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square foot of its area. This gives a thrust increase for a particular blade pitch angle, or, alternatively, the power required for a thrust is reduced. For an overloaded helicopter that can only hover IGE it may be possible to climb away from the ground by translating to forward flight first while in ground effect. The ground-effect benefit disappears rapidly with speed but the induced power decreases rapidly as well to allow a safe climb. Some early underpowered helicopters could only hover close to the ground. Ground effect is at its maximum over a firm, smooth surface.
154:
occurs when an aircraft has two or more lift jets. The jets strike the ground and spread out. Where they meet under the fuselage they mix and can only move upwards striking the underside of the fuselage. How well their upward momentum is diverted sideways or downward determines the lift. Fountain flow follows a curved fuselage underbody and retains some momentum in an upward direction so less than full fountain lift is captured unless lift improvement devices are fitted. HGI reduces engine thrust because the air entering the engine is hotter and less dense than cold air.
237:
189:
150:
a VTOL aircraft hovers IGE depends on suckdown on the air frame, fountain impingement on the underside of the fuselage and HGI into the engine causing inlet temperature rise (ITR). Suckdown works against the engine lift as a downward force on the airframe. Fountain flow works with the engine lift jets as an upwards force. The severity of the HGI problem becomes clear when the level of ITR is converted into engine thrust loss, three to four percent per 12.222 °c inlet temperature rise.
65:, ground effect results in less drag on the rotor during hovering close to the ground. At high weights this sometimes allows the rotorcraft to lift off while stationary in ground effect but does not allow it to transition to flight out of ground effect. Helicopter pilots are provided with performance charts which show the limitations for hovering their helicopter in ground effect (IGE) and out of ground effect (OGE). The charts show the added lift benefit produced by ground effect.
201:
175:
retroactively fitted to the P.1127 improved flow and increased pressure under the belly in low altitude hovering. Gun pods fitted in the same position on the production
Harrier GR.1/GR.3 and the AV-8A Harrier did the same thing. Further lift improvement devices (LIDS) were developed for the AV-8B and
153:
Suckdown is the result of entrainment of air around aircraft by lift jets when hovering. It also occurs in free air (OGE) causing loss of lift by reducing pressures on the underside of the fuselage and wings. Enhanced entrainment occurs when close to the ground giving higher lift loss. Fountain lift
149:
There are two effects inherent to VTOL aircraft operating at zero and low speeds in ground effect, suckdown and fountain lift. A third, hot gas ingestion, may also apply to fixed-wing aircraft on the ground in windy conditions or during thrust reverser operation. How well, in terms of weight lifted,
108:
A wing generates lift by deflecting the oncoming airmass (relative wind) downward. The deflected or "turned" flow of air creates a resultant force on the wing in the opposite direction (Newton's 3rd law). The resultant force is identified as lift. Flying close to a surface increases air pressure on
140:
When a hovering rotor is near the ground the downward flow of air through the rotor is reduced to zero at the ground. This condition is transferred up to the disc through pressure changes in the wake which decreases the inflow to the rotor for a given disc loading, which is rotor thrust for each
252:
The stalling angle of attack is less in ground effect, by approximately 2–4 degrees, than in free air. When the flow separates there is a large increase in drag. If the aircraft overrotates on take-off at too low a speed the increased drag can prevent the aircraft from leaving the ground. Two
781:"The NTSB’s John O’Callaghan, a national resource specialist in aircraft performance, noted that all aircraft stall at approximately 2-4 deg. lower AOA with the wheels on the ground." (from NTSB Accident Report concerning loss of a swept wing business-class jet airplane in April 2011)
176:
Harrier II. To box in the belly region where the lift-enhancing fountains strike the aircraft, strakes were added to the underside of the gun pods and a hinged dam could be lowered to block the gap between the front ends of the strakes. This gave a 1200 lb lift gain.
868:
From NTSB Accident Report: Flight test reports noted "post stall roll-off is abrupt and will saturate lateral control power." The catastrophic unrecoverable roll of the aircraft in the
Roswell accident was due in part to the absence of warning before the stall in ground
109:
the lower wing surface, nicknamed the "ram" or "cushion" effect, and thereby improves the aircraft lift-to-drag ratio. The lower/nearer the wing is to the ground, the more pronounced the ground effect becomes. While in the ground effect, the wing requires a lower
164:, built to research early VTOL technology, was unable to hover until suckdown effects were reduced by raising the aircraft with longer landing gear legs. It also had to operate from an elevated platform of perforated steel to reduce HGI. The
261:
business jet the test aircraft rotated to an angle beyond the predicted IGE stalling angle. The over-rotation caused one wing-tip to stall and an uncommanded roll, which overpowered the lateral controls, leading to loss of the aircraft.
