Weird Inverted Stall

[Sheepherder]

What is the reason to not protect the super expensive/skilled Russian pilots to NOT make mistakes in an extreme situation, which can be easily done whilst doing extreme maneuvers to survive a missile attack, if I know the weak point of this plane are nnegative Gs and so an inverted stall?

 

Given that high negative Gs causes people to spew their lunch into their oxygen mask and permanently go blind a proper negative G limiter is something of a formality.

 

You could just as easily ask why the Su-27 doesn't have an auto-trimmer when it already has pitch, roll, and yaw damping.

 

The engines, if working, will produce a force in the opposite direction even if there is no lift. So if the nose of the plain shows 25° down and the engines produce 75.22 kN each, then the plane MUST move in the direction in which the nose is pointing. There is NO way that the 2x75.22 kN (full afterburner) have no influence on the flight path because there is no lift. Again, if you were any near right there would be no space flight possible!

Even without lift EVERY object must move if a force affects the object as long there is no counterforce with the same power!

As long as the afterburner is working the Su27 MUST react on this input and lift has nothing to do with this! Counterforces would be gravity (pseudo Force) and the sum of forces called "air drag".

If a Su27 can riding on her engines straight into the sky or reach a SL mach +1.0, I can't see any real force which could counter this engines force.

Action = Reaction!

If there is Action but no Reaction then there is something wrong!

 

A jet engine is not a rocket, it breathes air to burn fuel rather than a separate chemical oxidizer, and so the amount of thrust generated is directly proportional to the amount of air going into the engine. When you inverted stall, not only is air not flowing directly into your engine, laminar airflow is in fact blocked from entering the intakes by the nose and leading edge root extensions of the plane. So no, the thrust of the engine is not constant, it has in fact suddenly and precipitously dropped to almost zero. An engine in this state actually continues to spin, so barring any other failures if you're not watching your gauges you will probably notice nothing amiss.

 

In fact, in real jet engines the sudden loss of pressure on the intake side often causes the thrust being generated by the engine to take the path of least resistance and comes out the front of the engine, this is called a compressor surge. Sometimes it carries the compressor blades with it.

Edited January 6, 2016 by Sheepherder

[LtMacGowan]

As for the landings the Flanker has a thrust to weight ratio greater than 1:1 so you can let those beautiful engines push you home

[311Gryphon]

I don't have anything intelligent to add to the conversation but I have gotten into quite a few situations where I lost control in the SU-27 and ended up in a very long, slow fall from altitude, upside down, unable to recover, with my plane making a really pretty whistling sound.

 

 

It was completely my fault, as you can tell. I later thought I discovered that I could recover by extending my gear until the nose pointed down and stayed there. Then I could retract the gear and get my engines spooled back up. But when I tried to test that theory I couldn't get back into the uncontrollable position.

[DarkFire]

I don't have anything intelligent to add to the conversation but I have gotten into quite a few situations where I lost control in the SU-27 and ended up in a very long, slow fall from altitude, upside down, unable to recover, with my plane making a really pretty whistling sound.

 

 

It was completely my fault, as you can tell. I later thought I discovered that I could recover by extending my gear until the nose pointed down and stayed there. Then I could retract the gear and get my engines spooled back up. But when I tried to test that theory I couldn't get back into the uncontrollable position.

 

Interesting, I'd never thought of lowering the gear! Might well give that a go, thanks for the tip :thumbup:

 

Believe it or not it's actually difficult to make the Su-27 depart from controlled flight. When it does happen it's usually at altitude with a heavy load of weapons & fuel and can be caused by applying negative angle of attack. The Su-27 REALLY hates negative AOA which is why you'll always see real Flanker pilots roll inverted & pull down rather than pushing over, for example.

[Ironhand]

:) Sometimes the gear. Sometimes the speed brake. In that situation, give everything a try.

[Kondor99]

Former pilot here.  Looks like a classic deep stall with the wash from the wings “blanketing” the elevators, rendering them useless and preventing recovery.  Also looks likely the rudders would be rendered pretty ineffective. 
 

Agree with deploying the gear but honestly it looks un-recoverable in the altitude available. Without yaw and pitch authority, you can’t recover. 
 

The SU-27 is a hot ship.  It’s designed to be unstable, but it’s not some fly-by-wire starship that’s going to keep you out of trouble.  It’s why I love flying the Russian planes - they demand more from the computer in your head

[TaxDollarsAtWork]

Recovery is possible, the sooner the better I found.

You want to induce as much pitching up and down as possible then start imputing right roll left rudder and vice versa you will eventually catch the nose down keep it down and recover. Its all about building up as much oscillation pitch wise

[Breakshot]

Recovery is possible, the sooner the better I found.
You want to induce as much pitching up and down as possible then start imputing right roll left rudder and vice versa you will eventually catch the nose down keep it down and recover. Its all about building up as much oscillation pitch wise

What he said, plus a few things to be aware of

Be sure to turn direct control off, power idle. Start inducing the pitch. Go full gate upon the correct recovery angle on the oscilations and you should be out of it rather quickly.

With DC on, its much harder to recover (but easy to enter that stall).

PS: Lowering gear sometimes also does the trick (as silly as it sounds).

Отправлено с моего STV100-2 через Tapatalk

[stefasaki]

After reading part of the su-27sk manual the deep inverted stall looks realistic, it supposedly is very hard to get out of it. It seems however too easy to enter it. Per the manual you need a negative AOA and an airspeed lower than 310 km/h, which is also what happens in DCS, the problem is that often in the game you can enter the inverted stall while recovering from a cobra-like maneuver, as the game thinks for some reason that your AOA becomes negative, while it should always remain positive. Basically any pitch down with the direct control mode (even from 90+ degrees of AOA) will result in an immediate negative AOA, this is why it’s very easy to enter it in the game if you’re not being careful

[Ashayar]

Now I understand why I crashed two days ago... I didn't know why my engines were shutting down, now I know

 

Thank you!

[Skysurfer]

Engines on the real jet won't shut down, you have AC boost pumps in the right spots of the tanks to account for that.