Landing Distances - EASA CAT.POL.A.230

[Journey Man]

I've read all the previous threads on PPRuNe and elsewhere regarding landing distance performance and Performance A factors; yet even the most in depth thread I found on this site is still very subjective as to whether CAT.POL.A.230 f) applies when carrying out an inflight, pre-landing assessment of the destination airfield with the latest weather.

For this question I am referring to commercial operations on a Performance A aircraft. The situation I am referring to is pre-landing performance assessment of the planned destination, under normal circumstances, using the actual conditions. Abnormal, Emergency, or other "RE-planning" diversions are not considered.

Here's the section from IR-OPS Annex IV:
CAT.POL.A.230 Landing — dry runways
a) The landing mass of the aeroplane determined in accordance with CAT.POL.A.105(a) for the estimated time of landing at the destination aerodrome and at any alternate aerodrome shall allow a full stop landing from 50 ft above the threshold:
1) for turbo-jet powered aeroplanes, within 60 % of the landing distance available (LDA); and
2) for turbo-propeller powered aeroplanes, within 70 % of the LDA.

b) For steep approach operations, the operator shall use the landing distance data factored in accordance with (a), based on a screen height of less than 60 ft, but not less than 35 ft, and shall comply with CAT.POL.A.245.

c) For short landing operations, the operator shall use the landing distance data factored in accordance with (a) and shall comply with CAT.POL.A.250.

d) When determining the landing mass, the operator shall take the following into account:
1) the altitude at the aerodrome;
2) not more than 50% of the headwind component or not less than 150 % of the tailwind component; and

3) the runway slope in the direction of landing if greater than ± 2 %.
e) For dispatching the aeroplane it shall be assumed that:
1) the aeroplane will land on the most favourable runway, in still air; and
2) the aeroplane will land on the runway most likely to be assigned, considering the probable wind speed and direction, the ground handling characteristics of the aeroplane and other conditions such as landing aids and terrain.

f) If the operator is unable to comply with (e)(1) for a destination aerodrome having a single runway where a landing depends upon a specified wind component, the aeroplane may be dispatched if two alternate aerodromes are designated that permit full compliance with (a) to (e). Before commencing an approach to land at the destination aerodrome, the commander shall check that a landing can be made in full compliance with (a) to (d) and CAT.POL.A.225.

g) If the operator is unable to comply with (e)(2) for the destination aerodrome, the aeroplane shall be only dispatched if an alternate aerodrome is designated that allows full compliance with (a) to (e).


CAT.POL.A.235 Landing — wet and contaminated runways
a) When the appropriate weather reports and/or forecasts indicate that the runway at the estimated time of arrival may be wet, the LDA shall be at least 115 % of the required landing distance, determined in accordance with CAT.POL.A.230.

As I have understood all the threads I've found on this subject, some believe the requirements of a) - d) do not need to be applied once enroute to your planned destination and only the relevant AFM landing performance is applicable. I interpret the above regulation to mean that we are required to ensure our landing performance calculation complies with these Performance A factors. I could be entirely wrong.

Our AFM landing performance figures, and our performance calculations created via our briefing software, allow me to calculate operational dispatch planning via a supplement and then AFM landing performance, which is factored as per CAT.POL.A.230 a) 1) and CAT.POL.A.235 a). For my aircraft, the operational dispatch planning figure seem reasonable and the AFM Supplement it is derived from does state it complies with the EASA requirements to land within 60% of the LDA and we can further factor the landing distances for wet runways. (i.e. it complies with CAT.POL.A.230 a) 1) and CAT.POL.A.235 a)) The supplement specifically states that it is a requirement to calculate the landing performance prior to approach, and to use the main AFM landing performance section and the prevailing weather at the destination airfield to calculate this actual landing performance. Using the applicable Performance A factors with the main AFM landing performance figures results in severely restricted landing performance, in particular for wet runways.

The aircraft manufacturer has been very helpful responding to my enquiries seeking clarification. They have advised that the requirement to factor the landing distance to land with 60% of the LDA is not applicable once enroute. (They don't mention CAT.POL.A.230 a) 1) specifically.) In practice, we currently apply these factors via the FMS and crosscheck the FMS performance against our briefing performance with CAT.POL.A.230 a) 1) factor (x1.67), or the CAT.POL.A.235 a) factor (x1.92), applied.

Operational Dispatch Planning does state compliance with these two factors. AFM landing performance section does not state any factor, although clearly one is already applied otherwise there would not be such a large reduction in landing performance when comparing the operational dispatch planning to the AFM landing performance with either the 1.67 or 1.92 factors applied. AFM landing performance without these factors applies is significantly less restrictive than operational dispatch planning figures. It is not stated by what factor the landing performance calculated directly from the AFM is factored by. I presume it has some factor to avoid the risk of runway overrun excursions. Assuming CAT.POL.A.230 a) 1) is applicable, we are therefore unable to show the standard AFM landing performance complies with this.

