firebarSo you are kind enough to explain, how that does differ in AB-thrust?!
The nozzle-system aside.
In dry power, TF has much less exhaust gas velocity than TJ. The more by-pass ratio the less gas velocity.
In order to have reasonable gas velocuty, the TF must have much, much higher TIT.
In AB, the TF is limited by its compressor which runs at a far higher static pressure than the compressor of pure TJ, and at about 2 Mach, it usualy comes to its limit speed.
The compressor’s ram pressure multiplies with static pressure, and at about 2 Mach it is too much for higher pressure TF.
That is why the F-22 has no more than 2 Mach max speed, and probably less. Its compressor static pressure is very high and that is good for SFC, but it also has a bad inflence on max speed.
At 2 Mach, its engine compressors are on the verge of stall.
firebarRussian stuff better than you think.
I mean generally.
Of course, there are Russian engines which has outstanding SFC, like Lotarev 3 shaft TF, etc.
firebarAll the fancy claims from different sides aside. As you wrote, supercruise capability has nothing to t-w-ratio, but much more with drag-t-ratio. Supersonic airflow differs from subsonic airflow considerably. At supersonic speed, most of the effective thrust from an engine comes from the inlet-system and the nozzle-system . The main difference between TF and TJ is noticeable in two areas. Above Mach 0,8 and at height the old higher by-pass engine were at a disadvantage in dry thrust related to TJ, but not in AB when it comes to thrust only. But with a sfc above 2 those TF were not very economical in AB too, compared to the much cheaper to built TJ.
The example of the MiG-31 and its D-30F-6 TFs showed, that modern TFs are no longer at a disadvantage any longer from the 70s/80s. State of the art TFs are adjustable about by-pass-ratios via digital controls. The customer and his demanded mission-profiles will select the ratio.The transonic range from Mach 0,8 till Mach 1,2 shows a rise in wave-drag.
To keep it as low as possible the designers were looking for the smallest possible wing-profil and the smallest possible frontal area. In dry thrust the output of an engine drops with air-densety = height.
TJ 5000 kp dry at sea level drops to ~ 1250 kp dry at 40000 feet. What does not matter much because the subsonic drag drops in a similar way. So piston engine fighters used turbo-compression to reach a higher air-pressure within the engine and related power-output up to height.
Equipped with an AB the wet-thrust did not drop in a similar way.
7000 kp wet at sea level drops to ~ 3500 kp wet at 40000 feet. Here comes the extra power in need to overcome the transonic drag-wave.
TF (0,5 ratio) 5000 kp dry at sea level drops to ~ 1250 kp dry at 40000 feet till Mach 0,8. In the transonic range that dry thrust drops further, because the cold thrust from bypath did not add power any longer, the hot thrust from the engine was left only. Going into burner the surplus cold allows a higher AB ratio. At sea level the TF has ~ 8000 kp and ~ 4000 kp at height, but all that with a higher debit in sfc.
We keep in mind that the true-superonic drag drops after Mach 1,2. “The fighter is over the hill and can accellerate further or trottle back in burner.
All that things are just some basics for basic understandings. In the transonic range there is not a constant rise in drag and every aircraft/fighter has his sweet spots, for the abonded ‘Sonicliner’ those were at Mach 0,98 and Mach 1,02 at height f.e. But all that showed, why the AB was the preferred tool for supersonic flight at first.
Producer and public-relation-people did a lot to confuse the readers further.
Because it looks much better, the nominal thrust is given sometimes. It is a mathematical thrust to compare engines. Speed*thrust, frontal inlet-area and true airpressure ignored related to sea level. Under such conditions a simple TJ produces several tenthousand of hp.
You forgot the main figure: the exhaust gas velocity.
firebarFirebar wants to act like American anything is inferior to Russian everything. Over G wants to act like American anything is inferior to everything period. …
No,no. You simplify things.
The Russians are better in some ways and Americans in some other way.
For example, the American engines generally has better SFC.
firebarFirebar wants to act like American engines are inferior to Russian ones so I called him out on it.
It is well known that american engines are better concerning fuel consumption, but that is all.
The fact is that the west jet engineers pay to much attention to fuel consumption in expense of jet engine controllability at disturbed airflow conditions or at high speed.
See R-35 of MiG-23. It can propel it to amasing 2,35 Mach with 2 large underwing missiles.
All west’s jet engines would stall at such condition.
firebarSens i’m well aware of that,and how limited(to airshows mainly) is this.The thing is that JFrazier say that russians lack engine with “the envelope of the F119’s”.
