Certainly looks like a stall...
...but the video only shows the very end of the action.
I found a longer video:
https://www.youtube.com/watch?v=Z5Slv6E5ntQ
Clearly it's not a true stall. Seems like they lost control for some other reason.
Watch the world's biggest 'flying bum' go arse over tit in a crash
The Airlander 10 hybrid – part airplane and part airship – has had a bumpy touchdown after piling into its landing site nose first. The 92-meter (302-foot) aircraft gets 60 per cent of its lift from the helium that fills its two massive airbags, which have earned the aircraft its nickname of the Flying Bum, although the …
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Thursday 25th August 2016 16:33 GMT Anonymous Coward
Re: Certainly looks like a stall...
I suspect that the pilot may not have appreciated just how severe the nose-down attitude was
Are you sure? Got no airship piloting experience to draw on; but I would have thought that being strapped into a shed on the bottom of that thing would give you an immensely detailed appreciation of angles. Aside from anything else, he would have started spilling tea once it went past about 15 degrees off horizontal.
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Thursday 25th August 2016 10:00 GMT Anonymous Coward
Re: Certainly looks like a stall...
It doesn't really look like a stall at all - in the longer vid, linked above, the Airlander is already in a nose-down attitude before the final pitch-down. Also, if you full-screen the higher res video in the Reg article, you can see a grounding line hanging below the rear of the control cabin but it doesn't appear to get snagged; it just seems to drop vertically until just before touch-down.
What appears to happen is that the front ducted fans continue to be vectored backwards along the axis of the craft while it's descending, driving it downwards. Then, when it's clear that the attitude is too extreme, the fans start to be vectored downwards but not by nearly enough - they are still largely pointing backwards along the axis and continue driving the craft downwards.
I doubt that the fans are that restricted in their vectoring limits so I suspect that the pilot may not have appreciated just how severe the nose-down attitude was and so just didn't vector the fans enough: Controlled Flight into Terrain.
I'll be interested to read the AAIB report when it's out.
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Thursday 25th August 2016 17:50 GMT fnj
Re: Certainly looks like a stall...
@LeeE:
I doubt that the fans are that restricted in their vectoring limits
I believe (and this info is very difficult to pin down) the forward propulsors are limited in swivelling to +-20 degrees. But additional thrust vectoring is available through using the movable vanes in the propwash. It's very difficult to impossible to judge the final vector direction by inspection.
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Friday 26th August 2016 17:12 GMT Anonymous Coward
Re: Certainly looks like a stall...
"I believe (and this info is very difficult to pin down) the forward propulsors are limited in swivelling to +-20 degrees."
I don't know what the vectoring limits are but as the Airlander is designed to operate in (slightly) heavier-than-air mode I'd be very surprised if the fans can't be vectored directly downwards to help compensate for varying loads whilst taking-off and landing. In fact, if you're going to fit vectoring fans on a craft of this type, I'd be a bit surprised if they can't be vectored in any direction, especially directly forwards, to aid braking and positioning.
If you're going to fit vectoring fans I just can't see any good reason for limiting the vector range at all unless the designers only stressed the fan mountings for that +/- 20 deg range, which would seem to be either a bit of an oversight or an indication of marginal performance (in some respect) that could only be addressed by limiting the stress capability of the fan mountings.
If the fans are limited to just +/- 20 deg, I'd be very curious to know exactly why because given the entire context i.e. not just the type and design of the craft, but also its originating customer and intended purpose (military), those limits just don't seem to make much sense.
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Thursday 25th August 2016 06:41 GMT werdsmith
Re: Certainly looks like a stall...
I don't think you can stall a wing at near zero airspeed, though maybe they were into wind and the breeze dropped suddenly. Or a breeze picked up and aerodynamically caused the pitch down. I could imagine that being such a big area, once the nose is pitched down into wind then they would be fighting a very large aerodynamic force trying to force it down more.
It looked like the rotating engine pods at the front weren't capable of turning directing much downward thrust that could have helped level the thing.
Sitting in that cockpit would have felt like they were going in at a much steeper angle than it looked from outside. At least, though, all they need to do to repair is to bolt another shed on the bottom. Maybe attach a couple of straw bales to it next time though.
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Thursday 25th August 2016 07:53 GMT SkippyBing
Re: Certainly looks like a stall...
'I don't think you can stall a wing at near zero airspeed'
Pedantically wings stall at an angle of attack, specifically the one where the flow separates from the upper surface. It's just easier for pilots to use the airspeed this happens at as it's actually displayed in the cockpit. However that airspeed will change with all up mass and g-force.
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Thursday 25th August 2016 20:39 GMT John Brown (no body)
Re: Certainly looks like a stall...
"At least, though, all they need to do to repair is to bolt another shed on the bottom. Maybe attach a couple of straw bales to it next time though."
Maybe in the next iteration, put the shed on the top and all soft bouncy stuff on the bottom. Just in case, like.
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Thursday 25th August 2016 18:52 GMT Matt Bryant
Re: DoctorNine Re: It's a ship.
