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Landing Flare

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Landing flare, is the maneuver performed by a fixed-wing aircraft as it transitions from the final approach phase to touchdown, involving deceleration and transition to horizontal flight. During this phase, the pilot raises the aircraft’s nose angle using control inputs, between the flare point (flare initiation altitude) and touchdown.

The flare aims to safely reduce the aircraft’s vertical velocity to near zero, ensuring a smooth landing. This maneuver is the most challenging part of normal flight and presents difficulties for pilots at all experience levels. Especially under adverse wind and turbulence conditions, landing flare can be difficult and hazardous even for expert pilots. Indeed, a significant portion of general aviation accidents stem from errors during the approach and flare phases. Failure to initiate the flare at the correct time or improper execution has been identified as a contributing factor in numerous landing incidents. Therefore, the flare is regarded as one of the most critical and technically demanding stages of pilotage.

Physical and Mathematical Modeling

The flare maneuver is a complex and transient motion in flight mechanics; multiple effects occur simultaneously during the transition from approach to level flight. Accelerations in the aircraft’s speed and flight path occur, governed by Newton’s laws. To understand flare dynamics, various physical parameters can be modeled: approach speed and glide angle, touchdown velocity, aerodynamic drag and thrust conditions, control sensitivity, pilot technique, and ground effect are among them.

The most important characteristic of the flare maneuver is the aircraft’s deceleration. During the transition from approach to landing, the aircraft generates a positive flight load (g-force) to reduce its vertical velocity. If the vertical deceleration (negative vertical acceleration) during the flare is insufficient, the aircraft does not descend sufficiently and continues to float over the runway. Conversely, if the aircraft is decelerated too rapidly (excessively high g load), the vertical velocity is abruptly halted, causing the aircraft to rapidly lose altitude and strike the runway hard (sink). Therefore, in quantitative flare analysis, the average flare load factor is of great importance.

The average n load factor experienced by the aircraft during the flare provides a measure of its tendency to float or sink; a low average n (close to 1) indicates a long and gradual flare, while a high n indicates a short and abrupt flare. Indeed, research has shown that pilot evaluations correlate consistently with the average g load affecting the rate of deceleration during the flare. In this context, the average load factor can serve as a practical indicator to predict whether a flare will be successful under different aircraft types and conditions.

In the context of mathematical modeling, the goal during the landing flare is to reduce the aircraft’s vertical kinetic energy from its approach value to zero. During this process, the aircraft increases its lift by raising its nose, thereby gradually reducing vertical velocity. This physical process can be mathematically modeled using principles of energy conservation and acceleration.

Load Factor (n) and Acceleration Relationship

During the flare, the pilot’s back-pressure input temporarily increases lift, thereby increasing the aircraft’s load factor. The upward net acceleration during the flare is expressed as:

az=(n−1)∗g

In this expression, n represents the load factor on the aircraft and g represents gravitational acceleration (9.81 m/s²).

Kinetic Energy Approach

Assuming the aircraft’s vertical velocity at the start of the flare is V_vertical, the energy required to reduce this velocity to zero is provided by the upward acceleration generated by the load factor.

Energy dissipated:

Ek=21mVd2_vertical

This energy is dissipated through upward acceleration and altitude loss:

Ep=mgh

From energy equivalence:

21mVd2=m(n−1)gh

From this, h (altitude lost during the flare) can be derived.

These formulas predict how much altitude the aircraft will lose during the flare while decelerating. In light aircraft (e.g., Cessna 172), the vertical velocity during approach is typically around 2.5–3 m/s, and a typical load factor during flare is assumed to be 1.2. In this case:

h≈2∗(1.2−1)∗9.8132=2∗0.2∗9.819≈3.9249≈2.3m

This result supports the notion that light aircraft should initiate the flare at approximately 2–3 meters altitude. In heavier aircraft, higher wing loading results in delayed lift generation, leading to higher V_vertical and larger h.

When analyzing the flare, ground effect must also be considered. As the aircraft approaches the ground, the airflow compressed beneath the wings increases effective lift and reduces drag, causing the aircraft to experience a slight “cushioning” effect. This phenomenon can reduce the aircraft’s sinking tendency and allow it to remain airborne longer during the flare.

For example, combinations of reduced nose-down moment and increased lift due to ground effect have been found to reduce the pilot’s need for rear control input (easing flare control), but may also introduce a slight ballooning tendency (sudden altitude gain), reducing predictability of the landing.

Therefore, mathematical models for optimal flare design consider aerodynamic factors such as ground effect alongside the average load factor. In fact, some developed rules allow prediction of the difficulty level of the flare maneuver for a specific aircraft and condition.

