The MR23, the last Canberra.

[PR19_Kit]

The BAe Canberra MR23

During the 80s, the RAF Maritime Patrol squadrons were flying the Nimrod MR2 and in general were very pleased with the aircraft and it's performance. Based at RAF Kinloss and RAF St. Mawgan the units patrolled well out into the Atlantic and way up north toward Spitsbergen sniffing out any and all submarines and surface craft that came their way. The Nimrod's airframe was developed from that of the Comet 4, designed in the late 50s, and even though the prototype Nimrod flew in 1967, some 10 years after the Comet 4, many of its design aspects still mirrored that of the early jetliner. The RAF, being only too aware of this, started a programme to either replace or update the Nimrod fleet, which had now all been modified to the much more capable MR2 version.

In the interim the demands of the continuing skirmishes around the Falklands, even though the Argentinian invasion had been thrown back in June '82, meant that a large proportion of the Nimrod fleet were engaged in patrolling the Total Exclusion Zone around the Islands, and their flying hours were being depleted rapidly, especially as they had to transit back to UK for anything other than routine servicing. The demands of our NATO commitment to our partners in the North Atlantic zone did not balance the available aircraft in the Northern hemisphere and so a search was begun to find a short to medium range replacement that could offload the Nimrods.

As on many previous occasions, the answer was a Canberra. While that venerable aircraft, in any of its many versions, was not immediately suitable for the task, and while there were many airframes still in squadron service, it was considered that by mixing and matching components from various Marks, and by using hardware from other Services as well, a suitable compromise could be reached.

The latest Canberras in service were the photo-reconnaissance PR9s, but there was a pool of this particular mark available at various Maintenance Units and elsewhere. Six PR9 airframes, all with moderate flying hours logged, were gathered from various sources and transferred to Marshall Aerospace at Cambridge Airport for conversion. This turned out to be a major operation as the MoD's demands changed frequently during the build programme, but the result , to become known as the Canberra MR23, eventually turned out to be excellent for the tasks desired.

The heart of the MR23 update was the ex-Fleet Air Arm Blue Fox radar, normally fitted to the Sea Harrier FRS1. The sets for the Canberra update were taken from spares stocks, and during the first Falklands War had shown an excellent air-to-surface capability. The radar was mounted in ex-Canberra T11 and T19 radar trainer nose cones, many of which were freely available as the these aircraft had been out of use for some time.

Of course this prevented the use of the PR9 navigator's usual nose position, and so he was moved rearwards to the position used in the earlier bomber Canberra variants, some feet behind and below the pilot. However, as the PR9's camera bays had been replaced by bomb-bay sections from the B(I)8 intruder variant, complete with that aircraft's 4x ADEN cannon belly pack, plus the addition of the radar monitoring system, the navigator's position was displaced upwards by a foot to two, which required more headroom.

In order to accommodate this yet another 'old stock' item from the Fleet Air Arm was called back into use in the shape of the Sea Vixen Observer's hatch, resulting in the characteristic bulge in the top of the fuselage. The later transparent hatch cover was not used on the MR23 into order to improve the Navigator's view of the radar system. Entry to the Navigator's position was via the original equipment bay hatch on the starboard side as the systems previously located in that bay had been removed in the upgrade process. As the Navigator's position occupied the space of two of the PR9's fuselage fuel tanks, this compromised the MR23's range and tip tanks were a standard fit, as well as a nose mounted flight refuelling probe, offset to starboard rather like that of the Buccaneer. This resulted in the patrol endurance being limited to that of crew rather than the aircraft's fuel load.

The PR9.s Avon RA27 engines were very powerful and optimised for ultra-high altitudes, but with a modified fuel control system, supplied by Smiths Industries, they gave adequate power and fuel consumption for the low level, anti-submarine tasking that was to be the new aircraft's major work. While not being able to shut down 50% if its power, as could the Nimrods, at low throttle settings the updated Canberra was calculated to have an endurance of some 5-6 hours on its reduced internal tank capacity, and with the aid of the RAF's fleet of Victor, Vulcan and VC-10 tankers, this could be extended almost indefinitely.

