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A321 Neo: CAT C or Cat D?

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A321 Neo: CAT C or Cat D?

Old 12th Apr 2021, 07:30
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A321 Neo: CAT C or Cat D?

Hello everyone,

In our fleet with have A321 CEO some are category C (MLW 75.5T) and some are category D ( MLW 77.8T).
from what I undestand the aircraft category will depend of your Vs1G* 1.23 during approach at MLW.
Now we also have A321 NEO with a max landing weight of 79.2T. According to our FOM, they are considered Cat D aircraft. But a friend of mine in another airline, the A321 NEO is still a CAT C aircraft. As if you you do the landing performance even at MLW of 79.2T the A321 NEO will have a much lower VAPP than an A321 CEO at MLW of 75.5T in config full as by aircraft design the A321 NEO has more flaps extension in config full compare to other A321. In the other hand flaps 3 are exactly the same and therefore it’s not unusual to see a a 10-12 kt difference between VAPP in conf 3 versus conf full on A321 Neo while one the CEO it’s usually around 5/7kt only. VAPP conf 3 on 321 neo while heavy is above 151kt.

My questions are: The category of aircraft assumes config full only? As the A321 NEO is definitely a CAT C with flaps full but not in Flaps 3. I’m wondering if in your outfit you will apply cat D minima if you decide to fly Conf 3 in an heavy 321 as it’s definitely falls in the Cat D Aircraft.
I don’t undestand how come an airline can consider the A321 Neo cat C aircraft unless they always use flaps full landing.

Thank you.

Last edited by pineteam; 12th Apr 2021 at 07:46. Reason: Typo
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Old 12th Apr 2021, 12:43
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I believe the flap angles for the Neo were changed to get it back to a Cat C
Skybrary has this to say about approach categories
According to TERPS criteria, an aircraft shall normally fit into only one category. However, if it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the next higher category should be used. For example, an aircraft which falls in Category A, but is circling to land at a speed of 115 knots, should use the approach Category B minimums when circling to land.

Last edited by tubby linton; 12th Apr 2021 at 13:10.
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Old 12th Apr 2021, 16:02
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It seems that it is up to the manufacturer or operator to decide (cf 8168 below). From the Airbus side, it is considered as class C (cf Airbus Airport Planning Manual). The question was asked recently in one monthly quiz of A320Expert with reference to the documentation.

Pan OPS8168 Volume II

1.8.2 The criteria taken into consideration for the classification of aeroplanes by categories is the indicated airspeed at threshold (Vat) which is equal to the stall speed Vso multiplied by 1.3 or stall speed Vs1g multiplied by 1.23 in the landing configuration at the maximum certificated landing mass. If both Vso and Vs1g are available, the higher resulting Vat shall be used.

1.8.3 The landing configuration which is to be taken into consideration shall be defined by the operator or by the aeroplane manufacturer.

1.8.4 Aircraft categories will be referred to throughout this document by their letter designations as follows: Category A — less than 169 km/h (91 kt) indicated airspeed (IAS) Category B — 169 km/h (91 kt) or more but less than 224 km/h (121 kt) IAS Category C — 224 km/h (121 kt) or more but less than 261 km/h (141 kt) IAS Category D — 261 km/h (141 kt) or more but less than 307 km/h (166 kt) IAS Category E — 307 km/h (166 kt) or more but less than 391 km/h (211 kt) IAS Category H — see 1.8.8, “Helicopters”.

Last edited by Aerazur; 12th Apr 2021 at 20:03.
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Old 12th Apr 2021, 16:25
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PANS-OPS "C"
Vref: max 140
V final app: max 160
V circiling max 180

Vref A321-CEO_IAE 75.500 = 140 kt.

Hare's breath, but it fits on the paper if you want it to. The endgame is increased safety margins thanks to lower available minima. More straight-in-landings is safer than more go-arounds and diversions to alternates.

Someone tell me, what is the reasoning behind landing a 79 tonnes jet at 12 kts higher speeds than necessary, by using F3?
Ek(3) = 0,5 * 79.500 * 76 * 76 = 229,6 MJ
Ek(f) = 0,5 * 79 500 * 70 * 70 = 194,8 MJ
35 MJ extra for what exactly?

That is equivalent to 7,2 metric tonnes of extra weight. Practical terms, imagine:
One nice shiny 40' shipping container https://containertraders.com.au/wp-c...16/08/40HC.jpg
carrying three legendary Lada 4x4 Nivas https://i.pinimg.com/736x/c6/ab/4e/c...car-tuning.jpg
coming at you at 250 kph. And needing to stop that combo - or not, because it was never there. Hmmmm. And no, the FCOM does not advise using F3 in gusty conditions.


