湿跑道和污染跑道运行管理规定

污染跑道：跑道正在或计划使用的长度和宽度范围内的表面区域，有很大一部分（不管是否为孤立区域）都覆盖有压实的雪、干雪、湿雪、雪浆、霜、冰和积水等一种或多种污染物。

污染跑道：飞机起降需用距离的表面可用部分的长和宽内超过 25％的面积（单块或多块区域之和）被超过3毫米（0.118英寸）深的积水，或者被当量厚度超过3毫米（0.118英寸）水深的融雪、湿雪、干雪，或者压紧的雪和冰（包括湿冰）等污染物污的跑道。如果跑道的重要区域，包括起飞滑跑的高速段或起飞抬轮和离地段的跑道表面被上述污染物覆盖，也应该算作污染跑道。

湿跑道：跑道正在或计划使用的长度和宽度范围内的表面区域内，覆盖有任何明显的湿气或不超过３毫米深的水。

湿跑道：当跑道表面覆盖有厚度等于或小于3毫米（0.118英寸）的水，或者当量厚度等于或小于3毫米（0.118英寸）深的融雪、湿雪、干雪；或者跑道表面有湿气但并没有积水时，这样的跑道被视为湿跑道。

湿滑跑道：湿跑道，而且其相当一部分的跑道表面摩阻特性确定为已经降级。

干跑道：跑道正在或计划使用的长度和宽度范围内的表面区域内，其表面无可见湿气且未被压实的雪、干雪、湿雪、雪浆、霜、冰和积水等污染物污染。

干跑道：飞机起降需用距离和宽度范围内的表面上没有污染物或可见的潮湿条件的跑道。对于经过铺筑、带沟槽或具有多孔摩擦材料处理，即使在有湿气时也能保持“有效干”的刹车效应的跑道也算干跑道。

对于 污染跑道、湿跑道、干跑道 的定义，CCAR121R7和AC121存在出入，CCAR121R7为有效的民航规章，而AC121为有效的规范性文件，于情于理应该以CCAR121R7为准？
但结果真的应该这样吗？答案是否定的。
1.CCAR121R7于2021年3月份发布，而《航空承运人湿跑道和污染跑道运行管理规定（有效）》于2021年11月份发布，所以说AC121应该是更具有时效性的文件。
2.其次我们可以在CAAC官网上看到旧版的咨询通告：CCAR AC-121-FS-2009-33 《航空承运人湿跑道和污染跑道运行管理规定（失效）》，其定义与CCAR121 R7定义相同。但是在新版的CCAR AC-121-FS-33R1 《航空承运人湿跑道和污染跑道运行管理规定（有效）》生效后，旧版的定义即现在CCAR121R7 的定义已经失效了。
综上，应当以我们AC121的定义为准。

CCAR121部污染跑道的定义：
污染跑道：飞机起降需用距离的表面可用部分的长和宽内超过 25％的面积（单块或多块区域之和）被超过3毫米（0.118英寸）深的积水，或者被当量厚度超过3毫米（0.118英寸）水深的融雪、湿雪、干雪，或者压紧的雪和冰（包括湿冰）等污染物污的跑道。如果跑道的重要区域，包括起飞滑跑的高速段或起飞抬轮和离地段的跑道表面被上述污染物覆盖，也应该算作污染跑道。
以及：
《运输机场跑道表面状况评估和报告规则》中的要求：
跑道表面有超过13毫米（含）的积水或其当量厚度的雪浆应立即开展除冰雪工作且通知机场管制单位禁止航空器起降，关闭跑道，同时向航空情报单位提供相关原始资料。
其中提到了当量厚度。
《运输机场跑道表面状况评估和报告规则》附件15给出了计算方法：

污染物的水当量厚度=以水表示的厚度值/污染物的水当量
例子：因规定在水当量深度达到13mm时应当关闭跑道，雪浆水当量范围在0.5-0.8之间，所以雪浆深度在16.25毫米和26毫米区间的某一个值时应当关闭跑道。当不能确定准确多少关闭跑道时，应采用保守值，即16.25毫米。

目前仅收集到降级影响起飞的依据。
根据空客飞机相关规定：
若跑道上覆盖物超过3mm，任何降级禁止起飞
若跑道上覆盖物不超过3mm：
  降级至RWYCC4时使用压实的雪
  降级至RWYCC3使用干雪10mm
  降级至RWYCC2或以下禁止其起飞

  The RCAM classifies frost on the runway as a RWYCC 5, along with wet conditions. In most circumstances, this equivalence may be used by the operator to assess takeoff and landing performance.
  In the experience of some of the contributors to the TALPA recommendations, frost can become very slippery when a thick layer of it accumulates. This would typically be the case for portions of a runway close to a lake or the sea, and in that case the airport should appropriately downgrade the RWYCC for the affected thirds of the runway.

