Armstrong Whitworth Argosy AW 650/660 Series

The Armstrong Whitworth Argosy AW 650/660 Series

This paper is a brief history of the Argosy AW 650/AW 660 Series of transport aircraft designed and built by Sir WG Armstrong Whitworth Aircraft Limited, Coventry.  As it transpired the Argosy Series were to be the last aeroplanes designed and manufactured by Armstrong Whitworth Aircraft (AWA) at Coventry.

With the appointment of ED Keen as AWA’s Chief Designer in 1955, to replace his predecessor HM Watson, the company started to consider the possibilities of designing a military transport aeroplane to meet Air Ministry Operational Requirement OR 323. The machine was designated the AW 66.  At first the Air Ministry showed considerable interest, but this evaporated in 1956 when government funding was withdrawn and the project was discontinued.

However, with the financial support of the large Hawker Siddeley Group, of which AWA was an important constituent member, it was decided to proceed with a similar aeroplane designed for the civilian market. This was initially allocated the type number AW 65, but subsequently changed to AW 650.

AWA embarked on a considerable amount of market research to ascertain what the civil aviation market actually wanted, particularly the air freight business. Short turn-round times, ease of loading /unloading and medium haul operation seemed to be among the major requirements. To help meet the requirements of rapid turn-rounds and ease of cargo handling the Company developed their “Rolomat” System, enabling palletised loads to be moved almost effortlessly within the aircraft’s fuselage. AWA therefore proceeded to design an aeroplane to satisfy most of these needs.

To maximise the rapid loading and unloading of cargo, a twin tail boom arrangement was adopted for the projected freighter. This gave good access and opened up the possibility of simultaneous loading and unloading. The twin boom layout was not a totally new concept and had been used before, notably on the wartime Fairchild Packet /C119 Boxcar and subsequently on the French Nord Noratlas. Both these aircraft, however, were twin piston – engine machines and the AWA proposal differed significantly in that it was a larger aeroplane powered by four gas turbine turboprops.

Anyone who has read Elleston Trevor’s gripping novel, “Flight of the Phoenix” or possibly seen the film, with James Stewart in the leading role, will be aware of the aeroplane at the centre of the story. The twin boom arrangement of the crashed Fairchild Boxcar enabled the marooned passengers to rebuild the wreckage into a viable flying machine, capable of transporting them to safety. This is a nicely contrived story, but of course pure hokum in a practical sense!

By May 1957 the full-size wooden mock-up of the projected AW 650 was taking shape in the Baginton shops. The mock-up featured a fuselage of large cross-section, with large front and rear side-hinged freight doors. A shoulder mounted wing carried the four engines. The twin tail booms merged into the wing trailing edges to form the rear nacelles for the two inner engines, as well as the mounting points and undercarriage bays for the main retractable undercarriage. A retractable nose wheel was positioned in the underside of the forward fuselage. The empennage consisted of twin vertical fins and rudders together with a horizontal stabiliser and elevator married to the outer ends of the tail booms. Access to the elevated flight deck was gained by a ladder from the cargo hold.

Construction of the first Argosy airframe commenced at Baginton in I958 and the new aeroplane featured a pressurised fuselage and cargo hold. The engines selected to power the new freighter were the well proven Rolls-Royce 526 Dart turboprops driving four – bladed Rotol propellers. In each of the tail booms, just aft of their respective undercarriage bays, was a water-methanol tank of about 40 gallons capacity. To increase volumetric efficiency and thus augment power output, especially during take-off, water-methanol together with fuel could be injected into the engines for short periods. This was particularly necessary when aircraft were operating in high ambient temperature conditions from elevated airfields.

Mention of the Argosy booms brings back a still rather unpleasant memory for the author and also perhaps a comment on the down side of human nature. Whilst working on the Baginton sub-assembly section the author was placed with a certain person to build boom frames. Among the boom frames manufactured were those to support the water methanol tanks mentioned above. The mentor was supposed to be a “good fitter” – whose brother was Superintendent of the entire sub-assembly section at Baginton.

