The V-22 OSPREY   1


Running Head: THE V-22 OSPREY: PROJECT BACKGROUND AND SYSTEMS

            OVERVIEW




           T...
The V-22 OSPREY        2


                             Table of Contents

Title                                          ...
The V-22 OSPREY      3


                                             Abstract

The V-22 employs the tiltrotor system, whi...
The V-22 OSPREY          4


                                          Mission Summary

       Fixed wing aircraft have th...
The V-22 OSPREY          5


gives the greatest airborne time for fuel consumed. However, there is no expectation of repea...
The V-22 OSPREY           6


between the rotor and fuselage in airplane mode are also a guiding reference frame for the l...
The V-22 OSPREY         7


the development of this industry. However, the idea was later abandon due to unacceptable roto...
The V-22 OSPREY            8


         Administrative scenarios were also conducive for the development of the XV-15. The...
The V-22 OSPREY         9


Despite the achievements of the XV-15 in the tests, it never made it to production because arm...
The V-22 OSPREY         10


were for the development and manufacturing of the Osprey. However, Navy secretary John

Lehma...
The V-22 OSPREY           11


political and technological. However, it is evident that even though technological advancem...
The V-22 OSPREY          12


combat radius to about 500 miles and may carry a 50-caliber GAU-19 nose gun for self-defence...
The V-22 OSPREY         13


preparation against guided missiles, navigation improvements, lower body antenna, dual digita...
The V-22 OSPREY          14


       Transition from helicopter mode flight to aircraft mode flight and the vice versa req...
The V-22 OSPREY           15


recommended accelerated procurement of 458 production aircraft (360 MV-22s for the Marines;...
The V-22 OSPREY          16


a net-centric warfare era. The reason for asserting such an idea is the amount of expansion ...
The V-22 OSPREY        17


                                            References

Bolkom, C. (13 March 2007). V-22 Ospre...
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V-22 Osprey program history and systems overview

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V-22 Osprey program history and systems overview

