text: Maximum radius of operation - Rotary Wing Forum
  #1 01-09-2011, 06:01 AM
  I love simple formulaes to solve problems that would take lots of guessing or trial and error to arrive at.
  I have always had this formulae stuck in my bean for knowing the maximum radius I can fly and return with my usable fuel with wind. Usable fuel does not count warmup and takeoff fuel, and reserve fuel.
  groundspeed outbound X groundspeed inbound
  groundspeed outband + groundspeed inbound equals the max radius you can fly per hour of usable fuel onboard.
  Simple...say you can fly 80 mph groundspeed with no wind....and you have a 20 mph headwind outbound...just plug in 60 mph groundspeed going out and 100 mph coming back.
  60 mph X 100 mph
  60 mph + 100 mph
  equals 6000/ 160
  equals 37.5 miles max radius you can fly per hour of usable fuel onboard.
  So...if you have two hours of usable fuel...you can fly out 75 miles and return.
  #2 01-09-2011, 06:42 AM
  Stan's the formula man. Maybe you should write a small book of aviation formulas for those of us with short memories. Something we could put in a flight case or carry in a pocket.
  #3 01-09-2011, 06:44 AM
  I was going to recommend that too but I forgot...
  #4 01-09-2011, 08:00 AM
  And the nice part of this formula is that it works in any set of units, as long as the two speeds are measured in the same unit.
  #5 01-09-2011, 08:39 AM
  Jet Helicopter pilots!
  I love the way you are always thinking about aviation and then sharing it with us.
  In my flying near the Pacific Ocean the wind is seldom the same speed or direction long enough to get your formula to work.
  It was the same in the high desert of El Mirage or the arid region around Buckeye, Arizona. Sometimes we can turn a head wind into a tail wind by flying at a different altitude.
  I higher altitude seems to considerable extend my range even if the wind is the same.
  The Predator has a theoretical range of 219 nautical miles at 75kts with no reserve. In my flight planning I use 75 nautical miles because of the unpredictable winds. Mariah Gale may have a theoretical range of 456 miles at 90kts. I will probably use 300 nautical miles for flight planning. In my experience even Lockheed Martin is not to be trusted about winds.
  I know that you jet helicopter pilots can land anywhere and siphon fuel out of a tractor so your fuel calculations don�t have to be accurate.
  PS this is my attempt at humor.
  Unless you live ere.
  Its amzn how many times iv gota head wind go'n out, and by the time im headn back, iv gota natha head wind. __________________
  #7 01-09-2011, 08:38 PM
  Its amzn how many times iv gota head wind go'n out, and by the time im headn back, iv gota natha head wind. Birdy
  I must live closer to you than I thought, because I have the same problem Mark
  #8 01-10-2011, 05:49 AM
  Good one Vance , I love your humor.
  By the way , next time you see Stan , tell him my mathematics teacher says she loves him and his formulas.
  I tried to tell her he was already spoken for.
  She said she has a formula for that :
  ONE HELICOPTER PILOT _________________ = ENOUGH TO GO AROUND
  I hope the girls' have their sense of humor intact this morning.
  Otherwise I'm dead Arnie Madsen
  Vance; you have gotten me thinking! The next time I see Stan's Helicycle at Shelbyville, I am going to look very close for an old fashion credit card.
  #10 01-10-2011, 07:40 AM
  Identify attempts at humor.
  Otherwise I'm dead Thank you Arnie,
  I have to identify my attempts at humor because I am often not funny and it is easy for Stan to get his feelings hurt.
  He is a typical hypersensitive helicopter pilot.
  #11 01-10-2011, 10:01 AM
  Guys, I have a scenario to this. Hypersensitive helicopter pilot uses common sense and after reading Stan's formula which he already knew he does some basic calculations and tries to avoid siphoning fuel from the tractor in the first place. Maybe the tractors fuel tank are empty. Then what?? **laughs**
  Obviously hypersensitive helicopter pilot has some idea of how far his destination is and how much fuel he has remaining to get back to home base or other fueling location in his area of flight. He takes notice of wind conditions and allows a sufficient fuel reserve to account for this. He also keeps a close eye on the fuel gauge knowing how far a half or quarter of a tank of fuel will take him. I have had the chance to witness a fuel gauge failure. Which resulted in inaccurate fuel level readings. So you have to also rely on the calculations. If he has a 50-mile range one way he's not going to go 50-miles and expect to get back to home base.
  Last edited by SKYHAWG; 01-10-2011 at 10:43 AM.
  #12 01-10-2011, 10:42 AM
  Harry, in aviation you use fuel gauges as educated backup guess in case you get bored and want to cross check your fuel calculation based on fuel burn per hour and time elapsed. Seriously, though, if you rely on your fuel gauge to tell you when your tank is going to run dry you need a lot of tractors on the ground...
  #13 01-10-2011, 10:50 AM
  The flipside of that is even when you've calculated your fuel burn, know exactly how long you've been flying + how much fuel was in the tank on departure, or have a fuel flow gauge - don't forget none of that will be correct if you have a leak. In other words don't ignore the fuel gauge if it's reading lower than you think it should be...
  #14 01-10-2011, 12:33 PM
  Stan, you just gave me great idea for a simple and safe way of monitoring my fuel level on my coax design. Thanks,
  #15 01-10-2011, 12:44 PM
  Yep - I posted this in another thread a while back, I had a fuel leak in an R22 one night. Nothing you could see or smell from the cockpit, just noticed the gauge was dropping a little faster than it should - figured it was just a crappy gauge, after all I knew how much I started with & how much I'd burned.