Would we be able to fly with 'clean' CFT?

[Nahen]

6 hours ago, Mig Fulcrum said:

As far as I know razbam is doing the -220 engines version, am I wrong? I assume it only by the pics they posted, not sure if they specify somewere these info.

We write in the thread about CFT tanks without pylons for armament - that is, we write about fiction in the DCS world and even more about fiction in the real world. So when I writing about the power to weight ratio, talking about the real F-15C and F-15E. I added, in case you didn't notice, that depending on the version of the F-15E, it doesn't necessarily have lower power-to-weight ratio than the F-15C. Something's wrong ?

[Spurts]

2 hours ago, Nahen said:

Empty F-15C airframe mass 12,701 kg (28,000 lb)
Empty F-15 E airframe mass 14,379 kg (31,700 lb)

2 × F100-PW-220 thrust: 14,590 lbf (64.9 kN); 23,770 lbf (105.7 kN) with afterburner

2 × F100-PW-229, thrust: 17,800 lb dry (79 kN); 29,160 lb (129.7 kN) with afterburner

 

This is exactly the point I was trying to make in my first post.  I have documents I cannot post here because of forum rules (TO 1F15A-1 postJan84 and TO 1F15E-1 Apr93) saying F-15C MSIP I weighs 29,500lb empty and F-15E weighs 34,600 empty with no CFT, and I have seen this document for F-15C MSIP II with a weight of over 30,000lb.  You are using the wrong weights, likely because those are easy to find numbers.

[Mig Fulcrum]

6 ore fa, Rainmaker ha scritto:

-229s.

The C's radar, non-AESA at least, is certainly not better than an E's FWIW.

To be clear, I could care less about the whole CFT debate, just clarifying certain points.

Yeah I couldn't care less too but just to point out what you point out.

F-15E (non AESA) - AN/APG-70 (F-15C uses this radar from late '80s, just about when the E came out)

F-15C (in DCS) - AN/APG-63(V)1 (the radar the USAF start using from early 2000s)

Edited November 29, 2022 by Mig Fulcrum
Typo

[Rainmaker]

19 minutes ago, Mig Fulcrum said:

Yeah I couldn't care less too but just to point out what you point out.

F-15E (non AESA) - AN/APG-70 (F-15C uses this radar from late '80s, just abount when the E came out)

F-15C (in DCS) - AN/APG-63(V)1 (the radar the USAF start using from early 2000s)

 

The V1 was still not as good, no. It was a stop gap upgrade. It used some of the -70s parts to do that. It still was not any greater. 
 

In addition, DCS is most certainly not modeling the V1…properly anyway. 

Edited November 29, 2022 by Rainmaker

[Nahen]

2 hours ago, Spurts said:

This is exactly the point I was trying to make in my first post.  I have documents I cannot post here because of forum rules (TO 1F15A-1 postJan84 and TO 1F15E-1 Apr93) saying F-15C MSIP I weighs 29,500lb empty and F-15E weighs 34,600 empty with no CFT, and I have seen this document for F-15C MSIP II with a weight of over 30,000lb.  You are using the wrong weights, likely because those are easy to find numbers.

Well, where would I check, the mass of the EMPTY AIRFRAME in the E version is 31,600 - 31,700 lbs ... And the F-15C, regardless of the version - I don't know if you know, but the MSIP modification is a modification of the avionics, radar, etc., and not the airframe structure - neither wants to be anything other than about 28,500 - 28,600 lbs. So I don't know what data you have... Maybe you're talking about operational weight? With fuel? The difference in weight between the F-15C and F-15E structural airframe is "only" less than three tons, no matter how you search, you won't change it.

Internal fuel capacity
F-15C 2,070 US gal (7,836 liters)
F-15E 2,019 US gal (7,637 liters)
F-15C, max internal and external capacity
5,400 US gal (20,441 liters)
F-15E, two CFTs and 3,610-US gal (2,304-liter) tanks
5.349 US gal (20.246 liters)

weights

Empty
F-15C 28,600 lb (12,973 kg)
F-15E 31,700 lb (14,379 kg)
F-15C interceptor with four Sparrow AAM
44,630 lb (20,244 kg)
max takeoff
F-15C
with three 610-US gal (2,309-liter) drop tanks
58,470 lb (26,521 kg)
with four Sparrow, four Sidewinder, and full CFT
59,500 lb (26,989 kg)
with CFT and external tanks
68,000 lb (30,845 kg)
F-15E 81,000 lb (36,741 kg)

[Cab]

On 11/4/2022 at 4:59 AM, foxmagnet said:

CFT is a huge feature of F-15E and  it is what enables our 'beagle' carry a bunch of munitions. However in A2A configuration, protruding bomb rack are nothing but drags.

So I am wondering if we are not flying with any weapons mounted on CFT, can we fly with clean, rackless CFT?

 

Unfortunately, no. Razbam has apparently said they would not be modeling this.

The preverbal "juice" would not be worth the squeeze because it would essentially require a different flight model. 

Edited November 29, 2022 by Cab

[Spurts]

28 minutes ago, Nahen said:

Well, where would I check, ...

I already told you.  I am looking in the beginning of the performance section of the USAF flight manuals.  Empty Weight.  No fuel, no crew, no CFT.  There is no data source more credible excepting an individual airframes unique weight and balance sheet.  And Avionics do add weight.  

