[CLOSED, NO BUG] F-15C able to Supercruise.

[Czar66]

Ok, one night on 104th server I were returning to base in a F-15C with empty payload and 1/4 fuel without burners. Before I could notice, the plane went supersonic at 1.08 ish (afaik) mach below angels 20.

 

I did recon that F-15Cs can not supercruise. Cool, and today I did some testing. 13.500 ft.

 

Full weapons load consisting in: 6x AIM-120C, 2x AIM-9M. No bags. . Mach 1.0+ displayed through aircraft instruments. Edit: 1.010 through HUD.

 

I shot two AIM-120Cs and the speed went up. 1.014 through HUD

 

Two more 120s the speed went up even more.

 

I did jettison all the missiles and kept almost all the fuel the 15c clean can carry and the speed went to 1.051 mach through HUD.

 

Follows a track file and Tacview track file.

 

Did I have missed anything? Is it normal to it's instruments show mach 1.0 plus without burners?

 

I have searched and did not found nothing in this subject. Sorry if I did miss it.

Supersonic 1.trk

F-15 test.zip

Edited August 22, 2015 by Czar66
missing info

[Exorcet]

I'm pretty sure there is a thread on this already. Supercruise isn't a hard limit, which is to say planes that don't supercruise in combat still may be able to break Mach 1 without AB. Usually it takes a clean and light aircraft and as with the F-15 you will only just barely exceed Mach 1.

 

Also I'd use the HUD Mach indicator (comes up when you press the 2 key). It's easier to read and I've never been sure if the front panel Mach gauge is really accurate.

[Czar66]

I'm pretty sure there is a thread on this already. Supercruise isn't a hard limit, which is to say planes that don't supercruise in combat still may be able to break Mach 1 without AB. Usually it takes a clean and light aircraft and as with the F-15 you will only just barely exceed Mach 1.

 

Also I'd use the HUD Mach indicator (comes up when you press the 2 key). It's easier to read and I've never been sure if the front panel Mach gauge is really accurate.

 

yep, I was following that indicator, but I did not taken a screen of it. Mach 1.005 I believe with aircraft level and full armament and no bags.

 

 

Strange thing is, last December I remember the aircraft struggling to pass .967 ish without burners. On currently version it does not happen.

[GGTharos]

The result is correct; the eagle can just barely straddle the sound barrier on MIL.

[Wizard_03]

Yeah I do it all the time, when I practice dog fighting I usually just load up 2 or 4 sidewinders and nothing else and maybe 60 or 70 percent fuel and it has no problem super cruising.

[Czar66]

The result is correct; the eagle can just barely straddle the sound barrier on MIL.

 

Good stuff. :thumbup:

 

Yeah I do it all the time, when I practice dog fighting I usually just load up 2 or 4 sidewinders and nothing else and maybe 60 or 70 percent fuel and it has no problem super cruising.

 

That's something good to try out!

 

 

Thank you for the posts, guys. Looks like it was something new to be known by me. :smartass:

 

S! good flying!

[Capn kamikaze]

I know it may be viewed as nitpicking, but I would argue that no it can't actually supercruise, since it's still in the transonic domain, which is typically viewed as between M0.8 and M1.2.

 

Some of the airflow around the F-15 at ~1.1 will still be subsonic.

 

The F-22 on the otherhand can supercruise, it can get up to M1.4 without afterburner, which is definately in the supersonic domain (all the airflow will be supersonic).

[Czar66]

I know it may be viewed as nitpicking, but I would argue that no it can't actually supercruise, since it's still in the transonic domain, which is typically viewed as between M0.8 and M1.2.

 

Some of the airflow around the F-15 at ~1.1 will still be subsonic.

 

The F-22 on the otherhand can supercruise, it can get up to M1.4 without afterburner, which is definately in the supersonic domain (all the airflow will be supersonic).

 

That's the thought I ended up with. Yes, F-15 aero design and powerplant does not able it to supercruise IRL.

