Last-minute concerns about their vulnerability to ground fire meant that they were replaced in this role by French paratroops who conducted a daring low-level drop on 5 November, securing one of the two bridges. The helicopters, including types such as the H-21, the Alouette II, the Sikorsky H-19 and Sikorsky H-34, together aggregated over 190,000 flying hours in Algeria.The rotor is unpowered and rotates freely in the airflow as the craft travels forward, so the craft needs a conventional powerplant.Subsequently, on May 10, 1928, Second Lieutenant César Álvarez War Palmas Las voluntarily jumped from a height of 3,000 meters, becoming the first military parachutist. Then on May 16, 1928, Major Fernando Melgar Conde and Sergeant 1st. Jose Pineda Castro, jumped from the famous Las Palmas. The speed at which the abseiler descends is controlled by applying greater or lesser force on the rope below the device or altering the angle at which the rope exits
