How did the I-16 Really Perform in WWII?

[YavorD]

Really? I cited the pilot's manual for the I-16M-25 from 1937.

The I-16 equipped with the turbocharged M-62 exceeded a speed of 500 km/h in level flight.

What is the real meaning of the statement in the pilot manual? What, in practical terms, the pilot is supposed to do during a dive?
I can see the following options.
(1) throttle the engine, no full-power dive;
(2) decrease the dive angle; or
(3) terminate the dive and pull the control column to initiate transition to a level flight.
All the options impose several limit on the possibility to obtain a favourable position during a fighter-vs-fighter engagement.

Experimental aircraft with turbo-charged M-25V TK-1 and M-62 TK-1 engines went in excess of 500 km/h above 8500 metres, the performance at 3000 metres decreased in comparison with the speed and climb of production machines.

 

[YavorD]

A 1938 comparison between I-16 M-25V (type 10, 4 MG) and Messerschmitt Bf 109 D.

1938 : И-16 М-25В vs Bf 109 D (level speed)

1938 : И-16 М-25В vs Bf 109 D (climb)

I-16 M-25V have about 400 kg advantage in take off weight and 90 hp advantage in maximum power at rated altitude. The advantage is demonstrated in the rate of climb but the speed is already in favour of Bf 109 D, below 5000 meters at least.

 

[bf109xxl]

What is the real meaning of the statement in the pilot manual? What, in practical terms, the pilot is supposed to do during a dive?
I can see the following options.
(1) throttle the engine, no full-power dive;
(2) decrease the dive angle; or
(3) terminate the dive and pull the control column to initiate transition to a level flight.

Any of the above options, if it reduces speed and prevents the propeller from overspeeding.

All the options impose several limit on the possibility to obtain a favourable position during a fighter-vs-fighter engagement.

Sure. But the enemy usually has the same/similar limitations.

Experimental aircraft with turbo-charged M-25V TK-1 and M-62 TK-1 engines went in excess of 500 km/h above 8500 metres, the performance at 3000 metres decreased in comparison with the speed and climb of production machines.

The speed at low altitudes decreased due to the additional drag created by the turbocharger. At high altitudes, the speed of sound is lower than at low altitudes: the Mach number for the blade tips was even higher. Conclusion: the reduced efficiency of the propeller was not a decisive factor in the I-16's lack of speed.

 

[bf109xxl]

A 1938 comparison between I-16 M-25V (type 10, 4 MG) and Messerschmitt Bf 109 D.

View attachment 865704
1938 : И-16 М-25В vs Bf 109 D (level speed)

View attachment 865706
1938 : И-16 М-25В vs Bf 109 D (climb)

I-16 M-25V have about 400 kg advantage in take off weight and 90 hp advantage in maximum power at rated altitude. The advantage is demonstrated in the rate of climb but the speed is already in favour of Bf 109 D, below 5000 meters at least.

Sources?
I-16 M-25:

Source:

Bf 109 D

Source:

Comparison:

 

[YavorD]

Sure. But the enemy usually has the same/similar limitations.
...

I have no recollection for specific 1938 data, but for 1944 diving speed of Mach 0.75 ... 0.8 was not an exceptionally good achievement.

 

[bf109xxl]

I have no recollection for specific 1938 data, but for 1944 diving speed of Mach 0.75 ... 0.8 was not an exceptionally good achievement.

The I-16 Type 24 could exceed a speed of 600 km/h in a dive. Comparing aircraft from 1938 and 1944 is not serious.
The I-16 undoubtedly had insufficient propeller efficiency, but 1) this was partly due to the extremely unsuccessful design of the engine cowling, and 2) the contribution of the unsuccessful cowling, poor aerodynamics of the wing surface (fabric skin seams, warping of the aerodynamic profile, etc.) and losses of engine power due to poor manufacturing quality (including the carburetor) was cumulatively greater.

 

[YavorD]

Sources?
I-16 M-25:
View attachment 865778
Source:
View attachment 865779
Bf 109 D
View attachment 865780
Source:
View attachment 865781
Comparison:
View attachment 865782

I know the graph from the I-16 M-25 manual. From my point of view the graph is not applicable to I-16 type 10.
(1) The document in question is applicable to an early, pre-1937 variant, like I-16 type 5. See the weight tables, the values quoted are at least 200 kg less than 1700 kg plus values reported for 1938 production examples (1800 kg plus for gun-armed type 17).
(2) The maximum speed graph shows full throttle height of 2600 / 2700 metres - the altitude is correct for M-25 engine, quite low for M-25A, not for M-25V.
(3) The speed data from the I-16 manual (1937) correspond to an early lightweight aircraft with an enclosed cockpit, not an aircraft in combat trim.

