Boeing 707-320C fuel flow

[joscyriacv2]

Boeing 707-320C
Gross Weight: 95.3 tonnes
Speed: M0.82
EPR: 1.30

Fuel flow is 730kgs per engine totalling 2920kgs an hour. Im no pilot but shouldnt the fuel flow be higher as expected for a 707? LIke maybe 6000kgs an hour?

[aerofoto - HJG Admin]

Using the aircraft base pack/s, FDE/s, and the correct aircraft panel versions ..... as provided by us "HERE" .... my own B707-320B (early production), -320B ADV, and -320C simulations are demonstrating the following fuel burn indications for my stated cruising altitude and airspeed/MACH velocity :-


1. B707-320B (EARLY)

FL310 CRUISE PERFORMANCE (following MGW T/O)

IAS = 314 KTS
MACH = 0.82.4
TAS = 483 KTS
EPR = 1.48
N1 = 88.1%
EGT = 416*C
N2 = 89.1
F/F = 2,595 LBS (per hour/per engine X4)
AI Pitch = +1*


2. B707-320B ADVANCED

FL310 CRUISE PERFORMANCE (following MGW T/O)

IAS = 314 KTS
MACH = 0.82.4
TAS = 483 KTS
EPR = 1.41
N1 = 84.9%
EGT = 409*C
N2 = 87.0
F/F = 2,535 LBS (per hour/per engine X4)


3. B707-320C

FL310 CRUISE PERFORMANCE (following MGW T/O)

IAS = 314 KTS (per hour/per engine X4)
AI Pitch = +1*

MACH = 0.82.2
TAS = 482 KTS
EPR = 1.41
N1 = 79.4%
EGT = 397*C
N2 = 84.2%
F/F = 2,555 LBS (per hour/per engine X4)
AI Pitch = +1*


Totally coincidental to your query I only recorded, and compiled, this data recently .... to form part of my "new" and slowly advancing B367/B707/720 manual.

The question/s I pose in relation to you query is/are :-


1. What, if anything, have you done to your FDE .... particularly in regard to the FFS value ?

2. Precisely what panel version are you using with your B707-320C .... of course I can see which panel configuration you're using, but, we offer at least 3 "different" panels which fit that particular configuration, so, I need to know precisely what one you're actually using.

3. Need you to also confirm you're using the "our" B707-320C aircraft base pack FDE.


Expect indicated F/F and airspeed (IAS) to reduce with altitude gain .... and I the event you have an incorrect panel/aircraft base pack/FDE configuration then that would result in incorrect indications.

Im no pilot but shouldnt the fuel flow be higher as expected for a 707? LIke maybe 6000kgs an hour?

More like 10,000 LBS to 12,000 LBS "across all 4 engines" (and which is pretty much what I'm recording anyway) .... depending on aircraft weight, power setting, and OAT, etc.



I need a response from you in regard to my above 3 queries


And just as a comparison with my own above 3 B707 performance observations .... here's what I'm recording in regard to my own CFM-56 powered B707-700 simulation ....


4. B707-700

FL310 CRUISE PERFORMANCE (following MGW T/O)

FL310 CRUISE PERFORMANCE

IAS = 315 KTS
MACH = 0.82.3
TAS = 482 KTS
N1 = 63.1%
EGT = 353*C
N2 = 78.4%
F/F = 1,759 LBS (per hour/per engine X4)
AI Pitch = +1*


Mark C
AKL/NZ

[aerofoto - HJG Admin]

I just thought to comment additionally and as follows ....

REMEMBER .... I'm quoting LBS (pounds) and not KG's (kilograms) .... as the instrumentation on all B707's was calibrated to read in accordance with imperial measurements .... so far as I'm aware.

My roughly 2,500 LBS F/F (per engine/per hour .... and in imperial measurements) at 31,000 FT therefore equates to around 1,150 KG's (metric ... if my conversion is correct) .... and you appear to have been cruising at around 8,000 FT higher than me, so, given the altitude variation and its impact on F/F indication then maybe it could conceivably go that low.

shouldnt the fuel flow be higher as expected for a 707? LIke maybe 6000kgs an hour?

