Did this actually happen or is it just propaganda nonsense?

[mikoyan]

So what are the advantages of a diamond wing like the f-22s over a swept wing like the su-27 when doing high alpha turns? The raptors wings are basically deltas so are they draggy at high alpha or not very good at sustained turns?

Like for example everybody says that a mirage is good on instantaneous turns, but bad in sustained because of the high drag of the deltas. So how was that "drag" overcome by the Eurofighter and rafale?

[Exorcet]

The F-22's wing should be able to handle high alpha without much threat of flow separation. It also allows a high lift to structural mass ratio by limiting the root bending moment compared to span and allowing for a very thick wing root.

 

On paper, the Su-27's wing should be better for subsonic flight, but between lifting body, FCS, and engines it's hard to say which plane is more agile just by looking.

 

Over coming drag can be as easy as adding thrust. The EF in particular is very light and has a lot thrust which would help overcome the inherent drag of the delta wing. I've also heard that the wingtip pods are shaped to help with tip vortices, but I'm not sure how effective they'd be.

[marcos]

So what are the advantages of a diamond wing like the f-22s over a swept wing like the su-27 when doing high alpha turns? The raptors wings are basically deltas so are they draggy at high alpha or not very good at sustained turns?

Like for example everybody says that a mirage is good on instantaneous turns, but bad in sustained because of the high drag of the deltas. So how was that "drag" overcome by the Eurofighter and rafale?

The Mirage's downfall in sustained turns is more about thrust/weight than having large wings. Large wings relative to aircraft size (low wing loading) usually mean less drag in high g turns. The Rafale and Typhoon have 2 engines that each produce more thrust than the Mirage's (even dry in the case of the Typhoon), so the problem is no longer there.

 

The Su-27 has a very similar wing loading to the F-22, so subsonic performance should be similar. The straking of the Su-27's wing should help prevent separation at high AoA but the clipped diamond shape of the F-22's wings should reduce wave drag. The F-22 front wing section actually sits above the intakes, and that forward wing extension should also help reduce separation at high AoA. Clipped diamond and delta wings provide a larger wing-area-to-span ratio and so are better at reducing drag during high-g turns whilst minimising wave drag.

Edited September 8, 2012 by marcos

[Pilotasso]

The mirage not only has a larger wing but it also sports a lower bypass engine, great for high altitude speed but bad for acceleration and T/W.

[Exorcet]

The Mirage's downfall in sustained turns is more about thrust/weight than having large wings.

I think he was talking about the effect of planform, not wing size.

 

The Su-27 has a very similar wing loading to the F-22, so subsonic performance should be similar.

The aspect ratios and sweeps are very different though, both favoring the Flanker for low speed. Those things should have more impact than wing loading.

 

I do wonder though if the Su-27 suffers a drag penalty from its very large LERX's under certain conditions.

[marcos]

I think he was talking about the effect of planform, not wing size.

I think in the case of the Mirage, its thrust/weight ratio is so poor that wing planform is the least of its worries as regards sustained turns. The fact it still performs reasonably in instantaneous turns probably means the wings themselves are doing a good job.

 

The aspect ratios and sweeps are very different though, both favoring the Flanker for low speed. Those things should have more impact than wing loading.

I agree as regards aspect ratio and sweep but wing loading is fundamental at any speed.

 

I do wonder though if the Su-27 suffers a drag penalty from its very large LERX's under certain conditions.

I don't know, the F-22 has fairly large chines blended to the intakes, which should function as LERX at low speeds and provide more lift in the supersonic regime, but also incur a drag penalty. They do present a lower cross-section to radar than LERX though.

 

In cruising the effects of LERX are generally minimal. As a general rule of thumb, LERX and controllable canards are aerodynamically superior to chines but far worse in terms of radar cross-section. That is just a general rule though.

[marcos]

The mirage not only has a larger wing but it also sports a lower bypass engine, great for high altitude speed but bad for acceleration and T/W.

