britgliderpilot

. . . . . if that NASA source and public domain simulation program turns out to be EngineSim, I'm going to have a good little chuckle :D Yep. The static thrust value should be relatively close, though . . . . it's interesting to note that it's 5,000lb or so under the publicised value for the HFFMS as well :) It should be possible for a forum member to recalculate the thrust figures, to be honest. We know most of the pertinent data (number of stages, compression ratio, pressure recovery at intake, con-di nozzle at the back) and can estimate efficiencies and temperature limits fairly well for that era. I've got too much on my plate at the moment to deal with it - but someone really dedicated to the cause and with sufficient technical knowledge (failing that, technical ability and a decent textbook) could plough through it in Excel. Then compare to Lomac and the HFFMS numbers. Someone with a background in engineering floating around with some spare time to crunch the numbers? edit - do I understand from reading through that the current engine lookups have been calculated from a peacetime-trim engine extimation rather than a chart available for a Vmax engine?

As regards the first question - just guesstimate the distance based on the current scale on the HUD or MFD. If you've got 128 scale up, and the target's 50km away, then hopefully just under halfway from your aircraft symbol to the top of the screen will be a bandit . . . . To the second question - IIRC AWACS only gives you heights in terms of High, Medium, and Low. Someone somewhere has the definitions of those heights, but they tend to be wide brackets and there's always some guessing in there. Welcome to the world of BVR ;)

There may not be a "need" for 20 thousand polys in a tank . . . . but considering the nature of the sim, we did need better ground unit 3D models :) Given the choice between making a model "good enough" or making it to the limit of your abilities and the abilities of current computers . . . I think most modellers would go the whole hog. I certainly wouldn't want to create a model and know I hadn't done my best. To re-state the obvious just for the record - third-party modellers obviously can't spend their time doing coding work. They are donating worthwhile features to the sim for our enjoyment, and deserve the credit for it. They're doing a fantastic job. And trust me . . . . first time you pop over a rise to see an unexpected group of enemy units right in front of you, and watch that beautifully crafted turret slowly swinging to bear . . . . . their work will REALLY be appreciated ;)

The same engine doesn't automatically mean you'll get the same performance from the engine. The intake system can make a BIG difference - especially comparing the fixed geometry intake on the F-16 to the variable geometry intake on the F-15. The intakes on Concorde and the Blackbird were absolute works of art - they were the single biggest thing allowing the performance of those two aircraft. There'll be differences in static thrust and at low Mach numbers due to differences in the ducting systems as well . . . . those aren't so big, but you can pretty much guarantee they'll be there. Just as an example - observe pressure recovery curve comparing the intake efficiencies:

If it was accurate for the F-16, it'll most likely be inaccurate for the F-15. Biggest difference is the intake system - big difference at high mach nos, less so at lower numbers. The zero forward speed/zero altitude case is still interesting, though. Below 20,000lbs thrust in the HFFMSMSfufflemumble F-16 as well as according to SwingKid's numbers . . . . . Where are the HFFMS numbers coming from, out of interest? I assume they're the ones from the Falcon flight model . . . . but what source did they use?

+1 and . . . . . You can almost guarantee there's a thread at Frugals that points at this one, in which F4 pilots will be busy slapping themselves on the back at how rubbish we are and how Godly they are. edit - insert some kind of comment concerning Black Shark having the combination of AFM and switchology which will be a shock to both sides here :D

Have done my own numbers and am satisfied. Those were in full AB on the deck, right? I can't see any way for the drag at those speeds to be taking 10,000lbs away from the accelerative force . . . . so no there no longer seems any doubt that the Lomac F-15 isn't producing the published thrust levels when it most probably should be. Mmmn.

Really? Mind if I take a quick look at your numbers, might serve to convince me even more :)

'Tis probably just a concept image. They've been throwing them around for a while. And just for the record - since the breakup of the USSR, they're not technically Soviet any more. Just plain "Russian" will do :)

Sure, it makes Cd much worse. However, at low speeds it really doesn't make a difference. Will throw some numbers around later on, but at a rough guess you could probably hit a hundred knots purely on F=ma. Certainly gear drag wouldn't hit 10,000lbs at speeds you'd reach on the runway . . .

Only at high speeds. For acceleration from a standing start on the runway, you can pretty much ignore it. Interesting numbers there SwingKid . . . .

. . . . there's football stadiums and hotels as well, but you're absolutely right. We demand beer!! . . . . or possibly Vodka . . . .

