pj8768 Posted October 28, 2012 Share Posted October 28, 2012 There were plenty of vapour trails along SE Australia today. Anyone know the cause/s and significance? Link to comment Share on other sites More sharing options...
Guest Howard Hughes Posted October 28, 2012 Share Posted October 28, 2012 Cause = water vapour Signifcance = little Unless you ask the tin foil hat brigade! Link to comment Share on other sites More sharing options...
damkia Posted October 28, 2012 Share Posted October 28, 2012 Cause = water vapourSignifcance = little Unless you ask the tin foil hat brigade! Until you look at the significnt changes in weather noted by the US authorities during the grounding of all aviation in the weeks after 9/11. Apparently the contrails (vapour trails) are responsible for seeding a lot of cloud formations across America Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2012 Share Posted October 28, 2012 There were plenty of vapour trails along SE Australia today. Anyone know the cause/s and significance? We see condensation trails when the air thru which the aircraft is passing has just the right humidity. At the altitude of the jet trails we see, the air is often around -50 C and can't absorb much water vapour. Burning jet fuel adds water to the air, raising the local humidity. Initially superheated in the exhaust gas, a few metres after it leaves the engine this gas has cooled enough to condense, creating a visible jet trail. If the air is very dry, this may evaporate after a few seconds; the jet trail disappears again. In humid air the trail persists, gradually widening as the wake turbulence disperses it. Although jet engines are normally associated with condensation trails, any burning of hydrocarbons could do the trick. Survivors of WWII report often seeing the contrails of American bombers. After unloading over German targets during day raids they would often steer a northerly route home, passing close enough to reach neutral Sweden if their battle damage prevented them from making it home to Britain. Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted October 28, 2012 Share Posted October 28, 2012 Just finished a great book called 'Rocket Fighter' by former pilot (and survivor !) Mano Ziegler. It tells the fascinating story of the rocket powered Me 163 'Komet' that the Germans used towards the end of WW2, with mixed success. The 2000 Hp produce by the acid- burning rocket shot them across the field where they jettesoned the main landing gear, they then went straight up to the high cruising altitudes of the US B-17 bombers. The rocket motors were not noted for their reliability, but observers on the ground knew they had a successfull launch when they saw the vertical contrail heading upwards, toward the contrail producing bombers........A highly recommended read, and there is also some great wartime training footage showing operation of these very first supersonic jet fighters...google Me 163.......................................................Maj... Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2012 Share Posted October 28, 2012 Would like to read that, Major. There are a millions of great stories to come out of that war. Are you sure the Me-163 went supersonic on the way up to the bombers? It would have had to handle all the buffeting and control issues mastered by later sound barrier claimants like Chuck Yeager. Brave, fanatical or just plain terrified cannon fodder, those rocket pilots had short life expectancy. I knew a former Bf-109 pilot who told me of their desperate battles to stop the bombers late in the war, including one time there were no ground crew to start his engine. The little bloke had to wind up that 1700hp monster's flywheel starter by hand, before jumping off the wing, running around thru snow, climbing up and stowing the crank handle, hoping the damn thing would start, before joining up with others in climbing to 20,000 feet or so to attack swarms of bombers. Our lives have other challenges... Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted October 28, 2012 Share Posted October 28, 2012 G'day Old koreelah, The Me 163 komet pilots did have problems with compressability causing loss of control at high altitude, after control reversals. One pilot is reputed to have broken the sound barrier on the way down, registering a speed way above what was required to break the sound barrier at that altitude. That would put it a good three years ahead of Chuck, not that I want to take anything away from that fine effort in 1947. Additionally a British pilot operating in the Darwin area during the war, was reported to have created 'sonic booms' in a diving Spitfire. Interesting also is the fact that after capturing several 'komets' after the wars end, the yanks never did any rocket powered flights in the US, preferring instead to tow them to altitude and then glide them to a landing. This is also how the germans trained the rookie pilots in them. The fuel used in the Komet was incredably dangerous, and accounted for many of the pilot losses as it simply disolved flesh, or anything else organic after contact. A really great read, and very well written by a survivor who was in the thick of it all.....................................................................Maj... Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 28, 2012 Share Posted October 28, 2012 ... after capturing several 'komets' after the wars end, the yanks never did any rocket powered flights in the US... Probably couldn't get any volunteers... Link to comment Share on other sites More sharing options...
