Glyn
The issue with both the Express and Rapide was that time and technology was overtaking them, and DH's love affair with wood and the biplane.
Yes the Mossie and the Vampire showed his genius, but even he couldn't hold back the tide.
The DH86 had some structural design problems with the tail on top of that, but the DH89 was probably the final and best evolution of the Biplane twin airliner, really no argument with that. (leaving the Dragonfly as primarily a private twin rather than airliner).
However even in 1934 there were wooden monoplane designs that were emerging to compete with the Rapide on the same power or less, but the airliner issue quickly became larger aircraft, with larger engines and more seats, ie the Boeing 247D with 10 seats, the DC-2 with 14 seats and the DC-3 with initially 21, and later 28 seats, so the future clearly belonged to the metal stressed skin monoplane, even if it needed larger engines.
While the Rapide was as efficient as it could be on 2x 200hp engines, it only carried 8 passengers, and for an airline "efficiency" meant more seats, not smaller engines as this was still the age of cheap oil.
LJ Wackett in Australia designed and built two high wing monoplanes from 1934 onwards, the LJW6 Codock with 160hp Napiers and the LJW7 Gannet with 200hp Gipsy six's, admittedly with 2 less passengers.
In 1933 the Shorts Scion was also available, using only 2x 90hp Pobjoy's although its seating capacity of 5 more competed with the Dragon than the Rapide.
In January 1935 the civilian Avro 652, the forerunner of the Anson flew with a capacity of just 4 passengers, on 2x 270HP engines, but at a speed of 188MPH and 1271 NM, both significantly exceeding the DH89 where this aircrafts objective was not more seats but high speed mail runs and long international legs, the military Anson of the same year used much larger 350HP engines but primarily to increase weight carrying ability for bomb load.
The Rapide held its own for a while, and had a reprise with the Dominie during WW2 but it was quickly being passed by the rise of the monoplane and dawn of the metal stressed skin airliner even while it was being first built, and the race became for more seats at greater overall efficiency.
DH89 (8 seats) - 1934, Boeing 247D (10 seats) -1933, Douglas DC-2 (14 seats) -1934, Douglas DC-3 (21 seats)- 1935.
A measure of what Airlines considered "successful" is the fact that each of the US aircraft above were made obsolete a year later by the next development that increased passenger capacity by 50%.
Of course the Avro 652 quickly fell by the wayside as an airliner, and similarly the Anson as a bomber, (but it held on as a trainer), also quickly superceded by metal designs.
While war accelerated aircraft development, it halted airliner development for at least 5 years, the Dove and Drover may have arrived much faster since they didnt rely much on wartime developed technology, and James has already mentioned the Lockheed 10/12 pre-war series, to be joined by the Beech 18 later, all competing in the 8-10 seat range but with much faster speed due to monoplane stressed skin design, larger engines and retractable undercarriage.
I would have expected DH and Qantas to enter the latest and largest UK airliner into the 1934 air-race, they had to be delivered to Australia in anycase, 4x 200hp engines, and 10-12 passengers, but of course DH knew the only way a UK aircraft could win against the new US designs was through design of a purpose built racer.
DH through his Comet won the speed race, but the true winner was Douglas in terms of long term impact.
It was a bit much to expect the DH89 to place significantly, but its race performance was lacklustre in anycase more due to technical problems. I do think the DH89 is an important type regardless, as the last and perhaps most successful Wooden Biplane twin engined airliner.