I know this subject is raised a few times a year, but I haven't seen a decisive consensus in any of the threads I've read regarding the application of CAT.POL.A.230 a) 1) and CAT.POL.A.235 a) during inflight assessment of the planned landing. I intended to set this up as a simple "they apply" or "they don't apply" poll but haven't figured out how to do it here on PPRuNe. I've been pouring over IR-OPS, AFM Sections, AFM Supplements and back and forth with the manufacturer and I'm afraid I'm struggling to see the wood for the trees… Your collective advice is much appreciated! :ok:

[BizJetJock]

The first sentence refers you to CAT.POL.105, which says that all these requirements apply at the start of the takeoff run. Therefore once you are airborne only the actual landing distances need to be considered.
As with all these things, what is legal may not be sensible!

[Journey Man]

Whilst I agree that CAT.POL.A.105 a) 1) does state "at the start of the take-off; or" I'm unconvinced that this caveat is an exemption from further performance restrictions as CAT.POL.A.105 a) 1) is a general regulation and it could equally be argued that CAT.POL.A.100 a) is applicable as it states, "The aeroplane shall be operated in accordance with the applicable performance class requirements." One of which is CAT.POL.A.230 f) stating "Before commencing an approach to land at the destination aerodrome, the commander shall check that a landing can be made in full compliance with (a) to (d) and CAT.POL.A.225."

The part that does interest me from CAT.POL.A.105 is

CAT.POL.A.105 b)
(b) The approved performance data contained in the AFM shall be used to determine compliance with the requirements of the appropriate chapter, supplemented as necessary with other data as prescribed in the relevant chapter. The operator shall specify other data in the operations manual. When applying the factors prescribed in the appropriate chapter, account may be taken of any operational factors already incorporated in the AFM performance data to avoid double application of factors.

So maybe this does support what you're saying i.e. that the regulations are mindful of double application of factors and hence the AFM is sufficient.

So far:
No factor: 1
Factor: 0

[FlightDetent]

Hi,

The way I read it:

If you cannot meet the requirements of (e1), you may still dispatch with two alternates and then, before comitting to original destination, the dispatch conditions needs to be satisfied even when airborne.

It seems to make a lot of sense. If you cannot meet the dispatch criteria before flight, you are still allowed to depart, provided the dispatch criteria will be satisfied before commencing the approach.

[Skyjob]

Simply put:

BEFORE departure, despatch landing performance (planning performance) is to be taken into account, to ensure the flight can be completed to its destination, OR if unable two alternates (eg a new destination plus diversion to an alternate) must be valid before dispatch with associated fuel requirements.

AFTER departure, enroute landing performance (inflight actual performance data) is taken into account, to ensure the flight can be landed at intended destination.

Intended destination in the latter paragraph may well be the original destination if actual conditions are better than forecast conditions which prohibited its planning use to be suitable.

For instance:
Due WIP in GDN a reduced runway length exists and forecast weather conditions are SN with runway state reported at planning stage to be braking action medium.
The above reduces you planned maximum landing weight to conditions which prevail and the safety margins built in to them, thus well reducing your payload capability.
Operational experience has shown the runway will most likely be treated by the time you arrive, but no guarantees, thus you cannot assume this and dispatch performance is thus defining a payload reduction.
Your flight will now need to be using a second alternate with no restrictions for planning performance calculations, so all payload booked can be taken.
Once departed and approaching destination, the crew can access actual conditions in GDN and establish if Inflight Performance is suitable to make an approach at the scheduled destination, win for all parties involved, passengers at destination, aircraft in place for return trip, no diversion requirement.

[Journey Man]

FlightDetent, I agree with the requirement for two alternates in the case of (e) (1). If the requirements for (e) (1) were met before departure, what's your interpretation on the 60% requirement?


Just to throw in an argument against the use of CAT.POL.A.105 (a)(1) to act as a caveat to exempt the airborne, enroute situation… CAT.POL.A.105 (a) (1) is a General Requirement, and there is CAT.POL.A.100 which states

CAT.POL.A.100
(a) The aeroplane shall be operated in accordance with the applicable performance class requirements.

So I understand this to mean that CAT.POL.A.105 is secondary to the Performance Class Requirements stated in CAT.POL.A.230 (f). I've sought clarification from the regulator regarding this query and am awaiting their response.

[Skyjob]

Journey Man, dispatch performance has the 60% safety built in, which is a planning factor. Do not confuse inflight/en-route planning with dispatch planning requirements.

Once dispatched, the planning has been completed preflight, thus does not apply further, and inflight performance takes over which is more detailed and generally more forgiving, with its own factors applied, thus the 60% need not be applied any more.

[dirk85]

I spoke about this matter with many colleagues, and still was not able to find an agreed solution.
Our flight operation manager tends to apply the more restrictive interpretation, using the planning minima even after lift off, at least when it comes to destination airports.

