MiG-21 keeps evolving

[tomo pauk]

For sake of discussion, lets say that MiG bureau keeps the basic MiG-21 design as an insurance if the variable geometry does not work out as it was hoped for, and indeed MiG 23 encounters more of the serious problems than it did.
Development of the legacy fighter will need to address the shortcomings of it, like the low-speed abilities, long take off and landing run, short range/radius etc. Engines used are what MiG-21 use up until some time of late 1970s, with development itself continuing into late 1980s/early 1990s.

 

[mack8]

Back in the late 1960s- early 1970s, there were some projects of the MiG-21 with larger wings of less sweep and 6 hardpoints, one still delta with very small LERX-es, and one with even less sweep, LE devices and LERX-es like on F-5E, either of them would have been good on a bis airframe, offering increased turning performance. What would this be called, MiG-21bis-2 or MiG-21bis-80, or MiG-21Mbis?

And on the MiG-23, it was a mistake to export the MiG-23MS, which hurt the reputation of russian aircraft, they might as well just sell the MiG-21bis instead which has the same radar and missiles. Then perhaps they could start exporting the MiG-23MF a bit earlier, which at least has two tangible advances, it's LD/SD radar and BVR misiles.

Back at the MiG-21, further developments will need newer electronics, but this will take design resources away from other projects. Just like the RP-22 is based on Smerch techology, perhaps a miniaturized S-23ML can be built to fit in the MiG-21 nose? Might offer say a 40-45 km range (compared to 30 km on the bis) and some LD/SD capability. Missiles wise, they could integrate the deadly R-73, never mind any other short range radar guided missile. Come to think of it, perhaps the R-3R was a waste of time? I'm not sure if there ever been an R-3R kill, or RS-2US kill for that matter. The americans gave up on the AIM-9C. Maybe instead of working on the R-3R the design resources could be used to build an earlier R-13M?

They could perhaps fit the SPO-15 RWR, ASO-2 IRCM, maybe the ASP-17 gunsight on this MiG-21bis-2 as well?

Further down the line we get into Kopyo (Zhuk based)/R-77 territory and something akin to MiG-21-93, but slightly earlier. Would the RD-33 fit into a MiG-21? Well, just like PRC built J-7s into the 2000s, and JL-9 even now, maybe USSR/Russia would get to do that too.

 

[z42]

One thing limiting the development potential of the Mig-21 is that with the front mounted air intake, there is very little volume for the radar antenna. Some later Mig 21 variants did have a tiny radar dish mounted in the nosecone. With more and more emphasis on the electronics side of things, this is going to be a big handicap.

 

[tomo pauk]

One thing limiting the development potential of the Mig-21 is that with the front mounted air intake, there is very little volume for the radar antenna. Some later Mig 21 variants did have a tiny radar dish mounted in the nosecone. With more and more emphasis on the electronics side of things, this is going to be a big handicap.

Good points.
Soviets were thinkering with the Ye-8, that was shaped sorta pre-F-16, plus canards. Unfortunately, engine choice - literary - killed the project. There was a lot more space for electronics in the front section of the aircraft there. Not having the air passage in the 1st third of the fuselage should also allow for a bit better fuel tankage.
Also, as noted in the post above by another member, the JL-9 shows how it could've been done.
Chinese were also experimenting with the J-7FS and J-7MF, side elevations of the 1st third of A/C looking like that of the Crusader and E-fighter, respectively.

 

[Admiral Beez]

Chinese were also experimenting with the J-7FS and J-7MF, side elevations of the 1st third of A/C looking like that of the Crusader and E-fighter, respectively.

China's are basically where the MiG-21 would have evolved to.

 

[tomo pauk]

Grumman was trying to get into morphing the Chinese F-7 into a more modern fighter with the 'Sabre' design.
picture1
picture2

'Solid' nose, side intakes, Western avionics and upgraded weaponry, later a bigger wing, among other things. Kinda shows how might've the Soviet approach looked like.

 

[SaparotRob]

Go Grumman!

