RyanCrierie said:
Yet, when it came time to designate the F4H Phantom II in the USAF series, it was assigned the designator F-110A Spectre, instead of F-109A Spectre. So what's with the skipping?
I don't know the final answer to this question, and I think that apart from those who "were there" at the time, nobody knows
.
What I
do know, though, is that the USAF apparently had no fixed policy about skipping of disapproved or cancelled designations. E.g., the original designations C-137 (YC-137 became YC-97H), F-104 (XF-104 became XF-98A) and F-106 (XF-106 became XF-84H) were all cancelled and their numbers later re-used for other projects (twice in case of C-137!). On the other hand, in the Q-series of target drones, the requests for slots Q-7, Q-8 and Q-11 were disapproved and the numbers
not used afterwards. Another disapproved and non-reused slot is C-139.
One might think that a number is re-used, if it is still the next-in-line when a new request for designation comes in (i.e., the disapproval process has not taken so long that the following number in the series has already been assigned). This is a policy which was sometimes followed by DOD for the post-1962 joint system. But there are several counter-examples for this in pre-1962 USAF allocations - e.g. the F-106 gap was refilled with F-106A in 1956, while the F-107A designation had been allocated in mid-1954!
Things get even more complicated, because there was apparently a very short-lived (~ 1954/55 time frame) USAF/Navy agreement, that the Navy would use even-numbered slots in some (or all??) USAF designation series. Because the idea never took off, it led to gaps for at least H-36/38 and C-134/136/138. Some of the gaps were later filled by more or less "open" projects (C-134/136), some by
very obscure ones (H-36/38), and C-138 remained unassigned. There is circumstancial evidence that the "even-numbers-for-Navy" scheme was briefly applied to the F-series as well:
- When F-107A was allocated in 1954, the F-106 slot should have been available, because I
think the XF-84H had been redesignated by then (however, I can't find hard evidence for this right now).
- A McDonnell proposal for a two-seat interceptor version is labeled "F-109". The proposal must be from around 1955, when the F-108 slot was definitely not yet assigned.
Anyway, all this might be interesting (or not ;D ), but doesn't directly address your question about the F-109
. Well, I
guess(!) that the skipping of F-109 has something to do with the "visibility" of Bell's effort to have the F-109 designator approved. Other cancelled designations like XF-106 etc. were very short-lived and probably not widely known throughout the Air Force, let alone the general public. On the other hand, as far as I know Bell openly used the F-109 designation even though it hadn't been approved by the Air Force. So
maybe the idea "F-109 = Bell D-188A VTOL" had been spread a bit too much, so that it was deemed confusing if the F-109 slot would be used for a completely different projects later.
An alternate explanation would be a change in general policy from "fill the gaps" to "always advance to next number" around 1960 or so. Supportive evidence for this are the designations C-140 and Q-12, which were allocated in 1960 or later. In both series, the preceding number had been disapproved, was therefore available for allocation, and was definitely
not "well-known" in any sense of the word (in fact, I never saw SC-139 and XQ-11 anywhere before they turned up in my own research
).
So, bottom line is ... I don't know why the USAF Phantom didn't become the F-109A - but I sure can speculate about it ad nauseam! ;D
