COMPROMISES

An aircraft is usually the result of a design

process that is a compromise between the

aircraft’s purpose, the available engine, the

current level of aerodynamic knowledge and

other factors. Over more than a century of

aircraft development, the knowledge of aircraft designers has continually improved,

and aircraft designs have naturally evolved

with the level of technical knowledge at the

time of their creation. I use the word “usually” because there have been highly unorthodox aircraft designs in which aerodynamics

did not play a significant role. In these cases,

the engine power prevailed.

Making a faithful scale model of an aeroplane

isn’t also an easy engineering discipline.

I understand

modellers who want their

model to match the original as perfectly as

possible. The problem is what exactly is an

original.

When my colleagues prepare a new aircraft

kit, they ideally work with the original production documentation, good quality photographs and, for verification, a 3D scan of the

actual machine. The historic aircraft we scan

are carefully selected. In museums, we look

for pieces in as historically faithful a condition as possible. For instance, concerning the

L-13 Blaník glider that we’re going to make in

1/48 scale, it’s quite easy, we just drive the

scanner to our nearby airport.

However sometimes museums’ aircraft need

some repairs or are missing parts. And in

some cases, the newly fitted parts aren’t

exact replacements of the original parts.

Of course, we don't want to include something like that in a 3D design. This is not to

suggest that museum technicians have done

a bad job. They are often in a difficult situation because original parts are scarce and

documentation for a given part of the aircraft

might be missing, and the complicated cur-

February 2023

ved shape of any specific part is sometimes

hard to deduce from historical photographs.

We are also in the same difficult situation if

the production documentation or the aircraft

in its original condition is not available or is

only available in partial form. In this case

we study historical photographs, wreckage

images, surviving aircraft parts and drawings prepared by aviation researchers. The

result is our best interpretation, which is based on the current state of knowledge.

This is a demanding discipline. The quality

of the documents, including publication drawings, changes over time. If someone was

preparing a kit for a particular aircraft, say,

thirty years ago, they had different documentation than we would have in our hands today

while working on said aircraft. And in another ten or twenty years, knowledge of the

type will probably be a little more improved.

It is therefore important to approach kits

produced in the past with a certain tolerance and detachment. They can usually be used

to build a beautiful model. Last week I saw

a very nicely built ARII 1/48 Ki-61 Tony. This

kit was produced in 1972 and has a beautifully riveted surface. Some of my favourite

pieces from this period include the Ki-43 or

Ki-45 from Nichimo. In the half century since

their creation, new information about these

aircraft has probably come to light and today

the designers of these kits would possibly

design some parts in a different way. But

I don't think that's important. They are just

beautiful pieces.

But it’s a bit of a digression from my consideration of the progression of knowledge

over time. I would like to mention the relativity of the validity of the research materials. They often contradict each other to some

extent. The production documentation may

not correspond exactly to the condition in

which the aircraft left the factory. The point

is that there may have been changes during

the manufacturing process. Manufacturing

jigs may have been modified, some details of

the aircraft may have been changed and the

original documentation no longer reflects

the production details. Even a 3D scan of an

aircraft that is preserved in its original state may not be completely accurate. If it is an

aircraft that has been in service for a long

time, it has usually been through a lot. I'm

thinking of hard landings, small accidents or

even crashes and subsequent repairs. The

plane is not made of diamond, but of metal,

possibly even wood and canvas. A hard landing can cause deformations, for instance

the rear half of the fuselage to be moved up

a few degrees from the longitudinal axis of

the machine. Nothing special for the pilot.

An extra worry for the kit designer.

So, even with ideal research materials for kit

design, there are situations where they contradict each other. So ,a kit at a certain scale

is not only a scaled down version, but almost

always the result of various compromises.

If we have to make them, we try to make them

as best as we can.

As colleagues from previous generations

did before us and, hopefully, as some others

from the next generation will do after us.

Jan Bobek

INFO Eduard

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