The Stinson L-5 Sentinel Larry Westin - 2/17/96 REV 10 - Updated - 1/1/04 Stinson predecessors to the L-5 Stinson's first entry into the liaison field was the purpose designed model 74. First designated by the USAAF as the O-49, it later became the L-1, 324 of which were eventually built. While the L-1 had excellent short field performance, it was expensive to operate. Just before America's entry into WWII, Stinson was building the model 10/10A Voyager, a 1938 design intended for the mass market. A March 1940 USAAF competition asked the U.S. aircraft industry for a less costly liaison aircraft. Six commercial Voyagers were purchased by the United States Army Air Force (USAAF) in 1941 for testing, and designated as YO-54's. USAAF serial numbers 41-143 to 41-148. Success with the YO-54's lead Stinson to work on a purpose built replacement. This aircraft was the Stinson model 75B, only one of which was built. It was registered as NX27711, serial number 6001. Chief engineer was A. P. Fontaine and it was first flown by Albert H Schramm on June 19, 1940. Originally powered by a Lycoming O-235 engine of 100 HP, the engine was later changed to a Franklin 6AC-264-F2. Emerge the Stinson L-5 A. P. Fontaine further engineered the model 75B into the Stinson model 76. First flight, Al Schramm test pilot, was on June 28, 1941. The aircraft was registered NX27772, and carried serial number 76-1. First testing saw the model 76 equipped with a Lycoming 175 HP engine and full span leading edge slots. During testing it was learned that the full span leading edge slots caused asymmetric lift and could lead to an uncontrollable flat spin. Changes were made to limit the slots to half span and larger tail surfaces to NX27772. The result was an excellent flying aircraft. Initially identified as by the USAAF as the O-62. I believe that no aircraft were actually delivered to the USAAF with the O-62 designation, but rather the USAAF renamed the Stinson model 76 as the L-5 before any were delivered. During World War II most USAAF aircraft were assigned "popular" names. The reason for popular names was to identify aircraft by name rather than specific model. The public might be told of "Flying Fortresses" going to some war theater for example, rather than "B-17G's" going to that specific location. This allowed the public to be given information without giving the enemy specific model information about the aircraft being deployed. The official USAAF popular name for the Stinson L-5 is the "Sentinel." Unofficially it is often called the "Flying Jeep." Stinson continued as a division of Vultee through 1942. A new company, Consolidated Vultee, resulted from the merger of Consolidated and Vultee in 1943. Stinson remained in Wayne, Michigan as the Stinson Division of Consolidated Vultee. Because of the parent company name, you may find the L-5 referred to as a Vultee product rather than a Stinson product. The first USAAF order to Stinson was for 275 aircraft, originally identified as the O-62. Before the first delivery to the USAAF the designation was changed to L-5. Voyager 10 features were a major influence on the design, but the L-5 was optimized as a two place liaison and observation aircraft. About 3,691 Sentinels were built during WWII for the US Army Air Force and the Royal Air Force. US Marines received 306 Sentinels, all originally built under USAAF contract, and the US Navy also received some Sentinels with Bureau Aer numbers assigned to the Marines. Marine procurement did not begin until 1943 when Consolidated and Vultee had merged, with Marine aircraft designated, following Navy lines, as the OY-1. The models of the Stinson L-5 Sentinel O-62 First production airplane, 275 airplanes, deliveries through mid 1942. Gross weight 2050 pounds. Airplanes equipped with an RCA AVT-15 or AVT-112 radio transmitter, and an AVR-20A radio receiver. Many publications indicate that these