P.Bowers Curtiss Aircraft 1907-1947 (Putnam)
Model HS Series (Model 8)
In mid-1917, Curtiss converted the three-seat H-14 twin pusher flying-boat into a single-engined model and assigned the new designation of HS for Model H, Single-Engine.
With the US now involved in the war, the Navy ordered a modified version of the HS into largescale production. Existing Curtiss plants were overloaded and Curtiss couldn't meet the Navy's requirements for the HS. Consequently, five other manufacturers were given Navy contracts to build HS-boats under licence from Curtiss. Of the 1,092-aeroplane total, Curtiss built 675. Production ended when contracts were cancelled after the Armistice; only aeroplanes in an advanced stage of construction were completed in 1919. The type remained in Navy service into 1928 and in civil use in the US and Canada for a few years longer.
HS-1 - A traditional pusher flying-boat with 200 hp Curtiss V-X-3 engine driving a three-blade propeller, converted from the unsuccessful H-14 airframe.
On 21 October, 1917, the HS-1 prototype was the test bed for the first flight of the US Government's new 360 hp twelve-cylinder Liberty engine and was later converted to HS-1L standard.
HS-1L - Significant changes were made in the production version of the HS-1, which was designated HS-1L because of the Liberty engine installation. The most noticeable difference from the prototype was the use of horn-balanced ailerons on both wings - these were the first used by Curtiss on a production aeroplane - and two degrees of dihedral in the outer wing panels. Up to 360 lb (163 kg) of bombs or depth charges could be carried on underwing racks and the defensive armament was a pair of .303-calibre Lewis machine-guns on a Scarff-ring around the front cockpit. Colouring was the new overall light grey adopted as standard Navy camouflage into 1920.
The exact number of HS-1Ls flown is not known because some ordered as HS-1L were completed as HS-2L and others were converted later. Of the six builders of HS boats, only Curtiss and L.W.F. delivered HS-1Ls. Approximately 163 HS-1Ls were delivered to France in 1918, where they operated from ten US Naval Air Stations. The first ones arrived on 24 May and the first patrol was flown on 13 June.
In 1920, the Naval Aircraft Factory fitted stock HS-1L wings to fifteen new tractor-type aeroplane fuselages to create the PT-1 torpedo seaplane (serials A6034/6048).
HS-2L - The 180-lb (82 kg) depth charges carried by the HS-1Ls proved to be ineffective against submarines; heavier charges (230 lb/l04 kg) were needed but the HS-1L could not carry them. This deficiency was overcome by the old Curtiss trick of increasing the wing span; a new centre-section 12 ft (3,65 m) wider was fitted and one 6 ft (1,82 m) panel was installed between each lower wing panel and the hull to create the longer-span HS-2L. The vertical tail was also enlarged and balance area was added to the rudder.
The contract quantities and actual deliveries of HS-boats from the six manufacturers are listed here. Average unit cost was $30,000.
Model Manufacturer Ordered Delivered US Navy serial numbers
HS-1L/HS-2L Curtiss 675 675 A800/815, A1549/2207*
HS-1L/HS-2L L.W.F. 300 250 A1099/1398**
HS-2L Standard 150 80 A1399/l548
HS-2L Gallaudet 60 60 A2211/2276
HS-2L Boeing*** 75 25 A4231/4255
HS-2L Lougheed 2 2 A4228/4229
HS-2L Assembled by 25 A5564/5569, A5615/5619,
Navy from A5787, A5808, A6506,
spare parts in A6507/6513, A6553/6556
* HS-2Ls start at A1820.
** HS-2Ls start at A1223.
*** The Boeing-built HS-2Ls could be identified by the absence of lower wing ailerons.
At least nineteen of the 182 HS-boats delivered to France were the HS-2L model. Some HS-2Ls fitted with improved 400 hp Liberty engines remained in Navy service until September 1928. After 1920, standard colouring was grey hull with silver wings and tail and chrome yellow on top surface of upper wing and horizontal tail. Thirty surplus HS-2Ls were sold to the Canadian Air Force and eventually came into civil use into the 1930s. Others were used for short-haul airline work in the US in the late I 920s. The US Navy fitted HS-2L wings to more tractor-type fuselages to create eighteen PT-2 torpedo aircraft (A6326/6343).
