\section{Introduction}\vspace{1ex}%\noindent

The survey of Concurrent Engineering by Lawson and Karandikar
\cite{lawson:1994}, for all widely varying reported results,
reinforced CE as the \textsl{de facto} methodology for product
development. There was broad US industry participation in the
survey, but the primary response, 28~\%, came from the aerospace
sector. It is here that the benefits of CE methodology are most
pronounced. Also it is in Aeronautics and Shipbuilding that the
numerical analysis and computer based simulation tools (NAST) are
most various, sophisticated and demandable.\smallskip

This  has  led many engineers of these fields to believe that the
integration of conventional CAD systems with the NAST  is the
issue of vital importance. The main reasons for this are a higher
product quality (safety, first of all), the shortened
product-development time and reduced overall (life-cycle) costs
\cite{olsson:2000}.\smallskip

We  found quite a few reports and papers  devoted to design
development and decision support problems in  Aeronautics and
Shipbuilding,  \cite{beggs:1989} and \cite{mistree:1990}
among them. However, of a number of those publications dealing
with the principles of automated control systems design with
special reference to their application in navigation systems,
available are only a few.\smallskip

Historically  things went so that amongst the NAST pre-eminent and
most demandable in many branches of industry was
the finite element method \cite{fagan:1992}. %page240CE2002
Clearly  the first studies on CAD/NAST integration appeared as
CAD/FEM integration. However, the early research efforts did not
assume a full-scale integration. Mostly they addressed the
particular issues, such as unification of final element analysis
and geometric modeling \cite{shephard:1988}, determination of
appropriate finite element sizes automatically and generation of a
near optimal mesh \cite{young:1990}, or integration of
product design knowledge into a knowledge-based computer module to
implement parametric modeling and substructuring techniques
\cite{chung:1993}.

The  first  and very important step in the desired direction was
made in \cite{roy:1994}. For an automated design environment,
it has led to a generic framework whose significance we believe is
beyond the scope of the article, -- the integration of CAD and FEM
packages.

Based  on  this and our previous work \cite{semoushin:2002},
in this paper we adapt the above mentioned framework to developing
an intelligent integrated CAD/NAST environment for navaids
concurrent engineering. Hence we infer that our paper is addressed
in the main to those designing practitioners who consider the lack
of integrated technology tools as a barrier to implementing CE in
complex navigation systems development. As for those who are
responsible for designing such tools, the whys and wherefores of
the design can best be perceived in terms of mathematical %%%general
multi-variable  multi-mode stochastic control systems theory
\cite{semoushin:2002, semoushin:2004}.