In the case of the early turbojet powered B707's I s'pose it could approach that (across all 4 engines .... again depending on , altitude, weight, power setting, OAT etc), but, not in regard to the later fanjet technology which was quieter, cleaner, a considerably more fuel efficient (for the time) too

Mark C
AKL/NZ

[joscyriacv2]

Hi Mark. Here are your answers:

1. No. The FDE hasnt been touched, nor the aircraft.cfg or the fuel flow scalar. I don't usually tinker around with HJG files becuase i believe they are pretty accurate. The fuel flow scalar value is 1.04 at the moment.

2. The panel version being used is "b707-320bc_panel_adv_1970". The "B707-320B/C "1970" " panel. I doubt even a wrong panel would have any effect on the fuel flow.

3. Yes im using the stock B707-320C files from HJG all separately downloaded and joined together.

I compared one of my flight reports from 2016 and i observed it was giving fuel flow figures of approx. 12500lbs an hour albeit the takeoff weight being 5 tonnes lighter. Link: www.afva.net/pirep.do?id=0x20c19 . If you click the Flight Data checkbox, you can click and obtain flight data for various ballon points at cruise. Sadly, today's flight wasnt done for any VA so i dont have any pireps you could check. But yes the fuel burns were very off. In fact i felt if i could double the FFS value i may obtain a realistic fuel flow although i haven't tried it yet. This was the first 707 flight after a complete FS reinstall although other a/c are having no issues.

Fuel planning with performance charts gave me an approx fuel burn of 10,434lbs an hour whereas this wasnt the case. Maybe it had to do something with the reinstall. I'll try downloading a fresh copy of the files and try again. I might fly again in a couple of days so I'll know.

[aerofoto - HJG Admin]

I had even (earlier) considered you might possibly have been using the B707-700 FDE for your B707-320C by mistake .... simply because it's fuel burn rate of some 1,700 LBS per engine/per hour (at 31,000 FT) equates to around several hundred KG's per hour .... BUT .... that hypothesis doesn't fit either because your presentation indicates you were at 39,000 FT (I routinely seldom go beyond 31,000 FT .... at which altitude all of my cruise performance data is recorded .... its a god altitude at which to base such observations) where I'd expect the F/F indication to be a bit lower still.

I doubt even a wrong panel would have any effect on the fuel flow

It "shouldn't" in regard to F/F .... unless the wrong FDE is being used .... but which you assure us isn't the case.

It "can" however though in regard to engine power indications .... because most (of our own) engine gauges are programmed/calibrated in accordance with different engine types with their different thrust ratings and which is reinfornced by the FDE too .... so again .... "IF" a wrong panel assignment (not saying this's the case in your case) was applied then it could influence F/F .... especially "IF" a wrong base pack/FDE assignment is also applicable.

I compared one of my flight reports from 2016 and i observed it was giving fuel flow figures of approx. 12500lbs an hour albeit the takeoff weight being 5 tonnes lighter

12,200 LBS (pounds) per our is about what I'd expect .... and also fairly accurate .... BUT ONCE AGAIN .... such indications are going to be dependent upon/influenced by "weight, altitude, power setting, and OAT"

i felt if i could double the FFS value i may obtain a realistic fuel flow

I wouldn't encourage that .... as it would then "bugger-up" fuel flow indications right throughout their range from seal level to cruising altitude .... so definitely not a good idea

Fuel planning with performance charts gave me an approx fuel burn of 10,434lbs an hour whereas this wasnt the case

I need to explain that HJG F/F indications are generally very accurate "at sea level" .... but .... due to the way FS functions we have to accept whatever these become by cruising altitude .... and which can result in nominal plus or minus indication. FS is good in a lot of scenarios .... but .... due to the limitation of its manipulable parameters it's no so crash-hot in respect of other/all scenarios .... so .... their needs to be "a little tolerance" in regard to the use of RW performance data. We use that data too .... to get us into the ball park performance-wise .... but .... FS, due it the way its' engineered, will always have the "final say" .... as will always be evident per various gauge indications and which do, sometimes, need to be taken with a grain of salt.


