Aircraft Design : A Simplified Approach

Sunday, December 4, 2016

Hello Everyone,

It's been pretty long since i have written or updated my blog. Reason being I was pursuing the field that I love i.e. Aerospace.
As a kid we all are fascinated to see a aircraft fly, I am still today !!
In my job or life i come across many people who are curious to know about aircraft and aircraft designs. Well then this article is for all of you out there you want to start learning the design philosophies.
So how does a aircraft design starts ?? Do the designers just assume a design and work on it or do they actually search for a better explained designs ?? ....... Well truthfully it is a mix of both with more percentage of the latter.

Step 1:
Every aircraft big or small when started as a design , had a clearly stated mission profile. That means what kind of role it was going to play in this vast market of aircrafts.
A normal mission profile problem statement may look like : 
"Aircraft that is able to fly domestic routes with 150 passengers or international routes with 50 passengers"
"Aircraft for 4 person and which can be used for either short flights or cadets' training flights"
Each of these mission statements defines some specifications required as mandatory to be achieved by the aircraft designs. Thus comes the assumptions : This helps the designers to either estimates or assume the specs by looking at historical data (previous aircrafts), and different aircraft components supplier specs.

Step 2:
Once the specs are decided, the designs of aircraft is scrutinized and selected which BEST fits the mission role.
Just for example : try considering a box wing aircraft and compare it with low wing, mid wing, top wing wing designs. Also throw in some flavors of swept-back, swept forward or delta wing designs. If tail is conventional or prefer a T-tail ? may be tri-tail ?
Engine to be mounted on wings or on fuselage ? to be turbo-props or turbofans ?
Once such kinds of questions are answered, you get to see a shady image of the aircraft that it is going to look like....

Step 3:
Now comes the interesting part 
Once the specs of the aircraft are known the long iterations of calculations begins. Why?
This is done to get the specs like : weight, center of mass, lift, drag, thrust values correctly. Aircraft designs (details) depends heavily on these values for the aircraft to fly in the first place, as well as efficiency of the design.
As aircraft flies it burns fuel and nobody want to fly in an aircraft which runs out of fuel. Fuel consumption, fuel weight, fuel quantity, range of the aircraft etc. are some of the crucial factors just like ones state above which determines the design and performance of an aircraft.
Aircraft design goes through a lot of iterative calculations usually 50 or more to get all the figures correct.
You can grab a copy of Aircraft Design book by DP Raymer to get a proper idea on what kind of calculations we are discussing about.

BTW : due to calculations a lot of design changes and tweaks occur in STEP 2.

Step 4:
Start creating detail designs of the aircraft....... 
Well honestly this takes a lot of time and good understanding of designs, manufacturing and tools.
This means one has to invest himself / herself in the study of aircraft performance,  designing of smallest part and assembly of all the parts to make a bigger design block until it becomes an aircraft.
At this point various studies are conducted using modern tools of CFD analysis or classical wind tunnels to gather aerodynamic data, aircraft stability data.
Once all the hard work is done, which is time consuming, and detail designs finalized ... the actual work to create a aircraft comes into play that is manufacturing, requirements gathering for avionics, supplier contracts etc...

So next time you watch an aircraft fly do think about the time people have invested in it , to make that fine machine fly and like always do enjoy the view.. !!
Happy Reading