One day the author was taking down a fully drilled boom frame to de-burr all the holes prior to re-assembly and final riveting. The author started to de-burr the holes by hand using a slightly larger twist drill – a laborious but absolutely correct procedure. The mentor chided the author for doing it that way, saying it was too slow and prescribed coarse emery cloth to remove the drill arris. Very reluctantly the author did this, knowing it to be wholly wrong for various reasons, (viz) it scratched the pre-etch paint treatment and perhaps more importantly the anodised plating and introduced the distinct possibility of inter-crystalline corrosion. Corrosion was a big issue at the time.

No sooner had the author started to use the emery than a white coated Foreman appeared and proceeded to tear a strip of the author, quite correctly, for using emery cloth, reciting all above quoted reasons for not using it. The author waited for an admission of guilt or complicity from his mentor, but none came and he remained totally silent! Even worse, after the foreman had disappeared the mentor encouraged the author to resume using the emery! After nearly sixty years this still rankles with the writer of this paper, who remembers the names of the Foreman and the so called “good fitter”, the latter with particular contempt! The author never trusted the man again. The author was was certainly not one of AWA’s best apprentices, but did always admit to his own mistakes, which were many!

All the Argosy AW 650 Series 100 civil aircraft and indeed the subsequent AW 660 military machines employed the “safe life” type of wing; similar in design to that of the wartime Avro Lancaster and later Avro Shackleton. This type of wing contained its fuel in “bag” type tanks, which were rubber membranes inserted into appropriate cells formed within the wings. It was really quite an old and well established method of containing aviation fuel and usually the rubber tanks had self-sealing qualities, developed especially for military use during the war years.

Most of the major airframe components for both the civil and military Argosies were constructed at Baginton and these included, Fuselages, Wings, Tail Booms, Tail Fins, Rudders, Stabilisers Elevators, Flaps, Ailerons, Freight Doors, Undercarriage Doors, Passenger Doors, etc. All these major components and many other smaller items were constructed using fully jigged, interchangeable manufacturing methods. For example, it would be absolutely to no avail to manufacture an aircraft wing, at great expense, and find that the corresponding attachment points on the fuselage would not align with it! Jigs and fixtures were a very important part of aircraft work and virtually all assemblies, components and even the very smallest details were manufactured using them. In engineering there is a very specific difference between a jig and a fixture, but the words are fairly interchangeably used, often incorrectly, and it is not essential knowledge for the reader!

A jig or fixture could be as simple as a small hardened steel drill plate containing a few holes, an elementary bend block with a joggle, or at the other end of the scale it might be a steel fabrication as large as the nave of a sizeable church, to assist in the assembly of a big fuselage. In fact, the latter structures for really large aeroplanes were often known as “Cathedral Jigs”. It is believed that Vickers Armstrong at Weybridge employed particularly large Cathedral Jigs for the assembly of their VC10 aircraft.

“Redux bonding” using phenol-formaldehyde/polyvinyl adhesives manufactured by Ciba (ARL) Duxford, was one of the fairly new construction techniques employed on the Argosy for certain components including, the author thinks, cargo floor structural members. The Redux process, probably to specification DTD775, required the use of an Autoclave installation, providing both pressure and heat to cure the special adhesive. However, Redux bonding was seldom used without some supplementary riveting – just in case! Constant monitoring of the Redux process was carried out in a special laboratory at Baginton. One of the Redux tests, the author recalls, was the so called “Peel Test”. This particular test involved specimen pieces being taken from a batch of Reduxed components and subjected to a peeling action in a special machine, rather like peeling an orange. The general idea of the test being that the aluminium itself should tear or shear before the Redux bonded joint yielded. A very severe test of the bonded Redux joint.

