The world has had a large number of long runways in almost every
corner since the Second World War, but today military experts are trying to
get away from the use of them, in fear of the havoc that might be caused by
their destruction in wartime. As a result, Helicopters where invented to
eliminate the long runways and were used vastly in military. They were of
vertical take-off and landing (VTOL) type aircraft. But the limitations were
very significant. Short range, less capacity, slow speed etc. Thus the challenge
has been to device a vehicle that is faster, has more range and is more cost
effective than conventional Helicopters.
As a result, In 1989, two big aircrafts builders Bell and Boeing jointly
build an aircraft for the U.S Military and named it as ‘V-22 Osprey’. (The
word ‘Osprey’ is the name of a fish eating bird found in South America,
which is 60cm long with a 162cm wingspan)
The V-22 tilt rotor is a revolutionary, vertical and short take-off and
land (V/STOL), multi-purpose aircraft with excellent high-speed cruise
performance. This advanced technology rotorcraft performs a wide range of
V/STOL missions as effectively as a conventional helicopter, while equally
capable of achieving the long-range cruise efficiencies of a twin turboprop
aircraft. It brings capabilities not found in any helicopter – twice the speed,
three times the payload and five times the range of the legacy helicopters that
it replaces. Add the ability to fly two and a half times higher than those
helicopters and you have an aircraft that is truly a leap ahead.
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2. History and Development
The need of an aircraft, which is much better than Helicopters, was
aroused in 1950's. The ‘Tilt Rotor” concept comes into play at that time
and on 18 December 1958, the first tilt rotor vehicle named Bell XV-3
constructed by Bell Helicopters, made the history by converting Helicopter to
Aeroplane by the use of tilt rotor. The flights and testing continued till 1966,
when the program proved that the idea was practical there were many
problems to overcome. Experienced aerodynamits have pointed out that the
propeller or rotor does not provide much motive force, but only stirs the
around it, unless there is wind flow into it. A conventional airplane develops
sufficient speed on the runway to quarantee good airflow into the propeller
(or jet engine) by take-off time. A conventional helicopter sets into motion a
large airmass that is drawn downwards into the rotor, before rising. An
aircraft that attempts to pivot its engines while aloft is subjected to thrust
failure because of the paucity of airstream arriving at the rotors from the
newly selected aspect.
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To overcome all the difficalties, a lot of years had taken up for
calculations, repeated designs, imaginary testings etc. At that time U.S
Military invitted Boeing Aircraft Company to joint with Bell Helicopters to
construct a new tiltrotor aircraft.
On March 1989, the tilt rotor aircraft code named V-22 Osprey built by
Bell-Boeing aircraft made its first flight. Since then however there have been
four significant failures during testing -a crash in 1991, killed seven men in
1992, killed nineteen on April 2000 and four on December 2000. The testing
continued till March 2005 and the company claimed that the aircraft is ready
for final production. The first order for production was from the U.S Military
for 458 Ospreys for $37.3 Billion.
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Like any aircraft, the Osprey has the following systems:
3. Cockpit Controls
Osprey's External Features
3.1 Propulsion- The Osprey has two rotors with three-bladed propellers.
An Allison AE 1107C turbo shaft engine that is capable of producing over
6,000 horsepower drives each propeller. Each engine drives its own rotor and
transfers some power to a mid-wing gearbox. This gearbox drives the tilting
mechanism. In the event of an engine failure, the Osprey is capable of running
on only one engine. In this case, power from the remaining engine is
distributed to the two rotors through an interconnecting drive shaft. A
transmission interconnect shaft provides single-engine operation.
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3.2 Fuel- The Osprey has 16 fuel tanks, 10 integrated into the wings and six in
the fuselage. The feed tanks directly supply the engines with fuel from the
other tanks, and fuel transfer is automatic. As the fuel flows from the tanks,
pressurized nitrogen gas fills the tanks to reduce the possibility of fire.
Depending upon the configuration of the Osprey, it can hold from 1,450 to
3,640 gallons (5,489 to 13,779 liters) of fuel.
