MiG-21 modeling discussion.

[+yakarov79 11,082]

Maybe this is not a good place to talk about it, but I feel it is necessary to point out some things and misconceptions about Fishbed.

According to the discussion from the screenshot thread:

On 5/10/2024 at 9:50 PM, Gepard said:

The M has no mirror and was delivered without protection plates. The task of the protection plates is to protect the auxillary air intake from gun smoke, which can cause engine stall. Thatswhy this plates were fitted later during planes overhaul schemes.

 

On 5/10/2024 at 10:13 PM, FLOGGER23 said:

I got the M bort records from http://www.forgottenjets.warbirdsresourcegroup.org/ and based on it, I saw some pictures showing the gun blast panels

 

 

Those are not gun blast protection plates, The Instruction, and technical manual clearly state what it is. During production of the 21 many changes were made on the production line - and then some of the changes were retrofitted to previously produced types. One of those changes was adding a small fence under the auxiliary air intake under the cockpit on both sides of the fuselage.

Unfortunately "gun blast" myth started in the wets long ago by so-called experts - claiming that plates protect engine from gun blasts.

They are FOD protection of the engine on take-off, landing, and taxing from anything from the nose gear. I think in the manual it is called Взлётная створка воздухозаборника - or something like that....FOD plates are installed between the 9th and 10th fuselage frame to protect against ingesting foreign objects into air channels.  Auxiliary intakes themselves are operated by pressure differences outside and inside the air intake channels. Those covers in the intakes would never be open when a gun is firing. Auxiliary intake doors are there to relieve pressure difference and provide additional airflow to the engine on take-off and landing (low speed). On the inside lip of intakes, there is a seal that makes them completely tight, but only under pressure. Because doors are simply hinged, on the ground those intake doors would never be completely closed and there is a small around 1 cm gap. In-flight they close totally with the pressure inside the air duct forcing them to the outside surface of the fuselage. 

So during the flight - when you are firing a gun - the doors are completely closed. It is not usual to fire a 23mm gun on the ground with a running engine while you are on the airfield surrounded by ground crew, aircraft, and vehicles. So there is little chance of any gun gases coming into the intake and damaging the engine. 

And yes, those plates can be observed on two-seaters too - which has no gun, and at some point, plates were retrofitted to older models, 

 

On 5/11/2024 at 3:31 PM, Gepard said:

There is a confusion with MiG-21PFM vs PF designation. When the MiG-21PF was delivered it was not able to carry the Monsun. After an midlife update it got the capability to carry Monsun twin rails. The modified planes were in the East German Air Force (LSK) called MiG-21PFM. Later the soviets delivered their own MiG-21PFM, what posed designation problems in the LSK. The same designation for different versions of the MiG-21.  Thatswhy the soviet MiG-21PFM was called MiG-21SPS in east german service

 

that is why when there is confusion it is "better" to address them by "factory given name" designation.

F - prod.72

F-13 - prod. 74

PF - prod. 76

FL - prod.77 - export version of PF 

PFM- product 94 (изделие 94) and type 94N for a nuclear strike capable model.

R- prod.94R

M- prod.96, MF- prod 96A , but there are also export variants that also had different designations like 96A00

etc...

 

SPS system  (blown flaps) was introduced when PF and PFM were in service already. I guess countries were adding local names to an existing fleet of 21 to avoid confusion. However  SPS is not an official MIG-21 subtype.

In Poland, we had PF and PFM but unofficially PFM was called SPS just because it was the first to have that system installed.

And yes East Germany had a strange way of dealing with designations - here PFM has nothing to do with soviet PFM - as it was PF modified with RP-21 radar....East German PFM is izd.76A while "true" PFM is izd.94 (including early production of PFS.  Then izd.94A in German service was SPS.

 

 

 

Edited June 2 by yakarov79

[+Gepard 11,289]

4 hours ago, yakarov79 said:

Those are not gun blast protection plates, ...

This statement is wrong and true at the same time. Of course this plates were helpfull to avoid FOD. Thatswhy they were refitted also on gunless MiG-21 versions.

But the origin of this plates were war experiences. When the MiG was in a close dogfight at low speeds and low altitudes, the plane was flown with a good angle of attack and full afterburner. In such situation the engines needed much more air, than the air intake could deliver. The doors of auxilary air intakes were opend automatically. If in such a situation the gun was fired, the gun smoke had a good chance to were sucked into the auxillary air intakes, which caused compressor stalls and a flame out. The engine died and the pilot had only one choice: to use the ejection seat.