 

I was about to mention the 22, but would derail the point to some extent. If the modeling of transonic speed on the F-15s are on point, then there's no issue. That 1.0 + mach just caught me off guard.

 

Cheers Cap'n.

[Capn kamikaze]

I don't think it derails it, it puts it into context.

[Roadrunner]

what would be the definition of super cruise?

 

i ask this, because cruise speed is usualy NOT max MIL power, aye?

 

so even if a plane can go supersonic without burner it wouldnt be supercruise if he has to go 100% MIL as this is not cruise "setting"?

[Exorcet]

what would be the definition of super cruise?

 

Mach 1+ without afterburner.

 

It's not really going to be a cruise speed, it's only efficient relative to having AB on.

[Gryzor]

what would be the definition of super cruise?

 

i ask this, because cruise speed is usualy NOT max MIL power, aye?

 

so even if a plane can go supersonic without burner it wouldnt be supercruise if he has to go 100% MIL as this is not cruise "setting"?

 

From knowedlege, supercruise is the ability to sustan MACH 1.00 and above using mil power (100% or less), without burners.

[Capn kamikaze]

It's not as simple as the airspeed or groundspeed working out to being supersonic overall or mach meter saying >1.0

 

As I mentioned earlier, 1.0 is not really supersonic, it is right in the middle of the transonic speed range, some parts of the airflow around the aircraft will be subsonic at M1.0.

 

From an aeronautical engineering perspective, it's generally accepted that until about 1.2 you're not really going supersonic.

 

The real problem is that in that speed range drag is quite high, so fuel consumption will be higher than in the completely subsonic domain and the supersonic domain, and considering "cruise" infers getting efficient fuel usage then calling it supercruise just because the meter says >1.0 is a false assumption, and definately different to real supercruise eg M1.4.

[VincentLaw]

From an aeronautical engineering perspective' date=' it's generally accepted that until about 1.2 you're not really going supersonic.[/quote']I disagree. Transonic and supersonic are not mutually exclusive. Regions in the flow around any aircraft can be subsonic at any aircraft speed. The Apollo capsules reentered around Mach 33, but airflow at the front of the capsule was subsonic.

Edited August 31, 2015 by VincentLaw

[Exorcet]

It's not as simple as the airspeed or groundspeed working out to being supersonic overall or mach meter saying >1.0

 

As I mentioned earlier, 1.0 is not really supersonic, it is right in the middle of the transonic speed range, some parts of the airflow around the aircraft will be subsonic at M1.0.

 

From an aeronautical engineering perspective, it's generally accepted that until about 1.2 you're not really going supersonic.

 

The real problem is that in that speed range drag is quite high, so fuel consumption will be higher than in the completely subsonic domain and the supersonic domain, and considering "cruise" infers getting efficient fuel usage then calling it supercruise just because the meter says >1.0 is a false assumption, and definately different to real supercruise eg M1.4.

 

I think you're reading into the name too much. While Mach 1 is in the transonic regime, an object at Mach 1 is supersonic. It is going faster than the speed of sound in the ambient air.

 

I wouldn't put much into the "cruise" in supercruise either. It doesn't imply some need for efficiency. It's just how the phrase was originally coined.

[Capn kamikaze]

I disagree. Transonic and supersonic are not mutually exclusive. Regions in the flow around any aircraft can be subsonic at any aircraft speed. The Apollo capsules reentered around Mach 33, but airflow at the front of the capsule was subsonic.

 

Infront of the shockwave yes, but that is infront of the craft, not around it, as far as the craft is concerned that air has not reached it yet, if you go far enough ahead of any supersonic flow you will find a subsonic one.

 

Transonic and supersonic are not mutually exclusive.

 

Yes, they are, that is the whole point of defining them.

[Capn kamikaze]

I think you're reading into the name too much. While Mach 1 is in the transonic regime, an object at Mach 1 is supersonic. It is going faster than the speed of sound in the ambient air.

