Beban Pesawat Dipl.-Ing H. Bona P. Fitrikananda UA MTC
Weight and CG Range Beban Pesawat / Aircraft Loads 2
Gravitational Load Load Limitation WEIGHT Load Distribution & BALANCE 3
Weight Groups Airframe Structure sayap, ekor, fuselage, landing gear, nacelle, bidang atur Propulsion Group mesin, bagian yang berhubungan dengan instalasi dan pengoperaisan, fuel system, perlengkapan thrust reserver Airframe Equipment and Services Fixed: fixed ballast, fluida sistem tertutup Removable: perlengkapan dan sistem fluida yang bukan merupakan bagian integral pesawat Operational Items personel, perlengkapan dan suplai yang dianggap perlu untuk suatu operasi Payload semua jenis muatan (penumpang, bagasi, kargo dll.) Total Fuel semua bahan bakar (taxi, flight, reserve) 4
Weight Groups 5
Terminologi Weight / Berat: Manufacturer Empty Weight (MEW) berat struktur pesawat, powerplant installation dan fixed equipment Delivery Empty Weight (DEW) berat ketika diserahkan oleh pabrik (MEW + berat standar removable items) Basic Empty Weight (BEW) DEW ditambah atau dikurangi berat standard item variations atau MEW + removable item Operational Empty Weight (OEW) berat pesawat tanpa payload dan bahan bakar 6
Terminologi Weight / Berat: Zero Fuel Weight OEW + payload Take Off Weight berat pesawat bermuatan pada saat brake release (start take off). Tidak boleh melebihi Maximum Take Off Weight Ramp Weight berat Take Off + berat bahan bakar untuk pemanasan dan taxying Landing Weight berat pada saat Touch Down. Batasnya adalah Maximum Landing Weight Gross Weight berat total pesawat pada setiap operasi 7
Total Weights The component weights are grouped together to form a number of total weights that are routinely used in aircraft design. This section lists some of the typical weights and their definitions: Maximum Taxi Weight Maximum Brake Release Weight Maximum Landing Weight Maximum Zero-Fuel Weight Operational Empty Weight Manufacturer's Empty Weight 8
Total Weights MAXIMUM TAXI WEIGHT The certified maximum allowable weight of the airplane when it is on the ground. This limit is determined by the structural loading on the landing gear under a specified set of conditions and/or wing bending loads. MAXIMUM BRAKE RELEASE WEIGHT The certified maximum weight of the airplane at the start of takeoff roll. Maximum Brake Release Weight will always be less than Maximum Taxi Weight to allow for fuel burned during taxi. Brake release weight, in operation, may be limited to values less than Maximum Brake Release Weight by airplane performance, and/or airfield characteristics. 9
Total Weights MAXIMUM LANDING WEIGHT The certified maximum weight of the airplane at touch-down. This limit is determined by the structural loads on the landing gear, but not under the same conditions that determine maximum taxi weight. Landing weight, in operation, may also be limited to values less than Maximum Landing Weight by airplane performance and/or airfield characteristics. MAXIMUM ZERO FUEL WEIGHT The maximum weight of the airplane without usable fuel. 10
Total Weights OPERATIONAL EMPTY WEIGHT Manufacturer's empty weight plus standard and operational items. Standard items include unusable fuel, engine oil, emergency equipment, toilet fluid and chemicals, galley, buffet and bar structure, etc. Operational items include crew and baggage, manuals and navigational equipment, removable service equipment for cabin, galley and bar, food and beverages, life vests, life rafts, etc. MANUFACTURER'S EMPTY WEIGHT Weight of the structure, powerplant, furnishings, systems, and other items of equipment that are considered an integral part of a particular airplane configuration. It is essentially a "dry" weight, including only those fluids contained in a closed system (such as hydraulic fluid). 11
Total Weights Other totals that are commonly used include: Actual take-off weight Maximum take-off weight Landing weight Zero payload weight The airplane zero fuel weight is the sum of each of the components as shown below. Note that the actual zero fuel weight is generally less than the maximum zero fuel weight. The maximum zero fuel weight, may in fact exceed the zero fuel weight that is possible for this particular aircraft, but the structure is designed to handle the larger values to accommodate futur 12
Total Weights Wzfw = Wwing + Whoriz + Wvert + Wrud + Wfuse + Wcrew + Wopitems + Waircond + WElectn + WElectc + Wsurfc + Wgear + Whydpnu + Wpropul + WAttend + Wpax + Wbags + Wcargo + Wother + Winst + Wapu + Wfurnish Wpayload = Wpax+Wbags+Wcargo Wmt = Wzfw-(Wpayload+Wcrew+Wattend+Wopitems) Wreserv =.08*Wzfw Wfuel = TOW-Wzfw-Wreserv Wnopay = Wmt+Wfuel+Wreserv+Wcrew+Wattend+Wopitems Landing weight includes 1/2 maneuver fuel Wland = Wzfw+Wreserv+.0035*TOW Wowe = Wzfw-Wpayload 13
