Penetrating Counter Air / Next Generation Air Dominance

[hornetfinn]

Which is why they developed excellent (for that era) SA for MiG-31 and later for Su-27 (advanced datalinks).

Su-27 had awful SA thanks to the terrible radar display.

I think that's also because they had rather poor signal processing system compared to Western fighters of the era. I'm sure that affected the display part also. Of course it was likely a good deal better than what they had before in MiG-21/23/25 or Su-15. But it might not look too hot to F-14/15/16 pilots at the time. And of course F-22 and F-35 pilots would find even F-14 and F-15 really lacking in SA department.

Anyway, improving SA has always been extremely important part of developing fighter aircraft. They got bubble canopies, radios and then radars and other sensors (like IRST and RWR/ESM). In new fighters those systems were much better than in the previous aricraft. There was also constant effort to deny enemy SA. Aircraft got low-vis paintings and ECM/EW systems. Now they are buing built to be VLO in radar frequencies and also difficult to be seen with all other sensors.

In the 5th gens the SA part is really the most important thing as it potentially can give the largest advantages against the enemy. Having 10% tighter turn capability is nice, but having 100 times better SA than enemy is priceless.

[madrat]

As if Brewstee Buffaloes could ever take on Yaks with better SA. Oh, wait.

[mixelflick]

Which is why they developed excellent (for that era) SA for MiG-31 and later for Su-27 (advanced datalinks).

Su-27 had awful SA thanks to the terrible radar display.

I think that's also because they had rather poor signal processing system compared to Western fighters of the era. I'm sure that affected the display part also. Of course it was likely a good deal better than what they had before in MiG-21/23/25 or Su-15. But it might not look too hot to F-14/15/16 pilots at the time. And of course F-22 and F-35 pilots would find even F-14 and F-15 really lacking in SA department.

Anyway, improving SA has always been extremely important part of developing fighter aircraft. They got bubble canopies, radios and then radars and other sensors (like IRST and RWR/ESM). In new fighters those systems were much better than in the previous aricraft. There was also constant effort to deny enemy SA. Aircraft got low-vis paintings and ECM/EW systems. Now they are buing built to be VLO in radar frequencies and also difficult to be seen with all other sensors.

In the 5th gens the SA part is really the most important thing as it potentially can give the largest advantages against the enemy. Having 10% tighter turn capability is nice, but having 100 times better SA than enemy is priceless.

This is why I think the F-14 really excelled. Though not a stealth bird, it was a quantum leap in sensor capability over Russian and even US fighters.

First, you had the AWG-9. Outrageously powerful radar for the time and could see farther than virtually any other mounted on a fighter. The infra red (IR) search and track system was an early addition to the standard ECM antenna and position light. The later addition of a tactical camera system (TCS) enabled the F-14 crew to visually identify hostile aircraft at ranges of about 10 miles. There's a video on youtube showing how that camera tracked Libyan Mig-25's in one engagement, which were trying to evade it by going into/out of burner. Didn't matter what they did, the F-14's TCS followed.

I'm not aware of another US fightet that fielded all 3 of those capabilities, at least until the F-35 came online. Hopefully PCA has all of that and more.

[sprstdlyscottsmn]

This is why I think the F-14 really excelled. Though not a stealth bird, it was a quantum leap in sensor capability over Russian and even US fighters.

First, you had the AWG-9. Outrageously powerful radar for the time and could see farther than virtually any other mounted on a fighter. The infra red (IR) search and track system was an early addition to the standard ECM antenna and position light. The later addition of a tactical camera system (TCS) enabled the F-14 crew to visually identify hostile aircraft at ranges of about 10 miles. There's a video on youtube showing how that camera tracked Libyan Mig-25's in one engagement, which were trying to evade it by going into/out of burner. Didn't matter what they did, the F-14's TCS followed.

I'm not aware of another US fightet that fielded all 3 of those capabilities, at least until the F-35 came online. Hopefully PCA has all of that and more.

Eh, yes it had systems galore, but the MMI was still 3rd Gen.

[quicksilver]

“3d Gen MMI”

Amen. Most don’t realize (or have forgotten) what a revelation the Hornet cockpit was in the early 80s.

[sprstdlyscottsmn]

The F-15 was a quantum leap compared to the F-14. Same idea (big powerful radar with advanced capabilities) but all controlled by a single person. The F-14 has the IRST/TCS, yes, but it had to be controlled by the non-pilot AND the RIO could only operate one system at a time. If the RIO wanted to use the TWS mode of the AWG-9 they couldn't even see the TCS image. The F-16 improved on the MMI from there with more HOTAS capability. The F/A-18 was the penultimate 4th-gen MMI. In some ways the cockpit of the F-22 has more in common with the F/A-18 than with the F-35.

