tailwind landing
To the Airbus gurus in this forum:
Let's assume a long and dry runway (e.g. >4000 m) and a relatively light weight A320. Considering landing distance is not a concerning factor, what would be the best or recommended landing configuration in a tailwind situation? Flaps 3 or Flaps Full? Without thinking too much, most common answer is flaps full. But according with my experience I tend to believe that the "cleaner" configuration allows a much better and smoother handling. Thanks |
I presonally don't like Conf3+tailwind combination on the A320, due to tail clearance issues. In TW conditions you carry no extra speed, so have a higher approach pitch attitude to start with. Then, since you have higher ground speed and sink rate, you need even more pitch during flare... These effects combined leave not much room for mishandling which can happen on a bad day.
So, for my personal comfort Tailwind=Conf Full, even on a long rwy.... |
The length of the runway = the distance to the planned exit!. Plan accordingly.
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Say the wind at 500' is a 30kt TW and the wind on the runway is a 5kt TW. Flaps 3 probably won't have enough drag to decelerate the aircraft during the approach as the tailwind dies and maintain whatever stable approach SOP's you use. Hence, despite the fact that you can make a smoother landing, can you make a safe approach?
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Smoother landing could be the last thing on mind in tailwind. First because of the higher ground speed you feel closer to the ground than you are and tend to flare high. If that happens the float seems eternal and you would rather call it a day by putting it down. If you can flare little lower and little less than normal, a smooth landing is possible on the correct touch down point. On a long runway if you flare high as I said before and float then the factor C_star is talking comes into play. It depends on how much finer seat of the pant feeling you have. That is the only skill left in the airbus rest is automatic and done by computers.
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I don't know that I've noticed all that much difference. Then again, I usually only use Config 3 when the airplane is so light that the Vapp for Config Full is embarrassingly low.
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Company policy is to ban Flap3 landings in the A320 but we can do them in the A321. We fly some very heavy 321s (Cat D)so I would be be reluctant to reduce the flap setting with a tail wind. The thought process is how much energy you are trying to disspate on touchdown so why hammer the reversers and brakes to save a few kilos of fuel by landing with reduced flap.The touchdown quality doesn't seem to be any different.
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Hi C_Star,
Then, since you have higher ground speed and sink rate, you need even more pitch during flare... If you were on say a 3 degree slope, then flare by 3 degrees, you would fly level (with same IAS). Surely all you have to do is commence the flare earlier due to rate of descent? |
The way I understand it - with tailwind you'll have higher sink rate for the same glide path angle.
To arrest higher sink rate you either need to flare higher, or more aggressively. Hence, in my opinion at least, there's increased potential for tail strike, esp. if you get the flare height wrong... Increasing pitch by 3 degrees to fly level with the same IAS works in steady state, not in flare, where you need extra lift to change the flight path. Then add another degree or to of pitch to compensate for decreasing speed during the maneuver... |
All theory aside, an A320 will tend to float with any kind of tailwind. Hardly any flare is needed with a max TW. If you flare, you'll float.
F3 or Full? Personally I will only consider F3 in the most benign tailwind conditions, i.e. stable tailwind, no thermals, exactly on profile. If you get high on profile with a tailwind and F3, you WILL loose speed control. Same with thermals, your speed will run away with the engines at idle all the way down, especially in the A319. |
Cough, Why do you say you won't have enough drag? If you have at 500 ft 30 kts tailwind and at 50 ft 5kts tailwind you will need thrust not drag...
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Err...no.
A reducing tailwind is an example of overshoot wind-shear, and you would indeed need less thrust/more drag. |
If Tailwind reduces from 30 kt to 5 kts, due to inertia, KIAS will increase 25 Kts. Yes you need drag for deceleration.
if you are approaching with F3 and TW, pitch attitude or cockpit perspective will be relatively close to the Full Flap and No TW. That could be good for landing, provided more pitch up required during flare. |
Why for god sake would you do a F3 landing? On a 319 for practice purposes yes just to keep used to the picture as quite a few non normals require F3 for ldg. But why would you do a F3 in a 320 with tailwind?? Its harder to get the a/c speed stable. It feels like the a/c is hanging in the sky and speed fluctuations are much more present then with F-full. With some bad luck you end up with thrust in idle on short final. Even in gusty conditions i am not a fan of F3 but thats personal. Flare gives less margin for error and the possibility for a "pitch" callout increases big time. Only in very few situation I prefer F3 but otherwise I dont see the benefit!