  1. 1. The V-22 OSPREY 1 Running Head: THE V-22 OSPREY: PROJECT BACKGROUND AND SYSTEMS OVERVIEW The V-22 OSPREY: Project Background and Systems Overview Mersie A. Melke Embry-Riddle Aeronautical University Daytona Beach, Florida Department of Distance Learning Instructor: Dr. Daniel Nation January 20, 2009
  2. 2. The V-22 OSPREY 2 Table of Contents Title Page Abstract 3 Mission Summary 4 Development History 6 Systems Overview 11 Project Cost and Unit Cost 14 Concluding Remarks 15 References 17
  3. 3. The V-22 OSPREY 3 Abstract The V-22 employs the tiltrotor system, which refers to that area of rotor orientation between the one for a helicopter and a turbo prop powered aircraft. The tiltrotor system enables directing the engines’ thrust to change flight mode from hover to cruise or vice versa by vectored thrust. This capability makes the V-22 the choice of the United States Marine Corps. In addition, the United States Air Force and Navy have their version of the V-22 in development. However, the Osprey went through demanding developmental tests to acquire this reputation. This paper will show the challenges involved, the electronic advancements for net-centric warfare displayed on this aircraft and the costs incurred in paying for the demands of the project.
  4. 4. The V-22 OSPREY 4 Mission Summary Fixed wing aircraft have the advantage of speed, cruise altitude and range when compared with helicopters. Similarly, helicopters are agile and are capable of carrying out flight maneuvers impossible for fixed wing aircraft. The V-22 Osprey is a tilt rotor aircraft with a mixed capability of both a fixed wing aircraft and a helicopter. Its operation envelop covers both the helicopter and fixed wing aircraft area. This gives it an advantage over both types of flying machines. Such kind of a benefit was what the United States Marine Corps (USMC) was looking for that led to the development of the Osprey, amongst other requirements. In the following paragraphs, the mission summary of this aircraft will be analysed. Standoff advantage is a term used concurrent with military assault, which means being able to attack the enemy from a long distance away, and at the same time hampering the ability of the defending forces to attack the invading fleet at sea (Mark, 1997). In this kind of operation, range, maneuveribility and payload of aircraft will be the deciding factors in determining the side with a continuously attacking front line. Helicopters even though have the advantage of aerial agility are not a correct choice in terms of payload size. In addition, fixed wing aircraft have the disadvantage of maneuveribility. A study by Bell Helicopter had shown that a tilt rotor’s combination of range and payload would enable the ships involved in an amphibious assault to remain several hundred of kilometres from the beach, while the tilt rotors delivered troops and materiel for the invasion (Mark, 1997). Consequently, in an amphibious assault involving troop lift, the USMC expects Ospreys to carry a payload of 5760 pounds(lbs) or 24 troops over a range of 50 nautical miles(NM) and repeat the mission without loiters or maneuvers with a fuel reserve of 30 minutes at best endurance air speed (VBE) or 10 percent whichever is higher. The VBE refers to the speed that
  5. 5. The V-22 OSPREY 5 gives the greatest airborne time for fuel consumed. However, there is no expectation of repeat mission requirements in land assaults and the flight range is 200 NM (Rosenstein, Clark, 1986). In addition, in amphibious and land assault involving external cargo lift the V-22 must carry a payload of 8300 lb over a 50 NM range with a 30-minute fuel reserve at VBE or 10 percent whichever is greater (Rosenstein, Clark, 1986). Having the capability stated above in an aircraft that would take up a lesser space is also one of the requirements of the V-22 Osprey. The aircraft can fold its rotor and wing as a whole when in storage and therefore has space saving advantages on an aircraft carrier. A contrasting example would be the storage space for a CH-46 Chinook tandem rotor helicopter to that of the V-22. The V-22 goes in to storage mode by first folding its proprotors inboard when the nacelle is vertically oriented at 900 to the wingspan and then the nacelles assume a position parallel to the wings, which will turn clockwise parking on the roof of the aircraft. Proprotor is the term given to the blades of the V-22, which function as propellers during aircraft mode and rotors in helicopter mode. Concurrent with space availability on carrier ships the V-22 should vertically take off and land on different amphibious assault ships that are part of the United States Navy (USN) fleet. V-22 design specifications call for operationally spotting a minimum of 30 aircraft on LHA or LHD class ships (Rosenstein, Clark, 1986). LHA or LHD class ships are types of amphibious assault ship found within the USN. Concurrently the V-22 must be able to operate adjacent to the control tower on a LHA. A minimum clearance of 12 feet 8 inches from the control tower of the ship to the right rotor tip is one of the driving dimensional requirements. In addition, 5 feet clearance from the left landing gear to the edge of the deck coupled with a 1-foot clearance
