Short Stirling

https://en.wikipedia.org/wiki/Short_Stirling

The Short Stirling was a British four-engined heavy bomber of the Second World
War. It has the distinction of being the first four-engined bomber to be
introduced into service with the Royal Air Force (RAF).

The Stirling was designed during the late 1930s by Short Brothers to conform
with the requirements laid out in Air Ministry Specification B.12/36. Prior to
this, the RAF had been primarily interested in developing increasingly capable
twin-engined bombers but had been persuaded to investigate a prospective
four-engined bomber as a result of promising foreign developments in the field.
Out of the submissions made to the specification, Supermarine proposed the Type
317 which was viewed as the favourite, while Short's submission, named the S.29,
was selected as an alternative. When the preferred Type 317 had to be abandoned,
the S.29, which later received the name Stirling, proceeded to production.

During early 1941, the Stirling entered squadron service. During its use as a
bomber, pilots praised the type for its ability to out-turn enemy night fighters
and its favourable handling characteristics, while the altitude ceiling was
often a subject of criticism. The Stirling had a relatively brief operational
career as a bomber before being relegated to second line duties from late 1943.
This was due to the increasing availability of the more capable Handley Page
Halifax and Avro Lancaster, which took over the strategic bombing of Germany.
Decisions by the Air Ministry on certain performance requirements, such as to
restrict the wingspan of the aircraft to 100 feet, had played a role in limiting
the Stirling's performance; these restrictive demands had not been placed upon
the Halifax and Lancaster bombers.

During its later service, the Stirling was used for mining German ports; new and
converted aircraft also flew as glider tugs and supply aircraft during the
Allied invasion of Europe during 1944–1945. In the aftermath of the Second World
War, the type was rapidly withdrawn from RAF service, having been replaced in
the transport role by the Avro York, a derivative of the Lancaster that had
previously displaced it from the bomber role. A handful of ex-military Stirlings
were rebuilt for the civil market.

Origins

In the 1930s, the Royal Air Force (RAF) was interested primarily in twin-engine
bombers. These designs put limited demands on engine production and maintenance,
both of which were already stretched with the introduction of so many new types
into service. Power limitations were so serious that the British invested
heavily in the development of huge engines in the 2,000 horsepower (1,500 kW)
class in order to improve performance. During the late 1930s, none of these were
ready for production. Both the United States and the Soviet Union were pursuing
the development of bombers powered by arrangements of four smaller engines, the
results of these projects proved to possess favourable characteristics such as
excellent range and fair lifting capacity. Accordingly, in 1936, the RAF also
decided to investigate the feasibility of the four-engined bomber.

The British Air Ministry published Specification B.12/36, which called for a
high-speed, long-range four-engined strategic bomber aircraft, that would be
capable of being designed and constructed at speed. Amongst the several
requirements specified, the bomb load was to be a maximum of 14,000 lb (6,350
kg) carried to a range of 2,000 miles (3218 km) or a lesser payload of 8,000 lb
(3,629 kg) to 3,000 miles (4,800 km) (incredibly demanding for the era). It was
to have a crew of six and was to have a normal all-up weight of 48,000lb, while
a maximum overload weight of 65,000lb was also envisioned. The aircraft would
have to be capable of cruising at speeds of 230 mph or greater while flying at
15,000 ft (4,600 m), while possessing three individual gun turrets (located in
nose, amidships and rear positions) for self-defence.

On 14 May 1939, the first S.29, which had by this point received the service
name "Stirling" after the Scottish city, performed its first flight. The first
prototype was outfitted with four Bristol Hercules II radial engines, and was
reported as having satisfactory handling in its two months of flying. However,
the entire programme suffered a setback when the first prototype suffered severe
damage and was written off as a result of a landing accident, in which one of
the brakes locked, causing the aircraft to slew off the runway and the landing
gear to collapse. A resulting redesign of the undercarriage led to substantially
stronger and heavier struts being installed upon the second prototype. On 3
December 1939, the second prototype made its maiden flight. During its first
sortie, one of the engines failed on take off but the second prototype managed
to land with relative ease.

