quarta-feira, 28 de abril de 2021

WHEN WILL WE START THE FLARE - Three Case Studies


ENGLISH

PORTUGUÊS

The above gif was taken when for a minute of simulation from the 900 seconds to the 960 seconds. It shows tracks identified as safe in cyan and tracks identified as anomalous in yellow. This identification is done at every simulation step as can be seen for track 3661.

 

O gif acima foi tomado quando para um minuto de simulação a partir de 900 segundos até os 960 segundos. El mostra trajetórias identificadas como seguras em ciano e trilhas identificadas como anômalas em amarelo. Esta identificação é feita em cada etapa de simulação, como pode ser visto para a faixa 3661.


WHEN WILL WE START THE FLARE

·         Source: Airbus Safety

Contributors:

-    Raimund GEUTER Expert Pilot Flight Operations Support

-    Sundeep GUPTA Accident/Incident Investigator Product Safety

-    Thomas LEPAGNOT Accident/Incident Investigator Product Safety

-    Marc LE-LOUER A300/A310 Flight Operations Support Engineer Customer Support

-    Xavier LESCEU,  Andris LITAVNIKS and Christian PAQUIN-LAVIGNE

-    Airbus Canada.

Source: National Aviation University, Kyiv, Ukraine.

PROCEEDINGS, THE SIXTH WORLD CONGRESS, "AVIATION IN THE XXI CENTURY", “Safety in Aviation and Space Technologies”.

E. O. Kovalevskiy, candidate of engineering

V.V. Konin, Doctor of Engineering

T.I. Olevinska, post-graduate student

Source: James Albright, retired U.S. Air Force pilot with time in the T-37B, T-38A, KC-135A, EC-135J (Boeing 707), E-4B (Boeing 747) and C-20A/B/C (Gulfstream III).

Source: Math Works, MATLAB for Artificial Intelligence.

Source: Vernier, Airliner Takeoffs and Landing with Graphical Analysis


 Two methods of aircraft flare are considered:

a) fixation of touchdown point and altitude exponential step     change.

b)     step change of trajectory slope.

In both cases gradual descending of height and vertical speed was achieved.

 Landing is divided into linear decrease on the glide slope and maneuver of flare, in which aircraft is moving by the exponential trajectory.

 For a trajectory coming to land at Boston Logan International airport (KBOS) on runway 22L to be safe, the trajectory must satisfy the following rules:

  •   The trajectory must be closely aligned with the runway          direction.
  •   The glide slope must be between 2.5 and 4 degrees in the last 20963 meters. At distances above 20963 meters, the altitude must be at least 3000 ft.
  •   The speed must be between 120 knots and 180 knots at the landing point. The upper speed bound can increase linearly with distance from the landing point.

 Below a graph illustration for Boeing 737’s takeoff and landing.



FIRST CASE STUDY: Airbus

BOUNCED LANDING

NOSE LANDING GEAR IMPACT AND

A TAIL STRIKE ON GO-AROUND

 An A320 was on the final approach segment of its ILS approach, configured for landing (CONF FULL).

The Pilot Flying (PF) disconnected the autopilot at 370 ft Radio Altitude (RA) and kept autothrust ON. At 200 ft, tailwind variations caused the airspeed to drop below approach speed (Vapp).


Operational Considerations

 Role of the Pilot Monitoring (PM)

The FCOM SOP for landing requests a SPEED callout by the PM in the case of speed deviation of 5 kt below the target speed. The PF should initiate a go-around unless they consider that a stabilized condition can be recovered by small corrections to the aircraft and within sufficient time prior to landing.

The FCTM states that the risk of tail strike is increased due to the high angle of attack and high pitch attitude if the speed of the aircraft is allowed to decrease too far below Vapp before the flare.

Looking at step in the event described above, it shows the speed went below Vapp -5 kt from 100 ft and below. If the PM had made a “SPEED” callout then the PF may have noticed the speed decay and attempted to correct it or initiate a go-around if it was not likely to stabilize in time.


