Aircraft Design: Synthesis and Analysis - part 3 ppt

The table available here gives the external cross-section dimensions and seating layouts for a number of aircraft. Use the interactive layout computation in exercise 2 to check your hand layout. Sample Cross-section Dimensions and Seating Layouts N per Max NDecks Layout Width Height Aircraft Name XSection Abreast 2 2 1 11 64 60 Lear25 2 2 1 11 65 70 DHC6 2 2 1 11 94 94 GIV 4 4 1 22 110 101 DHC7 4 4 1 22 104 104 Dash8-300 4 4 1 22 113 113 Concorde 5 5 1 23 134 134 BAC111 5 5 1 23 130 130 F100 5 5 1 23 131.5 143 MD80/717 6 6 1 33 148 - 737/757 6 6 1 33 147 - DC8 6 6 1 33 140 140 BAE146 6 6 1 33 155.5 - A320 7 7 1 232 198 217 767 7 7 1 232 186 - 7J7 8 8 1 242 222 - A300/A310/A330/A340 9 9 1 252 237 237 MD11 9 9 1 252 235 235 L1011 9 9 1 252 244 244 777 16 9 2 333/232 266 336 A3xx Study (1994) 16 10 2 343/33 256 308 747 18 10 2 343/242 266 336 A380 Coach 19 11 2 353/242 - - MD-12 (study) 19 11 2 2342/242 307 373 Boeing NLA (study) 26 10 3 343/343/33 261 403 A 3-deck guess 29 12 3 343/363/232 335 403 Based on Douglas Study Exercise 2: Fuselage Cross-Section Enter fuselage cross-section parameters. About the input variables: ● Seat Width: The width of the seat including armrests associated with that seat (inches). ● Aisle Width: The width of the aisle in inches. ● Main Deck Seat Layout: Distribution of seats and aisles written as an integer. 32 means 3 seats together, then an aisle, then 2 seats. 353 means a twin aisle airplane with 3 seats then an aisle, then 5 seats in the center, then another aisle, then another 3 seats. ● Upper Deck Seat Layout: On airplanes with an upper deck the seat layout as described above. If the airplane has a single deck, enter 0. At the moment the cross-section is not drawn with an upper deck. ● Height / Width: The ratio of fuselage maximum height to width. ● Floor Height: The vertical offset of the floor from the center of the cabin in units of cabin height. A value of 0 places the floor at the fuselage centerline, while a value of 0.5 would place the floor at the lowest point on the fuselage. Typical value: 0.15. Fuselage Shape Planform Layout Cabin Dimensions The figure below shows a generic fuselage shape for a transport aircraft. The geometry is often divided into three parts: a tapered nose section in which the crew and various electronic components are housed, a constant section that contains the passenger cabin, and a mildly tapered tail cone. Note that passengers or other payload may extend over more than just the constant section, especially when the fuselage diameter is large. Because of the long tail cone sections, the pressurized payload section often extends back into this region. Additional area is required for lavatories, galleys, closets, and flight attendant seats. The number of lavatories depends on the number of passengers, with about 40 passengers per lavatory, a typical value. One must allow at least 34" x 38" for a standard lavatory. Closets take from a minimum 3/4" per passenger in economy class to 2" per first class passenger. Room for food service also depends on the airline operation, but even on 500 mi stage lengths, this can dictate as much as 1.5" of galley cabinet length per passenger. Attendant seats are required adjacent to door exits and may be stowed upright, but clear of exit paths. In addition, emergency exits must include clear aisles that may increase the overall length of the fuselage. The requirements are described in the FAR's. On average the floor area per person ranges from 6.5 ft^2 for narrow body aircraft to 7.5 ft^2 for wide- bodies in an all-tourist configuration. A typical 3-class arrangement requires about 10 ft^2 per person. The figures below show two layouts for the 717. Note the fuselage nose and tailcone shapes. Two-Class 717 configuration with 8 first-class seats with 36" pitch and 98 coach seats with 32" pitch. Single-class 717 configuration with 117 seats at 32" and 31" pitch. In addition to providing space for seats, galleys, lavatories, and emergency exits as set by regulations, the aircraft layout is important for maintainence and studies are done early in the program to determine that the layout is compatible with required ground services. Aerodynamics The fuselage shape must be such that separation and shock waves are avoided when possible. This requires that the nose and tail cone fineness ratios be sufficiently large so that excessive flow accelerations are avoided. Figure 2 shows the limit on nose fineness ratio set by the requirement for low wave drag on the nose. Even when the Mach number is low, constraints on fuselage pressure gradients limit nose fineness ratios to values above about 1.5. The tail cone taper is chosen based on similar considerations and generally falls in the range of 1.8 to 2.0. The details of fuselage shaping may be determined by looking at the pressure distributions. Several rules result from these analyses: The transition from nose to constant section, and constant section to tail cone should be smooth - free of discontinuities in slope (kinks). The tail cone slopes should resemble those shown in the examples. That is, the slope must change smoothly and the trailing edge should not be blunt. The closure angle near the aft end should not be too large (half angle less than 14°- 20°). Considerations Related to Fuselage Side-View The shape of the fuselage in side view is determined based on visibility requirements for the cockpit and ground clearance of the tail cone. Usually aft-fuselage upsweep is required to provide the capability of rotating to high angles of attack on the ground (often about 14°). The upsweep cannot be set without estimating the length of the main gear, but this can be done early in the design process by comparison with similar aircraft. Exercise 3: Fuselage Top View Enter fuselage seating parameters. About the input variables: ● Number of Seats: The total number of seats to be included at the specifed effective pitch. ● Seat Pitch: The average longitudinal distance between seats. This drawing includes only a single seat pitch, while most aircraft will be divided into 