B Mk III
The Halifax Mk III saw the original Merlin engines replaced by Bristol Hercules radial engines. These provided significantly more power than all but the latest Merlin 22s used in late production Mk II Series 1a aircraft, increasing the maximum speed and altitude of the aircraft. Most importantly, the most economical cruising speed of the Halifax III was 215 mph at 20,000 feet, three thousand feet above the service ceiling of the original Mk I! The radial engines make the Mk III (and similar later models very easy to distinguish from the earlier Merlin powered variants).
The B Mk III was otherwise very similar to the Mk II Series 1a, incorporating all of the modifications that had been made to that model to improve performance. One additional change was the installation of a fully retractable tail wheel.
Defensive firepower was provided by a four gun Boulton Paul Type E turret in the rear, a single Vickers K gun in the nose and a four gun Boulton Paul Type A upper turret, each carrying .303in machine guns.
The Mk III entered service in November 1943 with No. 466 Squadron. Eight more squadrons had received the type by January 1944. Once the Mk III was available in suitable numbers, the Mk II and V were both withdrawn from the bombing offensive.
February 1944 saw the official adoption of a ventral turret for the Halifax, a Preston-Green mounting carrying one .5in Browning machine gun in a dome shaped turret. This was a much more streamlined design than the retractable “dustbin” turrets used earlier in the war, but it could only be carried at the cost of the H2S navigational radar, which was carried in roughly the same place on the aircraft.
The Mk III retained the same 13,000lb bomb load as the Mk I and II, split between four small bomb bays in the wings and the main fuselage bay. The final two wing bomb bays were used to contain extra fuel. If required the main bomb bay could carry an extra 702 gallons of fuel, for a total of 2,688 gallons, although that would result in a dramatic decrease in bomb load.
In total 2,127 Mk IIIs of all types were built, and the type remained in use as a front line bomber for the rest of the war. It was joined by even more powerful Mk VIIs and Mk VIs, but not replaced.
GR Mk III/IIIA
Coastal Command received a small number of Mk IIIs in December 1944, equipping two squadrons with the type before the end of the war (Nos. 502 and 58). The GR Mk III was used to attack enemy shipping. The GR Mk III was little different from the standard bomber, while the Mk IIIa had more specific maritime equipment.
Met Mk III
Five Meteorological squadrons converted to the Mk III during 1945. No. 517 was first, in February, followed by No. 518 in March, No. 520 in April, No. 519 in August and No. 521 in December. The majority of the Meteorological squadrons were disbanded during 1946. The Met Mk III was modified to carry a Met officer and specialised weather monitoring equipment. The Met Mk III was a significant improvement on the Met Mk V, which had suffered from some serious mechanical problems, limiting its range.
A Mk III
The A Mk III entered squadron service with No. 38 Group between D-Day and the attack on Arnhem. This variant was used to tow both Horsa and Hamilcar gliders and drop paratroopers. Thirty B Mk IIIs were converted to this variant, a process that involved removing the dorsal turret, fitting glider towing equipment and adding a paratroop dropping hatch under the aircraft.
C Mk III
The C Mk III was the first cargo conversion of the Halifax. Most military equipment, including the front gun, dorsal turret and the guns from the rear turret were removed. Equipment was fitted inside the fuselage to allow the C Mk III to carry nine stretchers or eight passenger seats. The type entered service with No. 246 Squadron in December 1944.