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Use Of And Future Of The CH-46 Assault
Helicopter In The United States Marine Corps
AUTHOR Major Kenneth D. Bonner, USMC
CSC 1990
I.  Purpose:  To show the history of the CH-46 assault support
helicopter and highlight problems concerning the service life
of the airframe and dynamic components.  The replacement
aircraft and issues surrounding it were examined.
II.  Problem:  The CH-46 is rapidly approaching the service
life of the airframe and its dynamic components without a
solution to replacing our current medium lift helicopter.
III.  Data:  The CH-46 has served the USMC well for over 26
years.  The airframe and dynamic components service lift has
been established as 10,000 hours by the Navy.  One airframe
has already reached the limit and the Navy has made a
recommendation on revising maintenance practices to extend the
service life to 13,000 hours until we can build some more
CH-46s and do a service life extension program on the
remaining ones to make them last until 2020.  The other
alternative recommendations to date have been looked at and
rejected because they cost too much or required more research
and development which costs more money and time than the USMC
has to make a decision on the medium lift replacement
aircraft.  A cursory look was made into the Osprey which seems
the way to go in the future.  The salvation for the Osprey as
an option is in the hands of the American people and Congress.
IV.  Conclusions:  A requirement urgently exists to solve the
CH-46 medium lift replacement problem and the most cost
efficient, least time consuming plan is to remanufacture the
CH-46 and SLEP the rest of them.  This will set the USMC back
regarding the over the horizon attack capability, but fiscal
constraints are the culprits.
V.  Recommendations:  Submit the remanufacture and SLEP option
to DOD as the most efficient and least expensive option.  This
keeps money in the POM budget, and if Congress restores
funding for the Osprey, it can be reprogrammed.  If Congress
does not restore funding for the Osprey, we have a realistic,
cost effective solution in place.
THESIS STATEMENT.  The United States Marine Corps has a dilemma
in deciding what to do about the medium lift replacement for
the CH-46 as they approach the end of their designed service
life in view of the Department of Defense decision to cancel
the MV-22.
I.   History of the CH-46E
     A.  First Flight
     B.  Foreign Military Purchases
     C.  Commercial Application
II.  Mission
     A.  Troop Transport
     B.  Transport of Supplies and Equipment
     C.  MEDEVAC
III. Aging Airframe and Dynamic Components
     A.  CH-46 Airframe
     B.  CH-46 Dynamic Components
     C.  SR&M Improvements
IV.  Implications of Cancelling the Osprey
     A.  Service Life Extension Program
     B.  Remanufacture the CH-46
     C.  Replacement Aircraft
     D.  Pentagon Plan for Medium Lift Replacement
V.   Attempts to Save the Osprey
     A.  CMC Appears Before Congress
     B.  Congressional Support
     C.  Foreign Interest
VI.  Conclusion
     The first flight of the CH-46 prototype was made on April
22, 1958.  The CH-46 made its first official flight in October
1961, a year from the contract signing.  The first deliveries
to squadrons was scheduled in early 1964 to Marine Aircraft
Group 26.  Designated the HRB-1 by the U. S. Marine Corps
before the Defense Department revised military aircraft
designations.  It was procured through the Navy Bureau of
Weapons and is the first helicopter BuWeps has bought from
inception on a fixed-price contract.  The CH-46 was the first
helicopter to come under the Weapons Readiness Analysis
Program (WRAP) as part of the new Navy maintenance package
system.  Basically, the WRAP system calls for providing
various card-file maintenance instruction packages by the
contractor designed for various unit levels.  Each package is
to contain step-by-step maintenance instructions for the
particular command level involved and also will specify the
manpower skills required in detail to carry out the
instructions in the package.
     The CH-46 helicopter was bought by foreign military
services also.  Boeing Vertol delivered three ships to its
licensee, Kawasaki Aircraft, and the major components for
seven more.  The Royal Canadian Air Force ordered six
helicopters with oversize sponsons fuel tanks providing 900
more gallons of fuel.  The specific operational requirement by
the Canadian Air Force was for 190 helicopters.  The Swedish
forces initially ordered nine helicopters to be used as
anti-submarine warfare aircraft.  All of these foreign
governments still operate the CH-46 helicopter today.
