HMR-161, commanded since 8 August by Lieutenant Colonel John F. Carey, continued its primary mission of evaluating rotary wing aircraft and their methods of employment. One tactical innovation, movement of elements of the 4.5-inch Rocket Battery, was undertaken during August soon after the Bunker Hill battle. With ground-fired rockets, the problem of a tell-tale cloud of dust and brilliant flash of the rockets after each salvo had always plagued the artillerymen. This seldom went unnoticed by the enemy, who often showered the marked area with counterbattery fire. On 19 and 20 August, in Operation RIPPLE, HMR-161 and the rocket battery proved that these two units could successfully shoot and scoot to a new location and fire effectively again without drawing an enemy reprisal. This Marine Corps innovation in air mobility--the first displacement of field artillery under combat conditions--offered a major time-saving advantage. Whereas previously it took approximately a half-hour for rocket launchers to move from their bivouac area to firing position,[249] deployment by helicopter could be made in a matter of minutes, a time factor that could be critical in event of an enemy attempted breakthrough. [249] _Henderson ltr III._ The operation demonstrated that helicopters not only could transport rocket crews with weapons and ammunition to firing areas far more rapidly than conventional wheeled vehicles, but that the rotary craft could airlift these weapons into places inaccessible by road. The nature of the mountainous terrain proved advantageous in that hills and valleys provided defiladed areas for loading and firing the weapons as well as protected routes for helicopter movements. An observation made by pilots for operations in other types of environment, not offering as much cover and concealment, was that the shiny blue paint on their birds would make detection easy in most surroundings and that camouflage paint would lessen the risk from enemy AA. Transport helicopters of HMR-161 continued to augment those of VMO-6 in casualty evacuation and ferrying Marines and other frontline troops. The observation squadron maintained its policy and outstanding record of emergency flights of the wounded under any weather conditions except dense fog (electronic navigational aids still were not available). In August, various mechanical failures developed among the newly received HO5S-1 Sikorsky helicopters. These three-place observation aircraft were underpowered but superior in many flight characteristics to the HTL-4 helicopters then in the squadron. Mechanical difficulties with the newer aircraft increased until it became necessary to ground them late in October until replacement parts became available in the supply system.