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Speedbyrd

Determing aircraft range....

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I would imagine this could be a complex problem given the variables that an aircraft can encounter. So when my aircraft description says it's max range is 6750 miles, how is this determined? Is the the distance it could fly on a full fuel load while flying WITH the wind? I'm just doing some fuel calculations for my widebodies and was interested to know how range is determined.

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Real world range and FS range are not always close.The real world advertised range is for perfect weather conditions, perfect weight, perfect flight. With no wind.The no wind concept applies to any aircraft range figures, real or FS. Now some people, and airlines, will plan flights based on prevailing winds expecting an assist from the wind.There is a great file about an A340 flight across the Atlantic from KJFK to LGAV on FlightSim.com - maybe here also. It emphasizes the legal fuel range for the A340 won't allow the flight. They have to file to land in France. But based on their fuel usage and prevailing winds, they are almost always able to legally refile their destination as Athens before they reach the UK.Keeping track of fuel used during a flight is a major duty of cockpit crews on long flights. Also climb practices can cut a range significantly.Using time acceleration in FS can increase a range quite a bit on some aircraft, decrease it on others.The FS Flight Planner gives a guess based on many parameters of the aircraft, and while it tends to be a little optimistic, if you fly at the speeds it calculated from the .AIR file and the aircraft.cfg file settings it can be pretty close.Most people in my experience tend to fly too fast in FS, pushing an aircraft near it maximum, rather than it's cruise speed.The best experiement I know of for FS is to climb the aircraft to altitude - pause FS - record the amount of fuel used in pounds.Then fly one hour at cruise speed, not full speed. Pause FS - record the amount of fuel used in pounds for a one hour flight.That will give you solid performance numbers for your FS aircraft.

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makes perfect sense. I would then have two sets of info, one with the wind, one against, for east-west or north-southbound flights. I think you can pretty much count on adding an hour of flight time going westbound. Thanks for the info and I'll put it to work.

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>I would imagine this could be a complex problem given the>variables that an aircraft can encounter. So when my aircraft>description says it's max range is 6750 miles, how is this>determined? Is the the distance it could fly on a full fuel>load while flying WITH the wind? I'm just doing some fuel>calculations for my widebodies and was interested to know how>range is determined.Just like in the real world, you should concern yourself with endurance, and not range.Endurance is the amount of available flight time, and range is the distance over the ground you may travel. In the real world, a head wind or tail wind will change the range significantly, however the airplane will fly only for a determined amount of time in any condition. So for safety, we use endurance more than range... in the real world.You can search for the aircraft data through google. Then find the max endurance. For a margin of safety, calculate the max fuel burn and you will have your total endurance.The main reason for using endurance over range is that you can calculate that you can fly for say 500nm, but an unpredicted headwind may cut your range down to 400nm. When you crash you say to yourself, I still had another 100nm that I could go. The caveat is that on that SAME flight your endurance was say 4 hours. Because the headwind changed you can still only fly for 4 hours. So as you approach your time limit you know you can not reach your destination, and can divert as necessary (poor flight planing anyway LOL). Like I say, range can deceive you in that winds aloft will change, and shorten your total range.... Endurance is time, and regardless of head/tail wind you can still only fly for so much time, so it is safer.You do have to calculate endurance, based on DP, Climb, En route, and Arrival to the terminal area. And have 45 mins of reserve fuel if you are IFR (Fly to destination, then to the alternate if one is filed and fly thereafter for 45 mins at normal cruise speed), or for VFR have 30 mins of reserve fuel (fly after arriving at destination) during the day, and 45 mins at night.Have a good one,

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>Keeping track of fuel used during a flight is a major duty of>cockpit crews on long flights.Pan Am pioneered "Flight Control Technics" with the early Clipper routes. "Flight Control" is the general heading for controlling a flight in real time as opposed to executing and following a "flight plan" based on forecasted conditions.The "howgozit" chart was a part of Flight Control. The chart allowed the navigator to plot the progress of a flight on the "howgozit" chart to be able to see "how goes the flight" hence "howgozit".It relieved the Captain from certain decisions as to whether to press on with a flight or turn back because of actual winds or in-op engines. Egos can sometimes over rule logic. There are many cases when a Captain turned around based on a plotted line being above or below a reference line on a howgozit chart.Winds are one of the most influential conditions on a flight. The early Clipper navigators used celestial fixes at night to determine ground speed and Line of Position (LOP/speed lines) during the day to read the actual wind. Pan Am regarded these "Flight Control" technics that were developed by their Engineering Dept. in N.Y. as proprietary and held confidential within the company. World War 2 and the government required the sharing of these technics for the war effort.Amelia Earhart's navigator was Fred Noonan who did the survey of the first Pan Am route to China using "Flight Control" technics. He knew how to control a flight so as to NOT run out of fuel. Consequently the historical record of them crashing and sinking on July 2, 1937 because of fuel exhaustion is not entirely true.

