VSTOL History Overview - Rotorcraft General/history_overview_brief.pdf · Augmented Power Plant for...

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An Overview of the History of Vertical and/or Short Take-Off and Landing (V/STOL) Aircraft

Michael J. HirschbergCENTRA Technology, Inc.

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CENTRA Technology, Incwww.centratechnology.com

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V/STOL Wheel of Mis-Fortune

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2 4 M AY 63V

Curtiss-Wright X-100

Short SC.1

EWR VJ 101 CDornie r Do 31

Lockheed XV-4B VFW VAK 191 BMcDonnell XV-1

Vanguard 2C Omniplane

Lockheed AH-56

Combined Power Plant for Hover

Augmented Power Plant for Hover

Separate Power Plant for Hover

Same PropulsionSystem for

Hover and ForwardFlight

Doak 16 VZ-4

Bell XV-3

Bell X-22A

Vertol 76 VZ-2

Hille r X-18 LTV-Hil le r-Ryan XC-142

Transce ndental 1G

Canadair CL-84

Bell XV-15

Bell 65 ATVRobertson VTOL

Ryan VZ-3

Bell X-14Hawker P.1127 Kestrel

Yakovle v Yak-36BAe / Boeing Harrier

Lockheed XFV-1

Convair XF Y-1

Ryan X-13SNECMA C450 Coléoptère

V

MAR 54

THV

T

3 M AY 77

24 JUL 77

THV

DEC 5420 J UL 55

25 FEB 58

6 J UL 54

V

V

V V

TH

AUG 5525 OCT 56

MAR 60

APR 60

2 0 NOV 63

18 DE C 58TH

VTH 25 JUN 64

25 AUG 65

8 AUG 66

MAR 66

H

TH

T

JUN 67

23 J UL 68 All f lights t ethered

29 DE C 64

29 M AY 81

VH

VNord 500 Cadet

VTH

7 JAN 58

1 3 APR 57 15 J UL 58

V

TH 24 NOV 59

8 J AN 1957T et her ed Fl ig ht

H V

TH

11 J AN 6529 SEP 64

M AY 65

1 959 T et her ed Fl igh ts

17 FEB 57

21 JAN 59

V DE C 65

VFairchild 224 VZ-5

HFE B 60

1966

13 JUN 90

21 SEP 67Helicopter

Mode

1978Tethered T rials

H24 MAY 58

19 NOV 60

V T1957 V T

H

21 SEP 61

9 J AN 63

7 J UL 61

VTH AUG 66

V5 MAY 59

16 SE P 63TH

19 NOV 54

1955

VH

H T

VTH

AUG 54

1 AUG 54V2 NOV 54

10 DEC 55

28 MAY 56

2 APR 57

11 APR 57

V

6 APR 6018 M AR 63T

H 1 MAR 63

VDassaul t Mirage Balzac V

18 OCT 62

8 SE P 6527 JAN 64

H 24 JUL 6512 FEB 65

25 OCT 582 OCT 63

V

TV

2 8 NOV 66M AR 66

Dassault Mirage III-VH T

VTH

10 APR 63 20 SE P 63

31 AUG 6314 SEP 64

H

T

V

HVT

22 NOV 67

16 DEC 6710 FE B 67

14 M AR 69 THV10 SEP 71

26 OCT 72

V

VTH 1 1 F EB 54

6 NOV 57VH10 APR 58

Fairey RotodyneYakovlev Yak-38

V T26 SEP 71 20 M AR 72

15 JAN 71HYakovle v Yak-141

29 DEC 89

8 NOV 63

17 MAY 61

TLoc kheed XV-4A

7 J UL 62HV1 0 J UN 64

H 25 MAY 64 NOV 64

5 DEC 59T ethered Flight Rockwell XF V-12A

TJUN 64

APR 65 GE-Ryan XV-5AOCT 66

19641 960

Kamov Ka-22 VintokrylFE B 62Helicopter Mode

Piasecki 16H-1

VTH

VTHVTH

12 MAR 69

5 OCT 91

Bell Boeing V-22TH

V 19 M AR 89

14 SEP 89

H 9 M AR 87

Curtiss-Wright X-19

1955 1960 1965 1970 1975 1980 19851950 1990 1995 2000

V/STOL History: 1950 - 2000

Boeing X-32

Lockheed X-35

Bell Boeing V-22

Bell BA609

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V/STOL Jet Wheel

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Planned vs achieved maximum speed (clean) for V/STOL fighter aircraft

1960

1961

1962

1963

1964

1965

1966

1967

1968

1969

1970

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

Yea

r

1959

M

2.01.91.81.71.61.51.41.31.21.11.00.9

0.80.70.60.50.40.30.20.1

P.1127

III-VVJ 101C

Harrier

VAK 191

Yak-38

XFV-12A

Yak-141JSF

US/UK

Germany

USSR

France

The Quest for Supersonic V/STOL

Colé-optère

Yea

r

Mirage

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V/STOL Considerations• Balance

– Thrust and cg• Control

– Yaw, pitch, roll– Hover, transition, cruise

• Propulsion System – Volume, development cost/time, thrust matching

• Human Factors– Pilot workload, orientation, noise

• Environmental– Hot gas re-ingestion, footprint

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V/STOL Wheel of Mis-Fortune

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Same Propulsion System for Hover and Forward Flight


• Uses a single propulsion system

• Alters the direction of thrust for hover or cruise

• Can also alter the attitude of the aircraft itself

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Tilt Shaft/Rotor

• Rotating blades function like rotors in vertical flight, like propellers in forward flight