Osprey’s Fuel Tanks
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3.2 Cockpit Controls- The cockpit of the Osprey holds a pilot and co-pilot. In
addition, there is a fold-down seat in the center behind the pilots for a flight
engineer. The instrument panels have multi-functional displays, similar to the
new glass cockpit of the space shuttle. The displays hold information about
the engines (such as oil pressure, temperatures and hydraulic pressures) and
flight (such as fuel data, attitude and engine performance). There are also
keypads used to interact with the flight computer and sticks used to control
the flight maneuvers.
Osprey’s Control Panels
3.4 Communications- The Osprey is equipped with multi-band radios (AM,
FM, UHF, VHF) for voice transmission and radio reception. It also has
navigational beacons and radios, radar altimeters and an internal
intercom /radio system for communications among the crew and troops
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Osprey’s Control Panels
3.5 Payload- The Osprey can hold up to 24 troops and carry up to 20,000 lb
(9,072 kg) in its cargo bay, which is 5.7 ft wide by 5.5 ft high by 20.8 ft long
(1.72 x 1.68 x 6.35 m). The cargo bay has fold-down seats along the walls and a
ramp that is used to load or deploy cargo and troops. Deployment can also
take place in the air by parachute. In addition to the 20,000-lb load in the
cargo bay, the Osprey has an external hook-and-winch system that allows it to
carry up to 15,000 lbs (6,803 kg) of cargo in tow.
3.6 Stowage -When the Osprey lands on the deck of a ship, it can be folded up
for down-time. The blades and the wings are both foldable. The figures
below, shows the four stages of Stowage of Osprey. The top left and right
figures shows the blades are folded inward, the bottom left shows the wings
turn up and the bottom right shows the wings fold back.
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Four Stages of folding of Osprey for Stowage
4. Flying of Osprey
To understand how the Osprey flies, the basic thing to understand is
that airplane wings create lift by deflecting air downward, benefiting from the
equal and opposite reaction that results. Helicopters do the same thing with
blades, which are rotating wing shapes like the airfoils of an airplane wing.
Helicopter blades are thinner and narrower than airplane wings because they
have to rotate so fast. These rotating wings are mounted on a central shaft.
When the shaft is spun, lift is created.
There are two modes during the flying of Osprey. Helicopter mode and
Airplane mode. Tilting the two rotors of the Osprey does the change of mode.
When the Osprey is ready to take off, the aircraft will be in Helicopter
mode, i.e. the two rotors are in a vertical position. With the rotors mounted on
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the wings, it looks like a two-bladed helicopter. The two rotors rotates on
opposite directions to stabilize the aircraft and creates the lift.
Osprey on Helicopter mode
While in flight, the Osprey converts into the airplane mode by moving
(tilting) the rotors down to a horizontal position. The conversion will takes
approximately 5 to 12 seconds. In this position, it is the wings that generate
lift, like on a traditional airplane, and the rotors function as they on a
traditional airplane, and the rotors function as they do in a propeller aircraft.
Osprey on Airplane mode
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The Osprey lands like a helicopter by reversing the process, raising the
rotors from a horizontal to a vertical position. That means the osprey uses its
Helicopter mode during take-off, landing and when hovering and Airplane
mode during the flight.
V22 OSPREY transforming from Helicopter mode to Airplane mode
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5. Advantages over Aeroplane and Helicopter
The major advantages of Osprey over a Helicopter are:
Longer Range - The Osprey can fly from 270 to 580 miles (453
to 933 km), i.e. Five times more than
Higher Speed - The Osprey’s top speed is 315 mph (507 kph),
which is twice as fast Helicopter’s top speed.
Increased Cargo Capacity - The Osprey can carry 10,000 pounds (4536 kg)
of cargo or 24 troops.
The advantage of the Osprey over an airplane is that it can take off, hover and
land like a helicopter. This makes is more versatile than an airplane for such
missions as moving troops to remote areas, especially those without landing
strips, or conducting long-range rescue operations at sea.
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Amphibious assault transport of troops, equipment
and supplies from assault ships and land bases.
Boeing Defense and Space Group, Philadelphia, PA.
Prime Contractor(s) Bell Helicopter Textron, Ft Worth, TX.
Allison Engine Company, Indianapolis, IN.
