F-15A: Prior to Not a Pound for Air to Ground

[KJ_Lesnick]

I have two questions. 

• How much heavier would the plane have been before they stripped it of air-to-ground capability?
  
• How much air to ground ordinance was it designed to carry initially?
  

I'm not interested in the politics in regards to why they stripped it of air to ground capability, merely how much heavier it would have been empty, and how much bombs could it carry?

[PR19_Kit]

At risk of producing and ENDLESS discussion on this point, I always thought the -15 was originally designed solely as an air superiority fighter. Only later was the air-to-ground capability added, which resulted in the F-15E.

[scooter]

At risk of producing and ENDLESS discussion on this point, I always thought the -15 was originally designed solely as an air superiority fighter. Only later was the air-to-ground capability added, which resulted in the F-15E.

It was only after some enterprising AF test pilots saw the potential for a WSO and bombs on the B, did MDD bring forth the Mud Hen

[Captain Canada]

Doubt it would have been much heavier empty....as for the weapons load you'd need to know what they were considering for hard points. I'm assuming the weight would be similar to what the Strike Eagle is now ? Without the conformal tanks I'd presume....

[KJ_Lesnick]

PR19_Kit

1.) I don't intend to produce an endless discussion -- I'm actually trying to avoid that that's why I specified a lack of interest in politics merely keeping the topic on weight.
 
2.) When the F-15 was being conceived (before it flew), there was an intention to have air to ground stores on it (You have to keep in mind that it was designed to replace the F-4, and while the desire was to make it far superior to the F-4, it still was to have some air-to-ground capability).

3.) I've seen many early drawings of the F-15 on Secret Projects which depicted the plane carrying drop-tanks and bombs.

[tinlail]

I don't think there was ever a literal concern about A2G adding a bunch of weight to the aircraft, but rather a concern for cost, and schedule.

[KJ_Lesnick]

Tinlail

So, the weights weren't really a concern?

I'm looking at the weight figures for the F-15A and assuming they're right, I get the following

• OEW: 27,000 or 27,100 lbs
  
• Fuel: ~11,000 lbs
  
• Gross Weight: 38,100 lbs
  
• MTOGW: ~56,000 lbs
  

That yields a maximum load of 17,900 pounds, and assuming you were carrying the typical 4 x AIM-9, 4 x AIM-7 you'd have a 15096 to 15480 pounds remaining: For most intents and purposes you'd have 15,000 pounds of payload + 4 x AIM-7 & 4 x AIM-9.

This of course provides you have the pylons to haul all that stuff, but theoretically it works out. 

Regardless, the plane does have the means to carry 3 x 600 or 610 gallon tanks which brings you somewhere between 11,790 and 12,078 pounds (600 or 610 gallons; and how much each gallon weighs in at: I've heard 6.55 and 6.6).

[Gondor]

Early drawings for the F-15 in an air to ground mode had an extra pylon under the outer wing and carrying some ECM pods.

Gondor

[KJ_Lesnick]

Early drawings for the F-15 in an air to ground mode had an extra pylon under the outer wing and carrying some ECM pods.

Didn't that pod have some kind of flutter problem?

[Talos]

Tinlail

So, the weights weren't really a concern?

I'm looking at the weight figures for the F-15A and assuming they're right, I get the following

• OEW: 27,000 or 27,100 lbs
  
• Fuel: ~11,000 lbs
  
• Gross Weight: 38,100 lbs
  
• MTOGW: ~56,000 lbs
  

That yields a maximum load of 17,900 pounds, and assuming you were carrying the typical 4 x AIM-9, 4 x AIM-7 you'd have a 15096 to 15480 pounds remaining: For most intents and purposes you'd have 15,000 pounds of payload + 4 x AIM-7 & 4 x AIM-9.

This of course provides you have the pylons to haul all that stuff, but theoretically it works out. 

Regardless, the plane does have the means to carry 3 x 600 or 610 gallon tanks which brings you somewhere between 11,790 and 12,078 pounds (600 or 610 gallons; and how much each gallon weighs in at: I've heard 6.55 and 6.6).

He's right, it isn't really a concern. You aren't going to be lugging around bombs every mission. When you are, it's going to be a dedicated strike mission and they will jiggle the payload/fuel around a bit to suit it. The F-15A could carry dumb bombs and rockets from the start, after all. All it needed was a few, simple A2G modes for the CCIP to show it where they would land.

Early drawings for the F-15 in an air to ground mode had an extra pylon under the outer wing and carrying some ECM pods.

Gondor

The pylon mounting structure is still there, as I recall, just not used. There's a picture of an F-15C mocked up with a pair of HARMs hanging from it floating around. From what I remember, the recent Saudi F-15SAs they bought have the two extra pylons reactivated.

[KJ_Lesnick]

He's right, it isn't really a concern. You aren't going to be lugging around bombs every mission.

Plus, truthfully the USAF had several aircraft that were better suited to the air to ground task than the F-15 was, including the F-111 and A-7.  Both could do interdiction missions just fine, the A-7 could do a good job with CAS (when the USAF cared about it at all). 

They'd probably be better off with the F-15's handling the air-superiority and these aircraft doing the mud-moving.  Generally it seems more practical to use an F-15 down low when you can't use an F-111 or A-7.   

The F-15A could carry dumb bombs and rockets from the start, after all. All it needed was a few, simple A2G modes for the CCIP to show it where they would land.

Makes sense

The pylon mounting structure is still there, as I recall, just not used.

Oh, I thought there was some flutter issue.  I guess not...

There's a picture of an F-15C mocked up with a pair of HARMs hanging from it floating around.

The F-15C had air to ground capability from the outset -- up to 20,500 pounds of bombs

From what I remember, the recent Saudi F-15SAs they bought have the two extra pylons reactivated.

Are they structurally strengthened over the originally F-15A

[Daryl J.]

I spoke to a weapons loader for the F-15 not long ago and he felt the reasons for stations 1 and 9 being unused were they were very limited in capacity, that the ECM pods designed to be carried there were obsoleted very early in development.  He was unsure if they were still wired out to the station.   If memory serves correctly, he said the Saudi wing is strengthened and will be able to carry about a 100 lb load after pylon and other weight is considered.

[KJ_Lesnick]

Daryl J.

I spoke to a weapons loader for the F-15 not long ago and he felt the reasons for stations 1 and 9 were that they were very limited in capacity, that the ECM pods designed to be carried there were obsoleted very early in development.  He was unsure if they were still wired out to the station.   If memory serves correctly, he said the Saudi wing is strengthened and will be able to carry about a 100 lb load after pylon and other weight is considered.

I'm actually very impressed with the detail of your research: Thank you

[ajmadison]

After reading _Boyd_ the very bureaucratic Air Force upper management had a bad habit of allowing unchecked mission creep. As much as the Century class of fighters broke new ground in terms of aeronautics, look how each fighter gained weight and more top end, but to the point where they couldn't out maneuver a super tanker. And F-106 doesn't really count. F-102 started out as a Soviet Bomber interceptor, and kept that mission until it was re-cooked as the 106. _Boyd_ describes how, something as simple as a retractable foot step then causes a change in aircraft wheel up time, which causes additional avionics requirements, which makes the plane heavier, which shortens its range, so more fuel volume is added, which puts the wing loading out of spec, so the wingspan is enlarged, until the jet fighter has become the 767.

So a motto helps keep everyone focused on the airplane's most important mission.

[PR19_Kit]

Why does a retractable foot step slow down the wheel retraction time?