Engineers - any sign of ash damage so far?
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I think you may be mixing it up with the Viper as fitted to Jet Provost, and some earlier powerplants.
RR Viper, also used on the early models of the HS.125...also a fine aircraft/engine combo, although just a tad...noisey.
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Mad Jock
First of all, slightly off topic - bear with me Agaricus Bisporus - but I refer to Mad Jock;
My sincerest thanks for that Jock, because in my eighteen years as an MRI engineer (33 as CT eng) nobody, including all our support engineers and factory Service Engineering types, have ever come up with any more than a half ar8ed answer to that particular conundrum. Particularly when there is almost never any water ice in there - only Oxygen ice. You sir, I believe, have it exactly. Thank you again - I will be offering it to my colleagues who, I trust, will think I am truly the dog's bo11ocks. 
Right, back on thread; Agaricus Bisporus asked;
Which I thought a bit disingenuous as Forget then reminded us;
Which I suspect held the nugget there, entirely cogent to the overall question - to which L337 posted the answer.
I know a lot of people, all engineers or interested in engineering, who were absolutely gagging to know what you BA Aero Engineers found when you got your hands on that 744 at Cardiff. Like others, I had thought the flight was a bit of a PR stunt, but when I learned that the short hop to Cardiff had taken some three and a half hours and stepped all the way up to 40,000ft, I began to suspect that Willie Walsh was going to be standing next to you when you carried out your checks.
Thank you for that L337.
Roger.
Theory alert could be bollocks.
Surface tentsion allows fluids to do some very strange things when in capillarys liquified gases are famous for it. They will allow fluid to travel uphill so to speak.
My theory is that they have a slight leak and there is Oxygen fluid forming, if it manges to bridge the hole the surface tension will start doing its work and cappilary action will work pulling it up stream. Now because the fluid will be travelling into a cooler temp it will aid heat transfer to the outside it will cause even more oxygen to become liquid and supply the capilary action. Once its inside if there is any sort of height difference between top and bottom of the seal you will have started a syphon. Liquid oxygen being relatively heavy compared to He will have no probs overcoming the 4 psi differential. And thus you have an up hill (in pressure differential terms) leak. Look on the bright side though it means your not loosing highly expensive He through a seal leak.
Surface tentsion allows fluids to do some very strange things when in capillarys liquified gases are famous for it. They will allow fluid to travel uphill so to speak.
My theory is that they have a slight leak and there is Oxygen fluid forming, if it manges to bridge the hole the surface tension will start doing its work and cappilary action will work pulling it up stream. Now because the fluid will be travelling into a cooler temp it will aid heat transfer to the outside it will cause even more oxygen to become liquid and supply the capilary action. Once its inside if there is any sort of height difference between top and bottom of the seal you will have started a syphon. Liquid oxygen being relatively heavy compared to He will have no probs overcoming the 4 psi differential. And thus you have an up hill (in pressure differential terms) leak. Look on the bright side though it means your not loosing highly expensive He through a seal leak.
Right, back on thread; Agaricus Bisporus asked;
Mods, please close this thread if it doesn't come back onto topic.
I asked a topical question that had nothing to do with odd behaviour in gas capilliary action or labyrinth seals.
I asked a topical question that had nothing to do with odd behaviour in gas capilliary action or labyrinth seals.
But it does. As Smudge said -
Quote:
gas turbine engines employ labyrinth seals which rely on air tapped of the compressors to function ,this air actually enters the bearing sumps therefore any contaminants which are in that air will possibly enter the engine oil system,
Quote:
gas turbine engines employ labyrinth seals which rely on air tapped of the compressors to function ,this air actually enters the bearing sumps therefore any contaminants which are in that air will possibly enter the engine oil system,
I know a lot of people, all engineers or interested in engineering, who were absolutely gagging to know what you BA Aero Engineers found when you got your hands on that 744 at Cardiff. Like others, I had thought the flight was a bit of a PR stunt, but when I learned that the short hop to Cardiff had taken some three and a half hours and stepped all the way up to 40,000ft, I began to suspect that Willie Walsh was going to be standing next to you when you carried out your checks.
Thank you for that L337.
Roger.
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Nae Bother landrodger suprised one of your RPA's didn't spot it.
I can even suggest a method of sealing against it which might cut down your HE getting through seals so quick.
If you get your seal and put a water shroud over the top of it and fill it will distilled 100% H2O then freeze it down either using system temp or expanding gas over it. Then bring your system down to temp. The Ice will be denser than your seal so the He should take longer to get through it. And the interface where the cappilary action takes place will not have any air near it to form liquid O2. Vibration may be a problem breaking the seal between ice and surface but it could help out with some of the seals. If you can figure out a way of getting pressurised ice eg blue glacier ice with no O2 in it even better.
