Mass and Balance

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  • 1. MASS & BALANCE 1
  • 2. Aircraft stability depends directly of C.G. position Static stability: W W Aircraft must be in static stability in whole flight regimes. Therefore, C.G. position must be always ahead of Aerodynamic Centre i.e. Centre of Wing’s Lift (Centre of Pressure). 2
  • 3. Influence of C.G. position on aircraft performance V2 TOD VS VREF ALD 3
  • 4. MORE FWD C.G. => DRAG FUEL CONSUMPTIONMORE AFT C.G. => DRAG FUEL CONSUMPTION 4
  • 5. C.G. LIMITS Range of C.G. position (FWD & AFT limit) C.G. Aft Forward Mean Aerodynamic Chord. limit limitThe CG position is expressed as a percentage of the Mean Aerodynamic Chord(MAC) / Referent Chord (RC).It must remain between a forward and an aft limit depending on the aircraft weight. 5
  • 6. C.G. Envelope Weight MIT LI FWD IMIT AFT L C.G. position (H-arm) 6
  • 7. Certified vs. Operational C.G. limitsCertified Limits•Limits determined during aircraft testing phase (only flight crewonboard, no PAX, no CARGO).•Certified C.G. envelope are published in the AFM and WBMOperational Limits•Certified Limits accounted for possible errors during operations: •standard PAX weight error •pax/crew movement during flight (catering service, toilette) •fuel density error •movable parts error (landing gear, flaps/slats) •cargo distribution error •PAX distribution error •human accuracy error (balance chart on manual loadsheet)•Operational C.G. envelope to be used in operations (published onthe Loadsheet form). 7
  • 8. Errors affecting C.G. position are expressed in term of narrower C.G.envelope limits – certified limits become operational limits. Certified limits (AFM) Operational limits (Loadsheet) ng n di La ff eo k Ta W ZF ing nd La & off ke Ta Accounted for errors 8
  • 9. WEIGHTSRamp Weight MRWWeight of aircraft at block-off. MTOW Taxi fuelActual Takeoff Weight (ATOW)Weight of aircraft at beginning of takeoff(line-up position). + Traffic Load (TL) - Trip fuel Takeoff fuel(TOF) Weight of total payable load (PAX, (TRIPF) BAGG, CARGO, MAIL). and other load. MLW Actual Landing Weight (ALW)Operating Weight (OW) Weight of aircraft at landing at destination - ReserveWeight of aircraft ready for operations, fuelwithout payload (ready for embarkation MZFW + Takeoff Fuel Actual Zero Fuel Weight (AZFW)of passengers and baggage/cargo). Weight of total usable fuel onboard Weight of aircraft in flight when all usable aircraft at beginning of takeoff fuel is burned (engine shut down) (line-up position). Structural/performance limited weights:Dry Operating Weight (DOW) /Operating Empty Weight (OEW) •MRW: Max. Ramp Weight + Operator’s ItemsWeight of aircraft ready foroperations, without fuel and payload. •MTOW: Max. Takeoff weight Weight of items added by the Operator: Crew & crew’s baggage, •MLW: Max. Landing Weight Catering, Catering removable equipment, Potable water, Toilet •MZFW: Max. Zero Fuel WeightManufacturer’s Empty Weight fluids, Documentation, ...(MEW) / Basic Empty Weight / Relations:Basic WeightWeight of structure, power plant, •DOW + PL=AZFWsystems and other items that areintegral part of the aircraft, •AZFW+TOF=ATOWincluding fluids inclosed systems(hydraulic oil,...) •ATOW-TRIPF=ALW 9