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Some people above have said that little flare is required with a tailwind.
Why would this be the case when you typically have a higher ROD to maintain the glide? |
Anyone who deals with real world repetitive tailwinds, will attest to the fact that a standard flare WILL result in a float. After a while you get a feel for it. The only way I can describe it is that the aircraft is quite reluctant to settle down. After a lot of trial and error it becomes predictable and you will know just how little of a flare you need for a perfect tailwind landing.
Why? One of my theories is that the indicated airspeed (IAS) increases on a tailwind landing. Think about it. In a headwind landing you will often loose a few knots during the last 30 feet of the approach due to the decreasing wind. The same happens during a tailwind, however as usual, a reduction in tailwind will lead to an increase in IAS. And it is this increase which will lead to a floating tendency. This is just my theory, nothing else. Other avenues to explore are the higher ground speed and its effect on ground effect.. |
Normally I close the TLs at 30 ft, flaring at 15. With tailwind, the best results for me is to close at 45-40, flare only slightly at 10. My theory is the same as PENKO's.
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‘P’, the point you overlook is that there is no ‘standard’ flare. Landing is not an open loop step input, but a dynamic reassessment - how goes it, involving adjustment for the start and during the manoeuvre. We learn and improve with practice of how to adjust our inputs during the flare.
Some theories suggest that the assessment involves the comparison of height and height rate, with feed back including pitch attitude, and stick displacement or force. Further moderation and feedback involve time and most important projected point of touchdown. The Landing Flare of Large Transport Aircraft. For the OP, if you do not wish to follow the maths in the report, at least scan the many figures at the end which may provide an answer; at least an education every time I look at them. My safety view is that distance is always a factor, smoothness is just a resultant nicety of practice. It may be easier to gain experience from practice by concentrating on one normal flap setting. |
Safetypeee, of course it crossed my mind that it might all be an illusion. But how do you explain the fact that in a ten knot tailwind you can almost fly the plane down to the runway without any flare? The effect being a buttersmooth landing, of course. Don't do that with a headwind!
*disclaimer: the above is my experience, after more than 300 tailwind landings in just a few years in a very tailwind prone base. Use your own flare technique, but keep in mind what I wrote, and adapt from there on. In no way do I prescribe an non-standard landing technique! :) |
Originally Posted by FlightDetent
(Post 9859227)
Normally I close the TLs at 30 ft, flaring at 15. With tailwind, the best results for me is to close at 45-40, flare only slightly at 10. My theory is the same as PENKO's.
The FCOM says that a late flare will likely result in a hard landing. Especially if you retard the thrust levers high, you will tend to lose speed hence reduce the flare efficiency.. So could you tell us more about your landing technique ? Thanks |
Are we talking IAE or CFM engines? The difference couldn’t be bigger.
The IAE are small, but have high residual/idle thrust. CFM engines are larger, but have much less idle power. You can retard the thrust levers on an IAE A320 at 70 ft no problem, and airspeed will hardly decay. In a tailwind condition there is a pronounced tendency to float. With CFM engines it is not advisable to retard them higher than say 20 ft, because as soon as they spool down the bus is going to sink like the titanic. |
The math does not need to be complex to understand of the differences.
