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Post by beagle on Mar 9, 2013 16:40:41 GMT 12
yes, but I am wondering if hte interior pressure rises as the higher you get as well. I would think there would be a limit to as much as you pressurise it up to. Mr Mc Fly would be the expert here, unless mr Lockheed is here on the forum.
I am wondering if that cessna did more flights today as I saw one come in from the south about 5pm, maybe 4 30ish
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Post by suthg on Mar 9, 2013 19:07:06 GMT 12
Speaking from an engineering background, I would imagine as you gain more altitude and the external air pressure lowers, then there will be more leakage and an inability to cope is reached so the internal cabin air pressure may start lowering even though any compressor may be working at it's limit - hence a slight lowering below normal GL atmospheric or equivalent altitude say 3000ft that they try and achieve, would occur - totally unnoticed by the flight crew - once you reach a certain limiting altitude, which will be different for each craft due to differing losses, one from another. Once beyond that, the cabin air pressure will trend down with further climbing.
For some aircraft, it will be the performance of the engines (and props) that will indicate a drop off in the performance envelope and limit the maximum recommended altitude to fly at.
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furd
Flight Lieutenant
Posts: 71
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Post by furd on Mar 9, 2013 19:09:31 GMT 12
yes, but I am wondering if hte interior pressure rises as the higher you get as well. I would think there would be a limit to as much as you pressurise it up to. Mr Mc Fly would be the expert here, unless mr Lockheed is here on the forum. I am wondering if that cessna did more flights today as I saw one come in from the south about 5pm, maybe 4 30ish I'm trying to recall the cabin differential pressure for the C130H which I think was about 6.5 psi, no doubt someone who is current on the aircraft will confirm that. From memory sea level cabin altitude could be maintained to FL180. As with all aircraft pressurization systems you can climb maintaining sea level cabin altitude until you achieve max operating differential pressure and the cabin altitude will then climb as the aircraft altitude increases. In practice the cruise altitude is set on the pressurisation system prior to t/o and the cabin rate of climb is adjusted to a rate of 500 fpm for climb so that ideally the aircraft altitude, the cabin altitude and max operating diff all arrive at the same point. For descent the system is set to the destination field altitude and cabin is descended at a rate of no greater than 300 fpm so the cabin is at field altitude on landing when the outflow valve(s) automatically open. (500/300 fpm is the maximum allowable rate of change for pax carrying aircraft)
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Post by beagle on Mar 9, 2013 19:13:29 GMT 12
didn't get to 6th form to do phycis or how you spell it but cheers, more or less understand all that
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Post by davidd on Mar 10, 2013 9:54:29 GMT 12
All published specifications on C-130s agree that the normal service ceiling for the C-130H is about 28,000 feet with max load 42,000 lb, and 33,000 feet maximum at unspecified weight. Presume latter is a practical limit for normal operations, with much lighter payload, and taking into account the pressurisation system and probably other technical considerations. However the small PR postcards put out by the RNZAF in the 1990s clearly state that "our" C-130Hs have a ceiling of 42,000 feet (12,802m) so why our aircraft are so different raises the question of why our aircraft are so superior to everybody elses! A result of one of the upgrades perhaps? Where our our C-130 experts? Perhaps answer is that the published specifications normally stated are deliberately conservative and actual operation beyond these figures are at the discretion of the user? Still it seems a large jump to me. Normally aircraft never operate at their "absolute" ceiling because nothing is to be gained by it, and stress may be placed on various structural and other elements. David D
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Post by Ykato on Mar 10, 2013 10:15:19 GMT 12