airplanes carried the O-62 designation, but most likely all were delivered as L-5. Updated information on the O-62 designation. Homepage visitor Ron Hefner, e-mail , wrote to tell me he owns Stinson serial number 1003, Army Air Force serial number 42-14800. The data plate on his airplane shows it to be a L-5. Two areas of interest here, this is probably the oldest L-5 in existence, and it also shows that while many publications show serial numbers for the O-62, they were almost certainly renamed L-5 BEFORE delivery to the USAAF. Referencing the official flight manual would tend to support this assumption since the model O-62 is not listed at all. L-5 O-62 designation changed in 1942 before delivery of the first L-5 airplane. Aircraft equipped with the Lycoming O-435-1 185 HP engine. Electrical switches relocated after the first 275 aircraft. L-5A Commercial publications say the L-5A "was a modified L-5 with a 24 volt electrical system (previous airplanes were 12 volt) and that for ease of maintenance saw the deletion of the landing gear fairings as used on the L-5. These were originally built as L-5 airplanes and converted to L-5A." These publications list 688 airplanes as modified. I've been unable to locate any serial numbers for a L-5A model, my original official flight manual does not list it, and Jim Gray's original maintenance and parts manuals do not list a L-5A model. John Baker's World Stinson Database, data of which comes from FAA sources and other sources, does not show any L-5A models. For the above reasons I'm going to say the L-5A never existed, at least officially. See the Myths section below. L-5B Same as L-5 with addition of an upward hinged hatch added to provide access for a stretcher. Provisions made for float installation. Additional AN/ARR-13 radio receiver added. Gross weight increase to 2100 pounds. Some publications say the L-5B was the first version to use a 24 volt electrical system. I believe this is in error. My information indicates all L-5's used 12 volts until the L-5G model. See myths section below. L-5C Same as L-5B with addition of brackets to carry a K-20 aerial camera. L-5D Designation allocated but not used. L-5E Same as the L-5C with addition of dropping ailerons to improve short field performance. Drooping the ailerons is accomplished by turning a handle at the center top of forward carry through, at the top of the windscreen. XL-5F One L-5B (serial number 44-17103) modified to use the Lycoming O-435-2 185 HP engine. Later converted back to an L-5B. L-5G Final variant, same as L-5E with an engine change to the Lycoming O-435-11 190 HP engine. Radio equipment changed to a full SCR-274N command set. Gross weight increase to 2200 pounds. L-5 Production Serial Numbers USAAF/Army/USAF use of the Stinson L-5 Sentinel Model Number USAAF Serial Numbers L-5 275 42-14798/15072 - NOTE some publications say these were originally O-62's. Information from Homepage viewer Ron Hefner indicates they were actually delivered to the USAAF by Stinson as L-5. L-5 1,538 42-98036/99573 L-5A (688) Many publications say these were modified from L-5 aircraft with 24 volt electrical. I've not been able to find any serial numbers for a L-5A, flight and maintenance manuals don't show there was an "A" model. L-5B 711 42-99574/99735, 44-16703/17102, 44-17104/17252 (44-17103 is XL-5F Below) L-5C 200 44-17253/17452 L-5D Reserved designation not used L-5E 750 44-17453/18202 XL-5F 1 44-17103 (Built during L-5B production, Converted back to L-5B standard) L-5G 116 45-34911/35025, 57-6278 Royal Air Force use of the Stinson L-5 Sentinel Model Number RAF Serial Numbers Sentinel I 40 KJ368 to KJ407 Equivalent to L-5 Sentinel II 60 KJ408 to KJ467 Equivalent to L-5B Most RAF Sentinels were used in Burma Total L-5's 3,691 This is a total MILITARY L-5 count by serial numbers. The number of aircraft built is calculated by the assigned serial numbers. Reviewing