The original source for the data in Your post is actually LDv. 556/2 Ausgabe 1938. This particular set of data is quite reliable, in my opinion, and my model is not far away from these values.

 

[bf109xxl]

I know the graph from the I-16 M-25 manual. From my point of view the graph is not applicable to I-16 type 10.

This is definitely a manual for the Type 5 with an M-25A motor. The difference in maximum speed compared to the I-16 type 10 was negligible.

(1) The document in question is applicable to an early, pre-1937 variant, like I-16 type 5. See the weight tables, the values quoted are at least 200 kg less than 1700 kg plus values reported for 1938 production examples (1800 kg plus for gun-armed type 17).

The I-16 type 5 was produced until the end of March 1938. The weight of production aircraft could vary. There were lightweight Type 10 prototypes weighing around 1,500 kg. Weight has no direct impact on maximum speed, and even its indirect impact is rather insignificant. Moreover, the I-16 type 10 had a higher rate of climb, which is really strange.

(2) The maximum speed graph shows full throttle height of 2600 / 2700 metres - the altitude is correct for M-25 engine, quite low for M-25A, not for M-25V.

From the book by Maslov:

(3) The speed data from the I-16 manual (1937) correspond to an early lightweight aircraft with an enclosed cockpit, not an aircraft in combat trim.

Most serial I-16 Type 5 aircraft were equipped with a sliding canopy. Only a few late-series aircraft (from September 1937) got a fixed windscreen.
The speed chart from the manual does not correspond to either the prototype data (No. 123954) or the lightened aircraft for the aerobatic team (No. 5210660). The speed at ground level is clearly overestimated, and at an altitude of 5000 m, it is clearly underestimated. It is possible that these are simple errors made when drawing the chart by hand. Below is a graph from the book "Aircraft Construction in the USSR" - perhaps this data is much closer to reality.

The climb rate chart is also rather strange - it does not correspond to the published test data for aircraft with the M-25 engine and is better suited to the I-16 type 4 with the M-22 engine. But this does not change the conclusion: both mass-produced I-16 types (5 and 10) significantly outperformed the Bf 109D in terms of rate of climb at practically the same maximum speed.
The inefficiency of the propeller was more pronounced on aircraft with M-62/M-63 engines, but nonetheless, the other factors remained more significant.

 

[YavorD]

This is definitely a manual for the Type 5 with an M-25A motor. The difference in maximum speed compared to the I-16 type 10 was negligible.
View attachment 865829

The I-16 type 5 was produced until the end of March 1938. The weight of production aircraft could vary. There were lightweight Type 10 prototypes weighing around 1,500 kg. Weight has no direct impact on maximum speed, and even its indirect impact is rather insignificant. Moreover, the I-16 type 10 had a higher rate of climb, which is really strange.

View attachment 865798
From the book by Maslov:
View attachment 865799

Most serial I-16 Type 5 aircraft were equipped with a sliding canopy. Only a few late-series aircraft (from September 1937) got a fixed windscreen.
The speed chart from the manual does not correspond to either the prototype data (No. 123954) or the lightened aircraft for the aerobatic team (No. 5210660). The speed at ground level is clearly overestimated, and at an altitude of 5000 m, it is clearly underestimated. It is possible that these are simple errors made when drawing the chart by hand. Below is a graph from the book "Aircraft Construction in the USSR" - perhaps this data is much closer to reality.
View attachment 865828
The climb rate chart is also rather strange - it does not correspond to the published test data for aircraft with the M-25 engine and is better suited to the I-16 type 4 with the M-22 engine. But this does not change the conclusion: both mass-produced I-16 types (5 and 10) significantly outperformed the Bf 109D in terms of rate of climb at practically the same maximum speed.
The inefficiency of the propeller was more pronounced on aircraft with M-62/M-63 engines, but nonetheless, the other factors remained more significant.

