F-14 low speed prowess vs Other Aircraft

[aaron886]

It might have been an issue of masking the control surfaces as Alpha increased and the tendency towards adverse yaw (nose moving away from centerline in the opposite direction of the roll - watch "Cougars" carrier approach from Top Gun for a visual). The nose might have countered the forces applied by the control surfaces.

 

The Tomcat actually is said to have shown "proverse" yaw in some cases. Were the Tomcat to roll using traditional asymmetric lift devices at low speeds, it would definitely exclusively exhibit adverse yaw. But, the Tom relied on spoilerons when in approach configuration, which have the opposite effect. That Top Gun clip was probably flown as cleanly as possible, but I bet if the pilot slapped the stick around in low speed with the wings unswept he'd get that proverse yaw. One more interesting thing for Leatherneck to struggle with!

[captain_dalan]

Pretty certain that the F-15 can't complete a min radius turn in 15 secs ;)

 

The nimblest of WW2 fighters, the A6M2 Zero took 16.5 sec to complete one.

Not necessarily so. It would depend at least partly on the radius it self. The minimum radius is usually not the "quickest" turn.

[turkeydriver]

The Tomcat actually is said to have shown "proverse" yaw in some cases. Were the Tomcat to roll using traditional asymmetric lift devices at low speeds, it would definitely exclusively exhibit adverse yaw. But, the Tom relied on spoilerons when in approach configuration, which have the opposite effect. That Top Gun clip was probably flown as cleanly as possible, but I bet if the pilot slapped the stick around in low speed with the wings unswept he'd get that proverse yaw. One more interesting thing for Leatherneck to struggle with!

 

Ooh yes, need the ability to do a high alpha low speed cross couple to swap ends. DCS engine models alpha beautifully.

[GGTharos]

Pretty certain it can, and quite easily. Just need the right technique.

 

You cannot have it both ways no matter how much you'd like it to be so. Either both the F-15 and F-14 can do it, or neither one of them can.

 

Insofar as as certain parameters can be compared, ie. consider 'similar' combat payloads for an F-14 and F-15, including fuel and missiles, the charts at 10000' give the F-14 a higher STR by maybe a tiny faction of a degree. That's an advantage, though it isn't significant (2 deg/s would be a pretty significant difference) - but again, there are some assumptions here which may alter the end results:

 

1. The 'standard days' are the same (they're not, but I didn't check to see if the difference would make an impact. It may or it may not)

2. The combat weights that I chose are comparable. They might not be.

3. That I'm reading the charts right. Maybe I'm not.

 

That's sustained turn rate. If you want to see a really super hot turn, then you need ITR, not STR - and you're not getting a 20 second min-radius turn out of either aircraft with STR as far as I can tell ... which means that both will get under 20 sec in a real max-performance turn.

 

Edit: Just checked the standard atmospheres for both charts. Assuming I'm reading the right, the one used for the F-15C charts is warmer than the one used for the F-14, which means the F-15's performance would have to be increased to make a better comparison - so probably that fraction of a degree advantage might just flat out vanish.

 

Pretty certain that the F-15 can't complete a min radius turn in 15 secs ;)

 

The nimblest of WW2 fighters, the A6M2 Zero took 16.5 sec to complete one.

Edited March 15, 2015 by GGTharos

[Exorcet]

The F-14 may have an advantage at lower speed, but if it does I don't think it will be huge. It doesn't really have any leaps and bounds advantages over the F-15. And it really is that heavy. Loaded F-15's have better TWR's than combat weight F-14's.

[aaron886]

Pretty rare to see a fighter pull off a sub 20-second turn at sea level, just sayin'. Theory and practice are different.

[lunaticfringe]

The F-14 may have an advantage at lower speed, but if it does I don't think it will be huge.

 

Below 15k and Mach .75, the Tomcat holds an average of 1G sustained on the F-15 in both the A and B/D configurations. That's anywhere from 15-30% more available G. That is what is generally referred to as "huge", although YMMV.

