The third generation of fighter jets represented by F-15A/F-16A in the West shocked the Soviet Union with their crushing performance advantages in several local conflicts in the 1980s. Prior to the decryption of the flight manuals and test reports of the third-generation fighter jets such as F-15A/F-16A/Garre in the West, the Soviet Union wanted to know the general performance of its opponents, and at the same time, in order to write teaching materials for its fighter pilots. Several opponents’ tactics and strategies were entrusted to several domestic institutions (mainly the Central Fluid Research Institute, TsAGI) to estimate the performance of several Western aircraft using classic engineering methods, and the results of the Su-27 flight test were carried out. Compared. Many years later, the United States published the F-16 AGARD-242 test flight report. The data source of this article is the above data. By comparing the estimated value of the Soviet Union with the measured value of the United States, we can know the accuracy of the Soviet Union's estimation of the opponent's performance and the technical/non-technical factors behind these errors.
The cover of the report comparing the data of the Su-27 and the three western models (F-15/F-16/"Guangfeng" F2). The performance of the Su-27 is taken from the flight test results, and the performance of the Western aircraft is estimated by the Soviet agency
F-16. The result of the AGARD-242 flight test is an important basis for my country to evaluate the performance of the F-16. The four aircraft in the
TsAGI comparison report are based on the ideal configuration of no-load light oil (or with up to two fighting bombs) as the benchmark. The weight of the Su-27 air combat flight is set at 18,920 kg. The weight of the F-16A air combat flight is set at 9,200 kg. This data better reflects the weight characteristics of the original Su-27 model Su-27B (because it has reached its end of life, it was fully retired before 2005). To put it aside, the current Su-27 single-seat benchmark model on Sukhoi’s official website has risen to about 17,200 kg in empty weight, so the 18920 kg in this article can only reflect its extremely light load oil (about 1800 Kg). The F-16A's flight weight of 9,200 kilograms is basically the same as the combat weight of the F-16MLU's half-oil (1550 kilograms) with two bombs, which is heavily equipped by the US allies. When our country uses the F-16 AGARD-242 flight test report for performance evaluation, it also uses almost the same flight weight. The full afterburner fuel consumption of two AL-31Fs is more than twice that of one F100. In other words, the comparison conditions in this article are extremely beneficial to Su-27: Su-27 only needs to carry fuel that can support a full afterburner for about 2.2 minutes, while the fuel carried by F-16 can support a full afterburner for about 4.3 minutes. .
Su-27 single-seater basic type Sukhoi official website original data. The screenshot was taken in 2009. The weight has increased
The scope of comparison in this article
Statement: This article only compares maneuvering flight performance, does not compare thrust-to-weight ratio, wing load, etc. Because thrust-to-weight ratio and wing load are not flight performance, only turning, acceleration, climb, etc. are called flight performance.
This article focuses on comparing the following performances: sea level straight flight SEP, sea level 4-7G overload upturn maneuver SEP, transonic maximum maneuver overload, sea level 0.7 Mach continuous maneuver overload, 5000 meters altitude 0.9 Mach continuous maneuver overload.
Term explanation: SEP and climb rate
climb rate is calculated as speed*sin (climb angle), which is the vertical component of speed, where the definition of climb angle is: when rising at this angle, thrust = drag + gravity axis The directional component, that is, the longitudinal force of the aircraft should be balanced and cannot be decelerated due to insufficient thrust. In other words, assuming that atmospheric conditions do not change with altitude (for example, density and oxygen content do not decay as altitude rises), then the aircraft should be able to maintain this rate of increase without slowing down. It is not difficult to see that the "rise rate" that was suddenly pulled up during level flight is not the rate of climb. This is a mistake that many amateurs and even some aviation professionals make easily.
SEP is an abbreviation for specific excess power. The calculation method is (thrust-resistance)*speed/gravity.
Many books and periodicals often emphasize a theorem: SEP=Climb rate.It is a mathematical coincidence, and it needs to be restricted to be true. If the reader has a mathematical foundation in middle school and lists the force balance equation of the aircraft axis, it is not difficult to prove that SEP is exactly equal to the rate of climb. But there is one exception: if the thrust of the aircraft is so large that it cannot achieve force balance even when it rises vertically, that is, it can accelerate when it rises vertically, then the SEP at this time is not equal to the rate of climb, and it loses the physical Intuitive, but it can still be used as an indicator of vertical mobility. The higher the value, the faster and agile maneuvers in vertical planes, and the less energy loss. This is why in the data chart of some aircraft, when flying at 280 m/s, its SEP can exceed 280 m/s, which is intuitively difficult to understand. The meaning is that it can accelerate when doing a vertical climb at 280 m/s, which has exceeded the scope of the traditional climb rate. For this reason, SEP has been an important vertical mobility indicator for decades. The above is the "narrow SEP", that is, the SEP in straight flight. There is also a "generalized SEP", which allows the aircraft to calculate the SEP while turning (this algorithm was initiated by the Soviet Union), which can well characterize its vertical maneuvering performance such as ascending turns, somersaults, and Yin Maiman slewing. This article will compare narrow and broad SEPs at the same time.
