I measured with a ruler (:-D) and it’s about 24 AoA, which corresponds to the SK version, which says 24 is the recommended AoA limit. The picture shows that up to this AoA Su 27 is stable and above it is not. If implemented in a WT game, how many people would fall into a spin… it would be a crying session… :D
That’s not to say that the real Su 27 is exactly dangerous above 24AoA, but it’s not for the average Su 27 pilot of the 80s and 90s. Flying above the AoA limit is for the better pilot.
Sukhoi Su-27/30/33/35/37 Flanker series & Su-34 Fullback - History, Design, Performance & Dissection
Because it’s a Delta wing. The strakes would logically be placed on top. That is where airflow separation occurs at angles of attack beyond lift… Why would they be placed at the bottom??
The Mirage 2000 was only mentioned because it has vortex generators at the intakes. it is the same technological concept..
The Su-27s fuselage & elevators are located below the wing. That is why the strake was placed there.
The strake is situated in the optimal position so when the aircraft pitches up only then do the strake begin to produce vortices that travel along the fuselage that is specifically designed to channel airflow into two paths. The Elevators & aft fuselage. Between these two channels is another strake only few who actually appreciate the Flanker’s aerodynamic traits & know why it is special.
Vortices/energized air flow is represented in orange. NOTE: Vortices stay attached to the surfaces of aircraft, that is why they vorticity is utilized in alpha flight technology.
Regarding additional strake. This strake is called a Ventral Strake (belly) or Ventral fin.
You most likely understand it as simply as stabilizer. For NATO aircraft, yes. However ventral fins can be designed for both. Stability & vortex generation. This is something the Flanker has that the Mig-29 does not. This is also why the Fulcrum can only cobra Its elevators cannot pitch the aircraft in to the same degree or speed of the Flanker. Even though it has a much higher thrust to weight & substantially lighter.
The ventral fins traditionally serve as a vertical stabilization substitute when an aircraft is operating at angles of attack where the vertical stabilizer is shielded from sufficient airflow by the aircraft’s fuselage & wings the aircraft will begin to yaw uncontrollably. They are added in specifically on the center fuselage of aircraft like the F-16 to prevent unintentional yaw@ higher angles of attack.
The Su-27 does not have this problem, nor does it need any yaw stability. It has the tallest foreword positioned vertical stabilizer, rudders & LERX. They are massive for this exact reason & they can very well still yaw at angles of attack beyond 90 degrees.
The ventral strakes of the Su-27 are unique. They are primarily vortex generators. They are the largest & is the only design in which the elevators are actually attached to it. All vortices generated are immediately caught in the elevators.
The Su-27 ventral strakes directly fed by constant airflow of the Su-27s fuselage channels shown above. The ventral strake produces very little vortices in pitch alone. That is why the RWR receiver was fashioned into the aerodynamic shape & pattern of standard vortex generating stakes. a Nacelle strakes. The RuF likely easily decided that it was not necessary once the RWR was upgraded. It would be a such a small variation in performance in an exclusive flight regime that the Flanker is already the best in. Additionally, the plan to implement modern Flankers with TVC further this a non-issue.
Vortex Generators Can Also Delay A High-Speed Stall
When airflow across an airfoil reaches transonic or supersonic speeds, a shock wave forms. Eventually, these shock waves will form at the leading edge of the airfoil, plus at the trailing edge and at any control surface hinge points.
As air moves across the shock wave, it suddenly loses energy. In fact, the energy loss may be so great that the airflow separates from the airfoil behind the shock wave - just like it does in a low-speed stall. If an aileron or elevator lies behind the shock wave, the separated airflow makes the control surface ineffective, and it may make the aircraft impossible to control.
In this high-speed situation, vortex generators can pull in high energy air from outside the boundary layer, mix it with air inside the boundary layer, and prevent separation. They can also disrupt the shock wave, reducing the amount of energy lost as air travels through the wave.
You just named a technology on the Su-27 as a “Wing Strip” I do not believe you are equipped to determine what technology has an impact on the Su-27 or not accurately.
What is too far away?
Look, there is a reason the Flanker’s aerodynamics are still studied to this day. Do not be surprised if there are little things you had no idea existed in the aircraft prior that not found anywhere in open source.
What the hell is a Wing Strip???
Whatever you are referring to as “Wing strips” is wrong and is entirely made-up name for technologies.
The only technology on the Su-27 wings besides basic flight control surfaces is the droop flaps. Leading Edge Droop flaps simply drop down when the aircraft is in alpha flight to allow airflow to easily pass over the top of the wing. They are not vortex generators & the airflow that passes is just regular airflow that is not energized.
