Long before the era of jumbo jets such as the Boeing 747 and Airbus A380, the skies were graced by massive passenger planes known as “flying boats” or enormous seaplanes from the 1950s. Among the most famous of these was the Spruce Goose, also known as the Hughes H-4 Hercules. However, another well-known and iconic flying boat was the Saunders-Roe Princess, which will be the focus of our discussion here.
The Saunders-Roe Princess was a British flying boat that represented a remarkable vision for the future of air travel during its time. A massive aircraft with an elegant design, the Princess was a unique creation that promised luxury, comfort, and style. Despite its ambitious concept, the aircraft ultimately never entered commercial service due to various reasons.
Specifications and Features
The Saunders-Roe Princess was a large flying boat designed and built by the British company Saunders-Roe in the early 1950s. Its specifications were impressive, with a wingspan of 219 feet (66.7 meters), a length of 148 feet (45.1 meters), and a height of 54 feet (16.5 meters).
The aircraft was powered by ten Bristol Proteus turboprop engines, providing it with a range of around 5,721 miles (9,210 kilometers) and a cruising speed of approximately 360 mph (580 km/h). The inner four of the six sets of four-bladed propellers were double, contra-rotating, and powered by the innovative twin version of the Proteus, known as the Bristol Coupled Proteus. Each of these engines drove one of the contra-rotating propellers. The two outer propellers, on the other hand, were single and each powered by an individual engine. This incredible combination of design and engineering prowess made the Princess a true marvel of its time.
The sleek design of the Saunders-Roe Princess hull featured a subtle step in the keel, intended to minimize air drag and optimize its performance.
The Princess was designed to carry up to 105 passengers and featured luxurious accommodations, including spacious cabins, comfortable seating, and large windows to offer passengers stunning views. The aircraft’s three decks included private staterooms, a dining room, and lounge areas – all designed to provide a premium travel experience.
Design Highlights
- A Spacious and Comfortable Interior: The rounded, bulbous design of the Princess’s fuselage contained two full passenger decks, providing ample room for up to 105 passengers to travel in unparalleled comfort. The hull’s planing bottom featured a minimal step in the keel to reduce drag while in flight.
- Innovative Engine Configuration: Powering the Princess was an arrangement of ten Bristol Proteus turboprop engines, driving six sets of four-bladed propellers. The inner four propellers were double, contra-rotating propellers powered by a twin version of the Proteus called the Bristol Coupled Proteus. Each engine drove one of the propellers, while the two outer propellers were single and powered by a single engine each.
- Cockpit and Flight Crew: The cockpit of the Princess was designed for a crew comprising a pair of pilots, two flight engineers, a navigator, and a radio operator. The aircraft was initially intended to feature powered flight controls, including an early fly-by-wire implementation, to help pilots effectively actuate its large control surfaces. However, a traditional mechanical linkage approach, augmented by electrically driven power assist units, was ultimately chosen for more effective actuation.
- Advanced Control Systems: The ailerons and rudder were divided into multiple sections, allowing for any faulty part of the servo-powered control system to be “trailed” without affecting the remaining working sections. Although the prototype aircraft was fitted with advanced hydraulic controls, Saunders-Roe intended for production models to use an analog system featuring electrical servos with hydraulic final control actuators. This system was built and underwent ground testing, but the Princess project was terminated before any aircraft could be fitted with it.
Specifications
| Specification | Value |
|---|---|
| Crew | 2 pilots, 2 flight engineers, radio operator, and navigator |
| Capacity | 105 passengers / 137,000 lb (62,142.2 kg) disposable load |
| Length | 148 ft (45 m) |
| Wingspan | 219 ft 6 in (66.90 m) with wingtip floats retracted; 209 ft 6 in (63.86 m) floats extended |
| Height | 55 ft 9 in (16.99 m) |
| Wing area | 5,019 sq ft (466.3 m2) |
| Airfoil | “Saro-modified Goldstein section” to “modified N.A.C.A. 4415 Series” at tip |
| Empty weight | 190,000 lb (86,183 kg) |
| Gross weight | 330,000 lb (149,685 kg) |
| Max takeoff weight | 345,025 lb (156,501 kg) |
| Fuel capacity | 14,000 imp gal (63,645.3 l; 16,813.3 US gal) in four integral inner wing tanks |
| Powerplant (coupled) | 4 × Bristol Coupled-Proteus 610 turboprop, 5,000 hp (3,700 kW) each + 1,660 lbf (7.38 kN) residual thrust |
| Powerplant (single) | 2 × Bristol Proteus 620 Turboprop engines, 2,500 hp (1,900 kW) each + 820 lbf (3.65 kN) residual thrust |
| Propellers | 4-bladed de Havilland constant speed, quick-feathering Duralumin propellers, 16 ft 6 in (5.03 m) diameter |
| Maximum speed | 380 mph (610 km/h, 330 kn) at 37,000 ft (11,000 m) |
| Cruise speed | 360 mph (580 km/h, 310 kn) at 32,500 ft (9,900 m) |
| Stall speed | 113 mph (181 km/h, 98 kn) flaps and floats down |
| Range | 5,720 mi (9,210 km, 4,970 nmi) |
| Endurance | 15 hours |
| Service ceiling | 39,000 ft (12,000 m) absolute |
| Rate of climb | 1,900 ft/min (9.7 m/s) at 184 mph (296 km/h; 160 kn) at sea level |
History and End of Era
Before WWII, British airline Imperial Airways utilized large long-range passenger flying boats like the Short Empire and Short S.26 to establish long-distance routes, offering unprecedented comfort for passengers. However, wartime disruptions led to the merger of Imperial Airways with British Airways Ltd, forming British Overseas Airways Corporation (BOAC) in 1940, and many flying boats were repurposed for military use.
Flying boats had advantages over land-based aircraft, as they were not limited by runway length and could land and take-off from any available body of water. After the war, flying boat services resumed with models like the Short Hythe, Short Sandringham, and Short Solent. But the war had also left a legacy of large runways and airports, which could now accommodate bigger land aircraft.
The British Air Ministry was eager to revive flying boat routes and approached Saunders-Roe (Saro) and Shorts for a collaborative aircraft project called the Short Shetland. Although the project was deemed a failure, Saunders-Roe saw it as a learning experience and continued to develop a more revolutionary flying boat. In 1945, Saro submitted a bid for a new long-range civil flying boat, the SR.45, which was later selected as the winner.
Despite high costs and schedule overruns, Saro proceeded with the SR.45 project. The first prototype flew in 1952, and further testing revealed engine reliability issues. In 1951, BOAC declared no need for new large flying boats, and the British government struggled to decide the program’s fate. Ultimately, the three existing Princesses were placed into storage, and although several purchase offers emerged, the aircraft were found to be badly corroded by 1964. All three Princesses were broken up by 1967, marking the end of Saunders-Roe’s involvement in fixed-wing commercial aircraft production.
The Saunders-Roe Princess was a remarkable and ambitious attempt to revitalize the golden age of flying boats. Its impressive design and engineering aimed to offer passengers unparalleled luxury and comfort, while tapping into the unique advantages that flying boats possessed. Despite facing various setbacks and challenges throughout its development, the Princess serves as a poignant reminder of a bygone era of air travel. Though its legacy ultimately ended with the termination of its production, the Princess remains an iconic symbol of British aviation history and a testament to the ingenuity and aspirations of its creators.
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