Gadila-class Merchant Aircraft Carrier

Design history [1]
Merchant Aircraft Carriers (or: MAC-ships) were merchant ships with only the minimum conversion necessary to operate aircraft from a flight deck. They were first officially considered by the Admiralty in the beginning of 1942, but the decision to convert a number of ships was not made until the summer of 1942. By then, the monthly Allied merchant ship losses were on the rise and the Battle of the Atlantic was drawing closer to a decision. A major strategic problem for the Allies was that shore-based aircraft could not provide cover for the transatlantic convoys during the entirety of the voyage. There was a gap in the middle of the Atlantic, where convoys had no cover by aircraft and where as a result, the German U-boats could wreck havoc on the convoys without interruption. The MAC-ships was intended as temporary measure to close that gap, only in place until more suitable and effective escort carriers could be brought into service.

The British Admiralty requirements were initially for ships with a minimum speed of 14 to 15 knots, dimensions capable of providing a flight deck of 490 x 62 feet and hangar space for six fighter aicraft. Shortage of suitable candidates and experienced dockyards made that these requirements had to be recast to 11 knots, a flight deck of 390 x 62 feet and a hangar for four Fairey Swordfish anti-submarine and reconnaissance aircraft.

Orders were issued in October, 1942 for the conversion of 9 ships of the British Rapana-class tankers, of which the Dutch-flagged Macoma and Gadila were part. The number of similar ships being converted allowed for some standardization. The superstructure was replaced by a flight deck, made up of pre-fabricated parts. Arrester gear was fitted, as was a safety barrier and a small bridge island on the starboard side. There were no hangar arrangements below decks, and the aircraft had to be maintained maintained, refueled and parked on the flight deck, in addition to all normal flying operations there. The Swordfish-aircraft were normally parked at the after end of the flight deck, closed off by an arrangement of wind screens. Below decks, very little was altered, only generator capacity was increased to cover the extra electrical load from radar and communication equipment. These additions cost the ships about 1230 tons of their cargo capacity (reduction from 12.240 deadweight tons to 11.010 deadweight tons).

The MAC-ships were not commissioned in the British Royal Navy or Royal Netherlands Navy, as they continued to fly the merchant flag and were crewed by merchant officers and men. They did have a detachment of naval personnel on board which flew and maintained the aircraft.
[1]: Design history from [LEN] unless noted otherwise. [LEN] gives an excellent overview of the design history of these ships.

Macoma at sea, date and place unknown.

Construction details [1]
Name Gadila Macoma
Dockyard Howaldtswerke A.G., Kiel (Germany) N.V. Nederlandsche Scheepsbouw Maatschappij, Amsterdam
Dockyard number [2] 732 235
Owner N.V. Petroleum Maatschappij "La Corona", Den Haag. La Corona was a subsidiary of the Anglo-Saxon Patroleum Company Ltd.
Laid down    
Launched December 1, 1934 December 31, 1935
Commissioned April 11, 1935 (tanker)
February 1, 1944 (MAC)
May 13 , 1936 (tanker)
April 1, 1944 (MAC)
Radio callsign [2] PEFM PFRR
Pennant [3] MR MX
[1]: From VML unless otherwise noted. Confirmed by sources at the end of this page unless noted otherwise.
[2]: From [CNO].
[3]: From [HAZ]. These were in fact not pennants, since they were not naval ships, but flight deck numbers.

Displacement 16.660 tons (full load displacement) [1)
8011 gross registered tons
Crew 54 normal crew plus 64 navy detachment.
Dimensions 147,22 (o.a.) 140,21 (p.p.) x 17,98 x 10,36 m.
Armament 1 x 102 mm
2 x 40 mm Bofors
6 x 20 mm Oerlikon [2]
Aircraft 3 - 4 Fairey Swordfish Mk II, later Mk III of 860 Squadron Fleet Air Arm. [3]
Radar and electronics [4] Type 271 surface warning
Type 79 or 279 long range air warning
High Frequence Direction Finder (HF/DF)*
[1]: Displacement as merchant ships. May have been different as merchant aircraft carriers.
[2]: [LCOL] says 8 x 20 mm and no 40 mm.
[3]: 860 Squadron was manned by Dutch naval personnel. The Royal Netherlands Navy gained valuable experience with operating aircraft from flight decks on the MAC-ships.
[4]: Standard equipment for MAC-ships. Configuration for Macoma and Gadila may have differed.

