Tandem rotor helicopters, a brief history

America's "Happy Hooker," the CH-47 Chinook
America's "Happy Hooker," the CH-47
Chinook
December 13, 2006
Go!
Tandem rotor helicopters, a brief history
Fundamentally, a tandem rotor helicopter is one with twin
main rotors, one in the front, one in the back, with no tail
rotor. The Helicopter Page by Glenn S. Boom has a nice
description with good graphics which we commend to you.
Table of Contents
Introduction
Tandem rotor helicopters, a
brief history
CH-47 walk-around
The Florine helicopter, circa 1929-30. Presented by J. Gordon Leishman,
University of Maryland
The H-21, a tandem rotor
goes to fight in Vietnam
Nicholas Florine, a Russian-born engineer, built one of the
first successful tandem rotor helicopters, in Belgium, in
1929-30. He improved on his design over time, but
experienced multiple problems and the idea became dormant
during WWII.
The Chinook gets its
initiation in the Vietnam
War
The US Coast Guard was an early advocate of the helicopter,
among the first organizations in the world to see the helicopter
as a useful machine. During WWII, it needed an aircraft for
at-sea rescues of crews from ships torpedoed by the Germans
along the US coast. The USCG envisioned the need to carry
very heavy loads, up to 1,800 lbs, and it felt the Navy had
nothing that could handle the job. As a result, the tandem rotor
helicopter found its first requirements, from the Coast Guard
(USCG) during WWII.
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Fast forward to Afghanistan,
at war, and Pakistan, a
humanitarian role
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America's "Happy Hooker," the CH-47 Chinook
The Coast Guard's Lieutenant Commander F.A. Erickson, fifth from the left
in the above photo, and his 1st Coast Guard Helicopter Detachment, were
pioneers in helicopter flying. Presented by helis.com.
Commander Frank Erickson and his men were leaders in the
field. We have some information on the Coast Guard's early
helicopter activities in an article entitled, “No compromise. No
rationalization. No Hesitation. Fly the mission. Now!"
Before proceeding further, we will warn you that helicopter
nomenclature in the early days can drive you nuts. That said,
let's move ahead.
An American engineer, Frank
Piasecki, who earlier had
designed a small helicopter,
turned his attention to larger
ones during and after WWII.
He and his colleagues at
PV-Engineering Forum
developed the world's first US
Navy helicopter, and the
world's first successful tandem
helicopter, the XHRP-1 "Dog
Ship" in 1944. The "XH" stood
for experimental helicopter; they wanted to use "T" for
transport, but it had been taken by trainers, so they came up
with "RP." The final "X" reflected that the Dog Ship was a
company prototype.
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America's "Happy Hooker," the CH-47 Chinook
XHRP-1 Dog Ship first flight, March 7, 1945. F.N. Piasecki, pilot; G.
Towson, copilot, sitting behind the pilot. This was a flying mock-up flown as
a control demonstrator, without its fabric cover. Presented by Piasecki
Aircraft Corp.
Piasecki described the tandem rotor concept this way:
"Two rotors permitted a low disk loading, yet allowed
the blade spars to be within available material length.
The tandem design provided a significant increase in
center of gravity travel, thus negating the need for
shifting ballast, as was necessary in single rotor
helicopters. Since a tail rotor was not needed to counter
the main rotor torque, more weight could be lifted with
a given engine. It carried 10 men and reached 95 miles
per hour without its fuselage covering. Critics predicted
that downwash from the front rotor in forward flight
would cause severe rear rotor turbulence, spoiling its
control capability. This never happened when the proper
differential collective pitch was added to the
longitudinal control. Eighteen-hundred pound external
loads (world’s first log lift) were lifted with two, then
one load line. An autorotative test was made with the
interconnecting shaft between the rotors disengaged, as
well as disengaging the engine."
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America's "Happy Hooker," the CH-47 Chinook
XHRP-X performs world's first log lift (1,800 lbs.) - 1946, F.N. Piasecki,
pilot; Lou Leavitt, co-pilot. Presented by Piasecki Aircraft Corp.
