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17.9 “Design for Customer”

567

17.9.2 Worked-Out Example

From the worked-out example of the Bizjet, the following values are obtained. Because derivative aircraft values are obtained through simplified assumptions, they must be worked out in better detail. The linear relationship is used to work out the following example to provide a general idea.

Standard Parameters of the Baseline Aircraft

Unit cost in millions of U.S. dollars = $8 million; MTOM = 9,400 kg.

DOC in U.S. dollars per seat/nm = $0.352 per nautical mile per passenger (ten passengers).

Delivery time t in years (from the placement of order) = 1 year. Baseline aircraft = $0.8 million/passenger and $0.000851/kg MTOW.

Parameters of the Extended Variant Aircraft

Unit cost in millions of U.S. dollars = $9 million; MTOM = 10,800 kg.

DOC in U.S. dollars per seat/nm = $0.2875 per nautical mile per passenger (fourteen passengers).

Delivery time t in years (from the placement of order) = 1 year.

Large variant aircraft = $0.6428 million /passenger and $0.000833/kg MTOW.

Kn larger =

 

(DOC /DOC)

=

(0.352/0.2875)

 

(UnitCost/UnitCost ) × (t/10t + 0.9)

(9/8) × (1/10 + 0.9)

=

1.224/(1.125 × 1) = 1.088 (a better value)

 

Parameters of the Shortened Variant Aircraft

Unit cost in millions of U.S. dollars = $6 million; MTOM = 7,600 kg.

DOC in U.S. dollars per seat/nm = $0.482 per nautical mile per passenger (six passengers).

Delivery time t in years (from the placement of order) = 1 year. Small variant aircraft = $1 million/passenger and $0.00079 kg MTOW.

Kn smaller =

 

(DOC /DOC)

=

 

(0.352/0.482)

 

(UnitCost/UnitCost ) × (t/10t + 0.9)

(6/8) × (1/10 + 0.9)

=

0.7303/(0.75 × 1) = 0.974 (a lower value)

 

 

In general, a smaller derivative aircraft is penalized because it is heavier than it would be if it were a baseline design. The wing area is larger than what is required. The smaller variant is competitive aircraft, and there are aircraft in this class with similar DOC. Several new all-composite, four-passenger lighter jet aircraft have appeared recently and are selling at less than $5 million with better DOC. These new aircraft are yet to be proven in operational usage, and it will be some time before all-composite aircraft overtake conventional construction. The example of a six-passenger, smaller variant is a robust, all-metal aircraft with a larger cabin volume and high-end amenities suited to corporate demand. In a mixed fleet of three sizes, the total package offers benefits that are difficult to match. When an airline operates a mixed fleet of variants along with its baseline aircraft, the spare-parts

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