Author Topic: the flare, the horror  (Read 2761 times)

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Offline Adrian Chitan

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the flare, the horror
« on: December 02, 2013, 08:19:49 AM »
Hi, guys

I want to draw attention to one of my own horrors when it comes to flying: the flare. While in small aircrafts (under 737) it comes natural and I can do a pretty good timed flare, in the 737 and above I find myself pulling to hard and soaring over the runway then correcting by putting nose down (the A/T keeps the airplane at REF speed until touchdown), which gets me into a vicious circle because I'm hastening for a quick touchdown (the runway is loosing length very fast) so I usually end up with a high landing rate (200-300 fpm). I actually managed to go under 70 fpm on one occasion and under 100 fpm for some, but it seemed like luck.

My last landing was in Helsinki's Vantaa airport, rwy 33 RNAV app on 24 kts wind gusting at 37 kts. I actually did a nice visual approach from 15 NM out (I don't have any problem following some PAPI lights, when they disappear I have a problem with :D). I bounce-landed with the first bounce at over 700 fpm because I had the added workload of keeping the plane on the rwy.

I have to admit I haven't got to the flare part of the manuals put here by Bogdan, but I wanted to know HOW DO YOU DO IT?

Cheers and safe landings (unlike my last one).

P.S. I thought that we had a limit on the landing rate (> 700 fpm was considered a crash landing and didn't count), but my PIREP with -787 fpm was accepted. I would really like to have the landing rate limit reinstalled :) if possible.

Offline Bogdan Ghincea

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Re: the flare, the horror
« Reply #1 on: December 02, 2013, 10:03:11 AM »
I dont know if it is correct or not  but this is what i do:  When the autopilot calls for 10 feet above runway i put engines on idle and activate the reverse thrust and let the airplane touchdown by itself. You can give a try like that and let me know the results.

Offline Adrian Chitan

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Re: the flare, the horror
« Reply #2 on: December 02, 2013, 01:01:55 PM »
I tried your version and it actually helped. Even if I over correct the pitch angle (as I usually did), there is no A/T to accelerate and drastically increase vertical velocity, and the plane keeps descending at a slower and slower rate. In actuality, the A/T should be disabled before touch down, so you are right. And because you're going to rev thrust while at merely 10 feet above the rwy, the reversers don't actually come on before touchdown (the reversers' doors have to be opened first) - you aren't allowed to go to reverse thrust while airborne. So everything is OK from this point of view. My problem was a "huge" amount of lift when I didn't need it because of the A/T.

I landed at Arlanda with 117 fpm :D (manual and visual from 20 NM out).

Thanks.

Offline Bogdan Ghincea

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Re: the flare, the horror
« Reply #3 on: December 02, 2013, 02:39:31 PM »
I'm glad that you find it helpfull. If you can improve that technique please let me know.

Offline Adrian Chitan

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Re: the flare, the horror
« Reply #4 on: December 02, 2013, 06:22:35 PM »
OK, your technique changed everything. Just landed at EDDS with -72 fpm. Happy days are approaching. Auto-Land is out.

If I find anything new about this in the FCTM I will post it here.

Thanks again.

Offline Bogdan Ghincea

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Re: the flare, the horror
« Reply #5 on: December 02, 2013, 07:48:07 PM »
As the russian guy in 2012 the movie would say "Good...very good" :)

Offline Mircea Paraschiv

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Re: the flare, the horror
« Reply #6 on: December 12, 2013, 11:38:43 AM »
Well, try this technique:

    A typicaly well accepted vertical speed on touchdown for a jet airliner, is between 300 and 500 fpm as you don't want to "float" on the runway. For an auto land, the VS is around 170 fpm. Normally (no auto land), you should disconnect the A/P and A/T no later than the MDA or DH. At 50 ft AGL, flare the aircraft (that is, gently pull the stick until you acquire the desired VS) and at the same time pull the throttle to idle. With enough practice you will master this technique in no time. I hope this helps, cheers.  :)

Offline Adrian Chitan

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Re: the flare, the horror
« Reply #7 on: December 15, 2013, 10:47:30 AM »
Thanks, Mircea.