several publications reveals slightly different production numbers. USAF Modification Program Homepage visitor Abram Karl is currently restoring Stinson L-5E, USAAF Sn: 44-17812, and Navy BuNo: 03956. Karl provides the following information about a USAF modification program to bring early model L-5 aircraft up to L-5G standard, including a change from 12 to 24 volt electrical systems. "Some of the L-5B were converted to 24 Volt airplanes. But, they were also converted to L-5G standards although they retained their L-5B serial numbers and designations. This was a fleet wide campaign in order to standardize the remaining fleet of aircraft to an all 24 Volt fleet. This was also done just prior to the airplanes (primarily the L-5) release to the Reserve units, Civil Air Patrol, Coast Guard, and finally the release for sale to other countries. The modification done to these L-5B's was not done to all aircraft just aircraft that had what were considered to a "considerable" service life remaining." The End of United States Military Service for the L-5 With one exception USAF use of the L-5 ended in 1953. L-5G aircraft 57-6278 was repurchased in 1957 by the USAF for use by the Air Force Academy as a glider tug. Some sources list it as a new build airplane, although by 1957 the Sentinel was out of production for the military for more than 12 years. The USAF Academy L-5 was still in use in 1962 when military aircraft designations were standardized between the services. The single USAF L-5G in use was redesignated U-19B. Five Army L-5 Sentinels still in use were redesignated as U-19A in 1962. Marine Corps and Navy Sentinels U.S. Marine Corps Sentinels, designated OY-1, were transferred from the USAAF. They have the following USAAF serial numbers and U.S. Navy bureau numbers. Since these aircraft were built on USAAF contracts, they are included above in the total aircraft USAAF count of L-5's. Model Number Bu Aer SN Built as USAAF SN Model OY-1 10 2747/2756 42-99512 to 42-99521 L-5 OY-1 10 2757/2766 42-99690 to 42-99699 L-5B OY-1 10 2767/2776 44-16857 to 44-16866 L-5B OY-1 12 2777/2788 44-16957 to 44-16968 L-5B OY-1 2789/2790 Assigned, canceled OY-1 147 3862/4008 44- (44-17812 is Navy BuNo: 03956) OY-1* 1 4009 44-18137 L-5E OY-1 16 4010/4025 44- OY-1 16 60460/60475 42-98448 to 42-98463 L-5 OY-1 16 60476/60491 42-98528 to 42-98543 L-5 OY-1 16 60492/60507 42-98737 to 42-98752 L-5 OY-1 12 75159/75170 42-98948 to 42-98959 L-5 OY-1 12 75171/75182 42-99040 to 42-99051 L-5 OY-1 5 120442/120446 44- OY-1 28 120447/120474 44- ---- 311 * - Bureau of Aeronuatics SN 4009 went to the Navy. At least 29 others were modified to become OY-2 airplanes. U.S. Military production of the L-5 series airplanes ended November 1945. Equipped with a 185 h.p. Lycoming engine, the L-5 gross weight is 2050 pounds (rising in later models to 2200 pounds). L-5's saw service in all theaters during WWII, but are probably best remembered for their work in the Pacific and Asia. Only the Piper L-4 was produced in greater numbers than the Stinson L-5 Sentinel. United States Coast Guard Sentinels Mike O'Rourke wrote to give me information about U.S. Coast Guard use of the Stinson L-5 Sentinel. The United States Coast Guard used 6 Stinson L-5's between 1948 and 1958. None of these aircraft were new build, rather the USCG obtained them from either the Navy or USAF. Much of their use was to locate illegal "moonshiners" in the Southeast part of the United States. All of the machines were "based" at CGAS Elizabeth City (ECG) but operated out of various airports in the S.E. US looking for moonshiners. Oh yes, don't fret about the letter "G" appendage to the aircraft type. The USCG added a "G" at the end of everything they flew (PBM-5G, PB-1G, PBY-5AG, PB4Y-2G, etc. Update 10/19/03 - Homepage visitor Jos Heman provided the following additional information about L-5 aircraft used by the U.S.C.G. "In there Mike