I will try to answer some of the points. My impression is we are using the same secondary source material but arriving at different conclusions.
Concerning engine variants.
(1) M-25 is rated 700 hp (metric) at 1950 rev/min at 2000 metres on a test bench.
(2) M-25A is rated 730 hp (metric) at 2100 rev/min at 2500 metres on a test bench. If the induction system is not unusually bad in dynamic pressure recovery at true air speed above 400 km/h, and conduit pressure loss is not excessive, and propeller adjustment is not too far off towards the coarse pitch, the full throttle height must be above 3000 metres. Maslov's table shows: 2700 m (type 5); 2400 m (type 12); 2800 (type 15 trainer). The only set which looks somewhat reasonable is for type 15 two-seater. Data sets for type 5 and type 12 indicate an engine which is close to M-25, not M-25A as specified.
(3) M-25V is rated 750 hp (metric) at 2100 rev/min at 2900 metres on a test bench. Data set in the Maslov's table for I-16 type 10 shows full-throttle height of 3160 metres. Somewhat low value. Data set for type 17 is something I can not explain. See also the data for I-15bis in the TsAGI graph - a full throttle height well above 3000 metres at lower maximum speed.
(4) If there is a problem in my model results, it is concerning M-25V engine mixture control above 7500 metres. There are reports about poor mixture control at higher altitudes but not enough data to confirm the severity of the performance loss above 7500 metres. The problem for M-25V is supposed to be solved during 1939/40 in parallel with the work on M-62/63 engines.

Concerning flight test data reported.
The TsAGI data set for I-16 type 10 is a bit optimistic in my opinion but not too far from reality. May be brand new and a bit polished example but the engine and propeller settings not particularly good. Also, there are statements about problems whit normalisation of flight test data at the military test establishment at the time. If I remember correctly, Polikarpov, as well as production plant manager, complained in front of higher authorities when test report for a two-seat fighter stated higher maximum speed above what was reported for the "production standard" I-16.

As a conclusion of this post, the I-16 type 10 was a capable fighter for 1938, albeit somewhat tricky to master. The I-16 problem is the aircraft was forced to serve beyond 1940 and later variants with more powerful engines does not show much of improvement.

P.S. My airframe aerodynamics model for the I-16 was originally based upon work published by Владимир Сергеевич Пышнов. The version used for this set of results (generated about two-three years ago) is actually quite close to the Пышнов data, although the engine and propulsion system model is somewhat different according to my own analysis of the engine and propeller data.

P.S.2. Пышнов В.С., "Из истории летательных аппаратов", 1968 г

 

[bf109xxl]

I will try to answer some of the points. My impression is we are using the same secondary source material but arriving at different conclusions.

I have yet to see a single fact that contradicts my conclusions.

(3) M-25V is rated 750 hp (metric) at 2100 rev/min at 2900 metres on a test bench. Data set in the Maslov's table for I-16 type 10 shows full-throttle height of 3160 metres. Somewhat low value. Data set for type 17 is something I can not explain. See also the data for I-15bis in the TsAGI graph - a full throttle height well above 3000 metres at lower maximum speed.

The I-15 had better designed air intakes, while the I-16 had significant pressure losses in the air ducts. Due to the ram air intake, the I-15 had slightly higher full throttle altitude.

(4) If there is a problem in my model results, it is concerning M-25V engine mixture control above 7500 metres. There are reports about poor mixture control at higher altitudes but not enough data to confirm the severity of the performance loss above 7500 metres. The problem for M-25V is supposed to be solved during 1939/40 in parallel with the work on M-62/63 engines.

I am interested rather not in graphs, but in the assumptions within the model. Please provide the equations of the relationships and parameters, then we can discuss the subject in detail. Without them, the graphs are of no value whatsoever.

Concerning flight test data reported.
The TsAGI data set for I-16 type 10 is a bit optimistic in my opinion but not too far from reality. May be brand new and a bit polished example but the engine and propeller settings not particularly good.

When installing a two-bladed fixed-pitch propeller instead of a three-bladed variable-pitch propeller on the I-16 with the M-25, no noticeable deterioration in performance was observed. A serious loss of speed only began when the M-63/M-63 was installed. But even in this case, the maximum speed exceeded 500 km/h, provided that the engine had sufficient power at altitude - it is clear that the propeller's inefficiency was not the main reason for the loss of speed. The large-diameter cowling with poor aerodynamics reduced the efficiency of the propeller in addition to the tip effects of the blades. By using plywood for only the upper wing skin, it was possible to increase the speed by 20 km/h!
The main difference that affected the test results was the quality of the engine—the factory did not provide the required quality stability due to the large proportion of manual adjustment for each engine.
If you are not prepared to assess the contribution of each factor separately, then further discussion does not make much sense.
I will only add that quite a few problems arose due to the ambitions of individual departments and the voluntarism of the party leadership, which were exacerbated by the insufficient educational level of the executive staff. The Air Force wanted one thing at first, then another, the designer sought a compromise and proposed a third, the factory was ready to produce the fourth, but wanted to produce the fifth... Internal relations between structures in the USSR are an extremely interesting topic, which most likely will remain poorly studied.