I actually read through the FCTM manual and you're right. I haven't done an autoland in some time now (though my landing rates are not always "great", but they're under 200 fpm - sometimes I hurry the landing and get 400 fpm). Anyway, I disconnect A/P when I get established (so quite a large distance from the threshold and follow the ILS markers). I usually leave the A/T on until the 10 callout (Bogdan's version).

I had some no-A/T available approaches (I fly with the automatic failure on - 5 failures for every 10 hours of flight) and it wasn't that hard to maintain speed. So I'll try your version, and disconnect it sooner, while at the 10 callout I'll put them in reverse.

Thanks for all your help, I think I am on my way to mastering the flare in the big jets.

Cheers.

Offline Bogdan Aur

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Re: the flare, the horror
« Reply #8 on: August 30, 2014, 07:31:51 AM »
Boeing - 737-600   

Approach-Landing

 Landing Gear : CHECK DOWN
 Autopilot and  Autothrottle : OFF
 Landing Speed  :140 KIAS
 After touchdown Apply Reverse Thrust. At 60 kts Cancel Reverse Thrust
 Spoilers VERIFY EXTENDED
 Brakes AS REQUIRED
« Last Edit: September 01, 2014, 10:14:48 AM by Bogdan Ghincea »

Offline Bogdan Ghincea

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Re: the flare, the horror
« Reply #9 on: September 01, 2014, 10:16:34 AM »
140 KIAS landing speed is actually an exact speed ?  or a safety approximation speed?

Offline Adrian Chitan

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Re: the flare, the horror
« Reply #10 on: September 02, 2014, 04:52:25 AM »
Hi, Bogdan G.

It is an approximation. No landing is ever the same as the next one, given the weather and all. The FMC will calculate a VREF speed to which you add 5 knots. This should be your final approach speed. It is usually around 140 KIAS  for a 737 (-700 and upward) but you should check the FMC. In a very heavy 737 you can also find this speed to be near 150 KIAS.

Furthermore, if the weather is gusty or you land in a tail wind scenario, the approach speed is even higher. So you have to go through the manufacturer's manuals and calculate your own. As an example, a very gusty wind can make the approach speed be increased by 20 knots.

Cheers.

Offline Bogdan Ghincea

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Re: the flare, the horror
« Reply #11 on: September 02, 2014, 03:25:19 PM »
Hmm. Thanx. Good to know. There are many factors that influence your landing. Including Speed and maybe also autobrake level depending of available runway length but also depending on the approach speed as you mentioned i guess

Offline Adrian Chitan

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Re: the flare, the horror
« Reply #12 on: September 02, 2014, 04:23:49 PM »
Hi, again

The whole landing preparation requires more stuff than just the approach speed. You first have to choose a rwy and an arrival pattern (STAR or by conventional navigation). Then the FMC will give you an approach speed based on your aircraft's weight. After this you have a judgement call. What A/B setting you need to use. First of all there is a normal (usual) A/B setting that's described in the manual as the normal setting. For a 737 (PMDG) it is 2. For a 777 (PMDG) it is 3. Now you have to look at your rwy length (actually the length between your usual touchdown point till the exit you want to take). If it's short then go with a higher setting. Even if you have enough room to stop after touchdown but you have a high final app speed (like when landing with a low flap setting, or when you're very heavy) you will still put in a higher setting. Stopping a plane is still one of the biggest problems in aviation.

And bear in mind the weather speed correction. If your FMC has calculated a VREF of 142 knots, but you have gusty winds on landing stretching up to +/- 15 knots than you have to account for that drop in speed of about 15 knots. So the safest VREF would now be 157 KIAS (this is the worst case scenario when the wind is directly from the front, but still). Otherwise you will find yourself in the yellow part of the speed tape with only a maximum of 5 degrees of bank before you STALL. Anyway, remember that "heavy and fast" has a lot of energy to bleed off.

Offline Bogdan Ghincea

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Re: the flare, the horror
« Reply #13 on: September 03, 2014, 09:48:48 AM »
I just love your answers :)

 

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