Ah-1 Cobra Pilot

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About Ah-1 Cobra Pilot

  • Rank
    Full Member

Profile Information

  • Gender
    Male
  • Location
    Lincoln NE
  • Interests
    Flying, duh!
  • Reg #
    N468W
  • Model
    M20J
  1. Denver Post Airport Article

    As you probably know, I like to do math. If those 'five households' all did the same thing, it means that each called 5 times every day! As I like to say, hitmen are cheaper than lawyers.
  2. Newly Overhauled Engine, No Existing Logs?

    How much do you trust the guy who did the overhaul? The engine is worth exactly that much. It is also true for whomever you might sell it to. Personally, unless there are extenuating circumstances, I do not put much trust in someone who gets rid of previous logs.
  3. Would anyone be interested?

    Exactly. Total Drag comprises parasite drag, induced drag, etc. Some are greater at high speeds, some greater at lower speeds. Cars have similar/analogous forces acting upon them, too. Forgive me for not previously spelling everything out in the interest of conserving words.
  4. Would anyone be interested?

    The gear box in a GO-300, for instance is over 90% efficient and weighs about 30 lb., (if memory serves me). It only needs to reduce the rpm from about 3200 to 2400. Those worse figures are probably from turbo props or other high-percentage reduction.
  5. Would anyone be interested?

    No, just as in aircraft, you have several friction/drag curves and the engine has its own efficiency curve. Where these curves meet, essentially, is the best speed vs. fuel burn.
  6. Would anyone be interested?

    You would be trading a gearbox for a generator and a motor. I suspect the weight of the two would be more than the weight of the gearbox; plus, the efficiency losses would make it undesirable.
  7. Would anyone be interested?

    Very interesting. If a hybrid gets better mileage in town than on the highway, this tells you something. The perfect scenario is when an engine's most efficient output is equal to the drag, (combination of friction, aerodynamic drag, etc.), and you are on level ground. All of the engine power is devoted to pushing the vehicle forward; none goes to recharging the battery. A higher speed results in extra power, all devoted to propulsion, not recharge. Since your mileage is better in town, the greater part of energy produced is consumed in aerodynamic drag at the speeds you drive on the highway. An 8 mpg difference is pretty substantial. You must usually drive at least 30 mph above that magic 'best efficiency' speed. This also shows why a hybrid airplane is silly. Most of the distance people normally fly would be at a particular power setting, mostly at or above the point of maximum efficiency, meaning there is no 'waste' power to recharge a large battery bank. The only scenario in which a hybrid might make sense is for a trainer specifically made to stay in the pattern doing T&Gs. Again, using one engine to drive a generator/alternator to drive multiple electric motors can make sense in a quadcopter. It depends on the size of your payload.
  8. Would anyone be interested?

    The only fuel cells I have seen were used in spacecraft. They were one-shot deals, with the benefit that the water could be drunk in an emergency. (It was a nasty looking brown, but people who tried it said it tasted OK.)
  9. Would anyone be interested?

    You are right, I did make a mistake. Let us calculate it again. 125 hp * 1 hour * 3600 s/hr * 746 W/hp ÷ 0.8 ÷ 0.875 MJ/kg * 2.205 lb/kg = 1057 lb of battery to equal 6 gallons of gas , and the C-152 replacement would be 11,370 lb. (This is using the maximum energy density for the battery. If you use the low number, multiply by about 2.4.) [BTW, I had the Sparrowhawk conversion.] As for your link, a 17 kWh battery can only power a 85kW motor for 12 minutes at full power, (114 hp). Their rosy picture is of a one hour recharge. How many 'touch and go's can you do in a day with that? Not much of a replacement for your typical trainer aircraft.
  10. Would anyone be interested?

    They might be doing research, which may be a good expenditure of their time, but I oppose them wasting money, which is worse in that it probably comes from taxes. Ask them what subsidies they are receiving for this nonsense.
  11. Would anyone be interested?

    Please do the math before you respond like this. To fly for one hour burning 6 gph of AVGAS: 6 gal/hr * 6 lb/gal * .453 kg/lb * 46.4 MJ/kg = 757.7 MJ/hr. That is what a C-152 burns in gasoline at full power for one hour. To determine how much battery you need to supply that energy, a lithium-ion battery has, at best, 0.875 MJ/kg. Thus, 757.7 MJ/hr ÷ 0.875 MJ/kg = 865.9 kg = 1909 lb of batteries just to make a one hour flight. I did not even factor in the conversion efficiency of electric power, which would make it even worse. What percentage of aircraft weight is devoted to fuel? Factor that in, too. So 36 lb of AVGAS vs. 1909 lb of batteries? My old C-152 held 26 gallons, or 156 lb. That equates to 9.3%. Using batteries would make for an airplane weighing over 20,000. That would be one shitty airplane that no one would want to buy, except for people wanting to brag how 'green' they are. As for hybrids, they are lousy on the highway, which is analogous to how we usually fly. They are only good for city driving with lots of starts and stops, with the engine shutting down regularly. Not at all applicable to airplanes. You are far better off to avoid power losses from conversions and use a direct drive for your prop. Train engines are diesel-electric for other reasons, mostly to have one engine drive several motors. This may be applicable to multi-rotor craft, i.e. quad copters, but not airplanes.
  12. Would anyone be interested?

    My diesel Jetta gets over 50 mpg. (It was even better before the "fix".) Makes the hybrids look pretty crappy, I think.
  13. Would anyone be interested?

    Electric motors are pretty good, but batteries are the issue. We have covered this on another thread... When batteries have 1/5 the energy density of liquid fuel, then electric aircraft, (and automobile), propulsion will be something other than absolutely stupid.
  14. Would anyone be interested?

    Caterpillar advertises some of their big, stationary diesels at 0.34. One that fits onto an airplane will not be that good.
  15. The lesson is: Do no get divorced! Never get a divorce! Divorce is Wrong! There is no reason to ever get divorced! Don't you know, hitmen are cheaper than lawyers?