Let's make an example, which actually occurred to me recently.
Destination was Cannes, and in order to comply with the planning minima a headwind of at least 10 knots was required in order to land rwy 17.
The wind required was present in the forecast, and two alternates were selected. All the dispatch requirements were met.
During the descent to destination we checked the wind, which had decreased, falling below the minimum component necessary for us in the planning phase.

What were we supposed to do? It is actual phase now, and WITHOUT the 60% factorization we are able to take any runway, but WITH the factorization we shouldn't be landing.

[c100driver]

TALPA ARC

Advisory and Rulemaking Committees ? Takeoff and Landing Performance Assessment (TALPA) ARC, Charter (http://www.faa.gov/regulations_policies/rulemaking/committees/documents/index.cfm/document/information?documentID=302)

IFALPA


http://www.ifalpa.org/downloads/Level1/Briefing%20Leaflets/Aircraft%20Design%20&%20Operation/12ADOBL03%20-%20Certified%20vs%20advisory%20data%20on%20Boeing%20aircraft .pdf

[Skyjob]

Dirk85, in your scenario you have been despatched legally, you are now indeed requiring inflight planning from that point onwards.

Generally inflight planning is more forgiving as it is not factored by 60%, but it IS taking the more actual conditions into account (not so at planning stage hence the factor is applied). Thus you do not need the 60% required at planning anymore, you are to apply inflight performance and thus can land in your scenario on any runway where inflight performance enables you to land on.

[dirk85]

Skyjob, what about the paragraph that states... Before commencing an approach to land at the destination aerodrome, the commander shall check that a landing can be made in full compliance with (a) to (d) and CAT.POL.A.225.


Point (a) clearly refers to the 60% factorization, clearly introducing in the inflight re-planning phase all the rules typical of the dispatch phase.

[Skyjob]

See the GM1 for CAT.POL.A.230, clear indicating the reference to planning by using words such as determining, planned and expected.

GM1 CAT.POL.A.230 Landing — dry runways
LANDING MASS
CAT.POL.A.230 establishes two considerations in determining the maximum permissible landing mass at the destination and alternate aerodromes:
(a) Firstly, the aeroplane mass will be such that on arrival the aeroplane can be landed within 60 % or 70 % (as applicable) of the landing distance available (LDA) on the most favourable (normally the longest) runway in still air. Regardless of the wind conditions, the maximum landing mass for an aerodrome/aeroplane configuration at a particular aerodrome cannot be exceeded.
(b) Secondly, consideration should be given to anticipated conditions and circumstances. The expected wind, or ATC and noise abatement procedures, may indicate the use of a different runway. These factors may result in a lower landing mass than that permitted under (a), in which case dispatch should be based on this lesser mass.
(c) The expected wind referred to in (b) is the wind expected to exist at the time of arrival.

Actual conditions are used inflight, not planned ones...

[dirk85]

I would totally agree with you, and I think that planning phase should be separated from actual phase, but you did not answer the question.

That paragraph that I quoted you clearly talks about factorization, making reference to full compliance with CAT.POL.A.230 from point (a) to (d), which includes the 60% factor, and before commencing the approach, which indicates without a doubt an in-flight situation.

To be noted that this seems to apply only when a particular wind component is necessary in order to meet the above requirements (i.e. you comply with (e)(2) but not (e)(1)), and is coherent with the example of Cannes I made before.

Different would be if the plane does not meet point (e)(2) in planning phase, but comply with (e)(1): in that case once in-flight you are not required to meet any dispatch minima and you can use the unfactorized values from the AFM.

[JonDyer]

This is fascinating stuff. I've read earlier threads on this subject and must admit I'd always assumed there was nothing in it.

I think the question here though is: what evidence is there that the interpretation made by dirk85's Ops Manager is wrong?

I spoke about this matter with many colleagues, and still was not able to find an agreed solution.
Our flight operation manager tends to apply the more restrictive interpretation, using the planning minima even after lift off, at least when it comes to destination airports.


It's not clear to me where the distinction between pre-dispatch planning and inflight planning comes from?

Why does anyone think operators don't need to use the factored totals after dispatch?

[safetypee]

This issue is a grey area in regulation (deliberately?) and is open to interpretation.
The operator (Captain) is responsible for safe operation, there is a reminder of this in the OPS section – before landing assessment. There may also be other assumptions in the regulations (including CS25), but the final judgement is that of the Captain before landing.
Providing you can justify the choice of action as being safe then all is well, but if the chosen data is less than the established safety margin based on the dispatch data, then with hindsight after an incident, the decision could be debatable. The debate would be about the equivalent level of safety, and thus that there should not be a gap between dispatch and pre landing.

Many manufactures provide ‘actual’ data which requires considerable knowledge of what the data implies and then requires assessments, additions, or adjustment in correctly recognising contributing factors. If assessed correctly, and appropriate safety margins are added, then the pre landing check using ‘actual’ distances should be close to the dispatch case.