Also, there are statements about problems whit normalisation of flight test data at the military test establishment at the time. If I remember correctly, Polikarpov, as well as production plant manager, complained in front of higher authorities when test report for a two-seat fighter stated higher maximum speed above what was reported for the "production standard" I-16.

I would appreciate a quote - I guess this episode has simply vanished from my memory.

As a conclusion of this post, the I-16 type 10 was a capable fighter for 1938, albeit somewhat tricky to master. The I-16 problem is the aircraft was forced to serve beyond 1940 and later variants with more powerful engines does not show much of improvement.

The main problem with the I-16 was the technological weakness of the plant in Gorky, despite the great ambitions of the factory management and the chief designer (Pashinin). This was a case where the party leadership should have exerted more pressure, but for some reason this did not happen, and the factory was forgiven for its delays (in essence, sabotage) in improving the I-16.

P.S. My airframe aerodynamics model for the I-16 was originally based upon work published by Владимир Сергеевич Пышнов. The version used for this set of results (generated about two-three years ago) is actually quite close to the Пышнов data, although the engine and propulsion system model is somewhat different according to my own analysis of the engine and propeller data.

My understanding is that Pyshnov derives everything from the known drag curve. Then everything is clear - what is assumed is what is obtained.

 

[YavorD]

...

I would appreciate a quote - I guess this episode has simply vanished from my memory.
...

Ivanov, V. P. (2004) Chapter 14, pp. 236, 237.
A reference to the Polikarpov's private archive.

Иванов, Владимир Петрович (2004)
Самолеты Н. Н. Поликарпова
Русское авиационное общество (РУСАВИА), Москва, 2004, 432 с., формат 60x90/8, тираж 1500 экз.
ISBN 5900078256 / 9785900078250

 

[bf109xxl]

Ivanov, V. P. (2004) Chapter 14, pp. 236, 237.
A reference to the Polikarpov's private archive.

Thanks a lot, this is a great example of how well-organized the state apparatus was under Stalin!

 

[YavorD]

In order to complete 1938 "state of the art" picture there is a comparison between И-16 М-25В ВФШ and Bf 109 C (Jumo 210 G).

1938 : И-16 М-25В vs Bf 109 C (speed)

И-16 М-25В vs Bf 109 C (climb)

The fuel-injected Jumo 210 G engine got also a small enhancement in the second speed supercharger gear ratio, somewhat increasing full-throttle height, and power, in comparison with the Jumo 210 D engine. In this case I-16 M-25V demonstrated rate of climb advantage only at altitudes between between 1500 and 3500 metres.

Only 58 Bf 109 C-1 examples were produced, few converted to C-3 variant. Most of the Jumo 210 G engines produced were allocated to Bf 110 B airframes but even this series was not produced in large numbers. Both Bf 109 E and Bf 110 D switched to DB 601 A engines.

The Jumo 210 was one of the "small-size" V12 liquid-cooled engines at the end of 1930s, comparable to Hispano-Suiza 12 X and Rolls-Royce Kestrel. Junkers Motorenbau continued with larger Jumo 211 which powered Junkers 87 and Heinkel 111 bombers.

 

[YavorD]

Things changed a bit between 1938 and 1940. During the autumn of 1940 most numerous fighter aircraft in the Red Army Air Force (ВВС РККА) were И-16, И-153, И-15бис. A performance comparison between И-16 тип 29 (М-63, АВ-1) and Bf 109 Е-1 (DB 601 A) is shown.

1940 : И-16 М-63 vs Bf 109 E (speed)

1940 : И-16 М-63 vs Bf 109 E (climb)

The new M-62 and M-63 engines with a two-speed superchargers proved troublesome initially but throughout 1940 gradual improvements in the design and the manufacturing, as well as ground personnel and flying personnel training raised the service life between major overhauls to a respectable value of 100 to 150 flight hours.

 

[elbmc1969]

A 1938 comparison between I-16 M-25V (type 10, 4 MG) and Messerschmitt Bf 109 D.


1938 : И-16 М-25В vs Bf 109 D (level speed)

What are the dotted/dashed lines?

 

[YavorD]

What are the dotted/dashed lines?

The dotted / dashed lines below the bell-shaped curve show best climb speed. There are small fluctuations because the function is quite flat and I did not run the iterations to a very small threshold. Nevertheless, the effect of a +/- 5 km/h on the rate of climb is negligible.
Best regards,
Yavor

 

[fone]

Polikarpov was simply terribly unlucky - the I-180 crashes, which were actually caused either by test pilots' mistakes or manufacturing defects, undermined Stalin's trust in him.

Sorry to start this forum with criticism, but this is just the opinion of one biased historian. Unfortunately, the widespread biography of Polikarpov, written by Ivanov, tries to create the impression that drunk pilots, bad factory workers and political games of competitors are to blame for all Polikarpov's troubles.

