The least known of the three big Luftwaffe bomber families of the war,
the Do 17/215/217 in its later variants provided the basis for a powerful and
well armed night fighter, and for capable bomber, reconnaissance and anti‑ship
platforms.
0ne of the enduring puzzles of World War II is why the Do
217, an extremely capable bomber, should have remained apparently unknown to
British intelligence despite the fact that the first prototype flew in a
completely open place in August 1938. Subsequent prototypes cleared most of the
surprising list of difficulties, and by December 1940 the Do 217E‑1 bomber was
in production. The surmise stemmed from the fact that the 217 was merely a
heavier and pore powerful version of the widely used Do 177.
To be frank the Do 17 was not the world’s greatest tactical
somber, though it was nice to fly and had no limitations whatever unlike the He
111 and Ju 88). The 217 was obviously potentially much pore formidable, with
BMW 801MA or MI, engines of 1179 kW 1,580 hp) for take‑off and a bombload of up
to 2500 kg (5,511 lb). In practice the initial major version, the 217E‑2,
entered Luftwaffe servicein 1941, long after the Battle of Britain
had been lost. Dornier Werke GmbH were never people to sit on their hands and
wonder what had gone wrong. In June 1941 Claudius Dormer made a formal proposal
for a Do 217 night‑fighter, and it came at the right time.
Even at the time the existing 217 was recognised as not by
any neaps an ‘ultimate’ aircraft‑ All versions were likely to weigh well over
13608 kg (30,000 lb) and probably more than 15876 kg 35,0()0 lb), and called
for 1492‑kW(2,ooo‑hp) engines that were not available. On the other hand the
basic 217 was a proven aircraft which many crews liked very much, and which
could obviously without changing the engines ‑ be converted into a night‑fighter.
The original E‑series internal fuel capacity of 2956 litres (650 Imp gals) was
unchanged; it was enough for interception missions with the NJG wings and
enough for intruder missions over England. The original E‑series bomber had
capacious bomb bays, and the nightfighter retained the rear bay to house (for
example) eight SC 5oX bombs of 50 kg (110 lb) each. In the forward bay was
installed a tank of 1160 litres (255 Imp gals), giving a handsome margin over
what aircrews might have expected.
The main, and obvious, change in the 217J night‑fighter was
the nose. Instead of a multi‑pane Plexiglas nose for a bomb aimer, the J‑I had
a ‘solid’ nose in which were installed four 20‑mm MG FF cannon and four 7.92‑mm
MG 17 machine‑guns. The E‑2’s aft defensive armament, comprising an MG131
dorsal turret and a hand‑aimed MG131 in the ventral position, was retained
unchanged. The J‑1 was operational from February 1942. Crews liked its
firepower and endurance, but found it a rather heavy brute which was sluggish
when fast manoeuvres were called for (not often) and needed bigger airfields
than most of those that were available. More serious was the lack of airborne radar, though in 1941‑42 most Luftwaffe
nightfighter pilots were far from convinced that such new gimmicks were worth
having.
Dornier has no record of the first flight of a 217J‑2, with
FuG 202 Lichtenstein BC radar, but it was probably in the spring of 1942. The J‑2
was a definitive night‑fighter, not an intruder, the bomb bays being
eliminated. The J‑2 was lighter than previous Do 217 versions, and despite the
`mattress’ of radar antennas the flight performance was almost the same as
before. Only small numbers were built, and few combat missions were flown
before 1943.
This was because, despite the heavy armament, the 217J was
never considered as anything but a stop‑gap. Except for Rudolf Schoenert, none
of the night‑fighter “experten” even considered the 217, and
Schoenert only had a soft spot for it because only this aircraft could
accommodate his invention of oblique upward‑firing guns ‑ later called schrage
Musik ‑ with virtually no extra drag. Schoenert’s original suggestion in 1941
was not proceeded with, but following tests with a Bf 110 and Do 17Z in 1942
the idea was resurrected. Schoenert managed to get three Do 217J‑1s converted
for tests at Wittmundhaven and Tarnewitz. Results were promising, and in winter
1942‑43 the 2 Jagddivision had three more 217s converted at Diepensee with a
more fully engineered installation of either four or (one aircraft) six
MG151/20s. In early 1943 these were tested with increasing success by
Schoenert’s 3/NJG 3. When Schoenert was given the command of II/NJG 5 (Bf 110s)
he brought his own 217 with him. As a result, a standard Rustsatze (factory
modification) R22, for installing four MG151s at an angle of 70° into either
the Do 217J or Ju 88C was introduced. These were the first schrage Musik kits
to be officially approved for general use.