  6. 6. The V-22 OSPREY 6 between the rotor and fuselage in airplane mode are also a guiding reference frame for the lateral size of the aircraft (Rosenstein, Clark, 1986). In addition to the amphibious assault capabilities examined earlier, the V-22 are also required to under take troop lift and external cargo lift in land assault operations by the USMC. Also combat search and rescue (CSAR) capability of four personnel over a range of 460 NM for the USN is part of the V-22’s mission summary. Long range special operations with a payload of 12 troops over a range of 520 NM for the United States Air Force (USAF) and self deployment missions over a maximum range of 2100 NM with only a crew of three is expected from the Ospreys (Rosenstein, Clark, 1986). Currently the V-22 can carry 24 fully equipped marines, cruise at speeds of 510 Kilometres per hour (Kph), and has a top speed of 560 Kph (Mark, 1997). In order to come to this kind of achievement both performance and payload wise, development of a series of aircraft took place since the end of World War II changing the tiltrotor aircraft industry. The following section will examine the history behind tiltrotors and the V-22. Development history The idea of an aircraft with the ability to hover like a helicopter and cruise like a fixed wing aircraft dates back as early as the 1930s when the Baynes Heliplane was proposed in Britain but was never manufactured. After this, an entrepreneur by the name Robert Lichten was one of the first proponents of the tiltrotor aircraft who in 1950 formed a company to commercialize the idea. Lichten’s first tiltrotor vehicle, the Transcendental Model 1-G, hovered several times in 1954 but never achieved full conversion from vertical to horizontal flight (Mark, 1997). Boeing Vertol VZ-2 tilt wing of the 1950s was also another milestone in the process of
  7. 7. The V-22 OSPREY 7 the development of this industry. However, the idea was later abandon due to unacceptable rotor disc loading (Schneider, 1989). On going research in to the field had lead to the finding that weight penalty was the governing factor that could change the capacity of the tiltrotor aircraft. Consequently the XV-3 propeller driven tiltrotor was developed. Lichten designed this aircraft in the mid 1950s when he joined the then Bell Helicopters of Fort Worth, Texas after his business failed (Mark, 1997). Thus in 1958 the XV-3 became the first tiltrotor to achieve full conversion from vertical to horizontal flight (Mark, 1997). The XV-3 tiltrotor was still flying in the mid-1960s, and its primary competition was the Vought XC-142A tiltwing. Crashes, linked to the XC- 142A’s mechanical complexity, disfigured this aircraft’s extensive flight research program. The Bell XV-3 also had problems, all of them linked to the fact that it was underpowered. The above-mentioned problems with existing tiltrotor aircraft and on going research to expand on achievements of the past led to the development of the XV-15. Labelling the XV-15 as the parent aircraft of the V-22 Osprey is appropriate, as it served as a test bed for the technology now found on the V-22. Advancements in the development of lighter materials used to manufacture aircraft structure supplemented the transfer from the XV-3 to the XV-15. In addition turboprop engines which have turbines that drive a propeller rather than a compressor as in the case of turbo jet engines, made it possible to alleviate the power problem of the XV-3 mentioned earlier. Consequently, the XV-15 was fitted with two turboprop engines on nacelles mounted at the tip of fixed wings. As a result, the thrust to weight ratio of the XV-15 increased and the problem of the mechanical complexities of the XV-3 with one engine on top of the fuselage was solved (Mark, 1997).
  8. 8. The V-22 OSPREY 8 Administrative scenarios were also conducive for the development of the XV-15. The National Aeronautics and Space Administration (NASA) and the United States Army had reasons to look in to the outcome of the development of this aircraft. NASA required building its database on the research of tiltrotor aircraft and the Army wanted to see the applicability of XV-15 to the field. Thus, in 1971, a new tiltrotor development program under the joint venture of NASA and US Army was initiated under a budget of 50 million U.S. dollars(USD) and the contract for building the XV-15 was awarded to Bell Helicopter Textron (Mark, 1997). The project had the advantage of using NASA’s Ames research center wind tunnel for full-scale aerodynamic tests. However, tests came up with problems of empennage vibration due to wake vortex developed by rotor when oriented at a certain angle. This called for additional strengthening of empennage structure. In addition, Bell Helicopter Textron had to come up with a new power transmission system to accommodate the variable position requirements of the engines of the XV-15, which was different from the proved helicopter-transmission designs of Bell (Mark, 1997). Consequently, manufacturing of two XV-15s took place and the first flight test happened on May 3, 1977 (Mark, 1997). Hans Mark who was the director of the Ames research center where the wind tunnel tests of the XV-15 took place states the following about one of the findings during the tests made there: “One of the most crucial tests was unscheduled. The XV-15 was the first tiltrotor with a safety feature known as a cross-shaft system, which is a mechanical linkage that enables one engine to turn both rotors. This system proved itself, unexpectedly, when an engine suddenly failed during a test flight. The cross shaft behaved as anticipated, enabling the pilot to bring the craft down safely.”
