Piper O-59/ L-4 Grasshopper

The Piper O-59/ L-4 Grasshopper was the most successful of three models of commercial light aircraft that served as liaison and artillery spotter aircraft for the USAAF, filling a gap left by the slow development of the Stinson O-49/L-1 Vigilant

During the 1930s the speed, complexity and weight of all military aircraft increased, until it started to become clear that the existing observation aircraft (in the USAAF the three-man North American O-47), were no longer really able to perform some of their duties, in particular the army liaison and artillery observation roles. After some debate within the service, the Air Force decided to order a low speed liaison aircraft, capable of operating from unimproved airfields. The winner of the contest with the Stinson O-49 Vigilant, a high winged monoplane that resembled the more famous Fieseler Storch. However work on the O-49 progressed slowly, and by 1941, in the aftermath of the stunning German victories of 1940, the ground forces were no longer willing to wait. The idea of using commercially available light aircraft had been discussed several times, but always rejected but in the summer of 1941 Piper arranged to provide 12 Piper Cubs for the Second Army’s June manoeuvres in Tennessee. They also invited Taylor and Aeronca, their two biggest rivals in the light aircraft industry, to take part in the manoeuvres. In the end four aircraft were rented from each the three companies, to get the total of twelve, and were flown and maintained by civilians.

Piper L-4 Grasshopper over the mountains
Piper L-4 Grasshopper
over the mountains

Piper provided the J-3C-65 Cub. Like the Taylor and Aeronca aircraft, these were powered by the 65hp Continental O-170-3 flat four air cooled engine, which gave all three their commercial names, all some variant on the Model 65. The Piper Cub was built around a steel and aluminium tube framework with wooden wing spars all covered with fabric. The YO-59 had a top speed of 87mph, a range of 260 miles and a crew of two carried in tandem.

This first experiment was clearly a success, for it was repeated during the Third Army’s manoeuvres in Texas in July and Louisiana in August. Unsurprisingly this didn’t go down well in the USAAF, but the lack of any suitable official military aircraft for the exercises meant that they didn’t really have any good arguments to use. The Materiel Division pointed out that the aircraft would need to be flow by military pilots and tested by military mechanics to see if they were suitable for service. General Arnold was also worried that these unofficial efforts were apparently more successful than the O-49 programme, and ordered 24 hour working at Stinson to try and equip two squadrons with the O-49 for use in the next round of manoeuvres.

Piper L-4 Grasshopper over the Volturno river Italy Piper L-4 Grasshopper over the Volturno river Italy

The Air Force might not have been happy, but the Army clearly was, as in August 1941 the Assistant Secretary of War ordered General Arnold to produce service test aircraft from Piper, Taylor and Aeronca. The advantages of being able to use commercial light aircraft were clear – they were much cheaper, and took around 300 man-hours to build, compared to 6,000 man-hours for the much more complex O-49!  

At this time there was also a debate about the potential uses of these slow flying unarmed aircraft, with many believing that they would be unable to survive over the frontline. As a result the Air Force’s Combat Command suggesting creating a new classification – ‘L’ for Laision – to be used on these light ‘puddle jumpers’. The general belief was that these aircraft would be most useful in areas out of the reach of enemy fighters, but could also operate over friendly lines, as long as some fighter support was available. They would still be able to perform their main role as artillery spotters without having to stray into enemy held territory. The group forces were so keen on the type that at a conference in January 1942 they requested 2,750 examples for the field artillery, 13 aircraft for every infantry division and more for the cavalry, coastal artillery and anti-aircraft brigades, a total of 4,000 aircraft!

The Air Corps designated the service test aircraft as the Taylorcraft YO-57, Aeronca YO-58 and Piper YO-59. When these aircraft were tested, they were found to be inferior to the O-49, but the demand for light aircraft was so high and O-49 production so slow that there was no real alternative. In November 1941 the General Staff suggesting placing orders for the commercial aircraft, and the Material Division placed an order for 617 light aircraft. This was split between 342 O-57s, O-58s and O-59s and 275 Stinson model 76s, an improved version of an existing Stinson commercial aircraft.

Piper L-4 Grasshopper from the left
Piper L-4 Grasshopper
from the left

It soon became clear that this wasn’t going to be enough. After the January 1942 conference another 1,000 aircraft were ordered, followed six months later by 1,960 more.

In November 1942 a group of civilian and military agencies came to gether to discuss their requirements for 1943. The Civil Air Patrol, which had to carry out 600,000 miles of coastal patrols per week and 40,000 miles of courier flights every day asked for 200 Grasshoppers, while the Civilian Pilot Training Program asked for 1,220. The Office of Coordinator of Inter-American Affairs asked for 100 aircraft and the Army Ground Forces asked for another 2,500! The AAF Base Services asked for 1,511 aircraft and the OSS wanted 1,700. In total the conference asked for some 7,231 L-2 class aircraft! The Joint Aircraft Committee approved the production of 3,000 L-2s, L-3s and L-4s.

In April 1942 the change from O to L was officially made, with the Piper O-59 becoming the Piper L-4. Somewhat unfairly, given that it had been Piper that had originally been involved in the manoeuvres, the three types were often described as the ‘L-2’ class.

In 1943 the Field Artillery decided that it no longer wanted the L-2 or L-3 after a number of accidents at Fort Sill, and requested the L-4 instead. The Air Corps preferred to offer the L-5, but the Artillery believed that it was too complex to maintain on the front line and ‘too hot’ for Field Artillery pilots. The L-4 was also much cheaper to produce - $2,432 per aircraft in 1942 compared to $10,165 for the L-5!