I've never known FS indications in imperial LBS to be too inaccurate .... but .... I've never set it in accordance with metric KG's .... any discrepancy (at a guess only) may be in regard to the way FS interprets/converts this particular data.


What you could do .... before you try reinstalling anything (and which probably won't change anything anyway) is .... set FS to read fuel quantity in accordance with "pounds" (LBS) .... then .... repeat your B707-320C flight up to the same altitude. I'll do similar .... later (this could take me a couple of days though) and we'll compare our observations.

I'll look at this later .... but .... it ay be a day or so before I can report .... just a lot happening at the moment


Mark C
AKL/NZ



I'll look at this later .... but .... it ay be a day or so before I can report .... just a lot happening at the moment

[Mike Monce - HJG]

I will also do a quick check on the FFS at sea level to make sure it matches the engine spec

Mike

[aerofoto - HJG Admin]

Thanks Mike

The B707's are now among our oldest FDE'a .... and are probably in need of an update given what we learned over the past 12 years and now know how to do .... just as our DC-8 FDE's recently benefitted (during 2015).

Mark C
AKL/NZ

[aerofoto - HJG Admin]

What an enjoyable excercise

It's been a while since I've flown any of our B707's.

It's lucky I had/made time to be able to do it at all today though .... it won't hurt other HJG work to be delayed by 1 more day I guess


ANYWAY .... here's my test report ....


I took our B707-320C up to 39,000 FT .... and prior to getting there (and back down again) here's the observations I've recorded ....

FUEL FLOW & ENGINE SPEED AT GROUND IDLE

F/F = 642 LBS
Engine N1/N2 = N1 28.7% / N2 59.3 %

I loaded my B707-320C as for a MGW departure .... based on a "full payload" and then the following fuel (only) adjustment ....

FUEL & PAYLOAD

LEFT AUX = 100%
LEFT = 95%
CENTER = 92.3%
RIGHT = 95%
RIGHT AUX = 100%
CENTER 2 = 100%
CENTER 3 = 100%

With no payload adjustment the above fuel loading resulted in a 20 LB overload prior to taxi .... "stuff all"

For my B707-320C, and this test, I opted to use our classic 1965 B707-320B ADV/B707-320C configuration.

Prior to departure the simulation was configured as follows ....

TRIM = 3 units
T/O FLAP SETTING = 23* (2X notches)

T/O V-speeds were calculated as follows ....

V1 = 148 KTS (at MGW)
VR = 155 KTS (at MGW)
V2 = 170 KTS (at MGW)
V-REF = 158 KTS (at MGW)

MAX T/O THRUST = N2 100%
MAX T/O THRUST F/F = 8,200 LBS

The above T/O power and F/F indications will vary in accordance with airport altitude and weather temperature environments.

Following T/O the simulation was flown approximately as follows ....

INITIAL CLIMB RATE = 1,500 FPM (prior gear/flap retraction)
FLAP 23* RETRACT SPEED = 200 KIAS
FLAP 14* RETRACT SPEED = 220 KIAS
AFTER T/O (after clean-up) CLIMB THRUST REDUCTION = N2 92.5% .... and the ROC then increased to 2,500 FPM

The simulation was then climbed approximately in accordance with the following alltitude, ROC, and power adjustment schedule ....