Airbus, for one, now publishes Operational Landing Distances (OLD), more often with a Factor (FOLD) – check what the factor is - which provide more realistic and achievable landing distance for the conditions. There are still provisions such as the reported runway conditions are reasonably accurate (Captain decision again).
In many situations (most?), FOLD should closely agree with the dispatch data, thus the pre landing FOLD data could be deemed ‘safe’.
But then the crew still has to fly the aircraft according to the assumptions in the data.

[Journey Man]

Dirk85 has raised a great example.

CAT.POL.A.230 (f) is clearly relevant in this case. Putting everything into plain English: if there is only one runway, and you need a specific headwind component to land on it because in still winds your ODP performance shows it to be too short, you have to ensure that your landing performance allows you to comply with the requirements of CAT.POL.A.230 Landing (a) - (d) before commencing the approach.

Why only this one case? If you're airborne, and in every other case we can supposedly disregard the requirements of (a) - (d), what is the benefit of applying those requirements in this one case? Why would the requirements of (a) - (d) apply to only that one, specific situation?

My understanding remains that Performance Class requirements takes precedence over CAT.POL.A.105 (a)(1), and the requirements of CAT.POL.A.230 Landing (a) - (d) are applicable. In the case outlined in (f) I believe that this is merely reinforcing the requirements as in that specific situation a given wind component is required in order to ensure the necessary commercial safety factors; and these factors, most pertinently the 50% HW component, are applicable.

I've not seen a convincing argument against how I've comprehended this part of IR-OPS, but I'll add the caveat that I have made being wrong into an art form... :}

[FlightDetent]

Hello again everyone,

I read your posts carefully, yet still I see no trouble, please help me understand where the percieved dilemma comes from.

Typically (think of alternate aerodrome planning minima..), there are dispatch conditions, which are more restrictive than what is in fact operationally required to land. Then:

You can land safely if ALD (actual landing distance) is less than LDA - in flight calculation requirement. To put some margin in, the regulations require us to use ALD*1,6 coefficient in the dispatch phase. Thus: a) on purpose we dramatically reduce the statistical probability of really needing to land at ALD=LDA; b) if WX/MX/ conditions change unpredictably whilst airborne, the pilots are still allowed to use the full certified capabilities of the A/C without the 1,6 margin restraining them.

The NORMAL situation
1) big margins needs to be applied to dispatch
2) once in flight, as long as ALD < LDA, you may land "WHATEVER".
(statistical approach to hazards and risks)

I understand (f1) correctly, it provides - for a specific set of conditions - a waiver to the principle above:
If the operator is unable to comply with (e)(1) for a destination aerodrome having a single runway where a landing depends upon a specified wind component, the aeroplane may be dispatchedSo the ALTERNATIVE situation
1) the big margins normally in force (dispatch requirements) can be circumnavigated :O (2 alternates et al.)
2) but only if you promise to adhere to them before starting the approach. Which is not normally the case required.

To summarize:
A) The regulators ask us to use a hazard filter (ALD*1,6 at dispatch), and then allow us to operate all the way to the limits (in-flight: ALD <= LDA) if the situation requires so.

B) The regulators via (f1) allow us to depart with special provisions (two alternates) without the 1,6 "hazard filter" applied yet, but we still need to show compliance before commecing to land.

[c100driver]

It is not grey but it is not obvious, the rule needs to be correctly interpreted and note that the CAT.POL.A.230 directs that the landing mass refers to CAT.POL.A.105A, is at the start of the takeoff or an inflight re-plan. That is it is a planning function.

CAT.POL.A.230 Landing — dry runways
a) The landing mass of the aeroplane determined in accordance with CAT.POL.A.105(a) for the estimated time of landing at the destination aerodrome and at any alternate aerodrome shall allow a full stop landing from 50 ft above the threshold:
1) for turbo-jet powered aeroplanes, within 60 % of the landing distance available (LDA);

CAT.POL.A.105 General
(a) The mass of the aeroplane:
(1) at the start of the take-off; or
(2) in the event of in-flight replanning, at the point from which the revised operational flight plan applies, etc

[john_tullamarine]

This one crops up regularly and one can only have empathy with those endeavouring to find black and white answers floating somewhere in the grey porridge.

Consider -

(a) the Certification Standards (ie what the AFM says) have stood a reasonable test of time under fire so, as a first approximation, they represent a reasonably good risk approach for the general case.

(b) in an emergency situation of one kind or another - which impacts on landing performance - the normal standards may, or may not, be feasible and the commander has to come up with a recovery plan for the situation. He/she is expected to use all available resources and information in determining what the gameplan is to be ..

(c) if the result at the end of the day is less than desirable the operator and crew (commander in particular) can expect censure of some sort according to jurisdiction

(d) all the relevant players, presuming survival for the crew, can expect to be quizzed aggressively as to their decisions and actions .. food for thought ?

