Crash attenuation system for aircraft

A crash attenuation system for an aircraft, the system comprising:

• an airbag carried by the aircraft and inflatable to a position exterior of the aircraft, the airbag having at least one vent for releasing gas from the interior of the airbag for crash attenuation;
• a first gas source in fluid communication with the interior of the airbag for inflating the airbag to the position exterior of the aircraft with gas provided by the first gas source;
• a vent valve for controlling a flow of gas through each of the at least one vent, each vent valve being selectively configurable between an open state, in which gas can pass through the associated vent from the interior of the airbag, and a closed state, in which gas is retained within the interior of the airbag;
• a second gas source in fluid communication with the interior of the airbag for at least partially re-inflating the airbag with gas provided by the second gas source after venting of gas through the at least one vent;
• and
• a water-detection system for detecting the presence of water.