  Some aerodromes may report “ICE CONFINED TO THE MACROTEXTURE” in the free text of an RCR, typically in combination with DRY SNOW ON TOP OF ICE and a RWYCC of up to 3.
The situation that is reflected with a report of Dry Snow on top of Ice in this case is a thin layer of snow falling onto a surface that has been swept, where the heat generated by the sweeper has melted the contamination which has then refrozen in the macrotexture. The aircraft tires are thus in contact with the macrotexture, and the friction measurements are often of the order associated with a wet runway.
  Dry Snow on top of Ice is categorized as a RWYCC 0 in the RCAM, but the aerodrome may upgrade to a RWYCC 3 when supported by all observations. This permits the operator to determine landing performance with the upgraded RWYCC, but what about takeoff?
For takeoff, performance must be assessed for the contaminant type. An appropriate contaminant would be one classified in the category 3-MEDIUM of the RCAM, without any drag or aquaplaning.
  Dry Snow 10mm (2/5”) performance, as and when provided for Airbus aircraft, fulfills this requirement. It is associated with the same constant friction coefficient as RWYCC 3 (0.16), there is no aquaplaning effect at high speed and, for the lowest published depth of 10mm (2/5”), no contaminant drag.
  Note that flight crew should not use “Slippery Wet” performance in this situation. Although this is identical to Dry Snow 10mm for the same inputs, it is permitted to use FLEX for this condition as it is not considered a contaminant. FLEX is not permitted for an upgraded winter contaminant.
Furthermore, should the aerodrome report a RWYCC 2 in these conditions, the use of Slush 1/4” performance is not necessarily conservative.

  EASA operational regulation CAT.OP.MPA.303 makes a minimum 15% margin on the in-flight landing distance mandatory. Airbus recommends this minimum margin, but shows unfactored data in the QRH (where available) and provides results for EFB computations when less than this minimum margin is available.
FlySmart will provide information also when the full margin specified by the administrator for the computation of the FLD is not available. There will even be results when the unfactored LD is longer than the LDA.
  Airbus is not planning to change this design. It was a deliberate choice. Indeed, the final decision always remains with the commander (see CAT.GEN.MPA.105), and in some situations, landing with less than 15% margin may be the best choice. To permit informed decisions, results are always displayed, but it is clearly highlighted when the full margin is not available (amber) or “negative” (red). Not every emergency is associated with an in-flight failure that affects performance, so this behavior also applies to “normal” landing conditions.

  FAA ACs 25-31 and 25-32, as well as AMC 25.1591/25.1592 stipulate that performance data should assume a uniform runway condition for the entire surface intended to be used. Airbus performance data is published in line with this guidance.
  Condition reporting by thirds, and even permitting several contaminants to be reported for any given third, is not new and part of the pre-GRF SNOWTAM format. The issue for a flight crew having to select the most appropriate contaminant and depth for a given reported situation was thus already a reality before implementation of the GRF. The GRF format simplifies the situation, as only the items listed in the RCAM are reportable. The selection of the prevalent contaminant thus falls on the airport operator, more precisely the runway inspector. Airports are advised to focus on the area around the wheel tracks for their reporting. Experience of the FAA with the TALPA deployed since October 2016 across the US shows that there have in fact been a very small number of reports in which different contamination conditions were given for different runway thirds.
  Nonetheless, Airbus has evaluated the possibility of determining performance when the contamination varies along the length of the runway, in different thirds. This has brought to light an instability of the optimization process. This option has thus had to be dismissed.
  In the case of different RWYCCs on different thirds, the basic recommendation is thus to use the lowest one. Disregarding certain RWYCCs for landing can be based on the portions of the runway expected to be used, but is much more difficult to justify for takeoff. Airbus performance applications will eventually permit entering a single contaminant and depth together with a RWYCC for takeoff. To evaluate the effect of different contaminants, the best but not perfect solution is to calculate for each reported contaminant and to retain the most conservative result. In case of doubt, it may be necessary to request additional information and/or runway cleaning from the airport.