They are called droop flaps because they do not extend out like traditional leading-edge slats. They also do not expose any space between such as leading-edge flaps. Droop flaps are technologically superior to the mentioned types. Because not only do they allow airflow to pass over the wings in high angles of attack, they can increase the camber of the wings to produces higher lift.
They are found on aircraft such as Su-27, Mig-29, F-16. As well as aircraft like the F-22 & Su-57
So, what are you referring to on the wing??? Again, they do not produce energized airflow. They also have zero effect on the elevator’s ability to operate. They do increase lift & delay the stall alone. But there is no one single technology that makes an aircraft supermaneuverable. It’s a combination of several technologies & specifications.
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Just a few notes for the bigger picture.
Ventral Fin was standard on the F-15 and was chosen for overall greater aircraft stability (AoA and Mach) but their contribution to F-15 stability was found to be problematic and inadequate, so F-15 designers increased the area of the vertical tail surfaces and the stability problem was solved.
The MiG 29 had ventral fin very early on, perhaps from the beginning, it was later removed, on the other hand, the Su 27 did not have ventral fin from the beginning it was added later for better stability, probably to solve the stability problem.
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I don’t think the RWR covers on the sides of the intake ducts on the Su 27 had much effect on vortex formation, so they were soon removed. But I don’t know for sure. I won’t argue, I’ve never read about the benefit of these covers to the aerodynamics of the Su 27.
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pretty cool did not know this.
One drawing of a future F-15, probably 1968-1969
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They don’t affect anything.They were not even taken into account in the main aerodynamic model
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Yeah, could definitely be a reason. Definitely was placed in the flat shape for a reason in the exact position they have used Vortex Generators in prior designs…
Especially knowing the aircrafts most highlighted abilities. Flying really really well at very high angles of attack.
Making it flat with that specific tapering tip will increase drag in its most capable regime.
Thats pretty cool & very interesting. I am impressed you immediately knew the relevancy of the ventral fins
Ventral fin was part of the F-15 until 1971.
Removing them and increasing the vertical surfaces solved stability problems, plus reduced drag and weight.
EDITING :
Sorry, I thought you were responding to the F-15. Are you referring to the RVR covers on the sides of the intakes or the ventral fin on the Su 27?
As a point of interest, here are the failed F-15 designs from North American and Fairchild Hiller, they ended up behind today’s F-15.
McAir came in first with their 199B - today’s F-15, Fairchild second and NA third. The competition ended in December 1969.
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They sure did love the hell out of those ventral fins too huh. Artist did not definitely captures that lol.
The drawing reminds me of a B1 lancer
They were probably so jealous when the saw the Su-27 for the first time & that is has the massive LERX that actually extend to the canopy like the sculpture.
lol are they sure we did not get the real F-15?
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Every aircraft is about finding a compromise, there is always some advantage which brings some disadvantage.
Of course, the combination of expensive - big, and cheap - small like the F-15 and F-16 was very strong in its time.
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I’d probably guess the first use of LERX would be on the F-5, then the F-18 and F-16.
The “LERX” on the F-15 isn’t exactly a LERX, although it also makes a vortex.
F-15 Small? have you seen one irl?
They are given the nickname flying tennis court first. Not the Tomcat.
Comprise?
That was not the mindset of the United States whatsoever during the Cold War.
The Mig-25 put utter terror in the hearts & minds of the Americans.
The F-15 was developed under a sense of existential threat they perceived the Mig-25 was. Everything the United States produced was under driven by one objective, to prepare for imminent war with the Soviet Union. The Soviets produced & prepared likewise but operated under a Communist ideology.
There was actually no such thing as compromise or a program “budget” in the days of the Cold War.
It was simply, prepare for war with the Soviet Union.
There will never be another era in aviation quite like the Cold War where Lockheed & others were completely free of budgets constraints in developing top of the line technology.
For perspective, The US had 24 hour, 364 days a year nuclear Armed B-52s circling the entire Soviet Union nonstop from 1961-1968.
That was the mindset of the US in the cold war. “Cost” or “compromise” was just not in the cards.
Cheap- small - is F-16…
You don’t understand, everyone, really everyone who has designed aircraft knows it’s one big compromise. Su 27 too.
That’s not F-15 thread
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No, you actually do not understand. The Cold War was a whole other animal. The United States & Soviet Union operated completely differently. the RuF operates completely differently. China does not operate like the US & Soviet Union did.
I guarantee you, In the Soviet Union they did not order their nuclear physicist, rocket scientist & other aerospace engineers to develop a weapon system in preparation for imminent war with the United States, but at the same time “try to keep it within the budget.”
This did not happen in the United States Either. The Cold War was a period of time where the DOD, CIA, Pentagon, Navy, Army, & Airforce had countless black projects & R&D programs.
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RWR covers on the Su-27
I have a similar view