The Israeli air force is to use its Sikorsky CH-53 Yas'urs for communications relay and electronic warfare missions from unusually high altitudes for a helicopter.

The air force has completed an initial series of "high-altitude" CH-53 flights, reaching 18,000ft (5,500m). Previously, the Israeli air force restricted its CH-53s to 10,000ft. The test machine was equipped with an oxygen system for the flights.

One of the test pilots says the high-altitude flight required special efforts to overcome control and transmission problems.

A second series of high-altitude flights is planned in the next few months to evaluate the effect of high temperature as well as altitude on the flight envelope.

The air force will not say why it needs to operate the CH-53 at higher altitudes, except that it will allow coverage of larger areas. It is understood the extra altitude is needed for special relay and EW missions.

The air force plans to extend the CH-53's operational life to 2020. The fleet was upgraded in the 1990s to CH-53-2000 configuration, including new avionics. The latest upgrade work is concentrating on problems with the dynamic system.

Meanwhile, the Israeli air force is designing a belly container for its Boeing AH-64D Apache Longbow attack helicopters which will carry communications and EW systems for special missions.

The air force flight-test centre has designed a glassfibre prototype container that will shortly be tested to evaluate its effect on the helicopter's stability and the effect of the 30mm gun on the housing. Before settling on the new pod, the air force had considered placing the systems in the Apache's aft end.

Boeing delivered the first Israeli air force-bound AH-64D to the US Army last month. This will be used to test Israeli-unique systems. Series delivery of Apache Longbows to Israel is to begin in 2005.

Source: Flight International