All published specifications on C-130s agree that the normal service ceiling for the C-130H is about 28,000 feet with max load 42,000 lb, and 33,000 feet maximum at unspecificied weight. Presume latter is a practical limit for normal operations, with much lighter payload, and taking into account the pressurisation system and probably other technical considerations. However the small PR postcards put out by the RNZAF in the 1990s clearly state that "our" C-130Hs have a ceiling of 42,000 feet (12,802m) so why our aircraft are so different raises the question of why our aircraft are so superior to everybody elses! A result of one of the upgrades perhaps? Where our our C-130 experts? Perhaps answer is that the published specifications normally stated are deliberately conservative and actual operation beyond these figures are at the discretion of the user? Still it seems a large jump to me. Normally aircraft never operate at their "absolute" ceiling because nothing is to be gained by it, and stress may be placed on various structural and other elements. David D Seems to Vary with each fact sheet: Service Ceiling 10,770 m (35,335 ft) www.rcaf-arc.forces.gc.ca/v2/equip/cc130/specs-eng.aspService Ceiling: 30,000 feet www.mindef.gov.sg/imindef/mindef_websites/atozlistings/air_force/assets/aircraft/Helicopters_and_Transport_.htmlService Ceiling: 33,000 feet www.uscg.mil/hq/cg7/cg711/c130h.aspCeiling 42,900 ft 13,075 m www.military.cz/usa/air/in_service/aircraft/c130/c130_en.htmCeiling: C-130J: 28,000 feet (8,615 meters) with 42,000 pounds (19,090 kilograms) payload C-130J-30: 26,000 feet (8,000 meters) with 44,500 pounds (20,227 kilograms) payload. C-130H: 23,000 feet (7,077 meters) with 42,000 pounds (19,090 kilograms) payload. C-130E: 19,000 feet (5,846 meters) with 42,000 pounds (19,090 kilograms) payload www.af.mil/information/factsheets/factsheet.asp?fsID=92Ceiling 40,000 feet www.airforce.gov.au/Technology/Aircraft/C-130J_Hercules/?RAAF-EPzAnXmgjWuyTq8XSZbcAUaUIYIcntiBOperational altitude Sea level - 12,802m (42,000ft) www.airforce.mil.nz/about-us/aircraft/hercules.htm
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furd
Flight Lieutenant
Posts: 71
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Post by furd on Mar 10, 2013 12:28:04 GMT 12
All published specifications on C-130s agree that the normal service ceiling for the C-130H is about 28,000 feet with max load 42,000 lb, and 33,000 feet maximum at unspecificied weight. Presume latter is a practical limit for normal operations, with much lighter payload, and taking into account the pressurisation system and probably other technical considerations. However the small PR postcards put out by the RNZAF in the 1990s clearly state that "our" C-130Hs have a ceiling of 42,000 feet (12,802m) so why our aircraft are so different raises the question of why our aircraft are so superior to everybody elses! A result of one of the upgrades perhaps? Where our our C-130 experts? Perhaps answer is that the published specifications normally stated are deliberately conservative and actual operation beyond these figures are at the discretion of the user? Still it seems a large jump to me. Normally aircraft never operate at their "absolute" ceiling because nothing is to be gained by it, and stress may be placed on various structural and other elements. David D The RNZAF received the first 3 C130H's to come off the production line. This model with considerably more powerful engines and improved outer wings compared to the C130E had a much improved performance envelope. Engine torque for t/o was airframe limited which meant for hot climate t/o's and climb we could still achieve our max power settings up to about 30 degrees ambient temperature. I should mention the Ozzies with their E's were envious of our improved performance as they were on occasions runway limited where we were not. With this improved performance we could achieve higher altitudes for weight and cruise at 300kts true. In the initial few years the cruise was predicated on an engine power setting of 1010 TIT, however this was reduced to 970 TIT to preserve engine life. It doesn't take a rocket scientist to work out with this reduced power setting and to maintain a 300KT true cruise a lower cruise altitude is the penalty. I would suggest the service altitude being quoted on this thread is based on the lower cruise power settings and the lack of pax oxygen in the event of a rapid decompression. The aircraft is certainly capable of much more.
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Post by baronbeeza on Mar 10, 2013 12:56:52 GMT 12
cc-130j.ca/records-en/NEW RECORD Country USA Altitude 36,560 feet Aircraft Lockheed Martin C-130J Date 4/20/99 Details Breaks old record by 18 percent while carrying twice the payloadBREAKS these existing records: Altitude with following payloads: 0 kg; 1,000 kg; 2,000 kg; 5,000 kg; 10,000 kg ESTABLISHES these records: Altitude with 15,000 and 10,000 kg payloads
Did the RNZAF ever consider going for some of these records. I know the F-27 did something with endurance.