The XHRP-X Dogship officially became the HRP-1
"Rescuer," better known by observers as the "Flying Banana"
and the "Sagging Sausage." She had a fabric covered fuselage.
The company called it the PV-3. She could hold as many as
ten passengers, depending on how many crew and how much
fuel she carried. The Navy, acting as executive agent for the
Coast Guard and Marines, received deliveries from 1947
through 1949. At the time, this was the world's largest
helicopter.
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America's "Happy Hooker," the CH-47 Chinook
HRP-1 ladder demonstration at inauguration of Idelwild Airport, August
1948. Presented by Piasecki Corp.
The Coast Guard and Navy used this aircraft for rescue. The
Navy also would use it for anti-submarine warfare (ASW)
sonor "dipping."
HRP-1 (Piasecki) helicopter, taken at U.S. Coast Guard Air Station,
Elizabeth City, North Carolina, January 30, 1951. Presented by Waypoints: A
digital archive of US Coast Guard History.
Twelve of the aircraft bought by the Navy were assigned to the
Marines for landing exercises; three others were assigned to
the Coast Guard. The Coast Guard received its birds in 1948.
All three were stationed at Coast Guard Air Station Elizabeth
City in North Carolina. They did a lot of experimenting,
mostly crafted by Commander Erickson and his team,
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America's "Happy Hooker," the CH-47 Chinook
including on-the-water landings, use of new hoists, rescue
baskets, rescue harnesses, shipboard landings, and flood relief.
Lt. David Oliver, piloting, Lt. MacLane at the co-pilot and Lt.
Thometz, a doctor, ran the USCG's first recorded search and
rescue mission on December 31, 1948, carrying a 14 month
old baby girl with pneumonia from Cape Hatteras, North
Carolina to the hospital in Elizabeth. They flew aboard HRP
No. 13 for this mission. The young girl survived.
HUP "Retriever" for the fleet. Presented by Piasecki.
In 1945, the Navy went to another Piasecki tandem helicopter,
known as the XHJP-1 to Piasecki, HUP-1, 2, 3 and 4
"Retriever" to the Navy, and the H-25 "Mule" to the Army.
The Navy wanted her for spotting, rescue and utility missions
conducted from battleships and cruisers, while the Army
wanted her for light cargo and utility. The Retriever was a
six-to-eight-place machine for rescues. Both the Retriever and
the Mule could handle a useful load of about 1,650 lb once
fuel and crew were loaded up. The Navy received its first
Retriever in 1951 and flew them until 1964. The Army bought
63 but later turned them over to the Navy.
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America's "Happy Hooker," the CH-47 Chinook
HO3S helicopter aboard the USS Philippine Sea (CV-47), October 1950
during operations off Korea. Presented by Naval Historical Center.
Following WWII, the Marines did not have a helicopter they
could use to lift more than two troops. It was known as the
HO3S-1. In fact, the Marines were the last American military
service to receive helicopters. Nonetheless, they formed their
first helicopter squadron, an experimental helicopter squadron,
HMX-1, at Quantico, Virginia, in January 1948. The "H" was
for helicopter, "M" for Marine, and "X" for experimental.
Interestingly, the requirement for such a squadron grew out of
the use of A-bombs against Japan. The Marines worried that
traditional amphibious landings concentrated many troops and
equipment in a relatively small space, very vulnerable to these
weapons. The Marines wanted to be able to allow more diffuse
amphibious attacks, and saw the transport helicopter as a
means to effect that.
HMX-1 practiced with what they had, simulating landing a
regimental combat team and its equipment ashore using the
HO3S-1, its crew and two ground combat Marines on each run
from the USS Palau (CVE-122).
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America's "Happy Hooker," the CH-47 Chinook
HMX-1 Piasecki HRP-1 at Quantico, 1949. One Marine pilot commented,
"About all I could say about this bird was that it was underpowered,
shuddered, and was wrapped in fabric." Presented by popasmoke.
