sentences:  An evaporative cooling system was used on the V1, with the remaining prototypes receiving a semi-retractable radiator directly below the engine to augment cooling during take-off and climb.Only eight prototypes were completed and the aircraft did not see production, mainly because of the shortages of DB 601 "component" engines to construct the DB 606 "power systems" they formed.The first two prototypes were built as land planes, with retractable landing gear.