SPECIFICATIONS
Unless otherwise noted, these specs we taken from "RCN Aircraft General
Information Data" , dated May 1, 1963.
Main rotor diameter: 53 ' 0"
Max. Height (To top of tail rotor blade) : 15' 4"
Width (Blades folded): 11' 6"
Tail rotor diameter: 8' 5"
Max. weight: 7,750 pounds (6,800 lbs typical)
Service ceiling: 9,400 ft.
Maximum Speed: 115 knots (132 m.p.h). at sea level.
Cruising Speed: 75 knots at sea level
Maximum Climb: 910 ft./min. at sea level.
Endurance: About 4.5 hours or a range of 265 nautical miles.
Engine: Curtiss-Wright R1300-3 (7 cylinder radial engine) restricted
to 700 BHP at 39.5 in. of mercury.
Fuel: Uses 3-GP-25C 91/96 grade avgas stored in one forward tank of
86.6 Imp gal. and one aft tank holding 70.8 Imp gal. Both were crash resistant
tanks situated beneath the cabin in the lower part of the fuselage.
Engine Oil: Uses 3-GP-320 100 grade oil; one tank of 7.8 Imp gal. capacity
Armament: Equipped with a Mk 43 torpedo launching installation on the
port side exterior.
First taken on strength by the RCN: 5 December 1952.
Struck off strength: 16 May 1970.
VARIANTS
Lt Robert Murray provides information on the HO4S-3 variants and their
two roles:
"The RCN acquired thirteen HO4Sx helicopters in total. They
were all built at the Sikorsky plant in Bridgeport, Connecticut and were
purchased through Canadian Pratt & Whitney Aircraft Company of Longueuil,
P.Q. The first RCN variant was the HO4S-2 of which three were acquired
and allocated to No. 1 Naval Helicopter Flight, later to be known as Helicopter
Utility Squadron Twenty-One (HU-21). These helicopters were used primarily
as a plane guard during flight operations from the aircraft carriers.
The remaining ten were HO4S-3 models. Of the thirteen aircraft acquired
five were destroyed due to accidents with no loss of life to the aircrew.
The three initial HO4S-2 models noted above were fitted with an
engine of 600 horsepower derated to 550. One of these, serial number 51444,
was lost in an accident so the two remaining HO4S-2 were retrofitted with
the larger 800 horsepower engines derated to 700. This, together with other
technical improvements, brought them up to the HO4S-3 standard. Derated
engines improved reliability and the reduced engine overhaul interval of
500 hours provided an additional margin of safety. This upgrade work was
performed by Pratt & Whitney Canada Inc. at Longueuil, Quebec. Of the
ten additional HO4S-3 helicopters purchased from Sikorsky in 1955, six
were for the newly formed Helicopter Anti-Submarine Squadron Fifty (HS-50).
All RCN HO4S-3 helicopters were equipped with a Wright R-1300-3, seven
cylinder nose mounted radial engine. The R-1300-3 drove a fully articulated
three bladed, 53-foot diameter, main rotor through an angled drive shaft
and reduction gearing and, a torque compensating, two bladed, tail rotor.
The main rotor turned at about 220 RPM or roughly one-tenth the engine
speed and is constant throughout the zero to 115-knot (132-mph) speed range
of the helicopter. The normal cruising speed was 75 knots (82 mph) with
a range of 265 nautical miles (305 statute miles).
The RCN HO4S-3 was employed in two roles - SAR (Search and Rescue) and
anti-submarine warfare with each role being performed by a different Squadron.
Helicopter Utility Squadron HU-21 was the first squadron commissioned,
primarily for rescue duties both at sea, on Canadian aircraft carriers,
and ashore. The second, Helicopter Anti-Submarine Squadron HS-50 equipped
the helicopters with an AN/AQS-4 dunking sonar which was used for the underwater
detection of submerged submarines.
