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Ground incident leaves Airlander deflated

Hybrid Air Vehicles (HAV) is staying silent on the impact of an 18 November mishap in which its Airlander experimental airship collapsed during a ground incident at the UK firm's base at Cardington airfield.

HAV says it will assess the extent of repairs required to the airship over the "next few weeks" after a safety feature caused the Airlander to automatically deflate when the lighter-than-air vehicle "broke free from its mooring mast".

The 92m (300ft)-long, helium-filled airship is equipped with a system that is "designed to rip open the hull" if such an event occurs, in order to "minimise any potential damage".

"We are testing a brand-new type of aircraft and incidents of this nature can occur during this phase of development," the company states.

However, HAV declines to provide further detail to FlightGlobal about the extent of damage to the vehicle and any potential impact on the programme.

HAV says the aircraft "was not flying at the time of the incident" and was secured "on the edge of the airfield". Two staff members sustained minor injuries, it adds.

Why the airship broke free from its mast has yet to be determined, the manufacturer says.

Weather information for Luton airport – which is approximately 28km (17 miles) south of Cardington – indicated wind speeds up to 11kt (20km/h) on 18 November.

The latest incident is the second major setback for the programme. In August 2016, the airship crash-landed during its second flight. Following repair and modification work, the Airlander resumed test flights in May, completing a total of four sorties this year.

In fact, the 18 November accident took place a day after the first flight of a "second phase" of test activity, which promised "more intense" flight trials, HAV says.

The manufacturer says the European Aviation Safety Agency had validated flight-test data and agreed that "we are safe to fly in a wider range of conditions".

Under an expanded permission, dubbed "Airworthiness Release 2a", the aircraft's operating envelope was opened up to an altitude of 7,000ft, airspeed of 50kt, and to fly up to 75nm (138km) away from Cardington. HAV notes the permit additionally enabled the team to undertake "display and demonstration activity".

Several "modifications and upgrades" were introduced ahead of the expanded flight-test campaign, including a fairing between the hull and "mission module" to reduce drag at higher speeds, the manufacturer says.

If the images of the deflated Airlander look bad, the outcome could have been worse: in 2015, an experimental, tethered surveillance balloon on test for the US Army – the Joint Land Attack Cruise Missile Defence System (JLENS) – broke free of its moorings at the Aberdeen Proving Ground in Maryland.

Not equipped with an automatic deflation mechanism, the balloon travelled across Pennsylvania for about 3h, dragging its tether over powerlines and causing at least $300,000 of damage.

It eventually ended up in trees in a sparsely populated area of Pennsylvania, and the project was cancelled.

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