Brewing Master

Question:

* Pedants may replace the word accuracy with the word precision.   I claim common usage

But precision is more …. precise.

Response:

….snip * Pedants may replace the word accuracy with the word precision.   I claim common usage …snip Those who confuse accuracy with precision are doomed to get wrong answers expressed to 10 places.

Oh thanks a 1,000,000.003  :-)

Response:

- Hide quoted text — Show quoted text – Now you see why I hate students. Oi!! — Sam… pupilpilot! Heh!    :-) There is one thing though.   I very much doubt any engineering student who was so unfortunate as to have me in front of their class will ever, ‘tho they live to be 103, will EVER use more than 3 significant figures if they cannot justify the extra ones The smallest whole number with 3 significant figures is 100.   The largest is 999. The implied *accuracy of a number is plus or minus 1/2 the least count – for the example above that means between 100.5 and 99.5 or 999.5 and 998.5.   So the implied accuracy in the first case is an error of one (100.5-99.5) in 100 and in the second case it is 1 in 1000. So 3 significant figures represent a range of accuracy of between 1% and 0.1%. Now who’s kidding who?   Unless it is a project of critical national importance, such as a new brewery, no engineer expects to do better than 5%. How can you?   The accuracy of the output is determined by the accuracy of the input data.   That’s why factors of safety are used. * Pedants may replace the word accuracy with the word precision.   I claim common usage Given the above, you can see why when I read: " …… an airframe is considered to be 997.1 metres." (That’s 4 significant figures – and right at the top of the 4 sig fig range! The implied accuracy is plus/minus 50 mm  in a KILOMETRE!!!!!!) I posted: "  Nobody but a student (or a graduate who should have been failed) would have reported that number.   The implied accuracy is 1 in 10,000 – or 0.01%. In fluid dynamics (especially!) or any other engineering? Tell them to getta bloody grip!" (Actually it’s quite useful when you get numbers like that from authorities. Very heartning.  It shows they have no clue about reality and they make for easy meat in a court case <smirk

Well said, RT The fact that the accuracy of your output can be no better than (and is usually less than) the accuracy of your least precise input was taught to me by my 4th-year high school maths teacher. Didn’t need to do a degree in engineering to understand that. (But I bow to your much more precise statement of the principle). She told us an anecdote to help raise our awareness. The anecdote was simple. "A pilot crashes his aeroplane into the side of a hill. What went wrong?" We had to suggest possible causes and/or ask for more information. She would tell us if we were right or wrong. None of us got the right answer, but I got closest with the suggestion that he misread his altimeter (I was always interested in human factors… but I digress…) The answer was that the altimeter was wrong. Instrument failure. Important lesson- learn to doubt the instruments until you have evidence otherwise, and never take their readings as exact. I was reminded of this many years later when undergoing a checkup after my transplant. The doc (a physician- very bright lad, and highly trained) took my blood pressure- it had been a bit on the high side and I was taking some mild medication for it. He looked puzzled, sat down, and began scratching his head. "You only take one tablet, right?" he said. "Yes" I replied. "Have you been dizzy lately, you know, when you stand up suddenly?" "No" I replied- in fact I had been feeling fine, so wondered what he was getting at. "What are the symptoms of high blood pressure?" I asked "High blood pressure?" he said "Well, there’s headaches, and.. but you shouldn’t have to worry about that- far from it." By now I was puzzled. "What blood pressure did you get?" I asked. "60 over 40" he replied. I laughed. "No way" I said. "Your gauge is wrong. It has to be." We went next door to the next cubicle and this time the reading was the usual 120/80. The medication was doing its stuff, and he looked very relieved. I hope he got the lesson too. Coop (And *I* had to suggest he put a "U/S" note on the faulty gauge….)

Response:

(And *I* had to suggest he put a "U/S" note on the faulty gauge….)

That’d be right.   Medicine and maths are at the opposite ends of the intellectual spectrum – as is easily demonstrated when they try to use statistics and probability.