  The FAA has adopted the recommendation of the TALPA ARC in 2016. One of these meant that airports should report slippery wet conditions whenever their runway failed minimum friction criteria when wet. Furthermore, this was implemented in such a way that the entire runway is systematically reported as being affected.
  Regarding the associated braking performance, the classification of a Slippery Wet runway in the category of RWYCC 3 consistent with Medium Braking Action was a compromise. Indeed, runways that have degraded braking action when wet due to e.g. rubber deposits or polishing, can be locally more slippery than that. However, in most cases this happens no more than locally, as the airport should plan maintenance when a section exceeding 100m is affected.
  For the original purpose of TALPA, which was to mandate an in-flight computation of representative landing performance, the classification as RWYCC 3 was sufficient, as a computation with RWYCC is appropriate for in-flight landing performance. In the ICAO and EASA context, the runway condition must be considered for dispatch both for takeoff and landing. Furthermore, for dispatch, the regulation requires that data is published for contaminant types and not RWYCC or braking action.
  Airbus has provided a specific runway condition for Slippery Wet in the operational performance computation tools to permit
appropriate dispatch performance assessment. This data was derived from the approved performance models for Dry Snow.
  Airbus dispatch landing data does not consider contaminant drag, the use of Dry Snow data is thus appropriate for Slippery Wet conditions, which are not associated with a fluid contaminant.
  For takeoff, contaminant drag needs to be accounted for. However, the AMC 25.1591 stipulates that such drag must be considered only above 10mm of Dry Snow. Airbus takeoff performance data published for a depth of 10mm thus does not include any contaminant drag effects.
  ICAO guidance is that in accounting for slippery wet conditions at takeoff, the chosen method should not unduly penalize operational procedures, such as the use of FLEX. Airbus has thus chosen to open the temperature range for Slippery Wet up to max FLEX.
  However, in line with recommendations of the Global Plan for Reduction of Runway Excursions, Airbus recommends using Max Reverse for landing on Slippery Wet runways, regardless of noise restrictions.
  In summary, Airbus recommends using the available runway condition “Slippery Wet” for dispatch computations for takeoff and landing.

  The concept of Specially Prepared Winter Runway was introduced in EASA regulation at the request of the Norwegian airports（挪威机场）. These airports may be subject to conditions of ice and snow at temperatures well below freezing that prevent the use of deicing chemicals. However, the types of operations they have require a minimum RWYCC of 4. Standard upgrading procedures only permit a maximum RWYCC of 3 to be reported when the primary RWYCC is 0 or 1. The airports then apply hot wet grit to the contaminant, which freezes to the ice on the runway and creates a very abrasive surface. Aerodromes must demonstrate the effectiveness of this treatment with aircraft data collected during landings in these conditions. When an approval has been obtained from their national authorities, the airport can then report a SPWR as appropriate, in combination with a primary RWYCC of 4, which may be downgraded in line with normal downgrading procedures when necessary. The approval process applies to the airport, so any airline that operates at this airport and receives a report of SPWR with a RWYCC of 4 can calculate performance with this “improved friction”.
  Airbus does not plan to provide a specific contaminant type for this computation, but the use of the existing “Compacted Snow” data is perfectly equivalent and may be used in this situation.

