F-15E vs. F-18C

[henshao]

consider why they put swing wings on a jet in the first place before you wonder too hard about which has less drag

[Tenkom]

21 hours ago, Ramstein said:

I have not read every post in this weird comparison between the two aircraft. Totally different aircraft. F-18 was replacement for the F-14. The F-15, while on the heels of the F-4 Phantom, was meant to replace several aircraft, but mainly as A-A Interceptor, replacement for the F-111 (F-111 was very, very long distances), but the F-15 could not carry some of the larger weapons and much shorter leggs than F-111 (but weapons have evolved with so many long range missiles on so many platforms). But very capable of chasing down and delivering knockouts to other aircraft for long distances. Then they decided to give it some air to ground capabilities. The F-18 is multirole Navy fighter bomber. Totally different. Not even close. IMHO.

The F18 was not a replacement for the F14. It was meant to replace the A-7 and complement the F14. Eventually the F14 was canned and they developed the super hornet to replace both the hornet and the F14.

Also it seems you are talking about the F15C.

This discussion is about the F15E which is a multirole aircraft with emphasis on A-G. As such it makes sense to compare it to the F18.

[mkellytx]

16 hours ago, JB3DG said:

Yeah I've seen the effects of intake geometry on the T-38A vs the PMP T-38C (dropped max mach from 1.6 to 1.15). The F-15 does have variable inlets and exhausts though, I believe more advanced and capable than the F-111. That said, I would want to see total form drag as well as wave drag numbers. Greater mass means lower acceleration even when in level flight (simple a = F/m) and if the pig has a larger frontal area than the F-15E the total drag is still going to be worse. Combined with lower acceleration means you would have to spend more time in burner to simply get to the same speed which makes it less practical.

The F-15 variable ramps may well be more advanced, but it’s debatable if this translates into a more efficient propulsion system than the Vark’s inlets for level flight since the Eagle’s advances may well be to handle higher AOA turning (FWIW in engineering school I did have to work an F-15 inlet problem for a propulsion class).  That said, both are 1960’s designs with a different requirement set.

Trans/supersonic the compressible flow drags start to dominate, which area rule becomes a big thing (Mud Hens with CFT’s aren’t good here).  FWIW the Zero-lift drag coefficient area for the F-111F is 9.36 sq ft (Zero-lift drag coefficient is 0.0186, as a comparison the values for the F-105 were 6.65 sq ft/0.0173 respectively), I couldn’t find the same value for the Eagle (light gray or Mud Hen) so I’d be interested to see what that value is before definitively stating one is greater than the other, but both Eagles are big airplanes.

After 7 years of engineering school (BS, MS) I did become acquainted with that old, deceased, Englishman’s three laws.  When I took the equations of motion course from USAF TPS we started with the sum of the forces as well as conservation of angular momentum to derive the 6 DOF EOM’s.  The mass the forces act on matter, but compressible forces start to take over for trans/supersonic accelerations.  Again no statement here one way or the other since I don’t have my F-111 data (derived from flight test data which as a former flight test engineer I tend to prefer)

Now for some reason I do have the gray Eagle and Mud Hen manuals on my OneDrive (why didn’t I put the -1-1 for the Vark on it also).  So here’s a comparison of 0.5M to 1.2M at 10,000 ft since those are the charts I have available.

          F-15C, clean, F100-100, 38,000 lb GW          37 seconds   (102% trim on the engines)

          F-15E, clean, F100-220, 42,800 lb GW          41 seconds

          F-15E, -4 CFT, 4 AIM-9, 4 AIM-7, F100-220, 58,100 lb GW can’t accelerate to 1.2M at 10,000 ft, it tops out at 1.1M

          F-15E, clean, F100-229, 43,600 lb GW.          26 seconds

          F-15E, -5 CFT, F100-229, 55,600 lb GW        40 seconds

          F-15E, -5 CFT, 4 AIM-9, 4 AIM-7, F100-229, 59,800 lb GW         52 seconds

So, two observations the compressible drag of the CFT’s is rather significant and the -229 motors are a big improvement over the -100/220.