(e) if you don't have a really good story .. you may find yourself in a state of unpleasantness. The Sydney collision mishap (https://www.atsb.gov.au/media/24753/197101202.pdf)in the early 70s, while not directly relevant to the landing problem, illustrates the detailed Monday morning quarterbacking to which the parties may be subject and strikes me as a salutary lesson in after-the-event activities. Although the memory is fading on the specifics of this one, my recollection is that the subsequent damages action resulted in an approximate three-way damages split for the relevant parties .. which included the B727 commander.

(f) what to do ? - my suggestion, regardless of rules and however you may choose to interpret the State protocols, is

(i) if you CAN recover in compliance with the Standards, why would you place yourself and your passengers at jeopardy by accepting a more critical requirement ? After the subsequent mishap (which may not be related directly to the decision) what will be your story in Court ? You can bet your superannuation and house on opposing counsel's endeavouring to assign much importance to that decision ..

(ii) if no compliant recovery solution be available, one needs to have done (within the time constraints on the day) relevant and defensible risk assessments to arrive at the apparently best solution. Again, expect to be quizzed mercilessly if things don't go according to plan.

(iii) if there is no sensibly desirable strategy available the folk on the spot just have to do their best .. sometimes the outcome appears to be miraculous (eg Sioux City and the Hudson River) while, with others, the crew is largely taken out of the loop (eg O'Hare and various midair collisions).

In all cases there will be all the time in the world for the subsequent witch hunt to explore the minutiae of the history.

That the commander may only have had seconds just reflects the basic unfairness of life at times ..

once in flight, as long as ALD < LDA, you may land "WHATEVER".

That's a very brave outlook on risk management. In my view the result is a near foregone conclusion which the crew may reflect upon while sitting in the weeds (or worse) somewhere in the overrun or beyond ... If emergency considerations provide no feasibly preferred option, so be it, but one had best have that decision process neatly tied up in bows for the Inquiry.

[cosmo kramer]

I buy FlightDetent's explanation.... ONE runway being with only one landing direction available. Hence, very special circumstances and to prevent the operation to routinely circumvent the dispatch requirement, by selecting 2 alternates, to an airport that basically can never be used according to the dispatch criteria.

What is practical is another discussion (one landing direction or not). Our performance software naturally calculates dispatch and inflight distances. However, if the dispatch requirement can't be met, it outputs "Landing weight too high for LDA", and doesn't calculate inflight either. :}

So what to do?? Flying into e.g. a 1700 meter runway, in a 738, fully loaded and with wet runway: Dispatch requirement is 1900 meters, ALD is 1300 (approx. values from the top of my head, don't beat me up if the percentages don't add up).

Software refuses to make any calculations! Solution is to chose another airport, with a longer runway and with similar pressure altitude and slope. I presented this problem to my Director of Flight Ops, and his reply was: "if it is wet, when you arrive, I recommend you divert!". If he doesn't want to take the chance, why should I?

400 meter margin may sound like a lot, but is it? Those ALD performance figures are not real, they were never demonstrated properly. The aircraft manufacturer is allowed to combine the best segments from different flights: Best flare, best touch down, best braking - and add each up a combined ALD. The PERFECT (unachievable) landing, made by a test pilot, with no regard for pax comfort and probably with little fear of making a hard landing and damage to the aircraft. Probably they had perfect tires and brakes installed as well.

Do you really want to try replicate than?

Personally, I do not need to sh!t my pant, and max effort braking coming to a halt with the nose hanging over the opposite approach lights. :sad:

[c100driver]

400 meter margin may sound like a lot, but is it? Those ALD performance figures are not real, they were never demonstrated properly. The aircraft manufacturer is allowed to combine the best segments from different flights: Best flare, best touch down, best braking - and add each up a combined ALD. The PERFECT (unachievable) landing, made by a test pilot, with no regard for pax comfort and probably with little fear of making a hard landing and damage to the aircraft. Probably they had perfect tires and brakes installed as well.

You have it the wrong way around. The certified landing distance in the AFM is constructed that way, but tyres and brakes are degraded to service life, the result is then multiplied by 1.67. The advisory landing distance is "real world" with allowance for line pilot operations and the inclusion of reverse thrust and in some cases a further 15% is added.

The International Federation of Airline Pilots has the best description of the difference between Certified and Advisory here:http://www.ifalpa.org/downloads/Level1/Briefing%20Leaflets/Aircraft%20Design%20&%20Operation/12ADOBL03%20-%20Certified%20vs%20advisory%20data%20on%20Boeing%20aircraft .pdf

[cosmo kramer]

Thank you for correcting me about the brakes. I wasn't sure hence, the "probably". The rest I wrote is however, to the best of my knowledge correct, also for the advisory (inflight) normal configuration landing distances.
The advisory landing distance is "real world" with allowance for line pilot operations and the inclusion of reverse thrust and in some cases a further 15% is added.
305 meter (1000 feet) air distance (from 50 feet), is the only allowance I can find. Please tell what allowance is further added?

The inclusion of reverse is a disadvantage for you. That means that the reversers are already included in the calculation, and they do not provide you with additional margin.

