How did the I-16 Really Perform in WWII?

Steamed_Banana said:

From the interviews, it seemed like they loathed the Hurricane. Golodnikov sure didn't rate it.

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This is true as well. I guess they had hoped that it would work, only to see that it wasn't for them. It's purpose in lend-lease helped though.

Steamed_Banana said:

Seemingly with A5M and Ki-27 too, not to mention Ki-43 needless to say.

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Yeah this definitely surprised me. The I-16 as a modern fighter struggling against fixed-landing gear aircraft was a surprise for me. I know that the Japanese types were very light, but still.

Airborne2001 said:

This is true as well. I guess they had hoped that it would work, only to see that it wasn't for them. It's purpose in lend-lease helped though.

Yeah this definitely surprised me. The I-16 as a modern fighter struggling against fixed-landing gear aircraft was a surprise for me. I know that the Japanese types were very light, but still.

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To be fair, Ki-27 was pretty challenging for a lot of Allied fighters early on ... it was a freakishly agile aircraft and fairly fast in spite of the fixed landing g
ear

Airborne2001 said:

Yeah this definitely surprised me. The I-16 as a modern fighter struggling against fixed-landing gear aircraft was a surprise for me. I know that the Japanese types were very light, but still.

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Polikarpov did not pay enough attention to the aerodynamics of the engine cowling until the I-180. Apparently, the unsuccessful design of the I-16 engine cowling was the main reason for its excessive aerodynamic drag. For example, the P-35 had 1.5 times less drag than the I-16.

bf109xxl said:

Polikarpov did not pay enough attention to the aerodynamics of the engine cowling until the I-180. Apparently, the unsuccessful design of the I-16 engine cowling was the main reason for its excessive aerodynamic drag. For example, the P-35 had 1.5 times less drag than the I-16.

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I generally figured this. I mean:

That is a lot of flat cowl area for air to hit, even with the big spinner.

Airborne2001 said:

That is a lot of flat cowl area for air to hit, even with the big spinner.

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This is not the only reason for the high drag. The maximum speed of the I-16 with plywood wing skin was higher than with fabric skin, the difference can be estimated at approximately 20 km/h.

bf109xxl said:

This is not the only reason for the high drag. The maximum speed of the I-16 with plywood wing skin was higher than with fabric skin, the difference can be estimated at approximately 20 km/h.

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Oh my! I did not know this, but it makes sense. Correct me if I'm wrong, but I believe it gets down to small details like how fabric is not (at least inherently) as smooth as something like wood.

All of this does explain why the I-180 ended up being a whole league ahead of the late model I-16s in speed given that the Tumansky M-88 wasn't all that much more powerful than the M-62/63.

Airborne2001 said:

That is a lot of flat cowl area for air to hit, even with the big spinner.

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That is a bit simplistic.

There is a whole bunch of other stuff going on. Yes they probably could have rounded off the edge of cowl a bit better. But Curtiss didn't do any better with the Cyclone powered Hawk 75s.

What Curtiss did do better was fairing the cowl into the fuselage a bit better, not having large gaps in the cowl to fuselage joint. Not having all those large holes for the exhaust pipes creating drag. What is often invisible is large changes in fuselage cross section, like from large diameter radial to skinny cockpit and sometimes just another foot or two of length can reduce the turbulence.

Streamlining radials was a lot harder than it looks. At high speed you only need about 10-15% of the air that is approaching the front of the fuselage to actually go through the cowling for cooling and the more air that can be routed around the cowling rather than through it is an advantage.
What is unseen is shown by photos in wind tunnels with smoke. Most radial engines actually develop a high pressure zone ahead of the engine that starts moving the air towards the sides of cowling before it actually gets there. Turns out the spinners actually don't do much of anything at high speed. In fact they sometimes do their best work on the ground, keeping warm air from flowing forward around the prop hub and mixing the with cool air a little further out on the blades. That and not having the totally round area of prop blade beating up the air

Airborne2001 said:

All of this does explain why the I-180 ended up being a whole league ahead of the late model I-16s in speed given that the Tumansky M-88 wasn't all that much more powerful than the M-62/63.

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It should be noted that the frontal projection area of the M-88 was approximately 12% smaller than that of the M-63.
Even with the M-87B engine, the maximum speed of the prototype I-180-2 reached 540 km/h.

