experiamental fighter jet style aircraft

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by T-51ls1, Dec 7, 2012.

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  1. Dec 12, 2012 #101

    DangerZone

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    Flying is dangerous and you have to know what you are doing and be aware of YOUR limits. But nonsense is if you guarantee death and experienced pilots not only survive but fly often to higher altitudes than 5500m without dying. Hypoxia is also quite individual, some people may experience euphoria while others may not. Hell, I even see some forum members here get euphoria with both feet on the ground.
     
  2. Dec 12, 2012 #102

    Topaz

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    If you're flying above 18k'MSL without oxygen, you're obviously not aware of your limits. Yes, there are variations in people's response to hypoxia. But the variations aren't that large, even remotely.
     
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  3. Dec 12, 2012 #103

    DangerZone

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    The only thing that is apparent is that you are full of assumptions. If it makes you feel good, go for it.

    Everyone with sanity will have oxygen on board, that is the right way. But that does not mean everyone WILL HAVE TO USE IT. It is individual, some people have trouble breathing at lower altitudes than 5000m. Some people sail or fly for hours at around 5000m.

    So the only conclusion is that your knowledge is limited in understanding. Otherwise you could understand what I wrote.
     
  4. Dec 12, 2012 #104

    DangerZone

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    If you are flying at 5500m without an oxygen tank, that means you are not only unaware of your limits but stupid. If you are flying without having to use the oxygen tank, that means your body is more tolerant to the lack of oxygen in the nytrogen/oxygen ratio that we as humans breathe. Do people here understand the difference? I am amazed how the threads here go off topic...
     
  5. Dec 12, 2012 #105

    Mark Z

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  6. Dec 12, 2012 #106

    DangerZone

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    That is a good point, and these figures seem like an average. Meaning, some people will have more tolerance and some less.

    Sometimes the euphoria happens on the way down, due to nitrogen. But that is a completely different story and also totally off topic.
     
  7. Dec 12, 2012 #107

    Topaz

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    Unless you're Inca or Sherpa and have dozens of generations of adaptation in your ancestry, nobody's body is tolerant to the degree you suggest. Period. You seem to believe otherwise, but your belief is not relevant, compared to decades of research data that show precisely the opposite to your assertion.

    I agree. So let's knock off this diversion about oxygen and get back on topic.
     
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  8. Dec 12, 2012 #108

    T-51ls1

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    Yes your right sustaining 700hp for a long time is a different story then just pushing it once or twice. If i built an engine to run 700hp at around 5500rpm i would only hit that on take off and at some times when climbing or doing arobatics. Cruise rpm would most likely be around 3k and half the boost pressure so it would be down around 500hp. That hp range on an engine with good solid forged compents will last a good while before need to be overhauled. I have seen a ls1 with a factory bottom rotating asslembly go well over 60,000 miles of hard abuse before finally breaking under a nitrous run. That's jut my experiance with the LS motor's though.
     
  9. Dec 12, 2012 #109

    DangerZone

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    It's a good point, Incas, Sherpas, divers, pilots, mountain people, many of them have a lot in common and are beyond average in adaptation and tolerance.

    So I also agree, I gave examples of 4 airplanes that fit in the topic description so it would really be nice to get back to those instead of human respiration...
     
  10. Dec 12, 2012 #110

    Toobuilder

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    I drive behind an LS3 every day, and I can tell you without a doubt even though it is capable of 450 HP in current form (and sees it sometimes), it spends most of its time at 10% power. Yes, there are 1000 HP LS-3 street cars out there, but their life at that power output is measured in minutes, not hours.

    There are not many bigger fans of the LS engines on this board than me, but squeezing 700 HP continuously out of 6.2 liters is really, really ambitious.
     
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  11. Dec 12, 2012 #111

    Kristoffon

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    Allow me to present a counterpoint.

    If we look at Corvettes, BMWs, Mercedes, and the sort of car that gets a 500hp engine its either of two categories:

    1) a heavy car that will get driven on the autobahn at 300 km/h for god knows how long and how often
    2) a sports car that will get taken to a track where the engine will be at WOT 70% of the time

    You don't hear of Lamborghinis or Corvettes or Ferraris or turbo Subarus and turbo Porsches with 200 hp/litre having engine failures at racetrack events. You can be sure that all those factories give their engines a hell of a beating during testing because if they start to break down not only do they lose their top customers but the brand as a whole gets tarnished. "The engines on SL55 AMGs are breaking all the time I read on the Internet, no way I'm buying this A-class if not even their top of the line product is good". And that's factory original, now think of all those that modify their engines specially the turbos that are trivial to get more power out of, and those still don't break.

    From that I would be willing to bet any of those engines would give out their rated power for 500 hours at the very least because otherwise they wouldn't have enough of a safety margin to guarantee they wouldn't break in 'normal' use. And on the realm of low specific power ones such as a Corvette V8 I'd wager on the 2000 hour ballpark because those are not any different than ordinary ones only bigger and much better built.

