farri Posted April 8, 2008 Share Posted April 8, 2008 We are going to do a flight of 120 NM consisting of 2 legs. The first leg is, 75nm with a track of 180 degrees true and the second leg is 45nm with a track of 165 degrees true. The w/v (wind and velocity) at 2000 feet is 165/12 and at 5000 is 195/17. Our total fuel capacity is 60 lts. Useable fuel is 58 lts. Burn off rate is 15 lts phr. We will maintain an indicated airspeed of 50 kts. Using the least amount of fuel required,how much total fuel do we need to do this flight and can the flight be done without refuling. farri. Link to comment Share on other sites More sharing options...
Paul Willett Posted April 8, 2008 Share Posted April 8, 2008 Ballparking it in my head, using the FCST wind as all headwind because it is close enough - and conservative, 75nm * 38KT GS *15l=29.6l 45nm * 33KT GS *15l=20.4l =50 l Burn +(15% VR [if you apply it]= say 8l) +FR of 30 minutes = 8l +Assume no climb fuel differences + Taxi = neglibible + Assume no WX/Hold RQMNTS =66l required (but if you dont carry a variable reserve and you interpolate the winds a bit you might be ok with 60l) Link to comment Share on other sites More sharing options...
Yenn Posted April 8, 2008 Share Posted April 8, 2008 Track is given by you as deg True. so I am assuming no variation and therefore it will be 12 kts of headwind. IE GS 38 kts. That requires 3.158 hours at 15 l / hour = 47.4 litres, leaving 10.6 l, which is 42 minutes. As you say using least amount of fuel can it be done? The answer is yes. Would you do it? Would I do it? No. Being a chicken at heart I like to have at least 45 minutes when I land and with taxi, climb and the slow speed there is too little to spare. I have been in a situation with a 50 kt plane where the GPS was saying 40 mins to go then a minute later 42 mins to go, just because of varying wind speeds, but at 50 kts a difference of 5 kts wind speed is a big proportion of your TAS. Link to comment Share on other sites More sharing options...
Captain Posted April 8, 2008 Share Posted April 8, 2008 I have an extra section in my flightplan fuel calcs called "Arsesaving Fuel allowance" and I reckon that you don't have enough of that to do the trip without a stop. An example was the need to divert 45 Nm @ 90 degrees of track on the way home from Narromine, due to wall-to-wall rain. But then again I'm a bit of a scaredy-cat when the blue stuff starts to run out. As Kingsford Smith said ... "The only time an aircraft has too much fuel on board is when it is on fire". Link to comment Share on other sites More sharing options...
Flyer Posted April 8, 2008 Share Posted April 8, 2008 My calculations agree with Yenns and like Yenn says.... you might be legal but running close for comfort. Like the Good Captain, I also have an arsesaving fuel allowance. Set your own minimums and make sure YOU are comfortable with them. Regards Phil Link to comment Share on other sites More sharing options...
farri Posted April 8, 2008 Author Share Posted April 8, 2008 Can we do the flight or not. Guys,I`m looking for the right figures and answer. farri. Link to comment Share on other sites More sharing options...
jcamp Posted April 8, 2008 Share Posted April 8, 2008 Some legalities from CAAP 234 (1)1 Assume private/piston Variable reserve not required; 45min fixed reserve required. For a real flight and not an exam practical considerations revolve around the wind and where did it (the figures) come from. Remember although low at 2000ft they are 25% of IAS. If the winds are forecast as stated for the next 12 hrs AND confirmed as actual then maybe use a 20kt headwind. So assume only the first leg can be done. Link to comment Share on other sites More sharing options...
Captain Posted April 8, 2008 Share Posted April 8, 2008 Guys,I`m looking for the right figures and answer.farri. No worries farri. Need more info. We are going to do a flight of 120 NM consisting of 2 legs. Will you be overflying the waypoint at the end of leg 1 or landing there? The first leg is, 75nm with a track of 180 degrees true and the second leg is 45nm with a track of 165 degrees true. The w/v (wind and velocity) at 2000 feet is 165/12 and at 5000 is 195/17. Is this wind direction true or magnetic and is the speed in knots? What confidence do you have in that prediction? Our total fuel capacity is 60 lts. Useable fuel is 58 lts. Burn off rate is 15 lts phr. Please confirm that this is the proven reliable average over all flight conditions. We will maintain an indicated airspeed of 50 kts. Using the least amount of fuel required,how much total fuel do we need to do this flight and can the flight be done without refuling. farri. Please also advise the minimum safe altitude for both legs? What are the expected weather & cloud conditions ... with base and tops. Are the airports at which you will depart or land likely to require extensive or unusual length or time of taxiing? Do those airports have gliding or RPT operations or skydiving or an aviation event being held there during the flight which may demand an extent of holding? What are the possible alternate strips, how far are they off track and how far are they from both the waypoint and destination? Is fuel available at the alternates? Where is fuel available on your planned route, and is it assured? Given the limited data that you provided I doubt that practically there are "right" figures and answer. There will just be safe allowances or a pan & 3 tracks in a paddock, or a hole in the ground. Link to comment Share on other sites More sharing options...