Purpose and Mechanism of the Landing Flare

The primary purpose of the flare maneuver is to safely reduce the aircraft’s vertical velocity during the transition from approach configuration to landing configuration, ensuring contact with the runway at minimum speed and an appropriate nose attitude for stable touchdown. In other words, the pilot uses the flare to prepare the aircraft for a soft landing while avoiding excessive float (prolonged flight above the runway) or a hard sink.

At the start of the flare, the pilot typically reduces engine power to idle (or to the minimum required setting) and simultaneously applies controlled back pressure on the control column to raise the aircraft’s nose angle. This controlled pull increases the wing’s angle of attack, generating lift slightly greater than the aircraft’s weight, allowing the aircraft to descend gradually without sudden drops.

During the flare, the pilot focuses their gaze on the runway threshold or horizon to precisely perceive the aircraft’s vertical motion. At the end of the flare, when the aircraft is very close to the ground, the nose is held at the desired upward angle (so that the main landing gear touches down first) and the speed is maintained slightly above stall speed. As soon as the main wheels contact the runway, the pilot slightly lowers the nose angle to prevent re-lift and initiates braking. Thus, the flare completes the transition between approach and roll-out (deceleration after ground contact).

When properly executed, the flare optimizes landing distance and provides a comfortable touchdown. If the flare is initiated too early or too cautiously, the aircraft will descend too slowly and continue to float over a long distance on the runway. This is undesirable, as an extended flare makes it difficult for the pilot to touch down at the intended point and exposes the aircraft to wind shifts and turbulence for a longer duration.

Even experienced pilots struggle to achieve precise touchdown in an excessive “floater” landing; an inexperienced pilot may overcorrect in such a situation, causing the aircraft to rise again (ballooning) and ultimately descend uncontrollably. Conversely, initiating the flare too late or inadequately is extremely hazardous. In this case, the aircraft fails to decelerate sufficiently until very close to the ground, resulting in a late and rapid flare. The vertical velocity is abruptly arrested, drastically shortening the maneuver duration, leaving the pilot with almost no time to observe and correct the situation, and leading to a hard landing at high descent speed.

Therefore, the purpose of the flare maneuver is to decelerate the aircraft to the exact required rate at the ideal moment, without prolonged float or abrupt pull-up, ensuring a safe and smooth touchdown. Pilots strive throughout their training to master this balance and develop an intuitive sense of the appropriate flare initiation altitude and control input magnitude under varying conditions (aircraft type, weight, wind, runway length).

Application Methods

The landing flare can be applied in different ways depending on conditions and pilot preference. Generally, the “how” of the flare is shaped by the approach profile. When a slow and shallow approach is used, the aircraft already has low vertical velocity, so a longer and more gradual flare may suffice. Conversely, when a steep and fast approach is used, a shorter and sharper flare is required to reduce vertical velocity before touchdown.

Indeed, technical analyses have shown that approaches with insufficient deceleration (i.e., a very flat descent) require a long, soft flare; whereas over-decelerated (steep and fast descent) approaches necessitate a rapid and firm flare at the last moment. In other words, approach parameters directly influence the flare’s form: for example, an aircraft arriving at high speed or with a shallow glide angle may not generate sufficient g-force during the flare and may float the entire length of the runway. Conversely, an aircraft approaching at a steep angle with low power may lose altitude rapidly, leaving almost no time for the pilot to react to the flare. These two extreme scenarios are undesirable in practice but commonly experienced during training. Under ideal conditions, the flare should follow a moderate profile—neither excessively prolonged nor abruptly initiated.

Pilot control usage also varies in flare application. The general rule is to simultaneously reduce power during the final approach phase and apply smooth rearward pressure to raise the nose. However, when runway length is limited or with certain aircraft types, the pilot may use a small amount of engine power during the flare to achieve a more controlled descent; this method is particularly preferred in large jets or training aircraft to use engine response against wind for a smoother flare.

Another variation in application is the initiation altitude of the flare. In some cases, pilots initiate the flare earlier (at higher altitude) for a gradual transition; in others, they delay it and execute a rapid transition. This choice depends on factors such as runway length, aircraft center of gravity, and pilot comfort level. For instance, experienced pilots, if the runway is very long and they wish to enhance landing comfort, may initiate the flare slightly early and float the aircraft parallel to the ground for an extended flare.

Conversely, on a short runway where immediate touchdown is necessary, pilots may prefer to delay the flare as much as possible to quickly settle the aircraft. These variations can be risky if not carefully managed. Extended float can make landing distance critical, while a delayed flare may result in a hard landing or bounce. Therefore, standard operating procedures typically define a specific flare initiation altitude and method for each aircraft type and weight. However, in actual operational conditions, pilots often adjust the flare according to immediate circumstances; for example, wind shear, thermals, or runway slope can influence flare execution and compel the pilot to make spontaneous adjustments.

