Under-modelled power

[britgliderpilot]

What loadout, SK? Most people complain about the loaded aircraft, not clean config.

 

Could be the stores are just extra draggy ;)

 

. . . . . . Well yeah, but what are the figures in the dash one for, too?

 

If people are comparing a loaded aircraft to an unloaded one, then that's an obvious drawback :P

[Kula66]

One thing that is for sure is that the A-10 is underpowered but I still think it handles really good in LO.

 

Agreed,

Loops and turns a dream as long as you stay at 300ish.

... but then in RL its supposed to be underpowered.

[SwingKid]

What loadout, SK? Most people complain about the loaded aircraft, not clean config.

 

Good point - I tested only a clean F-15C with full fuel. I think someone did mention that the stores drag model may cause discrepancies.

 

I purchased the F-15A/B/C/D Dash-1 from http://www.eflightmanuals.com

 

-SK

[Kula66]

SK,

Any chance you could quote figures to say 10k, 20k and 40k feet? Also what speed should you be when you get there??

 

BTW: Did you export it? ;)

[SwingKid]

IIRC, it took about 30 seconds to reach 350 KCAS with full burners, then another 24 (?) seconds to reach 32,000' at Mach 0.95.

 

-SK

[phantom_fly85]

Don't even bother. You know what the answer is.

 

The F-15C will get its due attention eventually, as will the flanker and all the other planes, I'm sure.

 

I was joking about the grenade. I know this issue has been discussed over and over.

 

:pilotfly:

[phantom_fly85]

Thats like the problem Falcon 4 used to have. The stores were too draggy in the 1.08 patch. This was then fixed in the Superpacks and it flew like a dream then when fully armed.

 

One thing that is for sure is that the A-10 is underpowered but I still think it handles really good in LO. The MiG, I know is a high T/W ratio fighter even when fully armed but I feel it's a little overpowered.

 

The differences between Falcon 4.0 Superpack 3 and 4 are amazing. The research to get SP4 on the right track had taken many months, but the community was rewarded with a better product. Many of the sim community at Frugals were complaining about how long it would take to release SP4 and the development team's response was always "3-4 weeks." Kind of funny now in hind sight. Falcon:AF came out of nowhere and now it's better in some regards, but did take a step back from where BMS was leading the way.

[iVIPER21]

When I took out the time-to-height charts for the F-15C from its Dash-1 flight manual and compared them to Lock On, they were dead on. To the second.

 

Exactly correct.

 

Remember that we are flying a late 1970's / early 1980's Eagle with the Pratt & Whitney F100-PW-100 engines, not the newer upgraded -220 or -229 engines. So what you see at an airshow today is not what you fly in Lock-On.

 

Finally, as stated before, the effect of configuration and loadout will also change the allowable load factor with regard to structural limits - which will limit maximum sustained turn rate and affect many other performance factors. Overall, I think we get a pretty decent flight model for $30.

[Pilotasso]

Consider that the F-15's also increased in weight, wich ultimatly leads to similas T/W perfomance but lower wing loading.

[Cobra360]

The -220 is actually slightly less powerful than the older -100s. The -220 is seen as an upgrade in terms of reliability and behaves better when worked hard by the pilot with multiple throttle slams from idle to burner and back without any fear of a compressor stall or flame-out, it also respons quicker to throttle inputs.

[britgliderpilot]

The -220 is actually slightly less powerful than the older -100s. The -220 is seen as an upgrade in terms of reliability and behaves better when worked hard by the pilot with multiple throttle slams from idle to burner and back without any fear of a compressor stall or flame-out, it also respons quicker to throttle inputs.

 

True dat.

 

To the best of my knowledge, the -229 hasn't been fitted to the F-15C, either . . . . only the F-15E.

 

 

Pilotasso, I think you've tripped up here . . . . . how does an increased weight for the same wing area lead to a decreased wing loading?

 

The T/W, if anything, has decreased over the years, not remained similar . . . .

[iVIPER21]

The -220 is actually slightly less powerful than the older -100s.

Which brings up an interesting point: According to Pratt & Whitney's website, the F100-PW engine family ranges in thrust from "23,770 - 29,160 lbs." which is contrary to USAF's F-15 factsheet which states "Thrust: (C/D models) 23,450 pounds each engine". Thoughts?

[S77th-GOYA]

I can't say for sure about modern jets, but from seeing WWII manuals compared to actual a/c tests, the manuals are almost always quite conservative with speed and power figures. It sure would be nice to see some test data from an actual combat F-15C as opposed to the Streak Eagle. Of course, then they would have to shoot me.

[Cobra360]

Which brings up an interesting point: According to Pratt & Whitney's website, the F100-PW engine family ranges in thrust from "23,770 - 29,160 lbs." which is contrary to USAF's F-15 factsheet which states "Thrust: (C/D models) 23,450 pounds each engine". Thoughts?

Yep. the -100 can produce anywhere from 23,770-29,000lbs. The -100s are by default left at the 23,7 power rating to last longer. While they can be up-trimmed to produce 29k as were installed on an F-15D airframe acting as a proof of concept for the first F-15E.

