What is a Pilot Deviation?

A pilot deviation results from a pilot action that violates a Federal Aviation Regulation. The majority of pilot deviations (69%) occur during GA operations.

Types of Deviations

Pilot deviations are classified as either airborne deviations (77%) or surface deviations (23%).

Airborne Deviations

Airborne deviations occur when a pilot deviates from an assigned heading, altitude, or instrument procedure, or enters controlled or restricted airspace without ATC clearance.

Types of VFR deviations (listed in order of occurrences):

• Airspace violations (e.g., flying into prohibited airspace without clearance)
• Flying VFR into IMC
• Low-level flight
• Required aircraft equipment is not installed or operating

Types of IFR deviations (listed in order of occurrences):

• Altitude violations (e.g., failure to maintain the assigned altitude)
• Course clearance violations
• Airspeed violations
• Missing a compulsory reporting point

Surface Deviations

Surface deviations include:

• Taxiing, taking off, or landing without clearance
• Deviating from an assigned taxi route
• Failing to hold short of an assigned clearance limit
• Vehicle and pedestrian deviations in an airport movement area

The primary area of concern within the surface deviation classification involves runway incursions.

Runway Incursions

Reference: AC 91-73

A runway incursion is any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle, or person on the protected area of a surface designated for the landing and takeoff of aircraft.

A surface incident is similar to a runway incursion but occurs on a designated movement area (not a runway) and affects or could affect the safety of flight.

Types of Runway Incursions

• Pilot Deviations: Crossing a runway hold marking without a clearance or taking off or landing without a clearance.
• Operational Incidents: Clearing an aircraft onto a runway while another aircraft is landing on the same runway.
• Vehicle Deviations: Crossing a runway hold marking without ATC clearance.

Runway Incursion Severity

Runway Incursion Statistics

In the U.S., an average of three runway incursions occur daily. According to FAA data, approximately 65% of all runway incursions are caused by pilots, of which GA pilots cause 75%.

Causes of Runway Incursions

Investigations of runway incursions have identified four major contributing factors:

• Failure to comply with ATC instructions
• Lack of airport familiarity
• Nonconformance with standard operating procedures
• Distractions during taxi operations

Wrong Runway Departures

Wrong runway departures are a subset of runway incursions. No one intends to take off on the wrong runway, but it still happens.

Major contributing factors to wrong runway departures:

• Short taxi distance (less time to spot errors)
• Single runway airports
• A single taxiway leading to multiple runway thresholds
• The close proximity of multiple runway thresholds

Best practices for preventing wrong runway departures:

• Brief the entire taxi route to the departure runway using the airport diagram.
• If uncertain about the taxi route, request progressive taxi instructions.
• Verify each airport marking and sign along the taxi route.
• Avoid distractions while the aircraft is moving (“heads up, eyes out”).
• Set the heading bug to the runway heading and verify it matches the aircraft heading before takeoff.

Wrong Direction Departures from an Intersection

A wrong direction departure occurs when a pilot is cleared for an intersection takeoff and then departs in the wrong direction.

Major contributing factors to wrong-direction departures:

• Feeling rushed into the situation
• Misinterpreting airport markings and signs
• Not being fully prepared and ready when reaching the hold short line

Best practices for preventing wrong direction departures:

• Visualize the runway holding position sign as the runway (e.g., the runway number on the left side of the sign is to the pilot’s left).
• At a towered airport, do not confuse an instruction to turn after departure with a turn onto the runway.

Wrong Surface Landings

A wrong surface landing occurs when an aircraft lands or tries to land on the wrong runway, on a taxiway in error, or at the wrong airport.

Best practices for preventing wrong surface landings:

• Identify nearby airports with similar runway alignments that could cause confusion.
• Review the airport diagram and approach lighting in advance, noting key features and geometry.
• Back up all visual approaches with instrument guidance.
• Reference moving map displays to increase situational awareness and safety.
• Verify the correct runway alignment on every final approach.

Types of Errors that Can Lead to Deviations

Inadvertent pilot deviations can result from a variety of error types, including decision errors, skill-based errors, and perceptual errors.

Decision Errors (Cognitive)

Decision errors are “honest mistakes” that occur when one does not have the appropriate knowledge or makes a poor choice. An action is carried out as intended but is inadequate for the situation.

Examples:

• Inadequate weather evaluation
• Improper refueling decisions

Skill-Based Errors (Motor Control)

Skill-based errors are “stick-and-rudder” mistakes that occur without significant conscious thought. A person intends to carry out an action but carries it out incorrectly, and the desired goal is not achieved.

Examples:

• Airspeed or altitude not maintained
• Inadequate aircraft control

Perceptual Errors (Sensory)

Perceptual errors result from illusions. These can occur when sensory input is degraded at night or in other situations causing reduced visual acuity.

Examples:

• Misjudged distances
• Spatial disorientation/vertigo

Best Practices for Avoiding Airborne Deviations

Plan Each Flight: Always review NOTAMs, even when flying to a familiar airport. Conditions can change rapidly, like a pop-up temporary flight restriction (TFR).

Talk and Squawk: ATC can act as another set of eyes and has the latest local TFR information.

Give Yourself Some Room: Using a GPS to fly along an airspace boundary could result in a pilot deviation if ATC radar shows the aircraft within the restricted airspace. It is best to use at least a 5 NM buffer.

Stay Alert: Avoid distractions by maintaining a sterile cockpit when appropriate.

Best Practices for Avoiding Surface Deviations

The best way to avoid a runway incursion is to make sure you understand (1) where you are at, (2) what you have been cleared to do, and (3) where you are going.

Standard Operating Procedures (SOPs): GA pilots should develop and adhere to SOPs based on regulations and industry best practices. A sterile cockpit and proper use of aircraft lights should be defined in every pilot’s set procedures.

Situational Awareness (SA): Pilots can establish SA by reviewing the expected taxi route and hot spot locations. Pilots can maintain SA by avoiding heads-down time when taxiing.

Proficiency: Recurrent training and continuing education lead to proficiency. A flight to a towered airport with an experienced instructor is a good way to learn and practice.

Point and Acknowledge: Pointing at and calling out location signs and markings can help a pilot maintain focus and attention.

Pilot Notification of Suspected Deviations

When it appears that a pilot’s actions constitute a possible pilot deviation, ATC notifies the pilot as soon as operationally practicable.

"[call sign] possible pilot deviation, advise you contact Huntsville Tower at [telephone number]."

Note: This immediate notification is known by ATC as a Brasher warning. It was named after Captain Jack Brasher, who, in 1985, deviated from an assigned altitude by 700′. It was not until almost six months when Brasher received notification of a proposed certificate action. When asked about the flight, Captain Brasher replied that he had no recollection of the events.