Correct me if i’m wrong but isn’t supercruise determinant by T/W ratio with engine in dry trust?So for exampe Al-31FM equiped Yak-130( 😉 ) will be capable of supercruise.And this fictional plane will be with 0 km/h to 1.7 M flight envelope?Russians lack high trust engine for fighters….nothing new.Back to reality P-42(Su-27 record plane)is capable of supercruise and high alfa numbers.Can i say that R-32 is better than F119?No,F119 is superior to any present russian engine,but your statement is just anti-russian BS.The thing that impress me in F119 is different.You can see in this post by Vortex:
“i’ve heard that the F-104 can reach ~M1.05 without the use of AB..guys, you gotta keep in mind that the TYPE of engine also matters a lot….most turbojets should be able to achieve supercruise for a decently designed supersonic fighter, but for turbofans to achieve supercruise means that the aircraft design needs considerable effort. The reason is that the exhaust velocities of turbojets are usually much higher (equating to more thrust at that flight speed) than turbofans. That said, it’s not surprising that Mig25s can supercurise (probably at above 50kft and ~M1.2 without AB). But the importance for the F22 here is the fact that it’s a turbofan that’s doing supercruise (ok, actually a very very low bypass turbofan)…meaning that it’s endurance in every corner of the flight envelope is better than any aircraft out there.”
The BAC Lightning was able to cruise at 1,2 Mach in dry power and TU-144 with NK-144 turbofan engines cruised at 1,8 Mach in dry power.
firebarThat’s not what I mean by performance envelope. Again, the envelope of the F119’s is much larger than any Russian engine right now. Those engines may be able to go to 90 degrees alhpha but can they supercruise at Mach 1.7? No. To me, going Mach 1.7 and doing a sustained 60 degrees alpha is better than a Mach .9 cruise speed and going to an instantaneous 120+ degrees alpha.
The 2,35 Mach cruise of Mig-25 or Mig-31 is even better.
firebarI dont know why. Max speed is not that important. If its more than 1.8 its enough and the F-22 certainly does more than 1.8.
The speed is very important for a fighter interceptor. That is why the F-15 is the best west’s fighter.
If it was not true, the Harrier would be the best.
But it lacks speed.
The speed also means acceleration. Another very important figure.
During testing with the YF-22, it achieved 1.43 with F119 and 1.58 with F120 engines. That doesnt mean the F-22 has the same limits. Im pretty sure the engines have seen some improvements during the last decade which made the Raptor faster despite the aerodynamic changes. You also forgot the canopy, which is much flatter than with the YF-22.
And weight of the missing operational equipment is negligible because the drag/thrust ratio is important.
The service version is actually much draggier than prototype.
It has more wingspan and less wing sweep, which both largely affects speed.
Also prototype’s nose was much less draggy and more pointed.
Aerodynamics can not be overlooked.
Not to speak of much higher weight of service version.
The prototype achieved that speeds without any operational equipment !!!
The F-22 would be the first airplane in history which can achieve more speed in service than in prototype conditions !!!
firebarAnd he’s probably got TF-30s stuck on the brain. The F110 has always been very good. And the F404 and F414 as well. Haven’t heard of the newer F100s having any issues.
No, I do not hear of any west jet engine able to cross 60 degrees AoA, I mean in service.
I will be glad to see some west fighter doing Tail slide at low altitude at airshows.
firebarThe Mig-23 is not a high AOA capable aircraft.
The manual says it can achieve more than 35 degrees AoA.
That is very good for that generation.
Note that Mirage 3 or Kfir are limited to 22 degrees.
firebarThe Super Hornet is cleared for up 55 degrees alpha I believe. The Raptor can cruise at Mach 1.7 but the engines are also fine down to 0 knots or 60 degrees alpha. No Russian engine has that type of flexibility or performance envelope right now.
The RD-33 of Mig-29 is cleared to 90 degrees AoA at zero airspeed.
See Tail slide or Cobra meneuver.
We have yet to see a west fighter able to do that, regularly, with service version.
firebarI’ve seen different figures. Its Mach 1.72 and the engines were still below 100%. Thats according to a Flug Revue article.
Top speed is unknown, but its likely limited due to ram overheating.
Did you ever ask yourself why its max speed is kept secret ?
Regarding its dry speed, we can read 10 different figures in 10 different sources !!!
The fact is that during testing the F-22 never achieved more than 1,5 Mach, and that was without operational equipment, with smaller wing span and with greater wing sweep than operational version has.
The YF-23 has been faster, in dry power, than YF-22.
firebarA value of the MiG-25:
-“The existence of the MiG-25 strongly influenced a national political decision not to overfly the Soviet Union with the SR-71 .
Through MiG-25, the Russians caused us to deny ourselfs vast amounts of intelligence which could be gathered by no means other than overflights.”
General Keegan, chief of USAF intelligence, -MIG PILOT, John Barron, page 185
firebarFor those who do not know which are the speed and ceiling of Mig-25 are:
Air Forces Monthly, June 2005: (page 19)
-” Indian Foxbat, with a max speed of 3,2 Mach and ceiling of 88.600 ft ( 27.000 m), has been an invaluable reconnaissance aircraft.”
firebarAir Forces Monthly, June 2005: (page 14)
-“An F/A-22 accident occured recently, because of flight control defficiency which allowed the aircraft to exceed its AoA and G limits which overstress the airframe.
The flight control was lost when the F/A-22 crossed the wake vortex of an F-16.”
That is a good example of what should not happen with a new generation fighter.
It would not have happened if it had not been limited to 60 degrees AoA.
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