph
The single-seat Pober Pixie is another homebuilt designed by Paul Poberezny. It originally started as an effort to help pilots beat high operational costs and was designated Project Econoplane in 1974. Inspired by a Heath Parasol LN, the Pixie is a parasol monoplane powered by a Limbach VW engine rated at 50 to 75 hp. Full-span ailerons give excellent roll with little yaw on entry and recovery. This is a beginner’s project for construction, with highly detailed plans, and the cost level is low. Can be powered with a VW conversion or Continental A-65.
The Poage Eindekker was built by Jack Poage, of Churchville MD. USA, circa 1971. Registered N101SC, it was a single-place cabin, mid-wing monoplane, aerobatic aircraft.