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tailwind landing

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tailwind landing

Old 14th Aug 2017, 10:23
  #41 (permalink)  
 
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What would your question be, exactly ?

The case of rising terrain is some fun :
The vertical speed change required to achieve a smooth landing is higher (you have to add groundspeed*upslope to your normal reduction of about 700fpm, or GS*approach slope), but the RA indications are also higher than the actual height above the threshold (since the threshold is above the ground that's before the runway).

Iraklion is a good example of airport prone to hard landings, with a cliff and an uplsope.
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Old 14th Aug 2017, 10:39
  #42 (permalink)  
 
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What's the lowest altitude you can start a flare and still make a proper landing ?
Depends on the airport elevation.
That made me spill my coffee

I hope KayPam et al. can appreciate the occasional sarcastic jokes in this thread instead rather than taking it personally

KayPam, the flare is very much black magic, a seat of the pants skill that cannot be thought by reading a book. A slow flare from 50 ft may have the same result as an aggressive flare from 15-20 ft. I sometimes brace myself for impact as we come down and I cannot detect any appreciable flare from my colleague. Expecting a real crusher. The result? A kisser. The landing is one of those things you never get better at over the course of a career
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Old 14th Aug 2017, 10:48
  #43 (permalink)  

Only half a speed-brake
 
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Jeez. WTF is groundspeed upslope? The last people who tried to use RA for landing profile wiped all of the Polish executive, what are you advocating?

People on this thread have more landings in MAN 23R and HER this month alone, than you've seen naked women in your lifetime, probably websites included.

Be a man, answer my question about 50 RA autocallout being the correct gate for sucessful landing when pilot is over the runway designator. Bonus points for identifying this one: https://1drv.ms/i/s!AiE0Si5ywRcJgvNCmz1U5ax3h8nShw

Last edited by FlightDetent; 14th Aug 2017 at 10:58.
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Old 14th Aug 2017, 12:30
  #44 (permalink)  
 
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Groundspeed upslope : nothing.
Groundspeed * upslope is going to be your vertical speed while traveling at a given GS on a runway that has an upslope.

From an engineering point of view, a flare is going to be an increase in lift that is going to create in increase in load factor (vertical acceleration). This load factor (typically 1.05 to 1.15g) will change the vertical speed according to the physics formulae.

If you have a runway upslope (that's also mentioned in the FCTM) you will have to make a larger change in vertical speed and hence will require a longer flare (or more pronounced)

I'm not advocating to use RA for landing profile, of course not. However I've noted several pilots writing that they waited for this or that RA callout to start their flare.
As 172 driver pointed, flare is a complex thing and the pilot's and the engineer's point of view are very different : one is sitting at his desk looking at curves, taking one hour to analyze ten seconds. The other one is in a moving machine in real time.. Plus the flare will induce vertical accelerations in the flight deck that are absent at the airplane CG (due to the flight deck being so much forward of CG)
So when the engineer is tired of analyzing he will just say "flaring is (basic) airmanship, and hence does not need to be taught by the manufacturer"

As for you question ..
I'm guessing its a trick question since an airplane is supposed to be at 50ft over the runway threshold.
However, in an autoland (I'm choosing this because they should be more similar to each other than manual landings) the aircraft will descend on the glide slope. So basically the ILS antenna will follow the glide slope down to a certain altitude, then the aircraft will freeze its flight path angle down to flaring. Flare should occur below 50ft in normal conditions.
Since the gear is lower than the glide antenna and since the radio altimeter measures height from the ground under the tail up to the gear position (while correcting for pitch angle, but only for certain things like RA display on the PFD), you should get the 50ft RA callout before. A few tens of meters before.
That's if and only if my assumptions about the different sensors, etc.. are correct.

For instance, they may have introduced a correction so that the CG and not the antenna follow the glide path.
But we're starting to go into details that would require several tens of minutes to check them for certain.

If we're talking about a visual approach following the PAPI.. that's another story
If there is a ground slope near the threshold, this will change things as well


P.S. Without claiming it particularly high or low, I'm happy with the number of naked women (both real and websites) I've seen
Originally Posted by 172_driver View Post
I hope KayPam et al. can appreciate the occasional sarcastic jokes in this thread instead rather than taking it personally
Yes, this forum is good fun (see the line just above your quote)

Last edited by KayPam; 14th Aug 2017 at 13:08.
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Old 14th Aug 2017, 13:16
  #45 (permalink)  

Only half a speed-brake
 
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It was a trap. To see if you actually can read the FCOM.