  The means of compliance for JAR25X1591 and EASA CS 25.1591 provided, up to CS25 Amdt 26, a friction coefficient of 0.05 to be used in the computation model for icy runways, the same that applies above aquaplaning speed on fluid contaminants, i.e. in the case of total loss of contact of the tire with the runway surface. This value had been selected as a kind of worst case and was intended to be representative of a surface affected by wet ice. In line with this guidance, Airbus takeoff and landing performance provided at the time for an icy runway used this very low coefficient.
  Surfaces affected by wet ice are extremely slippery, and stopping and lateral control are severely affected. Airbus had initially prohibited planning operations on icy surfaces. It was changed to “not recommended“, since some northern airports were operating with ice on the runway in very cold conditions over extended periods of time, and with considerably higher available braking action than assumed in the EASA model. Not allowing operations proved very limiting to some operators.
  In 2009, the TALPA ARC recommended providing data for in-flight landing distances, and proposed a change to the friction coefficients associated with various runway conditions, expressed either in terms of contaminant type and depth, Runway Condition Code or Braking Action. These are the categories you find in the Runway Condition Assessment Matrix, and each has an associated friction coefficient characteristic which is mostly based on the EASA coefficients of AMC 25.1591, but with some notable changes to ensure a continuity in the data and reversible reading (from left to right and right to left) of the RCAM. In the process, most coefficients were adjusted downwards, to more conservative data, except for ice, where the coefficient was adjusted upwards, to 0.08. The rationale was that there was no use providing data for non-operable conditions.
  In the initial landing performance data published by Airbus in line with these recommendations, the new models were adopted except for ice. On request from operators, Airbus later introduced a new runway condition for A320, A330, A340, A350 and A380 with an increased friction coefficient of 0.07 and removed the existing performance data for icy runway. The new condition was called Ice Cold & Dry to make a distinction with the prior level. Indeed, EASA wanted to ensure that there would be no confusion between the improved performance level and the range of braking action it covered. At this time, operations on wet ice were explicitly prohibited. Note that this friction coefficient adjustment also affected 1-POOR landing distances. The rationale for not using the value of 0.08 recommended by TALPA was that Airbus wanted to ensure that the performance computation with the ICE COLD & DRY covered an unreported degradation to 0.05, which was not possible with recommended margins when assuming 0.08.
  While it is not forbidden to plan operations on Ice Cold & Dry, this is still a relatively slippery condition and crosswind limits should be observed closely. There should be no indications of potentially degraded conditions, such as a Pilot Report of Braking Action Less Than Poor, temperatures close to the freezing point and potentially a small difference with the dew point.
  Note that for the A220, a conservative coefficient of 0.06 is used for Ice runway condition.

  Some states will continue to report measured friction values in an optional field available in the ICAO format of the SNOWTAM Situational Awareness Section. When this is the case, information on this practice should be included in the Snow Plan of the airport or the national AIP. Friction reporting may be the primary and sole method used by airports to which the GRF does not apply, such as military airports.
  Airbus had put into place an option in FlySmart to make takeoff and landing performance computations with an input of Reported Braking Friction. Airbus recommends that this option should not be used anymore, for the following reasons:
  (1)The RWYCC reported in the GRF RCR is the result of an overall assessment of runway conditions, taking into account all observations made by a trained runway inspector. This may include friction measurements. When using the RWYCC as an input to a computation, the flight crew benefits from this overall assessment. When using a reported friction coefficient, the computation is based only on a single type of information, the measured friction. This may be misleading, as there is no strong correlation with aircraft performance.
  (2) Measured friction is determined with a variety of devices using a variety of measurement principles different from the mechanisms that determine the behavior of an aircraft tyre braked through an anti-skid system on the same surface. Some airlines have developed conservative correlation equations between reported and effective aircraft wheel friction coefficients that may be applicable to a very well defined set of circumstances. Airbus has no experience with such correlations and cannot provide any assistance with establishing such correlations.This is why Airbus recommends to base in-flight landing performance computations on the reported RWYCCs, for which the method of determination was built to be representative of aircraft performance.
  Airbus recommends never to use reported friction measurements to upgrade the assumed RWYCC.
  Airbus recommends not to base performance computations only on reported friction. However, in particular at airports to which the GRF does not apply, flight crew should not disregard friction values below the expected for a given contamination state. In doubt, flight crew should delay takeoff and request additional information.