2 or 3 classes with rather different seat pitch. Use an efgfective value that produces the correct cabin length. ● Nose Fineness: The ratio of nose length to maximum diameter. The nose section is defined as the section that extends from the forwardmost point on the aircraft to the maximum diameter section. ● Tailcone Fineness: The ratio of tailcone length to maximum diameter. The tailcone section is defined as the section the end of the constant section to the aft end of the fuselage. ● Forward Extra Space: The distance (in feet for now) from the start of the constant section to the first row of seats. This parameter is used to add extra space for galleys or closests, or may be made negative if seats extend into the "nose" section of the fuselage. ● Aft Extra Space: The distance (in feet for now) from the end of the constant section to the last row of seats. This parameter is used to add extra space for galleys or closests, or may be made negative if seats extend into the tailcone section of the fuselage. The layout is based on the cross-section geometry specified in exercise 2. Fuselage and Seating-Related FARs FAA Regulations Affecting Fuselage Design A number of federal regulations have a major effect on the fuselage layout and sizing. Included here are links to portions of FAR Part 25 that influence fuselage design. Seating-Related Items Emergency Egress Emergency Demonstration [...]... resulting from fuselage deformation in a minor crash landing (h) When required by the operating rules for any large passenger-carrying turbojet-powered airplane, each ventral exit and tailcone exit must be-(1) Designed and constructed so that it cannot be opened during flight; and (2) Marked with a placard readable from a distance of 30 inches and installed at a conspicuous location near the means... water landing (as prescribed in paragraphs (c) and (d) of this section), the external doors and windows must be designed to withstand the probable maximum local pressures Sec 25.8 03 Emergency evacuation (a) Each crew and passenger area must have emergency means to allow rapid evacuation in crash landings, with the landing gear extended as well as with the landing gear retracted, considering the possibility... high, with corner radii not greater than one-third the width of the exit, located over the wing, with a step-up inside the airplane of not more than 29 inches and a step-down outside the airplane of not more than 36 inches (5) Ventral This type is an exit from the passenger compartment through the pressure shell and the bottom fuselage skin The dimensions and physical configuration of this type of exit... berth, and its supporting structure, and each safety belt or harness and its anchorage must be designed for an occupant weight of 170 pounds, considering the maximum load factors, inertia forces, and reactions among the occupant, seat, safety belt, and harness for each relevant flight and ground load condition (including the emergency landing conditions prescribed in Sec 25.561) In addition-(1) The... the forward and aft directions If two or more main aisles are provided, there must be unobstructed cross-aisles at least 20 inches wide between main aisles There must be-(1) A cross-aisle which leads directly to each passageway between the nearest main aisle and a Type A exit; and (2) A cross-aisle which leads to the immediate vicinity of each passageway between the nearest main aisle and a Type 1,... configurations In addition-(a) There must be a passageway leading from the nearest main aisle to each Type I, Type II, or Type A emergency exit and between individual passenger areas Each passageway leading to a Type A exit must be unobstructed and at least 36 inches wide Passageways between individual passenger areas and those leading to Type I and Type II emergency exits must be unobstructed and at least 20... component at zero-lift and a lift-dependent component but includes only the increments due to Mach number (CL and Re are assumed to be constant.) Zero-lift drag is the drag at M=0.5 and CL = 0 It consists of several components, discussed on the following pages These include viscous skin friction, vortex drag due to twist, added drag due to fuselage upsweep, control surface gaps, nacelle base drag, and miscellaneous... radii not greater than one-third the width of the exit, in the pressure shell and incorporating an approved assist means in accordance with Sec 25.809(h), 25 additional passenger seats (iii) For a tail cone exit incorporating an opening in the pressure shell which is at least equivalent to a Type III emergency exit with respect to dimensions, step-up and step-down distance, and with the top of the opening... collapse of one or more legs of the landing gear; and (2) Within 10 seconds measured from the time when the opening means is actuated to the time when the exit is fully opened (c) The means of opening emergency exits must be simple and obvious and may not require exceptional effort Internal exit-opening means involving sequence operations (such as operation of two handles or latches or the release of... landing conditions prescribed in Sec 25.561) In addition-(1) The structural analysis and testing of the seats, berths, and their supporting structures may be determined by assuming that the critical load in the forward, sideward, downward, upward, and rearward directions (as determined from the prescribed flight, ground, and emergency landing conditions) acts separately or using selected combinations of loads . 2 35 3/242 - - MD-12 (study) 19 11 2 234 2/242 30 7 37 3 Boeing NLA (study) 26 10 3 3 43/ 3 43/ 33 261 4 03 A 3- deck guess 29 12 3 3 43/ 3 63/ 232 33 5 4 03 Based on Douglas Study Exercise 2: Fuselage Cross-Section Enter. - A300/A310/A 330 /A340 9 9 1 252 237 237 MD11 9 9 1 252 235 235 L1011 9 9 1 252 244 244 777 16 9 2 33 3/ 232 266 33 6 A3xx Study (1994) 16 10 2 34 3 /33 256 30 8 747 18 10 2 34 3/242 266 33 6 A380 Coach 19. 23 130 130 F100 5 5 1 23 131 .5 1 43 MD80/717 6 6 1 33 148 - 737 /757 6 6 1 33 147 - DC8 6 6 1 33 140 140 BAE146 6 6 1 33 155.5 - A320 7 7 1 232 198 217 767 7 7 1 232 186 - 7J7 8 8 1 242 222 - A300/A310/A 330 /A340 9