Airlander 10: Longest aircraft, based at Cardington - ongoing discussion

[whole diary]

[Chris from Nailsea]

From the BBC^» (British Broadcasting Corporation - home page):

Airlander 10: Longest aircraft hit power cable before nosediving


Airlander 10 is understood to have suffered damage on its return to Cardington Airfield

The world's longest aircraft came into contact with "high voltage power cables" before nosediving on landing, an electricity firm has said.

Developers of the Airlander 10 had denied witness reports the airship struck a telegraph pole during its "heavy landing" on Wednesday.

But UK^▸ (United Kingdom) Power Networks said the aircraft had come into contact with one of its power lines.

Hybrid Air Vehicles said a mooring line had been in "contact" with a cable.

The £25m Airlander, which is 302ft (92m) long, was damaged during its second test flight from Cardington Airfield, Bedfordshire.

Its owners initially denied claims from a witness that a line hanging down from the vehicle had hit a telegraph pole about two fields away from its landing site.

But after UK Power Networks said there had been contact, resulting in the loss of power to five customers, the firm released an updated statement. It said: "No damage was caused to the aircraft and this did not contribute to the heavy landing. We are sorry for any inconvenience this may have caused to anyone."


The £25m plane is understood to have sustained damage to its cockpit

Chief Executive of HAV, Stephen McGlennan, told the BBC the aircraft was being fully assessed by a team of experts. "They'll create a plan to repair the front end where there was some damage," he said.

Mr McGlennan also said investors in the Airland project had been "very supportive" since the landing. "They understand a business like this is involved in innovation, innovation is the business of doing things and sometimes when you do things for the first time, sometimes it doesn't work out quite how you'd hoped."

He confirmed two pilots walked away from the landing "without a scratch".


Airlander 10 took off from Cardington Airfield just after 09:00 BST

Mr McGlennan said he did not think the "heavy landing" would cause a "substantial change" to the future schedule of test flights and development. "We are investigating in the way that a normal aerospace company would," he said.

The Air Accidents Investigation Branch confirmed it had been notified about the incident and was investigating, but had not sent a team to the site.

Ooops. 

[stuving]

"Telegraph pole"? Really? Where would you find a telegraph line these days?

OK, it was an 11 kV local power line. But even if it was a much higher voltage, it can hardly have damaged an airship (or whatever that thing is) unless it had another dangling line reaching the ground and both were conductive.

[Chris from Nailsea]

I merely quote what the BBC^» (British Broadcasting Corporation - home page) article says, stuving: however, I happen to agree with your critique. 

I also previously resisted the temptation to point out that the history of 'airships', or whatever you want to call them, flying out of Cardington is somewhat blemished - see the sad story of the R101. 

[Red Squirrel]

...whatever you want to call them

Are you referring to this?

https://www.youtube.com/watch?v=EQyrd1BwusQ

Wind straight to 1.18 if time is pressing.

[TonyK]

Oh, the humanity!

A light aircraft clipping any form of electrical cable at landing speed is a potential disaster. A mooring rope coming into contact with the same at the sort of speed this aircraft would be doing would surely not have any great effect on flight performance, and could be a sign of a problem, rather than the cause. Equally possibly the fact that it made contact could be an indication that the final approach wasn't going to plan for some reason. It  I would not have expected the aircraft to land so close to the perimeter fence either. Time, and the AAIB^▸ (Air Accident Investigation Branch) report - a cracker for the inspector, who will not have dealt with such a craft before - will tell. Thankfully, nobody was hurt, although I dare say quite a few were inconvenienced.

The Airlander 10 is a fascinating concept, and I hope this proves to be nothing but a minor setback. It is financed in part from sales of Iron Maiden albums and tickets, courtesy of singer Bruce Dickinson, who also moonlights as a novelist, pilot, competitive fencer, beer developer, aviation maintenance and training company chairman etc etc.

For those who don't know the difference between a heavy landing and a crash, a heavy landing is a crash where everybody walks away.

