Reference: AIM RAC 6.3.2.1 Two-Way Communications Failure:

Reference: AIM COM 8.3: INSTRUMENT FLIGHT RULES (IFR) OPERATIONS IN OTHER LOW-LEVEL AIRSPACE:

To enhance the safety of IFR flight in uncontrolled low-level airspace, pilots are encouraged to adjust their transponders to reply on Mode A, Code 1000 and Mode C (if available), unless otherwise instructed by ATC.

Reference: FTGU 11.1.9 Sensory Illusions:

If the head is held vertical but is subjected to acceleration, the hair bends owing to the inertia of the mass at the tip of the hair. Both tilt and acceleration, therefore, produce the same response by the otolith. If there are no visual cues to compliment the information from the otolith, the brain is unable to differentiate between tilt and acceleration. If tilt and acceleration are experienced simultaneously, the interpretation is that of a much steeper tilt. This is known as the somatogravic (false climb) illusion. In such a situation, a pilot is tempted to lower the nose of the airplane.

Reference: AIM MET 4.0 GRAPHIC AREA FORECASTS (GFA), Figure 4.4(f)- Weather and Obstructions to Vision

Ref: AIM COM 5.4.2 Global Navigation Satellite System (GNSS)- Based Area Navigation (RNAV) Approach Procedures & COM 5.4.2.2 Global Navigation Satellite System (GNSS) Overlay Approaches

A series of waypoints in a “T” or “Y” pattern eliminates the need for a procedure turn.

All approaches must be retrieved from the avionics database, and that database must be current. While it is sometimes acceptable to use pilot-generated waypoints en route, this is not permitted for approach procedures.

When conducting GNSS overlay approaches, the VOR, DME and/or NDB onboard navigation equipment does not need to be installed and/or functioning and the underlying approach navigation aids does not need to be functioning. Nevertheless, good airmanship dictates that all available sources of information be monitored.

Ref: FTGU 9.1.4 The VOR Station:

Always listen for the identification signal to be sure you have the right station. During periods of maintenance, the coded identification is not broadcast. If you cannot hear the audio signal, take that as indication that the facility may be unreliable even though the VOR signal is being transmitted.

Reference: AIM COM 4.10 INSTRUMENT LANDING SYSTEM (ILS):

LOC alignment exceeding 3° of the runway heading will have an “X” as the first letter of the indicator, whereas LOCs and back courses with an alignment of 3° or less will have an “I” as the first letter.

AIM COM 5.3.1 Aircraft-Based Augmentation System (ABAS)

RAIM and FDE functions in current IFR-certified avionics are considered ABAS. RAIM can provide the integrity for the en route, terminal, and NPA phases of flight. FDE improves the continuity of operation in the event of a satellite failure and can support primary-means oceanic operations.

RAIM uses extra satellites in view to compare solutions and detect problems. It usually takes four satellites to compute a navigation solution, and a minimum of 5 for RAIM to function. The availability of RAIM is a function of the number of visible satellites and their geometry. It is complicated by the movement of satellites relative to a coverage area and temporary satellite outages resulting from scheduled maintenance or failures.

If the number of satellites in view and their geometry do not support the applicable alert limit (2 NM en route, 1 NM terminal and 0.3 NM NPA), RAIM is unable to guarantee the integrity of the position solution. (Note that this does not imply a satellite malfunction.) In this case, the RAIM function in the avionics will alert the pilot, but will continue providing a navigation solution. Except in cases of emergency, pilots must discontinue using GNSS for IFR navigation when such an alert occurs.

A second type of RAIM alert occurs when the avionics detects a satellite range error (typically caused by a satellite malfunction) that may cause an accuracy degradation that exceeds the alert limit for the current phase of flight. When this occurs, the avionics alerts the pilot and denies navigation guidance by displaying red flags on the HSI or CDI. Continued flight using GNSS is then not possible until the satellite is flagged as unhealthy by the control centre, or normal satellite operation is restored.

Some avionics go beyond basic RAIM by having an FDE feature that allows the avionics to detect which satellite is faulty, and then to exclude it from the navigation solution. FDE requires a minimum of 6 satellites with good geometry to function. It has the advantage of allowing continued navigation in the presence of a satellite malfunction.

Most first generation avionics do not have FDE and were designed when GPS had a feature called SA that deliberately degraded accuracy. SA has since been discontinued, and new generation SBAS-capable receivers (TSO-C145a/C146a) account for SA being terminated. These receivers experience a higher RAIM availability, even in the absence of SBAS messages, and also have FDE capability.

Reference: AIM RAC 9.6.1

A contact approach is an approach wherein an aircraft on an IFR flight plan or flight itinerary having an ATC clearance, operating clear of clouds with at least 1 NM flight visibility and a reasonable expectation of continuing to the destination airport in those conditions, may deviate from the IAP and proceed to the destination airport by visual reference to the surface of the earth. In accordance with CAR 602.124, the aircraft shall be flown at an altitude of at least 1 000 ft above the highest obstacle located within a horizontal radius of 5 NM from the estimated position of the aircraft in flight until the required visual reference is acquired in order to conduct a normal landing.  Familiarity with the aerodrome environment, including local area obstacles, terrain, noise sensitive areas, Class F airspace and aerodrome layout, is paramount for a successful contact approach in minimum visibility conditions. Pilots are responsible for the adherence to published noise abatement procedures and compliance with any restrictions that may apply to Class F airspace when conducting a contact approach.

NOTE:
This type of approach will only be authorized by ATC when:

1. the pilot requests it; and
2. there is an approved functioning instrument approach, a published GNSS or a GNSS overlay approach for the airport.

