next meeting - Duncan Flying Club

Newsletter for October 2015
Note from the Editor...
Well, Fall is officially here. We’ve already had a
few chilly days, and there is certainly more to
come. I read an article today that a plane in Alaska
failed to climb out of ground effect as the pilot
chose (yes chose) to not clear the frost off of their
wings before attempting to depart.
I was chatting with someone the other day about
owning an airplane. The classic comparison
inevitably came up, how boats are holes in the
water you throw money into. After the compulsory
chuckles, we started looking into the comparison a
bit further. After weighing things like safety and
trust in our machines, we decided that airplanes
were more like owning/operating a submarine
where there is much less room for error
(mechanical or operator/pilot). We can’t simply pull
over (car) or sit bobbing (boat) and wait for help to
come to us, we need to be pro-active, and that
starts when we get to the airport, or even before
we leave the house in some cases.
There’s an article coming up in a future newsletter
about this in detail, but hopefully this gives you
something to chew on in the meantime.
Gary, Sam and I have started a new round of
ground school on Sundays, remember that DFC
members are welcome to attend at no charge to
brush up on anything you may have grown a bit
rusty on. This brings 5-6 fresh new faces to our
airport and club, let’s all make sure we help them
to feel welcome.
In This Issue...
Note from the Editor
Turbulence
Contacts
Pg. 1
Pgs. 2-4
Pg. 3
** NEXT MEETING **
Wednesday, Oct. 7th, at 1900 hrs
Photo of Doug Mackenzie's Aerostar
Doug and his father were both DFC members in earlier
years. The Aerostar was based at CYCD as take off &
landing were a little trick on our short strip.
They also had, I believe a 172 that was based at DFC.
- Keith
Please enjoy the article on the
following pages “Turbulence” from
Alex Burton, a fellow instructor and
pilot examiner from the mainland.
Blue Skies - Steve
Duncan Flying Club - 5100 Langtry Road - Duncan, B.C. V9L 6R8 - http://www.DuncanFlyingClub.org
Turbulence...
Air turbulence is something all pilots deal with from
time to time. Pilots who choose to learn its causes,
how it manifests itself, and the types of situations
which produce it, are more likely to make positive
decisions and take the necessary steps to ensure
a safe and enjoyable flight.
The type of flying a pilot engages in will certainly
influence his or her decision-making process with
regard to flying in turbulent air. A commercial pilot
may well determine it is safe to fly in conditions
that a private pilot flying for pleasure will dismiss
as unnecessarily uncomfortable. As an instructor
and pilot examiner,
much of my flying
involves training or is
conducted in training
like conditions, so
decisions are based on
the training environment
presented by the
current weather in
relation to the particular
student’s needs and
level of skill and
experience. All pilots,
however, benefit from
knowledge about and
an appreciation of the reality of the conditions they
will face on any given day. A well-grounded
understanding of turbulence, its causes and its
effects assists in good decision-making for any
given flight.
turbulence is a very common occurrence and is
generally described as producing momentary
slight changes in altitude and/or attitude. Pilots
and passengers may feel a slight tightening of
their restraints; those prone to airsickness may
want to find a horizon to keep focused on. In light
turbulence, particularly in the summer when it’s
hot, I’m particularly careful to keep an eye on
beginning students with limited flight experience. If
the person sitting next to you in the cockpit starts
to become very quiet, it may mean they are no
longer enjoying the ride.
In moderate turbulence,
pilots and passengers
will experience a
definite tightening
against their restraint
systems. Loose objects
in the cockpit may begin
to move about, and
airsickness can become
a real likelihood. The
transition from light to
moderate turbulence is
not a clear-cut point, but
now the fun level is
definitely decreasing
rapidly. Pilots may well notice a silence descend
over their passengers and would be well advised
to keep checking on how those passengers are
feeling. Flying is now becoming a bit of work rather
than a relaxed afternoon checking out the scenery.
Turbulence is an irregular movement of air
resulting from eddies and vertical currents. It is a
very difficult weather event to predict and can vary
from a mild irritation to a life-threatening situation.
And, conditions can fool us, easily. How many
times have we set off in what appeared to be nice,
calm conditions only to find ourselves crashing
and banging about at altitude, thinking it might be
more fun sitting back in the coffee shop telling
lies?
Severe turbulence can produce considerable
changes in attitude, altitude, heading, and
airspeed. We are definitely not having much fun,
now. At moments, control of the aircraft may pass
from the pilot to the weather; pilot and passengers
will be thrown violently against their restraint
systems. Any unsecured articles in the cockpit or
baggage area will be on the move and may
become quite dangerous to people and the aircraft
itself.
Turbulence is classed according to its severity as
light, moderate, severe, or extreme. Light
Extreme turbulence is a situation none of us want
to experience first-hand. During extreme
Duncan Flying Club - 5100 Langtry Road - Duncan, B.C. V9L 6R8 - http://www.DuncanFlyingClub.org
turbulence we can expect violent changes in the
aircraft’s attitude, altitude, heading, and airspeed.
Control of the aircraft may become impossible;
structural damage may occur. Conditions of
extreme turbulence are certainly to be avoided by
all general aviation pilots, no matter how bold, and
by all but the very few, commercial and military
pilots who specialize in this type of flying.
Turbulence arises under four types of conditions or
situations. Mechanical turbulence is produced
when air passes over the ground, particularly
irregular ground, and man made objects. As the
moving air passes over objects, the airflow is
disrupted and eddies and vertical movements are
produced. The harder the wind blows the more
disturbed air will become. Mechanical turbulence
will, of course, diminish with altitude and with
distance, both vertical and horizontal, from
geographic features.