By the end of December 1943 the USAAF and the Army Ground forces were operating 2,079 L-4s and it remained a ‘standard’ type in 1944, while the L-2 and L-3 were reduced to ‘limited standard’. A total of 1,904 L-4s were built during 1944, the most of any liaison type. Eventually an impressive 5,611 L-4s and improved L-14s were accepted by the USAAF.

The L-4 was the first of these light liaison aircraft to see combat. Three operated from the carrier USS Ranger (CV-4) on 9 November 1942 during Operation Torch, acting as artillery observation aircraft for the naval guns.

Piper L-4 Grasshopper from the Right Piper L-4 Grasshopper from the Right

This wasn’t the only time the L-4 operated from ships. Some of them took off from modified Landing Ship, Tanks (LSTs) that had been given pierced steel planking flight decks during the invasion of Sicily of 10 July 1943. The L-4 couldn’t land back on these ships, so had to hope that enough of Sicily was soon captured!

The L-4 was also used with the Brodie Device, which consisted of a 300ft long cable carried between two towers mounted on an LST. The L-4 was given a nose mounted steel hook, which allowed it to take off or land from the cable. When landing the hook would catch the cable, and the slow moving aircraft would come to a halt while still suspended in mid air! This device as first used in action during the invasion of Okinawa

The L-4 saw extensive service in more conventional roles, serving as an artillery spotter, liaison aircraft and ambulance. Some were even armed with bazookas and used as light attack aircraft! The type remained in service into the Korean War, before being replaced with the Cessna L-19/ O-1 Bird Dog. In combat it’s slow speed and small size made it surprisingly survivable over the frontline, making it difficult for high speed fighters to actually shoot it down – as long as the attack was spotting in time, the L-4 could fly low and slow in circles, going so slowly that the Bf 109s and Fw 190s couldn’t get a shot off before zooming past! 



The YO-59 was the designation for the four service test aircraft, officially ordered after the summer manoeuvres of 1941.

O-59/ L-4

Piper L-4 Grasshopper over scenic valley
Piper L-4 Grasshopper over scenic valley

The O-59 was the first production version. It had a 6 volt electrical system and carried military radio equipment. 140 were built, of which 40 were ready in time for the August and September 1941 manoeuvres in Tennessee and Texas (one advantage of using an existing type).

O-59A/ L-4A

The O-59A was given a larger and wider observer’s position, with a seat that could rotate through 180 degrees and face to the rear. The glazed area was increased, with larger windows to the side and above the observer, extending well behind the trailing edge of the wing. This model was built in large numbers, with 671 built as the O-59A and 277 as the L-4A.


The L-4B was a dedicated version produced for the US Army Field Artillery. It was similar to the L-4A, but oddly wasn’t fitted with a radio, a rather odd decision for an aircraft that was meant to liaise closely with ground units. Unsurprisingly many of the 980 L-4Bs were later given SCR-610 radios that operated on the same frequencies as the artillery. 


This was the designation for eight civilian Model J-3Ls that were impressed into USAAF service. 


This was the designation for five civilian Model J-3Fs that were impressed into USAAF service. 


This was the designation for seventeen civilian Model J-4Es that were impressed into USAAF service. 


This was the designation for forty-three civilian Model J-5As that were impressed into USAAF service. 


This was the designation for thirty four civilian Model J-4Gs that were impressed into USAAF service. 


The L-4H was given a new one piece windscreen, replacing the three- piece screen on earlier aircraft. It had no electrical system, and thus no radio, but despite this was produced in very large numbers, with 1,801 completed.


The L-4J was the last wartime version of the aircraft, and was very similar to the L-4H. A total of 1,680 were built. Some were given Beech-Roby controllable pitch propellers, but these weren’t a success, and were soon replaced with fixed pitch units.


The TG-8 was a training glider based on the L-4. The engine and fuel system were removed and a new nose replaced them. The glider was 23ft long. Entry was via a hinged canopy on the front cockpit. 250 went to the USAAF and three to the Navy (as the XLNT-1).


The US Navy purchased 230 Piper Cubs for use as training aircraft, designating them as the NE-1 (E being the Navy code for Piper). They had dual controls.


The NE-2 was the designation for another 20 aircraft purchased by the Navy. They were similar to the L-4J, with the controllable pitch propellers.

HE-1/ AE-1

The HE-1 was the designation for 100 Piper J-5C Cub Cruisers purchased by the US Navy in 1942. They had a modified turtle deck that could be raised to allow it to carry a wounded man on a litter. The HE-1 became the AE-1 when the designation changed in 1943. These aircraft were given a more powerful 100hp Lycoming O-234-2 four cylinder engine.

Piper L-4H Grasshopper
Engine: Continental O-170-3 flat four air cooled engine
Power: 65hp
Crew: 2
Span: 35ft 2in
Length: 22ft 4in
Height: 6ft 8in
Empty weight: 740lb
Maximum take-off weight: 1,220lb
Max speed: 87mph
Cruising speed: 75mph
Service ceiling: 11,500ft
Range: 260 miles

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How to cite this article: Rickard, J (10 September 2019), Piper O-59/ L-4 Grasshopper , http://www.historyofwar.org/articles/weapons_piper_O59_L4_grasshopper.html

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