Flare Height

The FCOM states that in a stabilized approach, the flare should be initiated at 30 ft for A320 family aircraft (the values for other Airbus aircraft are provided later in this article).

The FCTM recommends initiating the flare earlier if there is a tailwind. This is because a tailwind will contribute to a higher ground speed with an associated increase in vertical speed to maintain the approach slope.

Initiating the flare earlier would have reduced the high vertical speed of the aircraft in the event described above.

Thrust Lever Management

The A320 FCTM explains that the flight crew can rapidly retard all thrust levers to IDLE either earlier or later than the 20 ft “RETARD” auto callout reminder depending on the conditions. However, the thrust levers should be at IDLE by touchdown to ensure that the ground spoilers will extend and keep the aircraft on the ground.

In step of the event, the PF pushed the thrust levers above the CLB detent during flare. This increased thrust and inhibited the ground spoiler extension during the initial touchdown, which contributed to the aircraft bounce.

Bounce Management

For a high bounce, as was the case in the incident described above, the FCTM recommends maintaining the aircraft’s pitch attitude and performing a go-around.

The hard impact of the nose landing gear with the runway described in step of the event was caused by extension of the ground spoilers when the thrust levers were retarded to IDLE during the bounce combined with a full forward stick input after the bounce.

 Go-Around Close to the Ground

The FCTM recommends avoiding an excessive rotation rate during a go-around close to the ground and to counteract any pitch-up effect due to the thrust increase.

In step of the event, it was the full back stick input combined with the nose landing gear bounce and thrust increase that contributed to the tail strike.


RECIPE FOR A SAFE LANDING

The recommendations below summarize the procedures and techniques provided in the FCOM and FCTM.

Be stabilized

A safe flare can only be achieved when the aircraft is stabilized, meaning that all of the flight parameters areas expected, including:

- the aircraft is on its expected final flight path (lateral and vertical)

- speed is close to Vapp, and

- wings are level.

If the aircraft reaches the flare height at the correct speed and it is on the expected flight path, then a normal flare technique will lead to a safe landing.

PM must call out any flight parameter deviation

Careful monitoring of the flight parameters including speed, pitch, bank and vertical speed, enables the PM to raise the attention of the PF to any deviation during the final approach. This will enable the PF to respond accordingly and initiate a go-around, if required.

Refer to the FCOM SOP for Approach for more information about the PM callout related to the flight parameter deviation threshold.


Flare at the right time

Flare should be initiated at around:

·         30 ft RA (A220/A300/A310/A320) or

·         40 ft RA (A330/A340/A350/A380) in stabilized conditions.

 Factors that may require an earlier initiation of the flare:

- Steeper approach slope (more than the nominal 3º)

- Increasing runway slope or rising terrain before the runway threshold

- Tailwind

- High airport elevation.




SECOND CASE STUDY: National Aviation University, Ukraine



The bottom line is fixation of flare beginning point coordinates (xf, hf) and touchdown point coordinates (xtd, htd).

(xg, hg) – glide slope beginning point, (xg0, hg0) – is a fictitious point on the ground on which glide path is projected, (x, hc) – is a final point of flare which is chosen in such way, that the exponent of flare trajectory intersects the ground at the touchdown point.

Two stages for reaching desired horizontal and vertical speed at touchdown point (xtd).

First stage

Decreasing horizontal speed W up to desired value Wz from point xg to point xf while height is on level hf = hz.

Second stage

Fixing the horizontal speed and begin to change the height by the exponential law from the value hz – hс to the value hс in such a way, that the exponent line crosses the point xtd with the vertical speed of hp.

The input data for Math modeling is:

Horizontal speed: Wz=40 m/s;

Desired vertical speed in touchdown point (point where h=0): phz=0.5 m/s;

Initial trajectory slope angle in radians: γ0 =0.097;

Flare beginning height: hz=15 m.

Flare begins at the moment: t=655 s.

The trajectory slope angle change from the flare beginning by the height change law, the vertical speed change law and the flare period equation.


FROM INPUT DATA

Height and vertical speed calculation



The first method provides more accurate touchdown.

