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Some landing advice please. A320

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Some landing advice please. A320

Old 21st May 2013, 10:57
  #121 (permalink)  
Join Date: Feb 2013
Location: The Wood
Posts: 248
And some aircraft, especially those with very low nacelles (737) or engines that are far outboard (747)
Airbus aircraft are always nice and high on the strut giving plenty of roll clearance. I believe if the drift angle is 5 degrees or less they say decrab isn't required. So that'd be perhaps just over a 10 knot crosswind.

My advice for landing the 320 is to keep your aim point at a third screen height - keep it there as your reference all the way down to 50 RA. All the while using your peripheral vision get a feeling for your ROD. At 50 RA look further down the runway and close the thrust levers promptly at 30 RA. (I go for 40 RA with a stiff enough TW or just under 20 for a stiff enough HW).
WhyByFlier is offline  
Old 23rd May 2013, 12:32
  #122 (permalink)  
Join Date: Mar 2007
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Posts: 562
Crabby Old Boeing.

Mr Boeing has cleverly and simply assisted the X-wind impact problem by fitting damped castoring main gear to the 737 variants, presumably by employing the K I S S principle when it comes to design?! Hence the impression of taxying with drift observed by following craft!

Therefore the 'frame "owns" the first 15 knots of X-wind, as in the autoland case, and the bonobo chimp at the controls only has to hack the remaining 18-20 knots, depending on the variant. This news seems to reassure the "newbies" who understandably get twitched when they work out the X-wind component about to be faced.

I dread to think what Toulouse would have cobbled up by way of a solution, involving wiggly amps and actuators and various "laws" which engage when least expected!

But we appear to have drifted off (pun intended) from the O Ps request for advice, and I'm longing to be educated as to why Toulouse decided to design the 'bus to behave so in the last 50' just before impact, as per my previous posting?
BARKINGMAD is offline  
Old 23rd May 2013, 16:46
  #123 (permalink)  
Join Date: Oct 2007
Location: America
Posts: 91
...why Toulouse decided to design the 'bus to behave so in the last 50' just before impact, as per my previous posting?

Simply put - so that the pilot feels like he's flaring the aircraft. The logic after 50' will compel the pilot to add back pressure like he normally would in a non-FBW aircraft.
junebug172 is offline  
Old 25th May 2013, 12:39
  #124 (permalink)  
Join Date: Jun 2007
Location: Wanderlust
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The principal of Airbus FBW is that the AC will do the trimming except in Direct Law, also in roll upto 33 degrees it will hold the bank and pitch . This makes flying very simple, you just create the pitch and bank you desire and leave the stick till you wish to change the picture. The AC behaviour from 50 feet you described is called flare mode. Now imagine trying to land this aeroplane without the flare mode. When you flare the AC would have continued to pitch up and auto trim as long as the sidestick was out of neutral. So everytime you raised the nose you would have to keep neutralising the side stick. Also if you flared more and pushed the stick forward it would have auto trimmed downwards. This AC responce is not going to produce good landings with consistancy. The Airbus created the flare mode in which at 50ft RA it stops trimming, at 30 feet it will memorise the attitude and start pitching down wards so now you can keep the back pressure as required without releasing the stick and keep increasing it as the nose keeps dropping. The main problem initially is getting used to the very small input that is needed on side stick as compared to conventional AC where the pressure and amount of movement of the yoke are much larger. However without bothering about the theory if you proceed with landing as any other AC you can get good consistant results.
vilas is offline  
Old 25th May 2013, 13:57
  #125 (permalink)  
Join Date: Mar 2007
Location: Another Planet.
Posts: 562

Vilas, sincere thanks for explaining the 'bus philosophy on landing mode(s).

It worries me that such designs seem to ignore the poor chimp who's trying to ignore thousands of years of evolution and is trying to think and operate like the machine?

A case in point is the research done years ago, following the introduction of digital watches, which implied that those who used them were consciously or unconsciously "translating" the digits presented into analogue form.

The recent fad for "track up" similarly ignores the fact that the chimp is sitting aligned physically and mentally (well most of us are!) with the longitudinal axis of the airframe and the new presentation is proving confusing to some. The same confusion has been expressed by new F/Os on type (737NG) so it's not just because I'm one of the old codgers raised in the "steam" days.

Of course the "track up" issue is another potential thread, but again thanks for a very lucid explanation of the 'bus way of doing things.
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