The light bomber played an important part in the RAF’s early World War Two operations. Malcolm V Lowe examines the type’s activities during that critical period of the conflict
One of the significant warplanes that entered service with Britain’s RAF during the later 1930s was the Bristol Blenheim. For its time, this light bomber was of advanced monoplane design and all-metal construction and thus represented a major step forward in layout, performance and capability compared with the biplanes that it ultimately replaced.
Developed in the mid-1930s by the Bristol Aeroplane Company from a private venture project for a fast civil transport, the initial example (K7033) of what became the Blenheim first flew on June 25, 1936. There was no actual prototype, production examples having been ordered ‘straight from the drawing board’ under Specification B.28/35. By that time, the project had considerable official backing as a part of Britain’s growing re-armament programme.
The original version for the RAF was the Mk.I (Bristol Type 142M), with its distinctive raked nose profile made up of multiple transparent panels. The first deliveries to a frontline unit were made to 114 Squadron in March 1937 at RAF Wyton, Huntingdonshire. The Mk.I was a dedicated light bomber for the nascent Bomber Command, and was built by Bristol at Filton as well as by Avro and Rootes Securities. Well over 1,000 were completed for RAF service.
With a wingspan of 56ft 4in and a length of 39ft 9in, the Blenheim Mk.I seated a crew of three in its comparatively cramped interior. They comprised the pilot, navigator/bomb aimer or observer, and wireless operator/air gunner. Power for the Mk.I was provided by two Bristol Mercury VIII radial engines, each of 840hp maximum output at 14,000ft. These gave a top speed, according to official RAF figures, of 279mph at 15,000ft. Armament comprised a single .303in machine gun in the Mk.I’s semi-retractable Bristol dorsal fuselage turret, usually a drum-fed Vickers ‘K’ gun. A .303in Browning machine gun was often, but apparently not always mounted in the port wing. Within the lower fuselage bomb-bay, 1,000lb of bombs could be carried, and optional small external racks beneath the fuselage centreline aft of the bomb-bay could carry 40lb fragmentation bombs.
Design work by Bristol of a potential layout for a separate anti-shipping ‘general reconnaissance’ bomber requirement resulted in the improved and more powerful Mk.IV (Type 149) initially under Specification 11/36. This featured a completely redesigned forward fuselage and modified nose glazing leading to an increased length of 42ft 7in. Powered by two Bristol Mercury XV radial engines, each of 920hp, the Mk.IV’s range was some 1,160 miles at 225mph with a top speed slightly less than the Mk.I. Armament and bomb-carrying capacity remained the same, including the dorsal fuselage turret that in combat often proved virtually useless.
The development Mk.IV (a converted Mk.I, K7072) first flew on September 24, 1937. The type officially became a reconnaissance (light) bomber, and as such it initially equipped dedicated recon/bomber units including 53 and 59 Squadrons of the Army Co-Operation Command, the former receiving its first operational examples in January 1939. Subsequently, the Mk.IV became a principal type for Bomber Command as well.
For the reconnaissance task, an F24 aerial camera was mounted above a clear panel in the lower fuselage escape hatch. The observer could also use a hand-held F24. Like the Mk.I, production was performed by Bristol, Avro and Rootes Securities, with just over 3,300 being completed. The type progressively replaced the Mk.I in the home-based light bomber and bomber/reconnaissance units.
Although advanced and highly regarded for its maximum speed at the time of its service entry in March 1937, rapid steps forward in warplanes rendered the Blenheim light bombers especially vulnerable. The appearance of the Messerschmitt Bf 109 as the Luftwaffe’s main fighter, with its excellent performance and comparatively heavy firepower, represented a real threat to the RAF’s rapidly growing Blenheim force.
At Britain’s entry into what became World War Two in September 1939, Bomber Command had 231 light bomber Blenheims on charge; although only 173 of these were declared operational. Nevertheless, this made the Blenheim numerically the most important type in the command’s inventory. Unsurprisingly, Blenheims were among the first RAF warplanes into action during the conflict.