 

1. The 'standard days' are the same (they're not, but I didn't check to see if the difference would make an impact. It may or it may not)

 

ICAO and US Standard Days are in essence the same. The 1966 version of the US standard is the same as the 1962 and 1976 up to 32km. Data higher changed due to satellite data in the 66 issuance, and then got substantially better in 1976 based on even more.

 

Re: configuration:

 

The 53,873 F-14A, with a 40,104 dry weight, is essentially 2840lbs of ordnance (4x AIM-9M @ ~200lbs and 4x AIM-7M @ 510lbs ea), and just under 11000lbs of gas, or 67.9%.

 

Is the chart for the F-15 anywhere close to 40,575lbs (same ordnance, since she could hang it, and 9135lbs of gas, or 67.9%)? Generally speaking, I see data on the F-15A/C at around half gas for combat weight, putting it around 2400lbs less (38,175), sometimes as low as 35,000lbs.

Edited March 15, 2015 by lunaticfringe

[GGTharos]

Below 15k and Mach .75, the Tomcat holds an average of 1G sustained on the F-15 in both the A and B/D configurations. That's anywhere from 15-30% more available G. That is what is generally referred to as "huge", although YMMV.

 

Maybe I'm reading the charts wrong.

 

ICAO and US Standard Days are in essence the same. The 1966 version of the US standard is the same as the 1962 and 1976 up to 32km. Data higher changed due to satellite data in the 66 issuance, and then got substantially better in 1976 based on even more.

ICAO appears to be using weather that's 10 deg warmer, but again - I might be mis-reading or mis-understanding what's in the charts. They are long and complex and I've only taken a quick look.

 

Re: configuration:

 

The 53,873 F-14A, with a 40,104 dry weight, is essentially 2840lbs of ordnance (4x AIM-9M @ ~200lbs and 4x AIM-7M @ 510lbs ea), and just under 11000lbs of gas, or 67.9%.

 

Is the chart for the F-15 anywhere close to 40,575lbs (same ordnance, since she could hang it, and 9135lbs of gas, or 67.9%)?

41000lbs F-15C with 4x4 and CL. At 0.6M, it has an STR of about 12.4 deg.

 

~54000lbs for the F-14. STR at 0.6M is about 12 deg.

 

Both charts read at 10000' due to both having that specific altitude available.

 

At this altitude the F-14 specifically peaks at around 0.7M, with an STR ~ 12.3 or 12.4 at 5 + some fraction of G (the chart doesn't let you read it off easily), the F-15 at 0.7M holds 13.25 at 5.3g or so.

 

Interpolating the F-15 graph to 5000' still gives the F-15 a slight STR advantage. In other words, IMHO both aircraft are quite comparable in STR at that particular point.

 

Going to the M0.4 point, the F-15 continues to maintain an advantage. Going faster than M0.7, the F-14's STR drops, the F-15's increases.

 

Anyway, I had to re-read the charts a couple of times to make sure I was reading the numbers correctly, and it's late, so there's certainly room for errors. Where there is a huge difference though is in ITR. If the F-14 was used as a 9g machine, it appears that it might get to whip around like a flanker.

Edited March 15, 2015 by GGTharos

[lunaticfringe]

ICAO and US Standard Day are both 15C/288.15K, 1013.25 hPA, same lapse rate.

 

*shrug*

 

Toss me your F-15 charts, yo.

[GGTharos]

Relevant chart attached. :)

[lunaticfringe]

I give you whole manuals, and get a page in return. Some pal. :P ;)

 

Maybe I'm reading the charts wrong.

 

Possibly, or you may be reading the wrong chart: Maneuvering Devices Not Operating, rather than Maneuvering Devices on Auto.

 

41000lbs F-15C with 4x4 and CL. At 0.6M, it has an STR of about 12.4 deg.

 

~54000lbs for the F-14. STR at 0.6M is about 12 deg.

 

0.6M @ 10k in the F-14A is just a shade under 13.4 degrees.

