On the 29th November 1950 Factory Instruction number 390 was issued by de Havilland Canada (DHC) to authorize construction of the prototype DHC-3, initially known as the King Beaver and later as the Otter.

Over the next year the aircraft was hand built at Downsview, and was rolled out on the 10th December 1951 in an overall yellow colour scheme with blue cheat line. Registration CF-DYK had been requested for the aircraft. These marks had already been allocated to Canadair Ltd., of Montréal in June 1946 for Douglas C-47 serial 13435 which they were refurbishing, but this aircraft had been sold to Aerolineas Argentinas in November 1950 as LV-ABX and accordingly the marks were available for re-use by DHC. The Otter was actually registered CF-DYK-X, being in the experimental category at that stage, and it made its first flight as such from Downsview on 12^th December 1951 flown by DHC's Chief Test Pilot George A. Neal.

CF-DYK-X continued its test flights from Downsview that month and for most of 1952. Flight trials showed that the Otter had some stability problems, which led to a re-design of the fin. In August 1952 a new fin was fitted, and painted on 2nd September 1952. This change cured the stability problem and resulted in the certification of the Otter on wheels and skis in November 1952. The aircraft was also used for the trial installation of the Hydromatic Propeller and the Janitrol heater. On the 1^st November 1952 the Otter was transferred to the ownership of the Royal Canadian Air Force (RCAF) and was allocated military serial 3667. The aircraft retained its overall yellow colour scheme with blue cheat line, and the serial was painted on the blue tail band as 3667-X.

The Otter remained based at Downsview on “indefinite loan” by the RCAF to DHC. It continued in use for test work, operated and maintained by DHC's research & Development Department. Amongst other projects it was used to evaluate a flap system which utilised air probes through the flaps and during 1957/58 carried a scale model of the DHC-4 Caribou mounted on a framework above the fuselage, for aerodynamic tests. It also tested the external carrying of a canoe by the Otter.

In February 1963, after more than ten years of RCAF ownership, although operated during this entire period by DHC, a report noted that “considering that this airframe has had its configuration changed to an extent that it is no longer in a flyable condition, and so would have little recovery value if sold”, the Crown Assets Disposal Corporation granted its authority for the transfer of 3667 to the Department of Defence Production, where it was to be used for experimental purposes and for the Defence Industries Research Programme. The Otter was restored to airworthy status by DHC and in June 1965 was registered to the Department of Defence Production as CF-SKX, the marks being carried on the aircraft as CF-SKX-X in view of the on-going experimental nature of its flights, which were conducted by DHC. During December 1966 the aircraft was used for “wing profile drag investigation” flights from Downsview.

A letter dated 21st June 1968 from DHC to the Department of Transport stated that CF-SKX had been on loan to DHC for research and development projects for the Defence Industries Research Programme, but during the past twelve months the aircraft had been in storage at Downsview and had not participated in any research work. Its total airframe time at that stage was 747 hours and with no work scheduled for the Otter, ownership was transferred to DHC, who decided to sell the aircraft. Rather than overhaul the Otter and sell it as a flyable aircraft with a current Certificate of Airworthiness, DHC elected to advertise the Otter for sale “as is, where is”, a decision which was to have many repercussions.

The buyer of the aircraft was that well-known Otter operator Lambair of The Pas, Manitoba, who acquired ownership of CF-SKX on 24th February 1969, the title in fact being transferred to Lamb Enterprises Ltd. On the following day, DHC wrote to the Department of Transport informing them of the sale and advising that the new owners wished to fly the aircraft to Calgary to rework the Otter to standard configuration. On 27th February 1969 a ferry permit was issued for the flight from Downsview to Calgary. At Calgary, Field Aviation removed all the test equipment from the aircraft and carried out a major overhaul and refurbish, returning the Otter to standard DHC-3 configuration. After completion of this work, CF-SKX was test flown at Calgary on 30th May 1969 and certified as 31 airworthy by Field Aviation.

