An effort is being made to decrease the noise emitted by engines used by the Israeli air force's unmanned air systems. The need stems from the heavier payloads carried by the aircraft, which demand using their engines in high power mode.

The noise footprint of some Elbit Systems Hermes 450 unmanned air vehicles has been decreased via a re-engining effort which is now under way. New UAS of this type are already equipped with more powerful and quieter engines.

In addition to expanding the range of missions that can be performed due to its reduced noise output, the new R902 (W) "Wankel" technology engine being integrated with the Hermes 450 also enables the tactical UAS to achieve an improved endurance of more than 20h.

The new engine has a larger combustion compartment than its predecessors, enabling the roughly 40kg (88lb) design to deliver more than 70hp (52kW).

Before the re-engining was launched, the air force had tested some types of mufflers on the Hermes 450's engine, but the results were not satisfactory. Examples still being flown with the old engine are currently used for training purposes, and during missions that do not require a "silent approach".

Source: Flight International