flying and illusions
The FAA integrated mix of VFR and IFR instruction is a violation of the
very instructional precepts considered basic to flight instruction. The
purpose of the IFR instruction to a VFR student was an emergency process.
As such, it focused on the attitude indicator and the making of a 180-
degree turn out of IFR conditions. The basis of this instruction was upon
the inability of a VFR pilot to maintain control in IFR conditions for
much over a minute.
The basic 1959 survival turn was performed by reference to the needle with
any descent initiated by a slight reduction in power as by applying
carburettor heat. The yoke was released and a quarter-needle turn initiated
and stopped by rudder alone. Over the years this was changed into a
coordinated attitude indicator shallow bank along with turn coordinator
rate turn for one minute. Any time devoted to this detracted from the use
of VFR references outside the cockpit.
The hood should be fitted prior to engine start. Note that the attitude
indicator has both a wings level and a level index mark at its top. The
10, 20, and 30 degree bank marks have been pointed out during Dutch-rolls
and banks. A plane will not turn if the wings are level. This means that
whenever the heading indicator is fixed on a heading the plane is not
turning and wings can be considered level. Knowing this will enable you to
perform even stalls under the hood. When the attitude indicator is at
level, heading will be constant. Confirm this with the heading indicator.
The turn coordinator has the ability to show both the direction of the
turn and markings that index the 2 minute standard rate turn. The vertical
speed indicator will either indicate false or excessive movement under
abrupt control input and may have up to a 12 second lag. The altimeter
also may lag. The accuracy of the instruments is proportional to the
smoothness of any change. The use of sound indexes acquired from VFR
flight will help clue you in on airspeeds and changes.
Standard Rate Turns
All banks under the hood are at standard rate. Standard rate turns
requires two minutes to make a 360 degree circle. One minute for a 180 and
30 seconds for each 90 degrees. The standard rate turn for a given
airspeed is indicated by the needle or by the turn coordinator. The turn
coordinator is the only true indicator of whether the bank is left or
right. (A necessary check during spins) The angle can be estimated by
dividing the speed by ten and adding five. (Speed /10 + 5 = angle of bank)
85 knots airspeed divided by 10 is 8.5 + 5 = 13.5 angle of bank. Set the
estimated angle on the AI and check with the turn coordinator. All climbs
and descents are at one bar width on the attitude indicator. From low
cruise both climb and descent at a given rate will closely correspond to
RPM changes by 100's. A power reduction of 500 rpm gives 500 fpm descent.
In VFR condition at level altitude cruise the standard rate bank is
selected by using the turn coordinator. The degree of bank is NOTED on the
attitude indicator. This angle of bank becomes the standard to be used. It
is checked for accuracy by making successive timed turns of 90, 180, and
360 degrees. It takes 30 seconds to turn 90 degrees, one minute to turn
180 degrees and two minutes to turn 360 degrees. In a C-150 at cruise the
angle will be about 12 degrees. After timed turns are introduced at cruise
go to VFR slow flight and determine the angle of bank required on the turn
coordinator for above timed turns. The angle will be close to 10 degrees.
VFR to IFR Options
What to do? If you're on top, do the four C's. Climb, communicate,
confess, and comply. If fuel and weather limits your ability to find a VFR
escape route. Don't delay, find an area in which to descend to VFR below.
ATC vectors may get you to the area but you must know how to make a safe
decent. As a student the manoeuvres below should be a 'hood' exercise with
your instructor. Some practice now may solve a future problem by having a
pre-planned solution. Try it until you can do it. When the need for
performance occurs you can advise ATC of your ability to perform an IFR
climb or descent in a declared emergency.
One way follows. There are other ways. Pay our money and take your choice.
Assume that all instruments are functional. Get on a cardinal heading, C.H.
power to 2000 rpm, and trim for 60 knots. Let go of the yoke and hold
heading with rudder. Slowly decrease power to 1500 rpm and descend at 60
knots using only rudder. If the terrain below is completely unknown as to
cloud clearance and terrain elevation. Do the process with full flaps and
airspeeds as low as 45 knots. The worse thing you can do is a spiralling
If you are below a cloud deck with a known top attainable by your aircraft
and fuel remaining, initiate a VFR to IFR to VFR climb using much the same
technique as the descent. Well below the cloud base, initiate a 65-knot
climb and trim for hands off. Let go of the yoke and hold a cardinal
heading with only the rudder. Once on top you should know if an escape VFR
airport is within range.
