One of the Pearl Harbour B5N2s, armed with one of the special 1,653-lb.
bombs converted from a naval armour-piercing shell, flying from the
carrier Akagi.
When the Pacific War
exploded in all its fury on December 7, 1941, the Nakajima B5N2 carrier
torpedo bomber was the best in service with any of the world’s navies.
One hundred and forty-four aircraft of this type participated in the
Pearl Harbor attack as torpedo and level bombers, and they crippled the
American Pacific Fleet’s battleship force. During the following twelve
months, carrier-based B5N2s were to participate in sinking three
American aircraft carriers, while land- and carrier-based B5N2s
supported Japanese amphibious landings on all fronts. But by 1944, the
Kate, as it was code-named by the Allies, was plainly obsolete, and so
it finished out the war in second-line units, mainly as an
anti-submarine patrol plane.
The Japanese Navy never regarded its B4Y1 biplane torpedo bomber (a
contemporary of the essentially similar Fairey Swordfish) as anything
other than a stop-gap type, because they wanted a monoplane torpedo
bomber with performance more compatible with that of the Mitsubishi A5M
carrier fighter (which see). They issued, in 1935, a specification
calling for a single-engined monoplane “carrier attack bomber” (as the
Japanese termed torpedo bombers). The requirements called for: (1) a
wingspan of less than 52 ½ ft. with provision for hydraulic wing
folding to reduce the plane’s span to no more than 24 ft. 7 9/32 in.;
(2) an armament of one 1,764-lb. torpedo and a single rearward-firing
7.7mm machine gun for protection; (3) a maximum speed of 207 mph at
6,560 ft.; (4) a normal endurance of 4 hours or a maximum of 7 hours at
155 mph; (5) a normal crew of three; and (6) either a Nakajima Hikari
or Mitsubishi Kinsei radial engine.
Excellent close-up shot of a Kate's cockpit; note especially the
torpedo-launching sight.
Katsuji Nakamura’s
design team at Nakajima created a beautifully clean low-wing monoplane
with a hydraulically-operated retracting undercarriage. The large wing
folded upwards, and the hinging points were so arranged that the
wingtips overlapped one another when folded above the cockpit. When
compared to the large wing, the fuselage seemed oddly small, but it was
kept relatively short at 33 ft. 9 ½ in. to fit on the Navy’s standard
carrier elevators. Other innovations on the Type K, as the company
named its creation, were Fowler flaps and a variable-pitch propeller.
Powered by the Nakajima Hikari 2 nine-cylinder radial engine, the
prototype, given the official designation B5N1, first flew in January
1937. Hydraulic-system difficulties marred the initial flight tests,
but the troubles were soon fixed, and the JNAF was particularly pleased
with the B5N1’s speed, which at 230 mph exceeded the requirement by a
comfortable margin.
But they were worried
that the many technical innovations being introduced by the new
aircraft would make it excessively hard to maintain under operational
conditions. Nakajima accordingly simplified the second prototype,
changing the Fowler flaps to more conventional types and replacing the
hydraulic wing-folding mechanism with a manual one. It also had a newer
Hikari 3 engine with a constant-speed propeller-the first ever fitted
to a production Japanese naval plane of any type-and integral wing fuel
tanks with increased capacity. In this form the B5N1 easily won the
competition with Mitsubishi’s B5M1, and it went into production in
November of 1937 as the Navy Type 97 Carrier Attack Bomber Model 11
(B5N1 Model 11).
Carrier qualification trials were carried out at the same time the new
bomber was flying its first combat missions in China in the spring of
1938. Armed with bombs, the B5N1 was used as a single-engined level
bomber, in a fashion similar to a twin-engined machine. The observer,
who was seated between the pilot and the rear gunner/radio operator,
was also the bombardier during these missions; he would aim the bombs
using a pair of small folding doors in the floor of the fuselage to see
his target. Covered by A5M fighters, the B5N1 was a success despite its
lack of protection for the crew and fuel and its modest defensive
armament of a single 7.7mm machine gun. No major modifications were
necessary for China operations, and the only minor change made was to
add a mast antenna to replace the trailing antenna. But the JNAF was
aware that there would be other opponents than the Chinese, and so in
1939 they instructed Nakajima to develop a better-performing variant of
the B5N1.
The B5N2 Model 12, or Type 97 Carrier Attack Bomber Model 12, first
flew in December 1939; it was externally similar to the older variant
aside from its engine, a Nakajima Sakae 11 fourteen-cylinder radial. A
tighter-fitting cowling was used, to improve pilot view and reduce
drag, and a small hub was fitted to the propeller to further reduce
drag and improve the engine cooling. Oddly the B5N2 was not much faster
than the B5N1 in spite of the 36% increase in power, but the Navy was
pleased, as the Sakae was more reliable than the Hikari, and the B5N2
would fly most of its missions over long stretches of water.
A Kate from the carrier Zuikaku leaving Pearl Harbour; Hickam Field
lies below.
By the time of the
Pearl Harbor attack, the B5N2 had totally replaced the B5N1 in all
front-line units, both land- and carrier-based. Commander Mitsuo
Fuchida was the aerial commander for the Hawaiian Operation; he flew in
a B5N2 as observer/bombardier, and was also lead bombardier of the 49
Kates used as level bombers in the first wave. All of the B5N2 level
bombers carried a single 1,653-lb. bomb made from a remanufactured
armour-piercing shell. The 40 planes earmarked for the actual torpedo
attack were led by Lt. Cdr. Shigeharu Mutara, considered the finest
torpedo bomber pilot in the Imperial Navy if not the world. His planes
were carrying a specially modified torpedo for use in shallow harbours
like Pearl; the idea had been gleaned from study of the British attack
on Taranto, Italy, in December 1940, where Swordfish torpedo bombers
had sunk or crippled a number of Italian battleships. Stupidly, the
United States had ignored the lessons of Taranto, and had disdained
using torpedo nets at Pearl; they paid heavily for their neglect.
