Most aviation buffs will agree that within the diverse realm of military aviation, one of the most interesting topics of discussion is aircraft that never were. No, when I say “never were”, I’m most certainly not referring to black aircraft that “don’t exist”. Rather, we’re talking about aircraft designs that barely made it to the prototype stage before getting canned, or worse- they never left the drafting table before the project/concept was scrapped in favor of some other program. The 1970s, in particular, bore a few examples of a bunch of aircraft that never were. Let’s briefly talk about one of them.
The early ’70s saw the United States Navy test the Grumman F-14A Tomcat as a carrier-based fleet defense fighter; the eventual complete replacement for their F-4 Phantom IIs. However, the first problem with the Tomcat that immediately blew into the spotlight (other than its engines which had a nasty habit of stalling during certain maneuvers) was that it was a very costly aircraft. Granted, it fulfilled the needs of the VFX (Naval Fighter Experimental) Program almost perfectly, and looked every bit the part of an air superiority fighter that could actually live up to what Grumman promised it could do. However, money and budgeting has constantly been a concern of many a one-star admiral and above. That’s why in the early ’70s, the Navy very briefly entertained an interesting proposal from McDonnell Douglas. The aircraft they offered would function as an alternative to the costly, heavier and “riskier” F-14 Tomcat. It wasn’t an upgraded Phantom, McDonnell Douglas’ most successful fighter at that point in history, nor was it a clean-sheet design. In fact, the fighter jet MD executives offered the Navy was none other than the F-15 Eagle, then still being tested and developed prior to its integration into the United States Air Force’s inventories.
At a first glance, the aircraft bore no drastic visual departures from the F-15A. It looked very similar, right down to the inclusion of a tailhook which was standard on the Eagle for short-field arrested landings (especially in emergency situations). However, the Eagle needed to be navalized. For storage in close proximity to other aircraft on the flight deck of an aircraft carrier, and for closed storage inside the massive hangar bays of a carrier, the wings would have to be shorted. Since this was impossible to do with the Eagle, the naval version would instead feature folding sections of the wings (a little more than 15.4 feet on both wings) that would lift up into right angles. That solved one problem. The next was the fact that carrier landings are usually very rough on an aircraft. Essentially a very highly-controlled crash, trapping aboard a carrier involves hitting the deck with your wheels and hopefully snagging one of three or four wires stretched across the angled deck. Added to the mix is the roll of the ship (it’s in the middle of the ocean, a bit of swaying is to be expected), and weather conditions. So instead of leaving the navalized F-15 with the Eagle’s original landing gear, McDonnell Douglas promised that if the jet was selected for further development, they’d redo the gear so that it could accommodate violent carrier landings with ease. Third was the tailhook. Yes, the land-based Eagle already came with one stock, but the naval variant would get an even stronger hook, as it would be used far more frequently than the regular F-15’s tailhook. It would have a higher rate of climb, max speed and combat range than the F-14A too. McDonnell Douglas engineers christened the proposed jet the F-15N Sea Eagle (I like to call it Seagle).
The Seagle, however, was afflicted with with a slew of issues that virtually doomed it from the get-go. The Navy (obviously in hindsight) found it less than satisfactory, and judged that the aircraft design failed to meet certain requirements that weren’t actually set for the hypothetical acquisition of such an aircraft, especially considering that the Navy was already gearing up to buy the Tomcat as their fleet-wide solution. Among the most glaring of these issues was the substantial weight of the jet. That, and the aircraft couldn’t carry the AIM-54 Phoenix, a missile the Navy felt showed considerable promise when paired up with the appropriate jet (namely the Tomcat). Temporarily undeterred, McDonnell Douglas got its engineers back to their drafting tables. The redesigned bird was deemed the F-15N-PHX, which would be able to carry (and deploy) a full load of Phoenix missiles. Once again, weight became an issue. The added weight of the missiles to the already-heavy jet would likely have had a significant negative impact on the combat performance of the aircraft, making it a far less feasible fighter to the F-14. The F-15N and F-15N-PHX never made it off the blueprint sheets, instead dying a very quick death after a Senate review in 1973.