HS-3 - The HS-3 was a major redesign of the HS-1L/HS-2L that fitted HS-2L wings to a completely new hull and vertical tail design developed jointly by Curtiss and the Navy. The major change was widening the hull to eliminate the sponsons. The Armistice ended official interest in the HS-3 as a Service type and only four were completed by Curtiss (A5459/5462) and two by the Naval Aircraft Factory (A5590, 5591) at $23,570 each less engines.
Patrol f1ying-boal. Two or three seats in two cockpits. 360 hp low-compression Liberty 12.
HS-1L HS-2L HS-3
Span. 62 ft 1 in 74 ft 1 in 75 ft 6 in
(18,92 m) (22,58 m) (23,01 m)
Length 38 ft 6 in 39 ft 38 ft 7 in
(11,73m) (11,88m) (11,76 m)
Height 14 ft 7 in 14 ft 7 in 14 ft 7 in
(4,44 m) (4,44 m) (4,44 m)
Wing area 653 sq ft 803 sq ft 824 sq ft
(60,66 sq m) (74,59 sq m) (76,54 sq m)
Empty weight 4,070 lb 4,300 lb 4,550 lb
(1,846 kg) (1,950 kg) (2,064 kg)
Gross weight 5,910 lb 6,432 lb 6,432 lb
(2,680 kg) (2,917 kg) (2,917 kg)
Maximum speed 87 mph 82,5 mph 89 mph
(140 km/h) (132,76 km/h) (143,22 km/h)
Climb in 10 min 1,725 ft 2,300 ft 3,120 ft
(526 m) (701 m) (951 m)
Service ceiling 2,500 ft 5,200 ft 6,500 ft
(762 m) (1,585m) (1,981 m)
Endurance 4,2 hr 4,5 hr 5,3 hr
Armament. One flexible 0.30-in Lewis machine-gun (all models), two 230 lb (104 kg) bombs (HS-2L and HS-3)
G.Swanborough, P.Bowers United States Navy Aircraft Since 1911 (Putnam)
Curtiss HS Series
The Curtiss HS-1 was a single-engine pusher flying-boat that was essentially a scaled-down version of the earlier twin-engine H models. In fact, the designation letters stood for 'H, Single engine'. Actually, the new H-boat stood about half-way between the smaller F and the larger H-12.
The original power plant of the HS-1, which was introduced early in 1917, was the 200 hp Curtiss V-X-X, a watercooled V-8. On October 21, 1917, the HS-1 was used as the test-bed for the first flight of the new twelve-cylinder Liberty engine, which in its original form developed 375 hp and was destined to become the major American aeronautical contribution to World War I and one of the world's great aircraft engines. In its later versions, this engine produced 420 hp, but was generally referred to as a 400 hp power plant.
Following the successful marriage of the HS-1 airframe and the Liberty engine, the Navy ordered the HS-1 into large-scale production as the Navy's standard coastal patrol flying-boat. The numbers required were beyond the capacity of the Curtiss plants, so additional manufacturers were asked to produce the boats under licence from Curtiss. The original Curtiss order was for 664 machines. The Standard Aircraft Corporation was given an order for 250, of which the last 50 were cancelled; Lowe, Willard and Fowler was given an order for a total of 200, but 50 were cancelled. (This firm later rebuilt one of its own HS-boats, A1171, which was then given the new serial number A5630.) The Gallaudet Aircraft Corporation produced 60, the Boeing Airplane Company built 25 of an original order for 50, and the Loughead Aircraft Corp. (known today as Lockheed) built two. The Boeing versions could be distinguished from all the others in that they were fitted with horn-balanced ailerons only on the upper wing. The others had ailerons on both wings.