Thus, in the matter of armament, the 217 led all the other nightfighters in 1942‑43, and it always had superior flight endurance. On the other hand its performance, as delivered by Dormer, was totally inadequate. None of the bomber’s equipment had been removed (apart from the bombsight), so the operational Gruppen (all of which used the 217J in a mix with other types, usually the 110) began removing as much as possible.
Flame‑dampers on the exhausts clearly had to stay, but the
rear defensive guns, armour, dinghy, dive brakes and (in the J‑1) bomb carriers
and release mechanism were all removed. This had a considerable beneficial
effect, maximum speed at optimum height of 5200 m (17,060 ft) rising from 430
to 510 km/h (26 7 to 317 mph) (still slower than the E‑2 bomber) and time to
climb to 5000 m (16,404 ft) being reduced from 35 to 24 minutes.
Meanwhile, from mid‑1941 the Dormer works had been
developing a series of different 217 versions. Several remained on the drawing
board, but two families were destined by 1943 to supplant the original E and J
sub‑types as the standard production models. The first of these new series was
the Do 217K, the first prototype of which (briefly fitted with a single‑fin
tail) made its maiden flight on 31 March 1942.
In all essentials the resulting production 217K‑1, which
began to come off production in about October 1942, was similar to the later E‑series,
and it was likewise intended for night bombing. The only significant changes
were fitting BMW 801D engines, giving a maximum power of 1268 kW (1,700 hp),
and a redesign of the forward fuselage. There had been nothing particularly
wrong with the original cockpit of the Do 17Z/215/217E, but Dormer ‑influenced
by Junkers’ development of the Ju 88B/188 ‑ developed a nose similar to that of
the He 177 and FW 191, with the front glazed part continued up to the top of
the fuselage. This had the slight drawback of making the pilot look ahead
through distant Plexiglas on which he tended to mis‑focus his eyes, especially
when the panes reflected lighted parts of the cockpit. At first the K‑1 had
MG81Z twin 7.92‑mm guns in the nose, two single MG81s firing to the sides/rear,
an MG131 in the dorsal turret and another MG131 in the rear ventral position.
Later two more MG81s were added firing to the sides. It was possible to fit the
R19 installation of one or two MG81Z firing astern from the tailcone, but it
was more common to have the R25 installation of a Perlon divebombing parachute.
Not many K‑is were built, at least one being fitted with underwing racks for no
fewer than four LT F5b torpedoes.
Running a few weeks later in timing, the Do 217K‑2 was the
heaviest of all production 217s, at 16850 kg (37,147 lb). It was specifically
developed to carry the FX1400 radio‑controlled heavy bomb, the He 111H having
been found not really suitable for the task. The massive bombs, also known as
Fritz X, were slung on special racks under the inner wings. An extra fuel tank
of 1160 litres (255 Imp gals) capacity was fitted into the forward bomb bay. To
carry the greatly increased weight the outer wings were extended in span from
19 to 24.8 m (62 ft 4 in to 81 ft 4 in), and handling and overall performance
remained satisfactory. Almost all K‑2s had the R19 fitting of twin MG81Z guns
(four in all) in the tail, and some even had an MG81Z firing aft from the tail
of each engine nacelle.
The K‑2’s greatest day was 9 September 1943. Maj Bernhard
Jope’s III/KG 100, based at Istres, made a concerted assault on the Italian
fleet as it sailed to join the Allies. The greatest battleship, Roma, took two
direct hits, blew up and sank within minutes. Her sister, Italia, limped to
Malta with 800 tons of water on board. Later the powerful bombs, each weighing
1570 kg (3,461 lb), crippled or sank many other ships. Some were launched by Do
217K‑3s, which instead of having the FuG 203a Kehl I/FuG 230a Strassburg
guidance link, had the FuG 203c or 203d Kehl IV with which the bomb aimer could
guide either FX 1400 or the smaller Hs 293A winged bomb.
The other production Do 217 family were the M bombers and N
night‑fighters. Structurally these were similar to earlier versions; in fact
the first 217M was merely a K‑1 fitted with Daimler‑Benz DB603A liquid‑cooled
engines, each of 1380 kW (1,850 maximum horsepower). The M‑1 went into
production almost straight away, being very similar to a K‑1 except for having
slightly better performance at high altitude. Not many were built, the need for
nightfighters being more pressing, but one achieved notoriety on the night of
23 February 1944 when it made a perfect belly landing near Cambridge (soon
flying in RAF markings), the crew having baled out over 100 km (62 miles) away
near London!
