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#41
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"Newps" wrote in message ... wrote: If gelling of Jet-A were a problem, airliners would be falling out of the sky on a regular basis. It is a problem. It is solved by heating the fuel. .... and since hydraulic fluid needs cooling they locate the hyd.cooling coils inside the fuel tank(s). That helps solve two problems. |
#42
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Excerpted from other posts.......
Any talk about Jet-A jelling sounds....bogus.. If gelling of Jet-A were a problem, airliners would be falling out of the sky on a regular basis. It is a problem. It is solved by heating the fuel. It is a problem on long flights at high altitudes and high latitudes. The fuel filters on the Boeings that I flew were heated to prevent the screens from "waxing" over. The fuel itself was not heated. The filters were heated with hot engine bleed air and heated for one minute every thirty minutes when the fuel temperature dropped below zero degrees celsius. At PanAm, we had three procedures for dealing with extremely low temperatures across the North Atlantic. 1. Re-route to a more southernly (warmer) route. 2. Reduce altitude to a warmer OAT. 3. Increase speed for a greater friction effect on the tanks. At around M.80, the Ram Air Temperature is about thirty degrees higher than the True Air Temperature. All of these required extra fuel of course and we depended on the Dispatcher providing a good Temp Aloft forecast. Bob Moore ATP B-707 B-727 PanAm (retired) |
#43
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Aha,
But much of the cost is due to changing components other than the engine. If you had a glass cockpit, and fuel system that were compatible to start with, then all you would need to change was the engine, mount, prop, sending units, and software. That would seem to be less than what the europeans are giong through to put the Theilert in a skyhawk. wrote in message ... In rec.aviation.owning Mike Rapoport wrote: wrote in message ... In rec.aviation.owning Mike Rapoport wrote: The Caravan has a 940hp engine flat rated to 675hp. Turbines are typically flat rated so that the engine can make rated power to reasonable altitudes and temperatures without having to design the gearbox for the full thermodynamic horsepower. To keep the comparison with piston engines apples to apples you need to use thermodynamic ratings. http://www.pwc.ca/en/3_0/3_0http://w.../3_0_2_1_2.asp OK, that explains that. To put some numbers on things, the engines in my MU-2 have a specific fuel consumption of .55lb/hp/hr and a piston engine is about .45 and diesels can be under .40. Huge (ship) diesels can be under .30. Compare your model aircraft engines with the TFE731-60 used on the Falcon 900EX which uses .405lb/lb thrust/hr Aha, numbers! So if one assumes the motivation to switch from a piston to a turbine is the price of gas is roughly twice Jet-A, the crossover point would be a turbine that did about .8 (to allow for the weight difference in the fuels). Any idea how small (in appropriate terms of hp) current technology can make a turbine with that consumption? -- Jim Pennino That would be the economic crossover point if the engines cost the same. Of course a plane that needed twice the fuel (in lbs) to achieve the same performance wouldn't have much useful load or range. Dropping a diesel in an airplane costs a bunch. The justification is the cost is recovered in lowered fuel costs. Your second point is certainly valid though and a minor problem with the diesels according to the AVweb article on them. -- Jim Pennino Remove -spam-sux to reply. |
#44
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#45
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wrote in message
... If gasoline hadn't risen to twice the price of Jet-A (at least in parts of Europe) 3 times. At least for avgas. Paul |
#46
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Howdy!
In article , Roy Smith wrote: In article , ) wrote: Think of it this way - a model airplane engine can be made to run with 1/20 of a cubic inch (.049 cu inch to even .010 cu inch), but piston engine aircraft became impractical above a few thousand HP. That is the range of practicality for a piston concept. It is certainly possible to build much larger piston engines than that. How about http://www.bath.ac.uk/~ccsshb/12cyl/ But it is a *little bit* impractical as an *aircraft* engine... yours, Michael -- Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly | White Wolf and the Phoenix Bowie, MD, USA | Tablet and Inkle bands, and other stuff | http://www.radix.net/~herveus/ |
#47
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Roy Smith wrote:
It is certainly possible to build much larger piston engines than that. How about http://www.bath.ac.uk/~ccsshb/12cyl/ Ah! I've always wondered how that Antonov 225 Mrija was powered... Stefan |
#48
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Mike,
TCM IO-520/550's running LOP are about .39-.40 BPSC according to the GAMI folks, the SEMA engine is about .33-.35 from their specs. At 70K for their engine conversion and the cost of JetA being within 10% of the cost of 100LL at most GA airports I ageree with you and don't think we'll see a lot diesel's in the near future. The Diamond Twin really impresses me, can' t wait for an independent (non-Flying or other slick mag) pilot report to see how it really does. Ernie BE36 E-160 KDVO "Mike Rapoport" wrote in message k.net... The Caravan has a 940hp engine flat rated to 675hp. Turbines are typically flat rated so that the engine can make rated power to reasonable altitudes and temperatures without having to design the gearbox for the full thermodynamic horsepower. To keep the comparison with piston engines apples to apples you need to use thermodynamic ratings. http://www.pwc.ca/en/3_0/3_0http://w.../3_0_2_1_2.asp To put some numbers on things, the engines in my MU-2 have a specific fuel consumption of .55lb/hp/hr and a piston engine is about .45 and diesels can be under .40. Huge (ship) diesels can be under .30. Compare your model aircraft engines with the TFE731-60 used on the Falcon 900EX which uses .405lb/lb thrust/hr Mike MU-2 wrote in message ... In rec.aviation.owning Mike Rapoport wrote: About the size of the Caravan 900hp+ Mike MU-2 According to the Cessna website, the current Caravan is 675hp. -- Jim Pennino Remove -spam-sux to reply. |
#49
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#50
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In rec.aviation.owning Pete Zaitcev wrote:
On Fri, 17 Sep 2004 12:13:49 -0700, wrote: A gas turbine scales up easily and but is nearly impossible to scale down. The auto manuacturers found that out in the 1940s - remember the "car of the future" on the covers of Popular Science et al? Turbines for cars are further away now than they were 55 years ago. The turbine suffers from excessive fuel consumption at part throttle (the piston engine is incredibly flexible that way)and in smaller HP installations. [...] This is not my recollection. What killed auto turbines was their spool-up and spool-down time, and gearboxes for 20,000 RPMs. BTW, remember the rail engines. The turbines there tried to compete well into 1960s. They were killed by their short overhaul time, not fuel consumption. -- Pete According to a guy I worked with who worked on the Chrysler turbine car, the problem that was the straw that broke the camel's back was the under the hood temperature being too high for all the other stuff under the hood, i.e. wiper motors, relays, etc. -- Jim Pennino Remove -spam-sux to reply. |
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