50
GA
/ Vol. 5 / No.4 / APRIL 2013
I
t's a really good idea that any air-
craft manages to complete a whole
flight without hitting any other
aircraft.
To achieve this: while the airlines
and to some extent the military can
rely upon instrument rules, primary
and secondary radar, and systems
such as TCAS to avoid other traffic,
in reality that's not enough for the
vast majority of VFR traffic, and
even for IFR traffic at lower levels in
VMC. There's always something, or
somebody, which can ruin an aircraft's
day large birds, ultralights, stray
balloons, lost gliders any of these can
appear very quickly, in either controlled
or uncontrolled airspace and lookout
is an essential skill for any pilot.
There are reports out there which
say that see and avoid is largely
ineffective and a waste of time; on the
other hand, certainly my experience
is that during most VFR flights, at
some point, I will see numerous other
aeroplanes, and usually change my
course or height once or twice to
avoid conflicting with other traffic,
and I don't think that I have any
monopoly on good eyes or good
practice. So seeing and avoiding
matters which first means seeing.
But, it's worth asking when
somebody sees another aircraft, or
some birds, or a balloon what do
they actually see? Unless it's very
close, they don't see the colour,
they don't see the shape they see
a contrast. So something large, but
of a similar colour density to the
by Dr Guy Gratton
Aircraft Technical
background, is very hard to spot.
Look at the picture I've shown here of
a sonde balloon it's big, it's close to
the camera, and you'd really struggle
to see it because it's so similar in
colour density to the background.
This is exactly why modern military
aeroplanes are also painted in very
neutral colours throughout this
makes them extremely hard to spot
far harder to spot than the broken
patterns of older military aeroplanes.
So first we can help make
sure that everybody else can see us
by painting our aircraft in colours
that depending upon the main local
backgrounds, are either as light,
or as dark, as possible. Companies
who really think hard about this will
often paint the underside as dark as
possible, and the upper surface as
light as possible particularly with
the colours changing partway up the
side of the fuselage; then, it's pretty
much guaranteed that there will be
a contrast against any background.
Of course, that helps other people
spot you but how do pilots do a
good job of spotting other traffic
whether it's winged, feathered, rotary,
or just floating there? Well looking
straight out of the front window
doesn't help a pilot much unless
they're "lucky" enough that your
traffic is on a perfectly reciprocal
course. Of-course, we have pretty
good peripheral vision as human
beings from about 110 degrees
either side for a young woman,
down to a still good 80ish degrees
either side for a man in his 60s, but
the structure of the eye is such that
peripheral vision is only really good
for picking up motion and if you
want to pick up things that you're
going to hit, motion isn't there. Try a
quick experiment to prove this: hold
a finger up at arm's length to one
side of you, then move your finger
in a straight line to a point a foot or
so in front of your nose. You'll find
that you pick up the finger in your
peripheral vision quite easily, and
as your arm keeps moving, you can
track the movement quite easily.
Now put your finger out at arm's
length again, and move it in directly
towards your nearest eyeball. You
won't see the finger easily until it is
very close, and even then, it will be
really hard to detect the movement.
Now do this a third time, but put your
finger right in front of you and look
at it as you bring it to your face the
shape and movement of your finger
now become very clear although it
is stationary in your field of view.
So, to detect an approaching
finger, sorry: aeroplane, you need to
be looking pretty much at it. And the
same is true for any pilot: if they're
going to spot that conflicting traffic,
they need to be looking at it when
it's close enough to make out the
contrasting shades. So pilots are, or
at-least should be, trained to move
their heads regularly typically six or
eight directions around them, moving
their head to look in that direction
holding the head still, and pausing
to pick up anything that's out there.
(Incidentally, if you've ever met
any fighter pilots, they usually have
necks like rugby forwards. Think
about doing that sort of move with
your head, for most of a flight, whilst
wearing a helmet, and pulling high
g constantly whilst you manoeuvre
and you'll start to realise why.)
So pilots can have a good go at
this but aircraft designers really
don't help as they often make
windows smaller than is ideal, and
also put large pillars between the
windows and doors. Any obstruction
such as a pillar, need to be narrower
than the distance between the pilots'
eyes: if it's the same width or wider,
then there will be gaps behind it.
Unfortunately, most aircraft designers
aren't pilots, and the majority regard
human factors of any sort as an
afterthought, so tend to surround
aeroplane and helicopter cockpits
with blind spots. Thus, the sensible
pilot not only needs to keep turning
his or her head (especially her, as
women's eyes tend to be slightly
closer together), but also need to keep
moving their heads around to ensure
that all these obstructions don't
create any permanent blindspots.
Which is very hard work
moving the head around like that
constantly, perhaps for hours for a
long low level flight, is physically
and mentally demanding. It needs
practice, and for the vast majority of
time of-course, the crew won't see
anything. But any helicopter pilot,
any light aircraft pilot, and any other
pilot or crew member who spends any
significant time in a cockpit, in VMC,
below 10,000ft or so: absolutely
needs that skill and obsession.
And whilst doing all of that
they of-course still need to operate
the aircraft, navigate, co-operate,
and all of the other skills that are
part of the pilots skillset. Not
easy, but always necessary. ·
Seeing to avoid