How to hit Mach 2.4?

[Callsign JoNay]

1 hour ago, captain_dalan said:

Just checked and indeed, adding the missiles only adds the missile weight to the total aircraft weight. But what if the palettes are considered on at all times? If an empty F-14A is 40100lbs and the one we have without fuel and internal ammo is 42086, that's about 2000lbs extra, right? Did those pallets weigh about 500lbs each? If so, it would account for the extra weight. 

Check out the sticky topic about the performance FM development starting around page 20. I think the on speed tests we did ruled out the weight of the pallets being baked into the aircraft clean weight.

[mkellytx]

A lot folks, wrote a lot of stuff, one thing not yet mentioned about the difference between the two engines is the Overall Pressure Ratio (OPR).  The TF30 is a 20ish OPR engine while the F110 is a 30ish OPR engine.  Lower OPR engines do better at higher Mach numbers, J58 (SR-71) 6ish OPR, RR Olympus 593 (Concord) 10ish OPR.  The inlets do a lot of the compression at high Mach through multiple oblique shocks (ramps/spikes/half cones), good for pressure rise but also raises the temperature.  The higher OPR compressor will run into temperature limits faster, not so good for sustained high Mach numbers.  That said, the higher OPR engine is the more efficient engine subsonic.

So, in the case of the Tomcat, by the time they got F110 the high fast intercept was less of a concern in the late 80's and 90's.  Hence don't spend the money to schedule the ramps, the better subsonic efficiency and higher thrust subsonic/transonic is good enough for the expected threat.

Edit: corrected incorrect acronym 

Edited June 22, 2022 by mkellytx

[KL0083]

2 hours ago, mkellytx said:

So, in the case of the Tomcat, by the time they got F110 the high fast intercept was less of a concern in the late 80's and 90's.  Hence don't spend the money to schedule the ramps, the better subsonic efficiency and higher thrust subsonic/transonic is good enough for the expected threat.

But drag enough to jeopardize a notch already.

Since A+ shares identical engine with Viper alone with much high Mach design,the speed performance ought not be limited at this level.

[captain_dalan]

11 hours ago, Callsign JoNay said:

Check out the sticky topic about the performance FM development starting around page 20. I think the on speed tests we did ruled out the weight of the pallets being baked into the aircraft clean weight.

Although i did participate in that discussion, i had to revisit it, as the topic about approach speeds was good ways back. However, i didn't find anything that provided decisive info on the pallets. It seems the consensus was that adding external tanks removed effective weight. But the pallets could still be or not be always on. As we base all our tests on gross weight, they might as well be there. After all, we don't know the empty weight of the bird we are simulating in DCS 

[Istari6]

Just started learning the F-14A Tomcat in April.  About a month ago, for my own interest, I ran a series of tests to get a sense of maximum speeds with different loadouts.

Conditions: ISA (15C, 29.92 Hg)

LOADOUT	w/FT x 2 @ 5000 lbs	Clean @ 5000 lbs	Notes
AIM-54A Mk 47 x 6, AIM-9L x 2	Mach 1.65	Mach 1.80	SLOW accel past Mach 1.2
AIM-54A Mk 47 x 4, AIM-7F x 2, AIM-9L x 2	Mach 1.75	Mach 1.85	SLOW accel past Mach 1.3
AIM-7F x 4, AIM-9L x 4	Mach 2.00	Mach 2.20	Mach 2.1 @ 7100 lbs rem*
AIM-54 pylons only	Mach 2.10*	Mach 2.25	*Unpleasant oscillations w/FT

Best result was a clean Tomcat with just the AIM-54 pylons, topping out at Mach 2.25.  All speeds are indicated in the cockpit gauge, actual speed might be slightly or lower.

Hope this helps others.  

[Quid]

23 hours ago, G.J.S said:

There’s something that is bugging me about this report . . . .

Being that it is secondhand (at best) from an after action report over 40 years ago is the first thing.

