This question isn't specific to the B727; however, since the members here (especially Lou and Mark) have been most helpful I figured maybe one of the pilots here could assist me.

What I want to do is learn how to figure my own fuel required for a flight. In the end I will bring this lesson back to my VA and add to the knowledge base there. No one has specifically tackled this question although there are so many resources provided. Those resources figure the fuel for you. That's not what I want, I want to figure the fuel on my the old fashioned way. I tell my kids "Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for life." These last few years of flight simming I have been getting fish. Now I want to feed myself.

Here is what I know but this isn't much.

1. At cruise altitude record the current fuel.
2. After one hour record current fuel.
3. This provides rough fuel use per hour.
4. Divide by 60 for fuel use per minute.
5. Multiply fpm times the time it will take to complete a flight from A to B.
6. Multiply fpm by the time it will take to fly from B to alternate C.
7. Multiply fpm by 45 for reserves
8. Multiply fpm by 30 for taxi
9. Add that all together for the total fuel you will need for a flight from A to B with alternate C.

Granted none of this takes into account weather.

Is there another way to figure fuel per hour without making a flight in the plane for one hour at cruise altitude?

If you were asked to teach this class, how to plan fuel, to a group of none-pilots how would you teach it?

Thank you for any help,
Ed

Hi Edward.

I think number 7. Multiply fpm by .75 for reserves is wrong. You need more than 45 seconds of fuel for the reserve. ;)
So shouldn't it be 7. Multiply fpm by 45 for reserves?

Another thing is to take into account the wind (tailwind = less time, less fuel, headwind = more time, more fuel). Or this calculated by the time between A to B and B to C?
Hopefully Lou can give you the info you need. I would like to see it too. ;)

Mark

Ed, as I say I am so mad that I dumped all my old 727 fuel use charts.

FAA fuel for the trip @ M.78 = fuel to destination + 45 minutes reserve VFR (no alternate). If you need an alternate you must add fuel to the most distant alternate @ LRC (long range cruise) if you have more than one.

Let's say you want to go KLGA to KSTL, about a two hour trip. The weather is bad enough to require an alternate. You use KMCI( Kansas City, MO.) as your alternate about one hour. We used to figure 10,000 pounds per hour at the old M.86, but at slower speed of say M.78 lets figure 8,000 pounds per hour. That should cover T/O & climb. All this and we still need to look at the wind (140 pounds per minute for fuel).

Trip fuel = 16,000
Alternate = 8,000
-------------------------
                24,000

But you still need some extra fuel for the descent into KSTL and a missed approach and climb to go to KMCI. Then you need some extra fuel to maneuver around for the approach at KMCI and a little bit of comfort fuel for momma and the kids!  ;)

Try this...

Put 30,000 pounds of fuel on the plane and a good load of people. Climb up to FL 310 or FL330. Set cruise for around M.78. After the plane settles down for a bit and is holding M.78 have a look at the FF. If the numbers come out to around 8,000 pph (2,650FF per engine) your good!
Not sure the CS FF numbers are exact, but give it a try

Nobody that I know would like to land the 727 with less than 8,000 pounds of fuel & if the weather was iffy, I'd use 10,000 as a minimum. Remember, you cannot plan to takeoff if your fuel will make you too heavy to land. In the 727-100 the max landing weight is 135,000. So your takeoff fuel minus the burn should put you under landing weight at destination.

Using the above trip, I would need to look at the EOW (empty operating weight) + payload = ZFW (zero fuel weight) + my minimum fuel at destination (8,000 pounds min - about 45 minutes at low level) should be less than max landing weight. Then you can figure trip fuel to see where the T/O weight comes out.

I'm guessing here...

EOW = 96,500
PL     = 25,000
-------------------
ZFW  = 121,500
MTO  = 152,000
Trip fuel = 24,000
T/O WT = 145.500
Only 6,500 pounds of extra fuel available for max takeoff weight. A bit tight, but doable. Are you feeling lucky?  :o
Since the burn is high, landing weight is not a problem. You could take extra taxi fuel as long as you do not exceed max takeoff weight.

