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TAWS with a CDFA goes a long way in helping us avoid CFIT on arrival. And a Class A TAWS will help to ensure proper landing configuration as well.
Climb, Climb Now!
We should all be practicing a handful of the alert and warning modes from our TAWS each time we go to the sim for recurrent training. At the airlines and my new Part 135 gig, wind shear and terrain alerts are two of the many “first- look” maneuvers included in a list of mandatory events that we perform every time at the sim. First-look means we are not forewarned about when, where or how often the alerts will occur – just like in real life. The requirement is both a test and a strengthening of the mental memory muscles to ensure instinctive compliance with the warnings. While I’ve never experienced an actual terrain warning, I once experienced a TCAS RA (resolution advisory – a traffic warning in which you must react) at the airlines.
We were in IMC and the TCAS display was being shared with the weather radar display. The display scale was at 40 nm due to convective activity making the TCAS target aircraft appear at the very bottom where the radar display comes to a point. At DFW, all departures have a top altitude of 10k and all arrivals have a bottom altitude of 11k – a 1,000-foot difference. If the departing and arriving aircraft have a climb rate and descent rate of over 1,300 fpm or so and are converging, the TCAS of one or both aircraft will compute an incursion into the safety bubble. This was
A classic example of cumulogranite.
the case during our arrival, and the TCAS instructed an immediate climb of over 2,000 fpm instead of our existing 1,200 fpm descent. Autopilot off, autothrottles off, initiate rapid but smooth compliance. Shortly after beginning the maneuver, a break in the clouds allowed us to spot the other aircraft. And as you would hope, it wasn’t even close.
Immediately and Instinctively
Even if the TAWS operates as it should, action initiated by the crew is what makes the airplane avoid the rocks, not the avionics. We are the ones flying the plane after all. The ones who are supposed to know exactly where we are always, and the first ones to the scene of the impact if we fail to do so. In the past, I’ve discussed the phenomenon of time compression during an intense event: How our memory works and, more relevant to this article, how we
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February 2023 / TWIN & TURBINE • 25