212:
113:
to produce the same amount of lift. In wind tunnel tests, in which the angle of attack and airspeed remain constant, an increase in the lift coefficient ensues, which accounts for the "floating" effect. Ground effect also alters
276:
A few vehicles have been designed to explore the performance advantages of flying in ground effect, mainly over water. The operational disadvantages of flying very close to the surface have discouraged widespread applications.
782:
224:
72:(VTOL) aircraft, ground effect when hovering can cause suckdown and fountain lift on the airframe and loss in hovering thrust if the engine sucks in its own exhaust gas, which is known as hot gas ingestion (HGI).
374:
128:
aircraft. Due to the change in up-wash, down-wash, and wingtip vortices, there may be errors in the airspeed system while in ground effect due to changes in the local pressure at the
236:
168:
VTOL research aircraft only ever operated vertically from a grid which allowed engine exhaust to be channeled away from the aircraft to avoid suckdown and HGI effects.
188:
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overran the end of the runway after overrotating. Loss of control may occur if one wing tip stalls in ground effect. During certification testing of the
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HANDBOOKS, OPERATIONAL READINESS, MISSION PROFILES, PERFORMANCE (ENGINEERING), PROPULSION SYSTEMS, AERODYNAMICS, STRUCTURAL ENGINEERING
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weapons-bay inboard doors on the F-35B open to capture fountain flow created by the engine and fan lift jets and counter suckdown IGE.
1001:
420:"An evaluation of the historical issues associated with achieving non-helicopter V/STOL capability and the search for the flying car"
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Early VTOL experimental aircraft operated from open grids to channel away the engine exhaust and prevent thrust loss from HGI.
1013:
849:"Crash During Experimental Test Flight Gulfstream Aerospace Corporation GVI (G650), N652GD Roswell, New Mexico April 2, 2011"
1019:
721:
Addendum to AGARD report no. 710, Special Course on V/STOL Aerodynamics, an assessment of
European jet lift aircraft
678:
Ameel, Frederick Donald (1979). "Application of
Powered High Lift Systems to STOL Aircraft Design". p. 14.
647:
Proceedings of the 1985 NASA Ames
Research Center's Ground-Effects Workshop (NASA Conference Publication 2462)
230:
Harrier GR9 showing the lift improvement devices, large ventral strakes and a retractable dam behind nosewheel
129:
834:
615:
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54:. The pilot can then fly just above the runway while the aircraft accelerates in ground effect until a safe
848:
1010:
Tongji
University Scientists in Shanghai announce design of a new vehicle, inventorspot.com, 14 July 2007
118:
versus velocity, where reduced induced drag requires less thrust in order to maintain the same velocity.
1043:
616:
AN ANALYSIS OF CORRELATING PARAMETERS RELATING TO HOT-GAS INGESTION CHARACTERISTICS OF JET VTOL AIRCRAFT
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Underside view of the first prototype P.1127 showing small ventral strakes to increase fountain lift
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on the aircraft. This is caused primarily by the ground or water obstructing the creation of
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799:"ASN Aircraft accident de Havilland DH-106 Comet 1A CF-CUN Karachi-Mauripur RAF Station"
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MODEL TESTS OF CONCEPTS TO REDUCE HOT GAS INGESTION IN VTOL LIFT ENGINES(NASA CR-1863)
1037:
683:
572:
94:
85:
When an aircraft flies at or below approximately half the length of the aircraft's
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301:
878:
Understanding
Aerodynamics - Arguing From The Real Physics, Doug McLean 2013,
296:
62:
50:, ground effect can cause the aircraft to "float" while below the recommended
515:
480:"Lift from Flow Turning". NASA Glenn Research Center. Retrieved July 7, 2009.
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F-35B showing weapon's bay inboard doors open to capture rising fountain flow
161:
125:
419:
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941:(Federal Aviation Administration). New York: Skyhorse Publishing, 2007.
994:
Aeronautical and
Maritime Research Laboratory, Australian Government. (
382:(2 ed.). American Institute of Aeronautics and Astronautics, Inc.
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571:. Federal Aviation Administration. 2000. pp. 3–4. Archived from
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RAMESH TAAL, HOSUR, VIC. Australia: Aviation Theory Centre, 2005.
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Bell X-14 showing lengthened landing gear legs to reduce suckdown
69:
43:
27:
Increased aircraft lift generated when close to fixed surface
835:"Reprise: Night of the Comet | Flight Safety Australia"
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above the ground or water there occurs an often-noticeable
815:
Aerodynamic Design Of
Transport Aircraft, Ed Obert 2009,
46:
generate when they are close to a fixed surface. During
764:
Harrier Modern Combat
Aircraft 13, Bill Gunston1981,
905:. Hoboken, New Jersey: John Wiley & Sons, Inc.