The sensor suite was enhanced by the addition of a long tail mounted boom containing a MAD system, sideways looking radar and the PR9's displaced rear radar detector head. This produced the longest Canberra variant ever, being some 77' 4" from nose to tail. During the prototype's trials it was found that at the low speeds expected during patrols the radar unit and other nose mounted equipment tended to overheat, and an enhanced air conditioning unit was fitted, fed by two cheek mounted air intakes, resulting in a nose aspect rather similar to that exhibited by some USAF B-57 variants.

The MR23 was to carry a heavy weapons load, the PR9's normal under-wing pylon positions being used to carry Sea Eagle missiles via Buccaneer pylons. The outer wings had the outboard pylon positions added, this configuration previously having been used with the Akrotiri Strike Wing B6s and also on the TT22 target tug variants. The outer positions were used to carry ECM pods and sometimes Sidewinder missiles for a limited self defence capability, although in later life the MR23s frequently carried an ALAARM anti-radar missile to counteract any surface vessel operated AA radar. The forward bomb bay could carry two Mk 46 air launched torpedoes or any other suitable small weapons.

The starboard tip tank was fitted with a remotely trainable searchlight in its forward half for use during night attacks, and this tank, together with its port side partner, was not capable of being jettisoned under normal circumstances, unlike previous Canberra variants.

By mid 1987 all six MR23s had been converted and anew Squadron, 204, was formed to operate the type. 204 had last been operational some 15 years previously flying Shackleton MR2s in the ASR role from RAF Honnington. This time 204 was to fly from RAF Macrihanish on the Mull of Kintyre, and the six re-built Canberra's were delivered there by Marshall pilots while the Squadron's crews were being trained at RAF Wyton and NAS Yeovilton.

Over the next few months 204 worked up its aircraft and crews and was declared operational on November 12th 1997, and promptly took over the short and medium range patrol tasks from its partner Nimrod squadrons based at Kinloss on the opposite coast. In service the MR23 proved remarkably capable for a stop-gap system, and showed good value for money considering that almost none of the component parts used in the upgrade were bought new.

The Squadron normally showed a very low public presence, being based at one of the UK's more obscure airfields, and with its aircraft normally operating out of sight of land. With so few MR23s available 204 rarely took part in flying displays, but this was changed for the 1998 RIAT display at Fairford as this year was the 80th Anniversary of the Squadron first being formed on April 1st 1918. Accordingly one of the MR23s, XH166, was re-painted in the white and grey scheme carried by its Shackletons, together with a large '204' on the fuselage side. A large '80 Year' badge was carried on the rudder and in this form XH166 gave a spirited display during the weekend. This was all the more remarkable as the aircraft carried a full weapon load during the display!

204 continues to fly its vintage fleet to this day, and together with No. 39 (1PRU) Squadron at RAF Marham flying the last PR9s, are the last two Canberra units in the RAF.

[See http://www.whatifmodelers.com/index.php/topic,23243.0.html for the model build]

[kitnut617]

Wonderful model and a first rate backstory 

[The Rat]

  Looks perfectly natural!

[Daryl J.]

Better be careful, there.   You'll wind up having this backstory quoted elsewhere on this crazy webnet and having it appear in text to be repeated into history's permanent future.     

The story pulls of without one glitch.   Excellent.



Daryl J.

[PR19_Kit]

Daryl,

Indeed, it occured to me after I'd posted it that there's no 'model story' at the end, so no-one has to try very hard to make it 'real'.

Luckily I haven't stored the thing in a museum somewhere, unlike the PR19!

[McColm]

Great back story,  you'd be surprised just how real your idea became a reality during one of the NATO 'paper exercises '. The what if we used those ...? Followed by ' that's a great idea, let's try it '. Only to be implemented 8 months later in a 'live exercise' just to see if it can be done.