Configuration Design Configuration Design part 2part 2

Wing Wing PlacementPlacement

HIGH WING:HIGH WING: PROSPROS1. Quick loading and unloading.1. Quick loading and unloading. C-5, C-17C-5, C-17 Loading and unloading through nose / tail doors: important Loading and unloading through nose / tail doors: important

to have low floor level.to have low floor level. Low-wing ac: main deck floor is 16-17 ft (5 m) above the Low-wing ac: main deck floor is 16-17 ft (5 m) above the

apron because the wing carry-through structure passes apron because the wing carry-through structure passes below the floor. Necessary to have special loading and below the floor. Necessary to have special loading and boarding equipment.boarding equipment.

2. Best for braced-wing monoplanes.2. Best for braced-wing monoplanes.CessnaCessna Struts cause little interference when attached to the lower Struts cause little interference when attached to the lower

side of the wing.side of the wing. Lighter struts because they are stressed in tension.Lighter struts because they are stressed in tension.

3. The wing is generally lighter.3. The wing is generally lighter.

C-17C-17

Cessna 152Cessna 152

HIGH WING:HIGH WING: PROSPROS4. The nose-wheel gear is shorter and lighter.4. The nose-wheel gear is shorter and lighter.5. Best for STOL5. Best for STOL QSRAQSRA Close proximity of the wing to the ground during TO and Close proximity of the wing to the ground during TO and

LNG may cause pronounced undesirable ground effects.LNG may cause pronounced undesirable ground effects. Required ground clearance for large, fully deflected TE flaps Required ground clearance for large, fully deflected TE flaps

and large props would entail a very tall and heavy LG in a and large props would entail a very tall and heavy LG in a low wing configuration.low wing configuration.

6. Safer.6. Safer. Damage and fire risk is limited during a forced LNG.Damage and fire risk is limited during a forced LNG.

7. Less Ground Effect in CTOL7. Less Ground Effect in CTOL Shorts 330Shorts 330 Smaller LNG distance.Smaller LNG distance.

8. Best for amphibians8. Best for amphibians Boeing 314-Boeing 314-AA

Keeps engines away from HKeeps engines away from H22O.O.

Quiet Short Research AircraftQuiet Short Research Aircraft

Shorts 330Shorts 330

Boeing 314-ABoeing 314-A

HIGH WING:HIGH WING: CONSCONS1. Problem w. the retraction of the main1. Problem w. the retraction of the main LG.LG. In small, high-wing propeller ac, main LG can be retracted In small, high-wing propeller ac, main LG can be retracted

into engine nacelles (into engine nacelles (Fokker F-27Fokker F-27) or in tail booms ) or in tail booms ((Hawker Siddeley ArgosyHawker Siddeley Argosy). In large ac, however, this ). In large ac, however, this would make the LG too tall and heavy.would make the LG too tall and heavy.

A solution for large ac: fuselage-mounted LG.A solution for large ac: fuselage-mounted LG. Problem 1:Problem 1: strengthening of the fuselage structure strengthening of the fuselage structure

required for the transmission of the LNG impact results in required for the transmission of the LNG impact results in W increase. W increase.

Problem 2:Problem 2: with a fuselage mounted main LG the track with a fuselage mounted main LG the track may not be sufficiently wide.may not be sufficiently wide.

2. No ground effect in CTOL.2. No ground effect in CTOL. Increased TO distance.Increased TO distance.

Fokker F-27Fokker F-27

Hawker Siddeley HS.660 ArgosyHawker Siddeley HS.660 Argosy

HIGH WING:HIGH WING: CONSCONS

3. No room for underfloor cargo.3. No room for underfloor cargo. Fuselage section below the floor is flattened to reduce LG Fuselage section below the floor is flattened to reduce LG

height + keep the floor low (4-4.5 ft = 1.2-1.4 m).height + keep the floor low (4-4.5 ft = 1.2-1.4 m). Solution: longer cargo hold in cabin.Solution: longer cargo hold in cabin. Problem 1:Problem 1: longer fuselage. longer fuselage. Problem 2:Problem 2: large cg travel. large cg travel.

4. Unsafe4. Unsafe Fuselage will sink when ac is forced down on water. Fuselage will sink when ac is forced down on water.

Provisions must be made for escape through the cabin roof.Provisions must be made for escape through the cabin roof.

5. Not good for highly maneuverable ac.5. Not good for highly maneuverable ac. Too stable in roll.Too stable in roll.

HIGH WING:HIGH WING: CONSCONS

6. ~ 20% more S6. ~ 20% more SVV than a low-wing than a low-wing

configuration.configuration.

7. OEW is generally higher.7. OEW is generally higher.

8. Structural design is generally more 8. Structural design is generally more complicated.complicated.

MID WING:MID WING: PROSPROS

1.1. Min D in high-speed flight.Min D in high-speed flight. (fighters, trainers) (fighters, trainers) Surfaces at wing / fuselage junction meet at 90Surfaces at wing / fuselage junction meet at 9000 angles; angles;

interference between BLs at low interference between BLs at low is minimized. is minimized. Fuselage section at the location where the wing is Fuselage section at the location where the wing is

mounted is roughly cylindrical; divergence of airflow mounted is roughly cylindrical; divergence of airflow over wing root is minimized.over wing root is minimized.

2.2. Best maneuverability.Best maneuverability.3.3. Wing can be continuous through the Wing can be continuous through the

fuselagefuselage transfer of loads from the wing can take place via transfer of loads from the wing can take place via

almost solid “bulkheads”, to which each wing-half is almost solid “bulkheads”, to which each wing-half is attached.attached.

F-18 Hornet & T-37F-18 Hornet & T-37

MID WING:MID WING: CONSCONS

1.1. Reduced internal useful fuselage volume.Reduced internal useful fuselage volume. That is the reason why mid-wing configurations are That is the reason why mid-wing configurations are

not adopted for transports.not adopted for transports.

LOW WING:LOW WING: PROSPROS

1.1. Efficient use of fuselage under-floor space.Efficient use of fuselage under-floor space.

2.2. Large tail angle allows for optimum rotation during Large tail angle allows for optimum rotation during TOTO (especially for stretched versions). (especially for stretched versions).

3.3. Easy retraction of main LG between wing spars.Easy retraction of main LG between wing spars.

4.4. Safer.Safer. A low wing and possibly the engines attached to it form a large A low wing and possibly the engines attached to it form a large

energy absorption mass during a forced LND.energy absorption mass during a forced LND.

5.5. Favorable ground effects.Favorable ground effects. Decreased TO distance.Decreased TO distance. AC lands itself; little or no elevator movement required to flare out AC lands itself; little or no elevator movement required to flare out

because L increase results in nose-up pitching M.because L increase results in nose-up pitching M.

6.6. Better maneuverability than a high wing.Better maneuverability than a high wing.

LOW WING:LOW WING: CONSCONS

1.1. Unsafe.Unsafe. Potential fire hazard during forced LND when wing Potential fire hazard during forced LND when wing

and engines hit the ground.and engines hit the ground.

2.2. Unfavorable ground effects.Unfavorable ground effects. AC floats during LND; longer LND distance.AC floats during LND; longer LND distance.

3.3. Greater elevator deflection required for Greater elevator deflection required for TO rotation and LND flare out.TO rotation and LND flare out.

Decreased downwash on the tail results in nose Decreased downwash on the tail results in nose down pitching M.down pitching M.

4.4. Longer LGLonger LG especially on swept back wings, to especially on swept back wings, to provide tip clearance during TO rotation.provide tip clearance during TO rotation.