Forum: Modern Military Aircraft

Quote:

I'm not here to challenge you, but it looks more like the other way around...
Again according to Russians, F15 has the edge in climb up to, at least 23kft.

That chart looks identical the the acceleration chart i've seen between the two.
It looks like the gap are even larger in Su-27 favor at the deck and up to the crossing. As expected, the short take-off lenght of the Flanker do come from high lift.

The Flanker are about 20%& larger than the F-15, has longer legs, are more agile and some 2 ton heavier. The AL-31F has more thrust but lower minimum fuel consumption vs the F-100 PW.
The Flanker still has upgrade and improvements road map left.
And you say the Flanker failed to best the F-15.. yeah riight.

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Except that if the Flanker gets over 26 tons and is no longer a 9G fighter. With its 3500 lb missile load a Flanker is restricted to 63% internal fuel to be a 9G fighter. Su-27 is 4 tons heavier than F-15C empty, and Su-35S is 6 tons heavier than F-15C empty. Add full internal fuel and fuel missile load (and even a 600 gal gas bag for the Eagle) and the F-15C comes it at a whopping 24 tons, and it has a nominal 25 tons of thrust. The Su-27 and Su-35S come to 30 tons and 34 tons, respectively, with a nominal 27 tons and 32 tons of thrust, respectively. Also, at 24 tons the Eagle is a 8.25G fighter, while the Su-27 and Su-35S are 7.8G and 7.4G fighters, respectively. In many aspects the F-15C is a superior platform while it others it is inferior. These two planes (with all their respective upgrades) cannot be declared "better" than the other.

haavarla wrote:

The AL-31F has more thrust but lower minimum fuel consumption vs the F-100 PW.

I'd like to put your information concerning this to a side-by-side test.

Lets also throw into this mix the F100 engine lasts 4x longer between overhauls than an AL-31F does before it's scrap.

The F100-PW-229EEP could achieve the same performance levels as the AL-31F it was pushed to the point of only lasting 1000hrs TBO, or if development of the F100-PW-232 had continued that engine would have been even better (including many F119 improvements). The latter didn't happen because the USAF decided to put their effort into the F119 and F135 programs. (The 229EEP has gained durability from both programs as the name of the game today is life-cycle costs and not stupidly inflated thrust requirements)

TEG

haavarla wrote:

It looks like the gap are even larger in Su-27 favor at the deck and up to the crossing. As expected, the short take-off lenght of the Flanker do come from high lift.

Yes, but what matters is the absolute value and Eagle has it higher.
Therefore, its outright performance is higher, regardless of Flanker's lift, which is of no importance, except at low speeds when Eagle aerodynamics can't produce equal, or more lift.
However, the point is, Eagle can choose to avoid low speeds due higher SEP, which Flanker can't follow and so can dictate the tempo of engagement.

Quote:

Except that if the Flanker gets over 26 tons and is no longer a 9G fighter. With its 3500 lb missile load a Flanker is restricted to 63% internal fuel to be a 9G fighter. Su-27 is 4 tons heavier than F-15C empty, and Su-35S is 6 tons heavier than F-15C empty. Add full internal fuel and fuel missile load (and even a 600 gal gas bag for the Eagle) and the F-15C comes it at a whopping 24 tons, and it has a nominal 25 tons of thrust. The Su-27 and Su-35S come to 30 tons and 34 tons, respectively, with a nominal 27 tons and 32 tons of thrust, respectively. Also, at 24 tons the Eagle is a 8.25G fighter, while the Su-27 and Su-35S are 7.8G and 7.4G fighters, respectively. In many aspects the F-15C is a superior platform while it others it is inferior. These two planes (with all their respective upgrades) cannot be declared "better" than the other.

The Su-27 cannot achieve full AOA and G ratings until internal fuel has been reduced to 60% ( (assuming that the maximum fuel load has been carried), meaning that a long range mission must account for not being cappable of efficent close-range combat until 40% of the fuel has been used.
The technical reasons behind this limitation are simple; when fuel is reduced to by 40% the No.1 fuel tank, located behind the cockpit, and the No.4 tanks, located in the wings, are emptied. The importance of this lies in the No.1 tank which when full has an adverse affect on the plane’s center of gravity, moving it forward of the optimal balance. Thus when it is emptied the plane’s manvering cappabilities rise sharply.

This fact means that the mission planning has to be very precise when it comes to the fuel – which is easy during training, but something almost impossible under real combat circumstances. In the case of any kind of unplanned engagements the plane has to get rid of fuel overload; jettisoning BVR missiles is also a very real possibility as they constitute a weight and aerodynamic penalty. Only once the Flanker is lightened to a certain extent it is highly maneuverable.

I'm not sure if the SK version sported the fuel dump pump, or if it was installed at a later date..? See pic below.

Anyway, at least the Flanker can choose the mission range from the very start without the extra drag from ext DT. In the F-35A spirit, this is a nice pros..

Not entirely sure if i get these graphs right, but..
The thick graphs are 60% of full fuel load(nominal) + Weapons(6 A2A missiles).
The thin graphs are 50%of nominal fuel load, IMO total 30% fuel load + weapons.
NB, this is with the Su-27SK version! So it would be interesting indeed to see the Su-35S charts here.. it would be a whole new ball game.

Quote:

The AL-31F has more thrust but lower minimum fuel consumption vs the F-100 PW.

I'd like to put your information concerning this to a side-by-side test.

Lets also throw into this mix the F100 engine lasts 4x longer between overhauls than an AL-31F does before it's scrap.

The F100-PW-229EEP could achieve the same performance levels as the AL-31F it was pushed to the point of only lasting 1000hrs TBO, or if development of the F100-PW-232 had continued that engine would have been even better (including many F119 improvements). The latter didn't happen because the USAF decided to put their effort into the F119 and F135 programs. (The 229EEP has gained durability from both programs as the name of the game today is life-cycle costs and not stupidly inflated thrust requirements)

I understand this.
The 117S engine are adapting to improved life-cycle cost..

If it was due to the SU AF doctrines at the time, where they max performed the engines(more heat) at the cost of TBO, or not is slightly beside the point. The AL-31F engine was very easy to replace/change and so was the field repairs. It was also interchangeble with eachother L=R. Those engines was mass produced. SU AF did this with the full knowledge(low TBO) that it would strain the logistic supply lines.

I said it before, for its intended purpose, the AL-31F engines where exellent designed with good fuel consumption, low weight, resiliant to airflow disruption and high output thrust.

They meet their requirements, and i doubt any fighter jockey whom fly against the Flanker, spare its engines lower TBO one thought..

haavarla wrote:

The thin graphs are 50%of nominal fuel load, IMO total 30% fuel load + weapons.

Thin curves are absolute lift limits and define instantaneous turn performance, on the deck.

haavarla, I knew about the weight issue but not about the CG balancing. Also of note is that the Russian AAM are far heavier than their US counterparts. This is why an Eagles weapon load is about half the weight while giving up only two missiles.

Forum: Modern Military Aircraft

Aicraft design choices