Kawasaki Heavy Industries, Ltd. still is manufacturing its
version of the aircraft, the KV-107, under license from Boeing
Vertol.  The last KV-107 was scheduled for delivery to the
Japanese Self Defense Forces in February 1990.
     In the early 1960's, the CH-46 was also used by
commercial operators and some CH-46s are still in use today
under the designation as a BV-107.  New York Airways used the
helicopter as a twenty-five passenger transport for the routes
around the New York area.  Columbia Helicopters in Washington
state has used the civilian version (BV-107) all over the
United States in externally lifting logs from inaccessible
sites for many years.  They have also used it in Norway to
externally lift tall power line transmission towers in remote
uninhabited terrain.
     The CH-46 is designed to provide helicopter transport of
supplies, equipment, and personnel for the landing force
during the ship-to-shore movement and within the objective
area.  Extreme mobility, gained by using helicopters
extensively in tactical operations, is an important part of
Marine Corps doctrine today.  It allows Marines to operate in
areas well removed from their rear bases for extended periods
of time.  Using helicopters to insert and extract long-range
reconnaissance teams provides a highly effective intelligence
capability.  The helicopter gives a commander an additional
means for locating the enemy, and its speed and mobility
provide the freedom to fix the enemy, mass sufficient combat
power, and destroy the enemy over distances previously
impossible to cross so rapidly.
     In helicopterborne operations, movement of troops,
supplies and equipment is accomplished by helicopters.  The
increase in mobility and freedom of action provides a ground
commander with combat options never available to him in the
past.  The helicopter's flexibility and versatility permit a
ground commander to reduce time and space limitations normally
encountered in the movement of assault forces.  Because an
assault force embarked in helicopters can cross terrain
obstacles, bypass hostile areas, and attack and destroy or
seize objectives deep in hostile areas, a commander is able to
concentrate the necessary combat power at the decisive time
and place and, once the desired result is attained, rapidly
redeploy his forces where necessary.
     Marine Corps CH-46 squadrons transport personnel and
cargo, provide utility combat support, and provide other air
support as directed for the landing force during the
ship-to-shore movement and within the objective area during
subsequent operations ashore.  These operations are part of
the assault support function of a Marine Aircraft Wing.
Marine CH-46s are employed for both tactical and
administrative/logistic missions.  Tactical missions consist
of helicopterborne assaults to seize critical terrain, isolate
pockets of enemy resistance, or conduct raids.
Administrative/logistic missions include supply or resupply of
troops, movement of equipment, nontactical movement of troops,
messenger and liaison service, and casualty and prisoner-
of-war evacuation.  The use as a medevac helo is especially
important in a cold environment because the CH-46 has a heater
and can carry 15 litter patients and two attendants.
     The CH-46 was procured from 1963 through 1971 with the
intent to fill a twenty-four year requirement for medium lift
in support of the United States Marine Corps.  The planned
life has since been converted to flight hours for
airworthiness certification purposes, more specifically, for
the purpose of determining what fatigue life the aircraft and
critical systems must meet.  In 1978, the Navy established the
service lift of the CH-46 as 10,000 hours.
     The CH-46 airframe service lift of 10,000 hours was
established as a qualitative indication of life for planning
only and is not a limit based on a fatigue test.  Therefore,
fatigue testing was not accomplished nor was any planned to
substantiate structural certification past 10,000 flight
hours.  Evaluation of the CH-46 airframe fatigue analysis,
fatigue test results and in-service experience data indicates
the CH-46 airframe can be safety operated beyond 10,000
hours.  This will be possible with a certain amount of testing
and analysis, as well as additional maintenance inspection
requirements, primarily during depot maintenance.  Some
civilian operators have logged over 25,000 hours on the BV-107
in commercial operations as reported in Rotor and Wind
Magazine.  However, these commercial operators are not
operating the airframe in the corrosive environment aboard
ships either.