SEARCH and RESCUE ROLE
In the SAR/Utility configuration used by squadron HU21, the HO4S-3 was
equipped for two pilot operation, but only one pilot plus one crewman/hoist
operator were normally carried on Search and Rescue (SAR) missions. Depending
on fuel load, provision could be made in the main cabin for six seats or
five stretchers. The primary item of airborne rescue equipment was a Breeze
Company hoist with a 600 pound lift capacity. If, for any reason, the rescue
crewman was required to assist a victim on the ground or in the water,
the pilot in the right hand seat could operate the hoist from the cockpit.
An electrically operated guillotine was available to the pilot or crewman
to sever the hoist cable should it become fouled. The helicopter could
also be fitted with an external sling which permitted the carrying of up
to 2000 lbs. of external cargo. When the helicopter was engaged in over
water "wet hoists", a large section of rubber matting was fitted over the
cabin floor. This prevented salt water from seeping into the cabin floor
and corroding the aircraft structure.
The call sign for the "duty" rescue helicopter based at Shearwater was
"ANGEL" and, when embarked from the carrier as HU-21 Detachment 1, its
call sign was "PEDRO" (The Flying Burro).
ANTI-SUBMARINE ROLE
"As noted earlier, a second Squadron of Sikorsky helicopters was formed
at HMCS
Shearwater on 4 July 1955, equipped with six HO4S-3 helicopters configured
to support ASW operations. The Squadron consisted of 18 pilots and ten
sonar operators. For any ASW sortie, the crew consisted of two pilots and
one sonar operator. Similarity with the operation of the helicopter's ASW
equipment with that carried in surface ships prompted the decision to employ
sonar operators in the helicopters. For tactical and safety purposes the
helicopters operated in pairs.
The HO4S-3 was fitted with an AQS-4 dunking sonar that could be lowered
up to 100 feet into the ocean. Active "sonar ranging" allowed the helicopter
to detect underwater targets and to direct fixed wing aircraft for attacks.
In the absence of fixed wing support, the HO4S-3 was capable of carrying
a Mk. 43 homing torpedo or a depth charge which could be launched from
the single rack on the port side of the helicopter. A primary role of HS-50
Squadron was to develop tactics for the use of helicopters in anti-submarine
warfare. A secondary role was the development of mine-clearing procedures".
Of the three man crew, the sonar man had the difficult task of picking
up echoes and classifying them since many objects beneath the surface of
the sea produce echoes besides submarines. Because the airborne sonar man
is much more on his own than his shipborne counterpart, only the highest
calibre operators were selected for this job.
The single biggest stumbling block against ASW operations was inclement
weather. Night, fog and heavy seas presented major problems. All weather
helicopters were yet to arrive on the scene. In particular, the lack of
an artificial horizon when hovering made it impractical to hover in anything
less than VFR conditions. A solution to the problem came later in the form
of a hovering autopilot.
INTRODUCTION OF HELICOPTERS TO THE DESTROYER ESCORTS
Leo Pettipas presents background information on the introduction of
helicopters to the RCN.
"The US Navy was experimenting with sonar-equipped helicopters
as far back as 1946, but it was not until the advent of the Sikorsky HO4S
in 1950 that a rotary-winged machine large and powerful enough to accommodate
sonar equipment became available.
The helicopter introduced a whole new dimension to ASW and can be regarded
as a truly revolutionary innovation. It gave the “small-ship” destroyer
escort (DE), with its limited rate of speed, a whole new lease on life,
as without the helicopter the DEs were severely handicapped in the age
of nuclear submarines. Its AN/AQS-4C sonar set, featuring a
submersible dome that was lowered by cable into the sea, was a variation
on the sonar equipment carried by surface vessels. A burst
of sound was transmitted from the dome, and any return echo was conveyed
back through the dome and the cable to the operator in the aircraft hovering
15 or 20 feet above the surface of the water. The operator could
determine the bearing and range of the object producing the echo. The versatile
helicopter had a distinct advantage over the surface vessel, which had
to be constantly moving through the water while carrying out its search
or attack; the noise of the water sweeping across the ship’s sonar dome
at high speed had the effect of drowning out the received echo. At speeds
of over 15 knots, the water rushing by the sonar dome would mask any returning
echoes. The problem could be addressed by reducing the ship’s speed, but
this was really not an option when the target was a fast Russian submarine.