  In some cases the airport may clear less than the full width of the runway and provide this information in the SNOWTAM. In such cases, the reported RWYCC and contaminants, their coverage and their depth, only reflect the situation on the cleared section.
  Airbus aircraft are generally certified based on flight testing performed on runways with a nominal width of 45m. Depending on the condition of the non-cleared runway edges, narrow runway penalties do not necessarily apply for runways that have not been cleared to the full width. Operators should provide guidance when operations on runways with a cleared width less than 45m may be conducted, and if performance penalties should be considered.
国内多数航司手册中明确要求禁止在宽度45m以上运行常见空客航空器，需要以手册为准。这也是为什么一定要关注雪情通告H项。
  Such guidance may consider the following:
  Two scenarios can apply when the cleared runway width is less than the full runway width:
  (a) The contamination type and depth on the runway edges is within the operational capabilities of the aircraft. That means that there are no contaminant types that are listed in the RWYCC 0 / Braking Action Less Than Poor, AND the depth of the contamination does not exceed the maximum published depth for that type of contamination. In that case, the flight crew should consider determining performance based on the type of contamination on the edges in addition to that on the cleared part of the runway and retain the more limiting result.
  (b) The SNOWTAM includes a notification of snowbanks on the runway, OR the type and depth or contamination is outside the operating capabilities of the aircraft, i.e. either results in less than poor braking action or its depth is in excess of the maximum published depth. In that case, it is not safe to roll and brake outside of the cleared width of the runway.
In scenario (b), if the cleared width is less than 45m, the operator should consider that operational limitations for a narrow runway apply, if available.
  The nominal (baseline) runway width of 45m below which a runway is to be considered as narrow stems from the Annex 14 standards for runway construction. These standards are formulated as a function of some aircraft characteristics such as wing span and main gear wheel track (e.g. Airbus A320 family aircraft have a code letter C) or reference field length (code number). This latter criterion introduces the discrimination based on takeoff weight, as ICAO recommends a minimum runway width of 45m for code number 4 (above 1800m) and 30m for code number 3 (between 1200 and 1800m). It is however important to note that these criteria are for airport design and do not constitute a limitation for the operations of aircraft.
  Only the Airbus A320 and A380 aircraft families have a minimum runway width stated in the AFM. To operate A320 aircraft on runways below 45 m, as stated in the AFM, the MOD 30397 is required. This MOD has no physical impact on the aircraft, but introduces restrictions on the maximum crosswind and may include penalties on takeoff performance due to increased VMCG limitations. The VMCG limitation, if applicable, will be automatically taken into account when the runway width in entered into the airport manager or the PEP/TLO. The maximum crosswind limitation is available in the AFM supplement or the FCOM. Most of the aircraft databases already include this penalty, as can be identoified by the availability of the Width(m) field in the PEP interface. However, operations must not be conducted without embodiment of the MOD first.
  For the other Airbus aircraft families, no minimum runway width is stated in the AFM, but all flight testing was done on a 45mrunways. Additional information on minimum runway widths can be found in the article on Airbus World entitled: “What is the minimum runway width in order to operate Airbus aircraft?”

  Airbus demonstrates that up to the maximum published depth of water or slush, none of the following will occur:
• Significant ingestion of the fluid in the engine
• Damage to the airframe due to the hydrostatic pressure of the spray.

  For low density contamination, Airbus does not conduct a specific demonstration and dry snow depth is thus limited to 100 mm by regulation. Additionally, Airbus assesses the capability of the aircraft to accelerate to lift off speed up to the maximum published depth.
  As such, the maximum published depth constitutes a limitation and must not be exceeded over significant portions of the runway.

  In the case of a runway affected with a winter contaminant on less than 25% of one third, the airport will be able to report a RWYCC of 6 for that third. When the coverage extends to more than 10% in at least one third, a SNOWTAM will be published, and this SNOWTAM could state a RWYCC of 6 for all thirds for a contaminant exceeding the minimum depth threshold of 3mm but remaining under the 25% coverage threshold for all thirds.
  For a runway affected by water, the situation is different, as in the ICAO and EASA provisions for the GRF there is no minimum threshold for the coverage. It is stated that a runway is considered wet for performance purposes when there is any visible moisture. The reason for this absence in minimum depth is that the analysis of some in-service events has shown that a significant drop in friction could occur even during light rain. While in terms of depth, this concept is consistent with that of the FAA, for the coverage, the FAA has adopted the same 25% coverage threshold as for contaminants. So when the runway is affected by more than 3mm of standing water on less than 25% of the surface, the report outside the US would state a RWYCC of 5.
  This reporting method, while entirely intentional, leads to an inconsistency in the conservatism of the approach, meaning that if the runway is affected by small patches of a winter contaminant, the report shows a RWYCC of 6 while it would show a 5 in the case of wet patches.
  This is deemed acceptable as the performance impact of less than 25% of ice in the worst location is compensated by the minimum margin of 15% on the landing distance.No such fixed margin exists for the Accelerate Stop Distance. However, the “margin” is in-built in the assumptions of the ASD, which is calculated with an engine failure just before V1. Moreover, there is a very limited exposure to rejected takeoffs.