Now, while I couldn’t find the performance charts for a Vark (without spending $56 on a document I already own), I did find the requirements for the nuclear delivery profile for the Vark which was to approach at sea level at 0.5M, with a can of instant sunshine in the bomb bay, otherwise clean, accelerate to 1.2M in 18 seconds, and fly 400 nm at 1.2M (200 in, 200 out).  Now I’m pretty sure the Vark never met that, but hopefully it’s understandable why I want to look at a Vark level accel chart before stating one way or another its relative performance to the Mud Hen.

[henshao]

eventually they did decide to give the F-15 some A/G capability, roughly 1971-1972

 

[Ramstein]

I worked with them in the USAF. not many Naval aircraft, but a few came into our bases. I worked in SAC, TAC, with MAC. I spent a few years in NATO. I left in the 1980's.

 

[mkellytx]

Alright, turns out my handy 1F-111(B)A-1-1 is accessible so I ran the numbers.  The Vark in question is either the FB-111A or F-111G with -P7 engines that put out 20,000 lbs of thrust, the T.O. uses the old 1975 flight test data.  So, not quite an F model with -P100’s, 25,000 lbs of thrust and off course the FB weighs more with longer wings.  Also, the level acceleration charts recommend an “optimal” profile, which translates into the charts start at 25 degrees sweep/mil power, advance to min AB intermediate sweeps then finally go full AB 72 degrees sweep.  Since those charts are set up that way, the drag race changes to 0.9M to 1.2M so there’s an apples to apples comparison (both at full AB the whole time).  The weights chosen for the Vark are 60,000 lbs and 70,000 lbs which roughly gives 10,000 lbs of gas and 20,000 lbs of gas respectively (49,000 lbs empty weight and 1,000 lbs of instant sunshine in the bay).  All altitudes are at 10,000 ft with a standard day.

     FB-111A @ 60,000 lbs, clean                                              Time - 24 sec          Fuel Used - 1,030 lbs          Dist - 6.5 nm

     FB-111A @ 70,000 lbs, clean                                              Time - 30 sec          Fuel Used - 1,200 lbs          Dist - 6.5 nm

     F-15C @ 38,000 lbs, clean, -100 (102% trim)                    Time - 24 sec

     F-15E @ 42,800 lbs, clean, -220                                        Time - 24 sec

     F-15E @ 43,000 lbs, clean, -229                                        Time - 10 sec

     F-15E @ 55,600 lbs, -5 CFT, -229                                      Time - 22 sec

     F-15E @ 59,600 lbs, -5 CFT, 8 AAM, -229                         Time - 30 sec

     F-15E @ 60,700 lbs, -5 CFT, 8 AAM, LANTIRN, -229.       Time - 65 sec (It pretty much maxes out at 1.2M in this config)

Conclusion, even the SAC Vark will out accelerate a -220 Mud Hen with CFT’s, it’s not that much slower than the -229 Mud Hen (-5 CFT’s) with 2/3rds of the thrust.  It’s pretty likely the F model Vark with the -P100 motors will out accelerate the -229 Mud Hen with CFT’s.  The CFT’s really mess with the compressible flow, the only way a heavier airframe with less thrust does that is with lower compressible flow drag components.

Enough with the off topic, gut feel here is that any Bug will have trouble with this drag race down low .

Edited May 16, 2023 by mkellytx

[GGTharos]

The strike numbers cannot be correct.  F=ma for acceleration here, you can even ignore the drag since we're more or less comparing apples to apples in terms of airframe, so the mach hump will look similar etc ... there is no way the -220 powered strike will have the same acceleration as the 38000lbs light grey, and the difference in mass is significant - about 10% or a little more.  You'd expect the strike to accelerate correspondingly slower, so about 26-27 seconds.   Similarly, the -229 doesn't provide over twice the thrust of the -220 either.  I'd expect to see the acceleration shaved off to maybe 20 seconds here.