• Rotors are long articulated blades


• Blades have cyclic pitch control for hover

• Power plants remain stationary

• Power shaft pivots from vertical to horizontal

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1. Transcendental Model 1G• Powered by a single 160 hp

Lycoming O-290-A engine• Three bladed 17 ft rotors• Manual two speed reduction box• Rotor speed

– Hover: 240 rpm– Horizontal Flight: 633 rpm

• Three concentric shafts controlled tilt angle, cyclic pitch and collective pitch

• Suffered from dynamic stability problems

• Required three minutes to transition 82° during conversion

Flight Milestones• 6 July 1954 - First vertical flight • December 1954 - First horizontal flight • 1957 - Testing concluded• Model 1G flew over 100 flights and

logged 20 hours of flight time

Tilt Shaft/Rotor

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2. Bell XV-3• Powered by a 450 hp P&W R-985

radial engine• Single 24 ft two-bladed semi-rigid

rotor• Manual two-speed gear box similar

to Transcendental 1G• Three-bladed rotor instability led to

a two bladed design• Conversion over the full 90° could

be conducted in 10 seconds• Significant manipulation of pitch

and throttle controls required during conversion

• Inadequate power and high weight growth precluded the XV-3 from hovering out of ground effect

Flight Milestones• August 1955 - First vertical flight• 18 December 1958 - Full conversion by

second prototype• 1965 - Damaged in wind tunnel test• Made over 250 flights including 110

full conversions

Tilt Shaft/Rotor

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Tilt Prop

• Uses propellers instead of rotors


– Has collective but no cyclic pitch control

– Has short, rigid blades

– Has a high degree of twist

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3. Curtiss-Wright X-100• Powered by an 860 bhp Lycoming YT53-

L-1 mounted on the fuselage• Two 10 ft diameter tilting fiberglass

propellers on the wingtips• Engine exhaust at the rear of fuselage was

used for pitch and yaw control in hover• Roll control provided by differential

propeller pitch• Used to prove the Tilt Prop concept for

use on the Curtiss-Wright X-19• Used “radial force” instead of wing lift for

conventional flight • Control in hover was weak due to low

exhaust gas velocity

Flight Milestones• September 1959 - First vertical flight• March 1960 - First short take-off• April 1960 - First and only conversion• October 1961 - Testing concluded

Tilt Prop

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4. Curtiss-Wright X-19• Originally civil executive transport• Powered by two 2,650 shp

Lycoming T55-L-7 turboshaft engines

• Two tandem wings with a three-bladed 13 ft, wide chord, high twist propeller at each end

• Diagonally opposed propellers rotated in same direction to eliminate gyroscopic and torque effects

• Roll, pitch and yaw were controlled by differential propeller pitch

• Plagued by control system and other mechanical problems

Flight Milestones• 20 November 1963 - First vertical flight • 25 August 1965 - Crash due to

transmission failure• Made over 50 flights but logged only 4

hours of flight time

Tilt Prop

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Tilt Ducts

• Ducts can increase propeller

thrust by as much as 50% due

to Bernoulli Effect

• Ducts provide additional lift

during forward flight


• Propeller pitch and deflector vanes in downwash controlaircraft in hover and transition

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5. Doak 16 VZ-4• Powered by a single 860 bhp

Lycoming YT53 engine• One 4 ft eight-bladed tilting duct

propeller on each wing-tip• Transition from hover to 200 kt

could be performed in less than 20 seconds

• Variable inlet guide vanes used for roll control in hover

• Engine exhaust gases deflected at fuselage rear for pitch and yaw control

• Deceleration and descent had to be carefully controlled to prevent duct lip from stalling

• Suffered from lack of control power

Flight Milestones• 1957 - Aircraft is built• 15 February 1958 - First flight• Completed over 50 hours of testing

proving tilt duct concept

Tilt Ducts

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6. Bell X-22A• Powered by four cross-linked 1,250 shp

GE YT58-GE-8D turboshaft engines• The engines had 35% excess power in

case one engine failed in hover• Four 7 ft diameter three-bladed ducted

propellers• The ducts rotated non-differentially

from 0° to 95°• Hover control was possible through

differential propeller pitch• The propeller ducts provided a

significant amount of aerodynamic lift during forward flight

• Maximum speed was 315 mph• Limited payload and range• V/STOL testbed until 1980

Flight Milestones• March 1966 - First vertical flight• January 1967 - Second prototype

performed complete transitions• 20 July 1968 - Set record for hovering

at altitude of 8,000 ft• Flew until 1980 and logged about 200

hours of flight time

Tilt Ducts

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7. Nord 500 Cadet• Design and built by the French

Nord company (later part of Aérospatiale)

• Powered by two 317 shp Allison T63-A-5A engines

• Used two large five-bladed duct propellers

• Four control vanes in a diamond shape controlled yaw (differentially) and pitch (collectively)

• This configuration selected to try to expand airflow in hover and compress it during horizontal flight

• The project was cancelled without further testing after July 1968

Flight Milestones• 23 July 1968 - Second aircraft makes

tethered hover• Program cancelled without further

testing

Tilt Ducts

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Tilt Wing• Tilting entire wing

– Increased aerodynamic flow over lifting and control surfaces during transition

– Minimizes lift loss due to downwash in hover

• Additional method of control during hover is required– Tail jet– Tail rotor

• Ailerons change from roll control in forward flight to yaw control in hover

• During hover control is difficult in wind gusts due to “barn door effect” of wing in the vertical position


www.vstol.org

8. Vertol 76 VZ-2• Powered by a single 860 hp

Lycoming YT53-L-1 engine• Two 9.5 ft three bladed propellers

power by a cross shaft through the wings

• Fuselage was built of metal tube construction

• Used a two seat helicopter-like cockpit

• In hover, pitch and yaw control provided by two ducted propellers in the tail

• Aerodynamic controls were phased in during transition until the tail propellers were no longer needed for horizontal flight