After the HS-1s, by this time designated HS-1L to identify installation of the Liberty engine, had entered service, it had been found that the standard 180 lb depth-bomb was ineffective against submerged submarines. Since two of these were all that the HS-1L could carry, it was decided to increase the wing span so that heavier 230 lb bombs could be carried. The modification was quite simple, an additional 6-ft panel was fitted between the centre section and the regular outer wing panels, increasing the overall span from 62 to 74 ft. This modification, which resulted in a new designation of HS-2L, was made to the majority of aircraft still on order, and there is no distinction in serial numbers between HS-1Ls and the HS-2Ls.
HS-1s were the first American-built aircraft received by the US Naval forces in France, eight arriving by ship at the US Naval base at Pauillac on May 24, 1918. The first flight was made on June 13. Records indicate that 182 HS-1Ls and HS-2Ls were distributed among 10 of the 16 Naval Air Stations in France. Of the total, only 19 can be confirmed as HS-2Ls.
The HS-2L remained the standard single-engine patrol and training flying-boat in the post-war years, examples remaining in the inventory until 1926. An additional 24 HS-2Ls were obtained in the post-war years by assembling accumulated spare parts at various Naval Air Stations and assigning new serial numbers to the complete aircraft. The serials were assigned as follows:
A5564/5569 NAS Miami, Florida
A5615/5619 NAS Hampton Roads, Virginia
A5787 NAS Key West, Florida
A5808 NAS Anacostia, Maryland
A6506 NAS Coco Solo, Canal Zone
A6507/6513 Naval Aircraft Factory, Philadelphia, Pa.
A6553/6556 NAS San Diego, California
The HS-3 was an improved model with revised hull lines under development at war's end. Curtiss built five (A5459-A5462) and the Naval Aircraft Factory two (A5590-A5591). After the war, many surplus HS-2Ls were acquired by civil owners who used them for passenger carrying and even scheduled airline operations. A few were still in use as survey planes in Canada in the early 1930s.
TECHNICAL DATA (HS-2L)
Manufacturer: Curtiss Aeroplane and Motor Co, Inc, Garden City, LI, and Buffalo, NY; Standard Aircraft Corporation, Elizabeth, NJ; Lowe, Willard and Fowler, College Point, LI; Gallaudet Aircraft Corporation, East Greenwich, Conn; Boeing Airplane Company, Seattle, Wash; Loughead Aircraft Corporation, Santa Barbara, California.
Type: Patrol flying-boat.
Accommodation: Crew of two or three.
Power plant: One 350 hp Liberty 12.
Dimensions: Span, 74 ft 0 1/2 in; length, 39 ft; height, 14 ft 7 1/4 in; wing area, 803 sq ft.
Weights: Empty, 4,300 lb; gross, 6,432 lb.
Performance: Max speed, 82.5 mph at sea level; initial climb, 10min to 2,300ft; service ceiling, 5,200 ft; range, 517 st miles.
Armament: One flexible 0'30-in Lewis gun. Two 230lb bombs.
HS-1L/2L (Curtiss): A800-A815; A1549-A2207.
HS-2L (Standard): A1399-A1548 (50 cancelled).
HS-2L (LWF): A1099-A1398 (50 cancelled).
HS-2L (Gallaudet): A2217-A2276.
HS-2L (Loughead): A4228-A4229.
HS-2L (Boeing): A4231-A4255.
HS-2L (NAS): A5564-A5569; A5615-A5619; A5787; A5808; A6506-A6513; A6553-A6556.
HS-3 (Curtiss): A5459-A5462.
HS-3 (NAF): A5590-A5591.