The V-22 Osprey is a multi-engine, dual-piloted, self-
deployable, medium lift, vertical takeoff and landing
(VTOL) tiltrotor aircraft designed for combat, combat
Description support, combat service support, and Special
Operations missions worldwide. It will replace the
Corps' aged fleet of CH-46E and CH-53D medium lift
CV-22 will be utilized by the Air Force for their
Special Operations missions maintaining maximum
commonality with the MV-22. Aircraft avionics
Variants peculiar to the Air Force unique mission requirements
constitute aircraft differences.
HV-22 will be used Navy the for Combat Search
and Rescue and fleet logistics support.
57' 4" - Spread
63' 0" - Folded
84' 7" - Spread
18' 5" - Folded
22' 1" - Spread
18' 1" – Folded
47,500 lb Vertical Takeoff/Landing (VTOL)
Takeoff Weights 55,000 lb Short Takeoff/Landing (STOL)
60,500 lb Self Deploy STO
200nm Pre-Assault Raid with 18 troops
200nm Land Assault with 24 troops
50 nm (x2) Amphibious Assault
500 nm Long Range SOF Missions (USAF/CV-22)
2100 nm Self Deploy (with one refueling)
50 nm External Lift Operations with 10,000 lb load
240 kts (MV-22)
230 kts (CV-22)
Crew Cockpit - Crew seats - 2
Cabin - Troop seats- 24
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7. Aerodynamic Force
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There are 4 basic Aerodynamic forces: Lift, Thrust, Weight and Drag.
In order for an airplane to fly straight and level, the following relationships
must be true:
Thrust = Drag
Lift = Weight
If, for any reason, the amount of drag becomes larger than the amount of
thrust, the plane will slow down. If the thrust is increased so that it is greater
than the drag, the plane will speed up.
Similarly, if the amount of lift drops below the weight of the airplane, the
plane will descend. By increasing the lift, the pilot can make the airplane
7.1 Thrust - Thrust is an aerodynamic force that must be created by an
airplane in order to overcome the drag (notice that thrust and drag act in
opposite directions in the figure above). Airplanes create thrust using
propellers, jet engines or rockets.
7.2 Drag - Drag is an aerodynamic force that resists the motion of an object
moving through a fluid (air and water are both fluids). In this case the fluid is
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the atmosphere and the object is the airplane. This is opposite to Thrust.
7.3 Weight -This one is the easiest. This is due to the gravitational force of
earth on the plane.
7.4 Lift - Lift is the aerodynamic force that helps the airplane to raise from
the base and to hold the airplane in the air. It is the trickiest of the four
aerodynamic forces to explain without using a lot of math. On airplanes, most
of the lift required to keep the plane aloft is created by the wings (although
some is created by other parts of the structure). Lift is a force on a wing (or
any other solid object) immersed in a moving fluid and it acts perpendicular
to the flow of the fluid. Drag is the same thing, but acts parallel to the
direction of the fluid flow.
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The V-22 is a joint service, multi-mission aircraft with vertical take-off
and landing (VTOL) capability. It performs VTOL missions as effectively as a
conventional helicopter while also having the long-range cruise abilities of a
twin turboprop aircraft.
It has been used primarily in military applications due to its high load
carrying capacity. It has been widely used by the navy, army, marine and the
customs. The Marine Corps version, the MV-22A, is an assault transport for
troops, equipment and supplies, and is capable of operating from ships or
from expeditionary airfields ashore. The Navy's HV-22A provides combat
search and rescue, delivery and retrieval of special warfare teams along with
fleet logistic support transport. The Air Force CV-22A conducts long-range
special operations missions. Now in the future it will be used for civil
transport also. All round of developments is going on to public
transport. Maybe one day it will replace the present day Helicopters and
aircrafts. Let us wait and see.
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“UPAHAAR”, the CD Presented by ‘Voice of CET’.
Journal of THE AMERICAN HELICOPTER SOCIETY
TILT ROTOR TECHNOLOGY - Paper by Jim Garamone
Newsletter of THE PRATT WHITNEY COMPANY
Journal of MILITARY TRANSPORT
Fact File of the V-22 OSPREY
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