How is everybody doing it?  Using FSX's estimation will result in turning your 707 into a glider, even with adding ten or fifteen thousand pounds more.

I flew from KSEA to PHNL (~2300nm) and used about 56% of my fuel. I left with full tanks to gauge the performance. My altitude for the flight started at FL310 and by the time I needed to descend I was at FL350. The fuel burn was around 3500 lbs/hr per engine (14000 lb/hr) at FL310 and about 3200 lbs/hr per engine (12800 lbs/hr) at FL350. If I started at FL350 and eventually climed to FL390 I would have done better, but the plane felt very heavy at FL310 in the first place. So my biggest problem is: What altitude at what weight!

It's a great plane to fly, but it sure is taking some learning!

Mark

Maybe I'm doing this wrong, but I usually fly at around FL280, with a fuel burn rate of roughly 4200lbs/hr per engine.  I use the FS 'fuel and payload' utility for fuel planning. Based on what I calculated from my first couple of flights,I just multiply the figure for estimated fuel burn by four (FS gives you the figure for just one engine) and reduce it to 70%/75% of its value, which gives me enough fuel to carry out the flight plus a comfortable reserve.

FS estimated fuel burn x 4 x 0.7

Never ran dry using that method, although it might not include enough reserves for say a transatlantic (which I still have to attempt sometime over the week end :D )

Cheers

Nico

I had a burn of 4800 lbs/hr at 30,000 with a strong headwind.

ADDITIONAL:

With weather cleared, I burned 3800 per engine per hour at .78, EPR around 1.9.  That would be 15,200 lbs per hour total.  

Divide distance by Speed in knots (450 no wind, 400 westbound, 500 eastbound) to get hours.  Multiply hours by 15,200 (or whatever you think your total burn per hour is).  That should give you your trip fuel.  Add 15,000 lbs for contingencies and reserve (or, again, whatever you please).  That should give you how much fuel to load.

The other side to the fuel burn is airspeed. I think my speed was between M0.82 and M0.84. This is, with cockpit tooltips enabled, the throttles set to 84% to 85%.

Has any one come up with reliable fuel burn figures ?

Yep :)
There is two ways i use.

Download Matt Zagoren performance data from avsim libruary. Search for 707perf.zip

First one can be used for fuel planning for 5-6 hour trips, or shorter. I use it almost every time. Its not precise but it does its job.
longer routes require wind corrections.

1. You estimate your cargo and pax load. assume that 1 passenger weight around 175 lbs.

2. estimate cruise fuel by fuel flow.
(Flight level   - Fuel Flow)

FL 360 FF 3300
FL 350 FF 3500
FL 330 FF 3900
FL 310 FF 4200

Using route length calculate cruise time for groundspeed 470 KTS. You can add wind corrections here, but i didnt found reliable wind data source. I fly in VATSIM almost all the time, so i use vatsim weather, - it may differ a bit from what FSX using as default.
Dont take into account climb time - just take entire route length and divide it to speed. -you'll get time, and multiply FF by that time by 4 engines.

Now you have your AC weight + pax + cargo + cruise fuel weight.

Estimate your takeoff weight by using TO and CLIMB table from Matts data. Estimate TO fuel by table and see if you guessed right, coz there are many tables for different TOGW there.

Add extra fuel for divert and so on, BUT NOT LESS than 10 000 lbs. Dont want to divert\hold, still add 10 000 lbs anyway.

See if you selected suitable flight level (tables will show it), if not - recalculate cruise fuel for lower\higher FL and repeat all steps after that.

Climb as you should, and after reaching your cruise flight level set engine cruise power by using Fuel Flow meters. That'll give you M=0.82 - 0.84 crz speed.

After stabilizing the speed in cruise flight - check how much fuel you burned. It should be close to numbers, CS 707 burn right amount of fuel in climbs.

Use Doppler nav system to get Ground Speed, or use chronometer to measure your average segment speed. (i do that in 727, in 707 i use DNS)
By knowing your speed, every radio fix or waypoint - you calculate how much time left to destination, and how much fuel will you need to reach it. Skip descend in your calculations. By knowing that - estimate how much fuel you will have on arrival.
See if you too heavy for landing, if wind around +-50 kts - you'll be fine

IF you have strong tailwind, like 100 kts - you'll be too heavy to land. Do not take any measures until 1 hour to TOD. Estimate landing weight around 1 hour to Top Of Descend point, and request lower flight level - burn excessive fuel by flying low.

That'll do the trick.  By doing that - i always arrive close to Max landing weight. Very rarely i need to burn fuel by cruising low.


Another way - to use figures from Matt's data, but you'll require reliable wind data. i dont have it. so i dont use it.

If you fly in vatsim you can get wind data by looking at aircraft's speeds along your planned route. Use VatSpy for that. Say you'll fly to the east. You see one 737 flies west at 500kts, one 737 flies east at 400 kts. Assume that steady air speed of 737 will be 450 kts. - you'll have around 50 kts headwind.

Ask questions - i fly 707 regularly.

Currently I do fuel planning as follows:

From several flights I obtained the following empirical numbers for fuel flow during cruise flight:







td] [/td]

Fuel Flow (1,000 pph)	Speed (M)
Altitude (FL)	0.63	0.66	0.70	0.80	0.82	0.827	0.83
100	21.2
150		19.2
250			14.4	18.8
270				17.2
330			11.6	12.8	14.4		15.6
350					13.6
370			9.6	11.8	12.0	12.6
390				10.0	11.2
410				9.6	10,4

01) [Speed of Sound at cruising altitude (kts)]
= IF [Flight Level] > 370 THEN 573.17 ELSE (-0.2378 * [Flight Level] + 660.98) END

02) [True Cruising Airspeed (kts)]
= [Mach Cruising Speed]
* [Speed of Sound at cruising altitude]

03) Estimated [Climb, Descent & Approach Distance on course (nm)] = 130

04) [Cruising Distance (nm)]
= [Flight Plan Distance (nm)]
- [Climb, Descent & Approach Distance on course (nm)]

05) [Time of Cruise Flight (hrs)]
= [Cruising Distance (nm)]
/ [True Cruising Airspeed (kts)]

06) [Cruise Fuel (1,000 lbs)]
= [Cruising Fuel Flow (1,000 pph) from table]
* [Time of Cruise Flight (hrs)]

07) Estimated [Taxi-out Fuel (1,000 lbs)] = 1.3

08) Estimated [Takeoff & Climb Fuel (1,000 lbs)] = 12

09) Estimated [Descent & Approach & Landing Fuel (1,000 lbs)] = 5

10) Estimated [Taxi-in Fuel (1,000 lbs)] = 0.9

11) [Fuel Required (1,000 lbs)]
= [Taxi-out Fuel]
+ [Takeoff & Climb Fuel]
+ [Cruise Fuel]
+ [Descent & Approach & Landing Fuel]
+ [Taxi-in Fuel]

12) [Diversion-to-Alternate Fuel (1,000 lbs)]
=
(
IF ([Distance to Alternate (nm)] - [Climb, Descent & Approach Distance on course (nm)] < 0
THEN 0
ELSE
([Distance to Alternate (nm)]  - [Climb, Descent & Approach Distance on course (nm)]
END
)
/ [True Cruising Airspeed (kts)]  
* [Cruising Fuel Consumption (1,000 pph)]
+ [Takeoff & Climb Fuel (1,000 lbs)]
+ [Descent & Approach & Landing Fuel (1,000 lbs)]

13) Estimated [Holding Fuel (30 min @ 225 KIAS, 1,000 lbs)] = 5.2

14) [Safety Addition (10%) (1,000 lbs)]
= 0.1
*
(
[Fuel Required (1,000 lbs)]
 + [Diversion Fuel (1,000 lbs)]
 + [Holding Fuel (30 min @ 225 KIAS, 1,000 lbs)]
)

15) [Total Fuel (1,000 lbs)]
= [Fuel Required (1,000 lbs)]
+ [Diversion Fuel (1,000 lbs)]
+ [Holding Fuel (30 min @ 225 KIAS, 1,000 lbs)]
+ [Safety Addition (10%) (1,000 lbs)]



I do not take into account
- the actual weight of the airplane
- cruise climbs
- actual pressure altitude
- ...
- ...
but it works well enough.

--------------
Markoz:
What altitude at what weight?

Derived from the Pan Am 707-300 Aircraft Operating Manual:

0.82M Cruise Optimum Altitudes:
Gross Weight (GW) <= 205,000 lbs : FL410 / FL390
GW <= 265,000: FL370
GW <= 275,000: FL350
GW <= 315,000: FL330 / FL320

Long Range Cruise Optimum Altitudes (0.805M … 0.806M):
GW <= 195,000: FL410
GW <= 215,000: FL390
GW <= 275,000: FL370
GW <= 295,000: FL350
GW <= 315,000: FL330




Best regards
Alex

you guys are great, this is exactly what I was looking for, I am devouring the info right now and will get back if any questions

"Matt Zagoren performance data" what a gem this is

:)

I've just finished an around the World Tour with the 707, travelling 5-9 hours long steps. The Way i am calculating it is , the aircraft Burns around 15000 lb/hour. Multiply that with the duration of the flight and add 15 percent. Fill up the main tanks first, and add the remaining amount in the center tank. Burn first the fuel in the center tank, then the main tanks.

BR,
Anders

AndersCN wrote on Aug 30^th, 2013 at 12:24pm:

I've just finished an around the World Tour with the 707, travelling 5-9 hours long steps. The Way i am calculating it is , the aircraft Burns around 15000 lb/hour. Multiply that with the duration of the flight and add 15 percent. Fill up the main tanks first, and add the remaining amount in the center tank. Burn first the fuel in the center tank, then the main tanks. BR, Anders

Good stuff, nice n simple.

Im struggling to find info on the cross feeds. I left them all open but lost the 2 outer engines. What order do we run them in and what to do when a tank runs dry?

Zoran:

Refueling Procedure:
Proceed as follows until your intended amount of fuel is reached:
1.  Load all main tanks equally.         (4 x 15,500 lbs = 62,000 lbs  =   62,000 lbs)
2. After #1 and #4 main tanks are full, continue to load #2 and #3 main tanks.      (+ 2 x 11,760 lbs = 23,500 lbs  =   85,500 lbs)
3. After all main tanks are full, load reserve tanks.      (+ 2 x   2,900 lbs =    5,800 lbs  =   91,300 lbs)
4.  After all wing tanks are full, load the center tank.      (+ 1 x 68,300 lbs = 68,300 lbs  = 159,600 lbs)

Fuel Management:

Check periodically:
IF Center Tank exceeds 20,000 lbs AND less than 12,000 lbs of total fuel consumed
THEN “Center Tank to Outboard Engines, Main Tanks to Inboard Engines”:
- Boost Pump Switches in Main Tanks 1, 2, 3, 4 & Center Tank....ON
- Crossfeed Selectors No. 2 & 3....CLOSE
- Crossfeed Selectors No. 1 & 4....OPEN
ELSE
IF Center Tank contains less than 20,000 lbs OR 12,000 lbs or more consumed
THEN “Center Tank to All Engines”:
 - Crossfeed Selectors No. 1, 2, 3 & 4....OPEN
 - Boost Pump Switches for tanks No. 1, 2, 3, 4 & Center....ON
ELSE (Center Tank empty)
  IF Fuel amount in Inboard Tanks > Fuel amount in Outboard Tanks + Reserve Tanks
  THEN balance main tanks: "Inboard Tanks to all Engines"
  - Crossfeed Selectors No. 1, 2, 3 & 4....OPEN
  - Reserve Tank Transfer Valves No. 1 & 2....OPEN as soon as Tank No. 1 ( No. 4) can take in whole content of left (right) reserve tank
  - Boost Pump Switches for tanks No. 1, 4 and Center....OFF
  - Boost Pump Switches for tanks No. 2 & 3....ON
  - 2nd Boost Pump Switch for Tank No. 2 or 3, whichever has less fuel....OFF for balancing
  - Center Tank Boost Pumps....OFF
  ELSE
   IF Inboard Tanks = Outboards + Reserves:
   THEN “Each Main Tank to its Engine”:
   - Boost Pump Switches in Main Tanks No. 1, 2, 3  & 4....ON
   - Center Tank Boost Pumps....OFF
   - Crossfeed Selectors No. 1....OPEN
   - Crossfeed Selectors No. 2, 3 & 4 ....CLOSE


Best regards

Alex

Thanks Alex that should keep me in the air:-) I will print it out for my next trip

cheers
zoran

I'd start a new topic for this, but I can't.  (Only 47 more posts to go.  Sheesh.)

Can anyone advise on the real-world full-throttle fuel consumption (SFC) at sea level, standard day for the -300C (assuming JT3D-7 engines)?

(Or the JT3D-3B.)

Many thanks.

Addendum - Refueling Procedure: how to compute the fuel amount for each tank

|TF = Total Fuel (1,000 lbs)	| Tank 1/4	| Tank 2/3	| Reserve Tank L/R	| Center Tank	|
|   0     <= TF <=   62	| TF * 0.25	| TF * 0.25	| 0	| 0	|
| 62     <= TF <=   85.5	| 15.5	| TF * 0.5 - 15.5	| 0	| 0	|
| 85.5  <= TF <=   91.3	| 15.5	| 27.25	| TF * 0.5 - 42.75	| 0	|
| 91.3  <= TF <= 159.6	| 15.5	| 27.25	| 2.9	| TF - 91.3	|