The Hs 123 and its odd success

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(Finally, the promised Hs 123 blog post.)

The Henschel Hs 123 was one of the most interesting WW2 aircraft; superficially an anachronism and badly outdated, it proved to be an incredible pilot's airplane, surprisingly survivable, surprisingly long-lived, surprisingly effective - and both its important strengths and flaws weren't visible on spec sheets, ever.

The Henschel Hs 123 story has two roots;

(1) The metal works company Henschel, a newcomer to the aviation industry business, had proven its competence in aircraft design to the German aviation ministry by developing a training aircraft. This was standard procedure for new German aircraft developers in the 1933-1935 time frame and it's still a favourite for aviation design newcomers to date (just look at the many recent jet trainer designs originating in developing countries!)

(2) Ernst Udet, highest-scoring surviving German WWI fighter ace and acclaimed aerobatics pilot, became a proponent for dive attack tactics in Germany. He imported even a few Curtiss Hawk II biplanes (export version of Curtiss F11C-2 Goshawk, a naval fighter with secondary light bomber capability).

XF11C-2 Goshawk, 1932

This led eventually to a dive bomber tender in Germany (1935), and Henschel participated with a traditional design not much unlike the Goshawk; the Hs 123.

This biplane, fixed landing gear aircraft appeared at about the same time as the first generation of German monoplane retractable landing gear fighters and looked obsolete immediately. It did nevertheless push all contenders out of the competition (including a monoplane) with its flight characteristics.

Its most modern characteristic was the use of  an all-metal structure and surface (Duraluminium, an aluminium alloy that first became famous for its use in large airships). Only the early A version still had some textile wing surfaces.

The final serial production standard evolved not until 1937, but in that year the Hs 123 has proven that it was able to compete with the modern Bf 109 fighter (in its contemporary version) in regard to climb rate; the power:weight ratio is the main input variable for climb rate, and the Hs 123 was using a powerful radial engine. It was also very strong in horizontal air combat manoeuvrability (turning radius).

Henschel Hs 123 V2 (2nd prototype)

One interesting thing about the Hs 123 is that it routinely carried a 130 litre external fuel tank. This could be jettisoned, but it being made of aluminium meant that this was expensive and thus only an emergency action. The flight radius of the Hs 123 was poor even with this fuel tank but this proved to be not much of a problem because the aircraft was capable of being flown and maintained on most primitive forward airfields (a field was deemed suitable for Hs 123 if you could drive over it with a car at 50 km/h). This proximity to the front line enabled many sorties per day during important battles and neutralised the range issue. The continued use of a drop tank does nevertheless prove that the Luftwaffe had understood this piece of equipment long before the 1940 Battle of Britain. Ultimately, the short-ranged Bf 109E fighters proved to be unsuitable in that important (yet still a bit overrated) air battle due to lack of range. It had no drop tank (until late in 1940).

The Hs 123 proved to be structurally deficient for a dive bomber, necessitating a structural reinforcement. This is somewhat odd, for the aircraft's structure also proved to be extremely robust and resilient to combat damages in the close air support role and during use on most primitive airfields.

Germany was involved in the Spanish civil war at the time of the Hs 123's early career and a squadron of these aircraft were sent to Spain. The success in the ground attack role (close air support; CAS) was visible immediately.

There's nothing in the specs that points at it; there was no special armour installed at the time, it had only the two standard machine guns and its 4 x 50 kg or 4 x 70 kg bomb armament was not outstanding in any way (except if compared to fighters).

The Hs 123 was still in service in late 1939, but only 40 aircraft were used in September 1939 over Poland. By that time, the Hs 123 were mostly dispersed in training units and it was long since regarded to be a close air support aircraft (a "Schlachtflieger"), not a dive bomber ("Sturzkampfflugzeug") for interdiction missions. Udet's preference for dive bombing had become the dominant view by 1939 because Udet had become responsible for the development and procurement of military aircraft in general. There was nevertheless a major general Wolfram von Richthofen, who preferred close air support and the Hs 123 over dive bomber interdiction messages with Ju 87 (at least since he had experienced the Hs 123's abilities over Spain). Ironically, this general was later most successful and much-decorated with an air force corps that was primarily in the business of using Ju 87 dive bombers to best effect over the Soviet Union.