During Vietnam war, but also during arab-israeli  clashes, some MiG-21 pilots shot down themself by firing the gun during low speed, low level dogfights.

The cure of the problem was to add the protection plates, which, as a side effect, were helpfull to avoid FOD.

So i have learned the story of the protection plates from east german fighter pilots.

[+yakarov79 11,082]

In a small photo above that I attached (Czech 5603), it is clearly visible that the gun is more aft of those aux intakes. Gun is installed after the 10th fuselage frame So I am not sure how gases from a gun can go there considering that the aircraft is moving forward. (this behavior would be against the law of physics).

And why are those FOD plates installed on UM then? No gun there. (yes I know some could carry gun pods, but some never carried anything and still had fod plates installed).

There is nothing automatic on those doors, simple hinge and flapping doors, not even spring loaded. Gravity is operating those doors.

Had no chance to talk to 21 pilots, but I had a lot of time with guys who kept them flying....

55 minutes ago, Gepard said:

When the MiG was in a close dogfight at low speeds and low altitudes, the plane was flown with a good angle of attack and full afterburner

hmm....not sure but seems like one contradicts another.

[+Gepard 11,289]

42 minutes ago, yakarov79 said:

 Gravity is operating those doors.

No.

If the suction of the engine becomes too great, the doors of auxilary air intakes open.

This photo shows the position of gun muzzle and auxillary air intake at the MiG-21F-13:

There is a fair chance, that gun smoke can get into an opend door.

Edited June 2 by Gepard

[+FLOGGER23 3,063]

Hey guys

2 Things:

1- If there are FOD doors, why no MiG-21R/RF have them? (at least the big majority) They have no gun provision.

2- If the plane is rolling at, let's say 40-60 KPH in the strip, there are chances something can avoid the FODs and get into the engine, me thinks...

Nice talk BTW

[+yakarov79 11,082]

28 minutes ago, Gepard said:

There is a fair chance, that gun smoke can get into an opend door.

Yes indeed, But this is an old lady. 

We have to decide which product we are talking about - In the photo we have MiG-21F-13, forward cannon, aux intake no plates -the pilot is doomed. And I do not remember seeing plates on F/F-13. Later models izd.76/94 have gun provisions for gun pod GP-9 but moved aft 10th fuselage frame. 

Here Mig21PFS (izd.94) even here it is visible that gun muzzle is far beyond aux intakes.

and attachment point between airbrake panels.

 

17 minutes ago, FLOGGER23 said:

1- If there are FOD doors, why no MiG-21R/RF have them? (at least the big majority) They have no gun provision.

Some had retrofitted, some not. Even UM had them. But not in Poland for example. But here:

 

30 minutes ago, FLOGGER23 said:

2- If the plane is rolling at, let's say 40-60 KPH in the strip, there are chances something can avoid the FODs and get into the engine, me thinks...

well, how a piece of the metal plate  - can stop gasses from going into the intake? Yes it could deflect, but how those gasses are even near intakes since the muzzle point is behind intakes? 

[+FLOGGER23 3,063]

14 minutes ago, yakarov79 said:

Some had retrofitted, some not. Even UM had them. But not in Poland for example. But here:

Agree on the retrofit, however the UMs had provision for a gun, and i am referring to the recon birds.

On another subject, this thread should have called MiG-21 Variants discussion, so we can discuss the rest of variants i have on the pipeline...

What you say??

[+yakarov79 11,082]

sure. 

and how many UM/US have you seen with guns? Does anyone even remember the designation of this gun? It was almost never fitted. So I honestly doubt that they would consider installing gun blast plates just because maybe someone will find in storage an old training gun and have a wish to fit it. 

For some time I was considering the presence of FOD based on which engine is fitted to the airframe (R-13) But I am not going to say that this is true. 

[+Gepard 11,289]

The gun of the trainers was an 12,7 mm machingun. I think it was an Afanasiew A12,7. It was used very seldom. It was placed in a streamlined container. I will have a look into my archive. Everywhere in the depth there is a photo of this container.

