An RAF Chinook helicopter struck power lines during a training flight, forcing its pilot to make an emergency landing in a nearby field.
The heavy-lift helicopter, based at RAF Odiham in Hampshire, landed safely in a field near the village of Pembrey in Carmarthenshire, Wales.
An RAF spokesman said the aircraft was on a routine training flight on Tuesday evening when the incident occurred. The Chinook sustained damage, and one crew member received minor injuries due to broken glass.
The Telegraph understands that the Air Accident Investigation Branch has already launched an inquiry.
All military helicopters are able to fly at a very low level in certain parts of the UK. Pilots are expected to keep a good look-out at all times.
Unlike power cables between pylons, which can be up to 200 feet above the ground, domestic power lines are not routinely marked on maps. They are usually only about 30 feet high and are coloured to blend into the countryside.
The Chinook helicopter, the workhorse of the military, was used extensively in Afghanistan. The RAF has three Chinooks and 100 personnel deployed in Mali, west Africa, supporting French forces fighting Islamist extremists.
It is not known if the aircraft involved in the wire strike was in training for the Mali mission. Experts said it could have been destroyed if it had been a few inches lower and the rotor blades had hit the lines.
Local man John Davies, 81, said: "This is not a war zone – it's a very quiet village, nothing exciting usually happens and there's not a lot going on. But all hell broke loose, the electricity went off and we heard a loud noise.
"We all heard it before seeing anything. It was really loud and blaring. The power went off at around 8.30pm and we had an alert saying that they were trying to get it back on. It was only off for around an hour, but everyone was on their doorsteps wondering what was going on."
The helicopter's crew stayed with the aircraft to maintain security until it could be recovered by military transport teams. An RAF mountain rescue team was called in to support the crew, who were put up in hotels overnight.