From 'Super Marauder' to Martin XB-33B Marianas
The production model B-33B-FO-1 Marianas reflected more focus on combat roles. Exact armament options remained in flux. To address on-going c/g issues, the prototype's Sperry ball turret was abandoned. The Martin A-14 dorsal turret was moved forward to improve balance - which, in turn dictated a re-arrangement of the crew compartment behind the cockpit. To better accommodate the fittings of the turret, the radio operator's position was turned sideways. The navigation positions was removed to the rear fuselage - an astro dome being placed directly in front of the fin extension for the navigator's use. Aircraft were delivered from the Ford factory at Willow Run, MI, with all ventral turret fittings removed and the ball turret opening plated over.
While being fitted out for overseas service, many B-33B-FO-1s received a distinct, low-profile belly position. This hand-held gun mount was based upon a 5th Air Force 'mod' for Liberators. Twin .50-cals were housed in a shallow plexiglass 'dish', rotating 360° around a central support post. While this 5th AF innovation had nowhere near the original ball turrets range of action, it was light, easy to maintain, and quite simple to install. Although not universal, the '5th AF' belly mount became a fairly common modifications for B-33B-FO-1s.
Top An Australian B-33B-FO-1 Marianas of the RAAF's No.201 Flight - an electronic intelligence unit. Adapted for its Antepodian specialist role by No. 1 Aircraft Performance Unit, [1] this aircraft is festooned with antennae of various kinds. The '5th AF' belly mount can be seen as well as a H2X 'Mickey' blind-bombing radar antenna under the nose. [2] No.201 Flight had formed on Liberators but these were quickly traded for the Marianas (special duties No. 200 Flight was likewise re-equipped).
This particular aircraft - originally a TB-33B - served briefly with No 7 Operational Training Unit at Tocumwal, NSW, before being transferred to No.1 ADU for conversion. Markings are essentially the same as the Flight's previous Liberators. A white recognition panel covers the uppermost fin and rudder although the significance of the black 'X' is unknown. NX+B has been dubbed 'Meddlesome Maggie', a name inherited from Liberator NX+R. Note the serial, A76-413. The Marianas received a new RAAF type code ('76') but serial numbers continued from the Liberator sequence - the last B-24M being 72-405, the first B-33B becoming 76-406.
Pattern Finally Settled ... But Perhaps Too Late?
The B-33B-FO-2 could be considered the definitive Marianas - it was certainly the last down the Ford production line. Engines changed from Wright R-2600-29As to R-2600-35s but power remained the same. The belly gun opening was eliminated altogether - being replaced by Marauder-style rear fuselage gun hatches. The main undercarriage was also strengthened. Otherwise, the final production model B-33B-FO-2 was essentially similar to the original B-33B-FO-1 Marianas.
Along with the twists and turns on B-33B armament choices, the USAAF's crewing concept also shifted. It was originally intended that the Marianas would be manned by ETO B-24 crew members with insufficient 'points' to qualify for a return stateside and demobilization. However, it was decided to redirect B-24 crews to the China-Burma-India Theater where Liberators were still widely used. The B-33Bs would, instead, be manned by former B-26 Marauder medium bomber crews. [3] Pilots were familiarized with 4-engine operation on B-24s before going on for brief type conversion on the handful of TB-33B-FO-1 trainer conversions.
Bottom 'A Bumpy Ride' - a B-33B-FO-2 Marianas of the USAAF's 427th Bomb Squadron, 303d Bomb Group, while based at San Marcelino Airfield on Luzon in the liberated Philippines. Joining Fifth Air Force squadrons, the 427th BS aircraft were used as part of Operation Pastel Three. Encouraging Japanese belief in a fictitious Allied landing on China's mainland was the chief goal of this deception campaign. To that end, aerial operations were centred on the Chusan-Shanghai area, consisting of leafleting, 'supply drops' (to non-existent agents), and bombing runs. [4]
From Philippines bases, these Chusan-Shanghai missions of 2,400 miles or so averaged just under ten hours duration - very tiring for the aircrews but well within the range capabilities of the B-33Bs. Returning from such a mission on 24 Feb 1946, 'A Bumpy Ride' was caught by Japanese flak over Formosa. She went down south of Ishigakijima but the crew were rescued by a US submarine, the USS Trumpetfish (SS-425) on its first operational cruise.
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[1] No.1 Aircraft Depot's Special Duties and Performance Flight until December 1943, No.1 ADU evolved into the Aircraft Research and Development Unit (ARDU) after the war ended.
[2] Generally, the B-33B-FO-1 was 'fitted for but not equipped with' the H2X radar. The RAAF specifically requested No.201 Flight's Marianas receive the 'Mickey' sets.
[3] Most surviving USAAF B-26 Marauder were being converted to AT-23 trainer/target tug status or passed on to allies as bombers or patrol aircraft.
[4] Aircraft assigned to leafleting or 'supply drops' missions still carried a minimal bomb load. This was for targets of opportunity - including any Japanese shipping found in the South China Sea or Formosan waters.