Hopefully, you will never need an emergency option. You should practice
recognition of weather so as to initiate the 180 escape before it cant be
done. When the turn is only possible in IFR conditions you must know
enough to totally rely on your instruments. Any effort to mix IFR with VFR
is doomed to failure. Use the turn coordinator to limit the bank to a
standard rate. Better yet learn the amount of bank on the HI that gives
the standard rate for your airspeed.
You and Illusions
1) Illusions can and do occur to everyone
2) Proper planning for strange airport conditions is essential
3) Weather and poor visual conditions make airport conditions worse.
4) Rely on your instruments to help your sense perceptions
5) Maintain situational awareness, know where you are.
6) Use airport systems and lights for directional and slope help.
7) Your physical condition can make matters better or worse.
IFR Flying Faults
Initially, VFR to IFR flight results in over-controlling especially when
making corrections. Non-instrument rated pilots who fly into instrument
weather lose control in about a minute of level flight. The usual VFR
movements for climbs, descents, and turns are far too extreme for IFR
flight. One technique used to avoid over controlling on heading changes is
to use the AI to set the standard rate of turn. Count three, five, or six
at a steady rate. Level out from the bank using the attitude indicator top
index to level the wings and note the degree of change in the HI. Do this
several times until you can get the count needed to get 10 degrees
correction every time. Focus on the attitude indicator top index when
levelling off. This technique prevents the common fault of reversing the
bank back to nearly the original heading. This reversal is caused by the
beginner's inability to ignore the turning sense imparted by the fluids of
the inner ear. This problem is normal for the beginner but focusing the
eyes on the top index of the AI for a few seconds will give the inner ear
fluids time to lose their influence.
Beware of false sensations. Your inner ear will give you feelings that are
overpowering. With low time under the hood you must avoid attempting to
extend manoeuvres beyond just holding a heading or a standard rate bank.
Any more may exceed your skill capacity for aircraft control in IFR
conditions. Any tenseness will cause the inexperienced to over-control. If
you have learned to use trim well as a VFR student you may be able to trim
successfully for hands-off IFR flight. An aircraft trimmed for hands-off
in pitch can be flown in roll (heading) with just rudder input. Descents
are controlled by slow power reductions, only.
May cause nystagmus (trembling of the eyes) which makes reading of
instruments impossible. Rare but can occur in extremes of weather or
flight conditions. Other types of disorientation are illusions such as
caused by runway/cloud sizes, shapes, or slope.
Unrecognized spatial disorientation is caused by a combination of a
focused attention, distraction and instrument fixation. These most often
occur in companion with loss of situational awareness due to excessive
Recognized spatial disorientation is when the pilot is aware of his
disorientation. Being aware means that the pilot should be able make his
recovery with power and attitude corrections. Pilots have, over the radio,
acknowledged their vertigo and inability to overcome it prior to crashing.
Spatial disorientation is considered incapacitating when the attitude of
the aircraft is so unusual that pilot is unable to determine the cause,
organizing the instrument information, and making control decisions.
Vertigo is the #1 cause of Air Force fatal accidents. Vision
is the pre-installed vertigo preventative. A moments glance out-the-window
is all it takes. This will overcome any sensations from other sources.
However, without vision, the organs of balance in the inner ear take over.
The semicircular canals approximate the three axes. They contain a fluid
that stimulates our senses of angular acceleration in these axes. Our
sense of uprightness is done by the otolith organs. Tiny stones affect
hair sensors in reaction to "gravity". Otoliths sense linear
accelerations, not angular accelerations, and regardless of the direction
interpret such accelerations as gravity. In our muscles and joints we have
sensors that give additional information about push or pull. Unless one or
all of these sensors are confirmed by vision we are on our way to vertigo.