Edited May 16, 2023 by GGTharos

[henshao]

29 minutes ago, GGTharos said:

The strike numbers cannot be correct.  F=ma for acceleration here, you can even ignore the drag since we're more or less comparing apples to apples in terms of airframe, so the mach hump will look similar etc ... there is no way the -220 powered strike will have the same acceleration as the 38000lbs light grey, and the difference in mass is significant - about 10% or a little more.  You'd expect the strike to accelerate correspondingly slower, so about 26-27 seconds.   Similarly, the -229 doesn't provide over twice the thrust of the -220 either.  I'd expect to see the acceleration shaved off to maybe 20 seconds here.

 

the F-15C in question is using the original -100; -220 F-15C makes the run @40k lbs in 21.5 seconds. The clean F-15E @44k lbs with -229 is actually about 13 seconds on the chart (it's scaled out slightly different for some reason)

Edited May 16, 2023 by henshao

[mkellytx]

46 minutes ago, GGTharos said:

The strike numbers cannot be correct.  F=ma for acceleration here, you can even ignore the drag ... there is no way the -220 powered strike will have the same acceleration as the 38000lbs light grey, and the difference in mass is significant - about 10% or a little more.  You'd expect the strike to accelerate correspondingly slower, so about 26-27 seconds.   Similarly, the -229 doesn't provide over twice the thrust of the -220 either.

 

The strike numbers are from the T.O.  The drag at trans/supersonic definitely are the dominating terms.  The difference between -100 and -220 are hydro mechanical controls vs digital so I completely believe that digital out performs hydro mechanical every day of the week and twice on Sundays.  The -229 is a completely different, digital engine with a completely different thrust profile (and core, and fan) so I can buy that as well.  IIRC the -229 charts are derived from flight test data so take it up with the test pilots/FTE’s….

The governing equations here are not linear, not even linear differential equations, so flight test data is king.  This is the biggest reason I differ to the data since nonlinear differential equations behave differently from what we learn in high school algebra.  This is complex stuff and an accurate gut feel comes from actually doing things up and away over years….

Edited May 16, 2023 by mkellytx

[Tenkom]

On 5/16/2023 at 4:17 AM, GGTharos said:

The strike numbers cannot be correct.  F=ma for acceleration here, you can even ignore the drag since we're more or less comparing apples to apples in terms of airframe, so the mach hump will look similar etc ... there is no way the -220 powered strike will have the same acceleration as the 38000lbs light grey, and the difference in mass is significant - about 10% or a little more.  You'd expect the strike to accelerate correspondingly slower, so about 26-27 seconds.   Similarly, the -229 doesn't provide over twice the thrust of the -220 either.  I'd expect to see the acceleration shaved off to maybe 20 seconds here.

 

In the F=ma equation F=Thrust - Drag.

If, at the given speeds, thrust is very close to drag, then acceleration can definitely double from a modest thrust increase.

Say if thrust=200kN and Drag = 180kN. If you increase thrust to 220kN you will double the acceleration if the mass stays the same.

[GGTharos]

Are you suggesting that the strike is less draggy than the light grey?

Are you also suggesting that drag force is linear across a bunch of speeds?

Edited May 18, 2023 by GGTharos

[henshao]

that -229 engine on a slick F-15 is a sight to behold, the -229 is allowed to run a good 100C hotter than the -220 among other improvements. VMax switch for the -220 would allow a 22C increase in FTIT for reference. Just a shame the common engine bay and other internal changes make the F-15E so much heavier, allegedly the -229 was designed to fit anywhere a -220 would and "should" fit in a "light grey" without problems. With that being said the proof of the pudding is in the eating, the apples to apples acceleration run in question for the clean F-15C is 21.5 seconds and only 13 seconds for the slick F-15E

[mkellytx]