motzartmerv Posted April 9, 2008 Share Posted April 9, 2008 is this a test??...lol...sounds like it to me....mate are you in a rush??...if it gets down to having to calculate precisley or ya might not make it then you are way way to close for comfort...Ur obviously not in a qantas heavy and on a strcit schedule...so land and top the tanks up..take the stress of fuel out of the equation.. Waht happens if the winds are 5 kts stronger then predicted??thats 10% of your IAS.. take ya time mate, enjoy the scenery. my 2 cents Link to comment Share on other sites More sharing options...
Guest RogerRammedJet Posted April 9, 2008 Share Posted April 9, 2008 We will maintain an indicated airspeed of 50 kts. 50 kts IAS? Have you thought of doing the trip in an aeroplane! Rog Link to comment Share on other sites More sharing options...
motzartmerv Posted April 9, 2008 Share Posted April 9, 2008 :thumb_up:..im sure that one will get a bite rog.. Link to comment Share on other sites More sharing options...
vk3auu Posted April 9, 2008 Share Posted April 9, 2008 Obviously none of you speed merchants has every flown in a Thruster. Enjoy the view. David Link to comment Share on other sites More sharing options...
motzartmerv Posted April 10, 2008 Share Posted April 10, 2008 ...yea i have...i flew in a very very dodgy one;) Link to comment Share on other sites More sharing options...
Captain Posted April 10, 2008 Share Posted April 10, 2008 50 kts IAS? Have you thought of doing the trip in an aeroplane!Rog At least the Rammer left out the word "real" this time. It might surprise a "real" pilot like the Rammer, that some in the RAA actually choose to own or fly aircraft that do somewhere near 50 kts IAS, and there are some that do so because that is what their budget stretches to. It bugs me that some "real" pilots like the Rammer feel the need to rubbish that with supercilious posts such as this. But then again, that's what some in the GA "real" world have been doing for years. However I bet the 50 kts brigade have a bigger smile on their faces. Get "real" Rog. Link to comment Share on other sites More sharing options...
motzartmerv Posted April 10, 2008 Share Posted April 10, 2008 I can't speak for anyone else but im sure it was meant as a joke .. Rag and tube in my mind is the esscence of ultralight flying in australia, it just so happens we enjoy rules that have allowed faster heavier higher performance machines into the fold. The rag and tubbers are just as much a real aeroplane as a 747. Some blokes love the freedom of hangin there chins out in the breeze with only a couple of instruments and a very steady cruise, while others like the feel of a rocket underneath them...each to there own i say...anyway....we are experiancing some drift off topic... cheers Link to comment Share on other sites More sharing options...
Captain Posted April 10, 2008 Share Posted April 10, 2008 but im sure it was meant as a joke .. I agree with the balance of your post, and IF Rog's comment was a joke, perhaps we can get Ian to invent a smiley that holds up a sign that says "This was a very funny JOKE", and it will stop me doing & :hittinghead: Link to comment Share on other sites More sharing options...
motzartmerv Posted April 10, 2008 Share Posted April 10, 2008 :thumb_up: Link to comment Share on other sites More sharing options...
Yenn Posted April 10, 2008 Share Posted April 10, 2008 My reason for flying a Thruster was that it did 50 kts. 50 take off. 50 climb. 50 cruise. 50 approach. I only had to learn 1 number. Seriously though I did get it up to 70 one day. In a near vertical dive. Oops, look out for TOSG! Link to comment Share on other sites More sharing options...
Guest J430 Posted April 10, 2008 Share Posted April 10, 2008 I am quite sure knowing Rog that his comment was all in jest........mind you he does have a point! 50kt machines are not really suitable long haulers......not to say you can't do it, just it might be a long trip around the country! So without pulling out my whiz wheel......or dare I say a piece of software.....it looks touch and go on the face of it. J Link to comment Share on other sites More sharing options...
Guest airsick Posted April 10, 2008 Share Posted April 10, 2008 No you can't do it. Winter is coming, the days are getting shorter and you would run out of light. (Just to turn the knife that Rog stuck in) Link to comment Share on other sites More sharing options...
farri Posted April 10, 2008 Author Share Posted April 10, 2008 I love it, farri Link to comment Share on other sites More sharing options...
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