Back to the topic:
Does the quoted 151 Vapp on 321-NEO F3 fit within the CAT "C" speed range for final approach and itermedieate MisAPCH ? [YES]
Does the certifided Vref on 321-NEO at MLW fit within the CAT "C" speed range for V(at-threshold) [YES]
Did the manufacturer go significant lenghts to "keep" the NEO in CAT "C" [YES]
Does the word "keep" imply that previously similar efforts were made to assure the CEO also had been CAT "C" [YES]

Last edited by FlightDetent; 12th Apr 2021 at 17:25.
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Old 12th Apr 2021, 17:51
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Flightdetent, I did not really understand but about using flaps 3 on A321 is just so much nicer than flaps full. I think any pilots who flies that type will agree. Nothing like the A320 who flies horribly nose up in conf 3 the A321 sits nicely at 1.5/2 degrees up. I always land config 3 on A321 unless tailwind and short runways but oh well in China that’s almost non existent. xD

Back on the topic: Flaps 3 max landing weight on A321 Neo will be around 153kt vapp. Faster than the A321 CEO which are Cat D In config full. Thus one of my question. How can we consider the A321 Neo a cat C aircraft when it flies much faster than some A321 cat D aircraft.

Last edited by pineteam; 13th Apr 2021 at 02:40. Reason: typo
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Old 12th Apr 2021, 18:31
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Not really contributing to the topic, but I use full on the 321 to keep the workload low.
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Old 12th Apr 2021, 19:46
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Consider that an A321, or any modern Airbus for that matter, could easily be 10 kts faster over the threshold given a strong headwind (GS Mini). Are we therefore to say that whenever the approach speed is higher than normal that we ought to reconsider the approach category? I don't know the answer but somewhere in all of this will be an argument for keeping things consistent despite the occasional deviation. Flap3, though nice to perform given a long runway, is not considered by Airbus as "normal".
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Old 12th Apr 2021, 22:29
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Superpilot

That’s the FAA’s position.

AIM 5-4-7 (b)

https://www.faa.gov/air_traffic/publ...pubs/aim_html/
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Old 13th Apr 2021, 03:21
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Its easy to over think this stuff. As pointed out above the operator will nominate the approach category based on approach speed in landing configuration. The operator will likely consider the lower approach speed when two landing configurations are available.

This wont limit the crew to conf full ( for the Airbus example ). As crew we should be familiar with the speed ranges for each segment of the approach and comply with them. This will ensure obstacle clearance based on the procedure design. So using Conf 3 for A321 would be possible as CAT C so long as the Initial / Final / Circling speeds are flown correctly. (For PANS OPS Procedures anyway as TERPS procedures dont have the same speed requirements ).
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Old 13th Apr 2021, 03:23
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Superpilot and Check Airman, I'm a bit surprised by your comments. By our FCTM for the A321:'' When landing performance permits, the best combination to reduce fuel costs and brake oxidation is: Conf 3 + REV IDLE + Autobrake LO''.
I don't understand the higher workload. I'm talking about operating on runways ranging from 3300 to 4000 meters on average at sea level. Unless very heavy you seldom need to override the autobrake if ON to brake more. I usually disconnect it earlier to keep the aircraft rolling to exit on the last high speed taxiway.
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Old 13th Apr 2021, 03:58
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Thanks. However, I think the reference might have changed. Could not find it in the latest publication. I found a nice explanation at AOPA although they don't mention flap setting taking your aircraft into the next category. https://www.aopa.org/news-and-media/...ary/29/ifr-fix
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Old 13th Apr 2021, 06:04
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Pinteam: structured reply to your reaction with some answers for the original dilemma later.

For now, consider
F1 at 12 NM
F2 at 8 NM
L/G DN at 4.3 NM
F4 at 3,5 NM

No ABRK, IDLE rev.

Does the SOP profile at your company with FCTM save more fuel? Is it more easy on the brakes?

For airlines whose homebase is 2400 m, is it a smart choice to have pilots fiddle with the flap selection all the time or just unnecessary workload?

I am not calling right or wrong, just pointing out that people no less smart than the two of us combined may have valid reasons to achieve the same or even better results via different paths. And we should not be surprised when that is the case.

Having their application of rules and logic explained in depth often leads to an important discovery about how thorough and truthful I was when doing own homework.
===
This will be the core of introducing the answer for C<D you had:
A321 CEO is designed and certified with speeds for a category C aeroplane.
A321 NEO is designed and certified to fly slower or not faster (with the higher weight), so that it can remain C too.