• Poor control power

Flight Milestones• 13 August 1957 - First vertical flight• 7January 1958 - First horizontal flight• 15 July 1958 - First conversions• 1965 - Testing concluded• Made over 450 flights and 34

conversions

Tilt Wing

www.vstol.org

9. Hiller X-18• Powered by two wing-mounted

7,100 eshp Allison T40-A-14 turboshaft engines

• Pitch control thrust provided by one Westinghouse J34 turbojet

• Was able to complete only partial conversions with wing angles up to 33°

• Grounded after 20th flight due to propeller pitch control problem

• Continued to test ground effects before it was damaged in a test stand failure

• Turboprop engine electric pitch control too slow for hover control

• Never achieved hover flight

Flight Milestones• December 1958 - extensive ground

testing of loaded aircraft• 24 November 1959 - first conventional

flight• Never completed full conversion to

hover flight

Tilt Wing

www.vstol.org

10. LTV-Hiller-Ryan XC-142• Powered by four-cross linked

3,080 shp GE T64-GE-1 engines• Four 15.5 ft diameter four-bladed

propellers• Roll was controlled by differential

propeller pitch• Pitch was controlled by an 8 ft

three-bladed variable pitch tail rotor

• Yaw was controlled by ailerons powered by propeller slipstream

• Suffered from excessive vibration and noise, resulting in high pilot workload as well as cross-shaft and gear box failures due to wing flexing

Flight Milestones• 29 September 1964 - First conventional

flight• 29 December 1964 - First vertical flight• 11 January 1965 - First complete

transition• Logged 420 flight hours with 39 different

pilots

Tilt Wing

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11. Canadair CL-84 Dynavert• Powered by two wing-mounted

1450 shp Lycoming T53-LTC1K-4A turboprop engines

• Two cross-linked 14 ft four-bladed propellers

• Pitch control provided by two counter-rotating two-bladed horizontal propellers

• Roll control provided by differential propeller pitch

• Yaw control provided by the ailerons• Extensively evaluated, including

demonstrations on amphibious ships and the Pentagon helipad

• Two test aircraft destroyed

Flight Milestones• May 1965 - First vertical flight• December 1965 - First conventional

flight • Cancelled due to lack of interest by the

government

Tilt Wing

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Tilt Rotor• Aircraft tilts the rotor for

transition from vertical to horizontal flight

• Like Tilt Wing, the engines tilt together with the rotors

Tilt Rotor / Tilt Jet


Tilt Jet• Like Tilt Rotor but jet engine powered• The entire propulsion system rotates from vertical for

hover to horizontal for conventional flight

www.vstol.org

12. Bell XV-15• Powered by two 1,550 shp Lycoming

T53-LTC1K-4K turboshaft engines• Two 25 ft diameter three-bladed rotors• Engines and rotors were cross linked

and tilted through 90°• Low speed control by cyclic and

collective blade angle adjustments• Conducted extensive tests:

– Shipboard Landings (USS Tripoli)– Dive tests (397 mph)

• This aircraft was tested extensively in the wind tunnel

• Led to Bell Boeing V-22 and Bell 609

Flight Milestones• 3 May 1977 - First vertical flight• 24 July 1979 - First complete transition• By 1986 - Had completed 1,500

transitions and logged 530 flight hours

Tilt Rotor

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13. Bell Boeing V-22 Osprey• Powered by two wing tip mounted

Allison T406-AD-400 engines • The engines are cross-shafted and

rated at 6,140 shp for take-off• Two 38 ft three bladed rotors• A total of 523 aircraft will be built

for the Marine Corps, Navy and Air Force

• Can carry 24 troops or 864 cubic feet of cargo

• Normal take-off weight 47,500 lb• Combat range 600 miles • Maximum ferry range 2,400 miles• Maximum speed 400 mph• Only V/STOL transport aircraft in

production

Flight Milestones• 19 March 1989 - First flight• 14 September 1989 - First transition• By the end of 1996 it had over 1,100

hours of flight testing• 5 February 1997 - First “production

representative” aircraft flight

Tilt Rotor

19 March 1989 - First flight

www.vstol.org

14. Bell 65 Air Test Vehicle (ATV)• Assembled from parts of existing

commercial aircraft• Powered by two 1,000 lb Fairchild J-

44 missile turbojet engines mounted on each side of the aircraft

• Engines could be tilted from vertical to horizontal

• Hover control was provided by Turbomeca Palouste turbo-compressor reaction jets at the wing tips

• Had inadequate thrust to complete transition from vertical to horizontal flight

• Cancelled in favor of the Bell X-14 project

Flight Milestones• 16 November 1954 - First vertical flight• 1955 - First horizontal flight• 1955 - Program cancelled by Bell

Tilt Jet

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Deflected Slipstream

• The propeller slipstream is deflected 90° downward with trailing flaps which form a “bucket”

• The deflected propeller thrust is used for lift


www.vstol.org

15. Robertson VTOL• Powered by two supercharged

340 hp Lycoming GSO-480 engines

• Wing had a sliding flap system with a double-slotted full span trailing edge flap providing all control