--- start part one --- An average A320 with 140 PAX will have approach speed of 130 knots. If the aim is to bring the aircraft from 50 ft ILS THR crossing height to an identical touchdown point (say) about 450 m down the pavement... ... given just 3 knots of TWC vs. HWC ... the kinetic energy to be managed is 513 MJ compared to 468 MJ. Now, the aircraft aerodynamically still flies Vapp = 130 kt at the beginning of the manoeuvre, so the "steering powers" of the pilot are essentially the same, however we drive a very different beast. It seems rather unavoidable that a different set of inputs is required to obtain the same desired trajectory. ---- end part one ---- --- start part two --- The manufacturer explains that typical loss of IAS during the flare is 7 kts. Somewhere between 30 and 10 feet, the wind does slow down by approximately 3 knots (my empirical observation). 10 feet being the reported anemometer value and close to bottom-of-flare, i.e. 3 kts on ground, 6 kts at the top of the flare. Due to aircraft inertia and the short time-frame when this happens, relative airflow changes and that translates to change in IAS. Thus for a headwind situation: the partial loss of the component when entering the boundary layer over the ground "takes away" 3 knots and the pilot flies the flare whilst slowing down by 4 knots by his own making. In a tailwind situation the loss of tailwind relative to the A/C creates an increase of IAS by those 3 knots. Here the pilot needs to fly the flare so to reduce IAS by 10 knots. --- end part two --- If we would discuss a situation of +/- 5 kt on the ground, I dare to draw the following illustration: --- figure 1 (imagination required) --- IDENTICAL for both TWC and HWC: An aircraft of 58 tonnes and IAS 130 kt follows an asymptotic trajectory from ILS THR crossing height of 50 ft to a touchdown point 450 m down the runway. DIFFERENT: HWC: The kinetic energy is 432 MJ, and we need to slow down by 4 knots. TWC: The kinetic energy is 552 MJ, and we need to slow down by 10 knots. ---- end --- DISCLAIMER: None of the above should imply me advocating techniques outside the FCOM / FCTM guidance. On the contrary, myself I am a hard core believer in chapter, verse, word and letter of those books (with logical exceptions :)). My claim is that a different colour of magic is required to achieve a similar result, just like two instruments playing the same acoustic tone. WARNING: The above applies, in my opinion, even before we factor in the FLARE MODE and dynamics of handling the thrust levers on Airbus FBW designs. And that’s another potful of jambalaya! CONFESSION: For those TWC landings that I am proud of, I personally cannot manage as described above. The touchdowns are flattish, at Vapp to Vapp -3. ---- to the OP --- busav8r: I sympathize and feel the thrill of mastering tailwind landings with F3, the art and geekiness of it, honestly I do. At the same time, may I suggest to leave that animal locked-in with a blanket over the cage? It is a skill of zero practical benefit and anyone attempting to learn it, use it, or show it off would be considered foolish by my professional idols, mostly because a chance was lost to train something meaningful to your(my) self instead. Hope you won’t mind, let me raise one to make all of this little worthwhile: What is the PAPI MEHT for standard ICAO runways longer than 2400 m? |
Because you've got more kinetic energy, and more downward kinetic energy (downward speed) : you should apply the flare force (lift higher than weight) for a longer time, so you should flare higher : this is as per FCOM.
So what would be your typical flare heights in headwind and in tailwind ? My understand of the tendency to float in tailwind is that the wind will tend to reduce close to the ground, so less tailwind will increase CAS hence will improve lift and prevent the A/C from landing. Plus in ground effect the induced drag is progressively reduced. |
I might end up flying the A320 soon. Pls tell me it's possible to land the thing, in tailwind and headwind, without having to read the FCOM "how to land"... :(
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Landing without reading FCOM? Passengers are not allowed in the cockpit. You better stick to whatever you are doing,
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With a tailwind, your groundspeed will be higher, V/S will be greater to maintain a 3 degree descent and your pitch attitude will be lower.
To achieve the same "smoothness" in touchdown you will need a bigger change in V/S and pitch. So to achieve the same smoothness you don't need "less flare" but "more flare". It's understandable that pilots will tend to flare earlier in a tailwind situation to break the increased rate of descent. Combine that with the increased groundspeed and most pilots will tend to land longer (or float).