By late 1948, though, the Marines received their first HRP-1s,
which could carry 8-10 troopers. Thus started Marine Corps
helicopter amphibious assault.
Marine HRS-1 "Chickasaw" helicopters launching from the USS Sicily off
Korea, 1952. Presented by the Naval Historical Center.
That said, the Marines did not take the HRP-1 to the Korean
war, instead using the little HO3S-1, followed by the HRS-1
"Chickasaw" manufactured by rival Sikorsky, a competitor of
the HRP-1. The Marines used the HRP-1 mainly to do tests
and evaluations, especially in the tactics development arena.
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America's "Happy Hooker," the CH-47 Chinook
The Marines wanted a transport helicopter that could carry
heavy payloads. By 1949 the Marines were talking about a
3,000 lb payload transport chopper. But they were reluctant to
go to the tandem rotor.
So for the Marines, in the Korean War, the Sikorsky HRS-1
Chickasaw was the preferred helicopter. You can see the
Chickasaw was a single rotor with tail rotor design. She was
used for multiple missions in the Korean War, including troop
lift, rescue and transport of heavy equipment and supplies, and
air assault. All the other services also bought this aircraft.
Over 1,000 were made for the US military. The Marines
conducted their first helicopter-landing of a combat unit in
history on September 21, 1951 using Chickasaws, enabling
troops to capture hill 884 in Korea.
Piasecki PV-17-HRP-2, 1949. Presented by All the World's Rotorcraft.
The HRP-2 was the next tandem rotor helicopter to pop out
from Piasecki. In June 1948, the Navy ordered five
"examples" of the PV-17 and designated it the HRP-2. She had
a metal fuselage instead of fabric, better visibility, and the
pilots sat next to each other instead of one behind the other.
The HRP-2 was a major improvement over the HRP-1, but she
was too light and could not carry the loads now being
envisioned by the services. Only five were built.
Next out of the Piasecki chute was the YH-21.
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America's "Happy Hooker," the CH-47 Chinook
USAF CH-21B "Workhorse" at the National Museum of the USAF.
Presented by the National Museum of the USAF.
The USAF ordered 18 YH-21s from Piasecki Helicopter Corp.
in 1949 for evaluation and service trials. They then ordered 32
H-21As for the Military Air Transport Service's (MATS) Air
Rescue Service (ARS) followed by orders for the B-model to
serve as an assault transport for the Troop Carrier Command
(TCC). All together, the USAF bought 214 H-21s. Deliveries
began in 1953 and the first off the line went into Arctic
service.
The H-21 operated well in frigid weather. It quickly began
servicing US and Canadian forces working in the northern
regions of Alaska, Canada and Greenland in support of the
Distant Early Warning (DEW) Line installations. The USAF
version was called the "Workhorse."
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America's "Happy Hooker," the CH-47 Chinook
Arctic view of US-USSR dispositions during the Cold War. Presented by
Cold War Stories, Related Tales & Commentaries.
It should be recalled that back in
these days, the USAF was going
to fly its nuclear capable B-52
strategic bombers over the Arctic
Circle and, USAF fighter aircraft
stationed in Alaska, Canada and
Iceland were tasked to meet and
destroy as many incoming Soviet
bombers as they could handle. Furthermore, transatlantic
flights on the northern route over and near Greenland were
growing in number, both military and civilian. So Arctic
rescue was important to the USAF.
The USAF needed a helicopter with "long legs;" i.e., long
range. The H-21 could be mounted with wheels, skids or
floats. A new word was hatched to describe this capability:
"omniphibious."
The Marines did not buy into the CH-21, even though the
aircraft interested them. As we mentioned earlier, they went to
Korea with the HRS-1 "Chickasaw." The Marines stuck with
Sikorsky, buying into its HUS (Helicopter Utility Sikorsky)
series of helicopters, all of which were single rotor with tail
rotor designs. The Marines' first heavy lift helicopter was the
HR2S-1, which the Army also bought, naming it the CH-37
"Mojave."