• Flaps were retracted into low aspect ratio wing for horizontal flight

• All fuel and oil stored in wing tip tanks which acted as endplates

• Tanks capped the wing “buckets” theoretically improving efficiency

• Further aircraft development not pursued

Flight Milestones• October 1956 - Robertson Aircraft

Corporation is formed• 8 January 1957 - Aircraft makes only

tethered flight


www.vstol.org

16. Ryan 92 VZ-3 Vertiplane• Powered by a 1,000 shp Lycoming

T53-L-1 turboshaft engine• One metal three-bladed Harzell

propeller on each side• Propellers were ahead and below

wing so the produced slip-stream flowed directly into the bucket formed by extended double flaps and deflected downwards for lift

• Differential propeller pitch was used for roll control

• Engine exhaust at tail was used for pitch and yaw control until tail surfaces could be effective

• Engines failed to provide sufficient thrust to hover without a headwind

Flight Milestones• 21 January 1959 - First flight• February 1959 - Grounded by a flight

accident• February 1960 - NASA test flights• Continued flying until 1961 - Testing

low-speed V/STOL handling characteristics


www.vstol.org

17. Fairchild 224 VZ-5 Fledgling• Powered by one 1,024 shp General

Electric YT58-GE-2 turboshaft engine

• Four three bladed Harzell metal propellers

• Aircraft could rest on two main wheels and tail skid, providing 30° of inherent rotation to enhance the bucket’s effectiveness

• Small rotors at the top of T-tail controlled pitch during hover

• Aircraft never flew

Flight Milestones• Late 1959 - Tether tests conducted


www.vstol.org

Vectored Thrust

• The jet engine exhaust is vectored to create a vertical or horizontal motion

www.vstol.org

18. Bell X-14• Built from Beech T-34 fuselage and

tail, Bonanza wing• Powered by two ASV8 Viper engines• Used a planar array of diverter vanes

to vector the engine exhaust• Reaction control jets on wings and tail• Eventually was fitted with a digital

fly-by-wire control system• Lack of ejection seat limited hover

testing to very low and very high altitudes

• The discovery of the suckdown phenomenon led to lengthening of the landing gear

• Served as a V/STOL testbed until 1981

Flight Milestones• 17 February 1957 - First vertical flight• 24 May 1958 - First transition• 1960 - More powerful GE J85 engines

installed and transferred to NASA

Vectored Thrust

www.vstol.org

19. Hawker P.1127 Kestrel• P.1127 powered by one 11,000 lb

thrust Bristol Pegasus 2 engine• Bifurcated jetpipe and vectoring

front and rear nozzles• Control power was low which

combined with suck down resulted in high pilot work load

• Hot gas ingestion problem was overcome with a low forward speed in takeoff and landing

• A tripartite program involving the UK, US and Germany funded nine improved Kestrels with a 15,500 lb Pegasus 5 engine

• The Kestrel paved the way for the Harrier

Flight Milestones• 19 November 1960 - First vertical flight• 7 July 1962 - First conventional flight• 12 September 1962 - First double

transition• 1962 - Tripartite program initiated

Vectored Thrust

www.vstol.org

20. Yakovlev Yak-36 Freehand • Powered by two non-afterburning

Soyuz Tumanskiy/ Khatchaturov R27-300 turbojet engines (13,000 lb)

• Engines were fitted with louvered nozzles which were vectorable through 90° and exhausted at the center of gravity (c.g.)

• Engine bleed air was used for reaction control at the wingtips, tailcone and the tip of nose “probe”

• Retractable doors reduced hot gas reingestion

• Only capable of vertical take-offs and landings

• This technology demonstrator led to the Yak-38 Forger

Flight Milestones• 9 January 1963 - First vertical flight• 16 September 1963 - First transition to

horizontal flight• 7 July 1967 - First public display at the

Domodedovo Air Show

Vectored Thrust

www.vstol.org

21. British Aerospace / Boeing Harrier

• Follow-on to the Hawker Kestrel• Operated by the USMC, UK RAF

and RN, Spain, Italy, India and Thailand

• UK RAF version powered by 19,000 lb Pegasus Mk 101

• USMC AV-8A powered by the 21,500 lb Pegasus 11

• AV-8B Harrier II has a more powerful engine (23,800 lb), a larger composite supercritical wing and optimized Lift Improvement Devices (LIDs)

• The Harrier II has double the payload and range when making short takeoffs

• Only V/STOL aircraft in service

Flight Milestones• 31 August 1966 - First flight for production

designed aircraft• 1 April 1969 - Enters service with UK RAF• 1969 - USMC purchase first AV-8A• 1974 - McDonnell Douglas begins

development of AV-8B Harrier II• 1978 - First flight of the Sea Harrier

Vectored Thrust

www.vstol.org

22. Boeing X-32B• The X-32 is a concept demonstrator

for the Joint Strike Fighter (JSF) program

• Powered by a derivative of the Pratt & Whitney F119 engine with Rolls-Royce lift components

• In short take-off and landing mode the engine closes the vectorable cruise nozzle and opens two lift nozzles at the aircraft c.g.

