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Wednesday, September 8, 2010

A330: Don't interfere with a Smart Woman!

Many mysteries of the female gender will go unsolved until the end of time, and the Princess’ secrets are no different. Don’t ask ‘why’ she does what she does … the best any pilot can do is to know what to expect, know when she’s lying, and what to do about it.

In a perfect world, the A330 strives to fly her profile in managed Nav. This profile plans a flight-idle descent with managed speed. She displays information on the map as to when she’ll manage her speed, per constraint, with a solid magenta dot. She displays a lightening bolt where she’ll intercept the path, a blue arrow for level off, and a white arrow for descent. She displays her constraints in magenta if she’s going to make it, amber if she’s not. If she’s going to make her constraints, speed and or level off, both will be displayed in magenta on the MCDU.

She wants to bring the thrust to idle and perform an idle descent. She’ll decelerate at the magenta D to approach speed, and all the pilot has to do it bring out the flaps and the gear. That's in a perfect world.

The Princess wants to make her profile… and she will, until someone interferes with her plan. When ATC slows you up during your descent, the minute you change your speed from the ‘profile descent speed’ (found on performance page) to a slower speed, you’ve just taken yourself off profile. Once you’ve taken yourself off profile, you no longer will make your restrictions. The worse part of this scenario is the A330 display stays the same… indicating you are going to make the constraint per the magenta indications. Fascinating.

What can you expect… you’ve interfered with her plan.

This is the problem: The Princess will indicate you’re going to make your level off with her magenta colored constraints when you're not. If you know this, you’ll be fine. The easiest way to determine how far you’re off the profile is on the Progress page. Know that if you’ve been slowed, you will be high. The only way to get her back on profile is with speed brakes.

Watch the deviation on the progress page, use the speed brakes, and you’ll can her get back on the profile. All is good. But always keep apprised of the distance remaining and your altitude for profile planning.

Enjoy the journey!

~ Karlene


  1. Thats slightly more complicated than the 430w in my Cardinal!

  2. Is it okay that I understood very little of that?! Best of luck querying!

  3. That's okay Heather, you understood the most important part... Query!

  4. Hi Pilot... a bit more complicated, but that's the French of you. :)

  5. So there's no way to just "reset" the approach?

  6. Torifly... excellent question! There's no need to reset the approach. Getting off profile isn't a bad thing...just something to be aware of to make the crossing restrictions. You can still make it, you just need to know she won't do it on her own and react promptly. Once you've interfered... now you have to help her.

  7. Counting on an idle descent is like planning to land on the theshold as opposed to the 1000' mark: you've taken away all of your margins. In gliders we plan the pattern at 1/2 speed brakes so we have some margin either way. Your environment is much more complex, and if I were designing the descent profile I would plan on some random event (distracted controller, NORDO a/c on freq, t-storm, resequence,...) and use a very low power descent rather than idle descent. In the long run real world planning saves more fuel than wishful thinking. Plus, pax comfort means avoiding speed brakes (although Delta doesn't emphasize pax comfort from my experience).

  8. Dr. ATP... Excellent thoughts. I don't fly gliders, but understand saving your margins. But, then you need to because you don't have engines when needed most.
    The airbus was designed for maximum fuel savings. The plane is smarter than the pilot and ATC. In a perfect world...and one that may come when more gets automated and we all fly established approaches to the runway...this plane actually does great.

    Ah... Not all Delta. Every crew I've flown with focuses on passenger comfort! But more than that... Safety.

    Thanks so much for your comments!

  9. if you are below the profile, how do you get back on the profile?

  10. so does the autothrust automatically add thrust?

  11. If you get too slow. Yes. But, there are different levels of automation. Your plane, if managed correctly, will not get behind profile. If you do it, and the plane is doing what you want, it won't just add thrust because you're low. It all depends where you are, what level of automation, what approach, what you have programed, etc., Not a cut and dry answer.

