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Enthusiast Joined: Aug 01, 2006 Posts: 43 Status: Offline

Actually, what i was looking for is during the fuel flow during a ground run. When the throttle is at idle and AB, there is actually a range of values which the fuel will be feeding the engine.

I've another question. I've read the DASH-1 and it says that the EXT centerline tank is transferring at 18000pph whereas the EXT wing tanks are transferring at 30000pph. Any idea why is this so? Or are there any special reasons for it?

thanks for all your help. Very Happy

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Elite 1K Joined: Aug 19, 2004 Posts: 1090

IDCrewDawg wrote:

Raptor_One wrote:

IDCrewDawg wrote:

It doesn't tell you what rate you should see in the TO's because there is no limitation to how much or how little fuel can flow, nor is there a limit to fluctuation in that setting.

Not quite true. In the performance sections of flight manuals you'll find fuel flows for MIL and AB throughout the entire flight envelope. You're also given fuel flow data for a wide range of cruise conditions based on altitude, airspeed, drag index, etc. So you do have some idea of what fuel flow to expect... especially when it comes to MIL of max AB operation.

Since you have this knowledge, I assume you would know the rates. Would you mind posting what is expected. Perhaps the verbage it uses?

V/R
ID

I don't know if you're familiar with the combat flight sim Falcon 4.0, but I helped develop some high fidelity F-16 flight models for it. These flight models covered blocks 15 through 52 and were based on extensive research and lots of round-about calculations. At times we simply had to approximate data. Fuel flow at static conditions is just one area where we simply had to extrapolate. The actual flight model data files contain fuel flow tables as a function of Mach number and altitude just like the thrust tables.

F16and117DCC (not the easiest user name to write out... hehehe) posted that at approximately 5000 ft, stabilized max AB fuel flow at static conditions was 34,999 pph (let's say 35,000 pph even) for an F110-GE-100. In the Block 30 and 40 flight models which have the same engine, we had altitude breakpoints every 10,000 ft with linear interpolation for intermediate values. I just calculated the value based on linear interpolation for Mach 0 and 5000 ft and got 36,953 pph. That's almost 2000 pph too hgih based on the actual 35,000 pph figure we were just given, but considering that is a linearly interpolated value based on two extrapolated data points (i.e. fuel flow at Mach 0 for SL and 10,000 ft), it's surprisiingly close. Like I said though, static fuel flow conditions aren't of much interest to a fighter aircraft able to reach speeds of Mach 2.0 and altitudes above 50,000 ft. It's no doubt of interest to maintainers and engineers as a reference/test point, but pilots spend most of their time in AB well above Mach 0. Wink

Elite 1K Joined: Aug 19, 2004 Posts: 1090

huagulong wrote:

Actually, what i was looking for is during the fuel flow during a ground run. When the throttle is at idle and AB, there is actually a range of values which the fuel will be feeding the engine.

I've another question. I've read the DASH-1 and it says that the EXT centerline tank is transferring at 18000pph whereas the EXT wing tanks are transferring at 30000pph. Any idea why is this so? Or are there any special reasons for it?

thanks for all your help. Very Happy

One of my air force contacts gave me this info a long time ago when I was doing research for F-16 flight models for Falcon 4.0. I forgot I had this info. Luckily, I cut and pasted his comments into a text file for easy reference.

Quote:

i have this..(so far)...at idle the FF is 700-1700 pph..of course what it is in that range will vary with altitude/temp...nozzle should be greater than 94% open with RPM 62 - 80%...FTIT less than 650 deg C....here's some more....for a run-up check... RPM 90%....FF 3200 to 3600 pph, oil press 25 - 40 psi, NOZ POS is 0 -5% and FTIT is ~575 deg C

aha... Smile

MIL or AB t/o... RPM 95 - 104% (106% max)... oil 25 psi min. but less than 65 % psi...nozzle less than 15% after 5 secs at MIL...FTIT stabilize in vicinity of 750 to 850 deg C (not to exceed 935 deg C)...Stabilized FF is between 7500 and 10,000 pph based on rpm... now for AB light off

AB light off within 5 seconds ...oil, rpm, FTIT should remain stabilized for most part indicating MIL power engine parameters when AB is used... FF and nozzle are quite different... FF should rapidly increase to big numbers like 32,000 - 49,000 pph or more... as AB fully lights, nozzle should be 50 - 95%...AB lightoff should be a smooth increase in thrust...

So there you have it. To sumarize, for a Block 30 you should have the following ranges:

idle: 700-1,700 pph
mil: 7,500-10,000 pph
AB: 32,000-49,000 pph

By the way, the approximated numbers I gave in my last post were based on standard atmospheric conditions. Maybe F16and117DCC can tell us what the temperature was for the AB test run he performed in the hush house. If it was warmer than standard day conditions for 5,000 ft in the hush house, that might explain why the number I calculated was nearly 2,000 pph more. The colder the temperature, the more thrust an engine produces. Consequently, the more thrust an engine produces. I would assume an advanced fighter engine like the F110 will automatically adjust fuel flow accordingly, in which case the fuel flow would be less than standard when the temperature is more than standard. Does that make sense? I better quit while I'm ahead.

Enthusiast Joined: Aug 01, 2006 Posts: 43 Status: Offline

Raptor_One wrote:

huagulong wrote:

Actually, what i was looking for is during the fuel flow during a ground run. When the throttle is at idle and AB, there is actually a range of values which the fuel will be feeding the engine.

I've another question. I've read the DASH-1 and it says that the EXT centerline tank is transferring at 18000pph whereas the EXT wing tanks are transferring at 30000pph. Any idea why is this so? Or are there any special reasons for it?

thanks for all your help. Very Happy

One of my air force contacts gave me this info a long time ago when I was doing research for F-16 flight models for Falcon 4.0. I forgot I had this info. Luckily, I cut and pasted his comments into a text file for easy reference.

Quote:

i have this..(so far)...at idle the FF is 700-1700 pph..of course what it is in that range will vary with altitude/temp...nozzle should be greater than 94% open with RPM 62 - 80%...FTIT less than 650 deg C....here's some more....for a run-up check... RPM 90%....FF 3200 to 3600 pph, oil press 25 - 40 psi, NOZ POS is 0 -5% and FTIT is ~575 deg C

aha... Smile

MIL or AB t/o... RPM 95 - 104% (106% max)... oil 25 psi min. but less than 65 % psi...nozzle less than 15% after 5 secs at MIL...FTIT stabilize in vicinity of 750 to 850 deg C (not to exceed 935 deg C)...Stabilized FF is between 7500 and 10,000 pph based on rpm... now for AB light off

AB light off within 5 seconds ...oil, rpm, FTIT should remain stabilized for most part indicating MIL power engine parameters when AB is used... FF and nozzle are quite different... FF should rapidly increase to big numbers like 32,000 - 49,000 pph or more... as AB fully lights, nozzle should be 50 - 95%...AB lightoff should be a smooth increase in thrust...

So there you have it. To sumarize, for a Block 30 you should have the following ranges:

idle: 700-1,700 pph
mil: 7,500-10,000 pph
AB: 32,000-49,000 pph

By the way, the approximated numbers I gave in my last post were based on standard atmospheric conditions. Maybe F16and117DCC can tell us what the temperature was for the AB test run he performed in the hush house. If it was warmer than standard day conditions for 5,000 ft in the hush house, that might explain why the number I calculated was nearly 2,000 pph more. The colder the temperature, the more thrust an engine produces. Consequently, the more thrust an engine produces. I would assume an advanced fighter engine like the F110 will automatically adjust fuel flow accordingly, in which case the fuel flow would be less than standard when the temperature is more than standard. Does that make sense? I better quit while I'm ahead.

Thanks for the info. Btw, do u have any idea for my 2nd question? Regarding the centerline and wing external tank fuel transfer rate.

Elite 1K Joined: Aug 19, 2004 Posts: 1090

I'm not the best person to ask, but I'd guess the different flow rates are to help ensure that all 3 tanks run dry at the same time assuming you're feeding off all 3 tanks. The centerline tank doesn't carry as much fuel so the flow rate might purposefuly be lower. The other reason might be to transfer fuel as fast as possible from the wing tanks since they add significantly to the 'rolling' moment of inertia. The centerline tank is pretty close to the center of mass of the aircraft, so it wouldn't add that much to, umm... Iyy?

Actually the centerline feeds before the wing tanks. To reverse that process for whatever reason you would put the wings first switch into wings first.

Elite 1K Joined: Aug 19, 2004 Posts: 1090

IDCrewDawg wrote:

Actually the centerline feeds before the wing tanks. To reverse that process for whatever reason you would put the wings first switch into wings first.

I probably should have known that just from having played Falcon 4.0. Embarassed

I obviously have no clue why they feed at different rates. I guess it's just how they were designed?

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