• The X-32 has a chin inlet and blended delta wing

Flight Milestones• 1994 - ASTOVL contract awarded• 1995 - 94% scale model of the P&W

YF119 was tested• 1996 - Selection as JSF demonstrator • 2001 - First flight of prototype

Vectored Thrust

www.vstol.org

Tail Sitters

• Entire aircraft points straight up

• The entire thrust of propulsion system is converted directly to vertical lift

• Easy to take-off in vertical direction


• Considerably more difficult to land facing in the opposite direction of aircraft travel

www.vstol.org

23. Lockheed XFV-1• Powered by two 5,500 eshp Allison

YT40-A-14 engines• Two 16 ft counter-rotating three-

bladed Curtiss-Wright propellers with electric pitch control

• Hover control was by the same large aerodynamic surfaces used in level flight, as each was bathed in propeller slipstream

• The “X” shaped tail arrangement minimized downwash masking

• Control in hover was very weak, and the pilot had difficulty in determining sink, climb, and rotation from normal visual cues

• No vertical take-off or landings attempted

Flight Milestones• March 1954 - Aircraft fitted with

conventional landing gear and made first flight

• 27 conventional flights were made• Complete transitions completed above

1,000 ft

Tail Sitters

www.vstol.org

24. Convair XFY-1 Pogo• Similar to the Lockheed XFV-1• Powered by one Allison YT40-A-14

engine• Used two Curtiss-Wright counter-

rotating three blade propellers• Control in hover for the XFY-1

were the same as for conventional flight, but provided only limited control power

• The seat was inclined 45o toward the instrument panel for vertical flight

• Ventral fin below wing could be jettisoned for emergency horizontal landing

• The engine and control systems were considered inadequate

Flight Milestones• April 1954 - First tethered flight• 1 August 1954 - First free vertical flight• 2 November 1954 - First transition• November 1956 - Last flight

Tail Sitters

www.vstol.org

25. Ryan X-13 Vertijet• This aircraft had a short pole

ending in a hook under the nose• The hook was used to capture a

wire on a vertical trailer bed• The trailer could be lowered for

ground transport• Engine thrust was vectored to

provide pitch and yaw control in hover

• Roll control was provided by puffer jets at the wing tips

• The first prototype was fitted with conventional landing gear and made full transitions

• The Air Force did not continue development because of the lack of an operational requirement

Flight Milestones• 10 December 1955 - First prototype

makes horizontal flight• 11 April 1957 - Second prototype

makes vertical take off, transition, and vertical landing using the hook system

Tail Sitters

www.vstol.org

26. SNECMA C450 Coléoptère• Powered by a 7,700 lb Atar 101E

turbojet• Four small fins were mounted on

the 10.5 ft diameter annular wing• Hover control provided by tilting

vanes in the nozzle• In forward flight, the small fins

deflected the air for control• Two small nose strakes were

extended to facilitate a pitch up moment in transition to vertical flight

• The Coléoptère never achieved transition

• The program was cancelled because of an increased emphasis on air superiority and attack roles

Flight Milestones• 17 April 1959 - First tethered hover• 3 May 1959 - First untethered hover• 25 July 1959 - Aircraft falls into

oscillations about all three axis and crashes while attempting to transition from hover at 2,000 ft

Tail Sitters

www.vstol.org



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V/STOL Aircraftand PropulsionConcepts

Depicted here are the vari ous t ypes of Verti cal andShor t Tak e- Off and Landing (V/S TOL) ai rcraf t whichhave been t ested ov er the past 40 years . All wer ebuilt to be f lown, but on ly thr ee (shown in bol d) h aveled to oper ational aircr aft. I n f act , th e Harr ier is th eonly V/ STOL air craft in service tod ay.

The Joi nt Str ike F ighter con cep t dem onstrator s ( shown in blue) , ar e schedul ed to fly in 2000; one of these concepts wi ll serv e as the basis fo r d ev el opment of an air craft t o replace the Har rier .

ANSERA NOT-FOR-PROFIT PUBLIC SERVICERESEARCH INSTITUTE

ht tp://w ww. ans er.org

• Used two separate groups of power plants– One for hover– One for cruise

www.vstol.org

Lift + Cruise

• Used vertically-mounted lift engines for hover


– Optimized to produce a large amount of thrust for a short duration

– Used only for take-off and landing

www.vstol.org

27. Short SC.1• Four 2,130 lb Rolls-Royce RB.108

lift engines mounted on gimbals in the center fuselage

• One 2,130 lb Rolls-Royce RB.108 cruise engine in the rear of aircraft

• The hover engines were started by ground carts for take-off or by cruise engine bleed air in flight

• Bleed air from the four lift engines, tail and wing tip reaction jets were used for control at low speeds

• Experienced typical suck-down and hot-gas ingestion problems

• Pilot work load very high during landing

• High fuel consumption by lift engines

Flight Milestones• 2 April 1957 - First CTOL flight• 26 May 1958 - First tethered flight• 25 October 1958 - First vertical flight• 6 April 1960 - First transition• Flew until 1967

Lift & Cruise

www.vstol.org

28. Dassault Balzac V• Built by the French Dassault

company• Eight 2,130 lb Rolls-Royce RB.108

engines for vertical flight• One 4,850 lb Bristol Orpheus

engine for cruise• Lift engines were separated by

main landing gear to balance center of gravity

• Each engine lift pair shared an inlet door and exhaust door

• 50% scale (by weight) demonstrator for Mirage III-V

• During transition all the lift engine doors created high drag

• Resulted in two fatal accidents and was subsequently cancelled

Flight Milestones• 12 October 1962 - First tethered flight• 18 October 1962 - First free vertical flight• 1 March 1963 - First conventional flight

Lift & Cruise

www.vstol.org

29. Dassault Mirage III V• Built by the French Dassault

company • Eight 5,400 lb RB.162-31 lift

engines• One 18,250 lb P&W TF30 cruise

engine • Hover control was achieved

through control jets in nose, tail and wing tips

• Fastest V/STOL aircraft in the world, achieving Mach 2.04

• Large number of engines reduced significantly internal fuel capacity

• There was no room for any useful payload on this aircraft

Flight Milestones• 12 February 1965 - First vertical flight• March 1966 - First complete transition

to horizontal flight• 12 September 1966 - Achieves record

speed of Mach 2.04

Lift & Cruise

www.vstol.org



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Depicted her e ar e t he var ious types o f Verti cal andSh ort Take-Of f and Landin g (V/ STOL) aircr af t whi chhave been tested over the past 40 years. All wer ebui lt to be flo wn, but only t hree ( shown in bo ld) haveled to operatio nal air craft. I n fact, t he Har rier is t heonl y V/STOL aircraf t in servi ce t oday.