Having constructed all the major Argosy components at Baginton it was then necessary to transport them to Bitteswell for Final Assembly. AWA’s Bitteswell airfield was situated just in Leicestershire, at the junction of the A5 and A4303 (A427) roads, approximately two miles West of Lutterworth. Apart from the airfield, AWA had assembly hangars and flight test facilities at Bitteswell. For a fuller description of the Bitteswell complex please see the author’s WIAS paper, “Vulcan’s at Bitteswell”. The road distance between Baginton and Bitteswell is approximately 14 miles and every major unit of every Argosy traversed this route. According to the author’s calculations, which could be incorrect, this amounted to about 77 fuselages and a similar number of wing and tail-boom pairs – port and starboard – being transported. The main difficulty for the fuselage transporters was the centre of Pailton village, as here they had to negotiate a right-angle bend on a fairly narrow section of roadway flanked by cottages. Nevertheless, these journeys were accomplished without mishap, as far as the author is aware.

Registered G-AOZZ, the first Argosy AW 650 – 100 Series machine was assembled at Bitteswell Old Site in the autumn/winter of 1958. After completion of final assembly, the aircraft was taken to the New Site Flight Shed for pre-flight preparations. On 8th January 1959, with snow cleared from the runway, G-AOZZ made its maiden flight from Bitteswell, with AWA’s Chief Test Pilot Eric Franklin at the controls. Eventually the aircraft obtained its full British Civil Airworthiness Certification (CAA) and US Federal Aviation Administration (FAA) approvals and thus the way was open for world sales.

The first Argosy made its public debut at the Paris Airshow in June 1959, followed by appearances of subsequent machines, G-APRN & G-APVH, at Farnborough in the following September. Unfortunately, world sales were very limited and only ten machines of the 100 Series were built. Seven machines initially went to Riddle Airlines of Miami, and three were supplied to BEA. Riddle subsequently transferred their aircraft to Capitol Airlines (five) and Zantop (two) and all these aircraft were used on the extensive Military Air Transport Services (MATS) and Logistical Air Support System (LOGAIR) routes across the USA, delivering important supplies to USAF bases. An AW 650 -101 Series aircraft, G-APRL, is displayed at the Midland Air Museum, Coventry.

The Argosy AW 650 – 200 Series aircraft, the first being G-ASKZ, featured an entirely new form of wing combining “fail safe” design principles together with integral fuel tanks. It was sometimes referred to as the “wet” wing because the fuel was retained within the wing itself without resort to rubber “bag” type tanks. Although not particularly new, this method of wing manufacture only really became practical with integrally machined wing skins and better sealing agents. The “fail safe” concept of the Series 200 wing was born out of progressive thinking which postulated that should a particular structural member fail in flight, there would be sufficient redundant structure remaining to prevent the catastrophic failure of the aircraft as a whole. This “fail safe” principal was becoming the accepted norm across the entire aircraft industry and was replacing the traditionally used “safe life” methods of construction, which had been shown to be not entirely satisfactory after several unexpected and catastrophic failures had occurred.

The author of this paper never worked on the construction of the new “fail safe” wing. It was also alternatively called the “integral” wing. People who actually worked on it may have called it something else! The manufacture of the wing involved fitters climbing inside the structure through relatively small elliptically shaped apertures in the top surface and contorting themselves into the working position, where they were obliged to drill or rivet in a confined space for perhaps several hours at a time. Working in the centre sections of the wing was a comparative luxury, as the aerofoil section was deep, but ingress and egress from the outermost wing panels called for small supple individuals, with dedication and no fear of claustrophobia! The synthetic rubber or polymer sealants used were not particularly user friendly, one of them being called Thiokol, the author seems to recall. Particularly well informed readers may just remember the name Thiokol from another branch of Aerospace!

