The Vulcan XH558 & General Aviation Thread

[Mike Bull]

Personally I think that the Vulcan team have done a very brave thing in releasing as much information as they have as the internet is now unfortunately littered with vitriolic comments.

I agree Stuart- there's been some very nasty stuff posted out there by some people, and it's terribly unfair; I mean yes, it's a fundamental and silly mistake that's had great cost, but, no one is going to feel as bad as the folk responsible, and the team have been very transparent in their honesty about the incident. Here's hoping they get the old thing back into the air again in double quick time, especially as she (finally!) has a nice new coat of shiny paint to show off this year.

[Mike Bull]

Newsletter from the Vulcan guys, complete with video and picture links-

http://mxm.mxmfb.com/rsps/wlnk/c/1216/r/207663/e/382

[rob565uk]

Is this what happens to silica gel? We have lots of it in the workshop - I feel an interesting experiment coming on.

Having been part of the last experiment, you needn't think I will be sitting in the jetflow to check the RPM while you do it

[Stuart Baker]

I feel an interesting experiment coming on.

Suggest you find a few panels which need blasting, tell Checkie they will make excellent shields and get him to stand by the exhaust. I'm sure he'll go for it if we all say it'll be OK. Please let me know when you plan to run the test - I'll bring my video camera

[Jordangbr]

It'll fix

[Stuart Baker]

Bill - The only wisdom I can give you is that silica gel will melt at about the same temperature as your stainless steel crucible. Turbine gas temperature can be hotter than this as the blades are cooled, so interesting experiment, but you really need to use a real engine!

Neither the Orph, nor the Oly 202 fuel systems have compressor surge avoidance systems. They didn't really start to appear until electronics were introduced to controls.

On hols for a bit now. Hopefully by the time I get back we will have some data and be able to stop speculating

[Renegadenemo]

But speculating is fun... Nothing meant by it, it's just interesting. I'll have to get even more heat on my silica gel then. The TIG torch ought to do it. The little bit of Googling I did from my phone suggested that the gel ought to melt before the stainless but it was never a well controlled experiment.
I remember watching a programme about the Trent engine and they said that a single turbine blade could contain sufficient energy to boil a kettle four times and without its cooling it would melt immediately so the gas must get flippin' hot.
It's a shame AAIB aren't involved though - I like to read their reports.


http://www.aaib.gov.uk/publications/bulletins.cfm

[mtskull]

Bill - The only wisdom I can give you is that silica gel will melt at about the same temperature as your stainless steel crucible. Turbine gas temperature can be hotter than this as the blades are cooled, so interesting experiment, but you really need to use a real engine!

A brief bit of internet research (because I lie awake at night wondering about these things, too) provided the following figures, all in degrees Celcius:

Max turbine inlet temp. at takeoff thrust (Olympus 593): 1400
Typical melting point of stainless steel: 1500
Melting point of silica gel: 1625

The 593 series is different from the 301 used on the Vulcan but unless the 301 runs at significantly higher temperatures, I guess that's one theory blown out of the water.

[Renegadenemo]

My quick Google search put the melting point of stainless around 1600 and that of silica at 1350 so clearly more Googling was needed. No matter - I shall fire up the TIG torch and put a ridiculous amount of heat into those little glass beads. I'm intrigued as to how something so seemingly innocuous can trash such a big, grunty engine. I'd also like to understand it for our own knowledge. I mean, what if you can do the same to an Orph' with a crisp packet?
I may be wrong but didn't the BA 74 engines that ingested all that dust just roll-back? They didn't surge, so far as I know.

[mtskull]

I mean, what if you can do the same to an Orph' with a crisp packet?
I may be wrong but didn't the BA 74 engines that ingested all that dust just roll-back? They didn't surge, so far as I know.

The BA 747 engines were high bypass ratio turbofans, so only around a quarter to a fifth of the air (and therefore ash) passing through the engine intakes would have gone down the hot section into the turbine. Furthermore, in a turbofan there is a tendency for material striking the fan to be flung outwards towards the cold stream, so the proportion of ash ingested by the hot section might well have been even less.
In a pure turbojet like the Olympus (or Orpheus), there is nowhere else for ingested material to go, other than where it can do the most harm. Keep those crisp packets out of the way, chaps!