eagleAPG-63 was an excellent radar for its day, easily superior to the Sapfir radar on the MiG-23. It lacked the raw power of the F-14’s AWG-9 however. The MiG-23 had some good qualities but avionics wasn’t one of them AFAIK.
The F100-PW-100 engine used by the A/B was a very advanced design for the time but suffered from some teething problems. The F100-PW-220 used by later F-15s corrected these problems and are extremely reliable but max thrust was reduced slightly.
The C/D also added the capability for CFTs (aka FAST packs). These could add a lot of fuel for a minimal increase in drag, although they are rarely seen on the C/D models other than those deployed in Alaska. Standard on the F-15E however.
While the -220 engine’s static thrust is less, actual performance is quite a bit better. Check the attached charts, top speed for a fully armed jet went up from Mach 1.8+ to Mach 2.2 at 2000lbs more weight for the C model. No info about -220 engine trim though.
The CFTs add more drag at supersonic speeds and some 2350lbs of non jettisonable weight. That’s probably why they were used mainly over Alaska and Iceland to intercept bombers.
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eagleJust pointing out a huge list of targets that fall in easy prey category for an F-15 and should be put under the category- hardly worth mentioning. Period.
That’s true but thats true for most fighters. More so for modern age jet fighters. Even back in the day of glorious guns only fights, many kills were achieved by sneaking up from behind.
eagleThe 23 WAS a generation older, let`s keep it real.
In service timing that`s a different story, conception & execution wise they are not in the same group.
Bottom line, the most acclaimed fighter jet for it`s hunting prowess actually has 13 (out of 100 + ) victories worth mentioning.
If we keep cool headed the 9 USAF ones were more than one sided scenarios, in those cases their enemies were badly outnumbered and outgunned plus they took on the little brother from the Cold War dance pairs:
F-16 – MiG-29
F-15 – Su-27
It does not matter if the MiG-23 was a technological generation older or not. What matters is entry into service. This means strictly speaking every air force has its own generations with the next generation simply being the one that replaces the older one. There isn’t necessarily much improvement.
The MiG-23M first flew in 1972, same year as the F-15, service entry was in ’73 iirc, which is much closer to the F-15’s in ’74 compared to 1983 for the MiG-29. So yes, the MiG-23 is very much an F-15 contemporary.
Much more important than that are exact engagement conditions such as pilot skills and of course the specs of involved export models aka monkey models.
eagleBut that is just a mockup. I don’t think an ejector launch capable ASRAAM exists currently neither does the trapeze rail launcher. ASRAAM (and AIM-9) are external only for the time being.
eagleWould aye. As far as aerodynamics are concerned, you’ll lose your Reynolds number/Mach correlation, but that is not such a massive deal nowerdays.
As far as systems go, its just scaling.
As far as engines go, you’d assume they’d design the scaled up version around the engine they want to use.
If its a prototype, then it doesn’t have to be perfect, just representative enough.
Yes it would scale if you were to replace the RD-93 with the AL-31 and enlarge the plane around it by ~50% also.
As per madrats proposal to replace afterburning RD-93s with non-afterburning AL-31s in the same thrust class, it wouldn’t scale.
eagleWhat would be the preferred F-35B/Stormshadow configuration? Only the inner wing pylons are rated for weapons this size so we have a bit of a Typhoon situation revisited here.
2 1300kg external weapons on a jet with a 450nm radius when clean, the resulting combat radius will not be impressive.
A single weapon? Probably not much better due to asymmetric loadout.
Or a single weapon plus 1 external fuel tank. The proposed 426 gal tank would balance things out at an estimated weight of 1400kg. That would require the fuel tank to be available of course.
eagleNo matter what eagle wants to argue about, the fifth generation is using wet thrust less and less. The dry thrust is where it’s at for getting to a good combination of range and low supersonic speeds. Wet thrust is cool to see, but operationally it’s an expensive expenditure.
You clearly didn’t get it. But all the 5th gen projects should give a clue. Yes, they all include a/b engines.
@ Amiga500: With different type of engines, it wouldn’t scale, that’s the point.
eagleAnglo-French FCAS May Not Be Unmanned
Something has to replace those Typhoons, Rafales and Tornados eventually. Anglo-French cooperation has worked pretty good in the past. I’d leave it at that.
Teaming up with other companies from overseas is probably ok, with other governments not so much…
eagleIt’s a prototype program currently, all low rate parts production. Most of it customized work. That first point is the least worry.
Except that the prototype would be utterly useless as you’re proposing a different aircraft.
Strike fighters spend the vast majority of their time in dry thrust. Each generation of fighter spends less in wet thrust than the previous. The trend is toward afterburning being an after thought. Sudden acceleration is less important than sustained. You do not see afterburners on many strike aircraft simply because they are unnecessary.
Now you’re talking fighters again. (Multirole) Fighters such as the J-31 have afterburners. Subsonic strike aircraft don’t. Supersonic strike aircraft such as the Tornado or the JH-7 do. What you have in mind is a supersonic strike aircraft like the Tornado (never mind the J-31 is actually designed to be a fighter!) but with fat engines instead of smaller ones with afterburners. Ever wonder why such a thing does not exist?