 

At this altitude the F-14 specifically peaks at around 0.7M, with an STR ~ 12.3 or 12.4 at 5 + some fraction of G (the chart doesn't let you read it off easily), the F-15 at 0.7M holds 13.25 at 5.3g or so.

 

It's actually 13.5 for the Tomcat at .65M @ 5.0G, but now we're in sweating over hair territory. And speaking of reading charts easily- HEY AIR FORCE: HOW'S ABOUT SOME ACTUAL Ps CURVES, EH? COMBAT DOESN'T HAPPEN AT PURELY SUSTAINED RATES. :D

 

Interpolating the F-15 graph to 5000' still gives the F-15 a slight STR advantage. In other words, IMHO both aircraft are quite comparable in STR at that particular point.

 

This is where I'm really getting the impression you're looking at the wrong series. I'll disregard the rest (M0.4), but as far as the two modes (non-operational and operational):

 

0.6M: N/O: 14dps @ 5.0G

0.6M: Op: 14.5dps @ ~5.4G

 

F-15: 0.6M: 14.5dps @ 5.0G (interpolated)

 

The F-14A can grab another degree here by slowing down a tad and standing at 0.55M as shown on the chart. 1 degree? Sure. But we're arguing this all out for the sake of arguing, so :P

[GGTharos]

I give you whole manuals, and get a page in return. Some pal. :P ;)

 

We can arrange for that.

 

It's actually 13.5 for the Tomcat at .65M @ 5.0G, but now we're in sweating over hair territory. And speaking of reading charts easily- HEY AIR FORCE: HOW'S ABOUT SOME ACTUAL Ps CURVES, EH? COMBAT DOESN'T HAPPEN AT PURELY SUSTAINED RATES. :D

 

Yep, it'd be nice if they included those, since with things as they are, we can only guess at certain other measures :P

 

This is where I'm really getting the impression you're looking at the wrong series. I'll disregard the rest (M0.4), but as far as the two modes (non-operational and operational):

 

0.6M: N/O: 14dps @ 5.0G

0.6M: Op: 14.5dps @ ~5.4G

 

F-15: 0.6M: 14.5dps @ 5.0G (interpolated)

 

The F-14A can grab another degree here by slowing down a tad and standing at 0.55M as shown on the chart. 1 degree? Sure. But we're arguing this all out for the sake of arguing, so :P

 

It turns out I was flipping between the two charts, which was monumentally confusing.

 

1 degree is significant. A 2 deg advantage is pretty big. This is all about 'whose sandbox do you want to play in?'. The F-15 can keep up (equal turn rate) by keeping just a bit more speed (about +0.1M gives it equal turn rate, or at least it'll be difficult to see a difference in the charts).

 

So now the only way to determine what might be more agile is to do a very different set of work, which isn't possible because no V-N diagrams for F-15 ... or rather, they would have to be constructed in-game.

[Exorcet]

Below 15k and Mach .75, the Tomcat holds an average of 1G sustained on the F-15 in both the A and B/D configurations. That's anywhere from 15-30% more available G. That is what is generally referred to as "huge", although YMMV.

 

If that's what the official sources say for similarly configured aircraft, then case closed. It's the anecdotal stuff I'm less willing to believe (or more likely to think exaggerated), but if the facts back them up then I guess they can be true.

 

41000lbs F-15C with 4x4 and CL. At 0.6M, it has an STR of about 12.4 deg.

 

~54000lbs for the F-14. STR at 0.6M is about 12 deg.

 

41000 - (2840 + 28000) / 41000 = .2478 (10160 lbs)

 

54000 - (2840 + 40104) / 54000 = .2047 (11050 lbs)

 

That F-14 has a bit of a fuel fraction advantage. Equality would happen with the Eagle at 7950 lbs fuel. The F-14 numbers are still impressive though.

[GGTharos]

The 41000lbs chart is the closest one that can be used for comparison. The next one down has no weapons on-board, which means that drag is significantly reduced.

