Can not be answered
kentb said:
He believes that the higher he flies the faster he will go. Does anyone have real data to support what is the fastest alt to fly at? ......I had hoped to see a couple of statements like "best alt for plane Y is at alt X". Kent
"Whats the best altitude to fly at?" What ever altitude you want, it's the joy of flying. U-da man, the big cheese the captain of the ship.
Kent: Your question is of course un-answerable, at least in a definitive way, as in the sun always sets in the west way you want.
The question about is the wind favorable enough at higher or lower altitudes to justify flying at those altitudes is a BIG QUESTION MARK, mainly because you rarely have perfect known actual wind, save for the FT's (winds aloft forecast). Asking ATC for PIREPS is a good technique, since so many planes now can give you winds aloft at altitude with GPS and a little E6B calc.
The answer as some one said is with flight planning. Also as Dan said there are practical aspects of flying, convenience and comfort. However from what your wrote you sound like you already are going up into the teens to have a look. Just start taking records and calculate the trade offs. Clearly the more wind on the tail the better.
Old wisdom: Fly fast when flying in head winds and slow when you have tail winds. Also tail winds never help as much and headwinds usually are worse, because head winds last longer.
The answer lies not only in the wind but weather, HP, winds, temps, weights, leg distance, terrain. To eliminate some variables assume generically: piston plane non-turbo engine, no wind condition and leg distance not a factor (long legs).
- FLY as high as you can where at Wide Open Throttle (WOT), you are at or below 75% power so you can lean. That is about 8000-10,000 feet for the RV's, lower for Cessna's.[1]
- For min time (fastest speed), no fuel limit, on the deck wide open 100% power full rich.
-Min fuel RV again assume generic limits; 12,500 - 19,000 feet, depending on weight and engine HP. Trip time will go up. You can approximate min fuel by flying low altitude at an airspeed approx 10% above best L/D speed. Not sure many want to fly their RV on a X-C at 90 mph.
[1] RV's make more power higher up because of the better induction and exhaust and higher cruise speed.
dan said:
Realistically, in an RV on a 3-hour leg, what's the drop-dead biggest delta in ETE that you're gonna see? In all likelihood about 20 minutes. Honestly.
True but 20 minutes may be 3 gals of gas at $4/gal or $7/gal.
However JUST PULL THE BLACK KNOB BACK AND THE RED ONE AS WELL AND YOU WILL SAVE FUEL. The real saving is playing the winds. If you have O2 you and have the option on the west coast you can sometimes get into the Teens and get 30 kts you might not get in the less rarefied atmosphere. Other wise I am with Dan, what feels good.
Also flying high you can't see as much. I asked an older 747 flight attendant what her favorite plane was. DC-7. Why? She said: "We flew lower and you could see more of the country side".