PS take all the glory for yourself, and do a patent search before you mention it to any one. Could be a nice boost to your pension. And in my child hood and to this day I don't think of MRI, it was and always will be NMR.
I can even suggest a method of sealing against it which might cut down your HE getting through seals so quick.
If you get your seal and put a water shroud over the top of it and fill it will distilled 100% H2O then freeze it down either using system temp or expanding gas over it. Then bring your system down to temp. The Ice will be denser than your seal so the He should take longer to get through it. And the interface where the cappilary action takes place will not have any air near it to form liquid O2. Vibration may be a problem breaking the seal between ice and surface but it could help out with some of the seals. If you can figure out a way of getting pressurised ice eg blue glacier ice with no O2 in it even better.
PS take all the glory for yourself, and do a patent search before you mention it to any one. Could be a nice boost to your pension. And in my child hood and to this day I don't think of MRI, it was and always will be NMR.
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errr - since one of my postings got caught in some diversions about plane-spotting, MRI, liquid Helium, etc. could I please also request a return to the original topic!
Ok - we now have some evidence that the BA 'test' / PR flight that ended up at Cardiff having meandered around some 'ash-containing' bits of sky did not ACTUALLY have a significant 'ash encounter'. Great - Willy Walsh was in no serious danger after all!
Doesn't make any difference to a REALLY basic question: IF (probably WHEN) volcanic ash becomes a problem in N Europe again, what reliable measures exist to measure the extent of ash encounters soon after they happen? Visual external inspection is OK if there's something to see. Don't rely of flight crew reports: frequently, there will have been nothing to report, from inside or outside the aircraft.
So the answer is there are NO effective measures. Does that make you guys on the firing line happy? Well, it shouldn't. Remember particularly ash damage MUST be cumulative and that aircraft utilisation is often on reciprocal routes, repeated ad nauseam.
Ok - we now have some evidence that the BA 'test' / PR flight that ended up at Cardiff having meandered around some 'ash-containing' bits of sky did not ACTUALLY have a significant 'ash encounter'. Great - Willy Walsh was in no serious danger after all!
Doesn't make any difference to a REALLY basic question: IF (probably WHEN) volcanic ash becomes a problem in N Europe again, what reliable measures exist to measure the extent of ash encounters soon after they happen? Visual external inspection is OK if there's something to see. Don't rely of flight crew reports: frequently, there will have been nothing to report, from inside or outside the aircraft.
So the answer is there are NO effective measures. Does that make you guys on the firing line happy? Well, it shouldn't. Remember particularly ash damage MUST be cumulative and that aircraft utilisation is often on reciprocal routes, repeated ad nauseam.
Remember particularly ash damage MUST be cumulative and that aircraft utilisation is often on reciprocal routes, repeated ad nauseam.
The data does not support it.
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Moderating threads ....
Just so folks have a handle on my philosophy .. in general I try not to interfere with a thread as whatever I do it is always a case of "you can please some of the people some of the time and none of the people all of the time" so I get shot whether I leave it or edit it ...
The only time I tend to jump in is if anyone starts to get nasty etc., or if a thread goes so far off the rails ...
In fact, I think one of the great things about PPRuNe is the range of digressions which crop up in threads .. ?
Just so folks have a handle on my philosophy .. in general I try not to interfere with a thread as whatever I do it is always a case of "you can please some of the people some of the time and none of the people all of the time" so I get shot whether I leave it or edit it ...
The only time I tend to jump in is if anyone starts to get nasty etc., or if a thread goes so far off the rails ...
In fact, I think one of the great things about PPRuNe is the range of digressions which crop up in threads .. ?
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As a BA pensioner I hope W.W. looked at the fine print of the insurance policy before his trip, the cost of a 747-400 could have put a dent in our liquidity .
Joking apart I bet a lot of midnight oil was burnt before it was decided to make the trips and was not a rush of blood to the head on his part .
[Thinks!! was the plane going to Cardiff for o/h anyway?].Cynic.
P/S I'm NOT a Plane spotter though still interested in the techie and flying side.
Joking apart I bet a lot of midnight oil was burnt before it was decided to make the trips and was not a rush of blood to the head on his part .
[Thinks!! was the plane going to Cardiff for o/h anyway?].Cynic.
P/S I'm NOT a Plane spotter though still interested in the techie and flying side.
......for a linearly variable magnetic field considering only the z direction for now,.....
the water protons in the body will be resonant at vl =gamma/2pi (B0 + GzZ).....
with NMR it is possible to go below absolute zero
ESR is nice
and
NOESY knows everything
could not resist
the water protons in the body will be resonant at vl =gamma/2pi (B0 + GzZ).....
with NMR it is possible to go below absolute zero
ESR is nice
and
NOESY knows everything
could not resist
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Total Loss oil.