Theres just little bits here and there . . . For instance.

Im in no way doubting the F-14 in its early iteration was a fast bird, but why go hot on two inbound -25’s at M2.4, only to close to visual and formate? The fuel wasted just to ‘join up’ is eye-watering.
I know about escort away from area of operation, but jeez, why make yourself look eminently hostile by blowing towards foreign fighters at Mach mucho? Muzic’s flight wasn’t the only airborne CAP, plus there were F-4’s a bit closer that could have intercepted and at the very least “tied up” the -25’s whilst the F-14’s placed themselves. 
 

Also, and this was something very prevalent during the Cold War, could the 2.4 be a little bit of disinformation? Make the ‘opposition’ expend time and money trying to develop something that can deal with a 2.4 cat, which at the time would be prohibitively expensive for any country, and hopefully break that country financially? The F-14 can certainly get close, but the difference between 2.3 & 2.4 can be millions of dollars and many months of trial and error for an opponent - maybe too much.
It’s the same with drunks at a bar - they always try to appear more pumped and skilled than they really are - intimidation. If the other guy is bigger, harder, faster than you, you are less likely to want to tango.

This incident certainly did happen, as did many more like it, but there’s just a few things . . . . 

 

While this quote was made more than 40 years later, this is far from the first time it was used.  The F-14A's top speed was quoted in the open-source world by James Perry Stevenson in 1975, albeit with an apparent typo listing its top speed as 2.5M instead of 2.4M[1].  It was amplified in Jon Lake's 1998 "Grumman F-14 Tomcat: Shipborne Superfightter": "Later the Tomcat exceeded its Mach 2.4 limit, the pilot chopping the throttles to decelerate when he reached a reported Mach 2.41, still accelerating." [2]  Former TOPGUN CO "Wigs" Ludwig actually claimed an even higher 2.5M, but he was speaking anecdotally[3].

These things having been said, it wouldn't surprise me if it were part of a disinformation campaign to say a loaded Tomcat could hit 2.4M (or 2.5M) to make the Soviets spend money to counter it.  Practically, the plane is slower, and it wouldn't surprise me if to hit 2.41 the plane had to have its engines and ramps tweaked in a way different from operational F-14s.

References:

1. James Perry Stevenson, Grumman F-14 "Tomcat", TAB Aero Publishing, London, 1975, 24.

2. Jon Lake (ed.), Grumman F-14 Tomcat Shipborne Superfighter, Aerospace Publishing, London, 1998, 36.

3. Grumman F-14 Tomcat Bye Bye Baby!, Zenith Press, MN, 2006, 175.

[mkellytx]

20 hours ago, KL0083 said:

Since A+ shares identical engine with Viper alone with much high Mach design,the speed performance ought not be limited at this level.

The fallacy here is that the same engine in another airframe should produce the same results.  The difference is that the vast majority of GE powered Vipers have a different inlet than the Pratt powered Vipers specifically designed for the 110. 

The 110 dropped into the Tomcat pretty easily since they were almost the same size as the TF30's and were about the same mass flow rate.  So, everywhere except the upper right hand side of the envelope performance increased.  That said, the effort to get that performance wasn't worth the cost.  No doubt it could have been done, but budgets were shrinking in real terms, those were real cuts, not "Washington" cuts.  At what cost would that performance come?  No Super Bug, no LANTIRN?  The potential existed to get the performance, the money and mission requirements just weren't there after the hordes of Backfires disappeared.

The fact that the F-15 rescheduled their inlets for 110's shows that it could be done, unlike the Navy, there were some wealthy Gulf States willing to foot that bill...  The tricky bit is once the Mach number starts getting higher than 1.5 matching the compression of the inlet to the compression of the compressor becomes really important and isn't easily intuitive unless you spend some time with supersonic aerodynamics, thermodynamics and some rotating machinery.  It's hard stuff, been 20 years since I've done it, found I liked the performance and handling qualities stuff much better and flight test is much more fun to boot. 