    Edit to add that a Wasp Major engine produced 4300 hp according to Wikipedia to 0.99 hp/in³ or about 60 hp/l while being air cooled, and that specific power is on the ballpark of today's modern auto engines. If that was doable 70 years ago I suppose 700 hp out of a 6.2 litre engine today for 500 hours is absolutely expected.
     
    Last edited: Dec 12, 2012
  12. Dec 12, 2012 #112

    deskpilot

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    Mods. I think it's time this threat was renamed as it's no longer about the current title.
     
  13. Dec 12, 2012 #113

    bmcj

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    Sadly, we'd have to rename most of the threads in this forum. Thread drift is unfortunate and notoriously hard to avoid, so I think the moderators' practice of breaking out sections to their own thread or to a more appropriate thread is still the best compromise.
     
  14. Dec 12, 2012 #114

    rv6ejguy

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    Peak hp and maximum continuous hp are pretty different things on air cooled radial engines. The R4360 was not a very reliable engine in service as I know someone who flew them on 4 engined aircraft. Few if any went 500 hours without a bunch of jugs changed. The OEM auto companies validate their modern designs for several hundred hours at full rated power these days before release for production. It is reasonable to expect the better ones to be able to run at 75% power for at least 500 hours assuming you are using the same ignition timing, fuel and AFRs as the OEMs do the testing with ie- conservative and very rich. You might not like the fuel flows...

    Turbocharged production engines regularly exceed 100 hp/L at pretty low revs these days so 70 is easy with long life and reliability with a forced induction, liquid cooled engine. The OEMs have better parts and generally piston cooling oil jets on their turbocharged engines to make them last.
     
  15. Dec 12, 2012 #115

    Topaz

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    This one has wandered drunkenly around since the beginning. If it'll stay on one topic for more than a few posts, we could split it appropriately. :roll:
     
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  16. Dec 12, 2012 #116

    DangerZone

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    Did anyone mention the Javelin Jet..? It isn't exactly a homebuilt but it is a small private fighter like jet...

    1-javelin.jpg
     
  17. Dec 12, 2012 #117

    Toobuilder

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    Theres no doubt that production engines, including the 638HP, 6.2l, LS-9 will run at 100% power for hours on end without acute failure. There are plenty of videos on line showing just that. However, translating that capability into a meaningful aircraft TBO is quite another thing. And then to expect to screw together an engine at home, and then significantly exceed the specific power output of the base engine is not reasonable.

    You bring up the 4360 - that and the turbo compound 3350 were essentially the bleeding edge of piston engine technology. They were the last of the breed before turbines took over, and their reliability was horrible. My father was a 4360 mechanic in the AF, and a pilot flying the 4360 and 3350 afterwards. It was UNUSUAL to return from ANY flight without at least one cylinder change, and in fact, it was not uncommon to see one engine feathered on landing.
     
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  18. Dec 13, 2012 #118

    Kristoffon

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    The Impreza STI spits out 380 hp out of a 4 cylinder engine, I cant find the displacement right now but IIRC it's 2.5l. Lancer EVO gets 360 hp out of what I believe is a 2.0l 4 cylinder. So 152 hp/l and 180 hp/l out of the factory door.
     
  19. Dec 13, 2012 #119

    Hot Wings

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    Just to keep this thread off track:

    In 1989 Subaru took the FIA endurance record for 100,000 Km with an average speed of 138 mph over a period of about 18 days. This kind of illustrates what a stock production modern automobile engine is capable of.

    While searching for a link I ran across a modern version that is even more impressive.

    World 100,000 mile record: 140 mph for 30 days averaging 40 mpg

    100,000 MILES in 30 days. (including oil, filter, and tire changes) 30 days is 720 hours.
     
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  20. Dec 13, 2012 #120

    nerobro

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    Comparing race engines to aircarft engines isn't fair. Race engines spend precious little time at any specific rpm, this means things like resonance don't really come in to play. Also, the faster the car, the less time is spent at full throttle. The mass of the engine and cooling system can handle peak loads, but are unlikely to handle sustained full power runs. "Stock" engines maybe, race engines, are a lot less likely. Even stock engines are on the edge of overcoming their own ability to reject heat from cylinder heads.

    Thread drift is fortunate and necessary. If you only discuss, or answer the question someone ASKS, they will rarely get the answer they NEED. (In my line of work, if I only answered the questions people asked, nobody would ever get their problems solved.)

    Threads are conversations. Conversations take turns, and wander, and explore. That's where real learning, and the changing of minds happens.

    Splitting a thread when the direction changes, means the next person, with the same question, won't be able to follow the discussion to it's conclusion. ;-)
     
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