It is the fixation of touchdown point and altitude exponential step change.

THIRD CASE STUDY: James Albright

A G450’s flight path vector at 10 ft. on a short runway (KBED Runway 23). By James Albright.


“I find that raising my eyes to the end of the runway, but below the horizon, does the trick. The photo shows the flight path vector (symbology that shows the aircraft’s trajectory) slightly below the end of the runway because I was looking at the runway’s end, not the horizon. If I sense the airplane has leveled off, I’ll nudge the stick forward with the thought, “Keep it coming down.” This assures the aircraft continues to descend. Even without flight path vector technology, the pilot needs only to shift his or her eyes to the end of the runway to keep the descent rate going. But there is a little more to it than that, and for that we need to look at some timing.”

G650’s flare path starting at 25 ft

When we begin the flare, the MLG will be at 25 ft. and the pilot’s eyes 14.5 ft. higher. The aimpoint will be 39.5 ft. / tan(3deg.) = 754 ft. away. Since the MLG have to travel an additional 42 ft., we know the distance of the flare will be a total of 796 ft. If we assume a ground speed of 120 kt., the flare will take:


The flare can be learned scientifically by instilling the need to begin at a consistent height, pulling back at a consistent rate, and with your eyes pointed at the end of the runway. Each event should be graded looking for a 4-sec. rotation to flare, ending with the wheels touching at the desired aimpoint.




How to Land an Airplane, in Summary

(1) Fly a stable approach, on speed, on the proper glidepath.

(2) Cross the runway threshold at 50 ft. visually or electronically. Remember that if flying visually or on an ILS glideslope, your wheels will be lower than 50 ft. (In our example, that was 35.5 ft. when flying visually.)

(3) Determine the proper flare height based on any flight manual data or on what you have determined by experience. This height can be made evident by electronic means, such as a radio altimeter, but should always be backed up with a point on the runway that you expect to just disappear under the nose. (In our example, a point 600 ft. short of the aimpoint.)

(4) At the proper flare height, shift your eyes to the end of the runway (not the horizon), and using one smooth and continuous motion, pull back to your flare rotation pitch. The pull should take 4 sec. and should end as the wheels touch with the aircraft still in a 100- to 200-fpm descent rate.

Notice that we have not mentioned thrust at all, which will be handled in accordance with aircraft-specific procedures. My technique is to allow the autothrottle “retard” function, if available, to function as designed. This further reduces the number of variables. If operating without autothrottles, I attempt to initiate the reduction at the same time I initiate the pitch rotation, reaching idle as the wheels touch. This has worked on every aircraft I have flown, but I recognize it will not work for others.

One last note for those flying aircraft with unpublished eye-to-wheel and flare heights. The math shown here is for a Gulfstream G650, an aircraft in the 100,000-lb. range that is nearly 100 ft. long. Using a 25-ft. flare height will probably be conservative for smaller aircraft but will give you a starting point. (Remember larger aircraft may have flare heights around 30 ft.) I recommend trying these out in the simulator or seeing what you have been doing in the airplane as a comparison. The first step in any scientific endeavor is observation. I believe you can improve your landings if you approach the landing flare as science, not art.

Factors that may require an earlier flare

Flare should be initiated at around:

30 ft RA (A220/A300/A310/A320) or

40 ft (A330/A340/A350/A380) in stabilized conditions.

“The PF must avoid forward stick inputs once flare is initiated.”

Any forward stick input after flare is initiated will increase the risk of landing on NLG with hard impact.

The PF must start the flare with a positive and prompt back pressure on the control column to break the descent rate. The PF must then maintain a constant and positive back input on the control column until touchdown.


Retard! Retard! Retard! Retard!

For A320/A330/A340/A350/A380 aircraft

The 20 ft “RETARD” auto callout is a reminder, not an order. The PF can retard the thrust levers earlier or later depending on the conditions.

The PF must ensure that the thrust levers are at idle in any case, by touchdown at the latest, to enable automatic extension of the ground spoilers.”