Th e Joint St rike Figh ter concept dem onstrator s (shown in bl ue), are schedu led to fly in 200 0; on e of these concepts wi ll serv e as the basis f or development of an air craft to r epl ace t he Harri er .

ANSERA NOT-FOR-PROFIT PUBLIC SERVICERESEARCH INSTIT UTEhttp: //w ww.a ns er.org

• Used main propulsion system for both hover and cruise

• An additional propulsion system was used for additional hover thrust

www.vstol.org

Lift Plus Lift/Cruise

• One set of engines for lift only• Additional set of engines for

both lift and cruise


www.vstol.org

30. EWR VJ101C• Produced by the German EWR

(Messerschmitt, Heinkel, and Bölkow)

• Powered by six 2750 lb Rolls-Royce/ MTU RB.145 turbojet engines

• Two engines mounted in tandem aft of cockpit

• Four engines in pairs in wingtip swiveling nacelles

• No reaction control system• First supersonic V/STOL aircraft• Suffered from high temperature and

erosion issues• Crashed due to significant power loss

from hot-gas ingestion• The follow-on, VJ101D, was very

complex and cancelled

Flight Milestones• 10 April 1963 - First vertical flight• 31 August 1963 - First horizontal

takeoff• 20 September 1963 - First double

transition• July 1964 - Aircraft breaks the sound

barrier in a shallow dive without afterburner

Lift & Lift/Cruise

www.vstol.org

31. Dornier Do 31• Used two 15,500 lb Bristol

Pegasus 5-2 engines for cruise and hover with 30° forward and 80° back vectored thrust

• Used eight 4,400 lb Rolls-Royce RB.162-4D engines for hover with 15° forward and backward vectoring for take-off and landing

• Roll and yaw control was achieved with differential vectoring and thrust levels

• Pitch control was achieved with a puffer jet in the tail

• Engine pod high drag and weight reduced the useful payload and range

Flight Milestones• 10 February 1967 - First conventional flight• 22 November 1967 - First vertical flight• 16 December 1967 - First transition from

vertical• 22 December 1967 - First transition to

vertical• April 1970 - Project was cancelled

Lift & Lift/Cruise

www.vstol.org

32. Lockheed XV-4B Hummingbird II• Was a modified Lockheed XV-4A

Hummingbird• Four 3,000 lb General Electric J85-

GE-19 lift engines• Two 3,000 lb GE J85-GE-19 for

lift/cruise flight• During hover, large diverter valves

directed the cruise engine exhaust to a nozzle between the lift engines for additional vertical thrust

• In transition, one lift/cruise engine was diverted to forward flight

• Pitch and yaw jets at the nose and tail provided hover control

• The Hummingbird II had a fly-by-wire autostabilization system

• The aircraft never achieved hover

Flight Milestones• 1964 - XV-4A cancelled and XV-4B

program initiated• 4 June 1968 - XV-4B is rolled out• 14 March 1969 - Aircraft crashed

during a conventional flight

Lift & Lift/Cruise

www.vstol.org

33. VFW VAK 191B• Two 6,000 lb Rolls-Royce/MTU

RB.162-81 lift engines one mounted directly behind the cockpit and one aft of the wing

• One 16,163 lb Rolls-Royce RB.193-12 vectored thrust turbofan mounted between the lift engines

• The RB.193-12 was a smaller version of the Bristol Pegasus engine used with the Kestrel/Harrier

• The program was intended to develop a high-speed V/STOL strike aircraft

• Was cancelled due to a change in NATO strategy

• Small wing gave it very poor transition characteristics

Flight Milestones• 10 September 1971 - First untethered

hovering flight• 26 October 1972 - First transition

achieved

Lift & Lift/Cruise

www.vstol.org

34. Yakovlev Yak-38 Forger• Two in-line 6,722 lb Rybinsk

RD-36-35FVR immediately behind cockpit

• One 13,444 lb Soyuz Tumanskiy/ Khatchaturov R-27V-300 turbojet was mounted in the fuselage center exhausted through two vectoring hydraulically actuated nozzles

• One nozzle was situated on each side of the fuselage just aft of the wing trailing edge

• Primary roles were fleet defense, reconnaissance and anti-ship strike but never saw combat

• Deployed on the Kiev-class aircraft carrier

• A total of 231 aircraft were built

Flight Milestones• Jan 1972 - First prototype flight• July 1976 - First deployment of

Yak-38 equipped Kiev • 1988 - End of production line• 1992-1993 - Forger is removed

from front line service

Lift & Lift/Cruise

www.vstol.org

35. Yakovlev Yak-141 Freestyle• The supersonic Freestyle was optimized

for air defense with a secondary attack capability

• A dozen FAI-recognized Class H.III records for V/STOL altitudes and time to altitude with loads were set by the Freestyle

• Maximum speed achieved was 1.7 Mach• Maneuverability was claimed to be

“almost as good as the MiG-29”• Development was stopped due to

shrinking Soviet military budget• Yakovlev funded the development

hoping to attract foreign investors but was unable to market the design

Flight Milestones• 9 March 1987 - First conventional flight• 29 December 1989 - First hover• April 1991 - Yak-141 sets V/STOL records• August 1991 - Government funding ended• October 1991 - Second prototype crashed