Ahhhhh . . . . Flanker 2, Flanker 2.5 and Flanker: Attack! I'm not old enough to remember Su27 Flanker . . . although I occasionally see a copy of the Commander's Edition in a local game shop for £5 and debate about buying it :P

There's a book about some of their exploits - Bloodsong, written by James Hooper with contributions by the guys from EO. Makes for . . . enlightening reading. From ground combat, to EO operating Angolan MiG-23s at night with iron bombs and NVGs . . . . it's good stuff! For more background on this sort of thing, I recently picked up a book . . . in Denver airport, actually . . . called Licensed To Kill, by Robert Young Pelton. Looks into the resurgence of the mercenary in recent years; one chapter goes into more of the internal workings and shady deals involving EO and ex-EO personnel. Another good read.

It was Executive Outcomes, and was disbanded some time ago after such activities were finally outlawed by the South African courts. . . . but then IIRC, they didn't own the helicopter at the time, they were just leasing it.

Of that list, the Typhoon. If it's made an absolute, the Raptor. . . . . . and what Pilotasso said :P

I'm intrigued. Where did all this come from?

EngineSim's model is for a turbojet rather than a turbofan, and while the efficiencies are greater than you'd expect, the material limits are rather lower than you'd expect. As such . . . . I don't know quite what they've done. I wouldn't class it as a workable estimation for any F100, to be honest.

Yep, mine said that as well. However . . . . if you look in a bit more detail, it says that that's the case for the -229 with F119 R&D going into it, while the original versions still had the 25:1 OPR. I'd be shocked if the F100 had a 35:1 OPR at entry into service in the 70's.

Yup - I had some sample efficiencies somewhere for a Uni design project that I used for the turbojet numbers, which as we've seen agrees a little bit better with the real number. Still not sure whether it's per stage or overall, though - it's not stated in the interface and I'm not sure how to get into the workings of the applet. There is - it's just that when going from zero forward speed to a "low" airspeed it's offset by the increased inlet drag. Running the same thing again with the turbojet with variable inlet, EngineSim says the initial drop in net thrust is much less than with the turbofan. Am a bit rusty on this, but I think I've got it right.

Righty - EngineSim's too limited for this estimation. It can't deal with afterburning turbofans, which is probably why they were using the turbojet approximation. As such . . . . you just can't get a decent answer out of it. It'd be possible to work it out theoretically with Excel, but you'd still be relying on guesses in certain places. The furthest I've got is by using the non-afterburning turbofan approximation with: 0.36:1 bypass 1.745 fan pressure ratio (guessed, it was a default ES figure) 10 stage compressor with pressure ratio of 14 (brings overall PR to 25) Fan diameter of 0.88m (from web reference stating inlet dia as 34.8 inches) Which throws out 16,000lbs dry thrust, about 1,500lb more than the stated dry thrust of the F-100. All of which tells us . . . . . actually very little :P Up the speed to 300mph and you lose 2,000lb of thrust, which at least should prove you can't climb vertically in an F-15 without burner. Which was never questioned. Bugger.

I fed it the default data that NASA supply as part of the F100 engine description. When I went back to check the numbers, it seems NASA are actually modelling the engine as a turgojet rather than a turbofan - it's not using any bypass ratio at all. The real thing has a small bypass ratio (0.36:1 according to Wiki), so it's not a BAD approximation, but there's an error right there :P Anyways - current NASA model. Compressor: 14 stages Pressure ratio 20.4:1 Efficiency 0.959 Burner: No pressure losses. Efficiency 0.984 Turbine: 4 stages Efficiency 0.982 It's eating 17748 kg of Jet A an hour, at 99.164 kg/s airflow. Will try and duplicate it in the Turbofan model and see what it says this time around - I think the software's limited to using movable inlets on turbojets, but since we're running at sea level and no forward speed it shouldn't matter.

Given that it's predicting 28,000lb thrust for the F100 at sea level, zero forward airspeed, I'd agree with that. PA, if you can tweak the EngineSim model so it'll give the advertised F100 thrust levels, and then repeat . . . . that'd be interesting. My guess would be they've not included duct losses or have overestimated efficiencies - but I'm just guessing.

I'm using a Logitch 3D Pro at Uni, both for some course-related stuff and Black Shark testing in the background. I've got an X45 at home, mostly because I've got the desk space to play with . . . . but lack of buttons aside, I've got no complaints about the Logitech stick so far. Shrug.

. . . . that it was RS-71 until LBJ got the name wrong at the official announcement? It's in Ben Rich's Skunk Works book somewhere, apart from anything else. Unless there's another story about that, of course :)