Having 321 CEO as D is an unfortunate result of overthinkig some details, on NAA level admittedly some times.
Flying 321 NEO faster by pilot's choice so much that you push out of the C speed ranges for which it was carefully built
- is a false argument for "should be D"
- might be considered suboptimal decision (underpinning the fact it is impossible to design, certify and categorise within some limits and guarantee someone will not wilfully operate outside of them).

My observation is you need to first ask: What happened that CEO turned out as D for some?

Last edited by FlightDetent; 13th Apr 2021 at 06:43.
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Old 13th Apr 2021, 06:46
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Originally Posted by FlightDetent View Post
Pinteam: structured reply to your reaction with some answers for the original dilemma later.

For now, consider
F1 at 12 NM
F2 at 8 NM
L/G DN at 4.3 NM
F4 at 3,5 NM

No ABRK, IDLE rev.

Does the SOP profile at your company with FCTM save more fuel? Is it more easy on the brakes?

The profile you describe is definitely more efficient.
I wish I could fly as you described above but our SOP states that “ we should be fully configured at 1500 feet” so basically at 5 miles from TDZ and must be stabilized at latest by 1000 feet.
with this kind of conservative approaches I’m sure you will understand why I’m using flaps 3. Fuel or brake saving asides, I also think it’s easier to land in flaps 3 on A321. = )
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Old 13th Apr 2021, 07:50
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As I understand there are two issues in the question:
  • the category as defined by certification (max wt, config) - the speeds flown as recommended by the manufacturer.
  • the category to be considered in operation with respect to safety margins required by PANSOPS or TERPS (n.b. not always the same); e.g. where config / speed is changed for operational reasons, then use the category according to the revised values.

The first aspect is generally considered as an economic issue.
The second, much more important - safety margins in operation.
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Old 13th Apr 2021, 10:13
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Originally Posted by pineteam View Post
I don't understand the higher workload. I'm talking about operating on runways ranging from 3300 to 4000 meters on average at sea level. Unless very heavy you seldom need to override the autobrake if ON to brake more. I usually disconnect it earlier to keep the aircraft rolling to exit on the last high speed taxiway.
Well the workload is higher because for a flap 3 landing, you have to make the selection in the fms, and also on the gpws panel. I get tired just thinking about it.
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Old 13th Apr 2021, 11:10
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Haha! =)

PEI_3721, FlightDetent and Superpilot. Thanks for the infos.
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Old 13th Apr 2021, 11:26
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Originally Posted by Superpilot View Post
Flap3, though nice to perform given a long runway, is not considered by Airbus as "normal".
I disagree with the above. Airbus allows Flap 3 or Flap FULL in “normal” operations.

performance landing stipulates that with selection for normal landing, without failure, the flap lever selection is at the discretion of the operating crew.
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Old 13th Apr 2021, 12:26
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Yeah I was struggling to think of a term. Not "normal" isn't the way to describe it.
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Old 13th Apr 2021, 13:07
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Someone tell me, what is the reasoning behind landing a 79 tonnes jet at 12 kts higher speeds than necessary, by using F3?
Was always flap 3 for me on an A321 if performance permitted. Handling characteristics are great, and 160-to-4 is much easier if you only have to lose 5-10kt.

Also helped that you could vacate at a high speed exit further down the runway so you had a shorter taxi.

I was told that the trade-off between brake wear and fuel use is pretty thin. But since they're not my brakes it didn't bother me.
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Old 14th Apr 2021, 03:55
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"Well the workload is higher because for a flap 3 landing, you have to make the selection in the fms, and also on the gpws panel. I get tired just thinking about it."

"For airlines whose homebase is 2400 m, is it a smart choice to have pilots fiddle with the flap selection all the time or just unnecessary workload?"

It always fascinates me that individuals who self-identify as not having the spare capacity to perform tasks that others consider normal then poo-poo other pilot's choices using such emotive language.

Flap 3 or Flap Full is perfectly normal and has an equivalent in the 737 - Flap 30 or Flap 40. Not having the confidence in your own ability to utilise various aspects of the aircraft shouldn't mean that you reject the use of that aspect for others.

A similar example; if the crosswind limit for the aircraft is 38 knots and you don't personally feel comfortable or capable of landing safely at 38 knots across; should no pilot attempt 38 knot crosswinds? Does that make landing in a crosswind of 38 knots unsafe? Because of how one feels individually? I think not.
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