  • 10. MAX. TRAFFIC LOAD CALCULATION MAX. TL = MATOW – TOF – DOW MTOWSTRUCT MTOWTAKEOFF = Min. of MTOWT/O PERF.MATOW – Max. MLWSTRUCTAllow. Take Off = Min. of MLW + TRIPF ; MLW = Min. ofWeight MLWLDG PERF. MZFW + TOF 10
  • 11. Passengers’ weight•Usually, standard (statistic) passengers weight is used. Actual weights – weighingof passengers is complicated.•If unusual group of passengers exist, they must be weighed or must declare ownweight.•Carry-on luggage included in PAX weightOPS 1.620 prescribe min. standard passengers’ weights to be used in operations: Passenger seats P20 P 30 Male Female All Adult All flights except 88 kg 70 kg 84 kg holiday charters Holiday charters 83 kg 69 kg 76 kg Child 35 kg 35 kg 35 kg Infant 0 kg 0 kg 0 kg All Adult weights applicable only for aircraft with 30 PAX seats or more 11
  • 12. Baggage weightUsually, baggage (checked-in) is weighed and actual weights are used. If baggage isnot weighed (check-in system out of service), standard weights may be used OPS 1.620(f) Type of flight Bagg. weight/piece Domestic 11 kg Within Europe 13 kg Intercontinental 15 kg All other 13 kgSimilar to PAX standard weights, operator may perform weighing process with specificsurvey, statistical analysis and obligatory use of results. Cargo Weight All cargo is weighed before loading – Actual weights are used. Fuel Weight Actual volumetric values are used (liters). Fuel(kg) = Fuel(lt ) × ρ FUEL Precision of fuel weight depends on fuel density determination. 12
  • 13. C.G. POSITIONOPS 1.605 Aircraft weighingAn operator must establish the mass and the centre of gravity of any aeroplane byactual weighing prior to initial entry into service (usually before delivery) andthereafter at intervals of 4 years if individual aeroplane masses are used and 9years if fleet masses are used.The accumulated effects of modifications and repairs on the mass and balancemust be accounted for and properly documented.Furthermore, aeroplanes must be reweighed if the effect of modifications on themass and balance is not accurately known (e.g. aircraft painting).Whenever the cumulative changes to the dry operating mass exceed ± 0·5% of themaximum landing mass or the cumulative change in CG position exceeds 0·5% ofthe mean aerodynamic chord, the mass and the CG of each aeroplane shall be re-established either by: - Weighing; or - Calculation, if influence of modification is exactly known 13
  • 14. C.G. determinationIndex method – large aircraftBy large aircraft, moments are big figures (~105). Therefore, it is inpractical tomanipulate with such a big numbers.By introducing INDEX, moments are transformed into small figures that arepractical for use. Moment INDEX = +K CC and K are constants arbitrary chosen by operator.Constant C reduce Moment to acceptable figure.Constant K prevent negative values (when C.G. is ahead of balance line) 14
  • 15. Datum Line•Origin point arbitrary chosen by manufacturer as reference for positioning items (firewall, leadingedge, or any other point outside the aircraft).•Position of any item is expressed as distance from Datum Line.•Also known as H-arm or Arm or STA (Station)Balance Line•Point arbitrary chosen as reference for balance calculation (to avoid big figures when calculatingmoments).•Moments are calculated around balance line.•Position of balance line is known as Referent Station (Ref. STA) and is expressed as distance fromDatum Line.•Datum Line may be chosen as Balance Line (usual by smaller aircraft) Balance Line Referent Station (Ref.STA) MAC (RC) LEMAC Datum Line 15
