Instituto Tecnológico de Aeronáutica

São José dos Campos - Brazil

Aircraft Design

Useful links    Quotes

Initial Sizing in Aircraft Design

The following module presents a method for estimating the size, weight, and thrust of a jet-powered aircraft introduced by Laurence K. Loftin Jr. in NASA Reference Publication 1060(LOFTIN 1980). Additional information about this methodology can be download here and here (this, written in Portuguese)

The aircraft design process is very complex and it is accomplished with high-cost, high-performance computer hardware, test rigs, flight tests and a lot of other tasks and equipment.

The design process is divided into some phases:

  • Feasibility study
  • Conceptual design
  • Preliminary design
  • Detailed design
  • Manufacturing
  • Entry into service

Tasks belonging to the conceptual design phase are outlined in the graph below:

In the conceptual phase, it shall be estimated the trust-to-weight ratio and the wing loading, two fundamental parameters in aircraft design. This section presents and provides an interactive methodology to estimate the best suited

 

 Takeoff mass, operating empty mass, fuel mass
 Engine thrust @ takeoff and other flight phases
 Airplane main components sizing

One of first tasks is the elaboration of the design diagram. For this, the following parts of Loftin's method will be presented:

  • landing field length
  • takeoff field length
  • climb gradient in the 2nd segment climb
  • climb gradient during missed approach
  • Required speed at cruise

In addition, an interactive panel enables the estimation of maximum takeoff mass (MTOW) from input data for a transport airplane

Design Diagram

 

MTOW Estimation