I find it helpful to use the image of a river to
understand mechanical turbulence. Air is a fluid,
like water, and behaves in a very similar manner.
Water flowing over an irregular streambed at high
velocity will kick up quite a ruckus. As the fluid
passes over and around obstacles, turbulence is
created. The farther you are vertically or
horizontally from an obstacle, the less you will be
affected by the turbulence it produces.
As the wind picks up, the experienced pilot will
avoid, in particular, the downwind or leeward sides
of hills and other barriers. He or she will learn to
visualise the airflow around terrain features and
anticipate where turbulence may be most likely
expected. Moving air meeting an abrupt slope, for
example, can be expected to produce turbulent
up-drafts. An experienced pilot may well opt to use
a higher altitude, particularly over uneven or
irregular terrain, remembering, of course, that the
velocity of the wind will tend to increase with
altitude. Often, some experimentation with altitude
will lead to increased comfort.
In mountainous areas, mechanical turbulence can
become very significant. Flying in mountains,
particularly below higher terrain, is a complex topic
and any pilot contemplating this type of flying is
well advised to seek out an experienced person
who can provide a through checkout. Pilots with
experience flying in the mountains learn to be very
alert as the wind increases.
Thermal turbulence is a result of differential
ground heating. Various ground surfaces are
affected differently by the radiant energy of the
sun. Uneven terrain, for example hills and valleys,
will produce areas of shade and direct exposure to
the sun’s heating causing convective currents of
differing magnitudes. The hotter the day, the
greater is the intensity of the effects.
Thermal turbulence is, like mechanical turbulence,
most severe at lower altitudes. Thermal turbulence
is a common occurrence during the warmer
months of summer and can result in some
interesting experiences during landing and take off
when we are operating aircraft in close proximity
to the ground and at low airspeed. I still chuckle at
myself remembering my first trip to the
Sacramento Valley in California one summer.
Trying to get the aircraft to touch down over
tarmac heated to something like 60 to 70 degrees
C was an interesting adventure!
Frontal turbulence is produced along the interface
of moving air masses. As warmer air is forced up
and over cooler air, friction between the two air
masses creates a zone of turbulence that can vary
from light to severe or even extreme in the event
of thunderstorm production. Frontal turbulence is
most often associated with cold fronts, but can be
produced by warm fronts, as well.
A good weather briefing before any flight is an
important part of preparation. Changing weather
systems and moving fronts can present
challenging flight conditions. A very high
percentage of aircraft incidents and accidents list
weather as a contributing factor, so knowledge of
the expected meteorological conditions along a
planned route of flight can greatly assist a pilot in
decision-making regarding the route, altitudes and,
indeed, whether a particular flight is safe to initiate.
Wind shear, a shift in wind direction or velocity at
altitude, can produce significant turbulence. At
Duncan Flying Club - 5100 Langtry Road - Duncan, B.C. V9L 6R8 - http://www.DuncanFlyingClub.org
high altitudes clear air turbulence can result along
the margins of the jet stream and can be a severe
hazard to aircraft. At lower altitudes, where many
of us spend our flying time, changing weather
systems can often produce significant wind shear
effects.
These effects can be particularly dangerous during
take-off and landing when we are operating low
and slow. Unfortunately, wind shear is not easily
observed or predicted, and, for the most part, we
must rely on pilot reports. The poor fellow who has
just experienced wind shear and reported it to FSS
or ATC may be our only way of knowing that wind
shear is a present hazard.
The significant danger of wind shear is the abrupt
change in wind speed and/or direction. Although
the movement of the ambient air mass in which an
aircraft operates does not affect the aircraft except
in terms of ground speed, abrupt changes in that
movement certainly can.
Abrupt horizontal changes in wind speed can
affect an aircraft’s airspeed. During landing and
take-off when we are operating at a low airspeed
an abrupt change of 15 to 20 knots can be critical.
Vertical changes in wind can also produce
potentially dangerous effects by changing our
angle of attack and wing loading. A sudden gust
from below can result in a stall by drastically
increasing our aircraft’s angle of attack. A sudden
gust from above can result in a stall by drastically
increasing our aircraft’s wing loading.
affects.
In 1901, Wilber Wright wrote, “If you are looking
for perfect safety, you will do well to sit on a fence
and watch the birds; but if you really wish to learn,
you must mount a machine and become
acquainted with its tricks by actual trial.”
Knowing your aircraft, its systems, and its
limitations; knowing and having an honest
appreciation of your own abilities and limitations
as a pilot; making a study of weather and how it
can effect the safety and comfort of flight; ensuring
you have an up to date and current weather
briefing before flight, and
developing positive decisionmaking patterns are all factors
which help make flying a
successful and enjoyable
experience.
Alex Burton BA, MSc, ATPL
Flight Instructor; Pilot Examiner; Author
Coastal Pacific Aviation
Abbotsford, BC
If you enjoyed reading this post, you might like to
check out my book, "Flight and Flying Volume 1,"
published through Amazon in paperback and
Kindle versions:
If a pilot is aware of potential wind shear, steps
can be taken to reduce its danger. Increasing
approach speed and increasing alertness to any
changes in airspeed and attitude can be very
helpful. Being prepared to take immediate
corrective action is also useful. Of course, we
would always choose to avoid situations with
known, dangerous wind shear, for example the
neighbourhood of thunderstorms.
Turbulence is part of the reality of our weather
systems and part of the reality of aviation. It is
important for pilots to understand turbulence and
to have a good grounding in its causes and
Duncan Flying Club - 5100 Langtry Road - Duncan, B.C. V9L 6R8 - http://www.DuncanFlyingClub.org
Used by permission of Gary Clark www.swamp.com.au
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