Lift & Lift/Cruise

www.vstol.org

Tip Jets

• A compound autogyro:– Transmits full power to the rotor for

vertical flight– Transfers power to a horizontal

propulsion device for forward flight and off-loads the rotor

• Wings provide lift in forward flight to allow the aircraft to fly faster than a conventional helicopter

• Tip Jet aircraft pump fuel and compressed air to small burner chambers at the rotor tips– This combustion generates thrust which turns rotor

www.vstol.org

36. McDonnell XV-1• Powered by one 550 hp Continental

R-975-19 nine cylinder radial piston engine

• Two air compressors powered by the engine drove the lift rotors

• 31 ft three-bladed rotors for vertical lift• One 6 ft diameter two-bladed propeller

for forward flight• Yaw control was achieved through a

small rotor at the end of each tail boom • Exceeded contemporary rotorcraft speed

records by attaining 200 mph• Tip jet noise was very loud• Tip jet flash at night made it an easier

target

Flight Milestones• 1954 - First tether test• 11 February 1954 - First free flight• 29 April 1954 - First transition to

horizontal flight• 10 October 1955 - 200 mph speed

record is set• 1957 - The program is cancelled

Tip Jets

www.vstol.org

37. Fairey Rotodyne• Powered by two 2,800 shp Napier

Eland 3 turbine engines• The 60 ft diameter four-bladed

rotor was powered by tip jets in vertical flight and autorotated in cruise, providing half the lift

• Two four-bladed tractor propellers provided forward thrust

• Pitch and roll were controlled by cyclic rotor pitch

• Yaw was controlled by differential propeller pitch

• Aerodynamic surfaces augmented control in forward flight

• Tip jet noise was very unpleasant• Aircraft cancelled when Westland

took over Fairey

Flight Milestones• 6 November 1957 - First vertical flight• April 1958 - First transitions are begun• October 1958 - Problem with jet relights

at altitude is solved• 1962 program fizzles out

Tip Jets

www.vstol.org



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Depicted h er e ar e the vario us ty pes of Vertical andSh ort Take-O ff an d Lan ding ( V/STOL) ai rcraf t whichhave been tested over the past 40 years. All wer ebui lt to be fl own, bu t only thr ee (shown in bol d) h av eled to operati onal ai rcraf t. In fact, the Harr ier is th eonl y V/STOL aircr aft in ser vice today.

Th e Joint S trik e F ighter concept dem onstrator s (show n i n blue), ar e scheduled t o fly in 20 00; one of t hese concepts wil l serve as th e basi s for develo pment of an air craft to r eplace the Har rier .

ANSERA NOT -FOR-PROFIT PUBLIC SERVICERESEARCH INST ITUTE

ht tp://w ww. anser.org

• Uses power plant(s) to drive an auxiliary device– Ejector augmentors

– Lift fans

– Propeller

• These devices provide additional

thrust for hover or cruise

• Wings provide lift in forward flight

www.vstol.org

Ejector

• Ejects high pressure engine efflux into a channel (augmentor) causing additional cooler ambient air to accelerate through channel and mix with engine exhaust


• At the augmentor exit the combined flow produces more thrust than input engine alone

www.vstol.org

38. Lockheed XV-4A Hummingbird

• Powered by two 3,300 lb P&W JT12 turbojet engines mounted on either side of the fuselage

• The thrust was diverted into augmentor ejectors for vertical flight, take-off and landing

• Engines fed interleaved ejectors in case of engine failure

• In transition one engine was diverted from ejectors to providing forward thrust until wing-born lift was sufficient

• Actual vertical thrust after installation losses was 7,500 lb for a 1.04 thrust to weight ratio

Flight Milestones• 7 July 1962 - First conventional flight• 30 November 1962 - First hover• 24 May 1963 - First untethered hover• 8 November 1963 - First transition

completed

Ejector

www.vstol.org

39. Rockwell XFV-12A• Powered by one modified 30,000 lb

(in afterburner) P&W F401 engine• For vertical lift engine exhaust was

diverted through ducts to ejector nozzles in the wings and canards

• Pitch and roll were controlled by differential variation of the four ejectors from fore to aft and left to right

• Yaw was controlled by differential ejector vectoring

• Expected max speed was over Mach 2• Lab tests indicated augmentation of

55% was possible but only 12.5% (average) was demonstrated

• The program was discontinued due to cost overruns and waning Navy V/STOL interest

Flight Milestones• 1974 - Engine rig testing begins• July 1977 - Aircraft ground testing begins• 1978 - Suspended tether trials performed• 1981 - Program is cancelled• July 1977 - Ground testing begins

Ejector

www.vstol.org

Fan

• A horizontal oriented ducted propeller or fan is buried in aircraft wing or fuselage

• The propeller / fan is located close to the center of gravity (c.g.)