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I believe they are alive and well and raised many babies on Borneo...... lolanyway, I miss Pan Am. Grew up with them and it's a shame what happened. Thank you for sharing this.

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I usually presume the maximum range in an aircraft description to be for the real aircraft, full fuel load, no winds, flight at optimum range altitude, optimum range speed (both of which might vary during the flight). It may or may not include IFR requirements for alternates and legal reserves. I know of a few military aircraft, and at least one commercial series (Short Empire class) for which the maximum range presumed a fuel load that would make the aircraft exceed MTOW, so that in-flight refueling is a necessary SOP for a full range flight.Assumptions about loads? I would like to think for commercial carriers, a maximum range would allow a paying load, not just fuel. Loaded to MTOW? Not necessarily, as this is not one number, it depends on conditions at the point of takeoff.For many light aircraft, the maximum range number may be for full fuel and pilot only, and possibly no reserves. The AOM even for light aircraft will have range information for a wide range of loads, speeds and altitudes, with the maximum being the biggest number one can get from anywhere in these tables.I don't expect the performance in the aircraft description to be the performance of the model. Very few FS models are that well designed.In some cases, the aircraft description may be the intended performance of the model. Even then, performance doesn't match intentions.Also, the information used by the flight planner in FS9 is not always a good predictor of performance: neither speed or fuel consumption. I've found aircraft that will fly twice as far as they should, others that burn three times as much fuel as predicted, three times as much as similar aircraft models of the same size with the same engine.I devote a lot of time to testing cruise performance of models I've collected. This makes up about half of my simulation flying (then I know what performance to expect for the other half, exploring the simulated world). To determine actual range: flight test, flight test, flight test.

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that's what I'm doing now. My collection includes the Overland B777 family (3 models); the Overland MD-11; the Overland A330's and the A345 / A346. I will fly each of these on a reasonably long flight; collect the data and compare it to advertised 'range' on the official airline websites. I've got the MD-11 as close as it will get to its estimated range of 7,000nm. I tested with no winds aloft so when planning, I will just need to plan for winds, depending on which direction I'm going. Tomorrow I start on the B777's.

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Something I've found very useful is a GPH/ PPH guage. I've put the default Mooney gauge in a lot of aircraft.On recent flights in the Ki-43, I've gotten adverse winds and had to lean out/ throttle back to make sure I had enough fuel to reach the destination / only available runway.Now you can't lean out jets very much, but you can throttle back to find an optimum fuel usage for speed point.

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I'm not sure I'm clear on that. My 'throttle back', you mean slow down? I usually fly around .83 on my widebodies, so they are designed to do .84 or .85. Please clarify if I missed your point. Thanks.

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This data is from www.gulfstream.com - their reference page for the G550 specifications - it does not copy well - but:Long Range Cruise Speed - 6,750 nm / 12,501 km at Mach 0.80Normal Cruise Speed - 6,000 nm / 11,112 km at Mach 0.85High Speed Cruise - 5,000 nm / 9,260 km at Mach 0.87Mmo (Max Mach) - 0.885The data is based upon 8 passengers, 4 crew, NBAA IFR reserves - with a note that the actual range will be affected by ATC routing, operating speed, weather, outfitting options and other factors.(I picked this aircraft because the company I work for is getting one delivered next month. Being able to fly non-stop from the US Midwest to Shanghi was a critical factor in aircraft selection - though it will have to be at Long Range Cruise Speed. Right now it takes stops at PANC and UHHH in the Challenger 604)I'm sure commerical aircraft have similar specifications - A Normal Cruise Speed/ Range;A High Speed Cruise Speed/ Range;A Long Range Cruise / RangeThe numbers are harder to find for commercial aircraft because they really are quite customized for each airline.You can see on the G-550 figures that the 0.02 mach between Normal Cruise and High Speed cruise cuts 1,000 nm off the range.But yes, throttling back will often extend the range significantly.A fuel flow gauge which gives you FS readings in GPH or PPH (or LPH / KPH) can really help you fine tune your performance for the best combination of speed and range. Just remember, verify if you are getting total fuel flow or a per-engine figure. Could save an embaressing dead stick landing in the boonies.This is much more critical in reciprocating piston engines than in jets, but it's still useful in jets.

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