  9. 9. The V-22 OSPREY 9 Despite the achievements of the XV-15 in the tests, it never made it to production because army officials did not push for its procurement. In addition, an opposing group within the military posed the idea that unlike the tiltrotor, whose supporting role was to have been limited to medical evacuation, many of the new helicopters carried weapons. In this kind of situation, aircraft with firepower gather more support among the military leadership (Mark, 1997). Conversely, the performance the XV-15 showed during the test phase of the late 1970s influenced certain members of the United States government. Navy secretary John Lehman, Senator Barry Goldwater of Arizona and the commandant of the Marine Corps, General P. X. Kelley were the influential ones that involved by the XV-15 (Mark, 1997). As a result, a new era of tiltrotor development began which led to the transfer to the V-22 Osprey from the XV-15. Bell helicopter Textron and Boeing helicopters took the project in 1983. Initially the name of this project was the Joint Vertical Experimental aircraft (JVX). Both Boeing and Bell Textron had previous experience with tiltrotors. However, one remarkable thing about the development phase of the Osprey is that it still followed the intermittent approval scenario that shadowed the tiltrotor industry since the XV-3. After receiving the decision to move forward with development of the Osprey with a total budget of 1.7 billion USD, Bell and Boeing had faced budget approval problems as the project continued. One reason for this was the politics involved. The first flight of the V-22 Osprey took place in March of 1989 just one month before Secretary Richard Cheney took his initial action to stop the program (Jensen, 1991). Cheney claims to have taken this course of action because of affordability and priority (Jensen, 1991). In addition, people within the U.S. government like Dr. David S.C. Chu who was the Assistant Secretary of Defence (ASD) for Program Analysis and Evaluation (PA&E) initially
  10. 10. The V-22 OSPREY 10 were for the development and manufacturing of the Osprey. However, Navy secretary John Lehman who initiated the motion for the development of the V-22 claims that he had to fight Dr. Chu every year on the V-22 (Jensen, 1991). In fact, this debate had gone on to the point of abandoning the V-22 project and building new CH-46s. Apparently, replacing the aging CH-46 helicopters with the V-22s was the initial plan. The politics involved had also extended to the point of accusation of government representatives of favouritism for their respective states. When Secretary Cheney had addressed the V-22 program has affordability issues another proponent on the other side of the debate was republican Congressman Weldon (Jensen, 1991). Colonel Jensen in his paper entitled to clip an Osprey’s wings dated 20 December 1991 narrates the issue as follows: “Representative Weldon is one of the chief proponents of the V-22 on Capitol Hill. As such, he has been attacked as advocating the program solely because it would be partially produced in his district. In countering these charges Weldon says, ‘Those who say that V-22 is 'pork,' must admit that any alternative will be somebody's pork project, with a local constituency and 14 employment opportunities.’ It is worth noting that almost 40 states would have some stake in producing the V-22 and it is estimated that the program would employ about 35,000 people nationwide.” Another possibly terminal incident in the history of the V-22 project occurred in July 20, 1992 when a V-22 prototype crashed in the area of the Potomac river killing all seven marines onboard (Mark, 1997). After the 1992 crash, the future of the V-22 program again seemed in doubt. Yet the project got another boost later that year after the election of President Bill Clinton, whose first secretary of defence, William J. Perry, was a V-22 supporter. In conclusion, one can say that the history of the V-22 and the tiltrotor aircraft had gone through difficulties both
  11. 11. The V-22 OSPREY 11 political and technological. However, it is evident that even though technological advancements had favoured its development, political requirements had slowed down its production and thus have decreased its flight time. This lapse in production decreases the fleet experience the user systems would have acquired had the V-22 been deployed to its working environment earlier than the second quarter of fiscal year 2007.This is the time when the first V-22 passed into its Initial Operational Capability(IOC) stage. Systems Overview The Osprey is capable of both vertical and short takeoff and landing maneuvers (VSTOL). The difference between the two maneuvers is the amount of horizontal runway used which is the least with the former type of maneuver. The V-22 Osprey has three variants namely the MV-22 for USMC applications, the CV-22 for USAF usage and a third variant for the United States Navy designated HV-22. About 65% of the airframe is made of graphite-epoxy composite materials overlain with copper mesh to dissipate lightning strikes (Bolkom, 2007). It has an overall dimension of 57 feet (ft) 4 inches (in) long, 84 ft 7 in wide and 22 ft 1 in. The maximum proprotor speeds are 397 revolutions per minute (rpm) in helicopter mode and 333 rpm in airplane mode. Concurrently it has a rotor tip speed of Mach 0.69 in helicopter mode and Mach 0.66 in airplane mode (Larson, 1998). The MV-22 is a three-crew aircraft equipped with two T406 turbo shaft engines rated at 6150 shaft horsepower and optimised to increase shaft power. In addition, it has a maximum vertical takeoff weight capacity of 47,500 lbs and a maximum short take off weight capacity of 55,000 lbs with a speed of 250 knots at maximum weight and a combat radius in excess of 200 NM (Bolkom, 2007). The CV-22 is to carry 18 troops, with auxiliary fuel tanks increasing
