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Configuration Design part 2

Configuration Design part 2. Wing Placement. HIGH WING: PROS. 1. Quick loading and unloading. C-5, C-17 Loading and unloading through nose / tail doors: important to have low floor level.

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Configuration Design part 2

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  1. Configuration Design part 2 Wing Placement

  2. HIGH WING: PROS 1. Quick loading and unloading.C-5, C-17 • Loading and unloading through nose / tail doors: important to have low floor level. • Low-wing ac: main deck floor is 16-17 ft (5 m) above the apron because the wing carry-through structure passes below the floor. Necessary to have special loading and boarding equipment. 2. Best for braced-wing monoplanes.Cessna • Struts cause little interference when attached to the lower side of the wing. • Lighter struts because they are stressed in tension. 3. The wing is generally lighter.

  3. C-17

  4. Cessna 152

  5. HIGH WING: PROS 4. The nose-wheel gear is shorter and lighter. 5. Best for STOL QSRA • Close proximity of the wing to the ground during TO and LNG may cause pronounced undesirable ground effects. • Required ground clearance for large, fully deflected TE flaps and large props would entail a very tall and heavy LG in a low wing configuration. 6. Safer. • Damage and fire risk is limited during a forced LNG. 7. Less Ground Effect in CTOL Shorts 330 • Smaller LNG distance. 8. Best for amphibians Boeing 314-A • Keeps engines away from H2O.

  6. Quiet Short Research Aircraft

  7. Shorts 330

  8. Boeing 314-A

  9. HIGH WING: CONS 1. Problem w. the retraction of the mainLG. • In small, high-wing propeller ac, main LG can be retracted into engine nacelles (Fokker F-27) or in tail booms (Hawker Siddeley Argosy). In large ac, however, this would make the LG too tall and heavy. • A solution for large ac: fuselage-mounted LG. • Problem 1: strengthening of the fuselage structure required for the transmission of the LNG impact results in W increase. • Problem 2: with a fuselage mounted main LG the track may not be sufficiently wide. 2. No ground effect in CTOL. • Increased TO distance.

  10. Fokker F-27

  11. Hawker Siddeley HS.660 Argosy

  12. HIGH WING: CONS 3. No room for underfloor cargo. • Fuselage section below the floor is flattened to reduce LG height + keep the floor low (4-4.5 ft = 1.2-1.4 m). • Solution: longer cargo hold in cabin. • Problem 1: longer fuselage. • Problem 2: large cg travel. 4. Unsafe • Fuselage will sink when ac is forced down on water. Provisions must be made for escape through the cabin roof. 5. Not good for highly maneuverable ac. • Too stable in roll.

  13. HIGH WING: CONS 6. ~ 20% more SV than a low-wing configuration. 7. OEW is generally higher. 8. Structural design is generally more complicated.

  14. MID WING: PROS • Min D in high-speed flight. (fighters, trainers) • Surfaces at wing / fuselage junction meet at 900 angles; interference between BLs at low a is minimized. • Fuselage section at the location where the wing is mounted is roughly cylindrical; divergence of airflow over wing root is minimized. • Best maneuverability. • Wing can be continuous through the fuselage • transfer of loads from the wing can take place via almost solid “bulkheads”, to which each wing-half is attached.

  15. F-18 Hornet & T-37

  16. MID WING: CONS • Reduced internal useful fuselage volume. • That is the reason why mid-wing configurations are not adopted for transports.

  17. LOW WING: PROS • Efficient use of fuselage under-floor space. • Large tail angle allows for optimum rotation during TO (especially for stretched versions). • Easy retraction of main LG between wing spars. • Safer. • A low wing and possibly the engines attached to it form a large energy absorption mass during a forced LND. • Favorable ground effects. • Decreased TO distance. • AC lands itself; little or no elevator movement required to flare out because L increase results in nose-up pitching M. • Better maneuverability than a high wing.

  18. LOW WING: CONS • Unsafe. • Potential fire hazard during forced LND when wing and engines hit the ground. • Unfavorable ground effects. • AC floats during LND; longer LND distance. • Greater elevator deflection required for TO rotation and LND flare out. • Decreased downwash on the tail results in nose down pitching M. • Longer LGespecially on swept back wings, to provide tip clearance during TO rotation.

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