Country of origin:

United States of America

Description:

Two-seat air-observation-post and liaison aircraft

Power Plant:

(L-5)

One 142 kw (190 hp) Lycoming O-435-1 six-cylinder horizontally-opposed air-cooled engine

Specifications:

History:

The L-5 Sentinel was not directly developed from the Stinson Voyager light touring monoplane and, when compared, the Sentinel had more power and a strengthened airframe to enable it to be flown in the role of air-observation-post under combat conditions.  Light aircraft which were used for communications duties in the frontline during wartime often received rough treatment as they regularly were involved in landings and take-offs from roads and paddocks etc.

Some 3,590 Sentinels were built for the American armed services and of these 288 were supplied to the US Navy as the OY-1 and some 18 as the US Navy as the OY-2, a number later being transferred to the US Coast Guard and the US Marine Corps. Some 40 of the L-5 and 60 L-5Bs were supplied to the RAF under the Lend-Lease Programme, these becoming known as the Sentinel Mk 1 and Mk 2, and served in Burma. The type served with distinction for 15 years, and was flown in the face of enemy action in most theatres of operation during World War II and in Korea. Approximately 30 OY-1 aircraft were converted to OY-2 configuration between 1948 and 1950. A toaal of eighty was supplied to the US Coast Guard, one from Navy stocks, seven from the Air Force, and two were reduced o spare parts.

The prototype Sentinel, was an experimental tandem seat version of the  Stinson HW-75 known as  the Model 105.  It was first designated as the Model 75B with a 75 kw (100 hp engine) known as the V-76 (NX27772), was flown for the first time on 28 June 1941. It later became then 75C when fitted with a 93 kw  (125 hp) Franklin engine. It was evaluated by the military for liaison work but was rejected.

The aircraft NX27772 ws a clean sheet replacement for the V-75C.  There were some visual similarity but it was a completely new design known as the Model 76. This was the true prototype that became the L-5 and was fitted with a 131 kw (175 hp) Lycoming O-435 engine which was  upgraded to 138 kw (185 hp) on production aircraft. First order for the type was for 275 aircraft and these became known as the O-62 but seven months later in November 1942, before any aircraft were delivered, that was changed to L-5. A further order was placed for 1,538 aircraft.  Further orders comprised 712 L-5Bs, 200 L-5Cs, 500 L-5Es, 250 L-5E-1 and 115 L-5Gs.

The L-5Cs had mountings for K-20 cameras but the cameras were not installed. All aircraft after the L-5C had the camera mount. The underwing racks were tested in the United States with 45 kg (100 lb) bombs but were never employed in combat.  However, the wing racks were used extensively for carrying 68 kg (150 lb) para-packs in the Burma and Philippine campaigns.

After World War II the type was operated by the air forces of India, Thailand, Pakistan, Philippines, Natiomalist China, Korea, Japan, Mexico, Brazil, Venezuela and Italy. One L-5 was officially loaned to the RAAF.

Because of the necessity to conserve scarce construction materials for fighters and bombers, it was necessary for the L-5 aircraft to use, where practicable, timber and non-critical materials in its construction. Thus the fuselage was an all-welded structure of steel tube, the engine cowls being formed from sheet metal. The wings and tailplane were built from wood, plywood sheets being bonded to the under-surfaces of the wings and tailplane, the whole aircraft being covered in fabric.

Production of the L-5 totalled 3,590 machines, with the designation being changed to O-62 after 275 aircraft had been completed.  In 1943 the L-5A appeared with a modified electrical system.  The L-5B was an ambulance version, with the fuselage altered slightly to provide a loading hatch to the rear of the cabin, and some 730 examples of this model were delivered. The L-5C had a K-20 reconnaissance camera installed and production comprised 200 aircraft. The L-5E had modified ailerons and production of this model totalled 750. A variant of the L-5E was the L-5E-1 with larger wheels and modified brake drums.  The L-5G was fitted with the O-435-11 engine of 142 kw (190 hp) in lieu of the O-435-1 and had a Koppers Aeromatic constant-speed propeller, a 24 volt electrical system and a revised instrument panel, but only 115 had been completed when the war concluded and orders were cancelled.