Lamb Enterprises Ltd applied for registration CF-AUS for the Otter, marks which were provisionally allocated by the Edmonton office of the Department of Transport. CF-AUS had been the marks carried by Thomas Lamb's first Stinson SR-7A aircraft back in 1936. Not intending to operate the aircraft itself, the Otter was sold by Lamb Enterprises to Carter Air Services of Hay River, Northwest Territories and on 21 May '69 marks CF-AUS were provisionally allocated to Carter Air Services for the aircraft. At this stage, however, difficulties arose. When the paperwork arrived at the Department of Transport's head office in Ottawa, they realised that this had been an experimental aircraft, indeed the prototype Otter, and on 5th June 1969 the marks CF-AUS were refused and a direction issued that registration CF-SKX was to be used for the aircraft. The next day, the Department issued a requirement that DHC Engineering must participate in determining the work package necessary to return the aircraft to standard configuration, due to the experimental history of the aircraft. (Lambair subsequently used the marks CF-AUS for a DHC-6 Twin Otter aircraft, registered to the company in February 1971.)

Field Aviation in Calgary approached DHC at Downsview, who replied on 10th June 1969 that they were unable to supply enough legitimate records of the history of the aircraft, the modifications made to it, repairs etc to satisfy Field's request for information. They explained that the aircraft had originally been operated as a civil aircraft, as CF-DYK-X, and then turned over to the RCAF with all its documentation. When the aircraft was taken back from the RCAF this documentation was not returned, and DHC believed the documentation no longer existed. They continued:”The only data we have consists of a large mass of work records scattered throughout our archives. To wade through this mass of data and correlate it with the modifications would be a time consuming exercise with no guarantee of success”. DHC explained that this problem had been looked into when they considered selling the aircraft, which is why they sold it “as is”.

By 12th June 1969, what with the ferry flight from Downsview to Calgary and test flights, total time on the Otter had risen to 761 hours. Field Aviation wrote to the Department of Transport with details of the work they intended to carry out to satisfy the Department as to the airworthiness of the aircraft. Then on 19th June an exasperated Mr Tom Lamb wrote to the Department saying that he had refunded Carter Air Services their money. He continued: “After spending over $100,000 buying this aeroplane, ferrying, completely overhauling, all modifications to date, sales tax, paid for new Otter floats and gear, which is not far from $20,000, new wheel-skis, brand new ADF-VHF, new upholstery, new seats, instrument panel, now your Department will not give this aeroplane a Certificate of Airworthiness. I would be much obliged if you will tell me and Field Aviation what we have to do now in order to licence this aeroplane. After all, CF-SKX is the grand-daddy of some 500 Otters that helped win the war and open up our Northland”!

After considerable correspondence, a massive work and inspection package was agreed between the Department, DHC and Field Aviation and carried out by Field at Calgary, the work taking two months to complete. Finally, on 5th September 1969, a Certificate of Airworthiness was issued in respect of Otter CF-SKX. Lamb Enterprises then advertised the aircraft for sale again and on 15^th December '69 it was sold to Geo-Terrex Ltd, an Ottawa-based survey company, and the Otter was flown to Ottawa. It was registered to Geo-Terrex Ltd on 7th January 1970 as CF-SKX, and they arranged for Laurentian Air Services of Ottawa to operate the Otter on their behalf.

Before the aircraft entered service, it was modified with survey equipment for its new role at Ottawa. On 13th March 1970 Personal Plane Services Ltd, Ottawa a division of Litton Industries, made application to the Department of Transport for an experimental flight permit to test the installation of wing-tip extensions with electro-magnetic pods. The permit was granted on the basis of day-VFR flight only, with flight over built-up areas prohibited. A test flight was conducted from Ottawa on 19 March 1970, the pilot subsequently reporting: ”In my experience, CF-SKX-X is an above average Otter in smoothness, performance and stability throughout the range. The complete test sequence was performed in ideal conditions of air smoothness”. The wing-tip pods were later re-positioned several inches, necessitating a re-flying of portion of the test programme. The Department indicated informally that a high speed run of 175 mph was required.

On 1st May 1970, over Dunrobin, Ontario during a high-speed dive, both wings failed from severe negative loading, torsional flutter and high aerodynamic stresses and broke off the aircraft. The Otter crashed to the ground, killing the pilot, the sole occupant. The subsequent enquiry found that this type of break-up was consistent with the performance of high-speed flight in turbulence, the aerodynamic loading under these conditions being aggravated by the wing pod installations. The test flight had been undertaken under “unsuitable atmospheric conditions”. It was a tragic end to a most historic aircraft, particularly given the great efforts which had been made to restore the prototype Otter to commercial service.

Full history up to 2005 courtesy of Karl E Hayes © from DHC-3 Otter - A History (CD-ROM 2005).