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Henschel Hs 129
The Henschel Hs 129, often referred to by its nickname, the Panzerknacker, (tank cracker), was a World War II ground attack aircraft fielded by the Luftwaffe. Although likely to be a good anti-tank weapon, the plane was produced in only small numbers and deployed during a time when the Luftwaffe was unable to protect them from attack.
By the middle of the 1930's the idea of using aircraft against ground targets had been "well understood" to be of little use other than hurting enemy morale. But the Condor Legion proved the opposite in Spain with attack planes like the Henschel Hs 123 and cannon-armed versions of the Heinkel He 112. Although these planes were poorly suited to the role, their powerful armament and fearless pilots proved that the aircraft was a very effective weapon even without bombs.
This led the Luftwaffe to issue a tender for a new plane that was built specifically for the ground-attack role. The plane had to be heavily armored around the cockpit and engines, and include a 75 mm thick armored windscreen that had to be as close as possible to the nose in order to see the ground during low level strafing runs. One last requirement doomed the designs, they needed to be powered by "unimportant" engines of low power. Four companies were asked to respond, and only two of the resulting three entries were considered worthy of consideration; Focke-Wulf's conversion of their earlier Fw 189 reconnaissance plane, and Henschel's new Hs 129.
Design and 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 stop bullets the sides were angled in forming a triangular fuselage, 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, and the gunsight was mounted outside on the nose.
In the end the plane came in 12% overweight and the engines 8% underpowered, so it flew like a pig. The controls proved to be almost inoperable as speed increased, and in testing one plane flew into the ground from a short dive because the stick forces were too high for the pilot to pull out. The Fw design proved to be no better, both planes were underpowered with their Argus 410 engines, and very difficult to fly. In the end the only real deciding factor 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 129A-0.
A series of improvements resulted in the Hs 129A-1 series, armed with two 20 mm MG 151/20's and two 7.92 mm MG17's, along with the ability to carry four 50kg bombs under the midline. But even before the A-1's were delivered the plane was redesigned with the Gnôme-Rhône 14M radial engine, which were captured in some number when France fell. This engine supplied 700 hp (522 kW) for takeoff compared to the Argus at 465 hp (347 kW). The A-1 planes were converted into Hs 129B-0's for testing (although some claim that some A's were sold to Romania) and the pilots were reportedly much happier. Their main complaint was the view from the canopy, so a single larger windscreen and a new canopy with much better vision were added, resulting in the production model Hs 129B-1.
B-1's started rolling off the lines in December 1941, but they were delivered at a trickle. In preparation for the new plane, I./Sch.G 1 had been formed up in January with 109's and Hs 123's, and they were delivered B-0's and every B-1 that was completed. Still, it wasn't until April that 12 B-1's were delivered and its 4th staffeln was ready for action. They moved to the eastern front in the middle of May, and in June they received a new weapon, the 30 mm MK 101 cannon with armor-piercing ammo in a midline pod.
By May of 1942 only 50 of the planes had been delivered when they started to deliver the new Hs 129B-2 model side-by-side with the B-1. The only difference between the two were changes to the fuel system – a host of other minor changes could be found almost at random on either model. As time went on these changes were accumulated into the B-2 production line until you could finally tell them apart at a glance, the main differences being the removal of the mast for the radio antenna, the addition of a direction-finding radio antenna loop, and shorter exhaust stacks on the engines.
In the field the differences seemed to be more pronounced. The R-kits were renumbered and some were dropped, and in general the B-2 planes received the upgraded cannon pack using a MK 103 instead of the earlier MK 101. These guns both fired the same ammunition, but the 103 did so about almost twice the rate.
|Close up of the BK 7,5 cannon|
Even by late 1942 complaints started about the MK103 against newer versions of the Soviet T-34 tanks. One solution would be to standardize on the larger 37 mm gun, itself adapted from an anti-tank gun that had recently been abandoned by the army. For some reason the Luftwaffe decided to skip over this gun (although it served perfectly well on the Ju 87), and install a 75 mm gun from the Panzer IV. A huge hydraulic system was used to damp the recoil of the gun, and an auto-loader system with twelve rounds was fitted in the large empty space behind the cockpit. The resulting system was able to knock out any tank in the world, but the weight slowed the already poor performance of the plane to barely flyable in this new Hs 129B-3 version.
B-3's only started arriving in June 1944, and only 25 were delivered by the time the lines were shut down in September. A small number were also converted from older B-2 models. In the field they proved deadly weapons, but with only 25 of them they had no effect on the war effort.
In order to address the poor performance of the aircraft, plans had been underway for some time to fit the plane with newer versions of the Italian Isotta-Fraschini Delta engine that delivered 850 hp (634 kW). However the engine ran into a number of delays, and was still not ready for production when the plant was overrun by the Allies.
See also: Henschel & Son
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