join cahsjournalInterested in joining the Canadian Aviation Historical Society? We have a diverse membership from across Canada and the world.

Membership Benefits:

Four issues of the CAHS Journal each year, site-wide access, including full-text PDFs of all available Journals, monthly e-newsletters, member's page on the website... and more. To learn more about becoming a CAHS Member, click here.

  • heritage toronto slide

  • Plaque Celebrating Aviation History in Mount Dennis

    Saturday, July 15 - 10:45 am

    Hearst Circle and "The Wishbone" (Opposite Harding Park in Mount Dennis)

    Reception to follow at The Atrium, 12 Division Police Station, 200 Trethewey Drive, North York

    This event is a joint function of Heritage Toronto, CAHS (Toronto Chapter & National) and 400 Squadron Historical Society.  The plaque is honouring the airfield that hosted 1st flight over Toronto in 1910, the startup location of DeHavilland Aircraft in Canada in 1928 at this airfield and in 1932 the first operational base of the RCAF 400 "City of Toronto" Squadron as 10 Sqn and later 110 Sqn.

    RSVP at

    Click here for larger image.

    FINAL Invite Trethewey july15 545

    Background on the William G. Trethewey Property

    By Dr. Robert Galway

    This property was purchased by William Trethewey following his sale of two Silver mining properties that he discovered in Cobalt, Ontario on 1904. He and his brother Joseph O. Trethewey made millions in this transaction. William Trethewey came to Toronto and purchased 600 acres in Weston, near present day Jane St. & Lawrence Ave. in 1907 The Royal Automobile Club of Canada and the OML of which Trethewey was a member, asked for permission to use a portion of the property for an exhibition Air Meet. This took place July 9-16th, 1910 following closely on the heels of the initial Air Meet held in Pointe Claire, PQ.

    During the Toronto meet, French Aviator Jacques de Lesseps completed the first flight over the city of Toronto as he had done two weeks previously in Montreal. The Toronto flight occurred on July 13, 1910. This is the basis for recognizing Jacques de Lesseps on the Heritage Toronto Plaque that will be unveiled this summer on July 15, 2017.

    However, this is not the sole reason for recognizing the contribution that this plot of farmland made to Canadian aviation history.

    Following the Air Meet of 1910, the property became the center of early aviation activity in Toronto. Indeed, it became known as de Lesseps Field. In 1928 de Havilland UK decided establish a manufacturing center in Canada. They were persuaded to do so because of the success they had met in selling the DH60 Moth to the Ontario Provincial Air Service. In their search for a suitable property, they were put in touch with Frank Trethewey who had inherited the property on his father’s demise in 1926. Trethewey leased a parcel of the land to de Havilland and with the incorporation of de Havilland
    Canada was appointed to the DHC Board.

    Consequently, the Trethewey property became the first manufacturing site of de Havilland. In fact the first building used to assemble the DH60 series was the Trethewey Canning Shed made famous by the sketch completed by famous aviation artist, Robert Bradford.

    Frank Trethewey was given the opportunity to purchase DH aircraft at a significant “favored” price. He and his brother were RNAS veteran pilots. In the 1930's he was Chairman of de Havilland Canada.

    The establishment of de Havilland Aircraft on this property in 1928 is the second reason to grant historic recognition to this property.

    Frank Trethewey not only over time purchased three aircraft from DHC but went one step further and joined the RCAF. This led to the establishment of the RCAF Squadron 10/ 110 on Trethewey Field. Frank Trethewey was one of the first four flying officers appointed to the Squadron. In 1940 he was appointed commanding officer of Base Trenton.

    The squadron was formed in October 1932 as 10 (Army Cooperation) Squadron and began flying in 1934 at the Trethewey Farm airfield (aka de Lesseps Field) in Toronto. In April, 1935, the City of Toronto adopted the squadron which then became officially known as “10 (City of Toronto) Squadron”. In 1937, the squadron was re-designated “110 (City of
    Toronto) Squadron”.

    The squadron flew five basic types of aircraft, all biplanes, from Trethewey until late 1939 when it deployed to Rockcliffe. During the Trethewey era, the squadron was involved in recruitment and flight training. At Rockcliffe, the squadron underwent conversion to the Canadian-built Westland Lysander until mid-February 1940. The squadron then deployed to the UK as the first RCAF squadron to enter the Second World War.

    In the UK, the squadron was initially equipped with the Lysander III and was involved in the Army Co-op and photo reconnaissance role. The squadron was active in the Dunkirk evacuation (27 May - 3 June 1940) but not directly involved in the Battle of Britain (10 July - 31 Oct. 1940). In mid-1941, the squadron was re-designated “400 Squadron”.

    Today, the Squadron is located at Camp Borden and is the main maintenance centre for maintenance of the RCAF's Tactical Helicopter Squadrons.

  • Canada150books slide

  • 2017 convention slide savethedate 600px

  • My Snowbirds Flight - Aide-Memoire

Written by Mathias Joost.

Bombing the South Saskatchewan River in 1951

RCAF P-51s 300By Mathias Joost

Alfred, Lord Tennyson declared in his poem Locksley Hall: In the Spring a young man's fancy lightly turns to thoughts of love. However, if you're the mayor of a Canadian city located on a major river, flooding is probably a greater concern for you. In 1951, an ice jam on the South Saskatchewan River threatened to flood the city of Medicine Hat. So what do you do? You call in the RCAF to bomb the ice jam.

Bombing ice jams was nothing new. In 1929, the Canadian government decided to bomb the ice in the St. Lawrence to speed the opening of the river. Canadian Airways pilot D.S. Bondurant, flying a Fairchild 71, dropped explosive charges onto the ice which produced a lot of ice chips and dead fish but no expedited break-up of the ice. In May 1945, two Liberators from Gander bombed the Hamilton River near Goose Bay to reduce the ice jam that was backing up water and threatening some of Goose Bay's infrastructure. On 29 March 1951, the South Saskatchewan River broke through its banks and flooded fields when two ice jams downstream began to raise water levels. The rising river was threatening the city of Medicine Hat and its buildings. The efforts to dislodge the ice jams became Operation Floodhat, as the RCAF named it.

The first calls to the RCAF were made at 1:20 PM on 29 March. Mr. Shoulton, the city's Public Works manager, requested assistance in that the RCAF bomb the ice jam. After that, things moved very quickly. Mr. C.E. Gerhart, Alberta's minister of municipal affairs called at 1:45, while Northwest Air Command (NWAC) staff called RCAF Unit Ralston (Suffield) to authorize an aerial recce. At 2:10 RCAF station Calgary reported that they did not have bombs or rockets. However, Group Captain Z.L. Leigh at AFHQ approved asking the Canadian Joint Air Training Centre (CJATC) at Rivers, Manitoba for support. He also stated that a written waiver for any damages be obtained from the provincial government.

rcaf mustang in flight

By 5:00 PM, Squadron Leader Laurence Virr at Ralston (RCAF Station at Suffield) had taken Mr. Shoulton on an aerial recce, the NWAC legal officer had prepared and had Mr. Gerhart sign the waiver and the CJATC at Rivers said they would send two Mustangs each armed with two 500 lb bombs and a Dakota loaded with eight additional 500 lb bombs. At 6:45 Flight Lieutenant D.F. Archer and Flying Officer A. Mehlhaff in Mustangs 9573 and 9580 dropped their four bombs with accuracy; however, this did not dislodge either ice jam. Both were bombed, with S/L Virr performing the role of master bomber and acting as safety aircraft. However, further bombing efforts could not be made that day as daylight was fast disappearing.

The next morning, the 30th, the two Mustangs were again loaded with two 500 lb bombs each and Mitchell 641, from Suffield, with four. Archer and Mehlhaff and Flying Officer Morrison in the Mitchell waited for S/L Virr in the Norseman to carry out a recce and advise that all was clear for their work. At 8:45 all three aircraft started their work, again bombing with accuracy and again with negative results. In the afternoon, Flying Officer D.L. Osborne in Mustang 9577 arrived from Rivers and bombed the ice but this did no good.

The assessment was that the delay on the fuzes was too long with the result that the blast was being directed in the mud of the river bottom and not on the ice. Besides the problem of the fuze setting, the ice was 6 feet thick and lodged into the mud at the bottom of the river. The bombing opened up small holes in the ice jams but these were quickly filled by more ice.

On the 31st, the first to have a go was the Mitchell with the 1000 lb bomb brought in from Rivers the previous evening. Before the drop could occur, a nearby farm house was evacuated while the Norseman acting as safety aircraft had to drop two messages to spectators who were getting too close. The arrival of spectators was not unexpected. The use of the 1000 lb bomb had been advertised in Lethbridge's newspaper and the prospect of front-row seats for a bombing display was a rare treat.

At 9:28 AM, the Mitchell dropped its lone bomb. With the fuze on a shorter setting, the blast effect was greater and the ice cracked considerably but still did not cause the ice jam to break. The three Mustangs then came in to do their job, dropping another 3,000 lbs of bombs. The main ice jam was now being held together by one piece of ice but would still not move.

mitchell 600

For the RCAF, they considered the bombing effort complete at this time. However, the spectre of failure had always been there and so Dakota 261 from 435 Squadron flew explosives from Edmonton to Medicine Hat on the 30th and then picked up more in Kamloops the next day. These were for the use of the Royal Canadian Engineers (RCE), who were the back-up plan. As the diarist for 435 Squadron put it, the fact the engineers had to finish the job was an embarrassment for the RCAF. And the ice jams, they began to shift on the 31st and the work of the engineers helped to further dislodge them.

Unfortunately, these bombing runs produced two pieces of unexploded ordnance. These were the targets of several searches over the next several years with the first efforts being made two days after the last bomb run. This first effort was supported through a RCAF Sikorsky helicopter. Unfortunately the two bombs were not found despite efforts over the next three years. Whether they ever were found is not recorded.

The bombing weakened the ice jams and provided some valuable lessons in bombing ice. Nature provided the ultimate push to break up the jams, with assistance from RCE and their demonstrations. The river's muddy flow and springtime flooding moved and covered up the unexploded bombs, which may still be somewhere in the river. And thus endeth the tale of the RCAF bombing of the South Saskatchewan River.

[My thanks are extended to CAHS member Jerry Vernon for his assistance on points related to the Mustangs and the Mitchell, Mathias]