 

[z42]

Good points.
Soviets were thinkering with the Ye-8, that was shaped sorta pre-F-16, plus canards. Unfortunately, engine choice - literary - killed the project. There was a lot more space for electronics in the front section of the aircraft there. Not having the air passage in the 1st third of the fuselage should also allow for a bit better fuel tankage.
Also, as noted in the post above by another member, the JL-9 shows how it could've been done.
Chinese were also experimenting with the J-7FS and J-7MF, side elevations of the 1st third of A/C looking like that of the Crusader and E-fighter, respectively.

Yes, it wasn't as easy as just moving the intake and problem solved. Early jet fighters had the intake at the front for good reason, namely access to undisturbed air over the flight envelope, and early jet engines were very picky about smooth inlet airflow. It took advances both in aerodynamics (specifically, inlet design) and engine design before inlets could be successfully moved backwards on the airframe. Even the West wasn't always successful with this, see F-14A.

For an overview on issues with jet inlet design, see https://eprints.soton.ac.uk/46202/1/AIAA-26830-529.pdf

 

[tomo pauk]

Yes, it wasn't as easy as just moving the intake and problem solved. Early jet fighters had the intake at the front for good reason, namely access to undisturbed air over the flight envelope, and early jet engines were very picky about smooth inlet airflow. It took advances both in aerodynamics (specifically, inlet design) and engine design before inlets could be successfully moved backwards on the airframe.

Soviets moved to the side intakes by the early 1960s, as it was the case with Su 15 or MiG 25.
I have nothing against the ventral intake, though

Even the West wasn't always successful with this, see F-14A.

It probably also had a lot to do with the TF30 not being that well suited for fighter maneuvers IIRC.

 

[GTX]

Don't forget the developments included in the Indian MiG-21UPG/ MiG-21 Bison. This includes:

• An overhaul of the airframe, with a 10-year service life extension.
• A new drop-shaped canopy with a single-piece windscreen replaces the old one.
• A new head-up display along with multifunction display.
• Cockpit controls are redesigned to a HOTAS arrangement.
• A new autopilot is added, as well as an inertial navigation system and GPS receivers.
• The aircraft are equipped with the Phazotron Kopyo (Spear) radar, developed from the Zhuk and capable of simultaneously tracking eight targets and engaging two of them.
• Compatibility with new air-to-air weaponry, like the R-27, R-77 and R-73 missiles, the latter of which can be cued to a helmet-mounted sight. Other new weapons include the Kh-31A anti-ship missile and the KAB-500Kr guided bomb.
• Chaff/flare dispensers are installed on the upper side of the wing root.
• The old radar warning receiver is replaced by the Indian-developed Tarang, and an internal jammer is added.

 

[RpR]

J-7FS

 

[Admiral Beez]

How would the MiG-21 do with a GE or P&W engine?

 

[nuuumannn]

Extending the MiG-21? Ta Dah!

DSC_6236

The Shenyang J-8 was essentially a heavily modified twin-engined, extended range MiG-21, which was licence-built in China as the Chengdu J-7, which underwent considerable modification for export as the F-7 Air Guard. In this variant, the aircraft was fitted with Western air-to-air missiles, French Matra Magics and Western avionics, for Pakistan.

This is what Wikipedia says about the export variant of the J-7:

"In 1987, the J-7E was released, having a greatly improved wing, among other improvements. It was roughly 45% more maneuverable, and its takeoff and landing performance was greatly increased. It was also equipped with a helmet mounted sight, as well as being the first MiG-21 variant to be equipped with HOTAS and a multipurpose display. Many of the electronic components were British in origin, such as the gun sight and the multi-purpose display. The aircraft is capable of using PL-8/Python 3 missiles with both the helmet mounted sight or the radar fire control, but the two are not connected. The pilot may use only one system at a time.

In the mid 1980s, Pakistan requested an aircraft with greater radar capabilities. Both the standard radar and the British Marconi radar were plagued by ground clutter, but China did not have any experience with air to ground radar at the time. In 1984, Pakistan provided assistance by having their American-trained F-16 pilots provide training on proper ground attack radar operation, which enabled the Chinese to develop the J-7M. In the late 1980s, the J-7MP and J-7PG introduced significant upgrades to the radar system by converting to an Italian FIAR Grifo-7 radar, more than tripled the effective range of the radar, as well as greatly increased the maximum angle for target detection."