F-16 Soviet estimated value vs F-16 measured value vs Su-27 measured value
Transonic maximum overload:
F-16 Soviet estimated value: 7.33G, F-16 measured value: 9G+, Su-27 measured value: 7.5G
Maximum speed at sea level:
F-16 Soviet estimated value: 1400km/k (1.14 Mach), F-16 measured value: 1.2 Mach (there is still a strong acceleration trend, due to other factors is artificially limited), Su-27 measured value: 1400km/h (Mach 1.14)
In order to make the results more convincing, I deliberately selected the F-16 full fuel test data vs the Soviet Union's half fuel estimate data for the F-16, as far as possible against the F-16.
The Soviet Union’s estimates of the maximum low-altitude speed and the instantaneous overload at transonic speeds are very error-prone.
This picture was declassified and shocked Russia. In the Soviet Union, it is estimated that the F-16 can only use 7.33G above Mach 0.85. However, the F-16 in the picture is clearly pulled to 9.5G at Mach 0.87. This picture comes from the evasive maneuver after the bombing of the reactor in the Israeli Air Force's "Operation Opera". It shows the performance of the F-16 in actual combat. It is very gold content
continuous turning overload
sea level 0.7 Mach:
F-16A Soviet estimate: 7.5 G, F-16A measured value: 9G (strength limit), Su-27 measured value: 8.5G (strength limit).
5000m 0.9 Mach:
F-16A Soviet estimate: 6G, F-16A measured value: 7G, Su-27 measured value: 6.7G. Extended reading: F-16C-block50 can reach 7.45G under the same conditions, and MiG-29A is 6.6G.
The Soviet Union's estimated F-16A continuous turning overload envelope, and the F-16A continuous turning overload envelope obtained from the AGARD-242 flight test report. Compare
sea level straight line SEP (normal overload Ny=1)
F-16A Soviet estimate : 245m/s, F-16A measured value: 343m/s, Su-27 measured value: 310m/s. The estimation error of this performance of
has been so large that it is difficult to look directly at
sea level rise turning SEP (normal overload Ny>1, the greater the turning, the more severe the turning)
has not been found in the F-16A manual (only Full fuel data), but it is in the manual of F-16C-block50, and the condition is that the light fuel is empty, which just meets the requirements. Note that the format of the chart is not much the same as that of the Soviet Union, so the author added some arrows and instructions to facilitate readers' understanding.
The Soviet Union only estimated the relevant data of Ny=3 and Ny=5 of the F-16, and believed that the test results of the Su-27 were sufficient to ensure an advantage of 70-90 m/s. The detailed test number of Ny=4~7 is given in the
F-16C-block50 manualaccording to. The result is surprising: when Ny=4.2, it is 75 meters/second higher than the Su-27's Ny=3 data. When Ny=6.5, it is 50 meters/second higher than the data of Su-27 Ny=5, and it is 15 meters/second higher than the data of Su-27 Ny=3. The F-16 can maintain a SEP of 366 m/s in a 4.2G ascending turn, which not only greatly exceeds the Su-27's straight-up SEP amplitude of 56 m/s, but is also higher than the MiG-29's straight-up SEP 21 Meters per second. In layman's terms, the F-16 can still maintain a higher ascent rate in more severe sharp turns. There is even a peculiar phenomenon that the upward turn is much faster than the opponent's straight up. The Soviet Union directly underestimated the performance of the F-16 by 1/3-1/2, close to the level of the second-generation aircraft.
is even more underestimated. Pulling more drastic turns and maintaining a higher SEP, such a big advantage, was estimated by the Soviet Union to be the level of the second-generation aircraft.
Conclusion The classic engineering method of
is used to estimate the performance of piston-propeller fighters with acceptable accuracy, but for modern fighters that use a large number of static instability and vortex lift designs, a small amount of input error may be amplified by various nonlinear effects, leading to estimation The result has a large deviation. Similar underestimation problems of
exist not only in F-16, but also in F-15, but to a lesser degree. The F-15's instantaneous circling performance, low-speed flight performance and SEP values of various maneuver overloads are all underestimated. You can consider writing another article in the future. An interesting phenomenon is that the F-16A performance data estimated by TsAGI is quite close to the actual data of the F-16/79.
