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 10, 2012 #61

    Dan Thomas

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    The total thrust from that engine (347 to 397 lbs) is about half or two-thirds of what a 150 HP Lycoming piston engine can generate. It won't give you a lot of speed without tiny wings and a really long takeoff roll.


    As far as oxygen at altitude: We're not talking trying to stay conscious here. We're trying to keep the brain working at full capacity. The brain needs a lot of oxygen, and the instant we start climbing it's getting less of it. Flying at night, your eyesight starts to suffer above 5000 feet.

    Here's a good article on the subject:

    Pilots Primer - Oxygen issues for General Aviation pilots - Canadian Owners and Pilots Association

    Dan
     
  2. Dec 10, 2012 #62

    T-51ls1

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    I've lived in a place that was 7200 feet and you do NOT need oxygen. I've also climbed mountains above 12,000 feet with out any oxygen and did just fine. Yes it was noticeable and harder to lets say run, but you will not have mental problems like you guys claim. I would agree with not staying above 15k feet for more then lets say an hour or so. I've seen several videos that show people cruising above 14k feet for hours.
     
  3. Dec 10, 2012 #63

    T-51ls1

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    I might disagree with your idea's on oxygen and elevation but i finally found some math equations to figure out how much estimated thrust a 150hp motor would generate. It came out to 825 almost exatly double the turbojet engine i found. Does make me think about what kind of powerplant i'm going to need to be able to move my aircraft.
     
  4. Dec 10, 2012 #64

    bmcj

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    Living at 7,200 feet (as I did for 4+ years) will acclimatize you to lower oxygen levels (specifically, your red blood cell count will increase). However, any significant increase in altitude over what your are accustomed to will result in a degradation of your faculties, even though it may not be obvious to you. Not only can your mental abilities be slowed or dulled, but your senses will suffer too. Two of the most easily verifiable changes would be your visual acuity, color vision, and night vision... take a breath of oxygen while flying at altitude and you will immediately notice a sharpening of your vision and brightening of colors. If it is at night, you will notice the lights becoming brighter and the appearance of dimmer lights that you did not see before.
     
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  5. Dec 10, 2012 #65

    T-51ls1

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    I understand that altitude effects the body's ability to function but there is no way its as low as you are suggesting. I was in south carolina for 6 months while in the army for training. I then moved back to wyoming which was 7200 feet and never felt any difference the first couple of days i was there. I've seen so many videos of people cruising at 12k to 14k elevation with no oxygen going accross the country. I just find it very hard to believe that you "need" oxygen above 10k. I guess if you want to wear it at such a low altitude thats the pilots call if its avalible. I wonder if being physicily fit differe's in effect from person to person?
     
  6. Dec 10, 2012 #66

    bmcj

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    Not saying you can't operate safely at altitude, just that you will be less than 100%.
     
  7. Dec 10, 2012 #67

    T-51ls1

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    Ok well that's all i was trying to say! The other people posting were giving the impression that you can't operate at any altituted above something like 10k without oxygen. I'm most likely going to build a prop plane with a piston engine and i wouldn't want to go much higher then 12k just cuz of the power loss mostly.
     
  8. Dec 10, 2012 #68

    bmcj

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    Just keep in mind that some aviation accidents were caused by the pilot being at less than 100%.
     
  9. Dec 10, 2012 #69

    T-51ls1

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    That's understandable. Accidents of any kind are generally always caused by people either not paying attention or not being 100%. Just the risk of doing anything in my opinion. As for me right now i'm just trying to learn more about flight and how certin airfoils work. Along with all other aspects of flying.
     
  10. Dec 10, 2012 #70

    Dana

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    Oxygen: Yes, there is a wide variation between individuals, but the FAA has established a legal requirement for oxygen as anything above 14,000' at all times for pilot and passengers and anything more than a half hour above 12,500' for the pilot. Most of the regulations aren't arbitrary; they were, as is sometimes said, "written in blood" through hard experience. As said above, oxygen deprivation is insidious, precisely because you're impaired you don't notice that you're impaired. Also, climbing a mountain gives you more time to acclimate than climbing in an airplane.

    On HP and thrust: The thrust produced by a turbojet engine remains essentially constant regardless of airspeed. The thrust produced by a propeller varies widely depending on speed, and a propeller will give maximum efficiency at the airspeed it's designed for, less at other airspeeds. Constant speed (adjustable pitch) propellers can help, but the range is still limited.

    In aeronautical engineering, we speak of two types of horsepower: Shaft horsepower, which is the engine's rating (e.g. the 150HP Lycoming you mentioned), and thrust horsepower, which is the engine's shaft horsepower multiplied by the propeller efficiency (say 80% as an optimistic example).

    Thrust horsepower THP = TV/550 where T (thrust) is in lbs, V (velocity, airspeed) is in ft/s, or THP=TV/375 where V is mph. So your 150HP Lycoming, assuming 80% propeller efficiency, would produce 450# thrust at 100 mph, 225# at 200 mph, 150# at 300 mph, etc. The 825# figure you quoted above would be all the way down at 55 mph. This assumes that the prop has the same 80% efficiency at all these speeds, which is not the case... a prop optimized to make 825# at 55 mph will probably make near zero thrust at 300 mph, and a prop optimized for 300 mph will perform very poorly at 55 mph takeoff speed. Most props are a compromise, and as I said a variable pitch prop increases the useful speed range, but there are still limits. From this you can see that a turbine engine producing, say, 300# thrust would have poor performance at low speeds (which is why jets typically require long runways) but far better than the piston engine at high speed.