P.Bowers Boeing Aircraft since 1916 (Putnam)
CURTISS HS-2L (No Boeing Model Number) - In keeping with the policy of having several manufacturers build certain aircraft which were needed in quantity during WW-I, the Navy requested Boeing to build 50 Curtiss HS-2L single-engine patrol flying-boats. Construction was entirely conventional for the period, and fitted in well with Boeing seaplane experience, since the hulls were built up of crossed strips of wood veneer over wooden formers in much the same manner as used on the Boeing-designed floats of the Model Cs. Construction was sufficiently under way at the time of the armistice to permit completion of the first 25 aeroplanes in spite of the large postwar contract cancellations. The Boeing-built HS-2Ls differed from those built by Curtiss, Standard, Lockheed, Gallaudet, and L.W.F. in not having ailerons on the lower wing. This model provided Boeing with the flying-boat experience that resulted in the B-l and BB-1 boats of 1919-20.
TECHNICAL DATA - HS-2L
Type: Patrol flying-boat
Accommodation: 2 pilots, 1 bombardier/gunner
Power plant: Low-compression Liberty, 360 hp
Span: 74 ft 1 in
Length: 39 ft
Height: 14 ft 7 in
Wing area: 803 sq ft
Empty weight: 4,359 lb
Gross weight: 6,432 lb
Max speed: 85 mph
Climb: 1,800 ft in 10 min
Range: 575 miles
Armament: One Lewis MG, two 230 lb bombs
Navy serial numbers: A-4231 /4254
Jane's All The World Aircraft 1919
CURTISS MODEL H.S. 1L and H.S. 2L FLYING BOATS
H.S 1L was a three-seat escort and anti-submarine flying boat of 1917, powered by a 375 h.p. Liberty engine. It was ordered into production and became the only American aircraft to fly with the US Navy in Europe during the war (from May 1918). Of 182 H.S. flying: boats received by the USN in Europe, almost all were of this version. Perhaps about 20 were of the later H.S.2L type, with greater wing span to allow carriage of larger bombs. This version is detailed below.
CURTISS MODEL H.S.2L. FLYING BOAT.
Wing span, upper plane 74 ft. 0 19/32 in.
Wing span lower plane .. 64 ft. 1 21/32 in.
Depth of wing chord 6 ft. 3 5/32 in.
Gap between wings (front) 7 ft. 7 1/8 in.
Gap between wings (rear) 7 ft. 5 29/32 in.
Length of machine overall 40 ft
Height of machine overall 14 ft. 7 3/4 in.
Angle of incidence, upper plane 5 1/2 degrees
Angle of incidence, lower plane 4 degrees
Dihedral angle 2 degrees
Sweepback 0 degrees
Wing curve R.A.F. No. 6
angle of incidence 0 degrees
Wings, upper 380.32 sq. ft.
Wings, lower 314.92 sq. ft.
Ailerons (upper 62.88, lower 42.48) 105.36 sq. ft.
Horizontal stabilizer 54.8 sq. ft.
Vertical stabilizer 19.6 sq. ft.
Elevators (each 22.8 sq. ft.) 45.6 sq. ft.
Rudder 26.5 sq. ft.
Total supporting surface 800.6 sq. ft.
Loading (weight carried per sq. ft.
of supporting surface) 7,77 lbs.
Loading (per r.h.p.) 18.85 lbs
Net weight, machine empty 4,359 lbs.
Gross weight, machine and load 6,223 lbs.
Useful load 1,864 lbs.
Fuel 977 lbs.
Crew 360 lbs.
Useful load 527 lbs.
Total 1,864 lbs.
Speed, max. (horizontal flight) 91 m.p.h.
Speed, min. (horizontal flight) 55 m.p.h.
Climbing speed 1,800 ft. in 10 mins.
Liberty 12-cylinder. Vee, four-stroke cycle. Water cooled.
Horse power (rated) 330.
Weight per rated h.p. 2,55 lbs.
Bore and stroke 5 in. x 7 in.
Fuel consumption 32 galls per hour.
Fuel tank capacity 152.8 galls.
Oil tank capacity 8 galls.
Fuel consumption per b.h.p. 0.57 lbs per hour.
Oil consumption per b.h.p. 0.03 lbs per hour.