  • 16. Balance Line Referent Station (Ref.STA) MAC (RC) LEMAC c.g.Datum Line H-arm c.g. (STA c.g.) Aircraft Weight (W) Moment INDEX = +K C Moment = W × ( H − arm c.g. − Re f . STA ) Belle Air values for C and K: W × ( H − arm c.g. − Re f . STA ) C=1000 INDEX = +K K=50 C 16
  • 17. DOW × ( Harm c.g . − 17.25) A319: DOI = + 50 1000 DOW × ( Harm c.g . − 18.85) A320: DOI = + 50 1000DOW/DOI values are pre-calculated for possible crew configurations and aregiven in form of DOW/DOI table. DRY OPERATING WEIGHT / DRY OPERATING INDEX DOW/ DOI (kgs/ index) A320-233 Applicable for aircraft registration: DRY OPERATING DRY CONFIGURATION WEIGHT* OPERATING REMARKS INDEX* kg 2+0 42344 48 3+0 42429 47 4+0 42514 46 2+4 42904 50 2FWD/2AFT(Ld) 2+5 42979 51 2FWD/3AFT 3+4 42989 48 2FWD/2AFT (Ld) 3+5 43064 49 2FWD/3AFT 4+4 43074 47 2FWD/2AFT (Ld) 4+5 43149 48 2FWD/3AFT 17
  • 18. Balance Line Index correction Referent Station (Ref.STA) MAC (RC) LEMACDatum Line H-arm Loaded/Unloaded Weight (±∆W) ±∆ ×( Harm −Re f .STA ) W ∆ = I C New INDEX = INDEX +∑ I ∆ Indexes are aditive 18
  • 19. Example: A320 , Crew 2+4, DOW 42904 DOI 50, 300kg .EIC in Cargo 1 and 400kg .EIC in Cargo 4 added. Maximum capacity Length of Compartment Volume arm from Index value Gross Description reference +/- Number Weight (m3) station per1kg (meters) 1 FWD 3402 13.28 -6.424 - 0.00642 300*-0.00642 ~ -2 3 AFT 2426 9.76 +4.013 + 0.00401 4 AFT 2110 8.5 +7.408 + 0.00741 400*0.00741 ~ 3 5 AFT 1497 7.22 +10.532 + 0.01053 WEIGHT INDEX Crew 2+4 DOW/DOI 42904 50 .EIC/1/300 +300 -2 .EIC/4/400 +400 +3 NEW DOW/DOI CONFIGURATION 43604 51 19
  • 20. Last Minute Changes (LMC) OPS 1.625: “An operator must specify procedures for Last Minute Changes to the load.” LMC Policy: ?? 20
  • 21. Fill the Load & Trim Sheet for following conditions:Flight LZ222T, BGY-TIA, A319 F-ORAG, Crew 2/4,Version 144YDOW: 40406, DOI: 50TOF=5600kg, TRIPF=3000kgPAX: 40M/35F/0CH/0INF 144YBAGGAGE: 975kg @ CC4+5CARGO:NILMAIL: NILBoarding scenario: Section 0A:24 PAX 12M/12F Section 0B:34 PAX 17M/17F Section 0C:17 PAX 11M/6F 21
  • 22. B GYLZ 2 2 2 T F- O RAG 144Y 2 4 20.04.12 57000 61000 5600 3000 40406 62600 70000 64000 5600 46006 46006 16594 T 975 975 75 50 I 40 35 0 0 75 12 A 2 40 35 0 0 975 975 12 0 6 12 70 29.0 12 58 28.3 - 1 57 40 35 0 975 975 16594 5970 6945 6945 40406 9649 47351 57000 TOW 5600  ZFW 52951  70000 75 3000 SMITH 49951 22 61000
  • 23. Fill the Load & Trim Sheet for following conditions:Flight LBY72T, BRU-TIA, ATR72-500 F-ORAA, Crew 2/2,Version 68YDOW: 13 474, DOI: 16TOF=1970kg, TRIPF=1200kgPAX: 20M/20F/0CH/0INF 68YBAGGAGE: 300kg @ CC4+5 and 300kg @ CC4+6CARGO:NILMAIL: NILBoarding scenario: Section 0A:14 PAX 7M/7F Section 0B:12 PAX 6M/6F Section 0C:14 PAX 7M/7F 23
  • 24. B RULBY72T F- O RAA 68Y 2 2 20.04.12 20800 22350 1970 1200 13474 22770 22800 23550 1970 15444 15444 7326T 6 0 0 300 300 40 16I 20 20 0 0 40 29A 2 34 20 20 0 0 600 300 300 16 19 23.9 45 71 45 25.1 26 26 20 20 0 6 0 0 300 300 3160 7326 3760 3760 13474 3566  TOW 17234 20800  1970 ZFW 19204 22800 40 1200 18004 SMITH 24 23550