  12. 12. The V-22 OSPREY 12 combat radius to about 500 miles and may carry a 50-caliber GAU-19 nose gun for self-defence (Bolkom, 2007). One thing that is common with all the variants of the V-22 is that 65% of the airframe is made from graphite-epoxy composite materials. The United States Department of Defence (DOD) plans to bring V-22s to the field in four blocks namely Blocks B and C for the USMC, and Blocks 10 and 20 for the USAF (Bolkom, 2007). Determination of these blocks is by the system architecture of the various variants. As a result, the MV-22 variant has the block A, B and C sub variants and the CV-22 have the sub variants mentioned. According to a Congressional Research Service (CRS) report for Congress, by Christopher Bolkom on 13 March 2007, these designs have the following differences amongst themselves. Block A MV-22s are for training and operation evaluation purposes (OPEVAL) with improvements to hydraulic line clearances and flight control software. Block B has improved nacelle maintenance provisions, retractable fuel probe, avionics upgrades, production icing system, ramp gun, hoist and improved fast rope location to deploy troops while in hover mode. Block C has flight incident recorder, radar altimeter sling load modification, fuel dump modification, weather radar, wheel well fire suppression, oil cooler inlet screen, main landing gear brake redesign, mid wing gear box indicator and cargo hook door upgrade. Block 20 of the CV-22 Ospreys has a system called Suite of Integrated Radio Frequency Countermeasures (SIRFC) for RF awareness and active self-protection jamming capabilities against RF, Directional Infrared Countermeasures (DIRCM) for protection against infrared weapon targeting, multi mode radar, flight engineer’s data display, flight engineer’s seat and low probability of intercept or detection radar altimeter. In addition, it employs, TCAS (terrain collision avoidance system), troop commander’s situational awareness, ALE-47 decoy for
  13. 13. The V-22 OSPREY 13 preparation against guided missiles, navigation improvements, lower body antenna, dual digital map and Global Air Traffic Management (GATM). The identifying features of the Block 20 of the CV-22 Osprey is that it has Geo-reference coupled approach to hover, terrain following below 50 knots corrections, heads up display (HUD), digital map system upgrades, great circle navigation corrections, performance calculator, passenger oxygen, Joint Tactical Radio System (JTRS) for software based radio communication, emergency power and fuel dump corrections. One can observe from the above configuration variations that avionics is the distinguishing factor between the five types of V-22s. This emphasizes the evolution of electronics and its military applications. All the variants have similar airframe and power plant. The two wing tip mounted power plant are cross connect by the cross shaft assembly. The purpose of this shaft is to protect the Osprey from asymmetric flight path during engine shutdown of either engine. The architecture of the shaft is in segments and connected by flexible couplings (Cowan, 1996). In addition, the Osprey has three hydraulic systems that supply hydraulic power of 5000 pounds per square inch (Larson, 1998) for the cyclic and collective controls of the rotor blades in both aircraft and helicopter mode (Cowan, 1996). The hydraulic system has pumps deriving motive power from the engines, an Auxiliary Power Unit (APU) and the cross shaft assembly. The pump installation on the cross shaft assembly impedes vibration when both engines are running and the shaft is not in use (Cowan, 1996). In addition, there are two electric power generators installed with the engines and two more in the fuselage with an additional battery capable of providing power for 20 minutes in case of loss of power from the four generators (Larson, 1998).
  14. 14. The V-22 OSPREY 14 Transition from helicopter mode flight to aircraft mode flight and the vice versa requires a smooth and precise transition. On the V-22, the fly- by- wire system makes this possible. This system translates control stick inputs from the cockpit into electrical inputs that operate the various flight controls. The fly-by-wire system on the V-22 has a triple redundancy failure path, which adds to the safety feature of the aircraft (Cowan, 1996). Mandatory operation zones of the nacelle orientation are between 600 and 950 from the wing plane for aircraft speed of 100 to 200 knots other than which stalling might occur (Larson, 1998). In addition, from survivability perspective, routing of electrical and hydraulic lines in font and aft spar of the wing ensure a single hit will not stop flight critical systems (Cowan, 1996). Also an on board generator extracts nitrogen from the atmosphere and pumps it to the fuel tank to avoid incidents of fuel tank explosion (Larson, 1998). Project costs and Unit costs In 1989, DOD projected a 663-aircraft program with 6 prototypes and 657 production aircraft (552 MV-22s, 55 CV-22s, and 50 HV-22s). However, in 1994, these figures were changed and the program comprised 523 production aircraft (425 MV-22s, 50 CV-22s, and 48 HV-22s). It is inevitable to notice the chronological relation between decrease in V-22 orders and the political and technical issues of the early 1990s concurrent with the V-22. The previous section mentioned these issues. Procurement of these 523 aircraft was to continue into the 2020s due to the Defence Acquisition Board limited annual expenditures for Marine MV-22s to $1 billion USD (FY1994 dollars) when it approved entry into engineering and manufacturing development (EMD) in September 1994 (Bolkom, 2007). Another development in the budget allocation of the V-22 was because of the Quadrennial Defence Review (QDR), released May 19, 1997. This review
