The first H2X-equipped B-17's arrived in England in early October 1943, and were first used in combat on 3 November 1943 when the USAAF VIII Bomber Command attacked the port of Wilhelmshaven.
Those missions where bombing was done by H2X were called "Pathfinder missions" and the crews were called "Pathfinder crews", after RAF practice of using highly trained Pathfinder crews to go in before the main bomber stream and identify and mark the target with flares.
American practice used their Pathfinder crews as lead bombers, with radar equipped aircraft being followed by formations of radar-less bombers, which would all drop their loads when the lead bomber did.
The ventral hemispherical radome for the H2X's rotating dish antenna replaced the ball turret on B-17 Flying Fortress Pathfinders, with the electronics cabinets for the "Mickey set" being installed in the radio room just aft of the bomb bay.

The H2X on later B-24 Liberators also replaced the ball turret, being made retractable as the ball turret was for landing on the Liberator.
The operators panel was installed on the flight deck behind the co-pilot (where the radio operator's normal position was).
In combat areas the Mickey operator directed the pilot on headings to be taken, and on the bomb run directed the airplane in coordination with the bombardier.
The first use of Mickey was against Ploiești on April 5, 1944.
The first H2X-equipped B-17's arrived in England in early October 1943, and were first used in combat on 3 November 1943 when the USAAF VIII Bomber Command attacked the port of Wilhelmshaven. Those missions where bombing was done by H2X were called "Pathfinder missions" and the crews were called "Pathfinder crews", after RAF practice of using highly trained Pathfinder crews to go in before the main bomber stream and identify and mark the target with flares. American practice used their Pathfinder crews as lead bombers, with radar equipped aircraft being followed by formations of radar-less bombers, which would all drop their loads when the lead bomber did. The ventral hemispherical radome for the H2X's rotating dish antenna replaced the ball turret on B-17 Flying Fortress Pathfinders, with the electronics cabinets for the "Mickey set" being installed in the radio room just aft of the bomb bay.
The H2X on later B-24 Liberators also replaced the ball turret, being made retractable as the ball turret was for landing on the Liberator. The operators panel was installed on the flight deck behind the co-pilot (where the radio operator's normal position was). In combat areas the Mickey operator directed the pilot on headings to be taken, and on the bomb run directed the airplane in coordination with the bombardier. The first use of Mickey was against Ploiești on April 5, 1944.
H2X