The protection plates came with the MiG-21MF. IIRC 1972 or so. The MF was the modified version, with some changes made after war experiences. Like mirror, R-13 engine, protection plates etc. BTW the mirror was not a simple mirror, like in a car. It was a periscope, the light had to go a zig-zag path through this device.

Back to the protection plates. In service it showed, that this plates also protected against FOD. Thatswhy they were refitted also to gunless MiG-21 versions.

The MiG-21RF came before the MiG-21MF. It was the first version with the long back tank. IIRC it based on the MiG-21PFM. Thatswhy it had, when delivered no protection plates.

[+Gepard 11,289]

Pictures of the MG pod of MiG-21 trainers were easier to find, than expected:

It's difficult to see. It is the small "bubble" under the belly.

Here a close shot:

And here from an other angle:

 

 

[+yakarov79 11,082]

No way that any gas from this pea shooter will go forward into intakes when "Sparka" is moving at 450-600km/h.

[+FLOGGER23 3,063]

9 minutes ago, yakarov79 said:

No way that any gas from this pea shooter will go forward into intakes when "Sparka" is moving at 450-600km/h.

Safety goes first...

16 minutes ago, Gepard said:

Pictures of the MG pod of MiG-21 trainers were easier to find, than expected:

It's difficult to see. It is the small "bubble" under the belly.

Thanks i needed those angles as i have the ones from the 4+ magazine.

Now, correct me if i am wrong, the trainers, the main variants are:

-MiG-21U-400, with F-13/PF wings, tail, SK seat, and chute (under the fuselage), no periscope.

-MiG-21U-600, with blown flaps and PFM tail with the chute at the VTail base, no periscope.

-MiG-21US, with KM-1 seat, periscope in the instructor seat.

-MiG-21UM, with the 3rd generation avionics, a distinctive antenna on the aft spine.

All trainers had the bigger wheels and the bigger fuselage bulge.

Hope i got it straight, if not, all corrections are welcome.

[+yakarov79 11,082]

9 minutes ago, FLOGGER23 said:

Safety goes first...

yeah, mostly because pod was almost never used. This is safety. 

[+Gepard 11,289]

4 hours ago, FLOGGER23 said:

Now, correct me if i am wrong, the trainers, the main variants are:....

-MiG-21UM, with the 3rd generation avionics, a distinctive antenna on the aft spine.

 

Only short. The blade antenna on the aft spine is not a sure distinctive object. There are some older MiG-21 trainers, which were refitted with this antenna.

Here a MiG-21U with this antenna:

A sure distinctive object of the MiG-21UM is a AoA sensor on the left side of the nose.

 

Edited June 2 by Gepard

[Svetlin 541]

I have read that the E-7R, which was the prototype for the MiG-21R, was based on the MiG-21PF and in fact it was a serial MiG-21PF that got converted. The first 2 MiG-21R were in fact serial MiG-21PFM (izd. 94) converted into MiG-21R.

The MiG-21RF was the export version of the MiG-21R. Since the MiG-21R was based on the MiG-21PF, it did not come from the factory with the subject plates.

I myself am more willing to take these plates as FOD protection measure. If you check a side profile of a MiG-21 with such plates installed, you will notice the plates are not simetrically placed under the auxiliary intakes, meaning if you find the center of the auxiliary intake and draw a straight line perpendicular to the plates, that line will not cross the center of the plates. The plates are placed slightly ahead and under the auxiliary intakes, which indicates they are meant to deflect stuff coming from infront below rather than from behind below. And if you connect the center of the auxiliary intake with the center of the plate below it and extend the line, the line will touch the front wheel. That may be just amateur logic, but to me it indicates the plates are meant to protect from debris, lifted by the front wheel.

Edited June 4 by Svetlin

[OlWilly 130]

This thing?

[+FLOGGER23 3,063]

14 hours ago, OlWilly said:

This thing?

Nope, for the side ones.

Edited June 4 by FLOGGER23

[OlWilly 130]

7 hours ago, FLOGGER23 said:

Nope, for the side ones.

Ahh, I misread the schematic.

The only way to say for sure would be to see it in the official technical description of the relevant 21 model. Book 3 preferably, this is where it should be

Online, I have seen book 3 only for 21UM and it has no mention of these plates

[+Gepard 11,289]

For me it seems to be, that the print is a description how the GSh-23 gun is fitted under the belly of a MiG-21M or later fighter version. Maybe i'm wrong, but if i'm right, then could part 1 be the steel plate, that protects the fuselage from muzzle flash.