I think what @GGTharos takes issue with, and he can correct me if I’m mistaken, is how the heavier -220 equipped Mud Hen can have the same acceleration as a light gray -100 equipped Eagle.  Now a big part of the problem is the most commonly quoted thrust numbers are static thrust, which by that metric a -100 produces slightly more thrust than the -220.  The problem is that acceleration isn’t a static equilibrium situation, it’s dynamic and transient.  The modifications to the -220, especially the DEEC produce more dynamic thrust so the thrust curve as a function of Mach number is greater, which is why the -220/220E equipped light gray’s accelerate faster than the -100 equipped birds.  As mentioned above the -229’s are absolute beasts.  The ability to run hotter, DEEC’s and lower bypass ratio create way more dynamic thrust which shows in the level accelerations.  Lower bypass ratio engines tend to perform better in the trans/supersonic flight regimes as well.

[SinusoidDelta]

if they were looking at the level flight acceleration chart I think they were, the discrepancy is because its a clean F-15E (i.e., sans CFT’s). If you have a -1 just compare against any accel. chart where CFT’s are specified at you’ll see a quite large increase in time to M1.2 

[GGTharos]

I doubt that a  clean F-15E with -220s is going to accelerate as fast as a clean F-15C.  It's trying trying to move 10% more mass with the same thrust, and drag isn't a differentiator here.

I just looked up my charts, both are at 10000' and for the -220 engine and clean, 'standard day', looking at the 0.8 to 1.2 mach accceleration:

F-15C, 40000 lbs: 25 seconds

F-15E, 42800 lbs: 29 seconds

F-15E, 43600 lbs: 16 seconds  - this is the 229 equipped one, all other conditions same as above (you could probably shave off a second if you shave off 1000lbs.  The reason this one is heavier is likely because the 229s are heavier)

Now, you could accuse me of not reading the charts very precicely and that's fine - I did my best.  No matter how you read it, the F-15E will accelerate slower which is expected.  The -229 will help accelerate faster - also, the -229 chart was a real pain to read, so if someone has the right charts they can verify my math.

EDIT:  Yeah I thought I didn't read those charts quite right, I read the -229 incorrectly because again, that chart sucks.

Edited May 19, 2023 by GGTharos

[henshao]

Now who's got the charts for the insect

[mkellytx]

On 5/19/2023 at 9:33 PM, henshao said:

Now who's got the charts for the insect

Those I have as well.

Spoiler

Neither insect can achieve 1.2 M at 10,000 ft.

Edit:

Some kind soul provided me the Specific Excess Power (Ps) charts for the -402 equipped C which can actually do 1.3 M at 10,000 ft with 2 heaters and 2 radars.

Edited May 21, 2023 by mkellytx

[mkellytx]

@GGTharos This is not intended as a quibble, but I am genuinely interested to know what the revision date, data date, data basis is for the -1’s of the charts you used.  I don’t have light gray charts for -220/220E only for the old -100 light grays.  Anyhow, I think we’re in violent agreement here because a F-15E with the same -220 engines is 4 sec slower than the light gray and 3.5 sec faster than the -100 equipped light gray at 102% trim.

Statement of due diligence:  all charts posted were taken from manuals purchased from  reputable sites such as Aircraft Reports or eFlight Manuals and are still available for purchase and comply with forum rules.  That said, please check my math.

F-15A/C Clean, F100-100 @ 102% trim   41 - 8.5 = 32.5 sec  (Flight test)

F-15A/C Clean, F100-100 @ 95% trim     67 - 9.5 = 57.5 sec  (Flight test)

F-15A/C CFT, F100-100 @ 102% trim       78 - 22 = 56 sec     (Flight test)

F-15E Clean, F100-220                              43 - 14 = 29 sec     (Flight test)

F-15E Clean, F100-229                               29 - 13 = 16 sec     (?)