Flight, August 30, 1917.
THE NEW CURTISS H-S-I FLYING BOAT.
ONE of the latest models turned out by the Curtiss Co. is seen in the accompany illustrations. The H-S-1 is a medium-sized boat, coming between the 90 h.p. and the 400 h.p. H-12 models. It is not designed for speed, but is a relatively slow sailing craft of great steadiness, which can be driven for hours without fatiguing the pilot, and is thus eminently suitable for coast patrol work, for which it has been primarily designed. It is powered with a single Curtiss V-2 200 h.p. and carries pilot, passenger and fuel for 6 hours' cruise.
The hull resembles that of the H-12, in that it is fitted with the planing fins at the sides, but the cockpit is not enclosed as on the H-12. Harold Kantner, the well-known American pilot, flew from Buffalo to Detroit and back with a passenger on this machine last July, and reported that the boat handled very well.
The follewing are the principal characteristics of the H-S-1: Span (top), 59 ft. 4 ins, (bottom) 45 ft. 8 ins.; chord, 6 ft. 3 1/16 ins.; gap, 7 ft. 6 ins.; no stagger and no dihedral angle; angle of incidence, 4° (wing section, R.A.F. 6); overall length, 38 ft. 6 ins.; height, 14 ft. 3 ins.; total supporting surface, 626 sq. ft.; loading, 6-7 lbs. per square foot; weight (empty), 3,215 lbs.; useful load, 1,000 lbs.; speed range, 52-73 m.p.h.; climbing speed, 500 ft. in 3 mins.
Flight, December 4, 1919.
THE U.S. NAVY HS-1L AND HS-2L FLYING-BOATS
A VERY successful type of flying-boat for coastal patrol work was put into quantity production by the United States Navy during the War, the Curtiss Aeroplane and Motor Corporation and the Standard Aero Corporation turning out most of the machines between them. There are two models of this flying-boat, the HS-1L and the HS-2L, but the only difference between them is that the latter model is 12 ft. greater in span than the 1L, and has a larger rudder. Apart from this and minor details, therefore, both models are identical, so that the following description and illustrations of the HS-2L apply equally to the other model. The additional wing surface of the HS-2L is obtained by inserting a 6-ft. panel between each outer extension and the centre section. All the other parts - except, of course, the rudder - required to convert the 1L to the 2L are duplicates of other parts already on the former model, and the following is a list of the parts and alterations required in converting the 1L to 2L:- (1) Four 6-ft. panels, complete with hinges, and standard HS-1L wing-post fittings. (2) Upper centre section panel, with unrouted spars. [These are routed in the 1L.] (3) Front centre section lift wires changed from two 3/16-in. to two 1/4-in. non-flexible cable, and rear lift wires from two 3/16-in. to two 7/32-in. non-flexible cable. (4) Two 7-ft. front interplane struts 2 5/8 by 6 5/8 ins., and two 7-ft. rear 2 3/16 by 5 1/2 ins. (5) Four 1/8-in. stagger wires, with turnbuckles and end connections. (6) Larger size rudder, having 26.5 sq. ft. area instead of 19.6 sq. ft. (7) Aileron control cables lengthened.
The main planes, which have neither stagger nor sweepback, have the R.A.F. No. 6 wing section, and comprise a centre or engine section, the lower panels of which being divided by the hull and attached to small "sidewalk" panels built integral with the hull; 24 ft. outer extensions, which in the case of the L1 are mounted direct to the centre section; and, in the L2, 6 ft. intermediate sections. The centre section surfaces are "straight," but the outer sections are set at a dihedral angle of 2°. Balanced ailerons are fitted to both upper and lower planes, the upper ailerons having a maximum chord of 2 ft. 2 ins., and span of 17 ft. 8 1/2 ins., whilst the lower ones have a maximum chord of 1 ft. 10 ins. and a span of 12 ft. 9 ins. The main spars are spaced 4 ft. apart, the front spar being located 9 ins. from the leading edge. The fabric is sewn to the wings with the seams laid diagonally or normal to the leading edge. It is doped with two coats of cellulose acetate, two to four coats of cellulose nitrate, two coats of anti-actinic grey wing enamel on the top and vertical surfaces, and one coat of the latter on the under surfaces. All the strut fittings are of steel stampings and forgings, the main spars are of spruce, and the trailing edges of flattened steel tubing. The compression ribs are of solid pine, and the intermediate ribs of lightened pine. The tail is of the non-lifting type, mounted high up on the stern above the fin. The elevators are divided and unbalanced, whilst the rudder is balanced.