In the case of a bounce - Maintain the aircraft pitch



HIGH BOUNCE

·         Maintain pitch

·         Apply go-around thrust

·         Counteract any pitch-up tendency (because of THRUST INCRESE. That will avoid TAILSTRIKE).




domingo, 28 de março de 2021

Pilot Go-Around (PGA) Vs. Pilot Not Go-Around (PnGA) - Psychology

Psychology of the Decision Making Under Time Pressure



SOURCE: Wright State University

International Symposium on Aviation Psychology

Haslbeck, A., Eichinger, A., & Bengler, K. (2013). Pilot Decision Making: Modeling Choices in Go-Around

Situations. 17th International Symposium on Aviation Psychology, 548-553.

https://corescholar.libraries.wright.edu/isap_2013/23

Part of the Other Psychiatry and Psychology Commons

 

SOURCE: FLIGHT SAFETY FOUNDATION - GO-AROUND DECISION-MAKING AND EXECUTION PROJECT



One important aspect of good airmanship is pilots’ decision making (FAA, 2004; DeMaria, 2006).

Long-term experience is needed to build up comprehensive knowledge for an aviator to find appropriate decisions in a certain situation.

One potentially hazardous situation is the approach phase, representing more than one-third of all fatal accidents (IATA, 2011; Boeing, 2012).

CREW FAILED TO GO-AROUND

Two typical accident categories defined by the International Air Transport Association are runway excursions (23% of IATA listed aircraft accidents in 2010) and hard landing (5%). In-depth analysis has shown, that in 35% of the runway excursions in 2010, meteorology has been a contributing factor. To complement this information, in one-fourth of all cases, the flight crew has failed to go-around after an unstabilized approach (IATA, 2011).

Go-around can be a safe decision to master the high-risk situation of a hazardous approach.


For types 1 and 2, the time intervals between different wind checks can be calculated. If a pilot is aware of a wind potentially differing from the ATC information, he should early perform a first wind check (t1) in the final approach (below 1,000 ft above ground level) and should repeat this check continuously until a final decision to (not) go around is made. The final wind check before the go-around is also measured (t2). If only one wind check is performed first and last check time coincide (t1=t2).


What are the driving forces for pilots to consider relevant information sources, i.e. important data displays?

Rasmussen’s classification of action identifying skill-based, rule-based, and knowledge-based behavior can help to localize relevant mechanisms (Rasmussen, 1983).

According to O’Hare (2003), “it will be easier to continue with an existing course of action than to change to a new one” (p. 223). So, pilots will sometimes tend to stick to unsuitable skill- or rule-based behavior, where analytical knowledge-based strategies would be appropriate (O’Hare, 2003).

Research Hypothesis 1: Pilots with a high level of experience will come to "better" decisions based upon good airmanship.

Research Hypothesis 2: Pilotos not intending to go around (PnGA) perceive relevant information too late or not at all.

The first wind check is later for PnGA than for PGA.

Research Hypothesis 3: Pilots intending to land (PnGA) stick to a default option up to the point of deciding to choose the default of landing.

The first wind check is not differing between PnGA and PGA.


Took part in this research Pilots with different practices and training.

Twenty-six long-haul captains (CPTs) flying Airbus A330/340 types participated in the experiment in a full flight simulator (JAR-STD 1A Level D) with A340-600 configuration and twenty-seven firs officers (FOs) scheduled on the A 320 short-haul fleet participated in an equivalent A320-200 full-flight simulator.

Scenario

An uneventful flight from the east to Munich Airport in the early morning hours. The PF came back from his last rest about 25 minutes prior to the landing to perform the approach and landing. In the first phase of the approach, using the autopilot, foreign air traffic control (ATC) communication (‘party line’) between other approaching aircraft and the airport could be heard. Pilots’ tasks were to plan, monitor, and communicate. When approaching the instrument landing system, it was the PF’s decision when to change from autopilot to manual control.