Crew accommodation

Under typical operations, most variants of the Stirling were flown with a crew
of seven, performing several different roles. It was flown by a pair of pilots,
who were supported by a navigator/bomb aimer, a front gunner/wireless operator,
two further gunners, and a flight engineer. The flight engineer and wireless
operator were housed in a cabin just forward of the leading edge of the wing,
and directly forward of them was the navigator's station. The two pilots were
contained within a fully glazed flight deck positioned level with the forward
end of the bomb cells; the provision of a separate flight engineer's station led
to the cockpit having a relatively simple appearance in comparison with the
majority of the RAF's bombers.

The cockpit containing the flying officers was provided with numerous controls
and features; to the left of the first pilot were the controls for the
auto-pilot and a P.4 compass; the pilot was also provided with a beam approach
indicator (to aid nighttime landings) and DF visual loop indicator in addition
to the standard flight controls. Switches for the flaps and position indicators
were located on a central panel set between the two pilots, while the master
fuel cocks were set above these on the roof; throttle and mixture controls were
also normally positioned between the pilots. Only limited engine instrumentation
was provisioned for, such as engine speed indicators and boost gauges.

The navigator/bomb-aimer would perform the latter of these roles in a prone
position within the aircraft's nose. For bomb-aiming, a drift sight, camera, and
steering control over the auto-pilot were provided; directly above this position
was the front turret position of the bomber. Just aft of the wireless operator's
position, the centre section of the wing cut across the fuselage; the space
above this was used for storing oxygen tanks while the space below was used as a
rest bunk. Behind the rest area, the uninterrupted deck ran across the full
length of the bomb cells to the location in which the retractable ventral turret
was installed upon early production aircraft; the internal area aft of this
position were used to store flame floats and reconnaissance flares, as well as
an escape hatch, lavatory, rear turret position, and the crew entry door on the
port side.

The Stirling was armed with nose and tail turrets (the latter was notable for
the wide angles of fire) along with a single retractable ventral ("dustbin")
turret located just behind the bomb-bay. This proved almost useless due to
cramped conditions, with the added distraction that the turret tended to drop
and hit the ground when taxiing over bumps. The retractable turret was removed
almost from the start and temporarily replaced by beam hatches mounting pairs of
machine guns, until a twin-gun dorsal turret could be provided. This turret also
had problems; it had a metal back fitted with an escape hatch which turned out
to be almost impossible to use. The later Stirling Mk.III used a fully glazed
turret (the same FN.50 as in Lancaster) that had more room and an improved view.
Later Stirlings could also carry an improved, low-drag remotely-controlled FN.64
ventral turret.


Role
Heavy bomber
Glider tug

National origin
United Kingdom

Manufacturer
Short Brothers, Rochester
Short Bros. and Harland, Belfast
Austin Motor Company

Designer
Claude Lipscomb / Sir Arthur Gouge

First flight
14 May 1939

Introduction
1940

Retired
1946 (UK); 1951 (Egypt)

Status
Retired

Primary users
Royal Air Force
Egyptian Air Force

Produced
1939–1945

Number built
2,371

In July 1940, the first production Stirling departed Rochester; in August 1940,
it was delivered to No. 7 Squadron at RAF Leeming, North Yorkshire. Following a
four-month working-up period in which crews adapted to operating the type, the
Stirling attained operational status in January 1941. On the night of 10/11
February 1941, the first operational combat mission was performed, flown by the
first three Stirlings, against fuel storage tanks at Vlaardingen near Rotterdam,
the Kingdom of the Netherlands, all but two bombers were deployed during the
mission, which was considered to have run smoothly. By the end of 1941, more
than 150 Stirlings had been completed and a total of three RAF squadrons had
been equipped with the type. At this point, the Stirling was being deployed on
both daytime and nighttime bombing operations and had been found to be most
capable of standing up to enemy interceptor aircraft by using a sweeping
combination of fighters and bombers, a tactic which became known as the Circus
offensive.