The 15% additive is only for braking action good to poor. Not for dry and wet. Wet data is not included in my QRH, but our performance tool calculates it as dry x 1.15 (factor, not additive), not a whole lot! If we are calculating to the last meter, with good or worse braking action, I am already sipping coffee at my alternate 15% additive or not.

[Journey Man]

I believe c100driver is pointing out that the beneficial effect of thrust reversers is not included in the certified landing data.

[c100driver]

My regulator has already required the 15% addition to inflight landing distance as recommended by the FAA in SAFO 06012 (hence "and in some cases a further 15% is added") as part of our OPS SPEC. So in my case we have a 15% buffer!


Landing Performance Assessments at Time of Arrival (Turbojets)
1. Purpose. This SAFO urgently recommends that operators of turbojet airplanes develop procedures for flightcrews to assess landing performance based on conditions actually existing at time of arrival, as distinct from conditions presumed at time of dispatch. Those conditions include weather, runway conditions, the airplane’s weight, and braking systems to be used. Once the actual landing distance is determined an additional safety margin of at least 15% should be added to that distance. Except under emergency conditions flightcrews should not attempt to land on runways that do not meet the assessment criteria and safety margins as specified in this SAFO.

3. Applicability:
a. This SAFO applies to all turbojet operators under Title 14 of the Code of Federal Regulations (14 CFR) parts 121, 135, 125, and 91 subpart K. The intent of providing this information is to assist operators in developing methods of ensuring that sufficient landing distance exists to safely make a full stop landing with an acceptable safety margin on the runway to be used, in the conditions existing at the time of arrival, and with the deceleration means and airplane configuration that will be used. The FAA considers a 15% margin between the expected actual airplane landing distance and the landing distance available at the time of arrival as the minimum acceptable safety margin for normal operations.

[safetypee]

FD, your argument is flawed – “You can land safely if ALD (actual landing distance) is less than LDA - in flight calculation requirement.”
The statement assumes that have a specific definition of ‘safe’ – the process of risk management (acceptable to the authority, etc, etc, and after the event), and also that you can calculate ALD with sufficient accuracy.

Using the Boeing format for ALD, it is generally recognised that the baseline data is not consistently achievable in normal operations, thus a factor is required to provide a starting point for corrections.
The alternative OLD, provides a much more realistically achievable baseline, FOLD provides a factor, normally 15%, so that this value is a better starting point for corrections and additions.


JM, c100, it would be incorrect to consider reverse as a benefit. Certificated data does not normally include credit for reverse, only if it mests the requirements for reliability. Comparing reversers with other systems, then they are not that reliable, and don’t forget that the engine can also fail.

The 15% in the SAFO might only increase ‘actual’ data to a value that can be expected to be achieved in normal operations, i.e. similar to the distances in OLD. FOLD adds a further 15% minimum with an expectation that the crew will add more according to the landing conditons.

[cosmo kramer]

Well congratulations for the 15% margin in USA. But this was a discussion about IR-OPS. That is the regulations of the European Union.

There is no requirement in EU or ICAO regulations to add 15% to ALD. Hence the requirement to make a near perfect (test pilot skills) landing to achieve the performance data we are provided.

[Journey Man]

Thank you CK, we do seem to be diverging slightly from the initial question.

EASA IR-OPS, normal Operations (Abnormal/Emergency situations not considered in the scope of this discussion)

[Skyjob]

Pre Dispatch the factor is applied with forecast landing weight but no credit given for reversers and planned using max manual brakes... Realistically this configuration is never actually used, hence the factor to achieve operational factors.

Actual inflight distances take into account actual landing weight, actual weather and runways conditions, actual configuration used such as auto brakes instead of max manual braking and use of reverse thrust vs no reverse or idle.

If unable pre-dispatch to use destination due forecast weather conditions, two alternates are required. If during the flight conditions at destination improved a new 'dispatch' calculation can be made which may well allow landing at destination, but rather than making two calculations only inflight calculations are now required.

The 305m air distance comes from the FAA 1000' markers used. ICAO national generally have markers set at 400m, and this correction of an additional 95m should always be taken into account. Actual location of the markers can be found in the AIP for the airport/nation thus when performance is limited the actual value should be used to ensure actual distance available for calculation purposes.

[safetypee]

J M, your opening questions identify ambiguity in interpreting CAT.POL. The options appear as to either use the dispatch factor in-flight – no further discussion, or to use some other aspect for the pre landing assessment.
In the latter case IR-OPS has the catchall – the pre landing assessment of landing performance should be judged as 'safe'.
Thus much of the debate above is about what is safe. This should relate to the requirements and guidance in IR-OPS, various advisory information, and an awareness of best practices in industry including accident statistics (those aspects which the lawyers will look at).

