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Chapter 6
Cost
Costs are estimated using statistical models based on historical aircraft price and maintenance cost
data, with appropriate factors to account for technology impact and inflation. The aircraft flyaway
cost (CAC, in $) consists of airframe, mission equipment package (MEP), and flight-control-electronics
(FCE) costs. The direct operating cost plus interest (DOC+I, in cents per available seat mile (ASM))
is the sum of maintenance cost (Cmaint, in $ per flight hour), flight crew salary and expenses, fuel and
oil cost, depreciation, insurance cost, and finance cost. Inflation factors can be input, or internal factors
used. Table 6-1 gives the internal inflation factors for DoD (ref. 1) and consumer price index (CPI,
ref. 2). For years beyond the data in the table, optionally the inflation factor is extrapolated based on the
last yearly increase.
6–1 CTM Rotorcraft Cost Model
The CTM rotorcraft cost model (refs. 3–5) gives an estimate of aircraft flyaway cost and direct
operating cost plus interest. The basic statistical relations for airframe purchase price and maintenance
cost per hour are:
cAF = 739.66 KETKENKLGKR W 1.0619
AF (P/WAF ) 0.5887 N 0.1465
blade + ccomp
cmaint =0.49885 W 0.3746
E P 0.4635
with WAF = WE −WMEP−WFCE. The term ccomp = LWcomp accounts for additional costs for composite
construction; Wcomp is the composite structure weight, obtained as an input fraction of the component
weight, with separate fractions for body, tail, pylon, and wing weight. The configuration factors are:
KET = 1.0 for turbine aircraft 0.557 for piston aircraft
KEN = 1.0 for multi-engine aircraft 0.736 for single-engine aircraft
KLG = 1.0 for retractable landing gear 0.884 for fixed landing gear
KR = 1.0 for single main rotor 1.057 for twin main rotors, 1.117 for four main rotors
The MEP and FCE costs are obtained from input cost-per-weight factors: CMEP = rMEPWMEP and
CFCE = rFCEWFCE. These cost equations are based on 1994 dollars and current technology levels.
Including an inflation factor Fi and technology factors χ gives the unit flyaway cost CAC and maintenance
cost per flight hour Cmaint:
CAC = Fi (χAF cAF + CMEP + CFCE)
Cmaint = Fi χmaintcmaint
The statistical equation for cAF predicts the price of 123 out of 128 rotorcraft within 20% (figs. 6-1 and 6-
2). These equations also serve to estimate turboprop airliner flyaway costs by setting Nrotor = Nblade =1