Sapphire Posted October 29, 2012 Share Posted October 29, 2012 Probably couldn't get any volunteers... Volunteers can be "arranged". Link to comment Share on other sites More sharing options...
facthunter Posted October 29, 2012 Share Posted October 29, 2012 Vee haf vays of making zem fly. Good comment OK. (about the contrails). Polar regions and high altitudes are very low humidity places. Nev Link to comment Share on other sites More sharing options...
eightyknots Posted October 29, 2012 Share Posted October 29, 2012 G'day Old koreelah, The Me 163 komet pilots did have problems with compressability causing loss of control at high altitude, after control reversals. One pilot is reputed to have broken the sound barrier on the way down, registering a speed way above what was required to break the sound barrier at that altitude. That would put it a good three years ahead of Chuck, not that I want to take anything away from that fine effort in 1947.Additionally a British pilot operating in the Darwin area during the war, was reported to have created 'sonic booms' in a diving Spitfire. Interesting also is the fact that after capturing several 'komets' after the wars end, the yanks never did any rocket powered flights in the US, preferring instead to tow them to altitude and then glide them to a landing. This is also how the germans trained the rookie pilots in them. The fuel used in the Komet was incredably dangerous, and accounted for many of the pilot losses as it simply disolved flesh, or anything else organic after contact. A really great read, and very well written by a survivor who was in the thick of it all.....................................................................Maj... Wow, that's an interesting aviation history snippet. I never heard of the sonic boom Spitfires until now. I wonder how much above the aircraft's VNE that was?? Link to comment Share on other sites More sharing options...
dodo Posted October 29, 2012 Share Posted October 29, 2012 The Komet was used in a speed record attempt. They towed it up to altitude behind a Me110, then it separated, lit the rocket, hit a bit over 1000km/h, and encountered severe mach buffet (flutter on the trailing edge of the wing - I think it lost a few bits off the wing in the process), but if I recall, survived. Definitely not mach capable without destructive damage - although possibly survivable. Fuel was RFNA (Red Fuming Nitric Acid) and a hydrogen peroxide of some sort. Either would dissolve the pilot. The two fuels were hypergolic meaning they ignited (exploded) on contact with eachother. I have a friend whose father came out to Oz working with an English aircraft firm at WRE and Woomera, with a pile of Walter engines from the Komet and Natter programs. Even test firing the engines the engines remotely from behind a concrete wall, they lost several people. If the motor misbehaved, or didn't fire, they had a mirror to look over the wall with. They got careless over time, and with a misfired motor, stood and peered over the wall one day. The motor exploded and removed their heads. Not very cheery, but fascinating, which is possibly why they killed so many people experimenting and using them, dodo Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 29, 2012 Share Posted October 29, 2012 Wow, that's an interesting aviation history snippet. I never heard of the sonic boom Spitfires until now. I wonder how much above the aircraft's VNE that was?? A number of piston/prop aircraft tickled the sound barrier in dives during that era, and men died. The younger Geoffrey De Havilland was killed by sonic buffeting in an early jet. "Going where no-one has gone before" has its risks. Regarding VNE, I've found a simple formula to calculate a home-designed aircraft's VNE, but when I applied it to my modified Jodel I got something in excess of 130kt, which I don't intend to ever go near. Link to comment Share on other sites More sharing options...
eightyknots Posted October 29, 2012 Share Posted October 29, 2012 A number of piston/prop aircraft tickled the sound barrier in dives during that era, and men died. The younger Geoffrey De Havilland was killed by sonic buffeting in an early jet. "Going where no-one has gone before" has its risks.Regarding VNE, I've found a simple formula to calculate a home-designed aircraft's VNE, but when I applied it to my modified Jodel I got something in excess of 130kt, which I don't intend to ever go near. Does your formula throw up different VNEs than the manufacturer's VNEs? Link to comment Share on other sites More sharing options...
boingk Posted October 29, 2012 Share Posted October 29, 2012 VNE can be used to express many conditions which will make an aircraft unsafe or unflyable at a given speed. Commonly used ones are: Control flutter Control reversal Excess control loads Excess structural loads More rarely they will include limits for sonic buffering or intake velocity for trans sonic craft that cannot breach the sound barrier. The craft we fly are generally limited structurally and by control flutter, which can occur at higher speeds without proper ajustments and weighting of controls surfaces. There is, for example, a Hummel Bird that is regularly flown at 160mph - 20mph more than stated redline. The owner has extensively modified it. The link is here and is an interesting read: http://www.eaa.org/experimenter/articles/2010-02_hummel_bird.asp Cheers - boingk Link to comment Share on other sites More sharing options...
Old Koreelah Posted October 29, 2012 Share Posted October 29, 2012 Does your formula throw up different VNEs than the manufacturer's VNEs? I only applied it to the Jodel D9's VNE. Like anything found on the net, you don't know how authoritative it is, so I am very happy to stick with the original designer's limit of 100kt. Link to comment Share on other sites More sharing options...
Gnarly Gnu Posted October 29, 2012 Share Posted October 29, 2012 Fuel was RFNA (Red Fuming Nitric Acid) and a hydrogen peroxide of some sort. Either would dissolve the pilot. The two fuels were hypergolic meaning they ignited (exploded) on contact with each other. Wow, conc nitric acid is indeed nasty stuff. I seem to dimly recall distilling a small amount once in younger chemistry days, I no longer have yellow nitric stains on my fingers. I understand it is difficult to store as it catches fire to many things on contact and is quite unstable. The Nazi's should have been encouraged to use more of it, they may have disappeared sooner. Link to comment Share on other sites More sharing options...
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