- Maintain 2,500 FPM ROC and approx N2 92.5% until 10,000 FT
- 10,000 FT reduce ROC to 2,000 FPM - maintain approx N2 92%
- 20,000 FT reduce ROC to 1,800 FPM - maintain approx N2 91%
- 24,000 FT reduce ROC to 1,500 FPM - maintain approx N2 90%
- 27,000 FT reduce ROC to 1,200 FPM - maintain approx N2 89%
- 30,000 FT reduce ROC to 1,000 FPM - maintain approx N2 88%
- 30,200 FT reduce ROC to 800 FPM - maintain approx N2 87%
- 30,500 FT reduce ROC to 500 FPM - maintain approx N2 86%
- 30,800 FT reduce ROC to 200 FPM - maintain approx N2 85%
- 31,000 FT ALT CAPTURE - maintain approx N2 84%

At 31,000 FT flight performance was noted as follows ....

IAS = 314 KTS
MACH = 0.82.1
TAS = 484 KTS
EPR = 1.33
N1 = 79.6%
EGT = 398*C
N2 = 84.3%
F/F = 2,557 LBS (X4 = 10,228 LBS per hour in total)
AI Pitch = +1*

At 35,000 FT flight performance was noted as follows ....

IAS = 286 KTS
MACH = 0.82.1
TAS = 472 KTS
EPR = 1.38
N1 = 81.4%
EGT = 380*C
N2 = 89.4%
F/F = 2,315 LBS (X4 = 9,260 LBS per hour in total)
AI Pitch = +2*

The increased AI pitch attitude was undoubtedly a result of the simulations weight being being in excess that desirable for this cruising altitude .... at a reasonably early stage following departure.

At 39,000 FT flight performance was noted as follows ....

IAS = 257 KTS
MACH = 0.81.6
TAS = 467 KTS
EPR = 1.43
N1 = 83.7%
EGT = 378*C
N2 = 85.5%
F/F = 2,046 LBS (X4 = 8,184 LBS per hour in total)
AI Pitch = +3*

Again .... the further increased AI pitch attitude was undoubtedly a result of the simulations weight being being in excess that desirable for this cruising altitude. I therefore simulated a significant fuel burn-off .... to approximare what should be the case prior to TOD .... and noted the following flight performance ....

IAS = 262 KTS
MACH = 0.82.8
TAS = 474 KTS
EPR = 1.40
N1 = 81.9%
EGT = 376*C
N2 = 84.5%
F/F = 1,070 LBS (X4 = 7,880 LBS per hour in total)
AI Pitch = +1*

The airspeed and F/F improvements are a direct result result of signifant weight reduction .... as should be expected close to TOD and nearing the end of any flight.

Simulated weather envvironents and less than MGW operations will likely influence the above recorded performance observations


IN SUMMARY ....


On the basis of how I load, and fly, our B707's (and most of our other simulations too) I can't see anything abnormal .... in either performance or F/F indications for power setting, altitude, and simulated weather environment too.

I'm comfortable endorsing all is well .... but .... these simulations do need to be flown properly in order to be able to perform correctly of course

It needs to be noted though that our B707 FDE's are, by now, among our oldest .... and are due for an overhaul. This was actually commenced, by me, early last year (or it might have been a bit earlier) .... in particular to improve landing attitude/performance of these simulations, but, has had to be shelved due to other HJG priorities both during the past 12 months and currently.

Here's a few images from this/my test flight of today







Mark C
AKL/NZ

[joscyriacv2]

So, that's it then. Your FL390 cruise figures and after-fuel burnoff figures seems just about matching with my observations. I was beginning to think there was something wrong with mine. The comparison i made with my Panam flight was wrong to begin with. The aircraft used there was a Boeing 707-320, not a B or C. I think that'll also affect due to variations in engine and design.Finally, i believe even atmospheric conditions have a say in all this, although how much it effects in FS is still unknown to me. Anyways, I'll do another 707 flight in a couple of days and see what happens. Pretty curious now

Here's a few shots from my flight in question:
Uganda 750 enroute Entebbe - Dar Es Salaam

[aerofoto - HJG Admin]

Your FL390 cruise figures and after-fuel burnoff figures seems just about matching with my observations

So long as you're getting fuel burn indications (for power setting, altitude, and operating weight) that "approximate" those observations I've quoted above and "in LB's" (measurement of imperial pounds) too .... THEN .... you're absolutely fine

Again .... I never use metric KG's with these simulations.