[stuving]

Do you realise what it Hybrid Air Vehicles say about it?

"Airlander 10 offers a new type of flight, with ground-breaking capabilities."

Well it can try, but it wasn't the ground that showed signs of being broken was it?

[TonyK]

"Airlander 10 offers a new type of flight, with ground-breaking capabilities."

 

One of my text books for the Private Pilots Licence course makes the point that even big aircraft are fairly inefficient when used for earth moving or tunnel boring, normally leaving only a slight depression surrounded by wreckage.

[broadgage]

I do not foresee large numbers of this type of craft ever being built.

There are many potential applications for small numbers, but they require vast volumes of helium which is expensive, liable to become more expensive, and in fundamentally limited supply.
The helium is not consumed like fuel, but will assuredly slowly leak out and require periodic replenishment. Some economy in helium use could be achieved by use of a hydrogen and helium mixture, with hydrogen present in the greatest proportion that gives a non flammable mixture.

I am not wishing any ill-will on the developers and see a bright future for limited numbers of these or similar craft.

[stuving]

The AAIB^▸ (Air Accident Investigation Branch) have published a report about this accident. They describe this as a "correspondence enquiry", rather than a "field enquiry", and do not provide a list of those. I think that means they will not publish a full report, but have included a shorter one in the March AAIB Bulletin. It is on page 32 (p 36 of the PDF).

The sysnopsis says this:

At the end of a test flight the aircraft could not be secured to its mooring mast because of  a fault in winching apparatus at the mast.  The aircraft departed again while the issue was  investigated.  As it did so the mooring line, which had been secured temporarily, fell free  until it hung to its full length below the aircraft.  The second approach therefore had to be  higher than ideal, which resulted in the aircraft arriving over the landing site at an excessive  height.

The  test  pilot  attempted  to  manoeuvre  the  aircraft  in  order  to  bring  the  mooring  line   within reach of the ground crew, but in so doing, it unexpectedly adopted an exaggerated  nose-down attitude and began to descend.  The pilot was unable to affect a recovery before  the aircraft struck the ground, causing damage to the cabin flight deck area.

... and the key paragraphs are these:

The pilot liaised with the ground team to establish the length of mooring line below the aircraft,  but was incorrectly informed that it was about 50 ft (it was actually 47 m / 155 ft  long).  Once  the problem with the ground equipment had been resolved, the pilot flew a further approach,  although it had to be steeper to ensure the mooring line did not become entangled in trees or  on the perimeter fence.  Despite this precaution, at a height of about 120 ft on the approach,  the line became entangled in wires which crossed the approach path about 200 m outside  the airfield boundary.

Although  the  line  was  freed  from  the  wires,  the  encounter  contributed  to  a  high  final  approach.  Consequently a descent to ground level was not possible in the landing distance  available  and  the  aircraft  arrived  over  the  landing  area  at  about  180  ft.    The  aircraft  was   reluctant to descend naturally and, with no forward airspeed, the pilot had limited control.   He attempted to trim the aircraft nose-down by management of the centre of gravity, so that  the mooring line would come within reach of the ground crew but, with the aircraft at about  10º  nose-down  pitch  angle,  it  suddenly  pitched  further  down  to  about  18º  and  started  to   descend.

The pilot attempted to arrest the descent with the control available and was partly successful  in that the aircraft’s nose-down attitude started to reduce.  However, there was insufficient  height in which to affect a full recovery and the aircraft struck the ground still in an excessive  nose-down  attitude,  causing  structural  damage  to  the  flight  deck  area.    The  accident  occurred 2 hours 12 minutes after un-masting.

As usual in accidents, several factors interact, but you could summarise most of them as "the pilot's understanding didn't match reality". The trailing line was longer than he allowed for, pushing the aircraft up, and when he tried to make it descend its response was not what he intended.

There is some further discussion of why that was in the report, but it comes to no clear conclusion. I presume that as the aircraft is still in its development stage (this was classified as a flight test), further analysis and changes to the design or operating instructions are a matter for its makers.

