Recovery - It May Not Be What You Think!
While accidental entries into steep spirals are
unlikely for proficient pilots in VFR conditions, it
is a common problem with potentially deadly results
when a non-IFR rated pilot stumbles into hard IMC.
And when that unfortunate pilot responds
instinctively, the problem only gets worse.
What Is It?
An aggravated steep descending spiral is
an autorotation about an external vertical axis. It
differs from a spin in two primary and very
(1) Neither wing is stalled
(2) Airspeed is increasing
Shaped like a tornado, it is
characterized by increasing roll and downward pitch
along with a quickly growing airspeed. Unchecked, loss of
control and structural failure in flight are likely.
With good outside visual references,
it is generally difficult to accidentally enter a steep spiral. In
IMC, however, entry can occur slowly and undetected if you
aren't "on the gauges." Once the uncommanded spiral has
developed, it matters little if you have a view of the
earth. At this point, even in clear VMC, the
view can be disorienting and frightening. Imagine the sight
picture as your airplane rolls through 70 degrees of bank
and the pitch attitude seems nearly straight down. Now,
add an airspeed racing toward the red line to this image and
you begin to understand the full dynamic of this problem.
straight-and-level flight, the lift vector points
straight up, fully opposing the gravity vector. The
spiral starts as a gentle, unnoticed bank. As the lift vector
is redirected into the horizontal, the vertical
component of lift is decreased. Since the gravity
vector is unchanged, it wins the tug of war and the
banking airplane enters a shallow descent. Uncorrected
by the pilot, the roll and downward pitch continue
to increase, slowly at first. But as the bank goes
through 45°, the roll and pitch changes begin to
increase dramatically. Faster and faster,
steeper and steeper.
It's only now that the pilot realizes
the true severity of the situation. Something needs to be done
First action: cut the power. The nose
is low and airspeed is increasing so quickly pull the
throttle to idle. What comes next is the true deciding
The Wrong Recovery
With the nose alarmingly below the
horizon, instinct tells the pilot to pull back on the yoke
or stick. Early on, before the bank passes through 45°
(approximately), this may work just fine. But with excessive
bank angles, yanking back on the yoke compounds the problem.
At roughly 55° of bank, pulling the nose up produces an
arcing motion relative to the horizon. This is due to the
fact that the roll is continuing during the pull. Rather
than pulling back up into level flight, the pilot actually
pulls the airplane into a tighter, higher-G, descending
that's just the beginning.
The excessive G-forces required
in the pull raise the airplane's stall speed. When
the critical angle of attack is exceeded, the
airplane enters an accelerated stall while pointed
nearly straight at the ground with the airspeed
needle sweeping past the red line . . . assuming
that the aircraft has not already broken up.
Look at the numbers: At 75° of
bank, 4G of pull is required to offset the gravity
vector. At 90°, an infinite amount of force won't do
exaggerated bank angles, your
airplane can't handle the load, and even if it
could, you would transition into an accelerated
stall. Beyond 60° of bank, most pilots will be
physically incapable of pulling the airplane back into level flight.
The outcome is quite simple.
If you succumb to your instincts in a situation like
this you will become another statistic in the Nall
Report. The solution is to change your instinctive
The Right Recovery
Let's step back. The airplane is now
rolling through 50° and the nose is dropping quickly. You've
recognized the steep spiral and pulled the power to idle.
And the right recovery technique is SO very easy:
(1) If you've unconsciously pulled
back on the controls, release all back pressure.
(2) Roll the wings level
(3) GENTLY raise the nose
Rather than fighting the spiral, you
simply redirect the lift vector toward the sky and let the airplane fly
itself out. When the wings roll level, the vertical
component of lift increases. This produces an immediate
increase in pitch. By gently assisting the pitch up to
level, the lift vector once again fully opposes the gravity
vector. And you are in happy level flight.
|VFR flight into
IMC by non-instrument rated pilots is highly
dangerous. If you find yourself in this situation,
focus first and foremost on your attitude
indicator. You only need to line up two things:
the sky pointer and the
horizon line (as shown
in Step 2 and 3 above). With properly functioning
instruments and systems this guarantees that you are
in straight-and-level flight. One-G up versus one-G
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