Total loss engine oil system
411A is correct. The RAF still flies the Dominie T1 with RR Vipers that have a total loss oil system.
411A is correct. The RAF still flies the Dominie T1 with RR Vipers that have a total loss oil system.
Not many people know that. Roger.
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The data does not support it.
or ash damage inside turbine hot sections being cumulative?
Thinking of the situation where fine-grained VA gets into the cooling channels inside turbine blades and / or forms a glassy coating on blades or stator vanes, therefore blocking leading-edge or other cooling holes, what's actually going to remove it? Therefore, further ash encounters must result in accumulation in the same area(s). If not, why not?
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Perhaps not designed as a partial loss oil system for the Dart, but there was always planty of oil in the wheelwell area of the 748. Always did like the sound when spoolingup. Once it was started, it wasn't so great.
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Thinking of the situation where fine-grained VA gets into the cooling channels inside turbine blades and / or forms a glassy coating on blades or stator vanes, therefore blocking leading-edge or other cooling holes, what's actually going to remove it? Therefore, further ash encounters must result in accumulation in the same area(s). If not, why not?
Thinking of the situation where fine-grained VA gets into the cooling channels inside turbine blades and / or forms a glassy coating on blades or stator vanes, therefore blocking leading-edge or other cooling holes, what's actually going to remove it? Therefore, further ash encounters must result in accumulation in the same area(s). If not, why not?
I think you are dead right. It wouldn't suprise me at all if there are incidents of blade shrouds departing the back end or vane trailing edges disappearing due to a very slow deposition rate of ash deposits inside the components.
I think you are dead right. It wouldn't suprise me at all if there are incidents of blade shrouds departing the back end or vane trailing edges disappearing due to a very slow deposition rate of ash deposits inside the components.
In other words history will be repeated in the numerous events from Mt Pinatuba as documented in the
Thomas Casavadell report
Casadevall
Now what was the question again?
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Just to add some balance to this. I believe that the glass deposits will flake off with engine thermal cycles (takeoffs and shutdowns) and that any deposits in the cooling air holes will eventually work they way out over time.
Not from my experience Lomapaseo. External deposits will be fine as you say, but a couple of blocked dust holes on a blade tip and away she goes.
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Here is a technical report on the engine damage on a DC-8 (CFM engines) operated by NASA after encountering a diffuse volcanic ash cloud. The encounter lasted for a period of seven minutes, was at night, and had it not been for the scientific instrumentation on board the aircraft no one would have been aware the event had taken place. Please note it was estimated the turbine blades may have had as little as 100 hours of life remaining as a result of damage incurred.
http://ntrs.nasa.gov/archive/nasa/ca...2003079762.pdf
http://ntrs.nasa.gov/archive/nasa/ca...2003079762.pdf
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I'm not saying that damage won't happen, but will the pilot have to shutdown engines? or is it only a maintenance finding on the ground?
That report shows the HPT blade (the blade in the photo has been through a repair cycle already). It would have been interesting to also see a fillet cut on the blade, you will normally see a lot of accumillation in the serpentine passages in the airflow "deadzones". It would have also been nice the see the LPT blade 1, which is a shrouded blade with an interlock.
411A,
You speak in jest, of course!
Only aeroplane I have flown that weathercocks out of wind.
Remember the CAGS??
We discovered some really weird characteristics of that Viper, including a ability to surge and only recover to a low power "false idle", with no response to thrust lever movement. One ( not VH-, but ex-VH-) went into the drink near Nice with that problem.
The undercarriage downlock system could only have been designed by Heath Robinson!! Hence the big block of faired hardwood down the guts, and the extended flap hinges with little wear pads, and DCA AU got to prove it worked, Avalon 1965 or '66, from memory.
But the rear main bearing lubrication was total loss, and we did learn to keep very careful track of the minimum oil consumption.
Tootle pip!!
on the early models of the HS.125...also a fine aircraft/engine combo
Only aeroplane I have flown that weathercocks out of wind.
Remember the CAGS??
We discovered some really weird characteristics of that Viper, including a ability to surge and only recover to a low power "false idle", with no response to thrust lever movement. One ( not VH-, but ex-VH-) went into the drink near Nice with that problem.
The undercarriage downlock system could only have been designed by Heath Robinson!! Hence the big block of faired hardwood down the guts, and the extended flap hinges with little wear pads, and DCA AU got to prove it worked, Avalon 1965 or '66, from memory.
But the rear main bearing lubrication was total loss, and we did learn to keep very careful track of the minimum oil consumption.
Tootle pip!!