Flare Techniques

The flare maneuver can be executed using different techniques, shaped by aircraft type, pilot preference, and conditions. The main techniques are:

One-Step Flare

In this most basic technique, the pilot increases the nose angle with a single continuous rearward pull upon initiating the flare. A smooth, constant-rate maneuver is applied. Commonly preferred in light general aviation aircraft.

Two-Step Flare (Level-off & Round-out)

This technique divides the flare into two sub-maneuvers:

Level-off: The approach glide path is terminated, and the aircraft is brought to level flight parallel to the ground.
Round-out: The angle of attack is further increased to achieve a soft touchdown. This technique can extend float duration but reduces ballooning risk.

Tau Flare (Time-to-Contact Based)

The pilot initiates the flare when the time-to-contact (tau) reaches a critical value. It relies on optical flow and angular expansion rate. Triggered by the mental sensation of “the aircraft will contact the ground in 5 seconds.”

Jacobson Flare

Based on geometric alignment. The flare is initiated when a specific reference point on the windshield aligns with a predetermined point on the runway. Provides a standardized system, especially beneficial for student pilots.

Sinking-Sensation Flare

The pilot initiates the flare when the sensation of vertical descent disappears (as if the aircraft is “floating” in the air). Often combined with delayed power reduction in jets. Each technique has advantages and limitations; the preferred method varies depending on aircraft type, altitude, runway length, and wind conditions.

Human Factors and Error Sources

The landing flare is a phase directly related to human performance and perception. The pilot’s visual perception, reasoning, experience level, and psychological state affect flare success. For novice pilots, the flare is a difficult skill to master, and numerous errors are common at the beginning. Statistics show that landings can be challenging for all pilot categories, and even the most experienced pilots can struggle during flare under adverse environmental conditions.

Landings are among the most difficult phases to learn for beginners; poor wind or visibility conditions can make them difficult and hazardous even for experts, and most accidents occur during this phase. This is related to the limits of human visual perception and timing ability.

Timing Errors

Initiating the flare at the wrong time is the most common error. Early flare—raising the nose too high—causes premature loss of speed and prolonged float. In this case, the aircraft continues to glide beyond the intended touchdown point, or the pilot may be forced to push the aircraft down, resulting in a hard landing. Additionally, if the pilot pulls back too aggressively during an early flare, the aircraft may momentarily gain altitude (ballooning) and then lose speed, leading to a sudden hard impact.

Late flare occurs when the pilot initiates the maneuver just before the aircraft is about to touch the ground; with very little time remaining, vertical velocity is not sufficiently reduced, and the aircraft may strike the runway. Late flare demands a rapid reflexive action from the pilot and offers almost no tolerance for timing delays, increasing the margin for error. Both excessively early and late flares can lead to hard, uncontrolled landings in different ways. Therefore, the most critical issue for pilots is initiating the flare at the correct moment.

Visual Illusions

Pilots’ perception of depth and distance during the flare depends on the visual environment. Weak or misleading visual cues create conditions for human error. For example, a runway wider or narrower than usual can cause pilots to misjudge altitude. A wide runway may appear lower than it is, prompting an early flare; a narrow runway may make the aircraft seem higher than it is, delaying the flare. Similarly, flights over surfaces lacking visual references (buildings, trees, textures, etc.) are hazardous. Especially during night flights or over featureless surfaces like water, pilots struggle to estimate proximity to the ground.

This phenomenon is known in literature as the black hole approach. In such a scenario, if the pilot uses only runway lights as reference, the actual aimpoint may be misperceived. As a result, the pilot may overestimate or underestimate the time-to-contact (TTC); if they use a reference above the horizon, they may perceive the remaining time as longer and initiate a late flare; if they use a reference below the horizon, they may perceive the remaining time as shorter and initiate an early flare. Such perceptual errors create serious crash risks, making night VFR approaches particularly sensitive from a pilotage perspective.

Reduced Visual Cues

Environmental factors such as fog, darkness, and rain that impair visibility increase flare errors. Experiments have shown that both experienced and inexperienced pilots exhibit systematic deviations in flare timing when visual depth cues are reduced. With limited visual information, pilots may unconsciously rely on more error-prone strategies such as distance or runway angle estimation. Therefore, to reduce human-factor errors, visual awareness must be enhanced, and pilots must be trained to correctly interpret visual cues under varying conditions.