The thrust just isn't high enough either way. ~21,000lb loaded and ~13,500lbf of thrust. TWR = ~0.64.

[IvanK]

for what its worth Mirage 2000C Fan Plot:

Edited September 9, 2012 by IvanK

[Pilotasso]

Instantaneous or sustained?

[marcos]

Instantaneous or sustained?

Clearly not sustained. If you look at the bold line contours they are basically showing SEP (Specific Excess Power) in fps (units of SEP are velocity). All the high g manoeuvres are are negative SEP and therefore not sustainable. Only the manoeuvres below the '0' countour are sustainable.

 

Reading the graph, the highest sustainable g is ~6.8g at Mach 0.92. The graph is measured at 15,000ft though. Stronger manoeuvres may be possible at sea level.

Edited September 9, 2012 by marcos

[aaron886]

In cruising the effects of LERX are generally minimal.

 

I was under the impression they can incur a significant drag penalty just due to vortex drag, even at low alpha.

[marcos]

I was under the impression they can incur a significant drag penalty just due to vortex drag, even at low alpha.

Not significant during cruise. All lift producing 3D objects do to some extent but LERXs are no worse than chines or canards.

Edited September 9, 2012 by marcos

[Exorcet]

I was under the impression they can incur a significant drag penalty just due to vortex drag, even at low alpha.

 

At low AoA, they're basically extreme delta wings. Compared to the wings, they are very inefficient (cd wise), but in terms of total drag force, they don't contribute very much because they're small. They also aren't designed to generate lift at low AoA, so the cl's are relatively low.

 

Induced drag = (cl^2/pi*e*AR*2)*rho*V^2*A

 

cl and A are small compared to a traditional wing, which helps.

e and AR are very low which hurts.

[marcos]

Did this actually happen or is it just propaganda nonsense? Part II

 

http://www.theregister.co.uk/2011/06/08/eurofighter_beaten_by_f16/

 

Pakistani pilots flying modernised versions of the 1970s-vintage F-16 Falcon fighter have beaten the RAF's brand-new Eurofighter Typhoon superfighters during air combat exercises in Turkey, according to a Pakistani officer.

 

 

Costs like a Raptor, flies like a Tornado

This interview with an unnamed but evidently experienced Pakistani Air Force (PAF) F-16 pilot on exchange with the Turkish air force, posted on the official site of the PAF display team, includes the following intriguing passage. (Hat tip to the excellent DEW Line blog for flagging this up.)

 

Q: Any memorable experiences that you would like to share?

A: On one occasion – in one of the international Anatolian Eagles - PAF pilots were pitted against RAF Typhoons, a formidable aircraft. There were three set-ups and in all three, we shot down the Typhoons. The RAF pilots were shocked.

 

Q: Any particular reason for your success?

 

A: NATO pilots are not that proficient in close-in air-to-air combat. They are trained for BVR [beyond Visual Range] engagements and their tactics are based on BVR engagements. These were close-in air combat exercises and we had the upper hand because close-in air combat is drilled into every PAF pilot and this is something we are very good at.

 

The Anatolian Eagle air-combat exercises are hosted by the Turkish air force and would have seen Pakistani pilots on exchange with the Turks flying modernised Turkish "Block 50" F-16s, a much-upgraded version of the original US made 1970s Fighting Falcon, which is now in service with many air forces and assembled under licence in various countries including Turkey.

[GGTharos]

That's too funny :D

[Pilotasso]

Old news too. I have Pakistani pilots at work, they like to spice their stories up a bit :)

[EtherealN]

Old news too. I have Pakistani pilots at work, they like to spice their stories up a bit :)

 

Well, tbh, that would pretty much describe "pilots" in general regardless of nationality. :D

[marcos]

I thought as much.

 

Do Pakistani F-16s even have helmet-mounted targeting? It would be real interesting to know how they won without that.