[TonyK]

The aircraft has been repaired and some modifications made, according to Bedfordshire News. Those mods include a way of retrieving the mooring line should the mast fail again, some sort of airbag device to take the brunt of any future prang, and modifications to allow approaches to be made safely from greater heights. The mooring mast is also being overhauled. Once testing has been done, it should return to the skies.

[Chris from Nailsea]

From the BBC^» (British Broadcasting Corporation - home page):

Airlander 10 'breaks in two' and collapses at Cardington


The airlander collapsed at Cardington Airfield, where it is based

The world's longest aircraft has collapsed to the ground less than 24 hours after a successful test flight.

The Airlander 10 - a combination of a plane and an airship - was seen to "break in two" at an airfield in Bedfordshire, an eyewitness said.

Owner Hybrid Air Vehicles Ltd said it appeared the Airlander broke free from its mooring mast, triggering a safety system which deflates the aircraft.

Two people on the ground suffered minor injuries.

It was not flying and was not due to fly, Hybrid Air Vehicles said.

No one was on board, but a female member of staff suffered minor injuries and was taken to hospital as a precaution. A colleague also sustained minor injuries while dealing with the incident.

"The safety feature is to ensure our aircraft minimises any potential damage to its surroundings in these circumstances," Hybrid Air Vehicles added. "The aircraft is now deflated and secure on the edge of the airfield.  The fuel and helium inside the Airlander have been made safe.  We are testing a brand new type of aircraft and incidents of this nature can occur during this phase of development.  We will assess the cause of the incident and the extent of repairs needed to the aircraft in the next few weeks."


The company that owns the airlander said it was not flying at the time

On Friday, the Airlander took off at 15:11 GMT and landed at 16:18 GMT at Cardington Airfield.  Hybrid Air Vehicles Ltd had said it was now in the "next phase of extended test flights".  It will soon "fly higher, faster, further and longer", the company said.


The airlander is the longest aircraft in the world at 302ft (92m)

In August 2016 the aircraft crash-landed after climbing to an excessive height because its mooring line became caught on power cables.  The 302ft (92m) long aircraft nosedived after the test flight at Cardington. No one was injured.

The Air Accidents Investigation Branch said the line was hanging free after a first landing attempt had failed.


Airlander 10 completed its sixth test flight on Friday

[broadgage]

This is a most unfortunate setback, as much due to the negative PR^▸ (Public Relations) as anything.
Since the aircraft was moored, not manned and not flying at the time it is not indicative of any failure of design.
In fact this incident is more like a conventional aircraft that when parked is turned over or otherwise damaged by hurricane force winds.

Anything that can fly is at somewhat vulnerable to accident, but this sort of craft is relatively low risk due to the modest speeds and inherent buoyancy.

I can see many applications for this sort of aircraft, including-
Delivering heavy or bulky roof top plant directly to urban buildings without use of a crane.
Sightseeing and wildlife observation
Delivering relief supplies after disasters.

I do not however expect large numbers of these to be built due to the cost of helium and the fundamentally limited supplies thereof.

[stuving]

This is a most unfortunate setback, as much due to the negative PR^▸ (Public Relations) as anything.
Since the aircraft was moored, not manned and not flying at the time it is not indicative of any failure of design.
In fact this incident is more like a conventional aircraft that when parked is turned over or otherwise damaged by hurricane force winds.

I'm puzzled you say that, given the quote in the report that explicitly says it was the intended result an "autodestruct" safety feature operating. So it's more like one of those old missile/gunnery target aircraft being flown from the ground* that the pilot loses visual on, flies out of rage limits, and is blown up. Except that in this case most of the bits should be reusable in a rebuild.

* Called a "drone" at the time, in the original use of that term for aircraft, because they just bumbled slowly along like they wanted to be swatted.

[Chris from Nailsea]

* Called a "drone" at the time, in the original use of that term for aircraft, because they just bumbled slowly along like they wanted to be swatted.
[/quote]

cf Class 143.