Windshear

Disclaimer: 

▪︎This content is Not an official document and does not represent the views of Airbus or any other aviation authority.

▪︎The information provided may be incorrect or misinterpreted and should not be relied upon for decision-making. 

▪︎Always refer to official documents and consult with a qualified aviation professional before making any decisions based on the information provided in this blog post.

▪︎The information provided in this blog post is based on personal study and review.

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According to the Airbus FCTM, there are operational recommendations regarding windshear. 

 

Before we delve into this procedure, 

it's essential to understand that there is a difference between predictive windshear warnings and reactive windshear warnings. 

Even though both are referred to as "warnings, " there is a distinct difference between the two.

 

1. Predictive windshear

Predictive windshear warnings are generated by the weather radar, 

while reactive windshear warnings come from the FAC (Flight Augmentation Computer)

Predictive Windshear by weather radar.

In the windshear system, there are not only warnings but also cautions and advisories.

 

 

2. Reactive Windshear warning

 

The windshear detection function is provided by the Flight Augmentation Computer (FAC) in takeoff and approach phase. (Flight Augmentation Part) 

 

There are differences in aural warnings between reactive windshear and predictive windshear. 

 

Additionally, the warnings displayed on the Primary Flight Display (PFD) differ. 

In reactive windshear warnings, you hear the aural message "WINDSHEAR" itself. 

 

Meanwhile, the predictive windshear indication on the PFD is displayed as "W/S AHEAD" and appears in different colors, either red or amber, depending on whether it is a predictive warning or caution.

 

 

windshear alerts on PFD

 

 

 

FCTM operation recommendations (Windshear)

 

Now, let's explore the FCTM's operational recommendations for windshear. Based on my experience, these instructions have evolved over the years, so it's crucial to refer to the most current guidance.

 

In the case of reactive windshear(WINDSEHAR, WINSHEAR, WINDSHEAR), 

it's essential to follow the memory items. Before reaching V1, initiate a reject takeoff, and after V1, engage TOGA. Vr, follow the guidance provided by the SRS orders.

Windshear memory item

 

Takeoff

 

Reactive windshear warnings will not sound during the takeoff roll since they are not activated until 3 seconds after takeoff or until reaching 1300 feet AGL during the approach (note that altitude thresholds may vary).

Now, what about predictive windshear warnings, such as "windshear ahead"? These predictive windshear alerts, including warnings and cautions, are inhibited when the aircraft's speed is above 100 knots and up to 50 feet. So, if such an alert occurs, it will be when the speed is below 100 knots. In this case, the FCTM specifies that the captain must reject takeoff, which makes sense because if the speed is below 100 knots, rejecting takeoff is generally a safer option.

 

FCTM - windshear operational recommendations.

 

 

Approach 

 

During the approach, if a reactive windshear warning is issued, the correct procedure is to follow memory items, which involve setting TOGA thrust and maintaining the SRS mode. If the autopilot is engaged, it should also be kept on

 

However, when faced with a "MONITOR RADAR DISPLAY" windshear caution, there may be different options to consider as below. 

 

In the case of "GO AROUND, WINDSHEAR AHEAD" aural alert triggering, the PF must set TOGA for a go-around.

 

 

we should notice the difference between predictive windshear and reactive windshear warnings, even though they use the same word 'warning'.