© James H. Gray
Sentinel Owners and Pilots Association
Observer or Ambulance?
Stinson L-5 Sentinels can be generally categorized by two basic variants: "Observer" models and "Ambulance" models.
Though unofficial, these names were and are commonly used to refer to the basic fuselage styles. The "Observer" has a slim
aft fuselage section and features a wrap-around style rear window while the "Ambulance" fuselage is deep and boxy aft of
the pilots seat to accomodate cargo or a standard Army litter. All L-5B through L-5G series airplanes are "ambulance"
models and feature a 6-foot long loading door on the starboard side. The difference between the two basic designs is easily
seen in the photo's below.
|Early models of the L-5 are sometimes
called "observers" and are easily
identified by the slender aft fuselage
section and wrap-around rear window.
Approximately 1,800 of these models
were built in 1942-43.
|The L-5B through L-5G models are
popularly called "ambulances" and
feature a deeper rear fuselage with a
6-foot long door that hinges downward
to accomodate a stretcher. Around
1,800 of these models were built from
|.(John Hitzke's L-5 Observer)
|.......................(John Gronemeyer's L-5E Ambulance)
There were six production versions of the two fuselage styles but many different designations have been applied. All aircraft
are collectively and officially termed Sentinels. The O-62, L-5, L-5B, L-5C, L-5E, and L-5G are the only U.S Army
identifiers used for the producrion models. The L-5 is the "observer" model and the L-5B through L-5G series are
"ambulance" models. No production aircraft were manufactured under the designations L-5A, L-5 D, or L-5F as these
were prototypes of designs that never made it into production. Contrary to popular belief , the so-called L-5A was not an
official variant. This is also borne out in the official aircraft operating and repair manuals. What most people referto as the
'A' were the aircraft manufactured subsequent to thr O-62's.. The actual L-5A variant was to have incorporated an
inverted Ranger six cylinder inline engine and a 24-volt electrical system, but due to engine shortages the model was never
manufactured. Likewise, the L-5 D was an improved "observer" model that reached the prototype phase but was cancelled
before production began. A single L-5B did become a test bed for an experimental propeller in 1948 and temporarily held
the XL-5F designation but that modification was later removed.
O-62 ('O' for Observation) was the original designation for the Sentinel and was used before the 'L' (for Liaison) category
was established in April 1942. Apparently, no airplanes were actually delivered under the O-62 label although the first 275
Sentinels were ordered as such.
OY-1, and OY-2 were the U.S. Navy and Marine designations for the "observer" and "ambulance" models respectively. A
review of military literature of the 1940's and 1950's reveals that they were referred to collectively as OY's.
Sentinel I and Sentinel II were the British designations for L-5 and L-5B airplanes respectively. All of these aircraft served
with the RAF in the China-Burma-India theater (CBI)
U-19 and U-19B were designations adopted by the U.S. Air Force for the few aircraft remaining in inventory in the 1960's
at the U.S. Air Force Academy..
|L-5E on EDO 2425 Pontoons
|(photo: courtesy Bill Stratton, ILPA)
All airplanes can be identified by serial number (see the Production Data page), but there are a few obvious details that can
help a careful observer quickly identify various models. This in not a complete list of all differences, just review of the main
L-5 : Has the "observer" style fuselage with wrap-around rear window. The rear seat door and windows are triangular.
Electrical switches are located on a console mounted above the pilot's left shoulder.
O-62 : (i.e. early L-5) Same as the L-5 "Observer" but the electrical switches are located on the lower left side of the
instrument panel. A full-length cuff, similar to those seen on pre- and post-war civilian Voyagers, covers each landing gear
leg. These cuffs were usually removed in service, leaving a telltale elliptical opening in the fuselage "blister" fairing. This leg
cuff was deleted on all subsequent models and a modified blister fairing was incorporated.
L-5B: Has the "ambulance" style fuselage with a two-section downward hinging cargo door on the starboard side (the
foreward section of the door acts as the rear seat entry). The rear seatback folds foreward, the aft control yoke is
removable, and the rear side windows are elongated rather than triangular.
|Ambulance Door on 'B' through 'G' Series
|(photo: courtesy Ken Gillis)
L-5C: Identical to the 'B' with the addition of a transverse bracket near the floor behind the rear seat to accomodate a
Folmer-Graflex K-20 aerial camera. To facilitate photography a small window with a sliding aperture is located on the belly
under the camera mount..
L-5E: Similar to the 'C' with the addition of "drooping" ailerons that can be manually lowered up to 15º (like flaps) to
enhance short-field and low-speed performance. The visual cue is a small handle and pulley mounted to the right above the
pilot seat on the wingspar carry-through structure. Also, some aircraft (designated L-5E-1) were fitted with larger
850X6.00 tires, wheels, and brakes.
L-5G: Similar to the L-5E-1 but incorporating a 24-volt electrical system. One difference is the battery which is mounted
on the firewall under the instrument panel instead of between the front and rear seats. Another clue is the external power
plug which is located foreward of the pilot's door instead of behind it. An improved 190 hp Lycoming O-435-11 engine is
installed, indicated by a manifold pressure gauge located on the instrument panel.
All airplanes were initially fitted with Sensenich or Fahlin fixed-pitch wooden propellers but many were later retrofitted with
metal-bladed Koppers or Hartzell variable-pitch units plus a manifold pressure gauge and propeller control in the cockpit.
The Clevenger is a highly modified biplane version of the L-5 that was used for cropdusting in the 1950's and 60's. The
rear seat, rear flight controls, and rear windows were removed to accomodate a chemical hopper. A second wing from a
Luscombe 8A Silvaire was mounted at the bottom of the fuselage with interplane struts connecting it to the upper wing. A
Continental W-670 or W-680 radial engine replaced the horizontally-opposed Lycoming and was left uncowled. A few
Clevengers can still be found but the lower wing panels have usually been removed and the fuselage returned to a two-seat
|(photo: courtesy Phil Livingston)
|Welcome to the Stinson L-5 Data Pages
A guide to L-5 variants
|* * * * * * * * * *
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