    -Dana

    "The difference between death and taxes is death doesn't get worse every time Congress meets." -- Will Rogers
     
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  11. Dec 10, 2012 #71

    jlknolla

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    There have been a few successful turbine-powered one-off experimentals, do a search for 'bo case t-33' and 'homebuilt panther'. I don't recall Mr. Case's educational or professional background, but the jet flew, and flew nicely although it was reportedly awful thirsty, and awful noisy - used a single Turbomeca Marbore from the T-37 as I recall. There is also a successful flying scratch-design semi-scale F9F Panther.

    Both are 2-seaters, both are, I believe, composite construction, and both are, I think, powered by surplus Korean war vintage jet trainer engines.

    There have also been a few reasonably successful conversions of the T-58 turbine engine (powers certain military helicopters) into turbojets by removing the power section, adding a simple throttlable fuel control and fabricating a nozzle - although these have atrociously high fuel consumption. Search on 'EZ-Jet' I think.

    Don't let the nattering nabobs of negativity keep you from further examining your idea. The world is full of successful homebuilt designs that were once nothing but a scratch on a napkin - and contrary to popular belief, if you are willing to seek and accept help when needed, I believe anybody can create the plane of their dreams. There are great resources out there with respect to aerodynamics, materials, CAD, etc.

    Designing and building any aircraft is a challenge, and the scope of such an undertaking is one most folks don't fully appreciate until they are hip deep in it, but it most certainly can be done.

    That said, if one really just wants a cheap jet to knock-around in, the Aero-Vodochody L-29 Delfin, Jet Provost, Iskra and the like can be had for less than you would probably spend to build anything - but they will drink you out of house and home, as will most anything with an engine you can afford/acquire.

    I always thought that Case was onto something good with his T-33, nice lines, decent size, easy build (relatively speaking), decent performance as I recall, and a very forgiving wing design. Kinda wish he would have kitted it.
     
  12. Dec 10, 2012 #72

    T-51ls1

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    Thanks for the advice on the difference between prop hp and thrust. I found a couple sites explaining a little bit about it but not as good as what you did. So if i can get an engine that can create around 400lbs of thrust then it should do fairly well once i get off the ground then? I'm going to keep looking for engines as i save up money and see what comes out at that point. I've seen a video of the scaled f9f panther and that thing looks like a blast to fly! I think the more i read into these turbine engines the more i'm going to have to have a wet wing design so i can carry enough fuel to have a decent flight time. Luckily for me most commerical airlines have wet wing design so i'm going to learn more detail about how their are built in the furture at school.
     
  13. Dec 10, 2012 #73

    cluttonfred

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    Just in case deskpilot's post got lost in the kerfuffle, let me point out again that the Aerosports Archon SF1 seems pretty close to what T51ls1 had in mind.

    Screen Shot 2012-12-10 at 9.02.14 PM.jpg

    [video=youtube;ZVMSgwa46S8]http://www.youtube.com/watch?v=ZVMSgwa46S8[/video]

     
    Last edited by a moderator: Mar 20, 2019
  14. Dec 10, 2012 #74

    T-51ls1

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    I looked at that plane and i thought it was pretty cool no doubt! I want something a little more then that. Once i get a CAD program and learn it i'll start drawing stuff up to show what i mean.
     
  15. Dec 10, 2012 #75

    karoliina.t.salminen

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    When we were flying over Rocky Mountains towards Europe at in between 12000 and 14500ft, we were saving oxygen so that only PIC used oxygen. I copilot side on that leg and I felt happy that I did not have to land the plane. I was feeling quite ok and oximeter was not showing too bad signs but clearly I not feeling even nearly 100% sharp, and that is when mistakes can start to happen. When piloting plane, mistakes are not forgiven and consequences can be severe. And it took longer to recover from this oxygen deprivation than there was time left on approach. Flying to even higher altitude without oxygen is a bad idea.
     
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  16. Dec 10, 2012 #76

    Hot Wings

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  17. Dec 11, 2012 #77

    T-51ls1

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    Since we've been talking about elevation. What kind of oxygen system's are out there for homebuilder or small planes? Would you use something like an oxygen tank with a mask on or is there like some kind of cycle system with tanks?
     
  18. Dec 11, 2012 #78

    Topaz

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    Ask and you'll receive: Oxygen Systems from Aircraft Spruce
     
  19. Dec 11, 2012 #79

    Radicaldude1234

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    Peter Garrison, of Melmoth 2 fame, uses welding oxygen. Which he hooks up to an oxygen system. I'd personally be worried about what else is in those bottles other than oxygen, but it seems to work for him. Good description of the system on his blog, though.:


    Slouching toward airworthiness
     
  20. Dec 11, 2012 #80

    nerobro

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    Everything you're typing here sounds like a serious (read: military) aircraft. Fuel is heavy, and dense. If you need wet wings, versus "wing tanks" you're in a totally different class of plane.

    This really sounds like a very dangerous airplane. By the time you have a plane that can fly 350kts, that can cruise at 300. On reasonable power, you also have a plane that's going to have a really high stall speed.

    With a 300knot cruise, you're not looking at much of a dive before you are knocking on the door of compressibility. When you get in that region, really strange things start to happen. CoP moves, far, and fast.

    I don't see this plane being easy to fly. Being small makes it close coupled. Short wings will make it difficult to segregate sections of wing to ensure a smooth, or controllable stall. You'll also need to consider what wing wash will do to the tail surfaces.

    At lower altitudes, piston engines have a huge fuel economy benefit. Also, their fuel needs on the ground are much much smaller. With a small jet, you can burn frightening portions of your fuel supply just rolling around taxiways. The altitudes you're looking at, do not lend themsleves to jets. Why are you focused on them?

    I'm going to try to re-direct the discussion a bit. Are you looking for a time compression device, or something to play top gun with? A time compression device, means less manuverability, high altitudes, and big fuel capacity. Something to play top gun with, would lead more towards something like a Extra 300.
     

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