IFR Precepts
--You cannot fly IFR without instruments.
--The inner ear is accurate only when supported by visual reference.
--Disorientation may take less than 20 seconds.
--IFR risk cannot be eliminated but it can be reduced.

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 strange 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.

Example:
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 an level below you. Avoid the temptation to dive.

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 ground.

Narrow Runway
A narrow runway can create the illusion of a high approach. Narrower and shorter than familiar runway will give illusion that you are higher than you are. Excess speed is most common problem. Fly the numbers and avoid straight-in arrivals. Prepare for go-around, do it earlier than usual.  The AIM Chapter 8-1-5 states that the pilot who does not recognize this illusion will adjust his perceived approach path to fly lower. 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.

Wide Runway
The illusion associated with a wide runway causes the risk of flaring rather high above the runway with a hard ground contact to follow.

Down Slope Runway
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 predict 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.

Variable Visibility Approach
If, while on approach, you should suddenly enter an area of 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.

Rain
Rain gives the illusion of being higher than you actually are. Combined with haze you will fly lower approaches during rain.

Creating Graveyard Spiral
Have student close eyes, head forward. Have student try to hold aircraft level. In a few seconds a slight bank should occur with a gradual increase. There will be a gradual descent, an increase in airspeed, and an increase in bank angle. Effort of pilot to correct these will only make them worse.

Creating Autokinesis Illusion
Cover or darken panel. On a night without either moon or stars, fly toward a single light. Have student stare only at that one light. After a while the light will appear to move. Student should try to keep the light in one place. Aircraft control will be lost.

Creating Elevator Illusion
Caused by quick upward acceleration as in updraft. Climbing sensation causes dive reaction. Could be caused by downdraft which results in climb reaction on controls.
Simulation:
Eyes closed. Make 90-degree turn with very slow bank entry from level into a 50-degree bank attitude. Student should have illusion of a climb. This same illusion can occur when caught in updraft. A sudden downdraft can give illusion of dive even though aircraft remains in level attitude.

Creating Corollas Illusion
Caused by abrupt head movement during a constant rate turn that has existed long enough to stabilize the inner ear. Gives sensation of motion on another axis. Attempts to correct
Simulation:
Eyes closed, head down and tilted (Cover AI). Enter extended constant rate turn until student no longer senses turn and bank. Have student make sudden head movement to instruments and open eyes. Student should sense rotation on another axis. May react to dangerous flight attitude.

Creating a False Horizon
Results from cloud formation that slopes. Problem can be made worse by angled road lights or light patterns. Pilot thinks horizon is out of level and attempts to align with illusion. Dangerous attitude results.
Simulation:
Eyes Closed or under hood. On a dark and hazy night fly diagonally across a freeway where other lights are infrequent. Light pattern could pilot to react with dangerous flight attitude. In IFR conditions this will occur as you break out of a solid ceiling.

Creating Inversion Illusion
Caused by abrupt change from climb to level flight. The pilot senses that he is falling backwards. The instinctive response of lowering the nose only makes the sensation worse.
Simulation:
Eyes closed. Have pilot enter and trim for climb. When senses have had settled, have student push yoke forward to nose low attitude while opening eyes. The pilot should sense feeling of going over backwards.

Creating the Leans
Eyes closed. Enter a bank so slowly that it might not trigger the inner ear motion senses. Once into the bank, make an abrupt correction. The student will react to his mistaken senses then by re-entering the previously created bank and will remain there.

Lighting Illusions
Pilot mistakes roadways for runways. Give illusion of being quite close when lights are bright. High approach results. 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.

After MDA the lights at the airport get brighter. Illusion is that you will fly right into the lights.
The normal tendency is to fly low when you can't see how high you are.
The more up-slope the runway the lower you must be to appear on the approach slope
The combination of up-slope and lights makes the situation even worse.
A down-slope will tend to make you high and fast. With lights illusions may cancel each other.

 Rain Effect
The curve of the aircraft windshield when impacted by sufficient rain will give a frosted-glass look from the interior. Heavy rains are accompanied by turbulence, downdrafts and wind shear.
All navigation aids except possibly GPS can be affected by heavy rain. Visual illusions that can occur require the pilot to pay close attention to altitude, rates of descent, and aircraft attitude.
Rain greatly increases the noise level in the cockpit and can make all communication difficult.

Illusions from the rain-covered windshield can lead the pilot to believe he is high on an approach. The illusions are of several types such as having a halo around a light, a runway appearing much shorter than usual or erroneous distance decisions since things seem further away. Approach lights appear lower. In general, illusions make you believe you are higher than you actually are, further away than you are actually are, and lights larger but not brighter. If this is a familiar airport your preconceptions are very dangerous when in conflict with these illusions. Reliance on aircraft and navigational instruments are the only safe recourse. Accept the fact that going from instruments to visual reference in rain is the most accident-prone region of IFR flight.

Simulation
Under the hood have pilot turn toward a TV tower while looking at compass. Will cause illusion of climb/descent situation that does not exist.

Vertigo
--90% of vertigo related accidents are fatal.
--Vertigo occurs when what you see, feels wrong.
--The three orientation systems of our body are in conflict as to what has happened and where we are.
--When the three systems are working in conjunction we are comfortable and oriented.
--We are up to 80% dependent upon our eyesight.
--Our vestibular (inner ear) system gives us upright, turning and velocity change feelings.
--Our 'butt feeling' is called kinesthetic and gives a sense of gravity.
--Vertigo can be of two types, (1) you are unaware of any disorientation, and (2) when you are aware.
--You first must recognize the existence of confusion typical of vertigo.
--Once vertigo is recognized, the cure is to force yourself to believe your instruments.
--Believe your instruments but verify that all are operating properly.

Spatial Disorientation
--90 percent fatalities when accident occurs
--VFR into IFR most common cause
--Then comes flight in marginal VFR
--Number three is loss of vacuum pump
--Last major cause is vertigo

Why?
--Eyes will believe what your eyes are preconditioned to see
--A slow vacuum pump failure takes about two minutes to be noticed and results in 80 percent fatality rate.
--Declare an emergency
--Request direct to nearest VFR or do it on your own.

Continued on IFR Radio Procedure

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