Data from "A14 Wackett Gannet"
General characteristics
Crew: 1 pilot
Capacity: 6 passengers
Length: 10.51 m (34 ft 6 in)
Wingspan: 15.85 m (52 ft 0 in)
Height: 3.50 m (11 ft 6 in)
Empty weight: 1,470 kg (3,234 lb)
Gross weight: 2,449 kg (5,388 lb)
Powerplant: 2 × de Havilland Gipsy Six, 150 kW (200 hp) each
Performance
Maximum speed: 240 km/h (150 mph)
Range: 885 km (553 miles)
Service ceiling: 17,000 m (5,200 ft)
Rate of climb: 4.3 m/s (850 ft/min)
Specifications (Scion II landplane)
Data from British Civil Aircraft 1919-1972: Volume III [6]
General characteristics
Crew: 1
Capacity: 5 passengers
Length: 31 ft 6 in (9.60 m)
Wingspan: 42 ft 0 in (12.80 m)
Height: 10 ft 4½ in (3.16 m)
Wing area: 255 ft² (23.7 m²)
Empty weight: 1,770 lb (804 kg)
Loaded weight: 3,200 lb (1,455 kg)
Powerplant: 2× Pobjoy Niagara III radial engine, 90 hp (67 kW) each
Performance
Maximum speed: 128 mph (111 knots, 206 km/h)
Cruise speed: 116 mph (101 knots, 187 km/h)
Range: 390 mi (339 NM, 624 km)
Service ceiling: 13,000 ft (3,960 m)
Rate of climb: 625 ft/min (3.2 ft/min)
Wing loading: 12.5 lb/ft² (61.4 kg/m²)
Power/mass: 0.056 hp/lb (0.092 kW/kg)
DH-89 Rapide
Crew: 1
Capacity: 8 passengers
Length: 34 ft 6 in (10.5 m)
Wingspan: 48 ft 0 in (14.6 m)
Height: 10 ft 3 in (3.1 m)
Wing area: 340 ft² (32 m²)
Empty weight: 3,230 lb (1,460 kg)
Loaded weight: 5,500 lb (2,490 kg)
Powerplant: 2× de Havilland Gipsy Six inline engine, 200 hp (149 kW) each
Performance
Maximum speed: 157 mph (136 kn, 253 km/h) at 1,000 ft (305 m)
Range: 573 mi (498 nmi, 920 km)
Service ceiling: 16,700 ft (5,090 m)
Rate of climb: 867 ft/min (4.3 m/s)
Wing loading: 16 lb/ft² (79 kg/m²)
Power/mass: 0.036 hp/lb (60 W/kg
Avro 652
General characteristics
Crew: 2
Capacity: 4 passengers
Length: 42 ft 3 in (12.88 m)
Wingspan: 56 ft 5 in (17.2 m)
Height: 13 ft 1 in (3.99 m)
Wing area: 410 ft² (38.1 m²)
Empty weight: 5,375 lb (2,437 kg)
Max takeoff weight: 7,400 lb (3,358 kg)
Powerplant: 2× Armstrong Siddeley Cheetah V radial engine, 270 hp (201 kW) each
Performance
Maximum speed: 163 kn (188 mph, 302 km/h)
Cruise speed: 143 kn (165 mph, 265 km/h)
Stall speed: < 60 mph ()
Range: 687 nmi (790 mi, 1,271 km)
Service ceiling: 19,000 ft (5,791 m)
Rate of climb: 770 ft/min [4] (3.9 m/s)
Avro Anson
General characteristics
Crew: 3-4
Length: 42 ft 3 in (12.88 m)
Wingspan: 56 ft 6 in (17.22 m)
Height: 13 ft 1 in (3.99 m)
Wing area: 463 ft² (43.1 m²)
Empty weight: 5,512 lb (2,500 kg)
Loaded weight: 7,955 lb (3,608 kg)
Max takeoff weight: 8,500 lb (3,900 kg)
Powerplant: 2× Armstrong Siddeley Cheetah IX radial engines, 350 hp (260 kW) each
Performance
Maximum speed: 188 mph (163 kn, 303 km/h) at 7,000 ft (2,100 m)
Range: 790 mi (690 nmi, 1,300 km)
Service ceiling: 19,000 ft (5,791 m)
Rate of climb: 750 ft/min (3.8 m/s)
Wing loading: 17.2 lb/ft² (83.9 kg/m²)
Power/mass: 0.088 hp/lb (140 W/kg)
regards
Mark Pilkington
_________________ 20th Century - The Age of Manned Flight
"from Wrights to Armstrong in 66 years -WOW!"
|