From late 1941 onwards, the Stirling played a pioneering role in the formation
of the RAF's Pathfinder squadrons - bombers that were dedicated to indicating
targets for following bombers to more accurately deploy their payloads upon.
From the spring of 1942, the bomber started to be deployed in greater numbers.
From May 1943, raids on Germany were often conducted using over a hundred
Stirling bombers at a time. Stirlings were amongst the RAF bombers used during
the First 1,000 bomber raid against Cologne. Norris observed that, by 1942, the
type had "given plenty of punishment to the Germans, and was also proving that
it could itself take punishment to an incredible extent. There were several
incidents in which heavily damaged aircraft, such as one Stirling which suffered
a head-on collision with a Messerschmitt Bf 109 fighter over Hamburg, were able
to continue flying and safely return to base.

Despite the "disappointing performance" at maximum altitude, Stirling pilots
were delighted to discover that, due to the thick wing, they could out-turn the
Ju 88 and Bf 110 nightfighters they faced. Its handling was much better than
that of the Halifax and some preferred it to the Lancaster. Based on its flight
characteristics, Flt Lt Murray Peden (RCAF) of No. 214 Squadron RAF described
the Stirling as "one of the finest aircraft ever built". However, a consequence
of the thick wing was a low ceiling. Many missions were flown as low as 12,000
ft (4,000 m). This was a disadvantage on many raids, notably if crews were
attacking Italy and had to fly through (rather than "over") the Alps. When
Stirlings were on combined operations with other RAF bombers which could fly
higher, the Luftwaffe concentrated on the Stirlings. Within five months of being
introduced, 67 out of the 84 aircraft delivered had been lost to enemy action or
written off after crashes.

The Stirling's maximum bomb load could be carried for only a short distance of
around 590 miles (950 km). On typical missions deep into Germany or Italy, a
smaller 3,500-pound (1,600 kg) load was carried, consisting of seven 500-pound
(230 kg) GP bombs; this payload was in the range of that which was already being
carried by the RAF's medium bombers, such as the Vickers Wellington and, by
1944, the de Havilland Mosquito. Perhaps the biggest weakness present in the
design was that, although the bomb bay was large at 40 ft long (12 m), it had a
pair of structural dividers that ran down the middle, limiting the bay to
nothing larger than the 2,000-pound (910 kg) bomb. As the RAF started using the
4,000-pound (1,800 kg) "cookies" and even larger "specials", the Stirling became
less useful. The Handley-Page Halifax and especially the Avro Lancaster offered
better performance, so when these aircraft became available in greater numbers
from 1943, the Stirlings were relegated to secondary tasks.

During the type's service with Bomber Command, Stirlings flew a total of 14,500
sorties, during which 27,000 tons of bombs were dropped, and 582 aircraft were
lost in action while a further 119 were written off. By December 1943, Stirlings
were being withdrawn from frontline service as bombers. The aircraft continued
to be used on various alternative mission types, such as minelaying operations
in the vicinity of German ports ("Gardening" missions), electronic
countermeasures, and dropping spies deep behind enemy lines at night.

Specifications (Short Stirling I)

General characteristics
Crew: 7 (First and second pilot, navigator/bomb aimer, front gunner/WT operator,
two air gunners, and flight engineer)
Length: 87 ft 3 in (26.59 m)
Wingspan: 99 ft 1 in (30.20 m)
Height: 22 ft 9 in (6.93 m)
Wing area: 1,460 sq ft (136 m2)
Aspect ratio: 6.5:1
Empty weight: 49,600 lb (22,498 kg)
Gross weight: 59,400 lb (26,943 kg)
Max takeoff weight: 70,000 lb (31,751 kg)
Powerplant: 4 × Bristol Hercules XI 14-cylinder air-cooled sleeve-valve radial
piston engines, 1,500 hp (1,100 kW) each
Propellers: 3-bladed metal fully feathering constant-speed propeller, 13 ft 6 in
(4.11 m) diameter

Performance
Maximum speed: 282 mph (454 km/h, 245 kn) at 12,500 ft (3,800 m)
Cruise speed: 200 mph (320 km/h, 170 kn)
Range: 2,330 mi (3,750 km, 2,020 nmi)
Service ceiling: 16,500 ft (5,000 m)
Rate of climb: 800 ft/min (4.1 m/s)

Armament

Guns: 8 x 0.303 in (7.7 mm) Browning machine guns: 2 in powered nose turret, 4
in tail turret, 2 in dorsal turret
Bombs: Up to 14,000 lb (6,350 kg) of bombs




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