Forum: F-35 versus XYZ

Last edited by haavarla on Jan 31, 2012 - 05:35 PM; edited 3 times in total

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Actually this got me thinking about the T-50. Wide engines, small verticals. At low speeds they are going to be of marginal effectiveness (even though they are all moving, the low Reynolds number may cause them to stall out before they can produce the required load). "But it has 3-D TVC" yes I know, but with one engine inoperative its a matter of "does the TVC angle allow the thrust line to reach, or pass, the CG" if not then it will still be yawing out and the plane will be pushed sideways to a great degree for the duration of the flight, possibly allowing nothing more than the opportunity for the pilot to pull the D-rings. Again this is a low speed event I am talking about. I trust that the engineers involved are aware of such problems and have things in place. I am just stating what appears to be a risky area for a design with wide engines and small fins. May be the TVC moving thrust line closer to center (reducing the yawing moment) will allow the fins to do the rest with the reduced "bite" load.

Well, is see your point. But keep in mind that while the Verticals Stabz are lower vs Flanker, they are wider, and on those wids one can clearly see how much they can rotate as well. So this does increase the Relaxed Horisontal Stability if nothing else.
And also you notice that the Engines are canted slightly outwards from each other, this too helps keeping the jet stable if it would have to fly on one engine.
And lastly it has large control surfaces, and more of em vs any Flanker. That with the same advanced FCS that is currently on the Su-35S, it should not be any problem for a pilot to fly on one engine.

I'm still not sure how the onboard FCS control the TVC on the T-50 works. Are there several different flying mode, which the pilots can choose from, can the pilot disengage them completly when flying etc etc.

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haavarla wrote:

I think i read about an incident with an IAF MKI landing with one engine. One engine erupted in flames in mid-flight. But i do not have anything to go by.
I'll try to sniff around and see if anything turns up.

Thank you.

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If one were to compair the F-14 and Flanker. It is widly known that the Flanker posess more relaxed stability in the horisontal plane, right?
Hense it can do those crazy manuveres without entering uncontroled spin.

It's actually the opposite, it is more likely to enter uncontrolled spin because it is unstable. And most of the instability is vertical, not horizontal. Most planes are stable: they're nose-heavy, so while the wings push the plane up, the tail has to push down to keep the nose from dropping. So if the plane starts to stall, the nose drops, the plane dives a bit and picks up speed, and the wings unstall and lift the nose back up. With a relaxed static stability design, the plane's center of lift is farther forward and the nose wants to go up. Pitching up moves the center of lift even farther forward, pitching the nose up even faster rather than automatically correcting the deviation from forward flight. The plane flips up until either it goes into a stall with its tail pointing down, or if it's going fast enough the wind hitting it straight in the flat of the belly and wings tears it apart. Like the F-16 and basically every fighter built after it besides the MiG-29, the Su-27 wants to pitch its nose up and flip backwards in under a second.

Basically, the plane is more maneuverable specifically because when it is left to its own aerodynamics, the plane will flip itself backwards in a fraction of a second. Unstable designs rely on the flight control computer to let it start to flip out of control, thereby allowing a very fast maneuver, then catch it again faster than humanly possible, before it actually goes too far. Think of it like trying to fire an arrow backwards. The feathers will try to flip the arrow around the right way almost instantly. With computer-controlled feathers, the arrow could constantly be trying to flip up, down, left, right, and the computer will make sure every time it starts to flip, the feathers try to flip it back the other way, so it keeps going straight. But if you do want to actually turn, the computer just lets the arrow flip that direction for an instant before catching it again. It's much faster than trying to push a regular arrow to turn in that direction. (And there are other aerodynamic advantages of the nose wanting to go up.)

