Douglas RD, RD-1, RD-2, RD-4 "Dolphin"

June 3, 2022

Douglas RD, RD-1, RD-2, RD-4 "Dolphin"

A Coast Guard RD4 Dolphin


The Coast Guard acquired 13 total of four different variants of the famous Douglas Dolphin.  They began acquiring Dolphins soon after the prototype model, named Sinbad, was introduced in 1930.  It had an all-metal hull with room for 8 passengers and two flight crewmen.  It featured a plywood-covered cantilever wing similar to the Fokker model acquired by the Coast Guard during this time.  The first example was powered by two tractor-fitted J-5C Wright engines with two Hamilton Standard fixed pitch propellers.  It was purchased for $31,500 in 1931 and was designated as RD for multi-engine transport, Douglas.  It was delivered on 19 March 1931.  It was not an amphibian but utilized beaching gear.  The Coast Guard christened it Procyon and assigned it to Air Station Cape May, New Jersey.  LCDR C. C. von Paulsen flew Procyon to its new duty station.  The Coast Guard soon after acquired two other Douglas RDs and were somewhat different than Procyon in that they were true amphibians and were powered by more powerful Wright engines.  They were christened Adhara (designated as RD-2 and delivered in July, 1932) and Sirius (delivered 5 August 1932).  Procyon was later converted to an amphibian configuration.  The service acquired upgraded Dolphins in November, 1935, and these were officially designated as RD-4s. 

According to Pearcy:

"The Douglas RD started as the Sinbad, going through some iterations before the final configuration was established.  It appeared to be smaller and lighter than the later Dolphins.  The U.S. Coast Guard aircraft register for 1933 shows the RD named Procyon CG-27 based at Cape May, New Jersey, and allocated the international radio call-sign 'NUMRG' and Coast Guard call-sign "24 G."  Apparently this first production aircraft was delivered to the USCG in New York direct from the Douglas factory in February 1931.  This was a flying-boat, not an amphibian.  The RD-2 Adhara was delivered in July 1932, and in 1933 it was based at Gloucester, Massachusetts, with the international radio call-sign 'NUMRJ' and Coast Guard call-sign '24-J.'  The RD-1 Sirius followed on 5 August 1932, being based at Miami, Florida in 1933 with international call-sign 'NUMRH' and Coast Guard call-sign '24 H.'  The first RD-4 was not delivered until nearly three years later, on 20 February 1935.  All four types were externally different in fuselage, engine and tail configuration. . .The U.S. Coast Guard aircraft were used extensively in search and rescue (SAR) missions and as flying lifeboats, often flying far out to sea from several air stations to rescue stricken mariners or seamen in need of urgent medical care to hospitals ashore.  Upon U.S. entry into World War II in December 1941 the U.S. Coast Guard became part of the U.S. Navy and the surviving Douglas RDD-4's were assigned to security patrols along the United States seaboard." [pp. 169-172]



Official No.





27; 227/ V106

9 Mar 1931

Dismantled, 1937



28/ 128/ V109

5 Aug 1932




29; 129; V111

July 1932

Mar 1937, crashed



130; V125

Nov 1934

Jan 1943



131; V126

Feb 1935

Aug 1941, crashed



132; V127

Feb 1935




133; V128

Feb 1935




134; V129

Mar 1935




135; V130

Feb 1935

Aug 1935, crashed



136; V131

Mar 1935

Jul 1940



137; V132

Apr 1935

Jun 1943



128; V133

Apr 1935




129; V134

Apr 1935

Aug 1942



Douglas RD-4; "One of the huge flying life boats of the U.S. Coast Guard Air Station at Biloxi, Miss., taxiing in the waters of the Bay of Biloxi, just before a flight over the Gulf of Mexico on patrol and rescue duties."  Photo Number 35, no date.  Photographer: Anthony V. Ragusin, Biloxi, Mississippi.

Douglas RD; Flying low over water, rear view; no caption/date/number; photographer unknown.

Douglas RD; "Douglas amphibian on patrol," (flying over water, overhead mid-fuselage view); no date; Bray Pictures Corporation Photo, Number 13A.

Douglas RD; Water take-off; no caption/number/date; photographer unknown.

Douglas RD-2 Adhara; No caption, profile view, port-side, on runway; 14 June 1932; Photo number 7-13-33N 3726 DOLPHIN; photographer unknown.

Douglas RD-2 Adhara radio arrangement; "Radio installation Coast Guard Patrol and Rescue Plane ADHARA.  Main transmitter model T-19, 100 watts, emission A.C.C.W. telegraph, frequency range 285-600 Kc; high frequency trans-receiver, model T-20-1, CGR-45; transmitter 5-watts power, emission C.W. and voice, frequency range 2464-4050 Kc, receiver frequency model CGR-19-C radio direction finder, homing receiver, beacon receiver and communication receiver, frequency range 250-525 Kc., (installed in tail and arranged for remote control from operators position since above photograph taken).  Frequency indicator, model CGR-57, crystal checked, frequency range 250-600, and 2800 to 8100 Kc (not shown)."  14 July 1932; Photo Number 5-3-34 3802 DOLPHIN; photographer unknown.

Douglas RD-4 Mizar; No caption/number/date; photographer unknown. Courtesy of Van R. Field.

Douglas RD-4 Mizar; No caption/number/date; photographer unknown. Courtesy of Van R. Field.

Douglas RD-4 in the New York City area; No caption/number/date; photographer unknown. Courtesy of Van R. Field.

Arthur Pearcy, U.S. Coast Guard Aircraft Since 1916 (Annapolis: Naval Institute Press, 1991), pp. 320-321.

Gordon Swanborough & Peter M. Bowers.  United States Navy Aircraft Since 1911 (Annapolis: Naval Institute Press, 1990) (revised), pp. 432-435.