Response:

|| (And *I* had to suggest he put a "U/S" note on the faulty gauge….) | | That’d be right.   Medicine and maths are at the opposite ends of the | intellectual spectrum – as is easily demonstrated when they try to use | statistics and probability. 5 out of 4 doctors agree …. — Cheers Dave Kearton

Response:

RT is being kind. Sounds like bull to me. Need a lot more definitive data here. For a start, the plumes from two vents 39m apart, 6.2m diameter blowing exhaust gas at 40m/s would remain apart due to vorticity, so the overall plume would become a bifuricated turbulent eddy. flow at ambient pressure is obviously small, and the net buoyancy only a few tens of metres above the vents would rapidly reduce due to shear diffusion mixing. What vertical velocity is defined as airframe damaging ? Is this vertical velocity what is predicted at 997.1agl ? What jet/plume model/software was used for the calculations ? What PBL characteristics/parameters were modeled ?

Response:

RT is being kind.

Me?  Kind!?  Heart-pills, quick! Sounds like bull to me. Need a lot more definitive data here. For a start, the plumes from two vents 39m apart, 6.2m diameter blowing exhaust gas at 40m/s would remain apart due to vorticity, so the overall plume would become a bifuricated turbulent eddy.

Ahhhhhhh – ok.   It’s not my field but had assumed vorticity would have encouraged coalescence early on as they are so close to each other (approx 7 diameters).   But, <blush, like I said it’s not my field. flow at ambient pressure is obviously small, and the net buoyancy only a few tens of metres above the vents would rapidly reduce due to shear diffusion mixing.

I like it As an aside.. You ever come across the suggestion to blow smoke rings to reduce pollution from stacks – er, well, actually to get the pollution up higher in the atmosphere? At first it seems outright silly, but years ago we had a grader that blew some smoke rings and, I’ll give you the mail, they went up a bloody lot further than the usual exhaust plume  Dunno how they are defined – a stable toroid? – Hide quoted text — Show quoted text – What vertical velocity is defined as airframe damaging ? Is this vertical velocity what is predicted at 997.1agl ? What jet/plume model/software was used for the calculations ? What PBL characteristics/parameters were modeled ?

Response:

….snip * Pedants may replace the word accuracy with the word precision.   I claim common usage

…snip Those who confuse accuracy with precision are doomed to get wrong answers expressed to 10 places. AW

Response:

Now you see why I hate students. Oi!! — Sam… pupilpilot!

Heh!    :-) There is one thing though.   I very much doubt any engineering student who was so unfortunate as to have me in front of their class will ever, ‘tho they live to be 103, will EVER use more than 3 significant figures if they cannot justify the extra ones The smallest whole number with 3 significant figures is 100.   The largest is 999. The implied *accuracy of a number is plus or minus 1/2 the least count – for the example above that means between 100.5 and 99.5 or 999.5 and 998.5.   So the implied accuracy in the first case is an error of one (100.5-99.5) in 100 and in the second case it is 1 in 1000. So 3 significant figures represent a range of accuracy of between 1% and 0.1%. Now who’s kidding who?   Unless it is a project of critical national importance, such as a new brewery, no engineer expects to do better than 5%. How can you?   The accuracy of the output is determined by the accuracy of the input data.   That’s why factors of safety are used. * Pedants may replace the word accuracy with the word precision.   I claim common usage Given the above, you can see why when I read: " …… an airframe is considered to be 997.1 metres." (That’s 4 significant figures – and right at the top of the 4 sig fig range! The implied accuracy is plus/minus 50 mm  in a KILOMETRE!!!!!!) I posted: "  Nobody but a student (or a graduate who should have been failed) would have reported that number.   The implied accuracy is 1 in 10,000 – or 0.01%. In fluid dynamics (especially!) or any other engineering? Tell them to getta bloody grip!" (Actually it’s quite useful when you get numbers like that from authorities. Very heartning.  It shows they have no clue about reality and they make for easy meat in a court case <smirk

Response:

- Hide quoted text — Show quoted text – As suggested by: " plume rise has been calculated as being reduced to not more  than 4.3 metres per second at an average height of 109.5 metres AGL (360 ft  AGL) and a maximum height of 997.1 metres AGL (3271.3 ft AGL)" (4.3 m/s =1000 ft/min) Suggest massive arse covering going on in typical public servant Suggest you ignore the whole thing Thanks for the additional info.

I wonder if the local gliding club knows about this….. Coop

Response:

Harold said…. Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian Brian,  you’re not talking about the Newport Power Station – which has been there for yonks – are you?

Newport has one chimney which is about 200 metres tall. It might be a new gas fired peaking plant which uses gas turbines, similar to jet engines. There are a few of these being installed around Melbourne and to the west to take advantage of the gas fields near Portland/Warnambool..