Hope that helps a bit...

Lou

You're right, Mark, I was thinking in fractions of an hour. Let me go correct that.

Well, Lou, I'm not sure I follow you there. If I had a B747 for example how would I take your guidance in that post and apply it? I'm looking for how to plan fuel for a trip given any plane not just the 727.

Wow!

Thanks for that great info (as usual), Lou. Unfortunately, my brain just went numb after reading it all. Must be my age. :(

I guess the thing to know is the fuel burn per aircraft, then all you need to do is factor in the the rest, like Maximum TakeOff Weight, Maximum fuel at destination and Maximum Landing Weight to give you the numbers for it. I don't think the Math is too hard using that guide that Lou gave us. I'll look into it for some other aircraft to see what I get.

I think the CS767 uses about 7200 pounds per hour (3600 pph x2), when cruising. If you have that, it might help with your planning a bit.

Mark

i done some flying in 727-100 with michael2 mod. it uses fuel more realistic if modded. right by the tables for cruise and descend.

so i can export and send you FSPassengers statistic tables which indicates fuel usage for climb\cruise\descend and time and distance traveled. but it'll be cool for modded ver only. default cs727 uses less fuel for climb and more for cruise, and default FSX fuel planner wrong for modded version. it'll gives you 3-4 times less fuel needed.

i still cant find right way to calculate fuel needed for climb.  and its really depends on climb procedure which i believe i doing wrong. so thats a subject for another question to Lou  :)

very roughly for modded cs727-100, for FL310 cruise at m=0.78 expect to use 7500 lbs climb (totally for 3 engines), +  3500*cruise time for cruise per engine (in hours), + 4000 for descend (at idle for all engines total) and + some for reserves. Climb to FL310 usualy takes up to 20 minutes if close to MTOW.

Markoz wrote on Feb 18^th, 2012 at 6:35am:

...I think the CS767 uses about 7200 pounds per hour (3600 pph x2), when cruising. If you have that, it might help with your planning a bit... Mark

Mark,

Excuse me, but are you sure? I think there was a mistake and you're talking about the B-727. Isn't? My B-767 uses about 11,000 pph (5,500 pph x 2), when cruising @ 0.80 MACH at FL300.

Pinatubo.

Windplayer,

After takeoff segment complete (flaps retracted and out of 1,500 feet), set climb power and climb at 250 knots (or faster depending on local rules) to 10,000 feet. Reduce pitch to accelerate to 290 knots to M.76 or so (you can use cruise Mach for climb if weight & FPM permits) up to planned cruise altitude.

As I've said I had all those charts and dumped them many years ago - rats! :'(

You could adjust climb speed for head wind or tail wind or if you were running late you might speed up in climb to get back on time. Since the 727 had no auto throttles, in the early days you had to keep an eye on the EPR as you climbed and make small adjustments. Later on in the life of the 727-200 airlines added a PMS (performance management system) which was actually pretty good at keeping optimum EPR during climb & cruise. It was a simple computer which you could feed weight information and it would read the SAT and make calculations and move the throttles during climb and cruise.

All the information about calculation of fuel is the same for all planes. Just the numbers are different. You have a max takeoff and landing weight and a max zero fuel weight. Just plug in the fuel burn and reserves and away you go. Sure temperature, load & balance will affect the numbers, but the logic is still the same for all planes.

Lou

Pinatubo wrote on Feb 18^th, 2012 at 2:18pm:

Markoz wrote on Feb 18th, 2012 at 6:35am: ...I think the CS767 uses about 7200 pounds per hour (3600 pph x2), when cruising. If you have that, it might help with your planning a bit... Mark Mark, Excuse me, but are you sure? I think there was a mistake and you're talking about the B-727. Isn't? My B-767 uses about 11,000 pph (5,500 pph x 2), when cruising @ 0.80 MACH at FL300. Pinatubo.