[milosh]

Which is why they developed excellent (for that era) SA for MiG-31 and later for Su-27 (advanced datalinks).

Su-27 had awful SA thanks to the terrible radar display.

https://www.youtube.com/watch?v=LQkGkwZTeRM

I don't see what terrible is there (compared to F-15 from 1980s), and capability of data sharing between fighters in 1980s is superb (btw MiG-31 had it in 1970s). I don't know when F-15 fleet got similar capability? I know in 1980s was plan to install additional display for datalink (and of course datalink) in F-15C but that was canceled. Maybe in 1990s?

[knowan]

https://www.youtube.com/watch?v=LQkGkwZTeRM

I don't see what terrible is there (compared to F-15 from 1980s), and capability of data sharing between fighters in 1980s is superb (btw MiG-31 had it in 1970s). I don't know when F-15 fleet got similar capability? I know in 1980s was plan to install additional display for datalink (and of course datalink) in F-15C but that was canceled. Maybe in 1990s?

The radar system only provided limited and imprecise information on contact speed and altitude.
The radar functions were split between the HUD and HDD, forcing the pilot to constantly look between both to use the system.
The HUD radar function is unintuitive to read and use. Other HUD modes such as navigation cannot be used at the same time as conducting a radar search.

On top of all that, the Su-27's N001 radar was quite limited in performance, inferior to the AWG-10/APG-59 introduced on the F-4J in 1966.

Further, the radar warning receiver display is terrible; unintuitive and lacking in information it provides.

Overall, situational awareness in the Su-27 was quite bad by Western standards of the 1980s. However, the 'Westernized' cockpits of modern Flanker variants have eliminated much of these flaws.

[wrightwing]

F-22 has 8 tons of fuel; Su-57 with 10 tons has 25% more fuel, but that isn't enough to be flying around supersonic all the time, or even most of the time, so Su-57 will still be limited to primarily subsonic flight regimes.

The F-22 carries 9 tons (18,000lbs) of fuel, so the Su-57 doesn't even have 25% more fuel. There's no evidence of Su-57 motors having better TSFC, etc.... Just like F-22s, they'll be spending most of the time at subsonic speeds, and using supercruise when the tactical situation dictates.

[knowan]

The F-22 carries 9 tons (18,000lbs) of fuel, so the Su-57 doesn't even have 25% more fuel. There's no evidence of Su-57 motors having better TSFC, etc.... Just like F-22s, they'll be spending most of the time at subsonic speeds, and using supercruise when the tactical situation dictates.

I'd heard the F-22 had an internal fuel capacity of 8,200 kg, but looking into it further reveals a higher capacity:


That comes in at 3082 gallons / 20,649.4 lbs / 9,366.4 kg, so you are correct about 9 tons of fuel.

The Su-57 is claimed to have 10,300 kg of internal fuel, so it has only 10% greater fuel capacity.

[milosh]

8200kg on LM site:

https://www.lockheedmartin.com/en-us/pr ... tions.html

I found 410nnm is F-22 super cruise combat radius so supersonic combat radius > 750km mentioned for Su-57 v1.0 is realistic. It would need type 30 to have noticeable better supersonic combat radius then F-22.

@knowan

Su-27 had digital data link Lazur which would provide Su-27 radar info from ground control, A-50 and MiG-31s. I think MiG-31 and Su-27 had intra fighter link capability also because their fighter links are more less same. So even though N001 wasnt good pilot still had impressive SA.

[mixelflick]

So back on topic...

If we know the F-22/35 both carry around 18,000lbs of fuel (more in the C, less in the B), what do we think PCA will carry?

I'm thinking 30,000lbs minimum, unless some super fuel saving breakthrough has been made. There's a chance (some think a good chance) internal PCA fuel will be at least double the F-22/35. I tend to agree, given they want it to escort B-21's deep into Western China.

Thoughts?

[sprstdlyscottsmn]

Fuel fractions.

The F-22 in an AA mission is around 64,000lb TOW with 18,000 in fuel for a 0.28 fuel fraction.
The F-35A in an AA mission is around 49,600lb TOW with 18,500 in fuel for a 0.37 fuel fraction.

Even with a fuel fraction of 0.37, a 30,000lb fuel load would be a TOW of 81,000lb. That is a HUGE plane.

Remember that range is a function of cruise speed, weight, cruise L/D, cruise TSFC, and fuel fraction. If you keep speed, L/D, TSFC, and fuel fraction the same, and just increase the weight, you will not see an improvement.

If we say 20% of the internal fuel is used on takeoff and climb to cruise and 15% is reserved for descent,landing, and reserves, then we can get the aircraft weight at the beginning and ending of the cruise phase. Combining this with cruise L/D and we get drag, and that combined with TSFC we get fuel flow, for the cruise phase for the begging and ending of the cruise phase. Combine that with cruise speed and we get range over the cruise phase.