Henschel Hs 123 A-1 (early series)

The Hs 123 demonstrated a strange ability over Spain and Poland; this was a combination of flying characteristics and acoustic oddity. The aircraft was slow, manoeuvrable and yet stable enough for extremely low level flight at only about 8-10 metres altitude (that's 30 ft). Its BMW 132A engine produced a terrifying sound (similar to machine gun fire) at 1,800 rpm (other sources claim the sound came from the propeller, but they agree on the rpm). The combination of both frequently led to panic among enemy ground forces.

This trick was probably only effective because these aircraft were a rarity, for neither the bombs nor the machine guns could be used during such acoustic-visual attack runs. The bombs would have destroyed the aircraft itself and the machine gun synchronisation was not safe at this rpm setting.

The Hs 123 was kept in service despite its obsolete appearance simply because it was so extremely successful as close air support aircraft. It participated in the Benelux and France campaigns, in the Balkan campaign and it was used over the Soviet Union and even Tunisia. Training aircraft were sent to front-line units again and even ten new Hs 123 were produced with spare parts.

The total strength at the end of August 1941 was 152 Hs 132, 99 had been lost so far. This strength dropped to 140 till end of 1941, and the Hs 123 was the last aircraft type that had to cease operations due to the extremely bad Russian winter weather. The Hs 123 was furthermore upgraded during 1942, adding some armour for the pilot.

Enemy fighters were apparently no significantly greater threat to Hs 123 pilots than friendly fire. Few Hs 123 were lost to fighters, and this was apparently a consequence of its ruggedness (there were few critical components that hits could take out and the structure was strong enough to tolerate several 20 mm HE hits), its low speed (the typically much faster fighters had very little time for actually firing at a Hs 123) and great agility (good for both dodging fire and making slowing down unacceptable for enemy monoplane fighters).

The extremely odd request for a renewed production of Hs 123 in 1942 or 1943 (sources vary on this) is a direct consequence of both the great utility of the Hs 123 and the lack of a superior alternative. It was denied, and the usually recounted reason is that the tools were already scrapped. In other words; a renewed production would have started slowly and at high fixed costs. By this time, close air support groups were converting to Fw 190F fighter-bombers (the version modified for CAS) which were in addition to their qualities as fighter-bombers also capable auxiliary fighters against enemy CAS and bomber aircraft

The front-line career of the Hs 123 ended in 1944 when its numbers were reduced to about a dozen. Many years of both peacetime and wartime service with up to eight sorties on certain days had finally worn down the inventory and surviving aircraft.

The last Spanish Hs 123 was scrapped in 1953 after an accident in 1952. It had been in service for 13 years, being one of the few pre-series aircraft (Hs 123A-0).

No Hs 123 has survived to date, but maybe we'll eventually find one in some Russian swamp, forest, lake or river, waiting for its recovery and restoration.

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What does the example of the Hs 123 tell us today?

First of all, aircraft cannot be judged by spec sheet and outer concept alone.

 Odd recipes as well as pure chance may lead to great effectiveness.

It does also emphasize the lesson that acoustic effects can have significant battlefield effects.

It reminds us of the importance of low maintenance requirements and high sortie rates.

It also reminds us that the fashion of the decade is not always necessary for a great aircraft. The Hs 123 had neither retractable landing gear nor enclosed cockpit nor a monoplane configuration. These modern characteristics would even have reduced its effectiveness ( retractable landing gear = more accidents and more maintenance, enclosed cockpit = worse field of view, monoplane configuration = worse view to the ground).

S O

Recommended source (German language): "Flugzeug Profile #42"
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