All in all working on the integral wing was an experience to be avoided, if at all possible! The author worked within the centre sections of the wing on final assembly at Bitteswell, fixing small electrical cleatings, etc, and also remembers, incidentally, drilling some small holes in the wrong place on one occasion, due to imprecise instructions from one of his mentors! However, the author avoided the outermost wing panels as they were far too small and confined for his still youthful, but not very supple frame!

Whilst fitters were operating inside the wing structures in the assembly shop at Baginton, there was always a member of the security/fire/safety/staff present to provide rescue coverage and oxygen, etc, if someone encountered a problem. It was said that the upper surface of the wing would have been “axed” in an absolute emergency to effect a rescue, but the author seriously doubts that would ever have actually happened! The author had and still has a great deal of admiration for all those who worked on the integral wing, in very confined spaces for long periods of time. He always wondered how many inspectors ventured in to check their work! Not too many one suspects! A nod and a wink may have operated here, who knows?

Apart from a change in wing, the AW 650 – 200 Series machines featured enlarged freight doors to accept the slightly bigger 108 inch standard cargo pallets. The first Argosy 200 Series aircraft, G- ASKZ, was retained by AWA for development work. At one stage, the author seems to recall, this machine sported very large wing fences, apparently to improve stall handling characteristics – ludicrously ugly additions indeed! This aircraft, failing to attract a customer, was scrapped in 1967. Five Series 222 aircraft were eventually purchased by BEA, the only customer. Subsequently a sixth machine was purchased by BEA to replace an aircraft that was lost in Italy. Three more incomplete machines remained unsold and were mothballed for several years pending a customer. Eventually these aircraft too were scrapped. So ended the production run of the civil Argosy AW 650 Series 100 and 200 aircraft, a very poor commercial return for AWA from what should have been a very much larger market share.

However, in addition to the civil Argosy aircraft there was the military equivalent, the AW 660 C Mk1, which kept the Baginton shops going a little longer. The Argosy AW 660 C Mk1 resulted from military specification, Operational Requirement OR 323, but official approval to proceed was not granted until after the civil Argosy had flown.

The main changes to the airframe for the military aircraft included, a strengthened fuselage floor, completely re-designed front and rear fuselage sections, modifications to fuel tanks and fuel systems and the provision for in – flight refuelling. Additionally, military rated Rolls – Royce Dart RDa8 Mk 101 turboprop engines were specified. A thimble nose radome at the front of the aircraft housed weather detecting radar.

Perhaps the biggest change was the provision of “clam-shell” or “beaver” doors to the rear fuselage. The lower door portion was designed to also double as a ramp, to facilitate vehicular access to the cargo hold. In order to secure aerodynamic cleanliness, a considerable amount of effort went into determining the optimum shape for the doors. After extensive wind- tunnel testing on models, a full size set of doors was constructed and grafted onto a civil Argosy, G-APRL, to test the in-flight installation. Flight trials dictated that slight lengthening of the doors was required. This was accomplished with the addition of fairings at the appropriate positions. These trials began in July 1960 and were completed by early 1961.

Whereas the civil Argosies had an opening front fuselage door, the AW 660 was provided with a new fixed nose section. The AW 660 C Mk1 retained the Series 100 “safe-life” wing, but with some slight modifications to the fuel system and increased fuel capacity. Provision was also made for the incorporation of in-flight refuelling, but only a few of the AW 660 aircraft had the refuelling probes actually installed. The AW 660 C Mk1 could carry 54 fully equipped paratroops or a maximum payload of 29,000 lbs (13 tons) for a maximum range of 345 miles.

On the 4th March 1961 the first AW 660 C Mk1, registered XN 814, made its maiden flight from Bitteswell, with Chief Test Pilot Eric Franklin at the controls and WH (Bill) Else in the second seat. Ultimately 56 military Argosies were delivered to RAF Transport Command, the first machines going to No 114 Squadron at Benson, in Oxfordshire.