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America's "Happy Hooker," the CH-47 Chinook
CH-37 Mojave attempting to lift a crashed CH-21 Shawnee. Presented by
wikipedia
Tandem rotor buffs won't like this photo too much, a CH-37
attempting to lift a crashed CH-21. We don't know if the
Mojave got this job done, but the CH-37 was a heavy lifter.
The Marines would go on to outfit their transport squadrons
with 309 HUS variants, all single rotor. It would be interesting
to study why the Marines stayed clear of the tandem rotor.
Piasecki CH-21 "Shawnee" for the Army. Presented by All the World's
Rotorcraft.
The Army, however, not only bought the CH-21, but used
them from 1949 to 1964. The Army bought 334 "C-Models",
and, in the tradition of using American Indian names for its
helicopters, named it the "Shawnee." The Army employed the
Shawnee in its first combat tests in Korea, but the Shawnee
emerged as a hard-worker during the Vietnam War. She was
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America's "Happy Hooker," the CH-47 Chinook
the first American military helicopter to deploy to Vietnam in
significant numbers. The first four Shawnee units arrived in
South Vietnam between December 1961 and September 1962
and remained the backbone of Army aviation in Vietnam until
1964, replaced by the UH-1 "Iroquois," better known as the
"Huey." Most Shawnees were withdrawn from active service
by 1965.
In the mid-1950s, Franck Piasecki left his company, we
understand, bitterly, and began a new one, using his name. So
the company he left renamed itself "Vertol" (Vertical Take-Off
& Landing). Boeing bought Vertol in 1960. It was first named
Boeing Vertol, then Boeing Helicopters. This company would
build two of the more famous helicopters made in the US,
both tandem rotors, the CH-46 Sea Knight and the CH-47
Chinook. We are going to concentrate on the Chinook, but
here they are, "side-by-each."
Navy Boeing-Vertol UH-46D. Photo credit: Photographer's Mate Airman
Byron Gilbert. Presented by Vectorsite.
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America's "Happy Hooker," the CH-47 Chinook
Army CH-47A "Chinook," on display at Camp San Luis Obispo. Presented
by the California Military Museum.
Vertol began studying "how to" develop a new medium-lift
helicopter using the HUP-1 "Retriever" and H-21
"Workhorse-Mule" configurations and based on the H-21's
rotor system. A prototype, called by the company the V-107,
began in 1957 and she took her first flight in 1958.
The Army ordered 10 production aircraft in mid-1958 and
designated it the YHC-1A. The Army also asked for a larger
aircraft, similarly designed, and the company designated it the
V-114. The Army ordered five prototypes, and designated it
the YHC-1B. For the company, the result was it was building
two different developmental aircraft at the same time. It could
not handle the myriad challenges of doing that, which forced it
to sell out to Boeing.
The Army stepped away from the small YHC-1A and opted
for the larger YHC-1B. But the Marines liked the YHC-1A
and designated it the HRB-1. At long last, the Department of
Defense (DoD) stepped in to end the nomenclature madness,
and introduced a new "tri-service" uniform designation
system. The HRB-1, or YHC-1A, became the CH-46A Sea
Knight, while the YHC-1B became the CH-47A Chinook.
We're not going to talk much about the Sea Knight. There are
some design differences. The big one is that the Chinook is
bigger, she has fuel tanks running the length of the fuselage,
and four fixed landing gears.
The CH-47A could carry 33 fully-equipped troopers or 6,000
lbs of internal cargo. She could lift 13,000 lbs externally.
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America's "Happy Hooker," the CH-47 Chinook
Here's an impressive lineup, presented by rotors.org.
Left to right, top to bottom, CH-47 Chinook, CH-46 Sea
Knight, CH-21 Shawnee, and the HUP-1 Retriever - CH-25
Mule.
CH-47 aircraft walkaround
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