The F-15N is purchased by the US Navy

[insidersource]

I will set the scenario with the following.

May 1968 the Armed Services committees of Congress voted to fund production of the F-111B. Justification was an urgent need of the Vietnam war for a long range escort for attack aircraft. The F-14 will no longer exist now that the F-111B has been purchased.

1970
The F-111B enters the Vietnam war and the powerful AWG-9 radar provides exceptional situational awareness. Ground attack aircraft now receive warning of incoming migs and the US losses are reduced.

1971
The AIM-54 Phoenix missiles prove to have a very low kill ratio.

1972
Four F-111B operating over North Vietnam get ambushed and shot down by a pair of Mig-21. It sends shock waves through the Navy.

1973
The Navy initiates the NASF program. Navy Air Superiority Fighter program. F-15 is now in flight testing and is instantly short listed. F-111B production is capped at 200 aircraft.

1974
The single seat F-15N prototype flies with strengthened landing gear, blown flaps and wing folding mechanism.

1975
The US Navy, USAF and UK initiate the advanced active sparrow missile program. The active radar seeker under development for the British Skyflash version of the sparrow would be paired with an extended motor creating a 600lb missile with 50% greater range than the latest sparrow version. This solves the problem of the Phoenix missile being too large for the F-15 and the Sparrow being too short ranged.

1976
The US Navy selects the F-15N with APG-63 and the advanced sparrow missile combination.

1977
First production F-15N delivered to the US Navy.

1978
The F-15N enters service with the advanced active sparrow.

1979
The US Navy F-111B fleet gains bombing capability to provide long range strike with self escorting capability.

I think the F-15N would have also prevented the Hornet from ever existing. The single seat F-15N would have been much cheaper to purchase and operate compared to the F-14. Most of the requirement for the Hornet was driven by wanting a cheap aircraft to sit under the expensive F-14. I think the single seat F-15N would have eventually gained multi-role capability to replace the A-7 fleet.

Today instead of the Navy having carriers full of Super Hornets they would be full of Navalised Eagles

 

[Manuducati]

I don't see the F-15 being easily turned into a carrierborne fighter.
I know the proposal of course, but the narrow path landing gear, the amount of modifications (nose landing gear, arresting hook, reinforced structure) the basically new wing (blown flaps, folding, leading edge flaps), replacing every electronic component not compatible with the carrier electromagnetic emissions, or not salty environment resistant, replacing the ejection seat, and given the poor reliability of early P&W F100 engines...
Those thinking the F-15N progran would have been smooth, easy and far less maintenance heavy than the F-14 one are dreaming I'm afraid.

 

[Hamez_boi]

P&W F100 engines...

would you be happier if the F-15N used F401 engines if in this scenario they actually went into production?

 

[Manuducati]

would you be happier if the F-15N used F401 engines if in this scenario they actually went into production?

That's not a possibility as the F401 was physically larger than the F100.

 

[Sferrin]

The USN already ran the numbers, and it came up short against the Tomcat.

 

[insidersource]

The USN already ran the numbers, and it came up short against the Tomcat.

This is why I changed a single point in May 1968. The F-111B production is approved meaning no Tomcat. The Navy now has to run the numbers of F-111B versus F-15N

The US Navy ran the numbers and determined the F-15N could not use the AWG-9 radar and heavy Phoenix missiles without a cleansheet design of the F-15. The shorter range and semi-active Sparrow missiles were deemed insufficient for the Navy.

This I mentioned the advanced active sparrow missile program as a key point. This improved missile would satisfy the Navy requirement while allowing the lighter APG-63 to still be used.

 

[Kiltonge]

The F-15N was intended as a supplement to the F-14A, not a replacement. There were over 80 F-14s already in the Fleet when the 15N was being studied.

The F-15N, believe it or not, was a 'low' tier proposal alongside various austere F-14s to bulk-out the inventory when the Navy thought it was going to have to stop procurement of the F-14A at around 300-ish. The Navy was seeking funds for a fly-off between austere F-14 and F-15N, which were never granted, but some of the cost-reduction proposals did reduce the F-14A unit price and allowed further procurement.

Had the F-15N entered service it would have prevented the F/A-18 having to be developed.