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Post by bbb747 on Apr 29, 2014 16:29:45 GMT
Hello,
In a attempt to render my flights a little bit more realistic I'd like to start calculating fuel instead of estimating and landing with 50 tons of fuel onboard.
Never used a fuel calculator. Where do I start? Are there any tools I can use with the HJG aircraft?
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Post by Mike Monce - HJG on Apr 29, 2014 19:43:30 GMT
It's not too difficult.. but needs to be done with each aircraft, especially here at HJG where the fuel flow varies with the engine type fitted. We try to be realistic  1) Record the average fuel flow during your climb (total for all engines!!) ... I usually do this at about 10,000 ft as the FF will decrease with altitude which compensates for the larger FF at takeoff. 10,000 ft FF gives a good average. 2) Do the same at cruise, and in descent. 3) Divide your final cruise altitude by your average vertical speed, convert to hours and multiply by the result for part 1 to get the fuel burn for climb. e.g. FF for climb turns out to be 8000lbs/hour, your cruise is at 33,000ft and you average 1500ft/min... so 33000/1500 = 22min = .37 hr; so FF for climb is .37*8000lbs = 2960lbs 4) Take the total distance to the destination, and for jets I subtract off 80nm for climb, and 120nm for descent. Example: 600nm trip gate to gate. 600 - 200 = 400nm. divide by average ground speed (make sure you take into account winds aloft if using real weather!), let's say avg GS is 460kts, then 400nm/460kts = .87, and let's say cruise FF is 6000lbs/hr, so .87*6000= 5200lbs. 5) do the same for descent, avg GS say, 320 kts, avg FF 2000lbs/hr, so 120/320 = .38, .38*2000 = 760lbs. 6) Now add together, 2960 + 5200 + 760 = 8920, Now add 1 hour reserve using the cruise value, 5200, so total is now 14,120. I then add an additional 5% for taxi/ground operation, so final is 14826lbs in this example. This is fairly realistic. I also have put this into an excel spreadsheet to help run through it quickly which also takes into account winds aloft for me. Others just load up with about 50% fuel and go... works for them  Some days that's what I do, other times I like to go through the entire process.Depends on how much real planning you like to put into your flights. Mike |
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Post by bbb747 on May 1, 2014 0:12:19 GMT
Hi Mike,
Thanks a lot for the explanation. I'll give it a try and see how it goes. Much appreciated.
cheers,
Michel
CYUL
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Post by aerofoto - HJG Admin on May 5, 2014 3:33:16 GMT
Mike's methodology will/should work fine .... for those whom can, easily, get their heads around the concept he discusses, BUT, I actually use a different, easier (I believe), though "much more crude" fuel planning methodology .... which I'll discuss as follows .... Depending upon how economically one wants to fly (and which is the key to most of this) .... the HJG DC8-40's will, at 31,000 FT (a good initial cruising altitude) indicate the following fuel burn rates after a MGW T/O .... MACH 0.79 ("economic" cruise) = 4,881 LBS per engine/per hour .... or 19,444 LBS (all 4 engines) per hour.
MACH 0.82 ("balls-to-the wall" cruise without a care) = 5,440 LBS per engine/per hour .... or 21,760 LBS (all 4 engines) per hour.This particular DC8 version, like each of its preceding turbojet powered versions also, has quite a high fuel burn rate .... and which is in keeping with known performance of the RR CONWAY fanjet engines which powered all DC8-40 aircraft. For economic cruise at 31,000 FT and for a flight of some 1 hour duration ....Based on the indicated hourly fuel burn rate, for the DC8-40's (remember fuel burn rates, quite correctly, differ for each of the HJG DC8 simulations), at cruising altitude I'd, typically, plan on a total 19,444 LBS of fuel "for starters" .... then add an extra 30 minutes "reserve" on top of this, and which which equates to an additional 9,722 LBS, to result in a new total of 29,166 LBS of fuel .... and to which I also then add an additional 10% more (just for good merasure), and which equates to yet another 2,916 LBS, for a final/total fuel load of 32,082 LBS (say 33,000 LBS) of fuel for my entire flight of "1 hour duration". I then simply load/distribute this total evenly across DC8-40's 5 fuel tanks (which should result in roughly 22% to 23% .... or so .... fuel in each individual tank) .... and then get on my way  Using this "very crude" methodology I've never .... ever .... had everything suddenly run dowm/"go quiet" on me en-route to any particular destination .... and nor have I ever had to divert to somewhere other than where I was planning on going either in order to get top up. Using this methodology I've always managed to arrive at my planned destination .... with a comfortable fuel quantity remaining after engine shutdown and without being overweight for landing either. It certainly works for "ME" .... within FS  Try this methodology also Mark C AKL/NZ |
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Some days that's what I do, other times I like to go through the entire process.Depends on how much real planning you like to put into your flights. 