Originally Posted by someone
Hardly any flare is needed with a max TW. If you flare, you'll float.
If you're aiming for a smooth touchdown on the blocks without floating in max tailwind, you will need to flare more (larger pitch change) and later then usual. (=larger pitch change in less time) =not easy. To get back to the original question in post 1: prefer flaps full for tailwind landings. |
KayPam: what a nice little bully you are. Those nubmers were posted already. Would you like to share how many 13 kt tailwind landings onto runways with LDA below 2200 m at 74 tonnes you have made in the last monsoon season?
You come across as a knowledgeable person but lately made several claims about FCOM that are not there. And seem to have missed my omisson of GSmini altogether. Maybe you can at least verify your credibility by agreening on this: it is correct to have RA callout 50' over the numbers. Hm? 172_driver Absolutely yes. Bring the aircraft to the threshold stable and on speed, keep pointing to the aimpoint. Close the TLs soon enough to prevent A/THR from kicking the N1 up once you begin to flatten the trajectory. Enjoy a second or two of adjusting the backpressure on stick, and she settles eventually between 5-3 feet. Apply the usual magic next. |
I might end up flying the A320 soon. Pls tell me it's possible to land the thing, in tailwind and headwind, without having to read the FCOM "how to land"... Anyway, do we really need to overthink everything? It is, despite all the noise about it being an airbus, simply an airplane in the flare. Look out the window and simply land the damn thing, (nearly) same as any other airplane. |
Originally Posted by FlightDetent
(Post 9860525)
Would you like to share how many 13 kt tailwind landings onto runways with LDA below 2200 m at 74 tonnes you have made in the last monsoon season?
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Originally Posted by FlightDetent
(Post 9860525)
KayPam: what a nice little bully you are. Those nubmers were posted already. Would you like to share how many 13 kt tailwind landings onto runways with LDA below 2200 m at 74 tonnes you have made in the last monsoon season?
You come across as a knowledgeable person but lately made several claims about FCOM that are not there. And seem to have missed my omisson of GSmini altogether. Maybe you can at least verify your credibility by agreening on this: it is correct to have RA callout 50' over the numbers. Hm? Tomorrow and the day after tomorrow are bank holidays but maybe wednesday when I'll have access to a proper FCOM or FCTM I'll be able to quote the exact sentences. If your companies allow you to access this documentation without being on the job.. then just look at the FCTM SOPs : landing/flare part. It will state the normal flare height, state that tailwind conditions, ascending runway or steeper approach path require an earlier flare, etc.. There's like a whole page of it. 13kt tailwind on a wet/contaminated runway at a high mass with only 2200m of LDA seems like a bad idea. I don't have anything to run the numbers but it looks like a bad idea :) tech log : as I explained earlier, I am an aviation professional, only not a pilot. Since my job is in close relationship to flying, I'm eager to learn from airline pilots' experience. And maybe I'll even correct things at my job or suggest new things if it's concluded we've been writing incorrect things. When I said that the FCOM (or rather FCTM) states "any late flare will increase the likelihood of a hard landing" it was only to clarify things with someone here who said he was able to flare at a very low height while achieving perfectly smooth touchdowns. Since this is in disagreement with airbus doc, either one sentence is wrong or the two sentences don't talk about exactly the same thing, so definitely something to clarify. I'm not saying my sentence is right, I'm asking for a clarification. There are very few airbus pilots at airbus.. Most of the guys working airbus flight ops only have a PPL or no license at all, and these are the guys writing the FCTM/FCOM. |
Landing without reading FCOM? Passengers are not allowed in the cockpit. You better stick to whatever you are doing, |
Originally Posted by KayPam
(Post 9860785)
There are very few airbus pilots at airbus.. Most of the guys working airbus flight ops only have a PPL or no license at all, and these are the guys writing the FCTM/FCOM.
Just intrigued as to how it all works at AB? |
The flight ops manual is written.. by the flight ops department.