So we will initially hold cruise speed constant at 0.95M, TSFC at 1, and L/D at 12 for all aircraft. Fuel fraction is the only variable.

F-22 goes 697nm on 11,648lb of cruise fuel on an average of 4,549pph dropping from 60,416lb to 48,768lb
F-35 goes 975nm on 11,929lb of cruise fuel on an average of 3,330pph dropping from 45,930lb to 34,001lb
PCA goes 975nm on 19,500lb of cruise fuel on an average of 4,549pph dropping from 75,081lb to 55,581lb

So in that first run we can see that having more fuel weight does nothing if everything else is equal. Now, let's say that the F-22 has an L/D of 15 as its size allows optimizations for wave drag, and that the PCA also gets this advantage. This would give the PCA the F-22s design wave drag optimizations and the F-35s fuel fraction.

F-22 goes 871nm on 11,648lb of cruise fuel on an average of 3,639pph dropping from 60,416lb to 48,768lb
F-35 goes 975nm on 11,929lb of cruise fuel on an average of 3,330pph dropping from 45,930lb to 34,001lb
PCA goes 1219nm on 19,500lb of cruise fuel on an average of 4,355pph dropping from 75,081lb to 55,581lb

Now, what is important is the PCA fuel FRACTION not the fuel LOAD. The design question becomes how small of an aircraft can we build that has the drag optimizations we need, the power and payload we need, and can still hit a 0.37 fuel fraction.

This is why a G650 has nearly the same max range as a 747-8.
G650ER
cruise speed 0.85M
fuel fraction 0.465 (48,200 / 103,600)
L/D (Wing Loading 80.7 - Aspect Ratio 7.73 - Sweep Angle 36deg LE)
TSFC (Engine BPR 4.1 - OPR 43)
Range 7,500nm

747-8I
cruise speed 0.86M
fuel fraction 0.43 (426,109 / 987,000)
L/D (Wing Loading 165.6 - Aspect Ratio 8.43 - Sweep Angle 37.5deg LE)
TSFC (Engine BPR 8.0 - OPR 52)
Range 8,000nm

So the Boeing has a slight edge in cruise speed and a huge edge in TSFC, but the Gulfstream has the advantage of fuel fraction. L/D overall likely goes in Gulfstreams favor as the wing sweeps are very similar and while the Boeing has a somewhat better aspect ratio the Gulfstream crushes it in Wing Loading which impacts Cruise CL which squares for the Drag.

So here we have two aircraft with very similar flight profiles and shockingly close ranges given that one has nearly 10x the fuel of the other.

[marsavian]

So back on topic...

If we know the F-22/35 both carry around 18,000lbs of fuel (more in the C, less in the B), what do we think PCA will carry?

I'm thinking 30,000lbs minimum, unless some super fuel saving breakthrough has been made. There's a chance (some think a good chance) internal PCA fuel will be at least double the F-22/35. I tend to agree, given they want it to escort B-21's deep into Western China.

Thoughts?

Spurts has done the math but it will ultimately be driven by what the USAF specify as internal fuel radius and the L/D efficiency of the competing airframes. 30 klb minimum is a good shout as it will give about 1200nm internal fuel radius for PCA for an optimized airframe but what if they specify say 1500nm radius, that will require more fuel. I have a gut feeling it will be around 40-50 klb to give a noticeably larger range than F-35 as it has to be differentiated enough to justify the much greater expense. I wouldn't be surprised if the radius it takes for Israel to cover all of Iran stealthily or the US too from friendly Gulf states was the hidden driver. Iran is the big long term threat not China.

[knowan]

8200kg on LM site:

https://www.lockheedmartin.com/en-us/pr ... tions.html

I found 410nnm is F-22 super cruise combat radius so supersonic combat radius > 750km mentioned for Su-57 v1.0 is realistic. It would need type 30 to have noticeable better supersonic combat radius then F-22.

The entire F-1A fuel tank would have to be unused for 8,200 kg to be correct.

Also, you're talking about 80% greater supersonic combat radius for at best 25% more fuel (assuming 8,200 kg of fuel is the correct figure).
While combat radius vs fuel isn't an exact correlation, 80% greater range is still way too high for 25% more fuel.

Su-27 had digital data link Lazur which would provide Su-27 radar info from ground control, A-50 and MiG-31s. I think MiG-31 and Su-27 had intra fighter link capability also because their fighter links are more less same. So even though N001 wasnt good pilot still had impressive SA.

It doesn't make up for the terrible cockpit setup, as the datalinks contacts are still displayed with limited in the HDD, with all the limitations.