  15. 15. The V-22 OSPREY 15 recommended accelerated procurement of 458 production aircraft (360 MV-22s for the Marines; 50 Air Force CV-22s; and 48 Navy HV-22s).Thus the current projection is for a 458-aircraft program (Bolkom, 2007). Unit cost of V-22 ospreys has also changed. Initially the cost for one V-22 Osprey in its baseline configuration was 41 million USD (Cowan, 1996). However, the introduction of computer aided engineering together with integrated product teams that are responsible for the audit and smoothness of project flow have decreased the unit price to an estimated 31 million USD with a goal of reaching 29.4 million USD (Cowan, 1996). The flight envelop of the V-22 Osprey traces the territories of both the C-130 turbo-prop aircraft and the UH-60 helicopter (Larson, 1998). The former has an operating speed range of 75 to 300 knots and a maximum cruising altitude of 25,000 feet whereas the latter has a maximum operating speed of 140 knots with a cruising altitude of 18,000 feet (Larson, 1998). Cost wise the C-130 ranges from 11.9 million USD to 48.5 million USD (n.d, 2009) and the UH-60 costs between 5.9 million USD to 10.2 million USD (n.d, 2009). Comparing these data with the V-22’s maximum operating speed of 275 knots, maximum cruising height of 25,000 feet and estimate unit cost of 31 million USD, the financial and operational gains the users can get out of the Osprey become apparent. This of course is leaving out detailed contrasting of the different capabilities of the individual aircraft. Concluding Remarks From the XV-3 to the XV-15 and now the V-22 Osprey, the tiltrotor aircraft has gone through the advancements examined in this paper. The politics involved with the development of this aircraft is not a simple matter. This paper has shown that the development of the V-22 was a complex process. In addition, the technology on the aircraft defines the US armed forces drive to
  16. 16. The V-22 OSPREY 16 a net-centric warfare era. The reason for asserting such an idea is the amount of expansion on avionic utilities used on the V-22 ever since it made its debut flight back in 1979. Research done during preparing this paper has shown that the V-22 is an aircraft on a continuing development phase, despite the first delivery of the MV-22 in 2007. In addition, an extended delivery date might have enriched the test findings but conversely it has decreased the actual combat experience of the fleet. However, a benefit of this extended delivery date is the beginning of the computer edge. In the 1980s when computer technology was at its infancy the V-22 would have cost approximately an additional 10 million USD from what it costs today because of the lack of the organizing and facilitating capability of computers. Another noticeable feature of the V-22 development project is the intermittent attitude of people in power that decide the fate of the aircraft. This is a reminder of the changing behaviour of a political environment. As Colonel Jensen put it in his paper dated 20 December 1991, “No issue is decided once and for all in bureaucratic politics.” This paper documented such kinds of changes towards the V-22 Osprey and discussed on its implications. Another point made by Col. Jensen was, “Whose position prevails can become more important than which position prevails.” Therefore, one cannot fully predict on the future of the V-22 considering the past it has come through. However, the V-22 has become a breakthrough in the tiltrotor transport system whatever fate comes in its way.
  17. 17. The V-22 OSPREY 17 References Bolkom, C. (13 March 2007). V-22 Osprey Tiltrotor Aircraft. CRS Report for Congress. Cowan, R. (September, 1996). Examining the V22 Osprey. Defence Helicopter, 15, 24-26. H-60 Black Hawk. Retrieved January 16, 2009, from http://www.globalsecurity.org/military/systems/aircraft/h-60.htm Jensen, H. (20 December 1991).To Clip An Osprey’s Wings. A Paper for Course III: The National Security Policy Process. The National War College. Larson, G.C. (October-November, 1998). Extreme Machine [V-22 Osprey]. Air and Space, 13, 26-35. Mark, H. (October, 1997). Straight up into the Air [tiltrotor aircraft]. Scientific American, 277, 110-115. Rosenstein, H. and Clark, R. (October 20, 1989). Aerodynamic Development of V-22 Tiltrotor. Paper presented on Aircraft Systems, Design and Technology Meeting in Dayton, Ohio. Schneider, J. ( August 2, 1989). Advanced V/STOL Attack Aircraft Design/ Operations Trade- off. Paper presented on Aircraft Design, Systems and Operations Conference in Seattle, Wa. U.S. Air Force Fact Sheet C-130 Hercules. Retrieved January 16, 2009, from http://www.af.mil/factsheets/factsheet.asp?fsID=92

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