Stress and experience level also influence flare performance. Novice pilots often misjudge ground altitude, frequently initiating the flare too high (causing float) or failing to recognize proximity to the ground until too late (resulting in abrupt pull-up). These errors decrease with experience, but even experienced pilots can make similar mistakes when transitioning to unfamiliar aircraft types.

Visual and Physical Cues

Pilots rely heavily on visual cues to determine flare timing. Literature categorizes the primary visual strategies for flare into three main groups.

Critical Distance (Altitude) Cues

The pilot aims to initiate the flare when the aircraft reaches a specific critical altitude. This absolute altitude depends on the aircraft’s wing loading and performance. For example, a light training aircraft may initiate the flare at approximately 20 ft (6 m), while a large passenger aircraft may do so at approximately 80 ft (24 m). This difference arises because large aircraft, due to higher weight/wing loading, require more time to decelerate. In distance-based strategies, the pilot uses radar altimeter or external references to perceive altitude and initiate the flare at the appropriate height.

The human eye uses two types of visual information to form distance perception: binocular cues (stereoscopic depth perception, eye convergence, etc.) and monocular cues (perspective, relative size, clarity, light-shadow patterns). For example, during approach, cues such as the size of ground objects, texture resolution, and the apparent height of the runway within the field of view help the pilot intuitively estimate distance. However, if these cues are insufficient or artificial, they can mislead the pilot.

Especially in simple simulators with two-dimensional visual displays or during night flights, real depth perception is weakened. If a pilot uses a strategy based solely on perceived distance, systematic errors may occur in low-visual environments. For example, the absence of ground texture or stereoscopic depth information in a flight simulator may cause the pilot to misperceive altitude, leading to incorrect flare timing.

Critical Runway Viewing Angle (ψ angle)

In this strategy, the pilot focuses on the geometric angle of the runway in their field of view. The horizontal angle (ψ) between the runway edges and the aimpoint, as seen from the aircraft’s perspective, is used as the flare trigger when it reaches a critical value. In other words, as the runway’s perspective expands downward, a specific angular width is deemed critical. This concept uses the runway’s apparent expansion in the pilot’s view as the timing criterion. For example, a narrow runway angle indicates high altitude; as the aircraft descends, the ψ angle increases.

The pilot may use their experience to trigger the flare when this angle reaches a specific degree. However, strategies based on ψ angle can lead to errors when runway width or approach angle changes. If a pilot applies a ψ value effective on a narrow runway to a much wider runway, the runway appears wider at a lower angle, causing an early flare. Similarly, a pilot accustomed to a 3° standard glide slope who switches to a steeper 6° approach using the same ψ value may misjudge timing.

This has been experimentally observed. Pilots transitioning between different glide slopes have shown systematic bias in flare timing when relying on their previous runway angle cues. Therefore, runway viewing angle-based methods require caution when considering runway width differences and varying approach profiles. Pilots must psychologically “recalibrate” for each new runway; otherwise, using an incorrect ψ threshold may lead to early or late flare risks.

Critical Time-to-Contact (TTC) – Tau Cues

This modern approach assumes the pilot can intuitively estimate the time remaining until ground contact. Time-to-contact (TTC) is defined as “the time remaining until the aircraft’s wheels contact the ground if no action is taken.” The pilot aims to initiate the flare when this perceived time reaches a critical value (e.g., 5 seconds). Theoretically, TTC can be calculated from distance and speed information:

TTC≈TahminiDikeyHızTahminiYerYu¨kseklig˘i(mesafe)

However, it is known that the human eye is prone to errors in accurately perceiving absolute distance and speed. Therefore, in perceptual psychology, a theory has been developed that TTC is calculated not directly from objective size estimation but via a visual ratio. According to this theory, the pilot’s eyes use specific optical flow information to sense the time-to-contact.

Tau theory links TTC to the rate of change in visual angle. Let θ

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AuthorBeyza Nur TürküDecember 5, 2025 at 9:33 AM

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Physical and Mathematical Modeling
- Load Factor (n) and Acceleration Relationship
- Kinetic Energy Approach
Purpose and Mechanism of the Landing Flare
Application Methods
Flare Techniques
- One-Step Flare
- Two-Step Flare (Level-off & Round-out)
- Tau Flare (Time-to-Contact Based)
- Jacobson Flare
- Sinking-Sensation Flare
Human Factors and Error Sources
- Timing Errors
- Visual Illusions
- Reduced Visual Cues
- Visual and Physical Cues
  - Critical Distance (Altitude) Cues
  - Critical Runway Viewing Angle (ψ angle)
  - Critical Time-to-Contact (TTC) – Tau Cues