EASA publishes regulations (rules) and may provide guidance. The National Authorities implement the regulations, provide additional guidance, and oversee operations; the operator bears the final responsibility for safety – Captain.
There is scant EASA guidance for the in-flight aspects, but the European Action Plan for the Prevention of Runway Excursions suggests that FOLD (providing a minimum of 15% addition) is an acceptable interpretation of the requirement for pre landing assessment.
The UK CAA provides some guidance under winter operations – “The operator is required to demonstrate that it can ensure safe operations, and by applying the same additional safety margin to the in-flight performance assessment as to the dispatch assessment demonstrates an equivalent level of safety. An FAA Safety Alert for Operators published in 2006 (SAFO 06012) recommends an additional safety margin of at least 15% on actual landing distance, except in an emergency”.

European Action Plan for the Prevention of Runway Excursions. (www.skybrary.aero/bookshelf/books/2053.pdf)

UK CAA Landing During Winter Operations. (www.caa.co.uk/default.aspx?catid=2520&pagetype=90&pageid=14021)

[Journey Man]

At this point, after much deliberation, I'm converted to the factors being for planning purposes only.

We plan conservatively. We get a more direct routing, maybe a more favourable level, and save a bit of fuel. We're a little heavier, but we will be close to our planned weight and the conditions should be similar to those forecast. If it all changes horrendously for the worst, or we've had an abnormal situation, we revise with judgement. I take a while... But hopefully I get it in the end.

As I think safetypee spoke of in their previous thread (which was very informative - in case my previous post didn't seem to appreciate your input SP), we're judged over the course of months on a decision made in a dynamic situation.

Thanks to all who've contributed and helped clarify this for me. Without wanting to sound too sentimental: Merry Christmas!

[safetypee]

J M, :ok:

A word of caution for all, beware of assuming that ‘close to the expected weight or landing conditions’ will be OK. There are some circumstances where the dispatch margins are very small, even though the planning data appear to provide large safety factors; this is particularly so for wet runways - how wet is wet, how close to a contaminated situation, what is the condition of the tyres, type of runway surface material (beware concrete), grooves or not, brake selection, …
The wet planning data (AFM) is only a factor applied to the dry figures; there were no wet flight tests to obtain the performance and only a conservative (mid-point) assumption is used. With increasingly wet conditions, the risks in operation increase rapidly, and with a combination of effects there may be no margin at all; factored data = ALD, and thus operations require all of the flight accuracies implied in the base data.

There have been many accidents where crews assumed that the conditions were ‘close enough’, having no idea of what the actual margins were. Regulations require a pre-landing check of landing performance for all approaches; this should help crew appreciate what margins there are. A given margin should be evaluated against flight variability to guard against unforeseen flight conditions (AC 91-79 / quick rules of thumb); 5 kts fast and an extended flare can easily eat up 1500ft (airspeed deviation or change in wind). Similarly to guard against inaccuracies in the reporting of runway condition or wind, check the next worst condition, and for system failures ‘what if’, particularly lift dump, autobrake, and reverse if relied on.
And from the TALPA work, do not rely on PIREPS; these are purely subjective, depending on aircraft type and operation, and subject to error in action and reporting.
This sounds like a lot of work, but it’s what we are paid for, to be safe; and you can tell the judge after the event. A full evaluation for every landing should help build knowledge of actual landing performance for the conditions, particularly for the more junior pilots. In every debriefing ask – ‘where would we have stopped, what was the achieved landing distance’?

Merry Christmas, and I hope that Santa will not miscalculate landing distance.

Managing the Threats ...” (www.skybrary.aero/bookshelf/books/874.ppt)

[Kefuddle]

Dirk,
That paragraph that I quoted you clearly talks about factorization, making reference to full compliance with CAT.POL.A.230 from point (a) to (d), which includes the 60% factor, and before commencing the approach, which indicates without a doubt an in-flight situation.
Yes it does, but only for dry and marginal conditions when alternates are available within the limits. When dispatch calculations for the destination are able to perform for the most favourable runway in still air, there is no requirement to apply the 60% in flight.

In wet conditions, neither dispatch nor en-route calculations mandate the within 60% of LDA requirement.

[Journey Man]

Kefuddle - the regulation, CAT.POL.230 (f), relates to one specific situation whereby your LDR is longer than the most favourable runway in still winds. Why does this preclude a wet runway? It could be a runway that becomes limiting when wet, and the only way LDR could be met is with a favourable wind condition, calculated using all the restrictions laid out in (a) - (d). In this extraordinary situation, you require a second alternate.

[Kefuddle]

I don't know. The only way I can rationalise those regs is that dry runways are by far the most common condition encountered by crews and so are treated in a more conservative fashion.

If the 60% of LDA requirement was mandated for contaminated runways, I'm guessing that it would be extremely limiting and would pretty much result in considerable disruption for operators servicing a large number of fields during the winter.

[disininer]

Hello again everyone,

I read your posts carefully, yet still I see no trouble, please help me understand where the percieved dilemma comes from.

