RAF Aircraft Role Designation
 

Why are some US sourced RAF aircraft given a UK role suffix, eg:
Sentry AEW1
Airseeker R1
Chinook HC2
Hercules C4
Poseidon MRA1

Whilst others retain their US prefix:
F-35B Lightning
MQ-9A Reaper
C-17A Globemaster

Those in the first part of your list are also described as E-3D, RC-135, CH-47, C-130J, P-8. The three of those in bold are used much more widely than their British names within the RAF at large. And the Airseeker is called a Rivet Joint by everyone I’ve ever talked to (admittedly none from 51 Sqn though). I don’t think there’s any rhyme or reason to it.

On F-35, can you imagine the confusion if the UK called the B “Mk1” and maybe later the A “Mk2”? Thankfully we don’t seem to have adopted that either!

I believe 51 are more used to referring to the "Replacement Bus Service".

The replacement aircraft for the Nimrod R1 was procured under "Project Airseeker", leading to the choice of the RC-135 "Rivet Joint. As such, the project people referred to the aircraft as "Airseeker" and the name somewhat stuck at various HQs. As you say, everyone calls it the RJ or Rivet Joint except just a few.

Remember European Helicopter Industries 01.... which Maggie mis-referred to as the EH 101...

I'm aware of this, I just wondered why some are allocated UK designators whilst others are not.

Ah, your OP seemed to suggest that the first group did not retain their US prefixes.

That doesn't explain the others, though. No idea on those.

Designation
 

It's a shame that the 'F-35B' is not known as the Lightning ll FGR Mk 1.
They made such a fuss about copying the old serial numbers from the English Electric Lightning for the new jets ...
We never called our Phantoms F-4K's or M's they had the 'proper' designation of Phantom FG Mk 1 and FGR Mk2.
I can only assume that brevity is best in a world where language seems to have sped up.
Accuracy and consistency seem to take second place now.

....ah, but what about the J's?

Not sure if or why it's referred to as a C-17A in RAF service. Boeing and the USAF just use C-17 and the proposed B version remained just that.

Edit: I've just seen reference to C-17A in American transcripts, perhaps the Americans dropped the 'A' when production ceased with just the one variant produced.

RAF designations have caused confusion in the past. I remember speaking to a somewhat perplexed defence attaché when trying to get last minute dip clearances for a Nimrod R1, Sentinel R1, and Shadow R1; he wondered why the same aircraft had three different names!

The F4Js were a short term lease - shorter than the C17s.

The Globemaster has always officially been the C-17A to the USAF, and the use of C-17 only is probably down to laziness.. I believe the last aircraft to enter US service without a variant suffix was the B-29. Every aircraft since has had an 'A suffix even if only one mark was ever used. Examples include the TF/F-102A, F-21A, B-2A and C-29A.

The reason given for not designating the F-4J(UK) as the Phantom F. Mk.3 was seemingly to avoid confusion with the Tornado F. Mk.3, which was not far away from entering service. I can't see the confusion myself; one was a highly capable, well armed interceptor and the other was the Tornado. Sorry, hat and coat etc...

I believe that the MoD recently officially dropped the 'II' in F-35B Lightning II.

I believe that the MoD recently officially dropped the 'II' in F-35B Lightning II.

Shouldn't it be the Lightning III ? Wasn't English Electric's world-beater, actually the Lightning II ? (Cue all the historians who will point out others before/after the P38)

UK Designations have always been about what the project team proposed and what their Airships accepted. There is usually a rational, but it's not always consistent! Until the C17, other than the F4J(UK) all US types in RAF service had traditional UK designators.

The F-4Js were not leased at all, they were bought outright...

-RP

I wonder how much it costs just to change the name of an aircraft in all of the technical documents and drawings that come with it.....

Some designations are directed from the Airships and yes it does mean the publications have to be reworked or have a front page added to explain the difference.

Agreed. The Sea King ASaC Mk7 was AEW Mk7 'till the last minute, when the RN insisted it be changed. The time to decide was when the configuration control change to the Mk number was agreed. Same with the 'Cerberus' name for part of the mission system. Purely an internal marketing device, which nobody in MoD had heard of until just before ISD. Not quite blank cheque time, but still costly. Companies sit on programme delays without telling MoD, hoping something like this will come along to give them breathing space.

The RAAF has gone the other way namely B737 AEW&C has been designated as E-7A Wedgetail and our A330 MRTT's as KC-30A's and our yet to be delivered Gulfstream 550 ISR birds are known as MC-55A Peregrine. This allows them to fit in easily in the US military database as known types. Many moons ago USAF exchange officers flying Mirage 111O had trouble entering their flight data in their system as the system couldn't take a name or abbreviation.

Yes it should, but as the Americans never flew the English Electric Lightning...