The origin of the
B-18 can be traced back to the same 1934 Army
competition that led to the famed Boeing B-17. In
May of 1934, the Army announced a competition for a
multi-engined bomber capable of carrying a ton of
bombs at more than 200 mph over a distance of 2000
miles. This Army requirement envisaged from the
start that the winning design would have a
production run of as many as 220 planes. Several
manufacturers were invited to submit bids, with the
entries to be flown at Wright Field in a final
competition to select the winner.
The Douglas entry
bore the company designation of DB-1. It drew
heavily on the company's experience with its DC-2
commercial airliner. The DB-1 was designed around
the wings of the DC-2 and was fitted with a deeper
and fatter fuselage which contained a bomb bay
within its center section. The DB-1 had larger tail
surfaces than did the standard DC-2, plus a wing
with a slightly larger span and area resulting from
the fitting of rounded tips. A six-man crew was
carried (two pilots, one navigator/bombardier, plus
3 gunners). Defensive armament consisted of three
0.30-cal machine guns, one each in manually-operated
nose and dorsal turrets, and one firing from a
ventral hatch. The dorsal turret was located just
ahead of the vertical fin and was fully retractable.
It was rather unusual in having a rectangular top,
so that it could lie flush with the upper fuselage
when retracted. A 4400-pound bombload could be
carried in the bomb bay.
The DB-1 made its
first flight in April of 1935, powered by a pair of
850 hp Wright R-1820-G5 air-cooled radials. Maximum
speed was 233 mph, with cruising speed being 173
mph. Range was 2030 miles with a 2000- pound
bombload. Service ceiling was over 25,000 feet. It
was delivered to Wright Field for the competition in
August of 1935. Competitors included the Martin 146,
which was a streamlined and enlarged version of the
B-10 twin-engined light bomber then already in Army
service, plus the four-engined Boeing 299, which was
eventually to emerge as the famed B-17 Flying
Fortress.
Test flights proved
the DB-1 to be inferior in almost every respect to
the Boeing 299. However, the DB-1 did have the
advantage over the Boeing design in being
substantially cheaper. In addition, the crash of the
Boeing 299 on October 30, 1935 caused the USAAC to
opt for the conservative approach, and on January
28, 1936 they ordered 82 B-18s, with the order being
increased to 132 by June. Fortunately, the Army also
ordered 13 Boeing YB-17s.
Production B-18s were
powered by a pair of 930 hp Wright R-1820-45 radials
housed in revised cowlings. The nose cone was
somewhat shorter than that of the DB-1 prototype,
and it contained more lateral windows as well as a
bomb-aiming window in its forward lower portion.
With full military equipment fitted, the performance
of the production B-18 fell off slightly, to a
maximum speed of 217 mph, cruising speed of 167 mph,
and combat range of 850 miles. Nevertheless, the
B-18 was the most modern bomber design then
available to the Army.
The first production
B-18 was delivered to Wright Field on February 23,
1937. The DB-1 prototype was brought up to full B-18
standards and was redelivered to the Army five days
later as serial number 37-51.
The DB-2 was a B-18
airframe fitted in March 1937 with a power-driven
nose turret with an extensively-glazed large
bombardier's enclosure. It bore the serial number
37-34, which identified it as the last aircraft
ordered on the original B-18 contract. However, it
was delivered out of sequence, and it was actually
the 36th B-18 to be delivered when it was received
at Wright Field on November 8, 1937. This modified
nose did not prove satisfactory, and the aircraft
was eventually converted back to standard B-18
configuration before being delivered to the 18th
Reconnaissance Squadron at Mitchel Field, New York.
The second (and last)
major production version of the Douglas bomber was
the B-18A. The B-18A differed from the B-18 in
having the bomb-aimer's position moved upward and
forward underneath an extended glazed housing, while
the flexible forward-firing nose gun was moved
further back and below and was mounted inside a
globular ball turret. This led to the rather unusual
geometry in which the bombardier sat above and ahead
of the nose gunner. A transparent domed cap was
added to round off the top of the dorsal turret, so
that it no longer lay flush with the fuselage when
retracted. The B-18A was powered by two 1000-hp
Wright R-1820-53 radials driving fully-feathering
propellers.
177 B-18As were
ordered on June 10, 1937, with 78 more being added
to the contract on June 30, 1938. The B-18A flew for
the first time on April 15, 1938. The first B-18A
was delivered to the Army in April of 1938, with the
last example being delivered in January of 1940.
Only 217 out of the 255 ordered were actually
delivered as B-18As, the last 38 examples being
built as B-23s.
Fearing the imminent
breakout of war in Europe, a delegation from the
British Air Ministry toured the Douglas plant in
late 1938 seeking to purchase combat aircraft.
Douglas was unable to interest the British in the
B-18 design, as it was deemed by the RAF to have
insufficient power, poor airfield performance, and
inadequate defensive armament. The RAF chose to
order the Lockheed Hudson instead. However, Douglas
did succeed in acquiring an order for 20 B-18A from
the Royal Canadian Air Force (RCAF). In Canadian
service, these 20 planes were designated Digby Mk 1.
The Digby was generally similar to the USAAC's
B-18As, but had 0.303 cal machine guns as well as
some other British and Canadian equipment. The first
Digby entered RCAF service in late 1939. These
carried the Canadian serial numbers 738 thru 757.
They served with No 10 (BR) Squadron, where they
were assigned the duty of patrolling the North
Atlantic in search of German U-boats.
In 1939, the DB-1
prototype (which had been delivered to the Army as
serial number 37-51) was modified to test the
feasibility of firing large-caliber cannon from
aircraft. A forward-firing 75-mm cannon was mounted
in a fixed position in the bomb bay and the nose was
cut down to accommodate the muzzle. Initial tests
were carried out over Lake Erie and at the Aberdeen
Proving Grounds in Maryland. Vibration during firing
proved excessive, and the experiments were
eventually discontinued. However, the data gathered
was of great value in developing the B-25G and H
cannon-firing versions of the North American
Mitchell medium bomber during the war.
In 1940, 22 B-18s and
17 B-18As had their D-3 and B-7 bomb shackles
removed so that larger bombs could be carried. They
were redesignated B-18M and B-18AM respectively.
Deliveries of B-18s
to Army units began in the first half of 1937, with
the first examples being test and evaluation
aircraft being turned over to the Materiel Division
at Wright Field, Ohio, the Technical Training
Command at Chanute Field, Illinois, the Aberdeen
Proving Ground in Maryland, and Lowry Field in
Colorado. The first operation unit to receive the
B-18 was the 7th Bombardment Group based at Hamilton
Field in California. B-18s later went to the 5th
Bombardment Group at Luke Field, Oahu, the 19th
Bombardment Group and 38th Reconnaissance Squadron
at Mitchel Field, and the 21st Reconnaissance
Squadron at Langley Field, Virginia. These units
were also later supplemented with B-18As, with
B-18As also being supplied to the 2nd Bombardment
Group at Langley Field.
By the early 1940s,
the deficiencies in the B-18/B-18A bomber were
becoming readily apparent to almost everyone. In
range, in speed, in bombload, and particularly in
defensive armor and armament, the design came up
short, and the USAAC conceded that the aircraft was
totally unsuited in the long-range bombing role for
which had originally been intended. To send crews
out in such a plane against a well-armed, determined
foe would have been nothing short of suicidal.
However, in spite of the known shortcomings in the
B-18/B-18A, the Douglas aircraft was the most
numerous American bomber type deployed outside the
Continental United States at the time of Pearl
Harbor. It was hoped that the B-18 could play a
stopgap role until more suitable aircraft became
available in quantity.
In early December of
1941, the 5th and 11th Bombardment Groups at Hickam
Field, Hawaii had 33 B-18s on strength, whereas the
28th Bombardment Squadron at Clark Field in the
Philippnes had twelve. B-18/B-18As were also
stationed with the 6th Bombardment Group in the
Canal Zone, with the 9th Bombardment Group stationed
at airfields in Trinidad, St. Lucia, and Surinam.
When war came to the Pacific, most of the B-18/B-18A
aircraft based overseas in the Philippines and in
Hawaii were destroyed on the ground in the initial
Japanese onslaught. The few Douglas bombers that
remained played no significant role in subsequent
operations.
The Bolos remaining
in the continental USA and in the Carribean were
then deployed in a defensive role in anticipation of
attacks on the US mainland. Fortunately, these
attacks never materialized. In 1942, 122 B-18As were
modified for the maritime reconnaissance bombing
role to counter the U-boat menace. These modified
aircraft were redesignated B-18B. An SCR-517-T-4 ASV
(air to surface vessel) radar set was mounted under
a radome in the nose, replacing the bombardier's
shark-nose glazed area. The bombardier's station was
moved below and behind the radome, where the forward
turret had formerly been located. In addition, a Mk
IV Magnetic Anomaly Detector (MAD) set was installed
in a long tubular boom that extended behind and
below the the rudder. Some B-18Bs were also equipped
with a set of retro bombtracks underneath the wings
which could fire bombs backwards in a prearranged
pattern.
B-18Bs are credited
with two U-boat kills--U-654 on August 22, 1942 and
U-512 on October 2, 1942. The antisubmarine role was
relatively short lived, and the Douglases were
superseded in this role in 1943 by the B-24
Liberator which had a substantially longer range and
a much heavier payload.
Like their American
counterparts, the RCAF Digbys were also employed on
maritime reconnaissance missions to counter the
U-boat menace. The Canadian Digbys are credited with
one U-boat kill. This was U-520 which was sunk on
October 3, 1942 by Digby #757 PB-K of 10 (BR)
Squadron operating out of Dartmouth (Halifax, Nova
Scotia). By mid-1943, the RCAF Digbys had been
superceded by Liberator GR. Vs in the anti-submarine
role,
Two B-18s ended up
serving in Brazil. 6300 (ex USAAF 36-300) and 7032
(ex USAAF 37-32) served with the Agrupamenato de
Avioes de Adatacao, which was a provisional
conversion training unit set up under the provisions
of Lend-Lease. They were later used for anti-
submarine patrols. They were struck off charge at
the end of the war. Another B-18 was used as an
instructional airframe, but I am unaware of its
serial number.
Surviving USAAF B-18s
ended their useful lives in training and transport
roles within the continental USA, and saw no further
combat action. Two B-18As were modified as unarmed
cargo transports under the designation C-58. At the
end of the war, those bombers that were left were
sold as surplus on the commercial market. Some
postwar B-18s of various models were operated as
cargo or crop-spraying aircraft by commercial
operators. The last Canadian Digby was struck off
strength by the RCAF in 1946. So ends the career of
one of the lesser lights of the Second World War.
The Air Force Museum
at Wright-Patterson AFB in Dayton, Ohio has B-18A
serial number 37-469 on display. It is equipped with
a rectangular-topped dorsal turret from a B-18.
Other preserved B-18As include 37-029 at Castle AFB
Museum, 37-505 at McChord AFB Museum, 38-593 at the
Pima museum, and 39-025 at Cannon AFB Museum
B-18 serials:
36-262/343
36-431/36-446
37-1/34.
29 is on display at Castle Air Museum, CA
B-18A serials:
37-458/634
469 is on display at US Air Force Museum, Wright
Patterson AFB, OH.
505 on display at McChord AFB, WA.
593 on display at Pima Air and Space Museum, Tucson, AZ.
38-585/609
39-12/64.
25 on display at Wings Over the Rockies museum,
Denver, CO.
B-18As 39-27/64 were delivered as B-23s
Specification of
Douglas B-18:
Two Wright R-1820-45
air cooled radials, rated at 930 hp for takeoff and
810 hp at 10,200 feet. Maximum speed 217 mph at
10,000 feet. Cruising speed 167 mph. Landing speed
64 mph. Service ceiling 24,200 feet. Absolute
ceiling 25,850 feet. Initial climb rate 1355 feet
per minute. An altitude of 10,000 feet could be
attained in 9.1 minutes. Range was 1082 miles with
2200 pounds of bombs and 412 gallons of fuel, or
1200 miles with 4400 pounds of bombs and 802 gallons
of fuel. Maximum ferry range was 2225 miles.
Dimensions: wingspan 89 feet 6 inches, length 56
feet 8 inches, height 15 feet 2 inches, wing area
959 square feet. Weights: 15,719 pounds empty,
21,130 pounds gross, 27,087 pounds pounds maximum
takeoff. Normal bombload was 2200 pounds, but a
maximum bombload of 4400 pounds could be carried.
Armed with three 0.30-inch machine guns in nose,
dorsal, and ventral positions.
Specification of
Douglas B-18A:
Two Wright R-1820-53
air cooled radials, rated at 1000 hp for takeoff and
850 hp at 9600 feet. Maximum speed 215.5 mph at
10,000 feet. Cruising speed 167 mph. Landing speed
69 mph. Service ceiling 23,900 feet. Absolute
ceiling 25,600 feet. Initial climb rate 1030 feet
per minute. An altitude of 10,000 feet could be
attained in 9.9 minutes. Range was 1150 miles with
2496 pounds of bombs. Dimensions: wingspan 89 feet 6
inches, length 57 feet 10 inches, height 15 feet 2
inches, wing area 959 square feet. Weights: 16,321
pounds empty, 22,123 pounds gross, 27,673 pounds
pounds maximum takeoff. Normal bombload was 2200
pounds, but a maximum bombload of 4400 pounds could
be carried. Armed with three 0.30-inch machine guns
in nose, dorsal, and ventral positions.
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