O'Rourke gave information on Sentinels used by the USCG and suggested that some of these were designated as OY-1G and OY-2G. The former included the aircraft serialized 42-98168. However, Arthur Pearcy's book 'United States Coast Guard Aircraft' shows, on page 318, a photo of this particular aircraft with the distinct designation OY-1 painted on the tail. So, it is likely that the OY-1G and OY-2G designations were never assigned. I have attached a scan of the photo concerned." My Thanks to Jos Heyman , 92 Modillion Ave, Riverton WA 6148, Australia for the information above. Mike O'Rourke's information continued: Regarding the below; RSS = Retired-Sold as Surplus, DBR = Damaged Beyond Repair, AFSP = Acquired For Spare Parts source, SSP = Scrapped for Spare Parts. AIRCRAFT TYPE/SERIES: OY-1/2 Stinson Sentinel Model 76 USCG Date Rec'd Date Other Nos./Service No. Comm From Decom Remarks C/N 3937 05/16/52 USN 02/06/58 OY-2G USN, OY-2, BUNO 03937 USAF, L-5E-VW, 44-? Crash, DBR 4870 09/18/48 USAF 11/15/51 OY-1G, USAF, L-5-VW, 42-14870 Crash, DBR 4970 09/18/48 USAF 03/28/52 OY-1G, USAF, L-5-VW, 42-14970 RSS 5025 09/16/48 USAF 05/09/49 OY-1, USAF, L-5-VW, 42-15025 RSS 5060 09/09/48 USAF 05/09/49 OY-1, USAF, L-5-VW, 42-15060 RSS 8186 09/20/48 USAF 06/04/58 OY-1G, USAF, L-5-VW, 42-98168 RSS (see above about the "G" designation) 8293 09/20/48 USAF 10/14/48 AFSP, USAF, L-5-VW, 42-98293 SSP 8665 09/20/48 USAF 10/14/48 AFSP, USAF, L-5-VW, 42-98665 SSP 8768 09/17/48 USAF 10/14/48 AFSP, USAF, L-5-VW, 42-98768 SSP Total Units Operated: 6 + 3 AFSP = 9 1st unit acquired: 09/16/48 Last unit: 06/04/58 Total service: 117 months Actual units: 6 - rest used for type support Other Military Users of the L-5 Apparently many surplus L-5 Sentinels were delivered to other countries. The following countries are shown as flying the L-5: Ethiopia, Greece, Indonesia, Italy, Japan, Republic of Korea, Mexico, the Philippines, and Thailand. I don't have quantities to any of these countries. Approved Type Certificate Since most military aircraft are not produced to civilian airworthiness standards, Stinson did not seek an ATC for the L-5. The first L-5, model 76, was registered NX27772, for flight testing. But an approved type certificate was not issued by the CAA (Civil Aeronautics Administration). After WWII, when appropriately modified, the L-5 is eligible for a standard Approved Type airworthiness certificate under ATC #764. Near the end of WWII with production coming to an end, the remaining inventory of L-5 parts was purchased by Sentinel Aircraft, Inc. of Dexter, Michigan. Apparently the newly formed "Sentinel Aircraft Company" continued to assemble L-5's, most likely from spare parts. That must have seemed like good business sense - to use up all the surplus components - until the airplane market crashed in '49. Later a company in Phoenix actually held the rights of manufacture in the 50's, and that may have been the source of the odd-ball 1957 'new build' Air Force academy L-5. Jim Gray suggests as many as 900 L-5G's were built, only the first 115 were built for the military. Checking John Baker's World Stinson Database reveals that FAA records show a real variety of serial numbers for the L-5 models. Basic L-5 Specifications SPECIFICATIONS Span: 34 ft. 0 in. Length: 24 ft. 1 in. Height: 8 ft. 11 1/2 in. Weight: 2,050 lbs. max. Armament: None Engine: Lycoming O-435-1 of 185 hp. Cost: $10,000 PERFORMANCE Maximum speed: 130 mph. Cruising speed: 90 mph. Range: 360 miles Service Ceiling: 15,600 ft. L-5 Sentinel Myths Myth number One - Reading different commercial publications provide differing descriptions of the models. First major difference is in the number of L-5 airplanes built. Many publications (most publications actually) indicate 1,731 L-5's were built, while the serial numbers I have show 1,813 L-5's were built. Jim Gray, e-mail of Juneau, Alaska, sent me the following e-mail