The weirdest thing about I-16 and I-53 to me is the short stubby fuselage, which seemed to be a 1930s trend...

You don't suppose it was influenced by the Gee Bees, do you?

Another plane from the rain drop school of aerodynamics
and short fuselages have less wetted area.
Rudders are over rated.

Good thing it has fixed gear or the flying wires on the underside would have no place to be attached ...

GregP said:

You don't suppose it was influenced by the Gee Bees, do you?

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Actually, it's funny that you mention this because over on secretprojects.co.uk we've actually had discussions that proved that the I-16 had at least a little bit of influence from the Gee Bee. Sadly I can't find it at the moment, but there is a good picture that shows the evolutionary similarities of the types.

bf109xxl said:

It should be noted that the frontal projection area of the M-88 was approximately 12% smaller than that of the M-63.
Even with the M-87B engine, the maximum speed of the prototype I-180-2 reached 540 km/h.

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On the topic of better aerodynamics, I remembered this from secretprojects.co.uk:

There were two prototypes that tested better aerodynamics, which included the I-165 (I-16bis) and I-166.

First we have the I-165, which all I could find is the right side of this image (left side is the I-180):

The I-16bis replaced the fabric covering with stressed skin, and it had multiple changes to the aerodynamics of the fuselage, cowling, and spinner.

The I-166 had a NACA cowling and also cooling flaps. This was combined with a singular exhaust pipe as opposed to multiple separate ones.

(All info credits go to redstar72 on secretprojects.co.uk.)

The I-163-1 (initially simply the I-163) was prepared as a production standard in 1937. Externally, it resembled the standard Type 5, but was equipped with an M-25E high-altitude engine (710 hp at an altitude of 5000 m), landing flaps, a modified landing gear design, increased rudder area, and a mast antenna (a radio was supposed to be installed). In a lighter version with two wing-mounted ShKAS machine guns, the I-163's flight weight was about 1,600 kg. The required speed of 490 km/h at an altitude of 6,800 m was not achieved due to unstable engine performance. The improvements introduced on the I-163-1 could not be applied to the serial I-16 type 5.
The I-163-2 was equipped with larger landing flaps and an oil-pneumatic landing gear retraction system. Due to multiple defects, it never flew.
I-164-1 (the first with M-25V) — also known as I-16s (s="escort"), was equipped with two additional fuel tanks in the wings, which increased the fuel capacity to 500 kg and the range to 2,000 km. Initially, the I-164 was rejected due to poor manufacturing quality - serious improvement were necessary. Further tests were discontinued due to leaks in the fuel tanks built into the wing. Repairing the tanks without completely dismantling them proved impossible.
The I-164-2 was initially intended for installation of the M-62, then the M-88. The aircraft was not built.
The I-165-1 with the M-62 engine was also called the I-16bis (not the first with this designation), had additional wing tanks, a new wing with rigid skin (I am not sure, whether it was stressed skin), a modified fuselage shape and engine cowling, and oil-pneumatic retraction of the landing gear. After three flights, the engine had to be replaced. It was planned to install a new wing with a more modern profile and rigid (playwood) skin. Due to a large number of assembly defects, the aircraft was not allowed for further testing.
The I-165-2 was originally designed for the M-62, but assembly was halted in early 1938 when Polikarpov decided to redesign the aircraft for the M-88. This required too much time, so further development was discontinued - the modernization lost its relevance, since the I-180 was already ready.
The I-166 with the M-25V was built on the orders of TsAGI. The main difference from other I-16s was the engine cowling with adjustable cooling flaps, an exhaust manifold, and a front ring oil cooler. The flight weight was reduced to 1,383 kg.
Source:

It is clear that the low technological level of production did not allow for any improvements to be implemented. It is also worth noting the factory's lack of interest in manufacturing prototypes.

GregP said:

You don't suppose it was influenced by the Gee Bees, do you?

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I think it was part of the same trend, and maybe some prevailing concepts in aircraft design. You can see the influence in the Buffalo and the F3F / F4F series of fighters, the Curtiss SBC dive bomber and others.

Here is the radio control logical extrapolation of the Gee Bee.

Flies really well and maneuvers well, too. Has a good rudder, too.

That's a lot of extra rudder and rudder fin...

Models have to fly better than the full scale versions.

Tricky to recover from a spin with an RC controller...