  The main driver behind the changes made by the GRF is to enhance safety for landing on contaminated runways. As a result, a new parameter is now reported, the RWYCC, the intent of which is to permit a direct computation of landing performance relevant to the assessed condition of the runway.
  The GRF gives the airport the possibility to downgrade or upgrade a primary RWYCC, which is determined with the RCAM based on the observed contaminant type and depth. Downgrades are part of the basic assessment process and can be applied for an initial report whenever the runway inspector considers that it is appropriate based on all other observations, such as vehicle braking and control or local knowledge. Upgrades can be made whenever they are supported by all information available to the inspector.While downgrading can be applied from any primary RWYCC in any condition, including wet, upgrades can only be made for primary RWYCCs of 0 or 1, and the maximum upgrade is to a RWYCC of 3.
  An upgraded RWYCC can be directly used for the in-flight landing performance assessment of the flight crew. For takeoff however, it is necessary to account for contaminant drag. Selection of a contaminant type and depth from those categorized against the reported RWYCC in the RCAM is not systematically conservative.
  In the context of writing the guidance in the ICAO Doc 10064 Aeroplane Performance Manual, this was discussed but agreement could only be reached on the following paragraph:

QUOTE
  Operators should provide recommendations in their operations manual on how to determine performance in such situations, considering that contaminant drag effects may not allow to identify simply a contaminant representative of the reported condition. In case of doubt, the prudent approach is to delay take-off. However, due to the low exposure to rejected take-off, it may be sufficient todetermine performance in nominal conditions and to adopt appropriate operational procedures such as considering reduced crosswind limits, using the full length of available runway. And potentially avoiding a rolling take-off.
UNQUOTE
  Airbus has advocated in industry forums that a better solution should be found. Manufacturers generally are not in favor of providing data for the full list of reportable conditions, as for most cases perfectly equivalent data is available with the current
EASA AMC 25.1591 set.

  For the scenario of downgraded RWYCC, it has been identified that the contaminant types and associated depths available for RWYCC 2 in particular, the contaminant drag systematically taken into account in the computation can in same cases lead to nonconservative results. So two things have been agreed by the industry:- for future designs, aircraft manufacturers should publish data for all contaminants from zero depth, i.e. no drag and no aquaplaning.- for RWYCC downgrades, the SCAP for takeoff should be able to take into account an input of both a contaminant type and depth, and a RWYCC.The computation should then be based on the lower friction coefficient of the characteristics defined for both these inputs for each ground speed. This mechanism ensures that the operational takeoff performance computation will systematically be compliant with the nominal AFM condition, which is based on contaminant type and depth only, but also take into account the actual conditions worse than assumed in the model.

  Airbus will adopt this SCAP option in the OCTOPUS computation core, but it needs to fit it into the existing software development schedule. This option should be available mid 2022. It is important to note that this change is not a prerequisite without which operations in a GRF environment cannot be conducted. When in doubt, takeoff can be delayed.
  In the meantime, operators may calculate takeoff performance (for hard contaminants only) based on the following:
（1）Downgrade to RWYCC 4: Calculate for Compacted Snow
（2）Downgrade to RWYCC 3: Calculate for Dry Snow 10mm
（3）Downgrade to RWYCC 1: Calculate for Ice Cold & Dry

  This addresses downgraded RWYCCs. For upgrades however, there is currently no regulatory basis for taking the benefit at takeoff.
  An airline may wish to seek and obtain approval for using improved performance from their local authorities. Even in that case, from a pure performance data perspective, there is no technical solution when the upgraded RWYCC is 2. For upgrades to RWYCC 3, a computation with Dry Snow 10mm would provide appropriate performance data, as neither drag nor aquaplaning is accounted for the lowest published depth of dry snow, as per AMC 25.1591.
  Note that for the A220, implementation of the possibility to downgrade or upgrade a primary RWYCC is currently under study.