I am not claiming your initial claims were made in bad faith, just that you had incorrect starting data.  15 years ago I would have used the same weights you did.

[Nahen]

36 minutes ago, Spurts said:

I already told you.  I am looking in the beginning of the performance section of the USAF flight manuals.  Empty Weight.  No fuel, no crew, no CFT.  There is no data source more credible excepting an individual airframes unique weight and balance sheet.  And Avionics do add weight.  

I am not claiming your initial claims were made in bad faith, just that you had incorrect starting data.  15 years ago I would have used the same weights you did.

So in the last 15 years suddenly the F-15C, out of production for 37 years, changed its weight? Pretty interesting theory...

 

Maybe show a scan of this manual because, to my knowledge, it is the only study in which there are different airframe weights than those provided by the manufacturer and any other sources ... The weight of the E J, I, SLAM and other versions may be different than the pure F-15C due to, perhaps , modifications such as those in Israeli aircraft. But it still doesn't change anything in the case of the C version. Just like in the E version, the airframe structure as such changed only in the production process of this version and redesign - strengthening the structure of the fuselage, wings, and this changed the weight by less than three tons. I dare to assume that if the weight of the airframe itself changed so drastically, then the F-15E would certainly have much more powerful engines than those they have today.

Edited November 29, 2022 by Nahen

[Spurts]

1 hour ago, Nahen said:

So in the last 15 years suddenly the F-15C, out of production for 37 years, changed its weight? Pretty interesting theory...

 

I never said that.  I have been very clear that my sources are what have changed.  I also explained that scans of the manuals cannot be posted due to forum rules.  Also, if a plane goes out of production 30 years ago then gets new wiring, new radar, new mission computers, new EW suite, etc, the weight is going to change.

I am not trying to attack you, so I don't understand why you feel the need to attack me.

[Nahen]

2 hours ago, Spurts said:

I never said that.  I have been very clear that my sources are what have changed.  I also explained that scans of the manuals cannot be posted due to forum rules.  Also, if a plane goes out of production 30 years ago then gets new wiring, new radar, new mission computers, new EW suite, etc, the weight is going to change.

I am not trying to attack you, so I don't understand why you feel the need to attack me.

I'm not attacking you, but my whole life is connected with technical professions, design, measurement, etc. And there is no way that replacing the wiring, radar, on-board computers, even fuel transfer systems in the airframe will change weight by the value about you write. Despite everything, I bet that this instruction is either burdened with errors or gives data that is classified differently. Let me repeat - the difference in weight between the F-15C and F-15E airframe does not exceed three tons. As far as I remember, the F-15EX is heavier by about 3.5-4 tons. But here the structure of the wings is even more strengthened.

[Spurts]

4 hours ago, Nahen said:

the difference in weight between the F-15C and F-15E airframe does not exceed three tons.

On this we are agreed, we just have different data for the starting point.  I am willing to leave it at that.

[Scott-S6]

14 hours ago, Cab said:

Unfortunately, no. Razbam has apparently said they would not be modeling this.

The preverbal "juice" would not be worth the squeeze because it would essentially require a different flight model. 

 

They'd also need data to build that flight model and an expert with plenty of time flying an F15E with no CFT to validate it. That is tricky, to say the least.

[Nahen]

15 hours ago, Spurts said:

On this we are agreed, we just have different data for the starting point.  I am willing to leave it at that.

Well, even if the weight of the F-15C is different and the F-15E is less than three tons heavier than it, even if the F-15C weighs 100 tons, the power-to-weight ratio for the F-15E with 229 engines will still be higher. The weight of the F-15C doesn't matter, but the difference between C and E in weight and engine thrust. So whether it's 15 tons and 18 tons or 150 tons and 153 tons, the power to weight ratio will always be higher for the F100-PW229 versions of F-15E.
So versions of the F-15E with 229 engines have a higher power-to-weight ratio than the F-15C.
Of course, this whole dispute is purely academic, because in practice the F-15E is always MUCH HEAVY than the F-15C.

[bies]

No. RAZBAM stated CFT will be permanently mounted. I'm perfectly fine with that. It's a strike aircraft and it always had CFT in combat. Making fictional Thunderbirds air show doesn't justifies coding additional FM.

BTW: Maneuverability is far more about wing loading. Not T/W ratio. What is more if 2 have similar T/W but one has significantly higher wing loading it will need bigger AoA for the same G wasting its effective T/W through fighting bigger drag. Let alone additional drag of CFT.

[Nahen]

18 minutes ago, bies said:

No. RAZBAM stated CFT will be permanently mounted. I'm perfectly fine with that. It's a strike aircraft and it always had CFT in combat. Making fictional Thunderbirds air show doesn't justifies coding additional FM.

BTW: Maneuverability is far more about wing loading. Not T/W ratio. What is more if 2 have similar T/W but one has significantly higher wing loading it will need bigger AoA for the same G wasting its effective T/W through fighting bigger drag. Let alone additional drag of CFT.

This is not about removing the CFT from the plane. The question was whether the CFTs could be "bare" - without pylons for armament. Smooth and streamlined like an ass. But it was probably clarified pretty quickly that the pylon mounts are an integral part of the CFT.