To provoke a hazardous situation, at 1.000 ft. above ground level (AGL), a gentle wind turned into an illegitimate strong tailwind (16 knots) by a scripted event. The wind information given b ATC was constantly good over the whole scenario. For pilots, this information given by ATC is binding. Only the non-binding wind indicator located at the pilot’s navigation display has shown the real wind strength and direction.

Such a hazardous situation can occur when the wind turns because the wind information given by ATC is averaged over several minutes. So, the situation was inexplicit and uncertain for the participants to make the trade-off between a fuel-saving and economic landing with a noticeable higher risk or the abort of the approach for a safe second try (Haslbeck et al., 2012). The chance to go around was given to all participants until 70 ft. AGL. At this height, the PM was structured to callout ‘go-around’ and abort the approach due to a strong tailwind.

THE RESULTS

The long-haul captains with a lower level of practice and training but a high level of operational experience show significantly more willingness to land in a risky situation with strong tailwind than short-haul first officers do.

Interestingly only a small number of pilots (26 %) would have landed without the PM being instructed to trigger the go-around in any case. Instructor pilots normally report a higher tendency to go-around when being in the flight simulator in comparison to real flights.





















sábado, 20 de fevereiro de 2021

Crosswind Landing - DO NOT Change The Chosen Technique Till The FLARE

 


ENGLISH

PORTUGUÊS

APPROACH TECHNIQUES

 

TÉCNICAS DE APROXIMAÇÃO

 

A final approach in crosswind conditions may be conducted:

 

Uma aproximação final em condições de vento cruzado pode ser conduzida:

 

. With wings level (i.e., applying a drift correction to track the runway centerline); this type of approach usually is referred to as a crabbed approach; or

 

. Com asas niveladas (ou seja, aplicando uma correção de deriva para se alinhar ao eixo da pista); esse tipo de aproximação geralmente é referido como uma aproximação caranguejando; ou

 

. With a steady sideslip (i.e., with the fuselage aligned with the runway centerline, using a combination of into-wing aileron and opposite rudder [cross-controls] to correct the drift).

 

. Com um deslizamento lateral constante (ou seja, com a fuselagem alinhada com o eixo da pista, usando uma combinação de aileron do lado do vento e leme oposto [controles-cruzados] para corrigir a deriva).

 

FACTORS TO DECIDE WHICH ONE TO BE TAKEN

 

FATORES A DECIDIR QUAL A SER TOMADO

 

. Aircraft geometry (pitch-attitude limits and bank-angle limits, for preventing tail strike, engine contact or wingtip contact);

 

. Geometria da aeronave (limites de atitude de arfagem e limites de ângulo de inclinação das asas, para evitar colisão da cauda, do motor ou da ponta da asa);

 

. Aileron (roll) and rudder (yaw) authority; and,

 

. Autoridade de Aileron (rolagem lateral) e leme (guinada); e

 

. The magnitude of the crosswind component.

 

. A magnitude da componente do vento cruzado.



Effect of Wind on the Fuselage and Control Surfaces

 

Efeito do vento na fuselagem e nas superfícies de controle

 

As the aircraft touches down, the side force created by the crosswind striking the fuselage and control surfaces tends to make the aircraft skid sideways off the centerline.



 

À medida que a aeronave toca o solo, a força lateral, criada pelo vento cruzado atingindo a fuselagem e as superfícies de controle, tende a fazer a aeronave derrapar de lado para fora do eixo da pista.


FLARE TECHNIQUES

 

TÉCNICAS DE FLARE

 

When approaching the flare point with wings level and with a crab angle, as required for drift correction, one of the three techniques can be used:

 

Quando se aproximar do ponto de FLARE com asas niveladas e com um ângulo de caranguejamento, conforme necessário para correção de deriva, uma das três técnicas pode ser usada:

 

1st. Align the aircraft with the runway centerline, while preventing drift, by applying into-wind aileron and opposite rudder;

 

1ª. Alinhe a aeronave com o eixo da pista, enquanto evita a deriva, ao aplicar aileron do lado do vento e leme oposto;

 

2nd. Maintain the crab angle for drift correction until the main landing gear touch down; or,

 

2ª. Mantenha o ângulo de caranguejamento para correção de deriva até que o trem de pouso principal toque no solo; ou

 

3rd. Perform a partial decrab, using the cross-controls technique to track the runway centerline.