The type served in many theatres of operation and operated in the Medevac, re-supply, reconnaissance, artillery spotting, target marking, personnel transport, communication, and search and rescue roles.  Some experimentation with armament led to crews carrying a Thompson machine gun and hand grenades. At one stage underwing racks were fitted to carry 45 kg (100 lb) bombs.

After World War II many served with the forces of Italy, Japan, Mexico, the Philippines and Thailand.  The Sentinel had good STOL characteristics, these being provided by the tailwheel undercarriage layout which spread the load, and wide-span flaps and leading-edge wing slots.

A small number of Sentinels on loan served with the RAAF in Australia and New Guinea and, as well as being used for communications and spotting duties, were used to evacuate wounded troops from forward areas.  They are also known to have been used to recover RAAF airmen shot down in New Guinea.  These aircraft, although basically attached to RAAF units, carried their US serial numbers.  The first attached to the RAAF was an ex USAAF L-5 (c/n 76-1370 – ex 42-99129) which undertook service trials. It was taken on strength by No 37 Squadron on 3 May 1944 and was allotted the serial A38-2 but it seems this was never painted on the aircraft (A38-1 was a Stinson Reliant).  The L-5 was returned to the USAAF on 1 February 1945.

In 1945 a number of war surplus Douglas C-47s were flown to Australia from the United States Foreign Liquidation Commission in the Philippines and it is believed four Sentinels were brought to Australia as freight.  These were allotted registrations VH-BEE, VH-BEN, VH -BFR and VH-BGQ. A further two arrived a few years later, becoming VH-ALQ and VH-CSA.  In more recent years further examples have been imported from a variety of sources, including India. One example for a period operated in Tasmania in the late 1950s and at one stage was used for crop-dusting near Launceston in September 1958.

About 14 Sentinels are known to have an Australasian connection.  In 1991, as noted, four Sentinels were imported from India for restoration as warbird projects. A further two arrived from the Philippines in 1979 and 1985.  Sentinels have appeared on the Australian Civil Register over the years, a few of these being known to have served with the US 25th Liaison Squadron in the Pacific campaign.

Registrations allotted to the type have included: VH-BEE, an L-5 (c/n 76-949 – ex 42-98708), registered in July 1947, which became VH-BOE in December 1949, being withdrawn from service in December 1963; VH-BEN, an L-5B (c/n 76-3312 – ex VR-HEO, 44-17025), registered in April 1954 and, after an accident at Coen, QLD in 1971, placed on display in the Sid Beck Museum at Mareeba, QLD; VH-ALQ (c/n 2751 – ex 42-99477) registered from April 1947 to August 1955; VH-BGQ, an L-5 (c/n 76-1706 – ex 42-99470); VH-BFR, an L-5 (c/n 76-2744 – ex 42-99465), first registered in October 1947; VH-CCO, an L-5B (c/n 76-2178 – ex VT-CCO, 44-16890); VH-CHN, an L-5 (c/n 76-1613 – ex VT-CHN, 42-99399); VH-CDF, an L-5B (c/n 76-2380 – ex RP-C545, 44-17643); VH-NLR, an L-5 (ex VT-CDL, 42-99331); VH-CRO, an L-5B, (c/n 76-1886 – ex 42-99645), which became VH-PWZ; and VH-CSA, an L-5E (c/n 75-4026 – ex 44-17739), first registered in January 1954.  The latter was operated with Crowley Airways in New Guinea at one time.

Other aircraft known to have been imported include: L-5E c/n 76-4069 (ex 44-17782); L-5 c/n 76-1572 (ex VT-CDL, 42-99381); and L-5 c/n 76-1886 (ex VT-CRO, 44-99645).