"They should have pumped ballast to the rear of the ship....." An interesting idea - maybe it was a ballast issue, but also a control issue in that they accidentally pumped water ballast forward in a panic when they should have pumped it aft. Some flying accidents are caused by the pilot being twisted round to look aft and then moving the controls the wrong way, then compounding the problem by pushing the controls even more the wrong way in panic. It would explain how the dive seemed to continue to steepen rather than starting to recover.
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Friday 26th August 2016 20:16 GMT JassMan
Re: DoctorNine It's a ship.
Admittedly I don't know the details of this particular ship but I have flown on an Airship Industries Skyship 500 and the pilot assured me that all the other airships he had flown used ballast to change the pitch attitude. Not surprisingly they use air, not water, as they don't need to carry it around with them when it not needed. Basically, there is a large bladder at each end, with a very big fan pushing air in when required. This has 2 effects:-
1) air is surprisingly heavy when you have enough of it (or light in a hot air balloon)
2) the volume occupied by the by the bladder pushes on the helium balloon thus reducing the lift at that end of the ship.
I was slightly surprised when he showed me the bladder evacuation system which consisted of a rope and pulley which lifted a big flap and let the air out again. Simple but effective. On the Skyship, the pilot achieved 30° of pitch up which I think was mainly due to the bladders since it has no aerofoils.
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Thursday 25th August 2016 00:18 GMT Lee D
As someone on Slashdot pointed out. This thing need 38,000 cubic metres of helium to operate. Yeah, that stuff that's rare, almost impossible to create, used for vital things like science and medicine.
And they want to build ten, and larger versions? The helium costs alone would become prohibitive over time, and there's a lot better things you could be doing with it than having the world's slowest crash in a giant ass-shape balloon.
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Thursday 25th August 2016 01:52 GMT AndrewV
That's not entirely true.
Until recently there was no point conducting helium mining exploration because the US were artificially depressing the price by running down their massive stockpile.
Now that's almost exhausted, exploration has begun. And quite successfully too http://www.bbc.com/news/science-environment-36651048
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Thursday 25th August 2016 03:22 GMT Flocke Kroes
Almost impossible to create?
Helium is relatively easy to create. It is a by-product in the manufacture of tritium, and a waste product of experimental fusion reactors. Manufacturing elements is expensive and only worth the trouble if the element does not exist naturally and has a profitable / military use. Even collecting naturally occurring Helium is not worth the effort - unless someone creates a market for it by, for example, flying giant airships.
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Friday 26th August 2016 16:39 GMT Suricou Raven
Re: Almost impossible to create?
Helium production by that means would be ridiculously expensive. Helium currently produced is a byproduct of natural gas production - over geological time enough has accumulated from captured alpha particles that it can be (just barely) profitable to purify and ship it.
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Thursday 25th August 2016 11:52 GMT John Smith 19
"Yeah, that stuff that's rare,.. used for vital things like science and medicine."
Actually mostly found being bled off oil wells in Texas. And IIRC the US is selling it's entire strategic reserve (about 1 billion cubic metres) on the open market because they did not need that much for err strategic uses.
It''s been along time since I thought the only way you could get He was distilling air.
It's not.
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Thursday 25th August 2016 17:49 GMT cray74
Yeah, that stuff that's rare, almost impossible to create, used for vital things like science and medicine.
Earth's atmosphere has 3.77x10^12kg of helium, enough to fill 555 million Airlanders. And if they spring a leak it goes back in the atmosphere.
Helium production by fractional distillation of air isn't cost effective when the competing source is sticking a fancy steel straw in the ground, but it's not rare.
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Thursday 25th August 2016 18:10 GMT fnj
@cray74:
Well, all neon is produced by fractional distillation of atmospheric air. However, it costs $330/kg. The volumetric concentration of helium in the atmosphere, however, is less than one third that of neon, so it would be extremely expensive to produce using this method. Logic would suggest at least $3000/kg (the density being 1/3 as much as neon in addition to the concentration being 1/3 as much).
Right now, helium extracted from natural gas costs only in the general neighborhood of $20-30/kg.
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Thursday 25th August 2016 01:18 GMT Anonymous Coward
Suggestion for El Reg: Go to Cardington and photograph the hangar...those are sheds on an epic scale that you simply won't believe until you see it. I used to live near there; saw them multiple times and still don't believe it. The Cardington sheds are one of those things that you don't believe while looking at it. Take someone else, so they can be a tiny dot in front of the doors for perspective.
Sheds as landscape. If you can make those invisible, I'll be genuinely impressed.
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Thursday 25th August 2016 11:31 GMT imanidiot
Recently visited the ex CargoLifter hangar in eadt Germany (now a tropical swimming pool/resort). The scale of these buildings is just mindboggling. You feel truly tiny standing under something that big. (The cargolifter hall could contain the eiffel towe on its side. With room to spare)
CargoLifter was btw also the previous company to try this exact idea. They built the hangar and promptly ran out of money.
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Thursday 25th August 2016 13:25 GMT asphytxtc
Indeed, they are ENORMOUS.. I live and work just around the corner from them (got to see the flying bum yesterday as well from the office). Even when you're standing right next to them, the scale of them still doesn't compute.. incredible buildings, and look fantastic after their refurbishment too.
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Biting the hand that feeds IT