Reference FTGU 6.9.2

Reference: AIM RAC 4.2.2

If the visibility drops below the published level of service (RVR/visibility) for the intended runway after you have started taxiing, you may continue to taxi but are not permitted to take off from that runway. However, you may take off from a different runway provided it meets the required level of service for the operation.

Reference: AIM 1.7.3 Minimum Fuel Advisory

AIM COM 5.3.1 Aircraft-Based Augmentation System (ABAS)

RAIM and FDE functions in current IFR-certified avionics are considered ABAS. RAIM can provide the integrity for the en route, terminal, and NPA phases of flight. FDE improves the continuity of operation in the event of a satellite failure and can support primary-means oceanic operations.

RAIM uses extra satellites in view to compare solutions and detect problems. It usually takes four satellites to compute a navigation solution, and a minimum of 5 for RAIM to function. The availability of RAIM is a function of the number of visible satellites and their geometry. It is complicated by the movement of satellites relative to a coverage area and temporary satellite outages resulting from scheduled maintenance or failures.

If the number of satellites in view and their geometry do not support the applicable alert limit (2 NM en route, 1 NM terminal and 0.3 NM NPA), RAIM is unable to guarantee the integrity of the position solution. (Note that this does not imply a satellite malfunction.) In this case, the RAIM function in the avionics will alert the pilot, but will continue providing a navigation solution. Except in cases of emergency, pilots must discontinue using GNSS for IFR navigation when such an alert occurs.

A second type of RAIM alert occurs when the avionics detects a satellite range error (typically caused by a satellite malfunction) that may cause an accuracy degradation that exceeds the alert limit for the current phase of flight. When this occurs, the avionics alerts the pilot and denies navigation guidance by displaying red flags on the HSI or CDI. Continued flight using GNSS is then not possible until the satellite is flagged as unhealthy by the control centre, or normal satellite operation is restored.

Some avionics go beyond basic RAIM by having an FDE feature that allows the avionics to detect which satellite is faulty, and then to exclude it from the navigation solution. FDE requires a minimum of 6 satellites with good geometry to function. It has the advantage of allowing continued navigation in the presence of a satellite malfunction.

Most first generation avionics do not have FDE and were designed when GPS had a feature called SA that deliberately degraded accuracy. SA has since been discontinued, and new generation SBAS-capable receivers (TSO-C145a/C146a) account for SA being terminated. These receivers experience a higher RAIM availability, even in the absence of SBAS messages, and also have FDE capability.

The Black Hole Illusion is a phenomenon that occurs when an aircraft is approaching a runway over dark or featureless terrain, particularly at night. This illusion can affect the pilot’s perception of altitude, which may lead to dangerous situations, such as an undershoot or an accidental crash.

What happens during the Black Hole Illusion:

1. Lack of Visual References: In normal daylight conditions, pilots rely on visual cues from the surrounding environment (such as lights, buildings, terrain, or other visual markers) to gauge their altitude and distance from the runway. However, when approaching over dark or featureless terrain, these visual cues are either absent or minimal. This is often the case when the runway is located over a dark area, such as a forest, ocean, or an unlit urban landscape, which creates a "black hole" effect.
2. Effect on the Pilot's Perception: As the aircraft descends, the absence of visual references gives the pilot the impression that they are higher than they actually are. This occurs because the human eye tends to misjudge altitude when there is little or no contrast between the aircraft and the surrounding environment. The pilot might believe they are closer to the ground than they actually are, leading to an attempt to lower the aircraft too much.
3. Risk of Undershoot: The primary danger associated with the Black Hole Illusion is the tendency for the pilot to descend too quickly, resulting in an undershoot of the runway. Since there are few or no ground lights or features to provide a sense of depth, the pilot might not realize they are still too high and will continue descending too aggressively, potentially leading to a crash or a missed approach.
4. The Role of the PAPI or VASI: Pilots rely on systems like the Precision Approach Path Indicator (PAPI) or the Visual Approach Slope Indicator (VASI) to maintain a proper approach angle. If the aircraft is on a correct approach path, these systems provide visual guidance to help prevent the black hole illusion. However, if the aircraft is too high or too low, these systems will indicate the need for a correction. In the absence of a PAPI or VASI, the risk of the Black Hole Illusion increases.
5. Mitigating the Black Hole Illusion:
   • Use of Instrumentation: Pilots are trained to rely on instruments, such as the altimeter and glideslope, especially during night landings or in situations where visual cues are limited.
   • Approach Planning: It’s important for pilots to plan the approach carefully and be aware of the lack of visual cues when approaching over dark terrain. In such cases, it is crucial to follow the prescribed approach path and use all available instruments to confirm altitude and descent rate.
   • Landing with Visual References: Ideally, pilots should land when they have sufficient visual references available. If this is not possible, a missed approach should be initiated rather than continuing a potentially unsafe landing.

Key Points of the Black Hole Illusion:

• Occurs when flying over dark or featureless terrain, particularly at night.
• The absence of visual references can cause pilots to misjudge altitude.
• It often leads to an undershoot because the pilot perceives they are higher than they are.
• It is a serious risk, especially when the runway is not well-lit or when the terrain around it is unlit.
• Pilots can mitigate the risk by relying on instruments and not relying on visual cues alone.

In conclusion, the Black Hole Illusion is a dangerous optical illusion that occurs during night landings, particularly when approaching over dark terrain. Proper training, use of instruments, and a disciplined approach to flying can help prevent accidents resulting from this illusion.