The RA callout when the "pilot is over the numbers" needs to be 30, as the RA is aligned with MLG that would pass the THR at 34' on proper 3 deg profile. Reference FCOM landing geometry,

On longer (2400+) runways, PAPIs are aligned at 66 ft (or even higher) over the landing threshold due to their longer lateral displacement. That has the potential of forming a habit of aiming far, and in turn creates a need for a personal short-landing technique. And with that second one a hole in swiss cheese is formed!

VVTS07R.visual_aim_point.jpg
FCOM.320.PRO-NOR-SOP-19A.jpg
Annex.14.RWY_2400m.JPG

In the respect of this "tailwind" thread, a good landing to be proud of is one at the correct point and proper speed. Kinetic energy and pavement length remaining, that is all that matters. And not overly easy to achieve. Ok, bins stay closed and coffee pots do not get ejected from housings.

My previous numbers are more suited for 319 with 44t, for commercially laden A320 they better be 5 ft higher, that is true. However hard landing is something above 1,9 g, no danger of that.

If you are looking for a kinematic explanation of smooth touchdowns, ... as you are the only one to mention the word and did twice already, ... good luck.
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Old 14th Aug 2017, 14:56
  #46 (permalink)  
 
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Wow, some of the explanations here confuse me.
IMHO: If runway length is not a concern, flaps 3 or full whatever makes you happy.
If runway is kinda short: flaps Full, duck under a bit if you are insisting for a soft landing.
Very short runway: Flaps full and aim for the numbers just like in the bush xD. Keeping in mind you are seating 15 feet+ above the main gears and that they are well behind you. Now I will brace myself for the safety officer freaks who insist on the 50 feet over the threshold.

Last edited by pineteam; 14th Aug 2017 at 16:04. Reason: Typo
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Old 14th Aug 2017, 21:17
  #47 (permalink)  
 
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Please tell that to the manufacturer's head of customer support.
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Old 14th Aug 2017, 22:19
  #48 (permalink)  
 
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I'm obviously very stupid. I thought that the aircraft currently built by Airbus would fly according the manuals they publish. The performance described in their manuals could met by the crews specified in certification standards (ie. average pilots under the worst of circumstances). But obviously not. Some super-heros haven it upon themselves to do some of their own flight testing and in contradiction of the manufacturer's testing and published procedures, decided to impose more restrictive operating procedures. God, I wish I flying with people like this. I'd learn so much!

I do hope they have informed their companies of these 'extra' , beyond manufacturer limitations. Any delays, cancellations etc. as a direct result of these smaller goal posts may well result in additional compensation payouts, i.e. If you impose greater restrictions, you should pay the price.
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Old 14th Aug 2017, 23:54
  #49 (permalink)  

Only half a speed-brake
 
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What are you on about, PM?
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Old 15th Aug 2017, 08:17
  #50 (permalink)  
 
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Originally Posted by FlightDetent
Bonus points for identifying this one: https://1drv.ms/i/s!AiE0Si5ywRcJgvNCmz1U5ax3h8nShw
KGS-LGKO (That was too easy)
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Old 15th Aug 2017, 08:41
  #51 (permalink)  
 
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Piltdown man can only land from a 3 degree standard FCTM approach?
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Old 15th Aug 2017, 10:41
  #52 (permalink)  
 
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Thank you Penko. You have guessed correctly.

I think I have been misunderstood. To my knowledge all modern aircraft are flight tested to ensure that they can be safely operated by appropriately trained average pilots, not super heros. Manufacturers will also flight test various configurations and publish the results. Not all configurations will be approved for normal landings. At the same time performance data will be produced for configuration. As line pilots we fly using this data with additional margins added to the basic numbers. Some margins are added by legislation, others by companies.

Which configuration should you use? Others have already answered that question.

But my point is that having certain manufacturer approved configurations denied because of company policy does not make sense. Should incident and QAR data imply that certain configurations result in more 'events' then that is something that should be taken up with the training dept. and/or manufacturer because this is something that should not happen.
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Old 15th Aug 2017, 15:15
  #53 (permalink)  
 
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Originally Posted by sabenaboy View Post
KGS-LGKO (That was too easy)
One easyjet airbus still remembers its visit there
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Old 18th Aug 2017, 22:10
  #54 (permalink)  

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Close, but no easy cigar. Better precision required to discuss a topic such as this, really.

While the key lesson from that report is the systematic lack of training follow-up with the student, Kos truly does have illusion prone terrraing profile raising towards the threshold in a creepy way. In HER, not so much, different issues there.

Meanwhile in the region...
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