The Vulcan XH558 & General Aviation Thread

[Renegadenemo]

Ah, but despite most of the air going around the outside, sufficient ash still went through the core to coat the hot end in powder that then fused into a glass-like product and finally put the fire out so the core taken in isolation is surely much the same as an Orph or Oly'. It wasn't until the engines had been dead for a while, windmilling and cooling that the glass began to contract and crack away allowing them to be restarted. Interestingly though, having done a bit of research, it seems that no.2 engine did surge after it was restarted. Intriguing. The damn things will eat whole chickens all day long then they choke on a mouthful of dust.

[TheDarkSide]

My quick Google search put the melting point of stainless around 1600 and that of silica at 1350.

Potential schoolboy question, but is the melting point of silica affected by how much moisture it's absorbed?

[Renegadenemo]

The moisture flashes off when you warm the stuff up so I'd imagine any would be long gone well before it thought about melting.

My mother used to have a new-fangled biscuit tin with a thick lid that shook like a maraca because it was full of silica gel to keep the biscuits crispy. On the underside was printed instructions to bake it in the oven periodically to dry the crystals.

[mtskull]

Ah, but despite most of the air going around the outside, sufficient ash still went through the core to coat the hot end in powder that then fused into a glass-like product and finally put the fire out so the core taken in isolation is surely much the same as an Orph or Oly'.

I have to say that I am now stepping outside the area of my experience, so take this speculation as you find it but I would suggest that, for reasons already mentioned, the impairment of turbine efficiency would be relatively gradual for a Turbofan compared to a Turbojet; hence whilst the one simply spools down, the other may be more prone to surging.
With reference the BA 747 incident, also bear in mind that we are comparing the effect of ash ingestion over several minutes with the effect of a bagful of silica gel all in one go...

[StewDurham]

Silicon loves forming silicon carbide in the prescence of a nice high temperature hydrocarbon reaction - it's often a bugger to stop it in forming in steels, never mind a nice hot gas reaction chamber with excess CO. I'm guessing silicon carbide particles in a hot gas stream won't do the hot end vanes any favour. Bugger, but fair play to them for putting the video's up. The last question of the day at the talk at Durham Uni a few weeks ago was "how long will she fly for?" Answer was about the airframe will be up on hours in a few years time with about another season possible if they fit a strengthener to the leading edges, but they only have (had) 2 spare engines.

[Mike Bull]

'...Mr Pearson's got the engine well in hand...'

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[Mike Bull]

Time lapse of No.2 being dropped-

[rob565uk]

Looking at these videos, I am mightily impressed by the overall engineering standards demonstrated by the Vulcan Team. If anyone had any doubt where their donations go, this sort of footage should dispel them completely. It really underlines the cost of keeping this unique aircraft flying and the skill and dedication of the Team.

Many years ago, I was boating on Lake Windermere when I heard powerful jet engines. Looking around, I spotted a Vulcan flying South to North towards me up the Lake at a level lower than normal. As it passed close overhead, the pilot throttled up for a fairly steep climb over Kirkstone Pass and that image, the sounds of the engines and the smell of jetfuel are forever etched into my mind, at least in part because of the parallel with the Vulcan that flew over Coniston on 5th January 1967 in a salute to Donald.

What a tremendous aeroplane - a reminder of British engineering at its very best.

[Renegadenemo]

Great aeroplane, and don't forget the gubbins inside either. That H2S radar was amazing!

[rob565uk]

Ah, H2S - a wonder indeed. An all-British centimetric radar system conceived in the 1940s for target identification and navigation for bombers and only taken out of service half a century later when the last Vulcan was taken off active duty. It was used for the bombing run on Port Stanley airfield in the Falklands conflict. The Germans captured one of the early WW2 versions from a lightly crashed Halifax bomber and from it gleaned enough information to accelerate creation of their Wurzburg and Freya radar systems. Without that capture, they probably would have taken another couple of years to get to the same point. Unfortunately, the effectiveness of German night-fighters pursuing our bombers was increased considerably by the capture of H2S and the earlier use of Wurzburg and Freya systems.

The enabling technology for H2S was the multi-cavity magnetron as a source of high-power centimetric waves - the descendent of which powers your microwave at home. Although the magnetron was developed in parallel in a number of countries, it was the British who got it working first. It's a thermionic device, or "Valve" in old-fashioned language - but unlike other valves it has never been replaced with a compact transistor/semiconductor equivalent. There is still no semiconductor device that can produce centimetric or millimetric waves at such high power in a single device - hence why your microwave still uses one.

As the name suggests, it relies on magnetic fields, and extremely strong ones at that. Generally, a horshoe magnet is used with the valve placed in the intense field in the gap of the horseshoe. I have a number of old magnetron horseshoe magnets and you have to be careful to retain a keeper across the open gap, otherwise all the ferromagnetic bits on your bench race rapidly towards the gap (I kid you not). I once entered a radar workshop to see what appeared to be a 6 inch nail suspended in mid air... On closer inspection, one end of it was tied off to the bench with very fine fishing line and the nail was held in mid air by a magnetron magnet in a cupboard fully 6 inches away from the nail! A good illusion.

But nobody has ever been sure where the name H2S originated, or what it stood for.