The simulation used for vertigo such as the Barany chair, the yardstick on
the nose, etc. in no way prepare the pilot for the real occurrence of
vertigo. Unlimited motion in all three axes as well as planetary motion
for acceleration are required. Even with these in place it is additionally
necessary to create a work overload. The instructor should expose the
student to simulations that closely approximate the real thing. That is
except for safety of altitude, configuration and airspeed. To train the
recovery the same forces and psychological pressures must be recreated
over and over by in-flight simulations.
What ever the illusion, it will take a few moments for you to get
reoriented. If the illusion occurs in trimmed flight the problem is not as
severe as it might be if it occurs during manoeuvres as it usually does.
Spatial disorientation caused by loss of horizon, change in power,
banking, or other acceleration forces can lead the pilot to believe that
the aircraft is doing something that it is not. These forces cause the
pilot's vestibular and proprioceptive system to give the somatogravic
A pilots first reaction will be to over-control in a direction exactly the
opposite to what should be done. The only safe procedure during the onset
of any illusion is to increase your instrument scan rate.
The brain is capable of separating out the conflict of information between
the eye and the inner ear when the eyes are looking outside the cockpit. A
conflict between the sensory inputs of the body can be overwhelmed when
the natural horizon disappears. When the conflict of information comes
with the eyes viewing relatively unfamiliar instruments inside the
cockpit, the brain can become confused and then give improper information.
This is the origin of an illusion. You must trust your instruments in IFR
conditions. (See IFR material)
Rain gives the illusion of being higher than you actually are. Combined
with haze, you will fly lower approaches during rain.
Low visibility can cause the illusion that things are further away.
Entering a fog during descent will give an illusion of pitching up.
An updraft can cause such vertical sensation as to cause the pilot to put
the nose of the aircraft down. He senses a climb where the attitude of the
aircraft has been level. Avoid the weather conditions that can cause
illusions. Believe your instruments. Get an instrument rating.
Illness, medicine, alcohol, fatigue, or hypoxia will make susceptibility
to an illusion more likely. It takes very little to cause disorientation
Runway and approach light illusions will always be a problem if you are in
an unfamiliar area. For this reason it is always desirable to make a
daylight familiarization flight to an airport before a first time night
arrival. Night has its own illusions that are covered in the night flight
lessons. The distance of lights is greatly affected by the relative
clearness and haze existing. A region of no lights such as might exist off
the end of a runway toward the ocean can cause disorientation because of
IFR illusions. The best solution is to go on instruments until established
inland at altitude.
If, while on approach, you should suddenly face reduced visibility you
will get an illusion of a sudden pitch up in aircraft attitude. Failing to
recognize this illusion will lead to an instinctive and abrupt descent in
the approach flight path.
Your ability to determine distance is greatly affected by haze. It is not
unusual to call a distance at over twice the actual distance. The sudden
appearance of bright lights during an a night approach through haze will
create the illusion that the airport is much closer than previously
realized. This results in a high approach.
If there is no VASI or VAPI for vertical guidance if you get too low the
runway lights will begin to disappear. A steep approach is always better
at night. An arrival at an airport with and approach lighting system (ALS)
tends to be lower and at a shallower angle than otherwise. Low approach
results when runway is approached over dark area. Don't use landing light
until close to ground. The visual cues used for a normal night landing
seem much the same as you get with a rapid increase in sink rate.
If there is a strong crosswind and you are crabbing to the runway instead
of slipping you will get the illusion of being inverted. If the airport is
well lighted in a surrounding dark area you will have an illusion of being
higher than you actually are. Again, a steep approach has much advantage.
Rain on the windshield will give the illusion of being higher than you
are. If you mistake roadways for runways. It will give illusion of being
quite close when lights are bright. High approach results.
If you are low and pitch the nose up as a correction or through the use of
flaps, the illusion will indicate that you are rising. Any reduction of
power will cause you to land short.
At night, banking into or away from a line of lights will give the
illusion that a dive or a climb is occurring. The same dive or climb
illusion can happen by a change in aircraft pitch occurs while flying
toward a light. A 10 degree bank with only the approach lights visible can
cause an illusion that the lights are sloping from above.