 

I wouldn't put much into the "cruise" in supercruise either. It doesn't imply some need for efficiency. It's just how the phrase was originally coined.

 

The object overall is supersonic, say the mach-metre says it's just over 1.0, some parts will be higher, and some parts lower.

 

You can't just look at an objects speed through the air, or from point A to point B and say it is in the supersonic realm just because of that, and supercruise is called that because the aircraft is supersonic, and cruising, but if it is infact at transonic speeds then it would be a miracle if it was infact cruising, since as I mentioned earlier the transonic regime is high drag, and high drag is not good for fuel efficiency.

[Exorcet]

Right, I know how transonic works. Local velocity is not the total velocity, etc.

 

Basically what's being said is that supercruise does not imply supersonic regime or a "cruise" speed. I've only even seen two definitions for supercruise. One being no AB and holding Mach 1+, the other being no AB and holding Mach 1.5+. I think the latter was used by Lockheed for F-22 marketing purposes.

[VincentLaw]

if you go far enough ahead of any supersonic flow you will find a subsonic one.

Here you are wrong. the Mach number is measured relative to the aircraft, so if the world was flat with uniform freestream flow, the flow infinitely far in front of a supersonic plane would be supersonic. The Apollo capsules generated bow shock waves. Bow shocks result in subsonic flow behind the shock wave and around the front of the vehicle.

 

Yes' date=' they are, that is the whole point of defining them.[/quote']No, they are not. Transonic is basically just a way of saying the flow is more interesting. Regions of flow around the aircraft can be supersonic when the vehicle is subsonic, and can be subsonic when the vehicle is supersonic. The vehicle itself is supersonic when freestream Mach > 1.0 and subsonic when freestream Mach <1.0.

 

Basically a more specific definition of supersonic is that disturbances from the airplane cannot propagate forward to interfere with the freestream flow ahead of the airplane before the shock wave generated by the airplane gets there. This starts happening at Mach 1.0+ regardless of how much subsonic flow you have around your vehicle.

 

marketing purposes

Right. Catch phrases like "supercruise" and "gen 5" have more marketing than engineering significance.

Edited August 31, 2015 by VincentLaw

[Capn kamikaze]

The Apollo capsules generated bow shock waves. Bow shocks result in subsonic flow behind the shock wave and around the front of the vehicle.

 

That is simply not true, behind the shockwave can still be supersonic aswell, it can just be of a lower speed than infront of the shock, the only difference is you get a weak shock rather than a stong one, and is one of the reasons (other than heating becoming a factor) why you have the region known as hypersonic speed, which M33 certainly is.

 

No, they are not. Transonic is basically just a way of saying the flow is more interesting.

Again, no, you're over simplifying it, there is a reason for it being defined other than it being more "interesting" the way the air flows around the craft is vastly different between subsonic(1), transonic(2) and supersonic(3), (1) you will have no shockwaves, (2) you will have some shockwaves around or on certain parts of the aircraft, such as on the upper and lower surfaces of the wing, and (3) fully developed shockwaves around all parts of the craft that can generate them.

 

Basically a more specific definition of supersonic is that disturbances from the airplane cannot propagate forward to interfere with the freestream flow ahead of the airplane before the shock wave generated by the airplane gets there. This starts happening at Mach 1.0+ regardless of how much subsonic flow you have around your vehicle.

Yes, except for specific parts of the aircraft where the local velocity is <1.0...

 

And again, the word cruise can't be ignored, as I said, it implys strongly that there is a reasonably good expected fuel/speed tradeoff without having to use reheat.

[VincentLaw]

That is simply not true' date=' behind the shockwave can still be supersonic aswell[/quote']flow behind shocks can be supersonic, but I was referring to a bow shock wave. The front of a bow shock is essentially a normal shock, and flow behind a normal shock is always subsonic.

 

a pointless exchange of "yes" "no" "yes "no" isn't going to get anywhere. Try checking out this page instead: http://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-supersonic-flight-58.html

Vehicles that fly at supersonic speeds are flying faster than the speed of sound. The speed of sound is about 768 miles per hour (1,236 kilometers per hour) at sea level.[...]Flight that is faster than Mach 1 is supersonic.