Despite its later suffix letter the corresponding night‑fighter,
the Do 217N, flew as early as 31 July 1942, the DB603 engine installation
having been designed in 1941. Production Do 217N‑1s began to reach the
Luftwaffe in January 1943. By this time critical feedback about the 217J had
been going on for many months, and the NJG crews were disappointed to find the
N‑1 incorporated none of their mostly obvious recommendations.
This was largely because the RLM, and Erhard Milch in
particular, disallowed any modifications that would reduce output or increase
costs. By mid‑1943, however, Dornier had switched to the N‑2, and also produced
the Ul conversion set with which existing night‑fighters could be modified. The
chief changes were to remove the dorsal turret and lower rear gun gondola and
add wooden fairings. The reduction in drag and removal of some two tonnes of
weight raised flight performance to a useful level, maximum speed at medium
heights exceeding 500 km/h (310 mph). With the devastating armament of four
MGl51s and four MG17s firing ahead and four more MG151s firing at 70° upwards,
the 217N‑2 was a vast improvement over the J‑1, and soon appeared with the FuG
220 Lichtenstein SN‑2 radar. By 1944 217Js and Ns were scattered over a vast
area of Germany and the occupied countries, as well as I/NJG 100 on the Eastern
Front. On the other hand no Gruppe was ever solely equipped with the Do 217,
and various problems militated against it ever becoming a top nightfighter as
did the Bf 110G and Ju 88G. In the case of the best subtype, the N‑2, the main
problem was an enduring series of troubles and shortages with the engines, so
that aircraft were continually being cannibalised. For example as early as July
1943 all 14 Do 217Ns of II/NJG 3 were lying around with damaged engines, leaving
the Gruppe to carry on with just seven Bf 110s. The point could also be made
that the same DB 603 engines powered the He 219, and this was not only nearly
200 km/h (124 mph) faster but it was also a superior night‑fighter in every way‑but
endlessly dogged by its own problems and production difficulties.
Total production of Do 217Js and Ns amounted to a mere 364,
terminating in October 1943. From April 1943 until Italy’s capitulation five
months later small numbers of Do 217J‑2s served with the 59° and 60° Gruppi of
the Regia Aeronautica. They saw little action and suffered severe attrition
from accidents and other problems.
Various related aircraft which never entered service were
all intended for flight at high altitudes. First to be started, as an entry in
the 1939‑40 Bomber B requirement, was the Do 317. This was to be basically a
217 with DB604 engines, each with four banks totalling 24 cylinders and giving
a maximum power of 1984 kW (2,660 hp) each, and with a four‑seat pressure cabin
in the nose. In 1940 this was dropped and some of its features used to assist
development of the Do 217P, which had a similar pressure cabin but was powered
by two DB603B engines supercharged by a large two‑stage blower and intercooler
in the rear fuselage, driven by a third engine, a DB605T. The first 217P flew
in June 1942, and there were plans for a production Do 217P‑0 reconnaissance
aircraft with almost the same extended outer wings as the K‑2 (raising service
ceiling to an estimated 16154 m /53,000 ft), but this was abandoned.
Meanwhile, in late 1941, the Do 317 was resurrected, and in
early 1943 the first 317 began flight testing. This was planned in two
versions. The 317A was a broadly conventional high‑altitude bomber with DB603A
engines, outwardly having much in common with the 217M apart from an odd tail
with triangular vertical surfaces. The next‑generation 317B was to have
extended wings of 26 m (85 ft) span, huge DB610 double engines each of 2141 kW
(2,870 hp), and defensive armament comprising a remotely controlled 20‑mm MG151
in the tailcone and three twin‑gun turrets, two of them remotely controlled.
Eventually the 317 also ground to a halt, but five of the 317A series
prototypes were modified as unpressurised launch aircraft for the Hs 293A radio‑controlled
missiles. Redesignated as Do 217Rs, they actually saw combat duty with III/KG
100 at Orleans‑Bricy in 1944. At 17770 kg (39,021 lb) they were the heaviest of
the whole 2171317 family actually to fly, though had they gone ahead, the 317A
and 317B would have been much heavier still.
