Henschel Hs-293 Glidebomb
The Henschel Hs-293 family of glidebombs was the first to be used in combat and the first to enter advanced development. Henschel's mainstay in this development effort was the outstanding Prof. Dr. Herbert A. Wagner, a former Junkers engineer hired in 1940, who took over leadership of a development team comprising Reinhard Lahde, Otto Bohlmann, Wilfried Hell, Josef Schwarzmann, Dr. Hinrici, further supported in guidance system development by Theodor Sturm of the Stassfurter Rundfunk Gessellschaft. This team of engineers and scientists can take credit for the first operational guided bomb.
Henschel's team started development in 1939 using a glidebomb concept devised by in 1937 by Gustav Schwarz Propellerwerke. This concept evolved through the Hs-293V-1 and Hs-293V-2/FZ21 to the Hs-293V-3, tested in mid 1940. The unpowered Hs-293V-3 lacked the terminal velocity to punch through the skin of a warship, the intended target type for these weapons, and this led to the decision to add a rocket booster to increase speed and range.
The Hs-293A-0 was the preproduction configuration which combined the basic airframe and guidance package with a Walter HWK-109-507B rocket booster pack. This rocket motor used T-Stoff (hydrogen peroxide) and Z-Stoff (aqueous solution of calcium or potassium permanganate), using compressed air bottles to drive the hypergolic propellant mix into a reaction chamber. It delivered an initial 1,320 lbf (600 kp) of thrust, declining to 800 lbf (400 kp) before fuel exhaustion 12 seconds later.
The basic warhead for this weapon was the Luftwaffe's standard 500 kg SC-500 (Sprengbombe Cylindrisch) thin walled bomb casing, containing 650 lb of Trialen 105 explosive (15% RDX, 70% TNT, 15% aluminum powder), with an impact fuse. This choice of warhead was later shown to be a major limitation with best effect against small surface warships and transports.
The airframe was a simple mid wing monoplane configuration with slight anhedral, and a booster pack mounted on ventral brackets.
Dornier Do-217K-3 armed with Hs-293A glidebomb
Heinkel He-111H performing a trial drop of the Hs-293A
The guidance package was built around a Horn gyroscope, OPTA Radio control signal decoder, a Strassburg FuG-230b/E230 radio command link receiver, all powered by DEAG one shot batteries, and used to drive Hornasser solenoid control actuators for the ailerons and elevators.
In operation, the launch aircraft would send commands using a FuG-203 Kehl III radio transmitter, which received by the FuG-230b would be demodulated to generate steering commands for the control actuators. Eighteen preset frequencies in the 48-50 MHz bands were available. This was the first air launched Command to Line Of Sight (CLOS) guidance system ever used. A red coloured flare on the tail of the weapon was used to cue the operator when steering the weapon.
Performance claims include a glide range of 11 km for a 3,300 ft AGL release, and speeds between 235 and 486 KTAS.
The Hs-293A-0 entered production in November 1941, followed by the more refined Hs-293A-1 in January, 1942. Trials were conducted in 1941 using a prototype Heinkel He 177A-0, followed by a pair of He 177A-1 Greif aircraft.
The Hs-293 was operationally deployed with KampfGeschwader 100 (KG 100) in the Mediterranean and KampfGeschwader 40 (KG 40) in France, for antishipping strike operations.
The first documented combat use was on the 25th August, 1943, when KG 40 Do-217 bombers attacked a Royal Navy U-boot patrol in the Bay of Biscay, damaging the HMS Landguard and Bideford. Two days later a strike by 18 KG 40 Do-217s sank the corvette HMS Egret, killing 194 sailors, making this the first known sinking of a ship by a guided bomb.
In 1944, after the D-Day landings, Do-217 aircraft used the Hs-293 to attack bridges at River See and River Selume on the Cherbourg penisula, in an attempt to stall the Allied advance from the bridgehead.
Other claimed casualties for the Hs-293 include the frigate HMS Jervis damaged in January, 1944, the Liberty ship Elihu Hale sunk, LCT-35 sunk, the destroyer HMS Intrepid sunk in the Aegean, September, 1943, the destroyer HMS Inglefield sunk in February, 1944, the destroyer HMS Boadicea sunk in June, 1944, the destroyer RHS Vasillisa Olga, sunk in September, 1943. The weapon is credited with a total of 400,000 tonnes of sunk shipping [click for more ....].
Luftwaffe activity in Italy led to the compromising of the Hs-293A series when Allied forces captured intact crated Fritz-X and Hs-293 hardware at Foggia airfield, and were able to devise a radio command link jammer, rapidly built and deployed to fleet units.
The Hs-293B was devised as a counter to FuG-230b jamming, and used a wire guidance scheme, unwinding up to 12 kilometres of cable from a spool attached to the tail of the weapon. A FuG-207 Dortmund transmitter and FuGz-237 Duisburg receiver replaced the Kehl III/FuG-230b radio link. Source disagree on the number of Hs-293B built and used in combat.
A small number of the Hs-293C were built, equipped to attack ships below the waterline. This unsuccessful design evolved into the Hs-294 air delivered torpedo system, conceptually not unlike Australia's Ikara. While Greman sources claim up to 160 variants of the Hs-294 were built, none were reported used.
TV guided Hs-293D
The Hs-293D was an important milestone since it introduced a nose mounted television camera and radio uplink to the launch aircraft, the aim being for the bomber to attack through an overcast. This variant was distinctive due to the use of a tail mounted Yagi array for the video uplink, and a reshaped nose for the camera aperture. The first successful trials were conducted in August, 1944, using Seedorf 3 and Tonne 4a guidance equipment. German sources claim 255 were built, and at least one source claims a Royal Navy warship was hit by a Hs-293D.
The Hs-293E was an improved C-model, or which only 18 were built. The Hs-293F, with a delta wing, was abandoned in late 1943. The Hs-293G, built for steep dive attacks with a terminal homing seeker, never finished trials.
The Hs-293H was a attempt to adapt the Hs-293A as an air to air missile for attacking bomber formations. It was equipped with a pair of HWK-109-542 or Schmidding 109-513 rocket motors, an acoustic promiximity fuse, and a new guidance package. Eight prototypes were built.
The final Hs-293I was built around a larger warhead, but never entered production.
The novelty and complexity of the Hs-293 were reflected in frequent hardware failures and manufacturing faults, resulting in what German sources claim was a dud rate of 28% per launch for KG 40 and 25% for KG 100, against a successful hit rate of 31% for KG 40 and 55% for KG 100. The Hs-293 was carried by the Fw-200 Condor, He-177 Greif, He-111H and Do-217K, with most installations including an exhaust duct to heat the rocket motor before release.
In perspective, the Hs-293 proved to be useful weapon, but dilution of development effort into too many variants hampered the refinement of the basic models.
Trial drop of a Ruhrstahl AG SD-1400X Fritz-X glidebomb