But the computer has to be right about catching the flips, or you flip out of control faster than a human pilot can do anything about it. In normal flight, the computer is completely reliable. That's tested 40 times every second in every unstable plane flying. But what if the plane is flying in a regime that's not so completly proven and tested that the computer knows exactly what to do to correct (such as, one of the engines is out)? And the control surfaces have to be fast and powerful enough to push the nose back to forwards in time. Look at a 737; the tail control surfaces are about 50 feet aft of the center of mass in the engines and wing root. It doesn't take much sideways airstream on the vertical stabilizer to create a large lever-action torque to push the plane back towards straight flight. Look at an Su-27 in contrast; the tails are practically right on top of the center of mass in the engines and wing root. There's very little lever arm there for the stabilizers and rudders to force the plane back to straight flight when the center of mass has an off-center thrust. And the Su-27's nose is long; if it starts to flip sideways because an engine goes out, the drag on the nose can push it farther around sideways with a lot of leverage. The Su-27 has very large tails to compensate for their short lever arm, but they still have a short lever arm.

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In the RuAF we never hear about near accidents if all turns out well. We always get to hear of crash, so go figure..
But that beeing said, there could be sources out there i don't know about.

Same here. The English saying is, "If it bleeds, it leads." Or in other words, if nobody dies, it's not news, so it doesn't get widely published. That's why I asked; I don't know of any cases where the Su-27 landed with an engine out, but that doesn't prove to my satisfaction that none ever did.

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It's actually the opposite, it is more [...]

Yeah, i know. But i was not talking about the yaw/pitch or roll relaxed stability at all. I was spesificly talking about how the Flanker are far more 'relaxed stable in the Horisontal plane'.
And further more The Flanker has quite advance FCS, it will not enter any spin due to its inherent design, it come only by the pilots command. As we can see on airshows display. And further more it is remarkedly quick in re-gaining control once the jet are fully stalled too.

I was at MAKS2011. And saw the Su-35 b/n 901 doing crazy stuff i've never seen before, it was almost redicules unreal to watch.

Here you have the best video coverage from the whole Airshow. Superb quality too.
Enjoy.
http://www.youtube.com/user/KonstantinKhmelik

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My understanding was that no Su-27 derivative had ever successfully landed on one engine, because the wide engine spacing with such powerful engines caused very high yawing torque from the remaining engine at any throttle setting able to the plane in the air. An Su-27 or MiG-29 with one engine out is uncontrollable without essentially idling the second engine. But I could just be wrong. Is that untrue?

I don't know of any reports but I assume it can land on one engine.
The MIg29 can. Reported Indian Newspaper.

ON 24 Aug 09, Sqn Ldr SV Saharan(25065-T) F(P) was authorised to fly a two aircraft PI mission on a MiG-29 aircraft. During rejoin, the pilot realised that the left engine RPM did not reduce below 84% with throttle at idle. He decided to switch off the engine and carry out a single engine recovery. While switching off the HP cock of the engine, RPM dropped to idle and the engine did not switch off. Despite this, Sqn Ldr Saharan carried out a single engine landing with the RH engine (LH engine producing idle power). Subsequently, the pilot cleared off the runway and switched off the right engine.

and it be a few years before the t-50 finallycomes out. Russia is a little behind in the "stealth race" Wink

Perhaps relevant to single engine debate:

Su-30 Caught Fire Before Crash – Investigators MOSCOW, February 28

http://en.ria.ru/mlitary_news/20120228/171592093.html

"The crew of a Su-30 fighter that crashed earlier on Tuesday in Russia’s Far East reported an engine fire before the crash, a spokesman for the Main Military Investigative Directorate said.

The Su-30MK2 fighter jet crashed 130 km northeast of Komsomolsk-na-Amure during a post-construction test flight. Both pilots ejected safely, although one of them was hurt on landing.

“While executing acceleration to a maximum speed, the first pilot reported a fire in the right engine,” the spokesman said. “The flight controller immediately ordered the crew to eject.”

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“The flight controller immediately ordered the crew to eject.”

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The Russian military earlier said that the plane had been built for export.

I would think an appropriate response to the flight controller might be,

"We're outta here comrade." Shocked

"The Russian military earlier said that the plane had been built for export." Very Happy

Me guess, is that the Su-30MK2 are part of the last order from Vietnam.
And it is KnAAPO whom produce em.
So it fit nicly.

Anyway, what has this to do with F-35 & T-50

Forum: F-35 versus XYZ

T-50 and F-35