Total Weights 14
Gravitational Load Load Limitation WEIGHT Load Distribution & BALANCE 15
Center of Gravity (CG) The Center of Gravity or CG is the point where the aircraft s weight is applied. The position of the CG has to stay within certain limits to ensure aircraft maneuverability and stability and also the aircraft structure integrity. 16
Forces Applied on Flying Aircraft Diagram of forces 17
Forces Applied on Flying Aircraft Influence of the THS (Trimmable Horizontal Stabilizer) In order to keep the airplane level, a downward force is created by the Trimmable Horizontal Stabilizer (THS) which has to be trimmed accordingly. 18
Forces Applied on Flying Aircraft This additional force creates both lift degradation and important pitchup moment that counters the pitch-down moment. The pitch up moment is due to important balance arm between the aircraft CG position and the THS where the additional force is applied. 19
Influence CG Position on Performance Impact on the stall speed The stall speed (Vs) is speed at which the aircraft will stall. At that speed the upward force (mainly lift) is equal to the downward force (mainly weight + THS counter force) applied on the aircraft. The lift is directly related to the aircraft speed: the faster the aircraft flies the greater the lift. 20
Influence CG Position on Performance Impact on the stall speed 21
Influence CG Position on Performance Impact on takeoff performance Optimized takeoff distance or takeoff weight Take off Roll 22
Influence CG Position on Performance Impact on takeoff performance Takeoff climb Basic and alternate CG positions 23
Influence CG Position on Performance Impact on takeoff performance Basic and alternate CG positions The A320 and the A340 usually have a Dry Operating Weight (DOW) CG of around 30%MAC and their most forward certified CG limit is around 17%MAC. These tail-heavy aircraft usually have an aft takeoff CG position. This means that their everyday performance is better than the certified performance for the most forward CG position. So a second CG position forward limit has been certified for these two aircraft. at 25%MAC for the A320 at 26%MAC for the A340. 24
Influence CG Position on Performance Impact on takeoff performance Basic and alternate CG positions All takeoff performances in the certified Airplane Flight Manual are given for both these CG positions. takeoff CG must be of at least 27%. However, to take into account the errors in the determination of the CG position, a margin has to be applied on the calculated takeoff CG. I.e., for an A320, in order to be able to use the performance calculated for a 25% CG, the calculated takeoff CG must be of at least 27%. 25
Influence CG Position on Performance Impact on in-flight performance Let.s revert to the impact of the CG position on the forces applied on the aircraft and to the consequence it has on aircraft performance. Reminder: In order to keep the airplane level, the Trimmable Horizontal Stabilizer (THS) creates a downward force. This additional force creates a pitch-up moment that counters the pitch-down moment due to the aircraft weight but also a drag increase which magnitude depends on the aircraft CG position. 26
Influence CG Position on Performance Impact on in-flight performance 27
Influence CG Position on Performance Impact on in-flight performance The further forward the CG, the greater the counter moment necessary to keep the flight level. This is due to the increasing balance arm between lift and weight. In the case of a forward CG position, the THS is set to an aircraft nose-up position that creates important lift degradation therefore creating important drag. This drag will lead to an increase in fuel consumption. 28
Influence CG Position on Performance Impact on landing performance Landing distance or landing weight 29
Summary 30
Conclusion 31
Certified Limits Design Process The previous chapter has dealt with the influence of the position of the aircraft center of gravity on performance. The conclusion was that in general the further aft the CG, the better the aircraft performances. However, the CG has to stay within certain certified limits. These limits are defined in the Limitations volume of the Flight Manual (Chapter 2.02.00) and are also in the Weight and Balance Manual (Chapter 1.10, Limitations) These limits are mainly due to: structural limitations handling qualities a compromise between performances and aircraft loading 32
Certified Limits Design Process 33
Limitation summary 34
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