     There are numerous dynamic components (rotor system,
drive system and flight controls) which have a life limit
equal to or less than 10,000 hours.  These components will
require replacement, fatigue tests, or modifications to
provide a longer life.  This problem has arisen once again
because the CH-46 was planned to last 10,000 hours so there
was no requirement to track components or items which exceeded
the 10,000 hour limit.
     We need to reexamine current fatigue data using current
mission profiles.  Some components can be extended based on
current testing.   The CH-46 and its dynamic components require
a service life assessment program (SLAP) to extend the
airframe and its dynamic components to 13,000 hours.  It will
be more cost efficient to redesign some components and make
some of them out of composites so they will last longer and
reduce the weight.  The Naval Aviation Depot at Cherry Point
has previously reported that it will cost $500,000 and eight
months to complete the service life assessment program on the
     The CH-46 fleet is rapidly approaching the 10,000 hour
planned service life.  One airframe in the Navy has already
reached the 10,000 hour mark according to officials at
NAVAIR.  The Marine Corps planned to have the CH-46 out of the
inventory by 1999.  This phase out is obviously not going to
happen at that time, as we have no approved replacement
identified at the current time.
     Some interim measures to keep the CH-46 operational past
the 10,000 hour mark have been planned by the Naval Aviation
Depot at Cherry Point in conjunction with officials at
NAVAIR.  Until other modifications resulting from a SLAP on
the CH-46 can be identified, some modifications to our
maintenance program have been identified.
     When the aircraft reach their designed service life of
10,000 hours, they will be sent to depots to induct the
aircraft into a modified standard depot level inspection
(SDLM) program.  This will extend the aircraft past its
designed service life of 10,000 hours.  The inspection will
follow basic SDLM guidelines with emphasis placed on increased
evaluation of areas that have been historically prone to
corrosion and wear along with areas previously identified as
having fatigue crack potential.
     An aircraft successfully completing the modified
inspection would be permitted to continue in service for
another service period.  A service period is defined as having
to return to depot every 24 months of service.  When the new
period end date (PED) is reached, the cycle will be repeated.
It is imperative that aircraft being certified beyond the
current service life be reinspected at the depot.  For this
reason, the aircraft service period adjustment (ASPA)
inspections will be eliminated for these aircraft.  An ASPA
is where a team from depot comes to the squadron and conducts
a limited inspection of certain areas.  If the material
condition of the aircraft warrants, an adjustment to the
induction cycle at the aircraft's PED for depot level
maintenance is made.  It should be noted that the H-2 and H-3
communities have utilized the SDLM inspection concept to
extend their aircraft beyond the 10,000 hour mark set by
NAVAIR for all helicopters in the Navy's fleet.
     The CH-46 has already gone through a safety, reliabil-
ity, and maintenance program (SR&M).  The purpose of this was
to reduce the costs of ownership, keep aircraft readiness at
a sufficient level so operational capability would not be
seriously degraded and to enhance the safety of the air-
craft.  The aviation planners looked at the 3m data of the
160 items composing unscheduled maintenance.  The top fifty
accounted for 92% of the problem.  Thirty two items become
the SR&M program as some of the top 50 were already the
subject of an engineering change proposal (ECP) or were in
research and development to correct the problems.  The first
SR&M aircraft improved CH-46 was finished by the depot at
Cherry Point in November 1983.
     The recent cancellation of the Osprey by the Secretary
of Defense has the Marine Corps scrambling to solve the
medium lift replacement for the CH-46.  We basically put our
eggs in one basket concerning the Osprey and have to react as
best we can in the aftermath of this decision.  One proposal
is to enter into a service life extension program (SLEP) to
extend the service life of existing CH-46s through the year
2020 by optimizing safety, cost effectiveness and operational
suitability for the UH mission in addition to application to
the CH-46 mission until phase out.
     Current estimates by NAVAIR indicate we will have to SLEP
some airframes and procure additional aircraft to make up for
attrition of the CH-46 fleet.  The Osprey was due to be
introduced into the fleet in 1992 as well as increasing
numbers of CH-46 aircraft would go out of USMC inventory.  The
weapons system manager for the CH-46 believes it would take
seven years before the first SLEP hardware implementation kits
could be available.  Also 10% of the CH-46 fleet will have
reached or exceeded the 10,000 hour service life.
