Henschel Hs 129

https://en.wikipedia.org/wiki/Henschel_Hs_129

The Henschel Hs 129 was a World War II ground-attack aircraft fielded by the
German Luftwaffe. The aircraft saw combat in Tunisia and on the Eastern Front.

A key requirement of the original specification was that the aircraft be powered
by engines that were not in demand for other designs. Prototypes with low-power
German Argus As 410 engines of 465 PS (459 hp; 342 kW) failed acceptance test, a
more powerful replacement was found with the French Gnome-Rhône 14M engine of
700 PS (690 hp; 515 kW).

The design was relatively effective when it was first introduced, and saw
service on the Eastern Front in a variety of front-line roles. As the war
continued and anti-tank support became the main goal, the aircraft was
continually up-gunned, eventually mounting a 75 mm gun in the anti-tank role
that left the plane barely flyable. Only a small number of these B-3 models were
produced, late in the war.

By the mid-1930s, the German military, as well as its counterparts in other
countries, had come to see the main role of ground-attack aircraft as the
interdiction of logistics and materiel, a task in which targets were often
poorly protected and less likely to be defended by strong, well-coordinated
defences. For high-value, well-protected tactical targets, the dive bomber was
becoming the conventional solution.

The experience of the German Kondor Legion during the Spanish Civil War
(1936–39) refuted this idea. Even though it was equipped with types unsuited to
the role, such as the Henschel Hs 123 and cannon-armed versions of the Heinkel
He 112, the Kondor Legion proved that ground-attack aircraft were a very
effective weapon. This led to support within the Luftwaffe for the creation of
an aircraft dedicated to this role, and the Reichsluftministerium (RLM; "Reich
Air Ministry") requested tenders for a specialized ground attack aircraft.

It was anticipated that the main source of damage to such an aircraft would be
small arms fire from the ground, meaning that the plane had to be well-armored
around its cockpit and engines. Similar protection was also needed in the
canopy, in the form of 75 mm (2.95 in) thick armored glass. The aircraft was
expected to be attacking in low-level, head-on strafing runs, so the cockpit had
to be located as close as possible to the nose, in order to maximize the
visibility of its targets. Another, non-operational, requirement severely
hampered the designs: the RLM insisted that the new design be powered by engines
that were not being used in existing aircraft, so that the type would not
interfere with the production of established types deemed essential to the war
effort.

Prototypes

The Hs 129 was designed around a single large "bathtub" of steel sheeting that
made up the entire nose area of the plane, completely enclosing the pilot up to
head level. Even the canopy was steel, with only tiny windows on the side to see
out of and two angled blocks of glass for the windscreen. In order to improve
the armor's ability to deflect bullets, the fuselage sides were angled in
forming a triangular shape, resulting in almost no room to move at shoulder
level. There was so little room in the cockpit that the instrument panel ended
up under the nose below the windscreen where it was almost invisible; some of
the engine instruments were moved outside onto the engine nacelles'
inboard-facing surfaces and the gunsight was mounted outside on the nose.

Henschel's plane came in 12 percent overweight with the engines 8 percent
underpowered, and understandably, it flew poorly. The controls proved to be
almost inoperable as speed increased, and in testing, the V2 prototype flew into
the ground from a short dive on 5 January 1940 because the stick forces were too
high for the pilot to pull out. The Focke-Wulf design proved to be no better.
Both planes were underpowered with their air-cooled, inverted-V12 Argus As 410
engines, and very difficult to fly.

The RLM nevertheless felt they should continue with the basic concept. The only
real deciding factor between the two designs was that the Henschel was smaller
and cheaper. The Focke-Wulf was put on low priority as a backup, and testing
continued with the Hs 129 A-0. A series of improvements resulted in the Hs 129
A-1 series, armed with two 20 mm MG 151/20 cannons and two 7.92 mm (.312 in) MG
17 machine guns, along with the ability to carry four 50 kg (110 lb) bombs under
the fuselage centreline.

Hs 129 B-3

A closeup of the Bordkanone BK 7,5 75 mm cannon.
It was decided that the 7.5 cm (2.95 in) semi-automatic Rheinmetall PaK 40
anti-tank gun, which had already been adapted for use in the Junkers Ju 88P-1,
would be further modified for use in the Hs 129. This resulted in the BK 7,5
(Bordkanone 7,5), which, even though it weighed 1,200 kg (2,600 lb), was lighter
than the PaK 40. Fully automatic, it featured a new, hydraulic recoil-dampening
system and a new, more aerodynamic muzzle brake. An autoloader system, with 12
rounds in a rotary magazine, was fitted in the empty space behind the cockpit,
within the rear half of the wing root area. The gun and its recoil mechanism
occupied a substantial gun pod under the fuselage, and a circular port at the
rear of the pod allowed rearwards ejection of spent cartridges immediately after
firing. While this new variant, the Hs 129 B-3, was theoretically capable of
destroying any tank in the world, the added weight worsened the aircraft's
general performance and it was inferior to previous variants.

The Bordkanone 7,5 was the heaviest and most powerful forward-firing weapon
fitted to a production military aircraft during World War II. The only other
aircraft to be factory-equipped with similar-calibre guns were the 1,420
examples of the North American B-25G and B-25H Mitchell, which mounted either a
75 mm (2.95 in) M4 cannon, or lightweight T13E1 or M5 versions of the same gun.

From June 1944, only 25 examples of the Hs 129 B-3 arrived at frontline units
before the production line was shut down in September (a small number were
reportedly also created by converting B-2 aircraft). In the field the B-3 proved
effective, but its small numbers had little effect on the war effort.

Specifications (Hs 129B-2)

General characteristics
Crew: 1
Length: 9.75 m (32 ft 0 in)
Wingspan: 14.2 m (46 ft 7 in)
Height: 3.25 m (10 ft 8 in)
Wing area: 29 m2 (310 sq ft)
Empty weight: 4,020 kg (8,863 lb)
Max takeoff weight: 5,250 kg (11,574 lb)
Powerplant: 2 × Gnome-Rhône 14M-4/-5 14-cylinder air-cooled radial engine, 515
kW (691 hp)700 PS each for take-off
Propellers: 3-bladed Ratier constant speed propeller, 2.6 m (8 ft 6 in) diameter

Performance
Maximum speed: 407 km/h (253 mph, 220 kn) at 3,830 m (12,570 ft)
Cruise speed: 315 km/h (196 mph, 170 kn) at 3,000 m (9,800 ft)
Range: 690 km (430 mi, 370 nmi)
Service ceiling: 9,000 m (30,000 ft)
Rate of climb: 8.1 m/s (1,590 ft/min)

Armament

Guns:
2 x 7.92 mm (0.31 in) MG 17 machine guns, later models from 1943 to 1944
replaced the MG 17s with 2 x 13 mm (.51 in) MG 131 machine guns
2 x 20 mm MG 151/20 cannon or
a 30 mm (1.181 in) MK 101 cannon or MK 103 cannon in a conformally mounted gun
pod (B-2/R-2).

Bombs:
2 x 50 kg (110 lb) bombs on underwing hardpoints
4 x 50 kg (110 lb) fragmentation bombs on belly racks




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