Response:

RT said…. Suggest you get some data on the velocity decay from jet eflux. Suggest you’d get a hard ‘bump’ at 500ft but nothing of note above that.

Haven’t done it in years, but recall a flight over the local paper mill, at around 1,500 ft experiencing some turbulance. Have flown directly over the Loy Yang complex and don’t recall feeling any turbulence. That too was around 1,500ft (the LY chimneys are about 900ft tall). We have gas peaking plant next door to Loy Yang. 12 engines driving 6 generators. All aero derivative PW engines running on natural gas with a total of 320 MW generating capacity. Similar figures to this plant near Laverton as far as exhaust gas temps go. I wonder if there is any restrictions on where you can fly there? Maybe a called to Latrobe Valley Aero Club is in order..

Response:

– Hide quoted text — Show quoted text – <snip As an aside, near the main ML runway centreline they are installing – I think at about 15 DME – a power station to backup the electric grid for Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian Brian,  you’re not talking about the Newport Power Station – which has been there for yonks – are you? Harold. No Harold, this is entirely new.  Two plume stacks a short distance apart and the exhausts join to make an invisible high speed exhaust outlet that can overstress an airframe passing thru up to about 4000′. (There is a similar lower level item at the Bass Gas plant near Nyora). As it is grid demand generated there are no fixed hours of use, thus cannot be notified by NOTAM. Original suggestion to RAPAC was to make it a "D" area, we have pushed for "Restricted". I have a severe problem with the mechanics of this (a short stack – or even a pair of short stacks –  producing extreme turbulence at 4,000 ft). What is the maximum electrical power output of the power station and what fuel is used? RT Don’t know power output. RAPAC Agenda doco as follws: –  a.. 6.3. Creation of Danger or Restricted Area at Laverton North due Power Station Kevin Smith, CASA, submitted the following correspondence for RAPAC information. The location is at the intersection of the Princes FWY (Geelong Road) and Kororoit Creek Road and Fitzgerald Rd at Laverton North, between the FWY and Cherry Lane. S37.50′35" E144.47′13" (MELWAYS 53H4) The reason is because of the construction of a Gas Fired Peaking Power Station at 127 Cherry Lane, Laverton North, and the exhaust plume rise from the two exhaust stacks at the power station. The stacks are to be 39 metres apart and the plume rise has been calculated as being reduced to not more than 4.3 metres per second at an average height of 109.5 metres AGL (360 ft AGL) and a maximum height of 997.1 metres AGL (3271.3 ft AGL) The effects of the plume are generally expected to be within 260 metres of the centre of the two stack positions. Therefore it is intended to establish a Danger or Restricted Area within possibly a 500 metres radius of the assessed centre position of the stacks, from Surface to about 4000ft. While the power station is designed to cover peak periods at this stage, the Danger or Restricted Area will of necessity be H24. It is not yet known when the station will be operational, but I understand that mid next year is a possibility. Below notes from RAPAC meeting taken from CASA representative advice: – Brian Corro from Snowy Power Generation. understanding is as follows: – 1.  Two 30 metre high outlets 39 metres apart, the exhausts merging to be treated as one exhaust plume.  14 metres base, 6.2 metres at outlet. 2.  In a mixed residential / industrial area, unlikely to be specially painted to show up. 3.  Possibly, still under consideration, strobe light. 4.  No cooling towers and NO visible indication of operation and gas emission.  Operation on grid demand, no fixed times. 5.  Exhaust speed at outlet is 39.9 metres per second at 550 degrees C. 6.  Safety height where gas has slowed to a speed that will not overstress an airframe is considered to be 997.1 metres. 7.  On the edge of the high traffic 1500 and 2500 ML CTR steps.

Ok – on the basis of the exhaust velocity (ca 150 km/hr) it’s a (twin) gas turbine installation and I agree the exhaust plume will be a single one because of the high initial velocity  and (relatively) small separation of the two exhausts.  They can be expected to coalesce, ie. " 6.  Safety height where gas has slowed to a speed that will not overstress an airframe is considered to be 997.1 metres."