The aircraft used there was a Boeing 707-320, not a B or C. The comparison i made with my Panam flight was wrong to begin with.

The turbojet powered -320 is an "entirely different beast" from the later -320B, -320B ADV, and -320C .... in terms of its wing, weight, and engine thrust .... and the similar (to the -320) B707-420 is sligtly different again by virtue of its RR CONWAY engines performance (notably in regard to F/F indications) too.

The -320B, -320B ADV, and -320C vary slightly also (particularly in regard to the first of this particular line .... the -320B .... which was somewhat underpowered due to its lower engine thrust rating) .... again primarily due to weight, engine thrust, and sharing a later/different wing that the earlier B707's.

These variations were incorporated into each of these simulations as best we could at the time .... some 12 years ago .... and knowing what we know, and can do, now I know just how much we can further improve them (as we recently did with all our DC-8's). Although started .... that's another FDE upgrade project and one I won't speculate on in regard to its eventually becoming availabile.

i believe even atmospheric conditions have a say in all this, although how much it effects in FS is still unknown to me

In the past I've noted most simulations tend to climb "faster" in simulated "cooler" temperature environments .... promoting a slightly higher ROC in order to aid keeping airspeed in check .... but .... I now never use imported weather environments, nor manipulate FS weather scenarios either .... beyond the types of cloud I want, their altitudes and coverage, and visibility too.

Here's a few shots from my flight in question: Uganda 750 enroute Entebbe - Dar Es Salaam

Nice to see textures by our staff member .... the late John KEANE and to whom the recently released HJG B737 project is dedicated in memory of ....
tonymadgehjg.proboards.com/thread/5323/rip-john-keane

getting some well deserved virtual air time .... and forum exposure too

Mark C
AKL/NZ

[aerofoto - HJG Admin]

Just on the subject of John's UGANDA AIRLINES B707 liveries ....

Every time I see those liveries I always seem to think about the following satiric song ....

The "IDI AMIN" song (1976)
www.youtube.com/watch?v=MFeJJAQPiK4

AMIN's only known reaction to this particular song is reputed to have been .... "DA PEOPLE HOO WOTE AND POBLISHED DAT SONG DAY ALL SHUD BE SHOT FOR DOING DAT" .... or words to similar effect

Mark C
AKL/NZ

[Mike Monce - HJG]

Wow, there was a lot of dust on that airplane!

Anyway I just did a a fuel flow test on the 320B. I don't have a 320C installed but the engines are not that different and the sfc isn't either. The way I test is this:

1)I do not necessarily trust the FF gauge on the panel as it's subject to error depending on the coding.

2) So, my procedure is to run 1 engine at 100% N1 at sea level for 1 minute using the clock on the panel. That gives FS time of 1 minute which can actually be a bit off from real world 1 minute due to computing resource use. Lacking a clock on the panel I then use real world time.

3)I go into the Fuel and Payload menu and note the initial fuel load, wait 1 minute on whichever clock I'm using, and then back to the F&P menu to get the final fuel load.

4) take the difference, multiply by 60 and you have the FF/hour in lbs.

5) Compare to real engine data: www.jet-engine.net/civtfspec.html and adjust the cfg FFS accordingly

For the 320B it uses PW JT3D-3B rated at 18,000 with a SFC of 0.51 which gives a FF of about 9200 lbs/hour. I measured 8500 lbs/hour for the 320B. That tells me our FFS scalar is low by about 9%. For that particular model I would recommend upping the FFS by 9% which means changing from 1.15 to 1.24.


As Mark mentioned, these FDE's a fairly old and in need of revision. I don't think it would be out of the question to up the FFS in your plane by about 9% if you wish. Or just perform your own test using the above guidelines and then make an adjustment based on your findings.