This is an early production J-7 I, which was essentially a Mig-21 F-13 with one-piece forward opening canopy.

DSC_6229

The J-7 II model featured new avionics and weapons carriage capability, with a conventional two-piece rear opening canopy. This is a J-7E based on the J-7 II, as mentioned in the Wiki text above.

DSC_6233

The J-7 III was unique in that the Chinese did not acquire a licence to build it, it was a reverse-engineered MiG-21MF export variant based on an airframe acquired from Egypt. The J-7 IIIA variant had revised avionics and weapons fit and a variant was proposed that could carry the Matra Magic AAM.

DSC_5989

Let's not forget that the Chinese had the MiG-21 in production for 50 years, so they got a shed ton out of it. Not mentioned are the JJ-7 derivatives, two-seaters heavily modified as advanced fast jet trainers, again, which ended up very different from their Soviet origins.

Perhaps the Ultimate MiG-21 modification was the J-8 II, later the J-8B. Again, from Wiki:

"In 1980, Shenyang began investigating improving the J-8 by using ideas embodied by contemporary aircraft like the McDonnell Douglas F-4 Phantom II and the Mikoyan-Gurevich MiG-23. Gu and He Wenzhi began design work on what became the J-8 II (later the J-8B) in 1982.

70% of the J-8's airframe structure and systems were reworked. The nose air intake and its shock cone were replaced with an ogival radome and lateral air intakes to create room for the larger Type 208 pulse-Doppler radar. The number of external hardpoints increased to seven; a single Type 23-III cannon was carried. The aircraft was area ruled and the powerplants replaced by the more powerful WP-13A-II turbojets. The two ventral fins under the tail were replaced by a single larger fin copied from the MiG-23; the fin folded to starboard on the ground for ground clearance. Performance was greatly improved with the higher thrust-to-weight ratio, as was handling. Improvements to manoeuvrability was limited due to the 6.9 g limit. The prototype was completed in March 1984 and made its first flight on 12 June. Production and entry into service was approved in October 1988. The greatest problems were with the avionics, particularly the radar.

The improved J-8 IIB (or J-8B Block 02), fitted with the KLJ-1 (Type 208A) radar and avionics from the J-7C, flew in November 1989 and entered production in 1996."

Of considerable interest was the Peace Pearl Program. "The 1986 "Peace Pearl" program with the United States included upgrading 50-55 J-8 IIs with US avionics, Martin-Baker ejection seats, and possible US engines for US$502 million. Two aircraft were flown to the US for prototyping, and work was underway by the time of the 1989 Tiananmen Square protests and massacre. Peace Pearl was cancelled by China in 1990; the US had permitted it to continue despite the post-Tiananmen sanctions."

 

[GTX]

How would the MiG-21 do with a GE or P&W engine?

I don't think any modernist P&W ones would fit but a GE F404 or F414 might (with some engineering). Comparing to the R-25-300 as used in the MiG-21bs with the F404 and F414 we see the following:

	Tumansky R-25-300​	F404-GE-402​	F414-GE-400​
Length	4.615m	3.91m	3.91m
Diameter	1.191m	0.89m	0.89m
Dry Weight	1,212 kg	1,035 kg	1,110 kg
Military Thrust	40.3 kN	48.9 kN	57.8 kN
After burning Thrust	69.6 kN (97.1 kN emergency)	78.7 kN	97.9 kN
SFC	Military: 27.2 g/(kN.s) Afterburner: 63.6 g/(kN.s) Afterburner emergency: 94.4 g/(kN.s)	Military: 23 g/(kN⋅s) Full Afterburner: 49 g/(kN⋅s)	Military:​ Afterburner:
Thrust-to-weight ratio	5.6 (max afterburner)	4.8 (dry) 7.8 (afterburner)	9 (afterburner)

You might be able to fit the GE engines with some work but the payoff might be worth it. Or you could just buy a newer fighter.

 

[tomo pauk]

I don't think any modernist P&W ones would fit but a GE F404 or F414 might (with some engineering).

P&W 1120 perhaps? Granted, it wasn't manufactured beyond a number of prototypes.