It was a serious mistake to start production of the wooden LaGG.

In fact, the start of production of the LaGG-3 was completely logical. The war had started in Europe, and an all-wood fighter that saved scarce aluminum was not a bad idea.

It was necessary to preserve the technology and produce the I-180 of mixed construction despite all the problems with the engine, which had achieved acceptable characteristics by the end of 1939.

Unfortunately, the I-180 did not have any characteristics until the end of 1940 due to the fault of Polikarpov, who was very cool about any mass production. He chose from the three available I-180 variants the N21 plant variant (I-180 type 25) only in May 1940, while this variant had not yet passed any tests. Then, on July 30, 1940, the management of the N21 plant and Polikarpov adopted a resolution according to which the serial I-180 would be radically changed, starting with the 21st aircraft.

 

[bf109xxl]

Sorry to start this forum with criticism, but this is just the opinion of one biased historian.

Please name some unbiased historians. Do you consider Mikhail Maslov to be a biased historian as well? Nowadays it's very popular in Russia to justify any decision made by the Soviet leadership during the Stalin era.

Unfortunately, the widespread biography of Polikarpov, written by Ivanov, tries to create the impression that drunk pilots,

The book "Unknown Polikarpov" by Ivanov states something exact opposite - the author quotes Dmitry Tomashevich who said that Chkalov (for those unfamiliar with the name, he was the most famous pilot of that time in the USSR) would sometimes fly being drunk, but on the day of the I-180's maiden flight (and his last flight), he was sober. Chkalov simply ignored all instructions that took into account the possibility of engine failure - had he followed them, the crash would not happened.

bad factory workers and political games of competitors are to blame for all Polikarpov's troubles.

It was the management of Plant 21 that was bad, evidently sabotaging the introduction of the I-180 in favor of "their own" IP-21 (I-21) by Pashinin. Ivanov cites documents signed by Senior Military Representative Belousov, which state that, on the orders of the management of Plant No. 21, the most experienced workers were transferred from the I-180 to the I-21, resulting in extremely poor build quality of the I-180.

In fact, the start of production of the LaGG-3 was completely logical. The war had started in Europe, and an all-wood fighter that saved scarce aluminum as not a bad idea.

Oh, yes, it was very logical - to rely on the production of an aircraft that required imported materials (phenol formaldehyde resins) from... drumroll, please!... Germany! If there's one thing you can't accuse the Soviet leadership of, it's a surplus of logic. The idea of building a wooden fighter may not have been the stupidest one, but... not the LaGG, and not at Plant No. 21, where they had to nearly double the number of workers due to the switch to wooden construction techniques! For a wooden fighter (and the LaGG in particular), the M-105's power was clearly insufficient. The LaGG was brought up to an acceptable performance level by 1943 - and its main achievement was increasing the scores of German aces. Yes, the LaGG had some merits, and yes, there were pilots who could successfully fight German aces even in a LaGG, but... That wasn't enough. The aircraft gave inexperienced pilots too few opportunities to gain the necessary experience.

Unfortunately, the I-180 did not have any characteristics until the end of 1940

That is not true. The aircraft passed factory tests and was transferred to the Air Force Research Institute (NII VVS) for state tests, while serial production began before the state tests were completed - at that time, this was rather standard practice. There are quite convincing arguments that pilot Proshakov was to blame for the crash of the I-180 during tests at the Air Force Research Institute, rather than any design flaws. The performance characteristics obtained during factory tests in May 1940 (pilot Ulyakhin) satisfied the Air Force. In the spring of 1940, three I-180S aircraft were manufactured, which were considered production models. In July, one aircraft (No. 25213) was even sent to a combat regiment for weapons testing. The I-180's shortcomings were far less significant than those of the LaGG.

due to the fault of Polikarpov, who was very cool about any mass production.

That's not true either. Polikarpov consistently took the factory technologists' requirements into account and adapted the design to the factory's capabilities. For example, on the I-180-3, the wing spars retained a tube design instead of a more advanced (T-shaped) one, since the factory was unable to master the production of the new spars.

He chose from the three available I-180 variants the N21 plant variant (I-180 type 25) only in May 1940, while this variant had not yet passed any tests. Then, on July 30, 1940, the management of the N21 plant and Polikarpov adopted a resolution according to which the serial I-180 would be radically changed, starting with the 21st aircraft.

The major problem with the I-180 was its engine - the M-88 wasn't brought up to an acceptable condition until the fall of 1940. Even producing the Yaks at Plant No. 21 was more logical.