     The Marine Corps is analyzing a four phase life extension
and upgrade for its fleet of CH-46 assault support helicopters
as an alternative to the Pentagon's plan to replace the
aircraft with a derivative of the UH-60 Black Hawk and buying
more CH-53Es.  In addition to a renewed CH-46 program, we are
considering the Westland/Agusta EH 101, Boeing's Model 360
technology demonstration helicopter.
     These alternatives, plus the V-22 itself, are under study
in an independent cost and operational effectiveness analysis
being prepared for Congress and the Pentagon.  Secretary of
Defense Cheney has indicated in the Washington Post that the
Osprey is killed regardless of what the study recommendations
indicate.  We have to consider the aircraft options as we help
prepare Navy aviation acquisition budget plans for fiscal year
1992-1997 that is to be submitted to the Pentagon in April.
     A CH-46 program would cost less than a UH-60 derivative
and the Black Hawk is too small.  The CH-46 carries a Marine
squad of 16-18 Marines, while the UH-60 is sized to an Army
squad of eleven soldiers.  A stretched version of the UH-60 to
accommodate the larger squad would lead to substantial
development costs and take too long.
     The 1950's technology CH-46 has been out of production
since 1971.  The SR&M upgrade did not extend the aircraft's
service life, and CH-46s will start reaching their 10,000 hour
service life in increasing numbers in 1993.  Time is short and
the 19 February 1990 issue of Aviation Week Magazine reports
the Marines have a plan revolving around the CH-46.  In
distinct phases, some-of them occurring simultaneously, the
CH-46 plan entails:
	 A service life extension program for most of
	 the current fleet.  The emphasis would be on
	 dynamic components, including the rotor system,
	 transmission and hydraulics.
	 New production of CH-46's as quickly as possible.
	 These helicopters would be manufactured with
	 improvements already made in fleet aircraft, but
	 otherwise would have the configuration in which
	 the CH-46 was last produced.  This phase would be
	 held below 100 aircraft, providing for no more than
	 attrition of the fleet.
	 Development and production of a CH-46E derivative,
	 being called the CH-46X.  The upgrade would
	 include modern equipment developed for other
programs, including integrated controls and the
	 V-22 derived glass cockpit incorporated in the
	 Boeing MH-47E and Sikorsky MH-60K special
	 operations forces helicopter.
	 Upgrade of all E models in the field into the
	 X configuration.  A thorough remanufacturing
	 program would start the new X models off with
	 new lifetimes lasting well into the 2020's.
     In the end, we would have a fleet of X's about the same
size as its current fleet of E's--about 350 aircraft.  This
plan assumes that current Marine Corps force levels will
survive Pentagon budget cutting.  Aircraft numbers would be
reduced if force levels were reduced.  We would seek a
reallocation of fiscal year 1991 budgets to accelerate a
reopening of the CH-46E production line at Boeing.  Table 1
shows how the CH-46E new production would be configured.
Table 2 shows the CH-46X new production configuration.  The
CH-46X would have to be capable of carrying the tow-configured
HMMWV (7900 lb) externally and a crew of three (750 lb)
internally out to 50 NM and return with 20 minutes of 10%
initial fuel, whichever is greater.4
     The Pentagon plan would replace plans for the Ospreys
with a mix of CH-53E and HH-60 helicopters to meet the Corps'
medium and heavy lift needs.  A Pentagon cost comparison done
in 1989 showed that buying 176 CH-53 and 590 HH-60 helicopters
would cost $6 billion more than the Ospreys, if produced
jointly by Bell-Boeing.  If there were competition between
Bell and Boeing for the Osprey line, the V-22 savings would be
about $8.5 billion on the helicopters according to DOD.
