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• Mass Estimation

Piano predicts the mass characteristics of each aircraft using conventional preliminary design techniques. A mixture of semi-empirical and analytical equations is implemented. These have been calibrated against industry-derived data, including component mass breakdowns that are not generally available in the public domain. Individual contributions can be factored or overridden by the user to match known masses or to simulate the use of advanced materials.

For airframe structural components, the user can choose from several different estimation methods that predict the wing, fuselage and tail weights. Design load factors are evaluated according to standard FAR/JAR-25 rules for the critical gust and manoeuvre cases. Emphasis is placed on wing weight prediction. The fundamental wing box weight equations are sensitive to all the major design parameters such as aspect ratio, sweepback, wing area, thickness/chord ratios, loading conditions, etc. These predictions have a theoretical basis and are not simple 'one-line' statistical fits.

The Maximum Takeoff Weight (MTOW) can be set directly or iterated to match a particular range requirement. It can also be selected via parametric studies or numerical optimisation procedures, to satisfy any design constraints. The Operating Empty Weight (OEW) and other basic numbers such as the Maximum Zero Fuel Weight (MZFW) and Landing Weight (MLW) can be adjusted to ensure that airplanes in the database are consistent with the manufacturer's quoted values.

The following sample breakdown shows component masses and ancillary data:

 Design Limits
 _____________

 Design cruise point is Mach 0.82 at 37000.feet

 Design dive Mach     MD       0.87
 Design cruise speed  VC       345. KEAS
 Design dive speed    VD       400. KEAS
 Limit    load factor          2.55
 Ultimate load factor          3.83
 Cabin pressure differential   8.06 psi (limit)

 Mass Report      (in kg. and % of MTOW)
 ________________________________________

 MTOW    73500.
 OEW     41310.     (56.2%)
 MZFW    60500.     (82.3%)
 MLW     64500.     (87.8%)

 Mass Breakdown            kg.    % MTOW
 ________________________________________
 wing group               7819.   10.64 %
  (struct.box    6349.)
  (flaps          761.)
  (slats          342.)
  (spoilers       171.)
  (ailerons        77.)
  (winglets       119.)
 fuselage group           7984.   10.86 %
 stabiliser                837.    1.14 %
 fin                       458.    0.62 %
 undercarriage            2913.    3.96 %
 _____________________  _______   _______
 basic structure total   20011.   27.23 %

 dry engines total        4324.    5.88 %
 nacelles total           1622.    2.21 %
 pylons total              862.    1.17 %
 _____________________  _______   _______
 powerplants total        6808.    9.26 %

 furnishings              6000.    8.16 %
 surface controls         1035.    1.41 %
 fuel systems              286.    0.39 %
 hydraulics                551.    0.75 %
 electrics                 883.    1.20 %
 avionics                  566.    0.77 %
 APU                       430.    0.58 %
 air conditioning          657.    0.89 %
 misc. systems            1838.    2.50 %
 _____________________  _______   _______
 fixed equipment total   12246.   16.66 %

 manufact. contingency       0.    0.00 %
 _____________________  _______   _______
 Manufact. Empty Mass    39064.   53.15 %  = MEW

 crew                      700.    0.95 %
 operational items        1546.    2.10 %
 _____________________  _______   _______
 Operators Empty Mass    41310.   56.20 %  = OEW

 design payload          13650.   18.57 %
 design fuel             18540.   25.22 %
 _____________________  _______   _______
 Maximum Takeoff Mass    73500.   100   %  = MTOW 


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