[+FLOGGER23 3,063]

25 minutes ago, Gepard said:

For me it seems to be, that the print is a description how the GSh-23 gun is fitted under the belly of a MiG-21M or later fighter version. Maybe i'm wrong, but if i'm right, then could part 1 be the steel plate, that protects the fuselage from muzzle flash.

And now, that is a task to be added to the pendings, again, as a bump map.

Thanks, guys, I may have more questions coming.

[+FLOGGER23 3,063]

On 6/2/2024 at 2:09 PM, Svetlin said:

The MiG-21RF was the export version of the MiG-21R.

I remember the RF was an specific version of the recon bird with the cameras mounted under and part of the fuselage, while the variants using the recon pods were called R, domestic or export

Now, talking about the recon pods, does anyone have details of them, the D/N/R? like the stencils and panelings?

 

 

[Svetlin 541]

3 hours ago, FLOGGER23 said:

I remember the RF was an specific version of the recon bird with the cameras mounted under and part of the fuselage, while the variants using the recon pods were called R, domestic or export

Now, talking about the recon pods, does anyone have details of them, the D/N/R? like the stencils and panelings?

Yes, exactly, Egypt made a local modification to the MiG-21R by adding permanently cameras in a fairing under the nose as in your picture.

Sadly I do not have good reference for the recon pods, but it seems the old Eduard 1/48 MiG-21R model kit would be a good reference with respect to stencils and panel lines.

Here is a review of the model kit: https://www.themodellingnews.com/2014/06/review-eduards-fishbed-mig-21r-in-48th.html

[+Gepard 11,289]

I'm not sure wheter the egyptian RF were modified R. It could be, that it are modified MF. The camera pack is installed at the place, which originally was used by the GSha-23 gun and the ammo storage of the gun.

EDIT:

I have searched a german forum about the MiG-21RF. There i found, that only 12 planes were built. The camera pack was not installed at the place of the GScha-23 gun, but at the place of the akku (battery) package. The akkus were relocated to somewhere in cockpit area. The engine was definitly the R-13F-300.

Here a photo of an RF, which i found in the net, at an ukrainian aircraft factory in 1990th (i think it was in that timeframe). It was there for overhaul and repair.

 

Edited June 5 by Gepard

[Svetlin 541]

2 hours ago, Gepard said:

I'm not sure wheter the egyptian RF were modified R. It could be, that it are modified MF. The camera pack is installed at the place, which originally was used by the GSha-23 gun and the ammo storage of the gun.

I do not mean to argue, but it does not seem likely that those were modifed MFs. They have the MiG-21R wing with the radio-electronic warfare wingtip pods. Also they have the MiG-21R tube installed on the right upper side of the nose with just an air pressure sensor, whereas the MiG-21MF has other sensors added on the same tube. Why would anyone downgrade by removing some useful sensors to convert a serial MiG-21MF into a MiG-21RF?

Some countries, Bulgaria included did have their own recon version of the MiG-21MF. Here it was labelled MiG-21MF-R and at the beginning it was planned to operate with the MiG-21R pods (after removal of the GSh-23L gunpod). That did not work out well, so later on, the MiG-21MF-R performed recon missions with a locally built small pod with camera, converted from a UB-16 rocket pod. That was the RFC-2 pod and shapewise it was something like this (this is just a shape, no skin):

 

[+FLOGGER23 3,063]

From Wikipedia: MiG-21RF (Izdeliye 94RA; NATO "Fishbed-H")

Egyptian designation for MiG-21R aircraft which had been locally modified by permanently mounting the cameras in a fairing under the nose.

 

16 or 18 planes were modified, the R11F2-300 turbojet, the pitot was moved to the right and no AoA vanes were present.

 

Look at the side air sensor, inherited from the PFM series

 

All R models were configured in this way

 

 

 

 

BUT and yes, a big BUT

 

Quoting Wikipedia again: MiG-21RF (Izdeliye 96R; NATO "Fishbed-H")

Not to be confused with the Egyptian local designation "MiG-21RF." This designation was used after some MiG-21Rs were upgraded with R13-300 engines as in the MiG-21MF.

 

So, this is a yes and a no on all previous statements and we will be more confused 

 

Now I will have another version to be made hahahahahahahahahaahhaha

 

Edited June 5 by FLOGGER23