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Home arrow Engineering arrow Small Unmanned Fixed-Wing Aircraft Design. A Practical Approach
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Climb Performance

The climb performance of an aircraft and its variation with altitude is the result of a complex web of interactions between the aerodynamics of lift generation and the response of its powerplant to varying atmospheric conditions and airspeed. Typically a range of design points have to be considered, representing a variety of conditions, but at this early stage in the design process it is best to keep the number of these design points at a more manageable level. Here we use 80% of the cruise speed for the climb constraint.

In [9]: RateOfClimb_fpm = 591

In [10]: ClimbSpeed_KCAS = CruisingSpeed_KTAS * 0.8 The rate of climb constraint will be evaluated at this altitude:

In [11]: ROCAlt_feet = 0

Turn Performance

We define steady, level turn performance in terms of the load factor n (which represents the ratio of lift and weight). n = 1/ cos в, where в is the bank angle (so n = 1.41 corresponds to 45°, n = 2 corresponds to 60°, etc.).

In [12]: n_cvt_ = 1.41 Service Ceiling

In [13]: ServiceCeiling_feet = 500

Approach and Landing

In [14]: ApproachSpeed_KTAS = 29.5

We define the margin by which the aircraft operates above its stall speed on final approach (e.g., a reserve factor of 1.2 - typical of manned military aircraft - means flying 20% above stall, a reserve factor of 1.3 - typical of civil aircraft, means 30% above stall; for small UAVs, lower values may be considered).

In [15]: StallReserveFactor = 1.1

In [16]: StallSpeedinApproachConf_KTAS = ApproachSpeed_KTAS

/StallReserveFactor

print 'Stall speed in approach configuration: {:0.1f} KTAS'

.format(StallSpeedinApproachConf_KTAS)

Stall speed in approach configuration: 26.8 KTAS

Maximum lift coefficient in landing configuration:

In [17]: CLmax_approach = 1.3

We also define the highest altitude AMSL where we would expect the aircraft to be established on a stable final approach in landing configuration:

In [18]: TopOfFinalApp_feet = 100

 
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