F-15E -5 CFT, F100-229                             43 - 21 = 22 sec     (Estimate)

It is pretty funny that the charts many people seem to believe more are the only ones that don’t say flight test on them (-229 charts).  The less than optimal engine trim for the light gray illustrates just how much thrust and compressible flow terms dominate in this flight regime, 7% off trim results in 25 sec slower acceleration.  

Here’s the gouge from the 1986 Performance Block of the USAF TPS manual

Note that both thrust and drag are functions of velocity which are in the numerator and will be at least a function of V^2.  Also, just in case anyone asks, this manual is public domain.

 

[GGTharos]

I have a '95 for the light grey I think, and the '93 for the strike.  I'll get you more info if needed.

[mkellytx]

8 hours ago, GGTharos said:

I have a '95 for the light grey I think, and the '93 for the strike.  I'll get you more info if needed.

Thanks, please PM me where I can find the 95 light gray.  Looks like you weren’t too bad after all as we got the same values from the ‘93 dash one.

[JetCat]

On 10/4/2022 at 12:47 PM, Beirut said:

I'm not the most learned aircraft guy, so please be gentle.

The Hornet is very slow. The F-15 flies Mach 2.7 Speed: 1,875 mph and has night vision, that´s the two main reasons I will buy it for the pure sake of speed in VR.

Tech is of course the next important aspect that makes an airplane interesting in the long run. Nothing beats watching YouTube tutorial videos for hours, writing down systems procedures checklists and cockpit details, having a perfect simulated airplane with endless system and technology (and of course the weapons are very interesting too to test) at hand.

But will the F-15 have more or less tech than the Hornet... hm I don´t know... it´s not released yet I cannot test if all sub-menus of the LCD screens in the cockpit are functional, if the board computer and the navigation systems TACANs waypoint programing autopilot fly-by-wire systems etc. are fully functional. Let´s hope so

 

 

[AhSoul]

3 hours ago, JetCat said:

 

But will the F-15 have more or less tech than the Hornet... hm I don´t know... it´s not released yet I cannot test if all sub-menus of the LCD screens in the cockpit are functional, if the board computer and the navigation systems TACANs waypoint programing autopilot fly-by-wire systems etc. are fully functional. Let´s hope so

 

 

Not at EA release - the Hornet has been around much longer and had many updates. Over time, I'd expect the answer to be that they end up similarly complete and complex.

[falcon_120]

The Hornet is very slow. The F-15 flies Mach 2.7 Speed: 1,875 mph and has night vision, that´s the two main reasons I will buy it for the pure sake of speed in VR.
Tech is of course the next important aspect that makes an airplane interesting in the long run. Nothing beats watching YouTube tutorial videos for hours, writing down systems procedures checklists and cockpit details, having a perfect simulated airplane with endless system and technology (and of course the weapons are very interesting too to test) at hand.
But will the F-15 have more or less tech than the Hornet... hm I don´t know... it´s not released yet I cannot test if all sub-menus of the LCD screens in the cockpit are functional, if the board computer and the navigation systems TACANs waypoint programing autopilot fly-by-wire systems etc. are fully functional. Let´s hope so
 
 

guys you need to stop looking at Wikipedia figures, or you'll be a pretty anger customer later, asking why your F15E full of bombs is not doing M2.5 at 100ft .

Rarely you'll manage more than M1.5 in any minimum tealistic/tactical scenario.

The hornet IS slower than a F15E, but perfectly capable of M1.5 with an A2A only loadout. It'll get there later than a f15e in the same configuration for sure.

Enviado desde mi ELE-L29 mediante Tapatalk

[KrisJ]

Question: how close are F15E systems to F/A18c in terms of MFD, UFC, TPOD and generally navigation and weapon programming?

 

In other words, will it make sense to train on Hornet as a preparation for Streagle?

[KrisJ]

1 hour ago, KrisJ said:

Question: how close are F15E systems to F/A18c in terms of MFD, UFC, TPOD and generally navigation and weapon programming?

 

In other words, will it make sense to train on Hornet as a preparation for Streagle?

Disregard. F15E is out!