Note that it is referring to "flight" faster than Mach 1, not "flow" faster than Mach 1. As soon as the F-15C breaks past Mach 1, it is supersonic.

Subsonic flight: Less than Mach 1. This is the speed traveled by most of the commercial airplanes that carry people and cargo.

 

Transonic flight: At or about Mach 1.

Edited September 1, 2015 by VincentLaw

[Capn kamikaze]

As a whole the F-15 is supersonic, but the flow has to be considered if you're going to make any claims to it having any sort of decent fuel efficiency and that has to include getting out of the transonic range, as that is never going to give good or even acceptable fuel consumption, and that is where the whole issue of calling is superCRUISE comes in, it is not remotely in any sort of cruise state in that speed range.

 

I know what supersonic flight is thanks, bow shocks CAN be subsonic, but only under special circumstances, such as the case of a stong shockwave, but we're not talking about space shuttles or capsules, we're talking about the F-15, and whether flight at transonic speeds (high drag, so poor fuel economy) counts as "supercruise", we'll just have to disagree on that, to me, it doesn't fit the definition of either being supersonic, transonic yes, supersonic no, or cruising in any way shape or form until you're at least out of that speed range, ie >M1.2.

Edited September 2, 2015 by Cap'n kamikaze

[Maverick Su-35S]

When the aircraft goes above a certain airspeed for which the airflow is supersonic from the nose (except in front of it where it will always be locally subsonic) to tail, then that can be called supersonic flight..., anywhere below this speed where subsonic flow regions appear anywhere on the airframe, even at the tail of the plane, then that Mach number or airspeed is called transonic, so it can no longer be attributed to a supercruise flight.

 

The transonic regions may vary from anywhere between 1.15 to as much as 1.3+ depending for airfoil section, 3D wing's shape (aspect ratio, wing sweep, etc.) and overall airframe's shape. So in this case, some aircraft are physically supercruising only after a given Mach number while some others don't. For this reason, supercruise flights are called to be that way, by convention, only after a certain Mach number had been reached, for instance nowadays it's considered so only after Mach 1.5, which is far from 1.08 or 1.1 that some talk about! Indeed the soundwaves are falling behind the aircraft as it goes faster than exactly 1.0 and can't be heard outside the Mach Cone, yet it's still transonic...!

 

The F-15 is only able to reach higher transonic flights with full MIL power (without AB), not supersonic.

[Capn kamikaze]

When the aircraft goes above a certain airspeed for which the airflow is supersonic from the nose (except in front of it where it will always be locally subsonic) to tail, then that can be called supersonic flight..., anywhere below this speed where subsonic flow regions appear anywhere on the airframe, even at the tail of the plane, then that Mach number or airspeed is called transonic, so it can no longer be attributed to a supercruise flight.

 

The transonic regions may vary from anywhere between 1.15 to as much as 1.3+ depending for airfoil section, 3D wing's shape (aspect ratio, wing sweep, etc.) and overall airframe's shape. So in this case, some aircraft are physically supercruising only after a given Mach number while some others don't. For this reason, supercruise flights are called to be that way, by convention, only after a certain Mach number had been reached, for instance nowadays it's considered so only after Mach 1.5, which is far from 1.08 or 1.1 that some talk about! Indeed the soundwaves are falling behind the aircraft as it goes faster than exactly 1.0 and can't be heard outside the Mach Cone, yet it's still transonic...!

 

The F-15 is only able to reach higher transonic flights with full MIL power (without AB), not supersonic.

 

Thankyou.

[SinusoidDelta]

Not to stir the pot here but my understanding was that no universally accepted definition exists for the term supercruise. If anyone can provide an official reference please do. The term 'supercruise' was invented by Lockheed Martin during development of the F-22. There is no point arguing over a capability that has no specific criteria.