Lights that appear dim, as seen through haze, will be reported as more
distant than they are. Example: I once reported an airport as in sight
from twelve miles when the tower had me on radar at only five miles.
You and every other pilot is susceptible to illusions. when any of our
three flight senses (Visual, auditory and Kinesthetic) give erroneous
information out mind produces inaccurate information. Flying illusions are
most likely to occur at airports due to visual information.
Illusions do not cause accidents. Rather, it is a pilots reaction to the
illusion that precipitates an accident. The best way to overcome the
negative effects of airport illusions is with experience. Even the most
experienced pilot can be fooled.
Our three flying senses fool us by misinterpreting distances, velocity and
relationship. Vision is the number one creator of illusion. Over our life
time of living and flying we have learned that if two things are of the
same size and one appears larger it is nearer. If we know two lines are
parallel then when they appear farther apart that is the near end. As we
fly we learn an approach slope for our aircraft at our home airport. Our
brain has developed a data bank of how things are supposed to be at
airports. The terrain around the airport can also be an illusion creating
factor. Use all the electronic and visual (VASI) help you can get.
You should practice landings at airports of varying width. All too often
you become overly familiar with airports of a consistent length and width.
This familiarity interferes with your perception of an airport of
A narrow runway can create the illusion of a high approach. Once the pilot
realizes that he is low it is vital that full power be applied while
maintaining approach speed with yoke pressure. No trim changes. Once the
proper glide path has been intercepted the power can again be reduced and
the stabilized approach resumed.
The illusion associated with a wide runway causes the risk of flaring
rather high above the runway with a hard ground contact to follow.
The atmosphere can create illusions. Clear clean air makes everything seem
closer. Hazy or smog conditions makes things hard to see and apparently
further away. Note: Be aware of this when reporting distances at strange
airports. The effect of sunlight in creating shadows is an important part
of our visual data bank. At night these shadows are not there. The absence
of contrast and background at night is a major cause of night landing and
takeoff accidents. Precipitation will distort visibility through the
windshield and make to think you are higher than you actually are.
Our vision is the major source of our cues related to speed. However, much
of our speed information comes from our peripheral vision and is often not
consciously entered into the brain. The unfamiliar tangential velocity of
the ground passing by in a low level bank may appear so fast as to make us
pull back on the yoke without regard to the air speed. Stall-spin. This is
the classic sequence of the downwind turn from base to final. We have
learned to judge both the proximity and speed of a known object crossing
in front of us. Closer things seem to move faster.
We are all subject to illusion because we have come to expect certain
appearances to occur. When we are told to look for traffic, we expect to
see that traffic. If we don't see the traffic tension rises; if we see any
plane we have our expectation satisfied and we stop looking. We shouldn't.
The traffic we see does not have to be the same traffic we should be
Gives identical illusion as wide runway but is much more likely to cause
the pilot to over-shoot the runway. A runway sloping away will give the
illusion that you're low on the approach. A runway that slopes toward you
can give the illusion of height. One of the most difficult runways is the
one with a mound in the middle. This gives the worst of both illusions.
In landings where you project the possibility of illusions, it is vital
that you proceed with the landing using a standard procedure to establish
a stabilized approach. The making of predictable changes of power, flaps,
and trim becomes very important as the landing progresses. 'Winging' it
for changes in these approach elements means that you are subjecting
yourself to the effects of illusion. A pilot who fails to recognize
illusion is going to make changes as though what he sees is reality.
Any airport that differs from our experience because of runway dimension
shape or slope is going to give us an illusion. If a runway slopes away
from us our perception (illusion) will be that we are too low. If the
runway slopes toward us we will perceive ourselves as being too high. If
we react to the illusion we will find ourselves both high and long from
the anticipated touchdown point. A wide runway or one whose lights make it
appear wider will give the illusion of a low approach causing the pilot to
stay too high.
A 3 degree approach to an upslope runway and the illusion is that you are
high. The same upslope runway made narrower and you will find yourself
low. A down-slope runway creates a "low" illusion which can cause long
landings on short runways.