which MAY explain how the 1,731 number is arrived at: The L-5 serial numbers are as follows: 42-14798 thru 42-15072 = 275 (O-62) 42-98036 thru 42-99573 = 1,538 (L-5) From the second batch of 1,538 L-5 serial numbers, the Navy accepted the following airplanes for the Marines: 42-99512 thru 42-99521 = 10 (OY-1) 42-98448 thru 42-98463 = 16 (OY-1) 42-98528 thru 42-98543 = 16 (OY-1) 42-98737 thru 42-98752 = 16 (OY-1) 42-98948 thru 42-98959 = 12 (OY-1) 42-99040 thru 42-99051 = 12 (OY-1) 82 Total OY-1 from L-5 production 1,538 + 275 = 1,813 - 82 (OY-1) = 1,731 Apparently the OY-1's aren't considered L-5's by whoever made this computation. They shouldn't be subtracted because they are right out of the L-5 serial numbers, built on USAAF contracts. These were aircraft built for the USAAF as L-5's and diverted to the Marines. Based on the serial numbers, and Jim Gray's theory, I believe the actual number of L-5's built is 1,813 including the 82 for the Marines. Myth number two - was there an L-5A airplane? One commercial publication indicates the L-5A was a new build airplane and the L-5B a modification. Three other commercial publications indicate the L-5A is the modified airplane and the L-5B is the new build. Since serial numbers are assigned to L-5B's and not L-5A's, I believe the L-5A is the modified airplane, IF there ever was an official L-5A. Taking that one step further, it may be there never was an "A" model. Again Jim Gray E-mailed me to provide additional information. Gray's source is original maintenance and parts manuals for the L-5. "In the 1947, 1950, and 1953 USAF L-5 parts catalogs (unlike the earlier ones), there is an extra column in the right margin of each page used to show which model(s) each part is used on. A note at the front of the manual states that for this system they will use an 'A' to designate L-5's, a 'B' to denote L-5B's, a 'C' to denote L-C's, and so on... This is probably another source of the L-5A confusion. They are NOT saying these are L-5A's, just using the lettering system to make referencing parts simpler. For example, it is easier to list the usage for a part as: A-G, or A-B, rather than write it as _-G, or _-B." From the information he has, Gray believes there never was a L-5A model. He says there seems to be an assumption that if there was a "B" model there must have been an "A" model before it. My original copy of the official "Pilot's Flight Operating Instructions for Airplanes L-5, L-5B, L-5C, L-5E and L-5G, plus Navy model OY-1," identified as AN 01-50DB-1, is dated 10 August 1945. Note this flight manual lists the L-5, L-5B, L-5C, L-5E, L-5G and OY-1. There is no mention of an L-5A model. I've searched but so far have found no source to indicate what serial numbers were ever assigned to a L-5A model. In my opinion if there was an official model L-5A, the USAAF would have included it with the designations the flight, maintenance and parts manuals covered. From the information I have, and Jim Gray's maintenance and part manual information, I now believe there never was an L-5A model, at least officially. Myth number three - which are the 24 volt airplanes? Most commercial publications indicate the L-5B was the first to use a 24 volt electrical system. Contrary to the commercial publications, the official USAAF Pilot's Flight Operating Instructions for Airplanes L-5, L-5B, L-5C, L-5E and L-5G, plus Navy model OY-1," indicates the L-5G was the first airplane to have a 24 volt electrical system. Jim Gray provided additional information he obtained from the original maintenance and parts manuals for the L-5. These manuals show that only the L-5G has a 24 volt electrical system. Gray's conclusions from his original maintenance and parts manuals confirms the information I have from my original flight manual. Assuming my original flight manual, and Gray's original maintenance and parts manual are both correct, that