Bullshit. That is absolute crap.   Now you see why I hate students.  Nobody but a student (or a graduate who should have been failed) would have reported that number.   The implied accuracy is 1 in 10,000 – or 0.01%. In fluid dynamics (especially!) or any other engineering? Tell them to getta bloody grip! Suggest you get some data on the velocity decay from jet eflux. Suggest you’d get a hard ‘bump’ at 500ft but nothing of note above that. As suggested by: " plume rise has been calculated as being reduced to not more  than 4.3 metres per second at an average height of 109.5 metres AGL (360 ft  AGL) and a maximum height of 997.1 metres AGL (3271.3 ft AGL)" (4.3 m/s =1000 ft/min) Suggest massive arse covering going on in typical public servant Suggest you ignore the whole thing Thanks for the additional info.

Response:

Some of you may have seen the Defence media release about the expansion of the Cultana Training Area near Pt Augusta. Most of it is about giving the Abrams drivers a greater expanse of mud to churn up, but buried in the supplementary material is mention of "upgrading the Port Augusta airstrip in order to support at the least RAAF C-130J, and possibly USAF C-141 or C-5 flight operations." And, presumably, RAAF A330s when they arrive. Cheers David

Response:

Some of you may have seen the Defence media release about the expansion of the Cultana Training Area near Pt Augusta. Most of it is about giving the Abrams drivers a greater expanse of mud to churn up, but buried in the supplementary material is mention of "upgrading the Port Augusta airstrip in order to support at the least RAAF C-130J, and possibly USAF C-141 or C-5 flight operations." And, presumably, RAAF A330s when they arrive. Cheers David

David Good news for the airfield users but watch out for any expansion of the tank training area infringing the missed approach etc at Port Ag (I’m not a visitor there so unfamiliar with the proximity of the tank area and airstrip). At the last Vic RAPAC meeting we had to agree to restrictions on the missed approach at Mangalore due to tank training " the war on terrorism takes priority) and an extended MIL area at Pukka. cheers Brian

Response:

Good news for the airfield users but watch out for any expansion of the tank training area infringing the missed approach etc at Port Ag (I’m not a visitor there so unfamiliar with the proximity of the tank area and airstrip).

The expanded tank training area will be the 1800 square km area of pastoral land NW of Whyalla. The closest it will get to Pt Augusta itself is about 25km. Being a live fire area, I think it will be well marked. Cheers David

Response:

– Hide quoted text — Show quoted text – <snip As an aside, near the main ML runway centreline they are installing – I think at about 15 DME – a power station to backup the electric grid for Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian Brian,  you’re not talking about the Newport Power Station – which has been there for yonks – are you? Harold. No Harold, this is entirely new.  Two plume stacks a short distance apart and the exhausts join to make an invisible high speed exhaust outlet that can overstress an airframe passing thru up to about 4000′.  (There is a similar lower level item at the Bass Gas plant near Nyora). As it is grid demand generated there are no fixed hours of use, thus cannot be notified by NOTAM. Original suggestion to RAPAC was to make it a "D" area, we have pushed for "Restricted". I have a severe problem with the mechanics of this (a short stack – or even a pair of short stacks –  producing extreme turbulence at 4,000 ft). What is the maximum electrical power output of the power station and what fuel is used?

RT Don’t know power output. RAPAC Agenda doco as follws: –   a.. 6.3. Creation of Danger or Restricted Area at Laverton North due Power Station Kevin Smith, CASA, submitted the following correspondence for RAPAC information. The location is at the intersection of the Princes FWY (Geelong Road) and Kororoit Creek Road and Fitzgerald Rd at Laverton North, between the FWY and Cherry Lane. S37.50′35" E144.47′13" (MELWAYS 53H4) The reason is because of the construction of a Gas Fired Peaking Power Station at 127 Cherry Lane, Laverton North, and the exhaust plume rise from the two exhaust stacks at the power station. The stacks are to be 39 metres apart and the plume rise has been calculated as being reduced to not more than 4.3 metres per second at an average height of 109.5 metres AGL (360 ft AGL) and a maximum height of 997.1 metres AGL (3271.3 ft AGL) The effects of the plume are generally expected to be within 260 metres of the centre of the two stack positions. Therefore it is intended to establish a Danger or Restricted Area within possibly a 500 metres radius of the assessed centre position of the stacks, from Surface to about 4000ft. While the power station is designed to cover peak periods at this stage, the Danger or Restricted Area will of necessity be H24. It is not yet known when the station will be operational, but I understand that mid next year is a possibility. Below notes from RAPAC meeting taken from CASA representative advice: – Brian Corro from Snowy Power Generation. understanding is as follows: – 1.  Two 30 metre high outlets 39 metres apart, the exhausts merging to be treated as one exhaust plume.  14 metres base, 6.2 metres at outlet. 2.  In a mixed residential / industrial area, unlikely to be specially painted to show up. 3.  Possibly, still under consideration, strobe light. 4.  No cooling towers and NO visible indication of operation and gas emission.  Operation on grid demand, no fixed times. 5.  Exhaust speed at outlet is 39.9 metres per second at 550 degrees C. 6.  Safety height where gas has slowed to a speed that will not overstress an airframe is considered to be 997.1 metres. 7.  On the edge of the high traffic 1500 and 2500 ML CTR steps.