 

The C/D are rated at 23,450lbs but these too can be up-trimmed to give more power at the expense of longer life.

 

BTW the surviving USAF fleet of around 150 Eagles are due an engine upgrade in the next 5-10 years which will be good to see.

[GGTharos]

Umm, no ... actually the F100-PW is a whole family of engines ...e ach producing different amounts of thrust. AFAIK.

[britgliderpilot]

Umm, no ... actually the F100-PW is a whole family of engines ...e ach producing different amounts of thrust. AFAIK.

 

Yup.

 

 

F100-PW-100 is one engine, fitted to F-15A/B and early F-15C/D

 

F100-PW-220 is same family, but different spec, fitted to F-15C/D

 

F100-PW-229 is same family again, but is yet another spec and only fitted to the F-15E.

 

The -XXX refers to the last three numbers, not the first three.

 

 

Read somewhere that apart from anything else, the -229 is heavier than the other two version . . . . shrug.

[Cobra360]

Yep the 229 is heavier and needs extra cooling. Cooling ducts are installed at the rear of the CFTs used on the F-15E and have been modified when newer versions of the CFTs were developed, There were 3 or 4 different versions of the CFT. The latest I think are the dash 4E CFTs.

[Cobra360]

Umm, no ... actually the F100-PW is a whole family of engines ...e ach producing different amounts of thrust. AFAIK.

 

But my statement was very much true. The -100 was up-trimmed to around 29k thrust when used on the F-15D test airframe for the F-15E program. There were limited -220s at the time as they were going into F-16s and the early F-15C/D were being refitted with them so that why the -100s were used for that.

[Cobra360]

Yup.

 

 

F100-PW-100 is one engine, fitted to F-15A/B and early F-15C/D

 

F100-PW-220 is same family, but different spec, fitted to F-15C/D

 

F100-PW-229 is same family again, but is yet another spec and only fitted to the F-15E.

 

The -XXX refers to the last three numbers, not the first three.

 

 

Read somewhere that apart from anything else, the -229 is heavier than the other two version . . . . shrug.

 

Yes but some MSIP F-15A/Bs were fitted with the -220 and not all F-15Es have the -229. A few units still have -220 powered F-15Es and are usually based in the US for training. Some -220 F-15Es were refitted with the 229 later and in recent years. Currently around 80% of the USAF Stike Eagles are 229IPE powered.

[D-Scythe]

But my statement was very much true. The -100 was up-trimmed to around 29k thrust when used on the F-15D test airframe for the F-15E program. There were limited -220s at the time as they were going into F-16s and the early F-15C/D were being refitted with them so that why the -100s were used for that.

 

Um, I really don't think there was a Dash 100 tweaked to produce 29K lbs of thrust. I know that there are the Dash 220E and the Dash 220E+, derived from the 100 and 220 turbofans with -229 tech, but I don't think either of these engines were retrofitted to F-15s in the late 1980s when the F-15E program was underway. Reason for this is because the update incorporated IPE engine technology into the older engines, but the Dash 229 didn't exist back then.

[Kula66]

IIRC, it took about 30 seconds to reach 350 KCAS with full burners, then another 24 (?) seconds to reach 32,000' at Mach 0.95.

 

-SK

 

SK,

On this ... A 15 on the runway (low fuel load), Max power, brakes off lift off ASAP and go near vertical (say 70degs) ... the LO Eagle will fall out of the sky! In RL I've seen one do this ... and it just kept on going upwards - apparently accelerating.

[SwingKid]

SK,

On this ... A 15 on the runway (low fuel load), Max power, brakes off lift off ASAP and go near vertical (say 70degs) ... the LO Eagle will fall out of the sky! In RL I've seen one do this ... and it just kept on going upwards - apparently accelerating.

 

Ok, so which part of this is in error?

 

 

-SK

[Starlight]

Ok, so which part of this is in error?

 

 

-SK

 

 

Your chart states "US standard day 1968"

Kula lives in the UK, and he probably saw the F-15 many years after 1968, and we all know climate has changed dramatically in the last years ;)

that's my explanation.

 

Anyway, more seriously, I've seen some "Viking departures" at Aviano AB, and hell yes,they go straight up after t/o roll!

[SwingKid]

Anyway, more seriously, I've seen some "Viking departures" at Aviano AB, and hell yes,they go straight up after t/o roll!

 

I don't doubt your word, but a flight sim as accurate as Lock On needs more precise numerical data.

For example - how does Kula66 know the fuel load? The F-15C airshow routine and Viking takeoffs are reportedly done with full fuel.

How long was the aircraft going vertical, to what altitude, at what speed, and how do we know it was accelerating?

Note that the climb profiles shown above are for 350 KCAS. Whatever the precise details, vertical acceleration seems to be a very transient condition, that only happens near the ground imediately after take-off.

 

-SK

[S77th-GOYA]

Ok, so which part of this is in error?

 

Ok, so which part is relevant?

 

Explain in simple terms why any free object weighing 35,000 lbs (a clean F-15C w/50% fuel load) can't be accelerated straight up by 47,000+ lbs of thrust (2xF100-PW-100 afterburning turdofans).