• Engine power can be redirected to propeller / fan to provide vertical thrust for hover

• The conventional wing provides thrust for horizontal flight

www.vstol.org

40. Vanguard Omniplane• Powered by one 265 hp Lycoming

O-540-A1A six cylinder piston engine (later a 860 hp Lycoming YT53-L-1)

• One 6 ft diameter three-bladed propeller was mounted in each wing for vertical flight

• One 5 ft diameter propeller in the tail provided forward thrust

• Covers above the rotors and louvers below sealed the wing for lift

• Pitch and yaw was controlled by elevator and rudder surfaces behind the rear propeller

• Roll was controlled in hover by differential blade pitch

• Aircraft damaged and program ended

Flight Milestones• August 1959 - Ground testing of 2C• 1962 - Omniplane is modified with

larger engine and a third lift propeller in nose, redesigned 2D

• 1962 - Omniplane 2D completes hover tests

• 1962 - 2D version damaged and development discontinued

Fan

www.vstol.org

41. GE-Ryan XV-5A Vertifan• Powered by two 2,650 lb General

Electric J85-GE-5 turbojets• One 5 ft diameter fan in each wing

for vertical lift• Wing fans rotated in opposite

direction and covered by doors• Pitch control provided by one small

fan in front of cockpit• Roll control achieved by the wing

fans • Yaw control was provided by

louvered vanes under the wing fans that could vector the thrust

• Had slow control response and a narrow transition corridor

• Lift system occupied a large volume and weight

Flight Milestones• 25 May 1964 - First flight• April 1965 - First prototype crashed• June 1964 - First vertical flight• November 1964 - First transition• October 1966 - Second prototype

crashed

Fan

www.vstol.org

42. Lockheed Martin X-35• Joint Strike Fighter (JSF) Lockheed

Martin concept demonstrator• Powered by a derivative of the

P&W F119 engine• For vertical flight the P&W drives a

shaft which turns an Allison lift fan ahead of the c.g.

• Rear lift force and yaw control is provided by a swiveling exhaust nozzle similar to the Yak-141

• Roll control is provided by two roll nozzles using ducted fan bypass air

• An 86% scale model powered by a P&W F100 was tested for nearly 200 hrs including in Ames wind tunnel

Flight Milestones• 1993 - ASTOVL contract awarded• 1995-1996 - Large scale model is tested • 1996 - Selection as JSF demonstrator• 2000 - Planned first flight of prototype• 2001 - JSF source selection and

possible development of operational version

Fan

www.vstol.org

Rotor

• Designed for missions where the aircraft needs to spend a large amount of time in hover– Rotor is the most efficient lifting

device for these missions


• Very difficult for rotor to propel the aircraft forward andprovide lift at high velocity

• To increase maximum velocity a variety of methods have been used to add propellers and wings to rotor aircraft forming compound helicopters

www.vstol.org

43. Kamov Ka-22 Vintokryl ‘Hoop’• Powered by one 6,500 shp

Soloviev D-25VK turboshaft engine on each wingtip

• Each engine had one four-bladed rotor for vertical flight and one four-bladed propeller for cruise

• Could transport vehicles and other cargo, up to 36,400 lb or 80 seats

• Set a Class E.II speed record of 221.4 mph over a 15.25 km course

• Lifted record payload of 46,343 lb to a height of 6,562 ft

• Held several other payload to altitude records

• Abandoned after a crash

Flight Milestones• 20 April 1960 - Flight testing starts• 7 October 1961 - Sets Class E.II speed

record• 24 November 1961 - Sets payload

record• 1964 - Ka-22 abandoned

Rotor

www.vstol.org

44. Piasecki 16H-1 Pathfinder• Privately developed by Piasecki• Powered by a 550 hp Pratt & Whitney

PT6B-2 turboshaft engine• One 41 ft fully articulated three-bladed

rotor• One 5.5 ft three-bladed ducted

propeller in the tail for forward thrust• Anti-torque control by four vertical

vanes in duct• Used its wings and pusher propeller to

off-load the rotor and increase the max speed to 148 kts

• 16H9-1A Pathfinder II had a 1,250 shp T58 turboshaft engine

• 16H-1C engine upgraded to a 1,500 shp T58-GE-5

• Civil proposals were unsuccessful

Flight Milestones• 21 February 1962 - First flight• May 1964 - Piasecki contracted to test

16H-1A Pathfinder II• 15 November 1966 - 16H-1A begins

flight tests• May 1966 - Research concluded after

40 flight hours

Rotor

www.vstol.org

45. Lockheed AH-56 Cheyenne• Powered by one 4,435 shp GE

T64-GE-16 turboshaft engine• Hover by one rigid 50 ft four-

bladed rotor• One 10 ft three-bladed pusher

propeller• One four-bladed anti-torque rotor• Highly agile and capable aircraft• Original production order for 375

AH-56s approved in 1968• Ten aircraft built• Maximum speed reached was 277

mph• Project cancelled in 1972 due to

defense budget cutbacks

Flight Milestones• 21 September 1967 - First flight• 12 March 1969 - Third prototype

crashes killing the pilot• 1968 - Production order approved• 1972 - Project cancelled

Rotor

www.vstol.org

Lessons Learned

• Lots of different concepts were tried -- some more seriously than others.• Engine/mechanical system reliability is extremely important for powered

lift concepts.• Propulsion system sizing is very important: too small and the aircraft

can't hover, too large and it may be too heavy and/or oversized for cruise. • The propulsion system should not take up too much volume, or there is

no room for fuel or payload.• V/STOL development programs (like all programs) are often canceled

for political reasons. They must also be fully funded and not tried on a shoestring budget.

• Pilot workload needs to be manageable, especially during vertical landing.

• The control system needs to be sufficient (speed and authority) for hover.

www.vstol.org

The Future of V/STOL

Bell Boeing V-22 Bell Agusta 609

Lockheed Martin X-35

Joint Strike Fighter

Tilt Rotor

www.vstol.org

On the Vertical HorizonCarterCopter Powered Autogyro

Boeing Canard Rotor/Wing “Dragonfly”

Boeing Tilt-wing Advanced Theater Transport (ATT)

Bell Quad Tiltrotor (QTR)

Duncan Tilt-propeller “Xantus”

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