Response:

– Hide quoted text — Show quoted text – <snip As an aside, near the main ML runway centreline they are installing – I think at about 15 DME – a power station to backup the electric grid for Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian Brian,  you’re not talking about the Newport Power Station – which has been there for yonks – are you? Harold. No Harold, this is entirely new.  Two plume stacks a short distance apart and the exhausts join to make an invisible high speed exhaust outlet that can overstress an airframe passing thru up to about 4000′.  (There is a similar lower level item at the Bass Gas plant near Nyora). As it is grid demand generated there are no fixed hours of use, thus cannot be notified by NOTAM. Original suggestion to RAPAC was to make it a "D" area, we have pushed for "Restricted".

I have a severe problem with the mechanics of this (a short stack – or  even a pair of short stacks –  producing extreme turbulence at 4,000 ft). What is the maximum electrical power output of the power station and what fuel is used?

Response:

– Hide quoted text — Show quoted text – <snip As an aside, near the main ML runway centreline they are installing – I think at about 15 DME – a power station to backup the electric grid for Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian Brian,  you’re not talking about the Newport Power Station – which has been there for yonks – are you? Harold.

No Harold, this is entirely new.  Two plume stacks a short distance apart and the exhausts join to make an invisible high speed exhaust outlet that can overstress an airframe passing thru up to about 4000′.  (There is a similar lower level item at the Bass Gas plant near Nyora). As it is grid demand generated there are no fixed hours of use, thus cannot be notified by NOTAM. Original suggestion to RAPAC was to make it a "D" area, we have pushed for "Restricted". The other issue arising is how many other new items will intrude into our airspace and lomit it for us. As another aside, West Sale CTAF (therefore can be used by non-radio aircraft) will later this year begin testing UAV to FL500.  These are reliant on TCAS, ADS-B …… and radio …. for avoidance.  I am hoping we will not get a request at RAPAC for West Sale to become a "Radio" CTAF. However, the commercial and military push could win if so. PS  I can email you my RAPAC notes on either if you wish more detail. Brian

Response:

<snip As an aside, near the main ML runway centreline they are installing – I think at about 15 DME – a power station to backup the electric grid for Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian

Brian,  you’re not talking about the Newport Power Station – which has been there for yonks – are you? Harold.

Response:

Good news for the airfield users but watch out for any expansion of the tank training area infringing the missed approach etc at Port Ag (I’m not a visitor there so unfamiliar with the proximity of the tank area and airstrip). The expanded tank training area will be the 1800 square km area of pastoral land NW of Whyalla. The closest it will get to Pt Augusta itself is about 25km. Being a live fire area, I think it will be well marked. Cheers David

David 25 Km will hopefully be OK. However, it’s not so much whether it is well marked or not. The R352 tank firing area is about 9 Nm from Mangalore but affects the missed approach for IFR when R352 is active which will be about 50% of the time. It is unfortunate but if you look at the amount of Oz airspace that is MIL and compare it to the amount of MIL firing and flying that occurs with our depleted defence force reserves, something does not jell. East Sale airspace is bigger than the Melbourne CTR – with Tullamarine, Essendon and international traffic. Go overseas to the US and you find CTAF next door to USAF bases all existing harmoniously. Main thing for PAG is to make sure the two airspaces do not meet up in time because MIL always wins. As an aside, near the main ML runway centreline they are installing – I think at about 15 DME – a power station to backup the electric grid for Melbourne.  The stacks are quite short but the exhaust which is NOT discernible can cause airframe damage to 4000′ altitude.  So, another bit of our airspace – effectively in the western VFR entry lane – vanishes from our use. Brian

Response: