Engineering news
The 92m-long aircraft nosedived after a test flight at RAF Cardington airfield, Bedfordshire, on 24 August. No-one was injured in the accident.
Hybrid Air Vehicles (HAV), Airlander's developer, said at the time of the incident that the aircraft had "experienced a heavy landing and the front of the flight deck sustained some damage".
In its report into the incident, the Air Accidents Investigation Branch (AAIB) said the line was hanging free after a first landing attempt had failed.
The AAIB stated that ground crew had told Airlander's pilot the mooring line was about 15m-long, but it was in fact 47m-long. The rope became entangled in power lines near the airfield as the pilot attempted a second landing.
"The encounter contributed to a high final approach," the investigators said.
The report stated that the pilot attempted to manoeuvre the aircraft to a nose-down position to bring its mooring line within reach of the ground crew but it "suddenly pitched further down to about 18 degrees and started to descend”.
"There was insufficient height in which to affect a full recovery and the aircraft struck the ground," the investigators added.
Hybrid Air Vehicles said this week that structural damage sustained on the flight deck has been repaired and a number of improvements have been implemented since the accident last year.
A key visible change is the addition of an auxiliary land system which enables the aircraft to land at a greater range of altitude. This has been fitted forward of the main landing gear and is a pressurised air cushion which contacts the ground during a landing.
The company said it has also made a series of improvements to its ground systems to reduce the chance of an equipment failure such as the problem with the mooring mast winch that triggered the incident in August last year.
“We are also modifying the aircraft to make sure that if the mooring line were ever to hang down from the aircraft again, as it did that day, it can be recovered so that it does not interfere with the approach and landing of the aircraft,” the company said in a statement.
Hybrid Air Vehicles, which was founded in 2007, said a rigorous testing and training programme has started to prepare for Airlander taking to the skies again. “Over this period the whole focus of the team has been to improve the way we work and the way we operate the aircraft so that our next stage of flying achieves all of our objectives. Our work in this has been guided by our investigations, which were conducted and reviewed in line with the exhaustive standards that are the norm across the aerospace industry,” said operations director Tom Grundy.
First developed for the US government as a long-endurance surveillance aircraft, the British firm launched a campaign to return the craft to the sky after it fell foul of defence cutbacks.