Saturday, October 20, 2012

The Engineer's Tears

When I was a youngster I wanted to make model airplanes that actually flew. I learned from JP, big brother of a schoolfriend, how to design and build a basic airframe that would get off the ground and fly level.
It's not that hard, folks.
If you are flying faster, the rules are slightly different e.g. wing profiles for supersonic aircraft are different and the need for a smooth aerodynamic form is much more pronounced.

Anyone who takes an interest in flying things can pick up a lot of it from looking at the plentiful working examples - so why are fictional aircraft always done by people who ignore all the rules?

Here's a few examples from the DAZ site that make me throw up my hands in horror:

This baby even has a tank turret on top: weird, but take a look at the front profile of it. This thing (if it flies at all) is gonna be very slow. I'm also puzzled by the extra engines above the body that don't seem to be working. Oh wait - if they were turned on they would burn off the tailplane ! 

This one doesn't seem to have enough wing area to get off  the deck. 'nuff said.

This attempts to be the airborn equivalent of the jetski.  Ignoring the wing area issue for a moment, there is just one slight problem with that: the flyer is exposed to turbulent winds.  Provided you were flying at biplane-type speeds that could be okay - but then you would need much, much bigger wings.  Now ask yourself how the pilot is going to control this thing while standing up, buffeted by 100 mph-plus winds and no rudder pedals.
 I hope he has very strong arms !

 Ah,  I say- this one actually looks like it has enough wing area to get off  the ground, although the jet exhausts look a bit small for the size of craft.  Oh - hang on, where are all the control surfaces? where is the elevators - or any pitch control for that matter?
 . . . . . and then I saw another view . . . . .
What should be the main engine air intakes are partly closed off flat !  Add to that the louvres in the wing (so much for enough lifting surface to fly, sigh!) and once again this is just crazy.

Finally . . . . . . .
This is actually the best of the lot IMHO because it does not fall down on any of the foolishness shown above.
Aerodynamic? check.
Possibly enough thrust to get off the ground? check.
Possibly enough control to navigate? check.  (note those exhaust ducts on the tail?)

There's' just a couple of itty bitty problems.
 First, look at the front: the view from the pilot's seat is obscured forward so you won't see what's directly ahead.
Okay, maybe it has a camera and screen so the pilot sits behind armourplate. 

The other one is pretty obscure, so I don't really expect the creator of this flyer to know about it :- the man trouble with VTOL craft using jets is exhaust gas ingestion or EGI for short: when that happens, thrust drops off and the flyer comes down. Everything works fine once you are up in the air, it's those few feet above the runway that are the problem.  The Harrier jump jet uses some clever design to get away from it as much as possible but this design will get EGI in about one second -  that's why we don't have lots of VTOL flyers around using this method.

So in summary I will have to make my own SF flyers and spaceships  if I want them to pass muster.
More work, but at least I can be sure they will look like they might actually fly.
I might even be able to sell them on a website somewhere for pocket money. 

If you are interested, the place to go for some great design ideas for flying machines and spacecraft  (nearly real and real ones, that is !) is Scott Lowther's excellent Aerospace Projects Review Blog.

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