CAT 3 Low Visibility Landing

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During bad weather, resulting in low visibility, a precision approach and landing are required in order to land safely. A precision approach is an instrument approach and landing using precision lateral and vertical guidance with minima as determined by the category of operation. A good overview can be found here.

In the flight test you see on the below video, I am using Xplane 11 as the FS platform interfaced with my A320Sim software and using Instructor Operations System (IOS) we have configured the weather and visibility to CAT 3 category of operation.

All in all the landing just takes 7 minutes, but even with full automation by the FMGC, a lot of things need to be checked and actions need to be taken. Without any external visibility and reference, fully trusting on your instruments is of key importance.

The main thing to achieve is to bring the aircraft speed in a controlled way to the Approach Speed (VAPP) while maintaining a steady glide path (3 degrees in this case) and keeping alligment with the runway. In a precision approach the Autopilot performs all of this almost fully automatic.

CAT 3 Low Visibility Landing



Memorize the above schematic and let me walk you through the different steps you see in the video (suggest you open the video in HD in a separate browser window):

  • [00:00] I am flying the EBBR25L downwind leg on Autopilot at a heading of 70 degrees and a baro altitude of 3000 Ft.
  • [00:08] The selected heading is changed to 250 degrees, and the Autopilot starts banking the plane into a right turn, while maintaining the selected altitude of 3000 Ft.
  • [01:17] The Autopilot starts rolling out of the turn and leveling the wings, flying the selected heading of 250 degrees, lined up with the EBBR25L runway.
  • [01:34] The Approach phase is activated by pushing the APPR button on the FCU, which armes the lateral LOC mode and vertical G/S mode. Being lined up very well with the localizer beam, the LOC mode almost instantainiously goes from armed (LOC*) to active (LOC).
  • [01:35] With the approach activated and in managed speed mode, the FMGC commands the aircraft to slow down. The AutoThrottle (A/THR) throttles back the engines and the speed tape on the PFD starts showing a reducing speed trend.
  • [02:10] The aircraft has slowed down to Green Dot speed (just below 220 Kt in this case). As long as the pilot keeps the Flaps/Slats in CONF 0 the FMGC will maintain Green Dot speed.
  • [02:14] Flap Lever is moved from 0 to 1, and the A/THR starts slowing down the aircraft to S Speed (about 190 Kt in our case).
  • [02:45] To have some more viewing space, I remove the FCU Window (having all the A320Sim modules on one single screen it gets a little too crowded 🙂 ). And I pull up the Head Up Display (HUD). In low visibility operations, the HUD really helps to point the pilot to where he needs to look for the runway (lights). The vertical line with the small rectangle at the top is the HUD “Synthetic Runway”. The rectangular shape is the projected view of where the pilot will see the runway. It is a realtime projection and its size and shape will change (grow) as the runway comes closer. It basically draws the contour of the runway. During the rest of the video, keep an eye on it 🙂 .
  • [02:58] The ILS Glideslope is intercepted. The FMGC vertical mode goes from G/S* to G/S, and the autopilot starts pitching down to have the aircraft following the Glideslope.
  • [03:19] Flap lever is set to 2 and the A/THR starts slowing down the aircraft to F Speed.
  • [03:27] Landing Gear is lowered. Resulting in 3 green triangles confirming the landing gear is down locked.
  • [04:19] Flap lever is set to 3 and the FMGC further lowers the target speed. The A/THR makes the aircraft further reduce speed.
  • [04:49] The very important “One Thousand” call out. At this altitude the aircraft needs to be fully stabilized and configured in its landing configuration. I still have one thing to do: the Flaps to be set to CONF FULL. All the other items on the Landing Memo are done (well, the signs I can not set yet as I still need to develop that feature in my software. So for now, just ignore 😉 )
  • [05:10] We have reached the Approach Speed (VAPP). For our weigth (66.4 Ton) and in CONF FULL, VAPP is approx 142 Kt.
  • [05:28] EGPWS gives a “Pull Up” aural message. Well, that is wrong and I clearly need to futher tune the EGPWS triggers.
  • [05:38] At 400 Ft Radio Altitude (RA) the FMGC goes into LAND mode. Start scanning the outside view intensively to look for the runway lights ! Remember, the place to watch is the HUD Synthetic Runway.
  • [06:03] At 50 Ft RA you see the first glimps of the runway, and at 30 FT RA you see the Runway Threshold Crossing lines clearly.
  • [06:04] The FMGC goes into FLARE mode.
  • [06:05] The “RETARD” call out reminds the pilot to pull-back the throttles to IDLE.
  • [06:09] With the throttles in IDLE the Ground Spoilers that were armed, automatically deploy to slow down the aircraft in its roll out on the runway.
  • [06:11] To further help reducing speed, Engine Reverse Thrust is used by deploying the Thrust Reversers (see ECAM)
  • [06:14] Finally the third element to reduce the aircrafts speed activates: The Auto Brake. You see the Auto Brake was set to LOW and the green DECEL indication lets the pilots know that the Auto Braking is Decelerating the aircraft.
  • [06:15] Notice the HUD which reduces the amount of information it shows to only the strict necessary. In case of roll out, this is the Speed and the Auto Brake setting and performance. All the other data is removed. This is called Decluttering.
  • [06:35] At 70 Kt the Engine Reverse Thrust is deactivated, and the aircraft slows down to standstill on regular wheel braking.
  • [06:45] I pushed the Sidestick Autopilot disconnect button, which is indicated by the aural sound and on the ECAM the message “AP OFF”.
  • [06:58] “Welcome to Brussels where the temparature is 15 degrees celcius, with very low visibility and heavy fogg …” 🙂 .

My A320Sim software obviously still requires further work and also has bugs that need fixing. For those of you who are professional pilots you will have noticed the following items to be improved and/or corrected:

  • With No Decision Height, the aircraft should be set to CAT3 Dual. Meaning that both Autopilots should be activated. Well, I still have a bug in the dual autopilot working 🙁 .
  • Signs on! Sorry, not implemented yet…
  • Cabin V/S and cabin altitude are clearly wrong, also a bug that needs correcting…
  • And, as noted earlier, the EGPWS is a bit too trigger happy…

Anyone that can find any additional items for improvement or bugs, leave a comment below this blog. I would be happy to learn from you.

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