[Callsign JoNay]

On 6/19/2022 at 8:35 AM, captain_dalan said:

Although i did participate in that discussion, i had to revisit it, as the topic about approach speeds was good ways back. However, i didn't find anything that provided decisive info on the pallets. It seems the consensus was that adding external tanks removed effective weight. But the pallets could still be or not be always on. As we base all our tests on gross weight, they might as well be there. After all, we don't know the empty weight of the bird we are simulating in DCS 

I had to go back to refresh myself on it again. Yeah I suppose you are right. We still don't know the actual clean weight of our aircraft aside from what the ME tells us. It's really unfortunate. The weight of the pallets and fairings is equal to a GBU-10, that's not nothing. My fear is that HB built a flight model based on a clean jet that performs like a heavy one, or visa versa, a heavy jet that performs like a clean one.

[captain_dalan]

1 hour ago, Callsign JoNay said:

I had to go back to refresh myself on it again. Yeah I suppose you are right. We still don't know the actual clean weight of our aircraft aside from what the ME tells us. It's really unfortunate. The weight of the pallets and fairings is equal to a GBU-10, that's not nothing. My fear is that HB built a flight model based on a clean jet that performs like a heavy one, or visa versa, a heavy jet that performs like a clean one.

I just assume my bird is in fleet defense configuration pallets are always on

[Panny]

2 hours ago, captain_dalan said:

I just assume my bird is in fleet defense configuration pallets are always on

Makes sense to me that the weight of the pallets are permanently on

[draconus]

On 6/17/2022 at 6:04 PM, LanceCriminal86 said:

All ties into what Victory205 and others reiterated during the great FM chart wars, is that every jet was different in some way. While they would fly about the same some airframes, engines, etc. performed slightly different. I'd love to see some of that modeled, have % baked in to available thrust, turn rates, fuel economy, likelihood of system failures.

Well, HB already did implemented that random difference, which can be felt in yaw sometimes. You'd have to ask @IronMike how much lucky or unlucky you can get by this.

 

On 6/19/2022 at 2:16 AM, G.J.S said:

Also, and this was something very prevalent during the Cold War, could the 2.4 be a little bit of disinformation? Make the ‘opposition’ expend time and money trying to develop something that can deal with a 2.4 cat, which at the time would be prohibitively expensive for any country, and hopefully break that country financially? The F-14 can certainly get close, but the difference between 2.3 & 2.4 can be millions of dollars and many months of trial and error for an opponent - maybe too much.

While some disinformation might have been used there it takes much more than that to break a country. Only a few percent of GDP is usually spent on military. It's not like they were trying to build Dyson sphere. It's just a manned rocket (or a jet powered brick if you will) which happened to get easily up to M2.8, much more than mere 2.3 vs 2.4 difference.

 

@mkellytx as for "Operating Pressure Ratio (OPR)" isn't it "Overall pressure ratio"?

https://en.wikipedia.org/wiki/Overall_pressure_ratio#Examples with J58 being 8.8?

 

btw: total weight for Phoenix fairing+rail+launcher is 472lbs (station #3), 497 (6) and 444 (4/5) with DI of 10. This is for F-14A/B.

Edited June 21, 2022 by draconus

[WarthogOsl]

On 6/19/2022 at 5:23 PM, Quid said:

While this quote was made more than 40 years later, this is far from the first time it was used.  The F-14A's top speed was quoted in the open-source world by James Perry Stevenson in 1975, albeit with an apparent typo listing its top speed as 2.5M instead of 2.4M[1].  It was amplified in Jon Lake's 1998 "Grumman F-14 Tomcat: Shipborne Superfightter": "Later the Tomcat exceeded its Mach 2.4 limit, the pilot chopping the throttles to decelerate when he reached a reported Mach 2.41, still accelerating." [2]  Former TOPGUN CO "Wigs" Ludwig actually claimed an even higher 2.5M, but he was speaking anecdotally[3].

