I just got the IRIS F-15E "Mudhen Driver" a couple of days ago, but something seems odd with the speed. The aircraft will only accelerate to about 550 KIAS (and about 600 in a dive), but I checked online and in the IRIS documentation, and it's max speed is over Mach 2.5. So that means that it should have supercruise capability (at least I'd think so), and I can't even get supersonic with full afterburner. I assume I'm flying it incorrectly, but what could I be doing wrong?

 

Thanks,

boeing247

 

(and I'm asking here because I can't seem to get into the IRIS forums--and there are more people here )

First, I do not believe the F-15E is capable of supercruise. Second, have you checked the mach indicator(s)? There is one in the lower left area of the HUD, and one on the forward instrument panel That is where you will see whether you are supersonic or not, not on the standard airspeed indicators.

I'll check the Mach indicator (I didn't see it at first--I couldn't find it on the HUD like in the Superhornet), though I was flying low, and mach 1 at sea level is 661 KIAS, so I'm pretty sure I wasn't even at Mach 1.

 

Perhaps it's not capable of supercruise, but if it can reach Mach 2.5, I should have no problem reaching Mach 1...

 

Edit: And I just checked the aircraft.cfg file, and the max mach is listed as 2.20.

Okay, I looked into it a bit more, and I found this:

 

The static_thrust variable in the config file is set to 17800; that's the dry thrust (military power). Then, the rated_N2_rpm variable is set to 29100. However, the max N2 RPM on the real F-15E is 13800 (at least that's what I found), and 29100 is the thrust (in lbs.) of full afterburner, which several sources agree on. I checked the IRIS F-22's aircraft.cfg file and discovered that it has static_thrust set to 36000, which is the thrust on full afterburner. However, when I input the correct values into the F-15E's config file, the aircraft began flying much too fast, even at only military power--I got it up to 500 KIAS shortly after lifting off. It still handled like an F-15, but it seemed too fast. How fast should it be, and what's with the aircraft.cfg variables?

 

Edit: I just did a test with the normal engine variables. With full afterburner at 14000', where the speed of sound should be around 570 Knots, the aircraft could only manage 605 Knots in straight-and-level flight.

The F-15E is really not all that fast as I understand it because it has more drag due to the larger fuel tanks vs. the C model. It is very unlikely that an F-15e would see mach 2+ under ideal conditions, that is even difficult for the A and C models. I don't have the IRIS model to compare, but the Milviz one seems to have a very accurate flight model, and if I recall correctly, it won't do much more than mach 1.5.

Hm... still, mine seems pretty sluggish, even considering that. What values does the Milviz version have for static_thrust and rated_N2_rpm?

Does the Milviz version have the values for those variables of the real aircraft, the same as the IRIS one, or totally different ones?

I can't give any further information but I know that the F-15 (all variants) are not capable of supercruise....wish I was more help

I recently acquired the Iris F15E as well and i got it to Mach 1.9 @ 40.000 ft when flying straight and level.

Hm... so is max speed defined as max speed in a dive? That doesn't seem right--it definitely seems too slow.

My comments provided are completely independent of who makes said virtual version. I'm talking strictly real world airplanes here.

 

Speeds are relative. With jet engines you get that fast speed at optimal altitude, and only under optimal conditions -- meaning relatively light weight and no draggy external stores.

 

At low level, and with the conformal fuel tanks installed and with the external store pylons hung on the CFT's, the F-15E simply will not exceed Mach 1.0 on the deck -- because the thick air produces such significant parasitic drag that it won't happen. Further, your fuel flow with full burners engaged is so atronomical that you'll exhaust your supply of fuel in the header tank very quickly and the rate of burn actually exceeds the maximum rate of fuel feed from the various tanks that fill the header tank from which the fuel is sent to the engines.

 

Cheers,

 

Ken

 

Hm... so is max speed defined as max speed in a dive? That doesn't seem right--it definitely seems too slow.

 

No, max speed can be defined by multiple points of view. Normally, the max speed is what the aircraft is capable of doing in level flight. There is also a published never exceed speed (Vne) which for the F-15E is expressed both as indicated airspeed and also Mach speed. This Vne speed is a structural speed limit, meaning even in a dive if you exceed this speed limit then you can experience structural damage on your aircraft. The reason for a Mach speed for Vne is that there is a point where under certain circumstances, the change of airflow over the airplane as it approaches Mach 1.0 can cause localized airflow disturbances and can cause structural damage on some aircraft, but this is more a problem for aircraft that are not designed for supersonic travel but have enough speed where it could reach transsonic speeds.

 

Ken

Thanks for the info, Ken--it seems the IRIS version isn't too far off. So then, what's the final say? Is it correct, or would I be better off tweaking the static_thrust and rated_N2_rpm variables?

This will help, right from the Technical Order -1.

 

There are 2 versions of the F-15E before '90 with the PW220 or the '90 and above with the 229 Engines.

By the time an F-15E got to full speed you'd be out of gas (or very nearly so) anyway.

 

The original design intent was for the F-15 to do M2.7+ but glass then wasn't as good as it is now and the big bubble canopy that gave the pilots the visibility they wanted couldn't handle the stresses at those speeds. So the Pentagon reduced the requirement to M2.3. Mach 2.3 wasn't enough though and in war games the F-15 had trouble intercepting M2.0 Concords and couldn't do a stern conversion intercept (coming from dead ahead or a slightly offset angle and falling in behind) at all because it didn't have the fuel capacity needed to keep the 'burners going long enough. Add in the fact that the Russian supersonic bombers can hit M3.0 which all but make them immune to F-15s or any other "legacy" fighter for that matter.

 

Enter the F-22 which I have always suspected is much much faster than what is let on, considering its engines dry thrust is somewhere between 22 and 25k lbs (vs 29k wet thrust per engine in the F-15). and wet thrust is "35k lb class" and back in the day it was slipped as being 39k per engine...something to chew on, the SR-71 had 32,500 lbs wet thrust per engine and darn near weighed twice as much full and ready to go.

 

Anyway, on topic...If any F-15 in regular operation ever exceeded M2.0 it would be a very very rare occasion. M1.3-1.6 is probably the top end in most circumstances.

This is not from the real manual... It even has spelling error in it. Is this how the game models the aircraft? If so it is very unrealistic and undermodelled. Eyeryone lets stop guessing and rather present facts shall we?. Manuals for both F-15C and F-15E are publicly avaible and declassified.

 

 

The real performance from the manual(1993 updated version with PW-229 engines):

 

 

 

You can clearly see that top speed at standard day clean aircraft with CFT is mach 2 not 1.6! And this is also at structural limit of the CFT. That is a huge difference in speed.