     The helicopters would be cheaper if the CH-53Es were used
in a double sling mode--meaning they were rigged to carry two
HMMWVs instead of one.  Under the double sling proposal, the
Corps would need only 225 CH-53Es and 478 HH-60s to meet its
needs, saving about $2.2 billion over the Osprey.  CMC reports
he considers this dialogue of dual sling options totally
ridiculous.  "It has nothing to do with coming from the sea in
a wide variety of scenarios . . . It has nothing to do with
     To make the double sling work, vehicles must be bolted
together on ship before they may be carried ashore, creating
an extra logistical and administrative burden.  Once ashore,
the equipment must be unbolted before it can be used, which
would impede the speed and flexibility of the assault.  Anyone
who has ever planned an amphibious operation knows we don't
need a problem like this.  The deck would be fouled for a long
time while we bolted the vehicles together.  There simply
isn't enough room aboard a ship to do this effectively.
     The CH-53E and HH-60 mix has other problems.  The CH-53E
was built for logistics and endurance on the battlefield.  It
was never designed as an assault helicopter, but we have used
it like that in some situations.  It simply was not designed
to land on the sloping terrain in an assault like a CH-46, and
it has a tremendous radar signature.
     The Black Hawk carries about half the troops as the CH-46
or the Osprey.  We would have to get twice as many helicopters
and twice as many pilots and crew chiefs to get the same lift
as a CH-46 or Osprey.  There isn't a snowball's chance in hell
of getting any extra Marines in the fiscal situation we are
in.  We would need extra support equipment to maintain the
helicopter mix envisioned by the Pentagon.
     In a 20 February 1990 House Armed Services Committee
hearing in response to repeated questions about the V-22
Osprey program cancelled by the Secretary of Defense, CMC
said, "finding an aircraft to meet the Corps' medium lift
needs is the most pressing issue for Marines this year.  The
aging CH-46 helicopter is entering its 26th year of service
life.  While it has served us well, we can no longer expect it
to carry Marines in harm's way on the modern battlefield."
Gray said, "Precision guided munitions and hand-held
surface-to-air missiles place the 30-year old helicopters and
the Marines they carry at risk."
     The Commandant has urged Congress to take a new look at
the affordability issue surrounding the V-22 Osprey.  Navy
Secretary Lawrence Garrett has said the Navy stands by the
Pentagon decision to cancel the program.  The Secretary of
Defense has recently testified that it's a great concept, but
that it's an affordability issue.  The Osprey would not be
affordable if bought for Marine Corps use alone.
     Given the era of declining budgets, the Pentagon must
consider multi-mission aircraft for the future.  The V-22 has
potential for missions like antisubmarine warfare, special ops
and drug interdiction.  We are at the upper edge of the
helicopter technology envelope and if we want to make a
significant leap in capability, we must pursue a different
avenue.  As soon as the Osprey started flying, the Marine
Corps would have to fight for their delivery positions.  The
other services would jump on the bandwagon as soon as they
started flying.
     A bipartison coalition of eleven lawmakers recently held
a pro-Osprey press conference in front of the National Air and
Space Museum to lobby for continued funding of the V-22.  The
Department of Defense has ignored the direction of the
legislative branch by cancelling contracting for the aircraft
while Congress was in recess.  The lawmakers are touting the
V-22 for its commercial benefits in addition to its military
function.  Without a guaranteed military market, the V-22s
manufacturers would not continue spending money on the
aircraft.  It is unlikely any airline would order it until
they see it in production and operation.
     The Congressmen are seeking to have the Federal Aviation
Administration use one of the V-22 prototypes as a new
technology demonstrator and evaluation aircraft.  They also
want the FAA to continue its present research studies into
tilt-rotor technology.  Senator Gramm called the V-22's
tilt-rotor technology the way of the future and reported
Japanese, West German and French companies are all considering
production of such aircraft.  He warned if the United States
does not produce the V-22, we could lose thousands of jobs and
sales to foreign companies in the 1990's.5
     I have read articles saying the Japanese have hired
several designers from Bell Helicopters to develop a similar
aircraft for commercial and military markets.  Recently, an
article in Aviation Week stated the Japanese had let a
contract in Fort Worth, Texas to construct a manufacturing
facility for aircraft production.  I believe a tilt-rotor will
be built but will it have an American or foreign label?