Well I did say "I think". I did not check before posting. Besides that, I had not flown the 767 for a while. Also, I'm usually flying the 767 at between M0.78 and M0.79 (CI of 20 for an international flight) and normally well above FL300.

In the attached image, I an flying the 767 @ FL350, CI of 40 (for a domestic flight), and the speed for the flight is M0.789. I'm getting 4,200 pph x2 so I guess my figures were off a bit, so I probably did confuse them with the 757.

Mark

---

something got my attention guys!

when i climb in 727-100 with constant power setting, as i get higher, fuel flow reduces. Is that normal for 727-100 without any computers? Or it has one which adjust fuel flow?  what adjust FF and according to what it adjust it? (we dont have PMS on cs727-100 as i understand)

as i get higher EPR also increases (constant pwr setting) that should be right i guess.

I believe it is normal in all aircraft. This is why the higher you go, the less fuel the aircraft uses (saves money for the Airline company). All airliners have an optimum and maximum altitude at a given weight (seen in the VNAV Cruise page in the FMC on the 757 & 767), so I always try to fly near the optimum altitude. Lou can explain it better than I can, so I will leave it to him. I understand how it works, but I'm not very good at explaining how it works. :-/

Mark

just landed in YSSY. Flew YBAS to YSSY route. b727-100 modded.

http://fuel.aerotexas.com/ - this fuel planner said i will need around 26200 lbs for flight. and i really used this amount of fuel. good UNIVERSAL planner, many planes presented, but unfortunately it is not detailed. you cant fill cruise FL and so on. and it needs dep and dest ports to be entered. many regional airports not there.

To take of from 8000 ft rwy 30 at YBAS i had to be at TO weight no more then 150 000lbs. so i loaded 12000 lbs cargo + 114 passenders + and 32400 lbs of fuel. fuel planer suggested 39000 lbs with reserves, but i canceled fuel for diversion (bad idea). i landed with about 2600 lbs in every tank. climb wasnt fuel efficient (again), but still better then my worst climb. i used 7600 lbs for TO and climb, versus my best 5500 with same TO weight. during cruise i monitored fuel usage every waypoint (NDBs, VORs), and throttling back a little to set cruise pwr for current weight. Descended at idle, and landed YSSY rwy 16L. And that way i was able to get very close to EFU by that planner. really need to know more about fuel efficient operations :) Usually i overusing fuel.  but i better learn about all that :) I wanna go Hawaii in 707 :) dont want to swim around floating wreck of my x-mass gift to myself somewhere in pacific :) Thats totally uncool.

Does anyone know if FSX actually takes into account the planes weight when figuring fuel burn? For example if I burn off 2,000 pounds of fuel will my fuel burn over the next hour be less because the plane weighs less? I have never noticed FSX doing this.

What I'm getting at here is in planning a flight should I plan the extra fuel to carry the weight of the fuel itself? Again using the example of 2,000 pounds of fuel on a one hour flight should I load an extra 60 pounds of fuel to account for the weight of the 2,000 pounds?

The higher you go with a jet engine the lower the fuel burn.
The jet engine is more efficient at high altitude and colder temperature.

Using a climb or cruise chart, you adjust the EPR, not the FF.

Lou

EdwardS, if your A\T set to maintain speed, then as you burn fuel, aircraft become lighter, and require less power to maintain speed, so A\T will throttle back a little. A never flew plane with A\T, so i cant tell if it is correct for FSX, but it should do that i think.

Lou, could you be more specific on how engines are controlled in 727s and 707s? Those throttle levers in cabin adjusts what? and how engine know how much fuel it'll need for currrent altitude and set power?
i mean if fly DC-3, then i should manually adjust mixture. who adjust it in jets?

Thank you.

So is that a yes or a no? I'm not sure how those answers relate to the question I asked.


EdwardS wrote on Feb 24^th, 2012 at 2:39am:

Does anyone know if FSX actually takes into account the planes weight when figuring fuel burn?

EdwardS wrote on Feb 24^th, 2012 at 2:39am:

Does anyone know if FSX actually takes into account the planes weight when figuring fuel burn? For example if I burn off 2,000 pounds of fuel will my fuel burn over the next hour be less because the plane weighs less? I have never noticed FSX doing this.

The only thing that I have noticed with most (if not all) aircraft, is that as you burn fuel off, the aircraft gets lighter - so its speed increases.
So the fuel burn seems to remain the same, while the plane goes faster.

Mark

EdwardS, YES. FSX takes into account weight of the aircraft. if you want to stay on one cruise FL and on fixed speed - then you'll have to decrease power with time, so you will burn less fuel. or you can climb slow to higher alt, and save even more fuel for cruise. or you can fly same power setting, but you'll fly faster and faster :)

BUT! all that relies to flight model, not Fuel Flow rate. If you have A\T - it'll adjust power and you'll get less FF, in 727,707s you gotta do it yourself. And FSX default fuel planner sucks for payware aircrafts anyway, it only gives good results with default, and close to default crafts. no matter how it calculates EFU - it good for default crafts, and they all way to powerfull and superfuel-efficient.

To calculate estimated fuel usage with respect to all that, you will need some tables\figures for specific aircraft.
the bad thing about it - it all comes to how precisely flight model is :)

Ah, thank you very much. I wasn't sure that FSX was handling that aspect at all. So it is but from our limited resources plotting the affects of it is not really practical.

When you move the throttle in all jets - 727, 707, 747 etc. you are sending a command to the FCU (fuel control unit) on the engine. In the older planes that was accomplished by a cable and push-rod arrangement. On the newer jets -except Airbus - the command is via wire (potentiometer) to the FCU. The result is the same. In the Airbus the command is sent to a computer first which decides what the engine does. That is not to say that the FCU does not make adjustments, it does, but the computer part of the "Bus" is more controlling.

EPR is the primary thrust setting instrument with N1 being secondary. The resulting FF can vary depending on the condition of the engine. A newer engine may have a lower FF just because it is tighter. Same with EGT. The newer engine could have a lower EGT for the same power since its just working better.

Jets are designed to work better at high altitudes and colder temps. In the old days the "straight pipe" non fan did great at high altitude, but was less stellar at lower altitudes. With the advent of the by-pass fan, low altitude performance was much better. Today, with the huge fans the efficiency of the power plants is at an all time high. A lot of thrust at low altitude and great performance at cruise altitude.

When you set cruise power, you must be at the correct speed when you set the EPR. If you are faster when you set the EPR, the engine is actually producing more power for the same EPR. Same is true if you are slower than proper cruise speed when set EPR the engine is not producing the correct value. Once the F/E would set cruise power, they would wait a bit for the engine to stabilize and then see how the speed is holding. If the speed held, then the F/E could take readings of all the engines and compare the condition of each engine. With the same EPR set in each engine, the N1 & N2 speeds along with EGT and FF would give a pretty good comparison of the engine to chart values.

Lou    

Thanks Lou. That explains a lot! And the last paragraph is something that i couldnt even guess about. Its cool you hanging with us :)

EdwardS wrote on Feb 24^th, 2012 at 2:45pm:

Ah, thank you very much. I wasn't sure that FSX was handling that aspect at all. So it is but from our limited resources plotting the affects of it is not really practical.

yep, BUT!!! There is another side.
Planning the flight, calculating EFU, required runway for TO, checklists, tables etc, - that is not required in FSX, youll can fun without it.
But if you want - you can fun with it. So thats for me most of the time :)

Thanks to this forum members we have precisely flying b727,  and tons of info how to fly it :) so digging all that kitchen gives more satisfaction after landing ;)

btw, CoolP said that  B707 fuel tables good for cs707. EPRs -not, but fuel can be planned by Boeing manual. Havent check it yet, but i got 707 waiting for right time ;)

windplayer,

You are spot on!