Mike

[Herman]

Found this on the Airliners web site. It lists fuel consumptions for a lot of airliners. Scroll down for the 707's.
No idea how this information was acquired or hoe accurate it is.

www.airliners.net/forum/viewtopic.php?t=1355819

Herman

[joscyriacv2]

Thank you guys. Doing a bit of googling, i found this. I'd call it sacrilege.
www.flightsim.com/vbfs/showthread.php?298315-Libardo-Guzman-Boeing-707-Excessive-Fuel-Consumption

[aerofoto - HJG Admin]

Found this on the Airliners web site. It lists fuel consumptions for a lot of airliners.

RW F/F data "is" interesting .... and helpful too .... BUT .... as I mentioned near the very start of this thread, in FS we can usually get F/F indications almost spot on at sea level, however, we then have to accept what ever these translate to by cruising altitude, so, they're always going to "out", plus or minus, by a wee bit (and that's just the way FS is .... and what happens) .... so .... some folk (perhaps) need to be conscious of this

What we currently have was compiled "12 years ago" .... based on the best of data we had back then and which was applied in accordance the best of our abilities back then also .... BUT .... we have access to far better data now and have learned a hell of a lot more since too.

I measured 8500 lbs/hour for the 320B. That tells me our FFS scalar is low by about 9%. For that particular model I would recommend upping the FFS by 9% which means changing from 1.15 to 1.24.

I'd go with .... and are indeed happy to endorse .... Mike's FFS recommendation above (editing the FFS value .... for the "B707-320B ADV" (not the standard B707-320B early production version though) and "B707-320C" only .... to read "1.24".

That, as Mike states, will result in "an improvement" .... essentially resulting in a roughly 9-10% increase in the indicated F/F rate right throughout both earthly to heavenly regimes.

I've never known Mike to provide bad data

Mike .... I'll be in touch with you "privately" concerning this and in due course, so, start logging some B707/720 virtual air time .... when you can. This project will be far easier and much quicker than the similar one we recently undertook for all of our DC-8's. This thread has "sparked my interest" now

i found this. I'd call it sacrilege

I wouldn't be too hard on Libardo.

He's a nice guy .... I actually know, and have met him, personally .... "in Colombia" ... and even had him around home few times in Bogota.

He's loves B707's .... but then again .... most of us here do also

The FDE which accompanies Libardo's B707's is actually "the very first" data HJG compiled (between 2001 and 2005) .... before we/the new HJG upgraded this to what we've currently had since 2006.

That old FDE was actually compiled for FS2000 and FS2002 (and which was made known to him, at the time by our suggesting he could update it himself .... I don't know whether or not he did so though .... but he's sure have had to do some editing given the COG position in his model would like be at variance to that of our own models) .... and which (whilst it works in FS2004 .... and possibly FSX too) is why some of its parameters will be off-spec in both FS2004 and FSX.

The HJG development team do, from time to time, assist "selected" other FS developers and groups .... "IF" it's convenient and/or within our abilities to do so

I read the first posting by that guy within JOSCYRIACV2's link .... and never bothered reading any further. At MACH 0.84 .... and at 28,000 FT too .... the guy's flying way too fast and at way too low an altitude too.

I sometimes feel we're entering an era where some people (particularly the younger generation whom may never have seen, or flown on, B707's and DC-8's) really have little knowledge in regard to how these classic jetliners were actually flown .... and as a result they're probably inclined to want to fly them more in accordance with what they know about B757's, B767's, and other much later generation aircraft type performances.

The "BASIC" flying guides we compile and provide within each of our forum based manuals/"PANEL INSTALLATION & HANDLING NOTES" (whilst a couple of these earlier ones do now require updating too) are intended to "assist/guide" folk in regard to this .... crossing the bridge (so to speak) .... back to another much earlier time when civil jet airliners not only looked and sounded different, but, flew and were also flown differently too

Mark C
AKL/NZ