Need help with manual landing A320

[darth_damian_000 17]

Flying an A320, from LYBE to LSZH, landing on RWY 28.

 

When I am about to land, I disconnect autopilot at around 800-1000 feet above the ground. From then, I use my glideslope and centerline indicators ('diamonds') to guide me onto the runway.

1) How important are those adjustments? If the diamond goes slightly off center, should I worry about it? I look at the PAPIs, and I've made decent landings with 3 white 1 red, for example.

At around 20 feet, I get the "retard" callout.

2) How much should I pull back on the joystick? I pull back 40% maybe, and the plane doesn't touch down, it's as if it is flying level with its nose up. What am I doing wrong here? If I am more patient, will I eventually touch down?

 

Thank you all.

 

 

[Speaker 1]

1) If you can see the PAP's, it's bether to use the PAPI's.

2) If you get the Retard, you have to pull back to "Neutral".

[Lotus3xiG3 118]

I'm doing the same like you two, but at 20 ft I put the thrust to idle and pull back the stick very soft! And then at the 5 ft callout more, so that the rear gear touches first and then the frontgear.

[skelsey 103]

The glidepath indicators (both ILS and PAPI/VASI) are important: they show you the angle of your approach, which is important for obstacle clearance. You can arrive at the same spot on the runway if you are well below the glidepath, but your trajectory on the approach will be very flat (and you might bump in to something). Conversely, you could approach at a much steeper angle, but then your rate of descent would be very high:

Please login to display this image.

 

Same impact point -- different paths to get there.

 

Having said that, the really important thing to remember with any sort of visual glidepath indicator (i.e. VASI/PAPI lights) is that they will take your eyes to a particular height above the threshold. Clearly, this means that if the wheels are to cross the threshold at 50ft, the pilot's eyes must be higher in a large/long jet with a high flight deck compared to a smaller aircraft. Therefore, PAPIs/VASIs are normally calibrated to the most common aircraft type using the airfield: following 2 whites/2 reds in a B747 at an airfield with PAPIs calibrated for C172s will result in the aircraft touching down short of the runway, whereas following 2 whites/2 reds in a C172 at a large international airfield calibrated for B747s will result in crossing the threshold at some 70-80ft and a much longer landing. Those are the extremes: obviously everything else is somewhere in between, but it's an important point to remember. In a B747, it is common to fly 3w/1r at most airfields to obtain the correct threshold crossing height.

 

The eye-to-wheel path height on the A320 is about 25ft (i.e. the pilot's eyes will follow a trajectory 25ft above that of the main landing gear wheels whilst on a 3 degree glidepath at a normal approach attitude). The minimum height the wheels may cross the threshold for the A320 is 20ft. Therefore it is worth checking the MEHT (Minimum Eye Height Above Threshold) for the PAPI to see whether it is greater or less than 45ft: if it is less then you must not follow the PAPI below 200ft. Unfortunately the MEHT is not easily accessible to pilots: they are only included in national AIP data and not usually on approach charts. However, that said, at most places you're likely to fly an A320 in to the MEHT will be sufficient: if you are going to fly to somewhere normally frequented by much smaller aircraft you may want to do some digging and checking. By comparison, the B747 eye-to-wheel height is about 45ft -- it is clear to see that following a PAPI set for an A320 with an MEHT of 45ft in a B747 would result in the main landing gear impacting the runway on or short of the threshold with 2w/2r!

 

In terms of guidance on final -- I would tend to use the ILS, then gradually transition to visual references (i.e. the 1000ft markers/PAPIs etc) as you get lower. The PAPIs are a good reference but I would focus more on the marked aiming point on the runway and keeping that fixed in position with the correct glidepath angle (note that the ILS glidepath will guide the glideslope antenna on the aircraft to a point above the threshold and, again, this will have been calibrated for a particular threshold crossing height).

 

As you descend through 200ft or so you may get the sense that the ground is rushing up to meet you and this is where (combined with ground effect) you may tend to "shy away" from the landing, reduce your rate of descent and start getting high: keep the aircraft coming down on the correct glidepath. Good landings come from stabilised approaches: if you are stable, in the correct configuration at the correct rate of descent, with approach power set and at the correct attitude when you cross the threshold you have a good foundation from which to complete the flare!

The other common error is to "duck under" the glidepath in the latter stages of the approach to flatten out the final stages of the flare and landing: this too is poor technique (think obstacles!) and should be avoided.

 

As you get nearer to the ground, use the radio altimeter callouts to help you. At the "FIFTY" call you should be over the threshold: if the threshold is still in sight at this point, you are low. If the threshold has already disappeared by the "ONE HUNDRED" call you are high!

 

From that point in, use the cadence of the callouts to help judge your rate of descent and flare. You should hear something like "FIFTY... FORTY... THIRTY... TWENTY... TEN................ (touchdown)". If you hear "FIFTYFORTYTHIRTYTWENTYTEN" you have probably buried it!

 

As you cross the threshold - shift your focus to the last third of the runway. Passing through 50R the Airbus will go in to Flare Mode: it memorises the pitch attitude as you pass through 50ft and that attitude becomes the initial reference for pitch control. Thus it is very important on the Airbus that you cross the threshold in a stabilised manner at the correct airspeed and attitude!

 

Descending through 30ft the FBW system will start to reduce the pitch attitude at a rate of 2 degrees down in 8 seconds. This is simply to make the flare feel more conventional, i.e. to require a backwards pressure on the sidestick.

 

Start the flare itself at around 20-30ft. Ease the stick back and gently raise the nose approximately 2 to 4 degrees. How much is 2-4 degrees? Just barely enough to be perceptible. This attitude change is judged visually, not by looking at the ADI: this is why you must look out at the last third of the runway in the flare, because otherwise you will not be able to judge your rate of descent and pitch change. Close the thrust levers smoothly and hold the pitch attitude: do not attempt to hold the aircraft off for a "greaser".

 

Remember that "RETARD" is a reminder, not an order: however, with the A/THR engaged in a manual landing if you do not retard the thrust levers to idle the system will add thrust to keep the the aircraft on target speed, which will result in you continuing to fly gently a couple of feet above the runway! In an autoland the system will automatically reduce the thrust to idle (and this is where "RETARD" is an instruction).

 

What you must remember is that the landing is a dynamic manoeuvre and you will need to take in to account the conditions on the day and judge the correct point to start the flare/remove the power -- consider gusty winds etc.

 

Don't forget to keep flying the aeroplane, both in the flare and after touchdown: deployment of spoilers/reverse thrust will result in a nose-down pitching moment (at least on the Aerosoft bus) which you must be ready to arrest and gently fly the nosewheel down on to the runway with a slight aft pressure on the stick.

 

Hope that is helpful.

[adl320 1]

Great insight and detailed response, Simon. Often times in the real world, you are vectored to a final approach and may at times be told to "Track localizer inbound". Essentially, that will help you maintain lateral guidance in hazy conditions. That is effectively flying on instruments. When you are either cleared for, or are flying a visual approach, you can certainly use the Glideslope/localizer for guidance, but as Simon mentioned, the VASI or PAPI is your visual reference at that point. Both the VASI/PAPI and the ILS localizer beam is typically aligned to a 3 degree approach path but may be different to account for terrain, obstructions, etc.

 

A lot of landing also involves visual cues such as where the touchdown point is in your field of view out the window. The first third of runway is marked by the solid white aiming markers about 1,000' from the landing threshold. If those marks rise up the window, you will land short of the mark. If the marks go lower in the window, you will land long. These marks are your "desired" landing point on most runways but it isn't often that the flights I've flown on land on those marks. The objective for most commercial pilots with the luxury of long runways is a smooth landing, often resulting in long floats down the runway to smooth the landing.

 

I've attached some Airbus documents from a great online site which you will see in the docs. They outline the procedures for visual and ILS approaches in the A320. Practice doing "touch & Goes" with the A320 using the visual procedure and your landings will improve for sure!

 

Aaron

 

COPYRIGHT PROTECTED MATERIAL DELETED!

Please post links instead.

 

 

 

[Tom A320 4915]

Hi Aaron,

 

please post links to the files instead of posting them directly into the AS forum. Thank you.

[adl320 1]

Understood, thanks. Any consideration for sharing links? I have found a great reference related to the OPs question and Simon's response.

 

[Tom A320 4915]

Every link to another page that holds downloads or pictures is totally fine. Just uploading them here into the forum violates copyrights and can't be permitted by Aerosoft.

[skelsey 103]

Hi Aaron,

 

Thank you! Glad you enjoyed the post. Just a small point that's worth emphasising...

 

1 hour ago, adl320 said:

These marks are your "desired" landing point on most runways but it isn't often that the flights I've flown on land on those marks. The objective for most commercial pilots with the luxury of long runways is a smooth landing, often resulting in long floats down the runway to smooth the landing.

 

The aiming point markers are exactly that - an aiming point, and (assuming you keep them fixed in the windscreen) they represent the point at which you will impact the runway with no flare (strictly speaking the wheels will impact slightly before due to the eye/wheel path difference discussed earlier, but you get the idea).

 

Of course, if you don't flare at all then the pax will spill their G&Ts. The flare obviously extends the glide slightly and the result is that you will usually touch down slightly beyond the 1000ft markers, but it is imperative that you are down inside the marked touchdown zone (which will extend some way beyond). Runway overruns are a big industry topic, and as a result often there will be a SESMA event associated with long landings and/or excessive float -- i.e. if you continue to land having floated excessively and/or beyond the TDZ the aeroplane will send a message to your chief pilot and you can expect a tea/no biscuits chat, long runway or otherwise...

 

Smooth landings are great, but the primary objective must be to put the aeroplane on the ground at the right speed, on the centreline, in the touchdown zone and at a comfortable rate of descent -- everything else is a bonus.

[adl320 1]

Totally agree, Simon. I found this link which gets into the technical bits regarding all this. Although it is based off a G450, it is something that can be translated to other aircraft in principle. I've checked with the moderator and this link is OK to share

 

http://code7700.com/aim_point_vs_touchdown_point.html

 

Thanks,

Aaron