Propulsion details [1]
Machinery 1 x 4-stroke 8-cylinder MAN diesel engine (Gadila)
1 x 4 stroke 8-cylinder Sulzer diesel engine (Macoma) [2]
Performance 4000 - 4400 bhp
Shafts 1
Maximum speed 12 knots (fully loaded)
[1]: From VML unless otherwise noted. Confirmed by sources at the end of this page unless noted otherwise.
[2]: DI22 says Macoma had a Werkspoor diesel engine of 4000 bhp. [CNO] confirms this, saying it was a 6-cylinder engine. [VML] says Macoma had a Sulzer diesel engine. This may have been a Sulzer license-built by Werkspoor.

History [1]
Gadila Reconstructed to Merchant Aircraft Carrier by Smith's Dock Company Limited, Middlesbrough between April 1943 - February 1944.[2]. Commissioned February 1, 1944. [3]. Made a number of transatlantic voyages: [4]

Convoy Period
ON-229 March, 1944
SC-157 April 17 - May 1, 1944
ON-236 May, 1944
HX-293 May 27 - June 9, 1944
ON-241 June, 1944
HX-299 July 11 - July 24, 1944
ON-249 August, 1944
HX-306 August 31 - September 17, 1944
ON-263 October, 1944
SC-161 November 17 - December 4, 1944
ON-273 December, 1944
HX-333 January 18 - February 1, 1945
ON-284 February, 1945
SC-169 March 7 - March 21, 1945
ON-295 April, 1945
HX-353 April 29 - May 15, 1945
ON 284 February 10 - March 20, 1945
SC 169 February 10 - March 20, 1945

Taken out of service May 30, 1945 and converted back to tanker at Maatschappij Feijenoord, Schiedam (Netherlands).
Scrapped in Hong Kong starting June, 1958.
Macoma Trials May 13, 1936. Reconstructed to Merchant Aircraft Carrier by Palmers Shipbuilding & Iron Company, Hebburon on Tyne. Commissioned as Merchant Aircraft Carrier on April 1, 1944. Made a number of transatlantic voyages: [4]

Convoy Period
ON-242 June, 1944
HX 300 July 17 - August 3, 1944
ON-248 August, 1944
HX-305/TD> August 25 - September 10, 1944
ON-254 September, 1944
HX-312/TD> October 5 - October 21, 1944
ONS-35 October 29 - November 15, 1944
SC-161 November 17 - December 4, 1944
ONS-38 December 13, 1944 - January 2, 1945
HX 331 January 8 - January 22, 1945
ON 282 February, 1945
SC-168 February 25 - March 13, 1945
ONS-47 April 11 - 30, 1945
SC-175 May 7 - May 21, 1945

During one escorted convoy journey across the Atlantic the aircraft from Macoma found a submarine surfaced in the vicinity of the convoy. It was finally attacked by aircraft from 860 squadron and Fleet Air Arm aircraft from another MAC-ship. The submarine sank, but it later turned out to be the submarine La Perle of the Free French Navy. There was only one survivor.

Taken out of service May 30. 1945. Converted back to tanker at Rotterdamsche Droogdok Maatschappij in Rotterdam.
Scrapped Hong Kong 1958.
[1]: From [VML] unless otherwise noted. Confirmed by sources at the end of this page unless noted otherwise.
[2]: [VML] says Gadila was converted at Middlesbrough. [LEN] says converted at North Shields, by same dockyard.
[3]: According to [LEN], Prince Bernhard inspected the Gadila during trials, and insisted on making a deck landing himself. I don't know if this is true.
[4]: From [CYW].

Gadila at anchor in port, date and place unknown. (Collection NAVPIC-Holland)
Gadila at anchor in port, date and place unknown. (Collection NAVPIC-Holland)
Fairey Swordfish landing aboard Gadila (Collection NAVPIC-Holland)

CNO Cnooks - De nieuwbouw van de Shell tankervloot in de jaren 1924-1940 (deel 2).
CYW - Arnold Hague Convoy database
DI22 "M.S. Macoma", De Ingenieur magazine of May 29, 1936.
HAZ Hazegray and underway - Dutch MAC ships
LEN J. Lenaghan "Merchant Aircraft Carrier Ships", published in Transactions of the Royal Institution of Naval Architects, volume 89, number 2 (April 1947). Reproduced in the book "Selected papers on British warship design in World War II, Conway Maritime Press, 1983.
LCOL H.T. Lenton/J.J. Colledge "Warships of World War II", published 1962.
VML A.J. Vermeulen "De schepen van de Koninklijke Marine en die der gouvernementsmarine 1862-1962", published 1962.

August 4, 2014 Added convoys (Macoma)
July 30, 2014 Added convoys (Gadila)
July 29, 2014 Updated page (all sections)

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