The hull is similar in form and construction to the other flying boats of the H-12 and F-5L type. It has an overall length of 34 ft. 5 ins., a width of 4 ft. for the main body and 8 ft. across the planing fins. The planking is of pine or cedar, made up of 3/16 -in. outer layer and 5/32-in. inner layer, with fabric in between. The frames, keel and stern post are of ash, whilst the keelson, deck stringers and floors are of pine or cedar. The chine stringers are also of pine, or Port Orford cedar, and the seam strips are Spanish cedar. The bulkheads are of three-ply waterproof veneer. The hull itself is finished with low visibility grey wing enamel, and all metal parts are enamelled.
The power plant consists of a single twelve-cylindered, low-compression Navy type Liberty, developing 330 h.p. at 1,700 r.p.m., and driving a four-bladed pusher screw. The engine is carried on laminated ash-spruce-ash bearers mounted above the hull on streamlined steel tubing, braced with non-flexible tension cables. The main fuel tanks, having a capacity of from n o to 125 galls., are located in the hull at the centre of gravity, a gravity tank of about 30 galls, capacity being mounted on the top plane centre-section.
Dual control is fitted, consisting of an inverted U ash frame equipped with two 16-in. hand-control (aileron) wheels. The rudder-bars are of ash, mounted on bronze blocks. The throttle and ignition levers are located in the cockpit, on a diagonal bridge between the two seats.
All bracing cables are galvanised, non-flexible. The centre-section and intermediate cables in the 1L are 3/16- in., the outer cables being 5/32 in. All flying cables are doubled The following is a general specification of the HS-1L, and, in.brackets, HS-2L :-
Span, upper 62 ft. 0 ins. (74 ft 0 ins.)
Span, lower 52 ft. 1 5/8 in. (64 ft. 1 5/8 in.)
Chord 6 ft. 3 ins.
Gap 7 ft. 6 ins.
Overall length 38 ft. 6 ins.
Height 14 ft. 4 1/4 ins.
Angle of incidence, upper 5 1/2 #
Angle of incidence, lower 4#
Area, main planes
Upper 307 sq. ft. (380 sq. ft.)
Lower 241 sq. ft. (315 sq. ft.)
Ailerons 105 sq. ft.
Total surface 653 sq. ft. (800 sq. ft.)
Area of tail plane 54.8 sq. ft.
Area of elevators 45.6 sq. ft.
Area of fin 19.6 sq. ft.
Area of rudder 19.6 sq. ft. (26.5 sq. ft.)
Area of non-skid 16 sq. ft.
Weights, 1L -
Hull (including sockage) 1,265 lbs.
Wings, tail, bracing, etc.1,400 lbs.
Engine and equipment 1,336 lbs.
Ordnance equipment 560 lbs.
Electrical equipment 53 lbs.
Navigation equipment 32 lbs.
Crew and fuel 1,090 lbs.
Accessories 52 lbs.
Miscellaneous 112 lbs.
Total weight 5,900 lbs.
Total weight, HS-2L 6,223 lbs.
Useful load, HS-2L 1,864 lbs.
Loading per sq. ft. 9.03 (7.77)
Loading per h.p. 17.9 (18.85)
Maximum speed 91 m.p.h.
Minimum speed 53 m.p.h. (55 m.p.h.)
Climb, 500 f t / 3 mins. (1,800 ft./10 mins.)