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Post by phil82 on Mar 10, 2013 15:41:47 GMT 12
Alright, so there you are in your C130H, happily whizzing along at 30,000 with 40 or so baggies in the back, over hostile territory, Auckland say, and you lose cabin pressure, how long would it take to descend to a breathable altitude?
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Post by jonesy on Mar 10, 2013 15:53:32 GMT 12
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Post by beagle on Mar 10, 2013 16:57:37 GMT 12
Alright, so there you are in your C130H, happily whizzing along at 30,000 with 40 or so baggies in the back, over hostile territory, Auckland say, and you lose cabin pressure, how long would it take to descend to a breathable altitude? A plane full of avionics hey
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furd
Flight Lieutenant
Posts: 71
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Post by furd on Mar 10, 2013 18:31:21 GMT 12
Alright, so there you are in your C130H, happily whizzing along at 30,000 with 40 or so baggies in the back, over hostile territory, Auckland say, and you lose cabin pressure, how long would it take to descend to a breathable altitude? A consideration with any rapid or explosive decompression is structual integrity. If the aircraft is damaged then the slow speed gear down descent is carried out limited by the gear extended speed which in the case of the C130 is 145KTS from memory. this would take 6-8 minutes from FL300 to 10000 ft. A clean high speed descent (Vmo) about 3-4 minutes. I can recall doing one or two practice emergency descents in the aircraft from FL 350 and the initial push over to reach Vmo gives an estimated ROD of 10-12000 fpm for a very short period then settles at 6-8000 fpm at Vmo although this is not readable as the vert speed indicator is limited to -6000 fpm. For interest here is the useful consciousness table from my AirNZ safety procedures notes: FL 200 5-10 minutes FL 250 3-5 minutes FL 300 1-2 minutes FL 350 20-30 secs FL 400 9-15 secs
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Post by flyjoe180 on Mar 12, 2013 11:53:56 GMT 12
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Post by Ykato on Mar 17, 2013 10:27:36 GMT 12
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Post by baronbeeza on Mar 17, 2013 10:44:57 GMT 12
Just started it's descent. I have another pic taken a minute or so earlier also.
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Post by baronbeeza on Mar 17, 2013 11:22:36 GMT 12
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Post by Dave Homewood on Mar 17, 2013 11:34:56 GMT 12
So what is the answer to Beagle's question?
Is the highest this jet thing you're screenshotting?
Did the Hercules really achieve 43,000 feet??
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Post by baronbeeza on Mar 17, 2013 11:49:20 GMT 12
So what is the answer to Beagle's question? Is the highest this jet thing you're screenshotting? Did the Hercules really achieve 43,000 feet?? I am not so sure about the C-130 and the ceiling there. A couple of ex 40 Sqdn members here seem to think the Herc can get up there amongst it. I know I was in a Blunty at 39,750 ft. It would seem that we now have a serious contender at 45,000 ft. Proof just in today of a C152 getting along at that altitude. """""Cessnas of some sort (they're all the same anyway) """"""""' Until someone from 14 Sqdn chimes in with a story about the Canberra days this is it for now I believe. Can anyone beat 45,000 ft ? I am almost tempted to get out and dust off the Tomahawk.
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Post by beagle on Mar 17, 2013 16:09:17 GMT 12
What sort of max heights did the Skyhawks get up to
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Post by ngatimozart on Mar 18, 2013 1:18:42 GMT 12
Cool. Thanks for that. I use Firefox and have found an addon that does the same job at addons.mozilla.org/en-US/firefox/addon/fireshot/ The pro version does a lot more and you get a thirty day free trial, so I've just installed it and taken advantage of the free trial. The attachment is an image I took of the Fireshot addon page and I haven't altered it in any way. Attachments:
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