[Exorcet]

The 41000lbs chart is the closest one that can be used for comparison. The next one down has no weapons on-board, which means that drag is significantly reduced.

Understood, I was just curious to see how close they were. The F-15 number seemed a little high considering their empty weights. The F-14 empty weight was a little lower than what I usually use (43000 lbs) as well.

[captain_dalan]

Good points all around guys :thumbup:

What i miss the most in the F-15 charts is the CLmax charts, but i have never seen those on any AF diagram, not even on F-4s.

 

BTW, GGt? Are those charts for the F-15 with the GE engines? The PW ones seam to give it a bit less thrust. Here is what i managed to draw up at home using both. Note however, the PW F-15 should be raised a bit higher in the second chart, as the drag should be a bit lower.

 

F-14A 53800pds and F-15C 41000pds ENG1:

 

 

F-14A 53800pds and F-15C 41000pds ENG2

 

 

The colors are inverted on both pictures, but you get the idea. The GE powered engines on the Cat should made them even more similar i guess :)

[GGTharos]

I was thinking of doing the same using engauge - what software did you use? :)

 

The engines are F100-PW-220. They can be cranked up if need be, but there's no reason right now to simulate anything other than the -1 values ( ...because we don't have anything but those values, and even though the USAF says they can crank those up to 25000lbs/engine, we don't know under what circumstances that would be done, nor what the curves would look like).

 

We're not interested in the F100-PW-100 since it isn't the engine being modeled in the game.

Edited March 15, 2015 by GGTharos

[captain_dalan]

I actually used old fashioned Excel 2007 :)

 

I do do have the F-14A performance manual though, so i can extract the data from the specific excess power charts (pages 295-299). This and some NASA aerodynamic tables for low mach, give me enough data to fill in the blanks, and fine tune the curves. Drawing the thing over the existing charts is a bother, as right now i have no imaging software installed on my PC and use Paint from all things :(

 

 

The engines are F100-PW-220. They can be cranked up if need be, but there's no reason right now to simulate anything other than the -1 values ( ...because we don't have anything but those values, and even though the USAF says they can crank those up to 25000lbs/engine, we don't know under what circumstances that would be done, nor what the curves would look like).

 

We're not interested in the F100-PW-100 since it isn't the engine being modeled in the game.

 

Ahh, thanks! I didn't know that. I always thought we would have both engines in the sim.

[GGTharos]

I don't believe you'll be in danger of finding an F-15C with a -100 past a certain time period, if at all :)

[captain_dalan]

I don't believe you'll be in danger of finding an F-15C with a -100 past a certain time period, if at all :)

How did the upgrade program go? I mean time scale wise?

 

BTW, i am thinking of calculating the F-14B E-M chart at 10000ft, but it will take some time, so i might not be able doing it today.

[lunaticfringe]

Why calculate? PM.

[lunaticfringe]

The thing that kills me is that the only CL/Ps chart I've ever found on the F-15 is in that Gray Matter series (the RTU manual- I think I pawned it off on you a while back, GG) for 15k. Even at that altitude, the F-14 maintains the CL curve advantage through 0.65 of around 1/2 G, descending at 0.5M.

 

The frustration stems from exactly what I said- ACM isn't fought at sustained rates; it's the trades. If you're fighting in another guy's wheelhouse, you win by making the correct trades of Ps for position. You have to see those trades to learn them, and there's never enough DACT to go around. Get a proper chart, and you can not only see how far you can take it for rate, you can get a really good idea how much you'll pay, and how long you've got to unload (or how much altitude you've got to sacrifice) to get it back.

[GGTharos]

Yep, there's a lot of research on the subject, but only a few breadcrumbs available publicly ... :)

[Hummingbird]

Pretty rare to see a fighter pull off a sub 20-second turn at sea level, just sayin'. Theory and practice are different.

 

Yes, but apparently DCS is as good as reality :pilotfly:

[GGTharos]

So you're abandoning all hope of having a well modeled tomcat, right?

 

Yes, but apparently DCS is as good as reality :pilotfly: