To be honest, I'm a little puzzled myself - the rpm of the M-87/-88 was only slightly higher than that of the M-62/-63, but the I-16 with the M-6X was equipped with AV-1 propellers with controllable pitch and wider blades (there were also versions with conventional, narrow blades). Either the threshold for matching propeller power/rpm lay precisely in this narrow range, or the Soviets simply did not want to waste effort on improving the I-16 when prototypes of more advanced fighters were already available. The I-16 received more powerful engines too late.
How did the I-16 Really Perform in WWII? (1 Viewer)
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Shortround6
Lieutenant General
Perhaps.
The engine/s in the XF2A-1 and F2A-1 were not geared but had 2 speed superchargers. They maxed out 2200rpm for take-off and 2100rpm "normal". There was no "military" rating at the time. What the customers (USN and Finns) did with them? Finns may have used the 2200rpm take-off rating as military power.
The engines used in the F2A-2/3 ran at 2500rpm T-O and at 2300rpm "normal" and the engines made 1200hp for T-0 instead of 950/1000hp and 900hp at 14,000ft instead of 750/800hp at 15,200/16,000ft. The last two split numbers are for the Finns using the 2200rpm read line.
The F2A-1 and 239s used a 9ft prop and the F2A-2/3 used 10ft 3in prop.
The engines in the F2A-2/3 were the 2nd generation after the engines in the F2A-1. Engines (G series) in the F2A-1/239 used aluminum crankcases. Engines in the Export Buffaloes were usually the G-100s with the 1st steel crankcase while the engines in the F2A-2/3 and last Dutch aircraft were the G200s with the 2nd steel crankcase. The crankshaft also used larger roller bearings and among other changes the supercharger was the first Wright design (older ones were at least part GE) with a new impeller and other changes.
Trying to go up 20-25% in power with an existing propeller was probably not going to work.
- True, the I-180-1 (И-180-1) was tested with a direct drive engine.
- The I-180-2 (И-180-2) is described in my sources as equipped with an M-87B (М-87Б) engine. There is no clear statement about propeller reduction ratio (or direct drive engine). The airframe empty weight is increased by 351 kg in comparison with the first prototype. The wing span and wing area does not change in comparison with the first prototype. The overall length is increased by 41 cm (gearbox?)
- The I-180-3 (И-180-3) is described in my sources as equipped with an M-88 (М-88) engine. The wing area is increased by about 10%. The overall length is very close to the second prototype. There is no clear statement about propeller reduction ratio (or direct drive engine) but on pictures the propeller diameter is larger, and reported performance gives an indication of a geared engine.
- Small series production (№ 25211, 25212, 25213 ...) is supposed to be equipped with a geared M-88 engine.
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No objection from my side, just I would like to stress the point the direct drive engine is waste of power - the F2A-1 propeller efficiency at 300 mph is decreasing towards 75 %, while geared engine of higher power is driving a larger propeller at 80% plus efficiency. Two years later NACA spent a lot of effort to give another 1 or 2 % advantage in propeller efficiency for turbo-charged P-47's.
Best regards,
Yavor
Shortround6
Lieutenant General
The F2A-1 engine was about 1100-115lbs and the Prop was 262lbs (?)
The f2A-2/3 engine was about 1315-1370lbs and prop was 339lbs (?)
everything was trade-off and on the older, lighter engine the reduction gear appears to be worth about 80lbs.
Likely with an under 1000hp engine they would not have needed a 340lb prop and something around 1/2 way in between would have worked?
Was the improvement in propeller efficiency worth it for the extra 120lbs (?) on the original 950/1000hp engine/prop?
I am not saying it didn't exist.
With higher powered engines and the higher hoped for speeds better propeller efficiency becomes more important.
Going back to the I-16 the best Soviet engine was roughly equal to the Wright R-1820 G100 used in the export Buffaloes. The more common M-62 engine was roughly equal to the engines in the F2A-1/239 and the M-25 engines were roughly equal to engines in the last American biplane fighters. Many of which had 3 bladed propellers but with both HS and Curtiss (electric variable pitch) competing for world markets the US was in the fore front of propeller technology and use.
USSR had to sometimes balance availability with desired performance.
Three bladed propellers are more costly than two bladed propellers.
If your country is short of propellers saving the 3 bladed props for the bombers and faster fighters makes sense.
I found information about problems with the M-63 in another source. During the tests, the efficiency of the AV-1 propeller with a diameter of 2.8 m was found to be insufficient at any blade pitch angle. Installing a different propeller (VISh-6V) only worsened the situation. In addition, the design of the engine air intake was considered unsuccessful - it did not allow for the effective use of ram air. In addition to its poor aerodynamics, the cowling did not provide the necessary thermal conditions - the engine got overheated before reaching maximum power. Moreover, the carburetor did not provide the required fuel mixture at altitudes above 7,500 m.
And one more thing. After all, the I-16 flew faster than 500 km/h. According to documents, during factory tests of the I-16 type 24 in December 1939, a speed of 500 km/h was exceeded at an altitude of 6000 m. It is not entirely clear what kind of modification it was, but most likely it was an experimental modification with turbochargers.
The USSR had always to balance availability with performance
Nevertheless, three-bladed propellers had already been mastered by industry.
I think everyone was expecting miracles from the "new types." And they didn't particularly want to deal with heat-stressed and unreliable engines.
Both the M-62 and M-63 demonstrated disappointingly low reliability on the I-16.
1) I have a reasonably good results for versions of И-16 М-25В ВФШ (fixed pitch, ground adjustable propeller), И-16 М-62 ВФШ (fixed pitch, ground adjustable propeller), И-16 М-62 (М-63) АВ-1 (in-flight variable pitch propeller). I can post my results if there is an interest. It may cost a few hours of work to convert the raw data into presentable format, and to provide a brief explanation about the model.
2) Agreed, the M-88 gear ratio was not optimal for a fighter, another version was necessary, as well as a different set of blades for the variable pitch propeller. No version of I-16 was able to meet the requirements stated for 1940. The latest versions of I-16 M-62/M-63 were not too far behind Messerschmitt Bf 109 D (Jumo 210 D) but there was an obvious disadvantage in comparison with Bf 109 E (DB 601 A).
3) Late versions of P-63A were not rejected, IMHO, when available, and where used against Japan if not much in Germany?
Best regards,
Yavor
P.S. Small edit language.
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Most probably, there were no P-63 operations against Germany if not to count the deployment to PVO (without encounters with LW). Maybe occasional recon flights in the last weeks.
Regarding the Far East, since this is I-16's thread... There were regiments that changed their I-16s for P-63s. What an upgrade!
As I understand it, these are estimates of propeller efficiency? That would certainly be interesting, but I'm afraid it's not enough - we need estimates of speed losses due to poor cowling and low-quality skin as well. It would be interesting to compare the contributions of each of these factors.
By the way, the well-known Polikarpov biographer V.Ivanov wrote about the insufficient efficiency of the I-16M-6X propeller in his book "The Unknown Polikarpov":
I can draw the following conclusions: losses due to the use of an unsuitable propeller were comparable to or even lower than losses due to insufficient aerodynamics (engine cowling, skin quality) and only occurred when installing an engine with increased power and speed.
There was no chance to fight on equal footing with the 109F, but there was a chance of keeping up with the 109E, and the latter accounted for a significant proportion of the fleet. However, this required reasonable decisions, which were highly unlikely due to the low quality of the leadership and the contradictions of the Soviet system. Most importantly, the technical factor was secondary to the organizational one, including pilot training and air combat tactics. The Yak-1, by the way, was not much more effective than the I-16 in the first months of the war.
I don't quite understand - the I-16 M-6X was practically equal to the "dora" in speed and significantly superior in rate of climb. The "dora" was rather a strange beast that did not stay in the Luftwaffe for long.
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I seem to have lost track and don't quite understand what the P-63 has to do with it, but they weren't used against Germany - they were kept in reserve regiments. They were used against Japan to a limited extent, mainly as attack aircraft - there was no enemy for them as fighters, although they were also used as escorts. And I agree with the opinion above: the Soviets realized that this was the only more or less effective air defense interceptor - according to the results of Soviet tests at an altitude of 7,500 m, it outperformed both the Spitfire IX and the La-7.
The 20th ShAP (Ground Attack Aviation Regiment) replaced its I-15bis with P-63s, becoming the 410th IAP (Fighter Aviation Regiment).
Shortround6
Lieutenant General
I believe the 109D was last used either Poland or perhaps Norway?
They were used as trainers for quite a while after that but were replaced by the 109Es in France.
Actual combat between 109Ds and I-16s would have been just about nonexistent.
Around 175 (?) surviving E-1s were converted to E-7s or last production E-1s converted.
I-16s would have been fighting E-3s at best.
They were used as trainers for quite a while after that but were replaced by the 109Es in France.
Actual combat between 109Ds and I-16s would have been just about nonexistent.
Around 175 (?) surviving E-1s were converted to E-7s or last production E-1s converted.
I-16s would have been fighting E-3s at best.
My current model does not have the complexity and refinement to estimate drag caused by various airframe components.
The model, in my opinion, provides reasonably good estimate of available thrust. The model can be tested against known engine performance data, propeller data, and flight test data of air speed, rate of climb, and crankshaft rotational speed.
There is more uncertainty concerning thrust required. The total drag is adjusted according to the recorded flight test data, so the estimation is quite reliable. For the relative merits of various aerodynamic improvements, however, a very different approach is necessary.
In a few words, the model is good in estimation of the available thrust (about +/- 5%) and can give an answer about the effect of moderate weight variation but the effect of minor aerodynamic improvements can not be estimated with the same accuracy without specific flight test data.
I am going to return to the performance comparison between I-16 M-62/63 and Bf 109 D/E sometime soon.
Finally, I mentioned P-63A Kingcobra because I can not agree there was no requirement for a high-performance fighter for the war over Europe (Germany) during 1944/45.
Then, I'm afraid this model won't be enough to draw conclusions. It's not that hard to estimate the loss of thrust due to the propeller when the aerodynamic drag coefficients are known
The selection of propeller parameters is described in detail here (pp.58-70):
How does your model differ from the one described in the brochure?
I would be interested in reading it.
I wasn't talking about aerial warfare in Europe, I was talking about aerial combat on the Eastern Front. Why were high-altitude fighters needed there, if bombers on both sides usually didn't fly above 5,000 meters? The altitude of aerial combat is determined by the operating altitude of bombers.
Poland.
I'm not sure about France - almost certainly
not, but I didn't look into it too much. According to some sources, the "doras" were used as night fighters in the Reich's air defense.An air combat between the I-16 and the 109D could well have taken place in Spain.
The approach used in my propulsion system model is not too different from the approach described in "Практические работы по курсу воздушных винтов" [Practical exercises (examples) concerning course on propellers - loose translation]. As there is no specific data on the propellers in question, I am using contemporary (late 1930s) NACA reports concerning two- or three-blade Clark Y section propellers (Hamilton Standard blades in this particular case). A family of curves for various pitch setting is arranged in a two dimensional tables with values for thrust and torque coefficient. The algorithm interpolates between data points and calculates thrust and torque coefficient as a function of advance ratio and pitch. Compressibility corrections are applied in a similar way as described in the brochure, the fine details can be slightly different. Practically, propeller efficiency is assumed to decrease in proportion to the ratio between tip Mach number and certain critical Mach number value, so the correction is MIN (1; Ma_cr / Ma, for Ma above Ma_crit).
That is too much a simplification for my taste. A 1944/45 bomber mission over Eastern and Central Europe must be planned with fighter cover not in close proximity of the bomber / attack formation but as a coordinated fighter sweep across the space and time of bomber formation flightpath, and top echelon of the fighter force should be considerably higher, e.g. 7/8000 metres.
P.S. Error in formula and word choice correction.
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By memory, a few Bf 109 D were found on British soil in 1940, although at the time most Bf 109 D should be transferred to training or night-defence units.Poland.
I'm not sure about France - almost certainly
An air combat between the I-16 and the 109D could well have taken place in Spain.
So which German or Soviet bombers flew in formation at altitudes of 7-8 km? The standard altitude for both German and Soviet bombers was 4500-5000 m; only a few German high-altitude reconnaissance aircraft flew higher. The Il-2 generally tried to fly as close to the ground as possible. There was no need for high-altitude fighters on the Eastern Front. High-altitude interceptors became a priority when relations between the allies became tense and the USSR realized its vulnerability to the B-29 (and even to the B-17/B-24/Lanc, I think).
Repeat. My point is protection on the flight path of a bomber formation assuming attacks from all direction and altitude. Bombers did fly at optimum altitude in case fighter protection is available. Shadowing bombers in close proximity is ineffective and dangerous for the fighters. I do not insist the best approach was implemented always but it must be known at the time.
Shortround6
Lieutenant General
Yes, you are quite right.
It would have been an M-25 powered I-16 fighter (?) vs a Jumo 210 powered 109 so an interesting match up from a design perspective.
I am not sure if any M-62 powered I-16s made it to Spain?