indicates that the commercial publications are in error when they say L-5B's and later have 24 volt electrical systems. Official publications indicate only the L-5G is a 24 volt airplane. The Final Stinson Production Airplane - the 108 The next, and final light aircraft designed and built by the Stinson Division of Consolidated Vultee was the model 108 Voyager, descried separately. Stinson model 76 L-5 Sentinel Bibliography Commercial Publications Bowers, Peter M., and Swanborough, Gordon. "United States Military Aircraft Since 1909. My copy is the 1989 edition by the Smithsonian Institution Press. Pages 572 & 573 cover the Stinson L-1, pages 574 & 575 cover the Stinson model 76 L-5 Sentinel. Brief mention is made of the YO-54 on page 574. Juptner, Joseph, U.S. Civil Aircraft, Vol. 8, 1980, Covers all Stinson light aircraft ATC's, #709 model 105, #738 Voyager 10, #764 L-5 and #767 model 108. This book has been reprinted and is available again and recommended. Wegg, John. "General Dynamics Aircraft and their Predecessors," 1990. Pages 137 to 144 cover the YO-54, L-1 and L-5. This is an excellent reference for all Stinson aircraft including the model 108. Published in the United States by the Naval Institute Press, also in England by Putnam. One of the Putnam series newer, larger style format. ISBN 0-87021-233-8, Library of Congress 89-60237. This is my favorite book on the Stinson light aircraft. Military Publications Department of Defense (previously the War Department) - the following manuals are printed by the government for Stinson's used by the U.S.A.A.F and U.S.A.F. AN 01-50DB-1 Pilot's Flight Operating Instructions for Airplanes, Army Models L-5, L-5B, L-5C, L-5E, L-5G, Navy Model OY-1, 10 August 1945. "This publication replaces AN-01-50DB-1 dated 20 March 1945. Commanding Officers will be responsible for bringing this Technical Order to the attention of all pilots cleared for operation of the subject aircraft as well as those undergoing Transition Flying Training as contemplated in AAF Regulation 50- 16. This publication shall not be carried in aircraft on combat missions or when there is a reasonable chance of its falling into the hands of the enemy. Published under joint authority of the Commanding General, Army Air Forces, and the Chief of the Bureau of Aeronautics. Notice: This document contains information effecting the national defense of the United States within the meaning of the Espionage Act, 50 U.S.C.,31 and 32 as amended. Its transmission or the revelation of its contents in any manner to an unauthorized person is prohibited by law." Added 4/5/99. AN 01-50DB-4 Parts Catalog for Airplanes, Army Models L-5, L-5B, L-5C, L-5E, L-5G, Navy Model OY-1, 25 January 1946. Restricted. Title page includes the following notes: "This publication replaces AN-01-50DB-4 dated 25 March 1945. Published under joint authority of the Commanding General, Army Air Forces, and the Chief of the Bureau of Aeronautics. Notice: This document contains information effecting the national defense of the United States within the meaning of the Espionage Act, 50 U.S.C.,31 and 32 as amended. Its transmission or the revelation of its contents in any manner to an unauthorized person is prohibited by law. Courier-Journal Job Ptg. Co., Louisville, KY. February 1946 - 5,100." Thanks to John T. Baker at John@hangar9aeroworks.com, 4/5/99, for this entry. AN 01-50DB-4, Airplane Parts Catalog for Army Models L-5 and L-5B, Navy Model OY-1, British Model Sentinel 1 & II, 15 September 1944. It contains a similar security warning. Printed by Copifyer Lithograph Corp, Cleveland, Ohio, September 1944, 12,400 printings. Thanks to John T. Baker at John@hangar9aeroworks.com, 4/5/99, for this entry. AN 01-50DB-2. Revised 1 November 1954. It is a service manual for the L-5, but the cover and title page is missing. Thanks to John T. Baker at John@hangar9aeroworks.com, 4/5/99, for this entry.