I've taken a few minutes to find public sources for this message : First, type "flight ops engineer airbus" and find this kind of job offers : https://www.wizbii.com/company/airbu...s-engineer-m-f This is an example of a job offer where it states that : - The flight ops department comprises both pilots ("expert pilots") and engineers - The guys who actually write the FCTM/FCOM can be interns With these key words you can type other things in google or directly linkedin : "flight operations engineer airbus", you'll see plenty of people. "expert pilot airbus" : much less people These expert pilots often are ex airline TRI/TRE But you can infer from what you've researched that there are few pilots and many engineers. Which is not surprising since it's a desk job and pilots will cost much more than engineers. (plus let's face it there are many parts of the flight ops documents that don't require any flying experience at all) Yes you would expect the landing/flare section to be carefully proofread by several qualified pilots. But it looks like people can go against it without major problems. We've even read claims here that directly contradict some sentences in the FCTM. So since (as someone said) I don't fly the bus myself I'm really not sure what's true or false. What I'm certain of is that we need some clarification on this topic. One reason why the FCOM could appear "incomplete" is because its a very political document. If it was worded in an inappropriate way, airlines having damaged an airplane upon landing could reproach airbus with their FCTM or FCOM wording, and ask them to pay for the repairs. The flight ops department, when they write these documents, don't think about writing the whole complete truth. Their goal is to keep airbus safe and they write things that way. They also want to minimize incidents, like hard landings (hard landings are definetely the number one type of incident that Airbus helps airlines with) So it's possible they'll recommend a flare height that's a bit overestimated, in order to help reduce hard landing numbers.. (longitudinal runway excursion numbers are much lower than hard landing numbers) For all these reasons I would like an answer from your experience as pilots : What's the lowest altitude you can start a flare and still make a proper landing ? (from stabilized conditions : -3°, no wind, no stick input before the start of flare, CAS stable at VAPP) |
What's the lowest altitude you can start a flare and still make a proper landing ? |
KayPam
Most of the guys working airbus flight ops only have a PPL or no license at all, and these are the guys writing the FCTM/FCOM. What's the lowest altitude you can start a flare and still make a proper landing ? Like how much seat of the pant talent you have. What is the environmental factors like wind, gust, Apt. elevation etc. But to get percentage result you should stick to standard format. If one has good judgement of the height and amount of flare you can land from any height. |
The saga continues.
It really surprises me that seemingly experienced pilots have not noted a difference in aircraft behavior depending on: -sharklets----float -2 knots on top of Vapp---float -tailwind---float It surprises me more that people focus on the rate of descent in a tailwind. With a 2 knot tailwind there is hardly any difference. But you WILL float if you do not adapt your technique. |
i think the point about flare heights in a tailwind is: it depends a lot on airport geography.
the FCOM is written with a relatively constant tailwind down to the ground in mind. this might not be the most occuring scenario but it is the most conservative approach as airbus would rather have a float than a hard landing as someone wrote. (how wise that is is another topic) now it as has been commented at most airports there is a tendency for the wind to reduce substantially in the lowest 100ft. if this is the case you gain airspeed at a low level and therefore can land with a later flare. now with all the examples we have had no one has cited an airport or actual tailwind numbers. no one has stated wind differences at low level their airports get. all this will surely influence flare height quite a bit. to give two different examples: - an airport somewhat surrounded by buildings or forest - an airport on an island where the runway is nearly surrounded by ocean that would make quite a difference regarding lower wind layers, wouldn't it? |
A bit of raw data to feed the debate.
FCTM for long range aircraft states : "if the flare is initiated too low (below 25ft), then the pitch changes will not have sufficient time to allow the necessary change to aircraft trajectory. Late, weak or relased flare inputs increase the risk of a hard landing" (I just checked it for one airline) FCTOM for single aisle aircraft has the same line only without the 25ft value (also checked it for just one airline) I've seen cases in which a full back stick input from 20ft down to the ground was not enough to avoid a hard landing (for SA aircraft). |
Kay,
Is it possible with your contacts to ask an experimental test pilot why this is so? |
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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