On the day that war was declared on Germany, a Blenheim Mk.IV (N6215), piloted by F/O Andrew McPherson of 139 Squadron, was the first British aircraft to cross the German coast while performing a high-altitude reconnaissance of enemy naval vessels on the Schillig Roads near the port of Wilhelmshaven. The following morning, Blenheims from 107 and 110 Squadrons together with other types flew on the first major RAF bombing mission of the war, to attack the ships discovered the previous day. The raid was a failure, five of the Blenheims being shot down by anti-aircraft fire from the shore and some of the warships, while the largely ineffective GP bombs caused little damage. Further such raids followed, again with little success but growing losses.
The first armed strategic reconnaissance deep into German territory was flown on September 20 by 139 Squadron, but was defeated by cloud cover. The next day, Sqn Ldr Sabine and crew of 110 Squadron in Mk.IV N6212 successfully photographed at low level the railway near the key German city of Osnabrück, returning safely.
Later in the month, a Blenheim of the same unit reached Berlin, probably the first RAF bomber to over-fly the German capital during the war. But these were perilous strategic missions.
Unescorted and often alone, the Blenheims were a prime target for German fighters. The first ‘failed to return’ was on September 28, when 110 Squadron lost P/O Strachan and crew in Mk.IV N6206, shot down by a Bf 109E flown by Leutnant Helmut Heinz, the Staffelführer (junior squadron leader) of 4./JG 77.
The period between the fall of Poland and the commencement of the major German offensive against the Low Countries and France on May 10, 1940 is often described as the ‘Phoney War’. But it was anything but phoney for the RAF aircrews during those months.
Delegated as a part of the RAF’s new Advanced Air Striking Force (AASF), two Blenheim bomber units, 114 and 139 Squadrons deployed to France as the first (advanced) echelon of 2 Group, while 53 and 59 Squadrons with their bomber/reconnaissance Blenheims joined the Air Component of the British Expeditionary Force (BEF) together with the Blenheim bomber units 18 and 57 Squadrons, again stationed in France.
Also committed were several British-based Blenheim units of 2 Group as a part of AASF’s second echelon, including 107 Squadron at RAF Wattisham led by the colourful Wg Cdr Basil Embry.
Unfortunately, the lumbering Blenheims on their long-range reconnaissance flights over Germany soon became a prime target for Luftwaffe pilots. On October 30, 1939, when the Phoney War was becoming well established, British reconnaissance aircraft operations were becoming a daily occurrence. Writing later for Der Adler (the Luftwaffe’s wartime magazine), German fighter ace Werner Mölders described an encounter with a Blenheim Mk.I: “I took off with the Gruppenschwarm and three Schwärme of the 9th Staffel [of JG 53] for a patrol to counter enemy reconnaissance aircraft in the Bitburg-Merzig area. At 11.12 hours I noticed flak activity near Trier. I approached to within 50 metres of the enemy aircraft without being seen, and saw the British roundel very clearly.
“I opened fire and closed to the shortest possible range without any return fire from the rear gunner, and the left engine gave out a thick white cloud of smoke. It changed very quickly to black. When I pulled up beside it, the aircraft was totally on fire. I observed a parachute, but it seemed to be alight.”
The Blenheim that Mölders had shot down was L6694 of 18 Squadron, operating from the French airfield at Metz, east of Paris; Flt Lt Dilnot and his crew were killed.