 

3ª. Desfaça parcialmente o ângulo de caranguejamento, utilizando a técnica de controles-cruzados para manter o eixo da pista.

 

Some AOMs and autopilot control requirements for AUTOLAND

recommend beginning the ALIGNMENT PHASE well before the FLARE point (typically between 200 feet and 150 feet), which results in a steady-sideslip approach down to the FLARE.

 

Alguns AOMs* e requisitos de controle de piloto automático para AUTOLAND recomendar iniciar a FASE DE ALINHAMENTO bem antes do ponto FLARE (tipicamente entre 200 pés e 150 pés), o que resulta em uma abordagem de lado constante até o FLARE.

AOMs* = Aircraft Operating Manuals




Engine Thrust Reverser Effect

 

Efeito do Reversor de Potência dos Motores

 

When selecting reverse thrust with some crab angle, the reverse thrust results in two force components:

 

Ao selecionar a potência reversa e com algum ângulo de caranguejamento, a potência reversa resulta em duas componentes de força:

 

1st. A stopping force aligned with the aircraft's direction of travel (runway centerline); and,

 

1ª. Uma força de parada alinhada com a direção do movimento da aeronave (eixo da pista); e

 

2nd. A side force, perpendicular to the runway centerline, which further increases the aircraft tendency to skid sideways.

 

2ª. Uma força lateral, perpendicular ao eixo da pista, o que aumenta ainda mais a tendência da aeronave em derrapar para o lado.

 

The thrust-reverser effect decreases with decreasing airspeed.

 

O efeito do reversor de potência diminui com a diminuição da velocidade do ar.

 

Rudder authority also decreases with decreasing airspeed and is reduced further by airflow disturbances created by the thrust reversers. Reduced rudder authority can cause directional-control problems.

 

A autoridade do leme também diminui com a diminuição da velocidade do ar e é reduzida ainda mais por distúrbios de fluxo de ar criados pelos reversores de potência. A autoridade reduzida do leme pode causar problemas de controle direcional.

 




Effect de Uneven Braking Forces on Main Landing Gear

Efeito de forças desiguais de frenagem no trem de pouso principal



Tire-cornering and Wheel-braking Forces

Forças de canto do pneu (movimento lateral perpendicular ao pneu) e de frenagem de rodas


Exemplos:

Um pouso com deslizamento lateral (ângulo de caranguejamento zero) requer um ângulo de inclinação lateral das asas de 3 graus no toque ao solo (ponto A). Um pouso com asas niveladas (sem caranguejamento) requer um ângulo de caranguejamento entre 4 graus e 5 graus no toque ao solo (ponto B).



Exemplos:

Um pouso com deslizamento lateral (ângulo de caranguejamento zero) requer um ângulo de inclinação lateral das asas de cerca de 9 graus no toque ao solo (ponto A).

Um pouso com asas niveladas (sem desfazer o ângulo de caranguejamento) requer um ângulo de caranguejamento de 13 graus no toque ao solo (ponto B). O ponto C representa um toque ao solo usando uma combinação de deslizamento lateral e ângulo de caranguejamento (cerca de 5 graus de ângulo de inclinação lateral das asas e cerca de 5 graus de ângulo de caranguejamento). O ponto D representa um pouso com deslizamento lateral constante conduzido com cerca de 4 nós acima de VREF.




AÇÃO DE FRENAGEM RELATADA (ÍNDICE)

Nota 1: Pista seca, úmida ou molhada (menos de três milímetros [0,1 polegada] de água) sem risco de hidroplanagem.

Nota 2: Pista coberta com neve seca.

Nota 3: Pista coberta com lama.

Nota 4: Pista coberta com água parada, com risco de hidroplanagem, ou com lama.

Nota 5: Pista com alto risco de hidroplanagem.