Pilots unconsciously make extensive use of their peripheral vision. Level
flight, banks, climbs, and descents rely 80% on peripheral vision. (See
downwind turns) At low levels our peripheral vision gives us a sense of
speed. Over time we develop a peripheral sense as to what "normal" low
level speeds are. Add a tailwind, low altitude, a bank to final approach,
and a peripheral sense of a "high" speed. We now have an illusion causing
a pilot response that says to pull back on the yoke to reduce the speed.
The pull merely makes the bank steeper and initiates a low level stall
spin. Recovery not possible.
A final approach over high terrain leading to the runway gives an illusion
of a low fast approach. An approach over terrain that makes the runway
seem like an aircraft carrier will give an illusion of too high and too
Black Hole Landing
When it is very dark you are subject to illusions. Your seat position may
make you more or less subject to these. Aircraft seats are situated by a
"Design Eye reference Point" (DERP) that is supposed to give a view over
the cowl and at the instrument panel. It is not marked on the aircraft but
is part of the aircraft design.
If your seat is too low during dark conditions, you will only be able to
see runway lights if you are in a descent. The pilot tends to set up a
constant angle for their field of view on approach. During daylight, you
use the "point on the windshield" to maintain this angle. If the aim point
drifts upward you are in an excessive descent; if it drifts downward you
are too high. It works the same at night but the references are fewer.
The black hole illusion begins out a few miles on final. The field and
lights will be foreshortened. Getting closer the runway should rise in the
field of view. If the aircraft is descending the foreshortened view will
remain constant. The eye/brain interpretation of this is that the constant
foreshortened runway is an indication of a constant angle approach. This
is the "everything is fine" illusion of the black hole. During the final
phases the daytime depth perception does not work very well.
When flying into a black hole or 'featureless terrain' you must use a
correctly set altimeter to counter the illusion. Fly a full pattern using
your altimeter and a standardized procedure for a stabilized approach.
This is the best way to assure yourself that you will not meet an obstacle
on final. This is a combined IFR/VFR approach and requires that you be
capable of controlling the aircraft accurately without visual references.
The normal order of viewing runway, lights, and dark areas is so changed
illusions of being higher occur. If the illusions are believed, touchdown
can occur before reaching the runway.
The "black hole illusion" has a dramatic effect on straight in approaches
to a runway. The stabilized constant angle approach will appear to exist
as an illusion while you fly an arc that flies you into the ground. Do not
fly a straight in approach to a runway at night. Know the pattern
altitude. Fly somewhat farther out on down wind than appears appropriate.
Use a standardized configuration approach just as you would in daytime.
Fly the VASI or VAPI if available.
Failure to follow the above recommendations may cause you to make a
premature descent. Over flying featureless terrain without lights on an
approach that deprives you of the height clues can fly you into the
There are some optical illusions that relate to nearby aircraft. An
aircraft below you will appear to be above you. While getting closer it
will appear to descend through your horizon. All the time it is straight
and level below you. Avoid the temptation to dive.
Only by knowing where and when illusions occur can the pilot expect to
anticipate their occurrence and focus on the instruments. The runway
length and width proportions can cause a high or low illusion. Wide, short
and down slope runways give low illusion. Long, narrow and up slope
runways give high illusion. Haze and mist makes runway seem farther away.
Bright lighting makes it appear closer than it is. Rain during the day
makes runway appear farther away.
When taking off in a black hole situation the acceleration, rotation and
nose up attitude during initial climb can cause a somatogravic illusion.
You will feel that the seat is being tilted back. The sensation is that
there has been a shift in gravitational pull. This causes an instinctive
reaction to lower the nose of the aircraft to counter the kinesthetic
sensed pitching up illusion. The power of this illusion is so strong that
only a determined concentration on the attitude indicator can overcome the
Another illusion is that of being higher than you are when on an approach
to a runway. This illusion is common for naval pilots approaching
carriers. Even though all instrument readings show on glide slope, the
visual picture is one of being very high. Rain on the windshield can cause
the same illusion. This 'being high' illusion is the main one that makes
night flying different than day flying.