924:. Ottawa, Ontario, Canada: Aviation Publications.
1020:Numerical Analysis of Airfoil in Ground Proximity
545:Basic Helicopter Aerodynamics, J. Seddon 1990,
939:Pilot's Encyclopedia of Aeronautical Knowledge
724:. AGARD report; no. 710, addendum. p. 4.
490:
488:
486:
469:Pilot's Encyclopedia of Aeronautical Knowledge
1030:, 2, pp. 425–36, Warsaw 2007. ptmts.org.
518:, Defense Technical Information Center (1974)
8:
1024:Journal of Theoretical and Applied Mechanics
206:Dassault Mirage IIIV hovering over open grid
973:M. Halloran; S. O'Meara (February 1999).
984:Centre for Aerospace Design Technology,
362:. Federal Aviation Administration. 2020.
124:are more affected by ground effect than
986:Royal Melbourne Institute of Technology
967:Ask Us – Ground Effect and WIG Vehicles
318:
184:
747:
737:
700:
689:
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439:
428:
376:Aircraft Design: A Conceptual Approach
1002:Wing in Ground Effect and helicopters
506:Flight theory and aerodynamics, p. 70
325:
7:
975:"Wing in Ground Effect Craft Review"
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351:"Chapter 7 - Helicopter Performance"
337:
833:Staff writers (October 25, 2019).
25:
418:Saeed, B.; Gratton, G.B. (2010).
180:Lockheed Martin F-35 Lightning II
457:Aerodynamics for Naval Aviators.
235:
223:
211:
199:
187:
1008:Plane Can Fly Inches Over Water
784:Thin Margins in Wintry Takeoffs
535:. April 12, 2016. pp. 2–6.
903:Flight Theory and Aerodynamics
660:The X-Planes, Jay Miller1988,
1:
988:– via Abbott Aerospace.
963:. SE-Technology ('dead' site)
901:Dole, Charles Edward (2000).
529:"Aerodynamics of ROTOR CRAFT"
70:vertical take-off and landing
990:DSTO-GD-0201. Sponsored by
614:Krishnamoorthy, V. (1971).
248:Wing stall in ground effect
1060:
621:(Report). NASA. p. 8.
603:(Report). Nasa. p. 4.
565:Rotor raft Flying Handbook
373:Raymer, Daniel P. (1992).
359:Helicopter Flying Handbook
269:
68:For fan- and jet-powered
18:Ground effect in aircraft
644:Mitchell, Kerry (1987).
596:Hall, Gordon R. (1971).
961:Engineering explanation
718:Williams, R.S. (1985).
922:Pilot Flight Maneuvers
920:Gleim, Irving (1982).
786:AWST, 24 December 2018
438:Cite journal requires
1014:Ground-effect gliding
272:Ground-effect vehicle
266:Ground-effect vehicle
634:, pp. 551, 552.
292:Ground effect (cars)
166:Dassault Mirage IIIV
93:The result is lower
1004:. dynamicflight.com
803:aviation-safety.net
533:ABBOTTAEROSPACE.COM
471:2007, pp. 3-7, 3-8.
255:de Havilland Comets
122:Low winged aircraft
81:Fixed-wing aircraft
42:that an aircraft's
32:fixed-wing aircraft
969:. Aerospaceweb.org
650:. Nasa. p. 4.
1016:. hanggliding.org
912:978-0-471-37006-2
884:978 1 119 96751 4
821:978 1 58603 970 7
699:Missing or empty
105:behind the wing.
101:and interrupting
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632:Raymer 1992
302:Vortex ring
56:climb speed
52:climb speed
996:WebArchive
980:. The Sir
978:(PDF-9 MB)
701:|url=
582:2021-11-03
403:2019-12-26
326:Gleim 1982
308:References
297:Hovercraft
136:Rotorcraft
63:rotorcraft
750:ignored (
740:cite book
684:107781224
495:Dole 2000
338:Dole 2000
162:Bell X-14
126:high wing
1038:Category
692:cite web
281:See also
171:Ventral
103:downwash
87:wingspan
886:, p.401
869:effect.
668:, p.108
173:strakes
48:takeoff
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313:Notes
44:wings
992:DSTO
943:ISBN
926:ISBN
907:ISBN
880:ISBN
817:ISBN
766:ISBN
752:help
726:ISBN
705:help
662:ISBN
547:ISBN
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