Another advantage the helicopter had over the surface vessel was its
invulnerability from attack by a torpedo-armed submarine: unlike a surface
vessel whose hull shape and engine noise could be picked up by the submarine's
own sensors, the submarine could never be able to determine the source
of a helicopter's sonar bearing on itself. Because it had no bodily
contact with the water, the helicopter's movements could not be easily
predicted by the submarine. Finally, the helicopter's sensor was
recoverable, unlike the sonobuoys deployed by fixed-wing aircraft. Constraints
included a fairly high fatigue rate among crew members, inability to operate
at night and in adverse weather, and comparatively limited range. The conventional
fixed-wing aircraft remained essential to the ASW task of reaching out
beyond the range of the helicopter.
In the convoy protection role, the helicopter extended the search perimeter
of the surface escorts and provided close-in flanking, forward and rear
screens. Helicopter patrols generally lasted three to three and a
half hours, conducted during the daylight hours. Originally unarmed,
the helicopter was limited to discovering and pinpointing the threat; it
was still necessary to summon a destroyer or fixed-wing aircraft and home
it onto the target for the attack. The helicopters typically worked
in teams, leapfrogging one another to remain in close contact with the
submarine. To enable the destroyers to visually identify the particular
helicopter having the fix on the target, the sides and nose of the aircraft
bore large fluorescent red numbers.
HS 50 went on its first operational cruise aboard HMCS Magnificent in
February of 1956, and participated in the NATO New Broom V and VI trade
protection exercises held that year. In 1958, each of the HO4S-3s
was fitted with a torpedo-launching installation on the port side of the
fuselage, making them killers as well as hunters. Throughout the
late 1950s and on into 1960, all helicopter ASW operations were conducted
from the carriers. At the same time, something new was in the offing.
A distinctly Canadian contribution to rotary-winged ASW was manifested
in its exploratory work in operating large helicopters from small ships.
In October of 1956 the frigate HMCS Buckingham, with a temporary landing
pad fitted over her quarterdeck, commenced three months of trials in operating
a helicopter from the platform. In so doing, the RCN pioneered the
deployment of large rotary-winged aircraft from escort vessels.
 |
| A prefabricated helicopter platform has been fitted above the quarterdeck
of the frigate HMCS Buckingham to test the feasibility of operating helicopters
from anti-submarine escort vessels of this size. (DND photo DNS-16734) |
These experiments culminated in the first landing of helicopter
aboard a DDE, HMCS Ottawa, in October of the following year. The
aircraft involved was an H-34 helicopter provided for the purpose by the
RCAF. The trials successfully completed, it remained to fit the destroyers
with decks and hangars. Work was commenced in the late ‘50s
toward design and development of a rapid securing/quick release/traversing
system that would allow the landing and deck-handling of the aircraft.
This was eventually known as the "Bear trap". The first vessel
so configured went operational in the early 1960s. The helicopter had the
effect of increasing the destroyer escorts’ radius of search, detection
and attack. Of particular benefit would be the ability it would give a
ship to deliver a longer-range strike on a target lying beyond the reach
of shipborne weapons.
 |
| A HO4S-3 is standing by on the flight deck of HMCS Magnificent.
Prior to the introduction of helicopters, other ships performed the
duty of plane guard, ready to recover aircraft which ditched into the sea
during takeoff or landing. (Canadian Forces photo) |
END OF LIFE
The era of the HO4S-3 in HS-50 ended in 1963 when the squadron was re-equipped
with the larger and more capable Sikorsky CHSS-2 Sea King helicopter. The
HO4S-3 was stricken off strength from Canadian service in 1970.