First, this is a fun game/hobby. Please have fun and explore all the wonderful parts of flight. However, if as some folks have expressed, you want to dig into the nuts and bolts, that's where the Captain Sim planes excel in detail and depth. Sure, there are a few things that are not exactly like the real aircraft, but a lot of the bugs are just part of the FSX architecture.

Second, there are times I just fire up the computer and pick a plane and go fly. Other times I sit down and build a flight plan and make the weather bad, just to keep sharp. I can tell you I have hours of fun flying these planes and also chatting with all of you pilots out there.

Keep having fun!  :)

Lou

Actually I have been flight simming for over two years now. I prefer to make it as accurate while still holding that there are limitations. Over the years I have flown many great payware craft such as the A319, A320, A321, 757, 737NGX, DC10, the list goes on. The only thing I was searching to do with this thread is flesh out fuel planning. Until this point I have, for the most part, depended on other sources for fuel calculations. I did not fully understand aspects such as bias, which doesn't apply to flight sim unless you are flying the 737NGX, supplemental fuel, the applications of crosswinds, tailwinds, and headwinds, et. el. So fun is always first and has been over the years. Not an issue at all but thank you for mentioning it. In hind sight I think I should have opened this thread in the general area since I was not asking about the 727 in specific.

Windplayer if it helps as newcomer, first thing is you cannot compare how you operate a piston engine say in a DC3 with a pure turbine engine they are very different beasts. A piston engine requires a fuel and air mixture be delivered inside the engine in precise amount due to the volume of the area taken up by the pistons, carburettors and fuel injection systems do this work. On a jet engine, fuel is sprayed into a big burner or several burner cans in the front mid section and pressure changes take care of the rest, low at the front high at the back and hey presto gas flows in that direction.

The levers on the pedestal for the engine in an aeroplane like the 727 or 7-7 are of two types the power or main levers simply control fuel flow like a tap the others control fuel like a thingy on a line does. The condition lever or fuel thingy lever lets fuel flow to the engine and shuts if off to stop thats all. The power levers control fuel flow, so they are in effect like a bunsen burner, push them forward more fuel more fire bigger burn more power and that is it, the essence of simplicity like the jet engine, fans at the front compress air in to where it is burnt ones at the back and they may be several convert the hot air resulting from the fuel burning into power or thrust out the back which is why there are two RPM or N gauges on the dash. REverse thrust is just a mechanical connection that means you bring the power levers back so the engines go to idle or low rpm, then moving them all the way back directs linkages which open up the reversing mechanisms vents or doors at the back of the engine to redirect the flow forward and as you pull back the levers they add more fuel and the engines power up to a maximum again but this time the air flow is directed forwards out of the back of the enigne. In a propeller aircraft reverse thrust is achieved by the propeller angles going into a negative pitch and then the engine powering up again.

So in short there is no mixture control in a jet engine as pressures from the outside air pressure, the inside pressures of the engine when burning and turning and the fuel nozzles delivering fuel handle all that so all you have to do to go is levers forward and stop levers back, it is that simple.

Hope this helps, performance planning is another subject all together and there are some good threads on this forum and the 707 forum about fuel settings and planning to help you out.

Thanks CoastalDriver. Now im gone to master 3 degree descend profile you talked about while ago ;) I usualy starting descend at FL*3 nm distance, but sometimes i arriving to target alt too early, sometimes a little late :) now i gonna learn how to stay on profile. that'll surely helps to save some fuel in the end.

I found this chart for 727-200. May be it can be helpful.
:)

www.boeing-727.com/Data/engine/LRC-15%20Chart.PDF

www.scribd.com/doc/60135535/Boeing-727-Performance-Handbook