On May 10, 1940, the expected German offensive in the west finally started, but its location, objectives and sheer weight of numbers took the Allies by surprise. The RAF’s France-based Blenheims and Fairey Battles were involved from that first day onwards, with disastrous consequences. The initial Blenheim sortie was a reconnaissance from Poix airfield in France early on May 10 by P/O Massey and his crew in Mk.IV L9332 of 53 Squadron. The first Blenheim bomber loss was from 18 Squadron (Mk.IV L9255) on an armed reconnaissance from Méharicourt (Rosières) airfield. Subsequently, sorties were flown from French air bases and by 2 Group Blenheim bombers based in Britain, the Blenheims having the range to achieve this. Unfortunately, 40 Squadron from RAF Wyton lost three aircraft on its first operation, during the fighting for Ypenburg airfield.
For the two Blenheim units of the France-based 2 Group, first echelon of AASF, the German invasion was a catastrophe. On May 11, while preparing for a bombing mission, 114 Squadron at Vraux (Condé-sur-Marne) airstrip had been caught on the ground by the Dornier Do 17Z-equipped 4th Staffel of KG 2 and had lost six aircraft destroyed with virtually all its remaining Blenheims damaged.
Located at Plivot landing ground near Épernay in the Marne, 139 Squadron mounted a bombing raid against key bridges at Maastricht in the Netherlands over the River Meuse early on May 12. Nine aircraft were sent, one returning early. Seven of the eight attacking force were duly shot down, the one remaining aircraft returning badly damaged. May 12 was a disastrous day all round for the RAF, and the Blenheims suffered particularly badly, 20 being shot down from several France and Britain-based squadrons including some Blenheim fighters that simply could not cope with the Luftwaffe’s Bf 109E.
Further disaster followed on May 14, and in the ensuing weeks the brave aircrews of the Blenheim and Fairey Battle squadrons continued the fight against the steadily advancing Germans.
But not all the losses were to enemy action. On May 16, a Blenheim of 53 Squadron was mistakenly shot down by an RAF Hurricane, followed by a second loss that day when another of the unit’s aircraft, having been damaged by a Hurricane, was then brought down by Allied anti-aircraft gunners at Amiens-Glisy airfield.
The sacrifice of so many of these airmen could only at best slow the German advance, and eventually some of the units were moved to western France and reduced to being virtually non-operational. All the AASF and Air Component squadrons were pulled out of France before the end of the fighting and the French capitulation of June 1940, some leaving behind virtually all their equipment.
Blenheims were fully involved in the Dunkirk evacuation of late May/early June 1940, bombing German land forces that attempted to advance on the retreating British and French armies. There too, losses were heavy.
The Blenheim’s inadequate rearwards defensive armament was a cause of much concern, and throughout 1940 various schemes were developed to devise a solution. Eventually, a Bristol Type IV turret was standardised, mounting two belt-fed .303in Browning machine guns to replace the totally inadequate single and later twin Vickers ‘K’ gun armament.
A rearwards-firing installation beneath the nose was also fitted to some aircraft, but proved virtually useless. Even with the addition of better self-sealing for fuel tanks, Blenheims were perennially vulnerable to fighter attacks from the rear.
Generally regarded by modern historians as having commenced on July 10, 1940, the Battle of Britain followed almost straight after the defeat of France. There was little time for the 2 Group Blenheim units – now all Britain-based – to regroup before the new campaign opened.
It is often forgotten that the Blenheim played a key role during the Battle of Britain. With bravery equal to the Battle of France operations, Blenheim aircrews continued their reconnaissance role over occupied France. But now they were looking for – and when possible bombing – concentrations of assembled shipping that would be used to launch a seaborne invasion of southern England. In addition, operations were flown against any other suitable German targets, including airfields that only weeks earlier had been used by the Blenheims.
This new area of the war has been described by historians as the Channel Front, and once more the main adversaries of the Blenheims were Bf 109E fighters that took a steady toll of the British aircraft.
Nevertheless, the Blenheims’ frequent excursions over the German-held Channel ports, and potential targets further inland, tied up Luftwaffe fighters that otherwise would have been operating against southern England. The successful conclusion of the Battle of Britain in the Allies’ favour later in 1940 allowed the RAF – tentatively at first – to begin taking the fight to the enemy over occupied Europe. Once more right to the fore, the Blenheim squadrons played a vital part in the early stages of what became a growing campaign against tactical targets in France and the Low Countries from 1941 onwards.