These things having been said, it wouldn't surprise me if it were part of a disinformation campaign to say a loaded Tomcat could hit 2.4M (or 2.5M) to make the Soviets spend money to counter it.  Practically, the plane is slower, and it wouldn't surprise me if to hit 2.41 the plane had to have its engines and ramps tweaked in a way different from operational F-14s.

References:

1. James Perry Stevenson, Grumman F-14 "Tomcat", TAB Aero Publishing, London, 1975, 24.

2. Jon Lake (ed.), Grumman F-14 Tomcat Shipborne Superfighter, Aerospace Publishing, London, 1998, 36.

3. Grumman F-14 Tomcat Bye Bye Baby!, Zenith Press, MN, 2006, 175.

FWIW, the version of the James Perry Stevenson book I have (it was my first F-14 book) also says "the F-14 has been as fast as Mach 2.6" on page 68.  I always assumed it meant in a dive.

[Katj]

FWIW, the version of the James Perry Stevenson book I have (it was my first F-14 book) also says "the F-14 has been as fast as Mach 2.6" on page 68.  I always assumed it meant in a dive.

Also, perhaps it wasn't a standard day, but way colder.

[mkellytx]

14 hours ago, draconus said:

@mkellytx as for "Operating Pressure Ratio (OPR)" isn't it "Overall pressure ratio"?

https://en.wikipedia.org/wiki/Overall_pressure_ratio#Examples with J58 being 8.8?

Indeed it is Overall, jumbled the O definition happens as we get older and don't take off the distance glasses to read the small print lol.  Of course on the jets I flew we always went by EPR.

Personally wiki isn't the first source I'd reference although my old Jet Propulsion text book was wrong, but did at least have a table comparing lots of engines on one page.  The SR-71A-1 page 1-4 gives "8.8:1 pressure ratio compressor".  Turns out Mattingly used an old reference from the 80's.  That said, 6, 8.8 is quibbling they're both low.

[henshao]

On 6/21/2022 at 7:13 PM, mkellytx said:

Indeed it is Overall, jumbled the O definition happens as we get older and don't take off the distance glasses to read the small print lol.  Of course on the jets I flew we always went by EPR.

Personally wiki isn't the first source I'd reference although my old Jet Propulsion text book was wrong, but did at least have a table comparing lots of engines on one page.  The SR-71A-1 page 1-4 gives "8.8:1 pressure ratio compressor".  Turns out Mattingly used an old reference from the 80's.  That said, 6, 8.8 is quibbling they're both low.

You think that's low, go check out the Tumanskys on the Foxbat...compressor section on those jets was almost cosmetic

[draconus]

3 hours ago, henshao said:

You think that's low, go check out the Tumanskys on the Foxbat...compressor section on those jets was almost cosmetic

4.75:1 is low but still far from "cosmetic".

[IronMike]

If I read an article that says "ThIS ToMCaT wEnT mACh 2.5!" and then in the article it says, "but we cut off exactly at 2.34, cause we got bingo, and it would have suuuurely gone mach fiftihundretthousandninetyninepointseven (aka mach 2.5 and beyoooond)," I chuck it in the bin. BS like this is why so many folks have completely wrong ideas and fights over "but my favorite jet can do mach sixty, mate!" ... If the article already does not hold up to the title -> garbage clickbait. Misleading garbage for the non-flyer, non-enthusiast or ... over-enthusiast. Just utter trash.