Typically (think of alternate aerodrome planning minima..), there are dispatch conditions, which are more restrictive than what is in fact operationally required to land. Then:

You can land safely if ALD (actual landing distance) is less than LDA - in flight calculation requirement. To put some margin in, the regulations require us to use ALD*1,6 coefficient in the dispatch phase. Thus: a) on purpose we dramatically reduce the statistical probability of really needing to land at ALD=LDA; b) if WX/MX/ conditions change unpredictably whilst airborne, the pilots are still allowed to use the full certified capabilities of the A/C without the 1,6 margin restraining them.

The NORMAL situation
1) big margins needs to be applied to dispatch
2) once in flight, as long as ALD < LDA, you may land "WHATEVER".
(statistical approach to hazards and risks)

I understand (f1) correctly, it provides - for a specific set of conditions - a waiver to the principle above:
So the ALTERNATIVE situation
1) the big margins normally in force (dispatch requirements) can be circumnavigated :O (2 alternates et al.)
2) but only if you promise to adhere to them before starting the approach. Which is not normally the case required.

To summarize:
A) The regulators ask us to use a hazard filter (ALD*1,6 at dispatch), and then allow us to operate all the way to the limits (in-flight: ALD <= LDA) if the situation requires so.

B) The regulators via (f1) allow us to depart with special provisions (two alternates) without the 1,6 "hazard filter" applied yet, but we still need to show compliance before commecing to land.


Completely agree. This is the best explanation I’ve heard so far!!.

[Banana Joe]

This is an old but interesting thread and still it isn't clear to me. My company manual doesn't even refer to this specific situation, probably because we don't operate into any field length weight limited runway. I would like to know if my interpretation of these regulations is correct.

If dispatch calculations don't allow to land within 60% of the LDA in still air conditions, we can still dispatch with an estimated landing weight greater than the landing field weight limit for still wind provided that:
a) with actual wind conditions (50% headwind and 150% tailwind), dispatch calculation permit landing within 60%;
b) 2 alternates meet the dispatch requirement in still air;
c) a pre-landing assessment to ensure compliance with point a is required only up to takeoff or in case of inflight replanning.

I'm really unsure about point C, but so far my interpretation is that after takeoff we can dispense with the 60% of LDA requirement and just work by the Inflight/Enroute performance data. That is, if we get a shortcut, save fuel and current gross weight doesn't meet the 60% dispatch requirement with actual wind, we can land as long as the required landing distance does not exceed the LDA.
And our inflight performance data incorporates a 15% margin for normal configurations.

I might have missed something in the thread and admittedly English isn't my first language. Any inputs?
​​​

[FlightDetent]

Quick observation:

your a) is overly simplified, I read the requirement differently
c) -> something probably lost in the translation, it does not add up (not a native language speaker either)

Few loose ends that stand out reading the whole thing again, happy to be corrected (and some goalposts may have moved over the time)

- AFM data are realistically achievable with equal conditions. It's not flight test data, flight test +10% springs to mind. As well flight test data is not ace-pilot data.
- under normal ops AFM data are not allowed to be used, Factored (+15% is a requirement)
- wish I never said "safely" as in the "you can land safely if ALD<LDA". I true pro should know better than to use the S word anyway, it's too amoebic and some of its inherent meanings do oppose each other. This is a realm of experts in that particular field. Proper wording should have been: "you are authorised to attempt the landing if ALD<LDA" which implies that a high degree of certainty about successful outcome exists.
- in a similar fashion to the
once in flight, as long as ALD < LDA, you may land "WHATEVER".
That's a very brave outlook on risk management. Although not quoted in full with the original meaning of "Having satisfied the ALD x 1,67 test at dispatch point, once in flight ..." it still was a poor choice of wording from my side. Saying " Having satisfied the ALD x 1,67 test at dispatch point, once in flight the scope of these paragraphs places no further restrictions as long as ALD < LDA" sounds 4 years wiser. ;)


Banana Joe note that both e.1) and e.2) must be complied with and each of them have a different alternate means of compliance offered by f) and g) respectively. This suggests that e.2 may be more restrictive than e.1 under some circumstances.

[safetypee]

After the TALPA review, FAA advisory, EASA mandated, the revised operational landing performance (opposed to ‘actual’ distance) is much closer to the factored performance required for dispatch.

Thus a pre landing assessment based on the most recent performance standard (OLD), plus 15% Minimum (FOLD), should minimise any difference between pre-deprture landing performance and that required by a inflight assessment.

What is the basis of your in flight data (all of Airbus is OLD / FOLD)

[FlightDetent]

I know, strong suspicion it already was when the original discussion took place.

It is important to understand what you say, however, this thread about the regulatory requirements might best be served using the terms utilized in them. From the viewpoint of procedural compliance on how should we handle the algorithm of POL.A.230, the numerical definitions of LDA / RLD / ALD are not part of the equation. As vitally important as they are.

Thinking of which, on a lighter note: ALD is historically mislabelled, isn't it? The Actual Landing Distance would be something the AAIB arrives to determine.:\