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Detail question about the (old) RW A320


BudSpencer

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Hi!

 

I have a few detailed questions about the A320 that maybe some of you experts could answer here:

 

By coincidence I just watched a "Mayday" episode about the A320 crash at Habsheim airshow in 1988, one of the few I hadn't seen before. Therein the investigators were first unsure if the "landing mode was automatically activated" because the airplane was so close to the ground and thus "preventing the pilots to give effective climb inputs". Later they discovered that only the Alpha floor activated which led the elevators to pitch down despite pulling at the sidestick - which makes sense at the low airspeed according to the logic of the Alpha Floor.

 

But: Concerning this "landing mode"?? I think I roughly understood how FBW/Alpha floor is working: The aircraft corrects inputs from pilots that would lead to a stall, an overshoot of the bank limits,... by adjusting pitch, roll and thrust so that the aircraft stays within its structural and aerodynamic limits in critical moments, right? ...which was also nicely modeled in the Aerosoft bus and even partly long years ago in the Wilco buses.

However, several investigation episodes about newer airbuses led to the impression (at least for me) that the airbus flies and lands itself without any more control of a pilot if it feels to do so. (It even feels a bit frightening when you hear that)

 

What's behind this magic "landing mode" or several other automatition modes in the airbus? Another example is the investigation of the Air Inter Crash at Strassbourg, where the aircraft obviously "automatically corrected some upwinds by pitching the aircraft steeply down". Is it an automatition that is just too complicated and/or that makes too little sense to simulate so that no one ever mentioned it here? Or is it just a (partly) failed try to simplify "Airbus-specific" systems for the average TV watcher?

 

Several other episodes that involved other aircraft types always made sense to me in every aspect from what I know about aviation from my hobby simmer's viewpoint.

 

Thanks in advance!!

 

Cheers, Dominik 

 

 

Edit: BTW, just one more question on that: The pilot claimed they couldn't hear the altitude callouts because of the headphones and because of the aircraft noise? Don't pilots ALWAYS have their headphones on while landing?? And doesn't the aircraft make the same "noise" at every landing?^^

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Well to cut things short, the pilot screwed up big time and blamed Airbus for the catastrophy. Not only did he plan to sink below the recommended altitude for a low pass (30 ft instead of 150 ft), he also didn't do a thorough briefing. Otherwise, he would have noticed the forest right behind the air field.The forest wasn't showing on the approach plate, but as he descended towards the airfield, he should have seen the trees being obstacles in his climb out path. Poor airmenship on behalf of the copilot as well - flying so low, you wanna make sure to rely on the radio altimeter rather than the Altitude Indicator. If it's hard to read, bend forward a little. Even if the Airbus touched down completly, they could have flown a so called touch and go procedure hadn't been trees in their way. And indeed, there is a minute lag for the engines to go from idle to TO/GA, but that's known to all Airbus pilots and part of the FCOM.

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Basically the low pass should never have been flown in that particular situation:

 

  • Pilots weren't thoroughly briefed by their airline (briefing was only written and "last minute").
  • Pilots weren't briefed by persons in charge of the airshow (trees anyone?)
  • Pilots had passengers on their plane (airshow stunts? With pax aboard? Seriously???)
  • Airline knew about deficiencies of engine spool-up at low height, but hadn't yet informed their pilots (deficiencies beyond those allowed in the certification process)
  • Airline knew about deficiencies of the barometric altimeters, but hadn't yet informed their pilots
  • Pilots were basically conducting an "unstabilized approach", as they noticed the field too late, were too high, had to sink fast, and arrived slightly above field elevation with their engines more or less at idle.

I am not quite sure about the "landing mode", but increasing engine thrust from a stabilized approach to go-around thrust is a couple of seconds faster than having them to spool up from (approach) idle conditions.

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A few more items:

 

  • the Habsheim accident report in English: https://reports.aviation-safety.net/1988/19880626-0_A320_F-GFKC.pdf
  • From the FCTM: "ALPHA floor is available, when the flight controls are in NORMAL LAW, from liftoff to 100 ft R/A at landing. It is inhibited in some cases of engine failure." So ALPHA floor automatically disengages during landing when below 100 ft radio altitude.
  • The Air Inter crash supplies an example of how the Airbus (wo)man-machine interface has been improved: Vertical speed now has a four digit readout that cannot be confused with the FPA readout anymore. (But the wheel for adjusting fpm or FPA still spins the wrong way - counter-intuitively - as opposed to the logic employed in Boeing planes, for example!)
  • For what the FPA autopilot mode can achieve and what not, this Air Canada flight accident report provides some valuable insight, too (starting on p.57): http://www.bst-tsb.gc.ca/eng/rapports-reports/aviation/2015/a15h0002/a15h0002.pdf
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