The author of the article just wants you to read his fine piece of journalism, not to do proper research and portray factual history. I mean that would be work, and who wants to work, if you can just sell someone else's half assed articles as your own. Heck, he doesn't even put in enough effort to write the article himself, lol. Retelling a second hand story third hand even is already indicative enough for that - I mean, the peak of journalism right there... It starts - and ends - by almost exclusively quoting another such writer - aka being too lazy to even write his one exaggerations. Let us just third hand quote the second hand superlatives of another author, because we are too lazy to make up our own! Just to then quote him 4th hand, cause you need a guy from Grumman to tell the National Naval Aviation Museum to tell you that the F-14 was Grumman's answer for fleet defense! I mean, thank god he checked with the museum if that detail is correct, cause here I was thinking it was the G-21. The fact that no quote has a single reference, link or footnote we won't even mention. But no, that is not enough, we need a 5th second third fourth hand account from a RIO who posted on Quora, the historic source of all sources. Totally verified, totally well researched by Ethen Kim Lieser, the amazing, the incredible, the unbelievable, the world-class science and tech writer from Google... And the worst part about articles (and "authors") like that is that if the story was to be true, you could not do it a bigger disservice.

(In reference to the article posted on June 16th.)


 

Edited July 17, 2022 by IronMike

[draconus]

You OK, Mike?

[IronMike]

4 hours ago, draconus said:

You OK, Mike?

I am, I just utterly dislike such "journalism". The interent is full of it, and by that I do not mean to blame anyone who believes that, it is easy enough. Some quotes here, all of course without source, some bloating and exaggerating there, and you get a recipe to misinform ppl, rather than to inform them. This kind of "writing", if you even can call it that, imo is at the core of a lot of nonsense that is being spread around in this day and age. And while some of it may be true, it usually isn't, and again does just a disservice to the factual portrayal of a topic, history, etc. This is particularly true for many of these so called tech or defense writers who just keep re-quoting each other with unsubstantiated claims.

What the author should have done was to take the Quora quote and research its factuality, find the RIO, talk with him, substantiate it, verify it, compare with other instances, etc. - present sources that can be backed up, etc etc... It just goes to show how much of that is out there, particularly in the military topics, just take about every 2nd article about the F-35 etc. Anyway, I did go off topic, but I hope you can see why.

Edited July 17, 2022 by IronMike

[Leviathan667]

On 6/19/2022 at 4:04 PM, Istari6 said:

Just started learning the F-14A Tomcat in April.  About a month ago, for my own interest, I ran a series of tests to get a sense of maximum speeds with different loadouts.

Conditions: ISA (15C, 29.92 Hg)

LOADOUT	w/FT x 2 @ 5000 lbs	Clean @ 5000 lbs	Notes
AIM-54A Mk 47 x 6, AIM-9L x 2	Mach 1.65	Mach 1.80	SLOW accel past Mach 1.2
AIM-54A Mk 47 x 4, AIM-7F x 2, AIM-9L x 2	Mach 1.75	Mach 1.85	SLOW accel past Mach 1.3
AIM-7F x 4, AIM-9L x 4	Mach 2.00	Mach 2.20	Mach 2.1 @ 7100 lbs rem*
AIM-54 pylons only	Mach 2.10*	Mach 2.25	*Unpleasant oscillations w/FT

Best result was a clean Tomcat with just the AIM-54 pylons, topping out at Mach 2.25.  All speeds are indicated in the cockpit gauge, actual speed might be slightly or lower.

Hope this helps others.  

Thanks for the table. It is helpful. Yesterday, I flew at mach 2.30-2.33 with a clean F-14A (AIM-9 and -54  pylons on). See tacview file at 15:17+.

Mach 2.33 could not be sustained and was attained for a fraction of a sec at 17:47 (the plane was not level with a vertical speed of abt -500 ft/min) and again at 17:50 (the plane was in a very slight climb at +65 ft/sec vertical speed - see image). Also, wind was 2 m/s blowing to 99° while plane's AZ was 94° so that may have marginally helped.

Other factors: 

• Temperature ASL 16°C
• QNH 29.92

Mission file below for whoever wants to try it (it's a custom AAR mission).

nullnull

F14A AAR Il-78.miz Tacview-20220716-220823-DCS-F14A AAR Il-78.zip.acmi

[henshao]

11 hours ago, draconus said:

4.75:1 is low but still far from "cosmetic".

unfailingly pedantic as always, draconus