Between the high-level bombers and the torpedo planes, the US Navy lost
two battleships sunk outright, three more sunk but recoverable with
difficulty, and three damaged heavily (the Pennsylvania, in dry dock,
was damaged by dive bombers and strafing fighters).
But that did not end the B5N2’s career. In the furious carrier battles
of 1942, the Nakajima torpedo bomber played a prominent role in sinking
the American carriers Lexington, Yorktown, and Hornet. But in all those
battles losses were very heavy; Lt. Cdr. Murata, for example, was
killed in the Battle of Santa Cruz, shot down by US Navy fighter ace
Lt. (j.g.) Stanley “Swede” Vejtasa. Murata was just one of seven kills
Vejtasa scored that day, October 26, 1942 (in 1969, Vejtasa, as a
captain, was commander of Miramar NAS, and was one of the founders of
the “Top Gun” training program).
A captured B5N2 being manhandled by an American ground crew; the
objects protruding from the wing leading edge are antennas for
anti-shipping radar.
The Kate did most of
its later combat flying from land installations, figuring prominently
in the Solomons, Marianas, and Philippines campaigns. Its last
carrier-based engagement was the Battle of the Philippine Sea in June
1944. Insufficient performance, and poor crew and fuel-tank protection,
contributed to staggering losses in all these campaigns, and so the
Kate was relegated to second line and training units by the end of
1944. But the B5N2 found a new lease on life because it still had
excellent long range endurance; it was used for maritime reconnaissance
and anti-submarine patrol, in areas where Allied fighters were unlikely
to be encountered. The B5N2 gave Japanese convoys desperately needed
escort against the depredations of Allied submarines. Some B5N2s were
fitted with a primitive form of ASV (Air-to-Surface-Vessel) radar, with
antennas fitted along the rear fuselage sides and the wing leading
edges, and others were given Jikitanchiki magnetic airborne submarine
detection gear. The most war-weary B5N2s joined B5N1s in service as
trainers, target-tugs, and even tow planes for gliders.
One thousand, one hundred and forty-nine B5Ns were built, 669 by the
parent company Nakajima between 1936 and 1941, 200 by Aichi in 1942-43,
and 280 by the Naval Air Arsenal at Hiro in 1942-43. The B5N Kate
enjoyed a brief status as the finest torpedo bomber in the world, and
helped bring Japan to its pinnacle as an Empire; but eventually, its
increasingly poor performance and protection left it outclassed, and it
finished its operational life as a supernumerary, a spear-holder, as it
were.
Possibly the same captured Kate as in the previous photo; here, the
shadows thrown by the fuselage antennas can be seen.
Nakajima B5N (Kate)
Technical Data
Type:
Single-engined three-seat carrier-borne torpedo bomber. All-metal
construction with fabric-covered control surfaces.
Accommodation:
Crew of three; pilot, observer/navigator/bombardier, and
radio-operator/gunner, in enclosed cockpit.
Power plant:
(First prototype) One Nakajima Hikari 2 nine-cylinder air-cooled radial
engine rated at 700 hp for take-off and 800 hp at 11,485 ft.
(Second prototype and production B5N1) One Nakajima Hikari 3
nine-cylinder air-cooled radial, rated at 770 hp for take-off and 840
hp at 9, 945 ft.
(B5N2) One Nakajima NK1B Sakae 11 fourteen-cylinder air-cooled radial,
rated at 1,000 hp for take off and 970 hp at 9,845 ft.
Armament:
One flexible rearward-firing 7.7mm machine gun; bomb-load, one
1,764-lb. torpedo or the equivalent weight in bombs or depth-charges.
Dimensions, weights, and performance:
B5N1:
Wingspan, 50 ft. 10 15/16 in.;
length, 33 ft. 9 ½ in.;
height, 12 ft. 1 21/32 in.;
wing area, 405.798 sq. ft.;
empty weight, 4,643 lb.;
loaded weight, 8,157 lb.;
maximum weight, 8,852 lb.;
wing loading, 20.1 lb./sq. ft.;
power loading, 11.5 lb./hp;
maximum speed, 229 mph at 6,560 ft.;
cruising speed, 159 mph at 6,560 ft.;
climb to 9,845 ft., 7 min. 50 sec.;
service ceiling, 24,280 ft.;
normal range, 679 st. miles;
maximum patrol range, 1,404 st. miles.
B5N2:
Wingspan, 50 ft. 10 15/16 in.;
length, 33 ft. 9 ½ in.;
height, 12 ft. 1 21/32 in.;
wing area, 405.798 sq. ft.;
empty weight, 5,024 lb.;
loaded weight, 8,378 lb.;
maximum weight, 9.039 lb.;
wing loading, 20.6 lb./sq. ft.;
power loading, 8.4 lb./hp;
maximum speed, 235 mph at 11,810 ft.;
cruising speed, 161 mph at 9,845 ft.;
climb to 9,845 ft., 7 min. 40 sec.;
service ceiling, 27,100 ft.;
normal range, 608 st. miles;
maximum patrol range, 1,237 st. miles. |