Yes, jets spend the vast majority of their time in dry thrust. That is exactly the reason why afterburners are more efficient than bigger engines. Because your J-31-AL31 is lugging around huge oversized engines that add considerable weight and drag yet leave less space for fuel and have to run at non-efficient settings. Meanwhile, the J-31-RD93 is lighter, less draggy, carries more fuel and its engines operate closer to optimum settings at subsonic cruise giving it more range. Yes, it needs a bit more fuel to take-off and for subsonic acceleration, but it can afford it. From around Mach 0.85, it will leave the -AL31 in the dust and of course, it will fly rings around it.
So you see, afterburners are not an afterthought. Subsonic strike aircraft don’t need them, supersonics do.
Sudden/sustained acceleration makes no sense. Faster acceleration is always better, no? Especially when you use less fuel in doing so. Because your -AL31 will take so long it uses more fuel.
Efficiency of the engine is not an impediment. The engine has a solid track record. It’s power may die off at supersonic speeds, but that is inconsequential if you do not intend to fly beyond the limits of your exhaust velocity. Optimal speed for combat doesn’t even approach supersonic speeds, especially in a turning fight.
Now it’s a fighter again. Anyway, in this case, it will be hopelessly outturned and out-accelerated anyway. It has nothing to do with top speed.
eagleYou might want to compare the dry thrust of the AL-31 to the wet thrust of the RD-33 again, because the former has more power than the latter in every comparable generation. The diameter would increase slightly, true, but length not so much as you’d think. And the weight gain would be about a quarter metric ton apiece using a conservative guess.
The airflow of the dry AL-31 wouldn’t increase over the wet RD-33. But your efficiency as measured by SFC would be quite a dramatic shift for a dry only AL-31, which we have already heard can propel an aircraft to Mach 1.3 without any afterburner! Mind you strike aircraft don’t even typically venture into supersonic range until you get to the F-35 and F-22. So you’re getting the aircraft into an efficient performance band comparable to the competition.
I don’t hope they do this, I fear this to be an easy change towards potency.
You would need to redesign the complete fuselage aft of the cockpit. And since the cockpit is attached to the rest, you would need to redesign that as well. Increased diameter would need new engine bays and thus a new rear end.
Airflow is at maximum at dry thrust, afterburners don’t increase airflow. At about 50% more dry thrust, the AL-31 needs about 50% more air aswell –> enlarged air intakes which naturally run through the fuselage –> new center fuselage.
Then there’s the thrust/speed issue. Sure, static sea level, dry AL-31 and wet RD-93 are about equal. But the dry AL-31 runs out of steam at supersonic speeds pretty quickly. Remember, thrust is mass times exhaust velocity, relative to aircraft velocity. You can have all the static sea level thrust in the world, if your aircraft speed is approaching exhaust velocity, thrust goes towards zero. Afterburners increase thrust by increasing exhaust velocity so at supersonic speeds an RD-93 in burners will have considerable more thrust compared to a dry AL-31. Acceleration will be poor also, even supercruisers use afterburners to accelerate.
What gives you the impression the J-31 is a strike aircraft? It’s obviously a fighter, multirole maybe, but first and foremost designed as a fighter. Your J-31-AL-31 would be seriously overpowered for a subsonic strike aircraft with some sort of supersonic dash capability while the wing and airframe shape plus oversized engines not running at their most efficient setting make it a poor subsonic cruiser. If you want something subsonic with supersonic dash capability, take a look at the A-7F. Just add an afterburner and its good for Mach 1.4 but still a subsonic cruiser.
Seriously, what you’re proposing is a completely different aircraft that is neither a fighter nor a good striker. There is a reason no such aircraft exists. The closest thing is the Harrier with its high TWR at dry thrust, but for different reasons, and its subsonic.
eagleThe AL-31 is a bigger engine so it would require a complete redesign of the airframe starting with the air intakes.
It would not provide similar thrust throughout the flight envelope. Dry thrust goes down with speed and altitude much quicker than wet thrust. Esp. for turbofans. Remember the Harrier? I estimate the topspeed of a J-31-AL-31 would be around Mach 1.3.
eagleNot a bad looking machine but I’m not certain what role it is meant to play with the J-20. The Chinese take on the “hi-lo” mix? But which is for air-superiority and which is for strike?
It’s either a hi-lo mix f.e. the heavy F-15 for BVR combat, the simple F-16 for WVR combat, or 2 jets for 2 (main) missions f.e. F-14/A-6 combo. Hi-lo doesn’t mean the high part is air superiority and the low part is air to ground.
With the J-31 being smaller than the J-20, but still a medium sized jet, I’d say its a high-medium mix for any role. I suppose both are going to be multirole.
eagleThe engine is most smoky at full dry thrust, no smoke on afterburner. So one engine at less than full dry and the other on AB makes less smoke than both engines running at full dry power. I think I read the same story.
eagleBAC Jet Provost, same as in your avatar?
eagleFine. But the question that remains unanswered is why is China trying so hard to replicate the function of the F-35’s Helmet Mounted Display System and DAS on their J-31 and J-20?
Is the DAS confirmed? As to why, why not? Modern fighters have HMDs and missile warning systems so it seems pretty straightforward for the J-31 to have them aswell. That doesn’t say anything about the capability of those systems though. F.e. the F-35 DAS is more than a missile warning system.
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