But the Blenheims with their comparatively long range were soon involved in a new campaign against strategic targets within Germany itself.
Operating in daylight and often at low level, these missions were as costly as the sometimes disastrous operations of 1940.
On January 10, 1941, Blenheim Mk.IVs of 114 Squadron escorted by several squadrons of fighters flew the RAF’s first ‘Circus’ tactical bombing operation, targeting the Forêt de Guînes in occupied France. From then onwards the Blenheims were fully committed to this new phase of operations, but again the cost in men and machines was heavy. In particular, a series of high-profile but very costly attacks were made against high-value targets. These were much heralded in the British Press, but they were often carried out with planning that went wrong and rendezvous with escorting RAF fighters that were sometimes missed, leaving the Blenheims vulnerable to defending fighters.
One of the most high-profile – and costly – raids of the Blenheim’s operational career was the August 12, 1941 attack on two power stations in the Cologne area.
Although within range of the comparatively long-legged Blenheims, this was too far for any RAF fighters to provide escort. In any case, the latter would have had no effect against anti-aircraft fire, which was heavy around such high-value targets.
The incredible gallantry of Blenheim crews throughout the type’s tempestuous combat career cannot be underestimated. Employing a warplane that was clearly outclassed in aerial combat, and performing perilous low level daylight raids in the face of heavy anti-aircraft fire, resulted in a very high loss rate. Many Blenheim crew members were decorated for their actions during the three years, approximately, that the type flew in combat over north-west Europe. This included the award of a Victoria Cross to Acting Wg Cdr Hughie Idwal Edwards of 105 Squadron for his leadership of a low level daylight raid against the heavily defended north German port of Bremen on July 4, 1941. He was the first Australian airman to be awarded the VC in World War Two.
Sadly, some of these missions were of little overall value to the Allied war effort. Two attacks in 1941 on the Rotterdam port/docks area in the occupied Netherlands on July 16 and August 28 resulted in heavy losses to the Blenheims, leading Winston Churchill to question the efficacy of such operations.
But one of the most dangerous undertakings of the courageous Blenheim aircrews was the 1941 anti-shipping campaign. Carried out against military and merchant shipping at sea, the Blenheims proved highly vulnerable to well-trained and seasoned anti-aircraft gunners. Several Blenheim squadrons were tasked with this undertaking. The battle-hardened 53 Squadron, for example, had started as an Army Co-operation Command unit when it first received the Blenheim in early 1939, had then fought in France, and in June 1940 was transferred to Coastal Command joining several other Blenheim units. The attacks against German shipping proved so costly that the campaign had to be temporarily halted later in 1941.
Some night operations were flown later in the Blenheim Mk.IV’s career, including participation in the first of the ‘Thousand Bomber’ raids during late May 1942. The final Bomber Command Blenheim sortie is generally considered to have been performed by 18 Squadron on the night of August 17-18, 1942.
The Blenheim’s time as a frontline warplane over north-west Europe eventually drew to a close. The type was replaced by a number of newcomers, notably the superlative de Havilland Mosquito. Faster, more heavily armed, and using tactics gained the hard way during the Blenheim’s combat career, the Mosquito grew into one of the RAF’s most successful multi-role aircraft. The first Blenheim unit to transition on to the ‘Mossie’ was 105 Squadron during late 1941/early 1942.
In the anti-shipping role, further Bristol products, the Beaufort and then the Beaufighter with its hard-hitting armament, very successfully took over from where the Blenheims left off.
In May 1943, 2 Group, which had relied so heavily on the Blenheim in early war years, was transitioned out of Bomber Command altogether and became the basis of the later outstandingly successful 2nd Tactical Air Force. By that time, the Blenheims were gone from the front line over north-west Europe.