AWA retained XN 814 and did extensive development work with it, including the installation of a Flight Refuelling designed “Buddy Tanker” pack, with the object of turning the machine into an in-flight refuelling tanker aircraft. This particular modification included the installation of large fuel tanks in the cargo hold and the addition of a white torpedo – shaped pod on the port side of the lower fuselage containing the hose and reeling mechanism. This work was carried out predominantly at Bitteswell in the Flight Shed and the T2 Type Hangar, situated on the airfield.

Probably the last AW 660 to pass through the Baginton and Bitteswell shops was a machine that had crashed into the sea when either landing or taking off from Aden. Although not particularly badly damaged, the effects of sea water had taken their toll on the aircraft. Extensive refurbishing was required both to the airframe and the various systems, and this provided welcomed additional work to both Baginton and Bitteswell. The author worked on this machine at various stages as it passed through the shops, finally helping to install the fuel system into the wings at Bitteswell Old Site. The refurbished aircraft finally re-joined the RAF as good as, or perhaps better than new!

The major problem with all the Argosy series, both civil and military, was a substantial lack of range when operating at maximum payloads; a considerable shortcoming particularly for a military aeroplane. This deficiency was never satisfactorily resolved. Also a lack of headroom in the cargo hold, especially on the AW 660 C Mk1, was also a handicap. It has been suggested by some commentators that the Argosy series were also underpowered. Most of these deficiencies had been recognised by the Argosy design team, particularly on the military version. AWA had even offered to the Air Ministry a revised military specification, designated the AW 660 Series 3, before the AW 660 C Mk 1 production programme had actually commenced; thus giving the military an opportunity to procure a much better aeroplane! This proposal received little official interest from the Air Ministry, and hence the RAF was supplied with an aeroplane with known inherent limitations from the outset!

The AW 660 C Mk1 was the last significant order for new aeroplanes that the company was to receive. AWA had hoped to build the new jet propelled STOL/VTOL military transport replacement to Air Ministry Operational Requirement OR 351, and indeed had won the design completion to do so with its projected AW/HS 681 submission. However, this was not to be and the AW/HS 681 project and the Hawker P1154 VTOL supersonic fighter were both cancelled at an early stage of development by a Labour administration, in February 1965. The TSR2 aircraft was cancelled a little later in April of that year. For a more comprehensive description of this cancelled project and its ramifications for AWA, please refer to the author’s “An Aeroplane Too Far: the AW/HS 681”.

The AW Argosy series of transport aeroplanes were solid reliable aviation work-horses, which did sterling service in both civilian and military roles. In the US the AW 650 Series 100 machines, operating on the MATS/LOGAIR operations, earned a particularly good reputation for rugged dependability. Unfortunately, on a wider front the civil aeroplane was not a commercial success and world sales were very disappointing. The Argosy was destined to be the last aeroplane designed and manufactured by a once proud Warwickshire aviation company, Sir WG Armstrong Whitworth Aircraft Limited.

Copyright © J F Willock September 2020

References

  • Armstrong Whitworth Aircraft, The Archive Photographs Series, Compiled by Ray Williams, Chalford Publishing, 1998,
  • An Aeroplane Too Far: The AW/HS 681, JF Willock, WIAS
  • The Rise and Fall of Coventry’s Airframe Industry, JF Willock, WIAS Publication
  • Vulcans at Bitteswell, JF Willock, WIAS

Of the Aircraft & Armament Experimental Establishment, Boscombe Down, seen arriving for IAT 83. This aircraft was written off in a landing accident at the Royal Aircraft Establishment West Freugh in Scotland on 1.10.84. (Mike Freer – Touchdown-aviation) [GFDL 1.2 (http://www.gnu.org/licenses/old-licenses/fdl-1.2.html) or GFDL 1.2 (http://www.gnu.org/licenses/old-licenses/fdl-1.2.html)]

Forward view of the civilian Argosy, note the open forward cargo door (Ozzy Delaney / CC BY) (https://creativecommons.org/licenses/by/2.0)