VISITORS IN 2018
Newsletter January 2018.
Next meeting Thursday January 11.
7:30pm, Blair Field Clubhouse.
I went up to the airstrip on January 4. It was minus 4
degrees. I wanted to ensure that the trailer door can be opened; it can!
So, no problem there.
Next, the furnace. It was slow to start, but then it produced
lots of heat. I let it run for 15 minutes.
Then the generator did not want to start right away, but finally
did and I let it run for 15 minutes too.
Some of the snow has been cleared, so we have parking space.
So: we have access, heat and light. I will get there early to
make sure it is comfortable for the meeting.
See you there!
In the meantime, if there is a big snowfall making it impossible
to go, I will try to let you know.
I installed counters to see how many visitors were looking at
this website. In December we averaged over 200 visits per day on the Buy&Sell
section, not too bad! For the past week we are already at 1280.
By Dan Thomas
Angle of Attack
One of the most
important aspects of aerodynamics is also one of the most misunderstood or
underemphasized in flight training. This lack of knowledge leads to numerous
accidents, many of them fatal. Let's review Angle of Attack and how it can cause
grief to the unwary.
Angle of Attack (AoA)
is the angle at which the oncoming airflow meets the chordline of an airfoil. It
governs the amount of lift a wing generates at any given speed: more AoA means
more lift, but only up to a certain angle, beyond which the airfoil stalls and
the lift largely disappears. You know that in level slow flight the nose of the
airplane is high, indicating that the wing is at a much higher AoA than it was
when you were in level cruise and the nose was much lower. The wing needs both
airspeed and AoA to generate lift, and if we have less speed we need more AoA.
This is simple enough, right? Until, of course, we ask for too much AoA and the
air can no longer make the turn downward over the top of the wing and it breaks
free and turbulates and the low pressure is lost. We've stalled it.
One of the ways we
get into trouble is when we start adding load factor, or G -loading. Students
are taught that load factor increases in a turn, as centrifugal force is added
to gravitational force. The normal 1G turns into 1.06G in a 20-degree bank, 1.31
at 40 degrees, 2.0 at 60, and 5.75 at 80 degrees. You can see that it isn't a
linear relationship. The stall speed goes up by the square root of the increase
in load factor: a 40-degree bank will increase the stall speed by 1.144 and a 60
degree bank by 1.41. An airplane that stalls at 55 will stall at 63 at 40
degrees and 78 at 60. This is the reason why your training taught you that you
should bank at no more than 30 degrees in the circuit, where the stall increases
by about 1.08. Your stall speed of 55 increases to a little over 59, safe enough
if you're doing 80.
But we can add load
factor in other ways. Almost every manoeuver we make will increase AoA and
therefore load factor. The one that lowers it is pushing forward on the stick,
as you change the flight path downward with respect to the airplane. And that's
a temporary change; the loading returns to normal once the airplane is
established in straight-line flight again, whether that is climbing or
descending or level. A steady descent is essentially 1G, contrary to many
opinions. So is a steady climb.
Newton's First Law
of Motion: Every object will remain at rest or in uniform motion in a straight
line unless compelled to change its state by the action of an external force. It
takes force to change the flight path of an airplane, and the more rapid the
change, the more force required. In an airplane, that force comes from the wing.
Picture the guy that
buzzes his friend's place and pulls up hard to get that impressive climb. All
too often this turns into an accident. The airplane is seen to pull up and
rather suddenly dive into the ground, sometimes dropping a wing as it goes. The
pilot pulled hard enough to get a load factor that increased the stall speed to
something beyond his airspeed and got an accelerated stall. Those tend to be
violent. If he was doing 90 and pulled hard enough to get 3Gs, his stall speed
of 55 went to 95 and the wing suddenly gave up. If he introduced a turn as he
pulled up, he added that into it, too, and even some speed over 100 wasn't good
enough. The yaw will also add a spin. Don’t forget that airspeed immediately
starts dropping in such a maneuver, too, bringing the stall closer.
The usual comment
recorded after such an accident: "I don't understand. He was such a good pilot!"
No, he wasn’t that good. His knowledge was deficient.
One more: The
dreaded base-to-final stall/spin. This one happens at or near 1G, but another
AoA factor is at fault. Remember the definition of chordline: it's the line that
runs though the leading and trailing edges of an airfoil. If we lower a flap or
aileron, we have moved the aft end of that line downward. Moving it downward
changes the AoA, which is why the airplane flies nose-low when the flaps are
down--we need to keep the AoA at a safe angle. Moving an aileron down increases
the AoA over the span of wing associated with the aileron; remember the
instructor's admonition to keep the ailerons level when recovering for a stall,
using rudder only? Many Cessnas are somewhat tolerant of aileron misuse in that
situation due to their washout and differential aileron movement, but go buy an
older design and it won't forgive you so easily. If you are turning base to
final and see that you are overshooting the runway centreline, DO NOT add rudder
while holding up the inside wing with opposite aileron. Keep the turn
coordinated and get back on centreline, or add full power and abort the
approach. Adding rudder to tighten the turn and using opposite aileron is
causing a skid, and there are several factors there that can quickly lead to the
stall-spin, one of them being that lowered aileron increasing the AoA to stall
angle when the airplane got too slow, and it will get slow because of the drag
of the skid and the nose will want to drop. The pilot will pull back to lift it,
and now we have all the ingredients for a nasty stall/spin: yaw, skid, and low
When I was an
instructor I most enjoyed the taildragger checkouts in the Citabrias. It was fun
to see the students, who usually had a fresh PPL and were thinking pretty highly
of thir skills, suddenly find out that their feet weren't so smart. Anyway, if I
saw them start skidding the turns in the circuit, we'd break off and go out to a
safe altitude and skid a couple of descending turns, letting the airspeed decay
some. It would suddenly drop the inside wing and roll over into a spin and we'd
need 800 feet to recover even though we knew it was coming and used the right
control inputs to recover. Doing it at 400 feet in the circuit while neither
expecting nor recognizing it results in a large, painful and expensive hole in
the ground. My students didn’t skid their turns anymore after seeing what could
From Dan Oldridge
Hello fellow KWRAA members and friends,
The January issue of The Leading Edge is now available on the
In this issue I have included a number of photos taken by Lee Coulman and a
description of a visit Lee and I had to the Rotax distributor, Rotech Research
in Vernon, BC in December. There is also a copy of a Letter to the Editor Lee
sent to COPA in regard to ADS-B and the direction currently being taken by COPA,
Nav Can and Transport Canada.
You can access the newsletter directly at:
From Paul Parsons
You can always go around!
From Jan Nademlejnsky
181. Short Cold Flight over South Ridge and
Dec 23, 2017
It was cold, -12C, but beautiful and sunny day.
Had to hand shovel snow to get from the hangar to taxiway. I used to fly down to
-25C, but my ultralights were slow to max 50 km/h. -12C at 110 km/h feels very
cold especially on the face and my fingers. There is an opening in the front
bottom of the pod to accommodate the steerable front wheel. This creates serious
and concentrated draft directly into the face, which is very unpleasant. Even
the microphone wind screen sponge froze solid from my steamy breath. I had to
raise my voice to penetrate the ice.
Overall it was very good flight. Actually, by
default, the flying in winter is more pleasant then in summer, because usually
there is no turbulence to worry about.