MiG-3 evolution
Latest update on November 4, 2005                                            file name: latemig-3.html
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Modifications to the MiG-3 series

Aircrafts built during the spring were 30 km/h slower than the initial production aircrafts, this partly due to hurry in production leading to rough surfaces, partly to the presence of underwing gun pods, introduced in February.
Many defects were noted during operative use, alongside the already known weak armament, tendency to spin, longitudinal instability and high landing speed:

The MiG-3 was conceived as an high altitude fighter, but its fuel pump was not suited for it, starving the engine even at 5,000 m altitude.
An attempted interception of an high-altitude German reconaissance plane was made by three MiGs of 31th IAP, based at the Kaunas airport in Lithuania, on April 10, 1941, before the official beginning of the war. It was a failure, because all three interceptors entered into spin during the combat and were lost, killing one pilot.
Pilot engineer A.Kochetkov went to Kaunas to investigate; he found that the pilot's training was insufficient, particularly for high altitude operations, so he organized some tests, and discovered that, if well piloted, the aircraft was able to make combat turns without spinning up to an altitude of 10,500 m.
He recomanded retrofitting an automatic mixture control on the carburetor, modifying the oil and fuel pumps to avoid loss of pressure at high altitude, and to install reliable oxygen equipment.
These recomandations were soon implemented, and pilots of 4th IAP and 55th IAP, based near the Romanian border, shot down three hostile aircrafts.
Pilots of this unit were helped in training by test pilots.
At the beginning, these units had both old fighters (I-153s, I-16s) and MiG-3s. None wanted to fly the MiG, until the test pilot P. Stefanovsky made some demonstrations of flight that changed the mind of the pilots, who then started to train to the new machine.
The 55th IAP was the unit of the future top ace A. Pokryshkin, that was impressed by the new fighter, particularly for its capability in vertical manoeuvres.

The request for a 1000 km range penalized the MiG-3 and LaGG-3, increasing their weight; on the contrary, the Yak-1 never satisfied it, so its flight charachteristics were not impeded by extra weight. In 1941, the only fighter from the Yakovlev OKB that conformed to it was the I-30, that remained as only a prototype.
On May 10, 1941, the ventral tank was reduced from 250 l to 140 l to save weight. Tests on aircraft n. 2859 (with 5 guns) showed that this lightening improved takeoff, landing, turning and horizontal stability; the time of turn was reduced by 2-3 s.
 
On July 10, 1941, automatic slats were introduced, noticeably improving the flight characteristics with regards to spinning. 
The introduction of slats led to moving the pitot probe from the right wing edge to the lower right wing surface.
In the seconf half of 1941 the engine gear reduction ratio changed from 0.902 to 0.732, and this was associated with a new AV-5L-123 propeller instead of VISh-22E; the new propeller blades had a pitch angle range of  30° instead of  20°. They are not distinguishable in photos.
Late MiG-3s could have both gear ratios; the installed one was painted on the cowling side to avoid mistakes while mounting the propeller. 
(left)

An armoured glass was installed internally to the windshield. 
It is difficult to recognize on photos, so it is difficult to determine this was common. 
(right)

On some examples, a system to fill tanks with inert gas was installed; this is recognizable from a small pipe taking exhaust gases from the 2nd and 3rd left exhaust stacks.
The purpose of this system was to exclude air in the tanks, reducing oxigen on them with obvious safety benefits.
This system, although required by early test pilots since 1940, was frequently installed on examples built in summer 1941 and later.

On April 12, 1941, the order NKAP n.322 ordered to increase the daily production of MiG-3 to 20 examples, starting from August; this increased the projected output of MiG-3s during 1941 to 4295 aircrafts.
 
In May 1941, the control surfaces were modified by increasing to 26% of the aileron compensation, and modifying horizontal tail assembly with a smaller stabilizer (63% of total area) and enlarged elevator (37% of total area).
These modifies were tested on 5 examples (nr.3205, 3211, 3214, 3120 and 3169) and approved, but the war prevented their implementation on series aircrafts.

 


The late type MiG-3 appears

The engine cowling with dzus locks was considered unsatisfactory and too complex by first line units; according to this, a new cowling inspired to that of Bf-109 was tested at first on the aircraft n.2554, and then introduced into series production from the 16th series (each series was usually composed of 100 aircrafts, so the new cowling should be installed from the aircraft n.3600).

Visible modifications between typical early MiG-3 and typical late MiG-3 were:
  • the different scomposition of the engine cowling, particularly the upper part that became in one piece and locked with lever locks instead of Dzud locks;
  • the new cowling had two longitudinal fairings for lateral gun barrels; this allowed to replace the side ShKAS with larger guns as UBS or ShVAK without alteration of the external paneling (this modify of armament was made on few late examples only);

Left: early type (early characteristics marked with light blue). 


 

Right, late type (late characteristics marked with pink).

  • the addition of small horizontal triangular plates on the oil coolers outlet to improve aereodynamicity when shutter is in open position;
  • the modify of exhaust stacks, that received a typical fairing covering almost completely the first stack, and upper and lower plate lips;
  • the introduction of a gap behind the stacks; this was due to the moving back of the cowling border to improve the access to the engine, but can give the impression that the aircraft was lenghtened, so the late MiG-3 is sometimes erroneously called "long-nosed", "leghtened" or "MiG-3 UD"; in reality, the total lenght remained 8250 mm;
  • the side plates behind the engine were shortened, and the grilles on them were suppressed;
  • the introduction of fully closed and bulged doors for tail wheel.
Automatic shutters were introduced in the supercharger intakes on the wing roots to avoid dust ingestion; they were actioned by the undercarriage retraction and extraction.  (left)
On the earlier aircrafts, only a grille prevents foreign matter ingestion. (right)

On many later examples, forthemost observed during winter 1941/42, the tail wheel was fixed in lower position, while the doors were removed and replaced by a canvas cover; it is not clear if this was made in the factory or on the field.

The horizontal stabilizators were modified, apparently enlarging their chord at the tip.

 
On some late examples, a starter tooth was introduced, protruding from the spinner point; differently than on other aircrafts, no any macroscopic step or slot is visible between spinner and tooth.


Modifying the armament

During the summer 1941, tests were made on many armament combinations:

Then, from September 20, Zavod 1 produced 315 MiG-3s armed with two 12,7 mm UBS guns with 700 rounds each; of these, 215 examples were armed with two ZROB-82 underwing batteries with 3 ROS-82 rockets each.
Further previously-built examples were refitted with rocket launchers too.
Studies for arming the MiG-3s with a 2 gun armament were made frome the end of 1940, and the 23 mm ShVAK gun was identified as the most apt; but, due to the war, it was not possible to install such armament in 1940. The last 52 examples, built in Kuibyshev and in Moscow, were armed with a couple of ShVAK.
 

This interesting perspective shows the example n. 5015 produced on late 1941, armed by two machine guns UBS and two built-in batteries of ZROB-82 for the shooting rocket projectiles ROS -82.

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