     The medium lift replacement program has the Marine Corps
scrambling to find a stop-gap replacement for the cancelled
V-22 Osprey.  The Navy and Marine Corps have spent over $2
billion in the research and development of the tilt-rotor, a
multipurpose aircraft that can take off and land like a
traditional helicopter and transition to a conventional fixed
wing aircraft in forward flight.  I doubt the Marine Corps
will pursue another Marine only aircraft because of the cost.
This eliminates the Boeing 360 from consideration.  The EH-101
is not much farther along in development than the V-22 and
possesses several serious drawbacks, including the fact that
it is not armored, carries its fuel under the aircraft rather
than in outboard sponsons and does not possess the troop
carrying capacity we require.
     Assuming the V-22 does not get put back in the budget by
Congress, upgrading our fleet of CH-46 helicopters and
supplementing them with some new CH-46 airframes is possibly
the cheapest alternative.  There is not more time for research
and development of another airframe.  The CH-46 is rapidly
approaching the end of its service life in ever-increasing
numbers.  Some CH-46 aircraft may have to be parked because
the dynamic components are reaching the end of their service
life and we don't have replacements on board.  The drawback to
remanufacture and SLEP of existing CH-46 airframes is--we will
have them for 20-30 years.
     I believe Congress will save the Osprey because of its
commercial applications.  The Marine Corps is still convinced
that tilt-rotor or tilt-wing technology is the way to go,
because the helicopter is physically constrained to a maximum
forward speed.  Eventually we may have an entire family of
tilt-rotor aircraft, both larger and smaller than the size of
the present V-22, performing a variety of heavy lift and
escort/gunship roles.  A tilt-rotor variant could replace the
OA-4 and OV-10 also.  This development must continue even if
the Marine Corps buys something else because the concept of
tilt-rotor or tilt-wing is too good to abandon.
Click here to view image
     1  William H. Gregory, "Vertol Flys CH-46A Assault
Helicopter,"  Aviation Week and Space Technology Magazine,
October 22, 1962, p. 30.
     2  David A. Anderton, "Vertol 107 Aims at Low Cost
Versatility," Aviation Week and Space Technology Magazine,
March 6, 1961, p. 53.
     3  David F. Bond, "CH-46E Replacement May be CH-46X:
Marines Believe UH-60 is Too Small," Aviation Week and Space
Technology Magazine, February 19, 1990, p. 18.
     4  J. P. Cress, Director, Naval Air Systems Command
Detachment, Program Manager Air (Field) -266, Marine Corps Air
Station, Cherry Point, North Carolina, letter about USMC CH-46
restart program.
     5  Elizabeth Donovan and David Steigman, "Gray: V-22
Substitute Scheme 'Ridiculous'," Navv Times, March 5, 1990,
p. 4.
Anderton, David A., "Vertol 107 Aims at Low Cost Versatility."
       Aviation Week and Space Technology Magazine, March 6,
       1961, 52-57.
Bond, David F., "CH-46E Replacement May Be CH-46X; Marines
       Believe UH-60 Is Too Small."  Aviation Week and Space
       Technology Magazine, February 19, 1990, 18.
Cress, J. P., Director, Naval Air Systems Command Detachment,
       Program Manager Air (Field) -226, Marine Corps Air
       Station, Cherry Point, North Carolina, letter about
       USMC CH-46 restart program.
Donovan, Elizabeth and David Steigman, "Gray: V-22 Substitute
       Scheme 'Ridiculous,'" Navy Times, March 5, 1990, 4.
Gregory, William H., "Vertol Flys CH-46A Assault Helicopter."
       Aviation Week and Space Technology Magazine, October
       22, 1962, 30-32.
Holzer, Robert, "Marine Corps Scrambles to Replace Cancelled
       V-22."  Defense News, February 26, 1990, 3.
Department of the Navy.  "Assault Support Helicopter Tactical
       Manual (U) MWP 55-9-ASH, Volume 1 (Rev D), September

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