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Guest TerryT

En-route wind calcs

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Does anyone know how involved the rw calculations are for estimating head/tail winds en-route for fuel planning?For example do they use data from each reporting station, work out head/tail component and how long that will be in effect for, ordo they split the route up into equal length segments and then do a spot wind check in the segment and apply that?I am trying to find the best way, with the least effort, to enter head/tail winds into the fuel planner.What prompted this was a flight last night where I underestimated the winds and ended up landing with 26,000lbs of fuel - not ideal :-eek TIA

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You need winds aloft forecast for your time each major leg traverses its respective area and your heading changes. You can use triginometry to figure the head/tail wind component to correct the groundspeed after adjusting for TAS. On the FAA's Pilot's Handbook pages I think you'll find a reference to it. Go here first:http://www1.faa.gov/avr/afs/pilottesttips.cfmbut be aware that the .pdf files are huge. I've purchased at low cost some FAA Handbooks at Borders book stores. As an example, the FAA Instrument Pilot's Handbook (not exact title) was about $13 US.

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Howdy Vulcan,As a general aviation pilot, the way I do it is to get the METARS for several places enroute, or close to the route I plan to fly, then incorporate that data into my flight plan. I always figure that this is just a general guess-ti-mate, and the flight plan will probabbly not be all that accurate. Of course in real world flying, the light planes I fly, do not hold too much fuel anyway. To have too much is not a problem, while not having enough is always on the back of my mind.

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Thanks for the two replies so far, both of which provided extra insight into solving the problem.However I realised that my original question probably didn't make clear my reason for asking :-doh I only fly virtually, not rw and mainly fly airliners not GA so I usually don't have the problem of small fuel tanks ;) usually the opposite, too much fuel and too heavy to land :-eek

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I don't know anything about airliners. But for GA planning I would treat fuel burn per hour as a constant based on power settings and altitude. Use the winds aloft forcasts and true air speed to calculate ground speed. Comparing ground speed to distance you can estimate the fuel needs. The winds aloft forcasts are available at many web sites.There is a very nifty tool called an E6B flight computer. It a kind of slide rule that costs around $30 and is available in pilot shops and aviation supply stores. You can use to make every aviation calculation imaginable, from crosswind/headwind componants to ground speed, fuel consumption, true air speed, density altitude, knot/mph/kph conversions, time en route, etc. Even if you don't fly in the real world it is well worth buying one.

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Vulcan, I think this is what you are asking for.http://aviationweather.gov/fdwinds/Just click on the sites closest to your flight route and the average out the direction/temps/wind speeds. This will then give you a good estimate for flight planning purposes. Remember, weather is fluid and is constantly changing so for those longer flights you might want to review the current TAF (forcasts) for the planned flight route.Hope this helps.Terry

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