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  Contaminated Runways  

Airport/Runway Data

 


 

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Figure: Photograph of the accident airplane in the roadway intersection, from NTSB Report, Figure 1.

  1. Runway Contamination Defined
  2. Runway Contamination Measured
  3. Regulatory Limitations
  4. Safety Alert For Operators 06012
  5. Pilot Procedures — Computing Balanced Field Distances
  6. Pilot Procedures — Computing Landing Distances
  7. Pilot Procedures — Dealing with Crosswinds
  8. Pilot Procedures — Avoiding Hydroplaning
  9. Pilot Procedures — The Flare
  10. Pilot Procedures — Braking
  11. Pilot Procedures — Reverse Thrust
  12. Aircraft Manufacturer Approaches to Runway Contamination

1. Runway Contamination Defined

United States — All Operators

[Aeronautical Information Manual, Pilot/Controller Glossary] CONTAMINATED RUNWAY− A runway is considered contaminated whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present. A runway is contaminated with respect to rubber deposits or other friction-degrading substances when the average friction value for any 500-foot segment of the runway within the ALD fails below the recommended minimum friction level and the average friction value in the adjacent 500-foot segments falls below the maintenance planning friction level.

[AC 91-79, appendix 4, ¶10.b.(2)] NOTE: The FAA has taken the position that a runway does not need to be reflective to be considered wet. If a runway is contaminated or not dry, that runway is considered wet.

The U.S. definition is rather simple but doesn't offer a lot of detail.

International Civil Aviation Organization - Commercial Operators

[ICAO Annex 6, Part 1, Att C, Page C-2]

  1. Contaminated runway. A runway is contaminated when more than 25 per cent of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by:
    • water, or slush more than 3 mm (0.125 in) deep;
    • loose snow more than 20 mm (0.75 in) deep; or
    • compacted snow or ice, including wet ice.
  2. Dry runway. A dry runway is one which is clear of contaminants and visible moisture within the required length and the width being used.
  3. Wet runway. A runway that is neither dry nor contaminated.
  4. Note 1.— In certain situations, it may be appropriate to consider the runway contaminated even when it does not meet the above definition. For example, if less than 25 per cent of the runway surface area is covered with water, slush, snow or ice, but it is located where rotation or lift-off will occur, or during the high speed part of the take-off roll, the effect will be far more significant than if it were encountered early in take-off while at low speed. In this situation, the runway should be considered to be contaminated.

    Note 2.— Similarly, a runway that is dry in the area where braking would occur during a high speed rejected take-off, but damp or wet (without measurable water depth) in the area where acceleration would occur, may be considered to be dry for computing take-off performance. For example, if the first 25 per cent of the runway was damp, but the remaining runway length was dry, the runway would be wet using the definitions above. However, since a wet runway does not affect acceleration, and the braking portion of a rejected take-off would take place on a dry surface, it would be appropriate to use dry runway take-off performance.

The ICAO definition in Annex 6, Part I, applies only to commercial aviation. The same definition does not appear in Part II for general aviation.

European Union — Commercial Operators

[EU Ops, §1.480(a)] and [JAR OPS, § 1.480]

  1. "Contaminated runway". A runway is considered to be contaminated when more than 25 % of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by the following:
    1. surface water more than 3 mm (0,125 in) deep, or by slush, or loose snow, equivalent to more than 3 mm (0,125 in) of water;
    2. snow which has been compressed into a solid mass which resists further compression and will hold together or break into lumps if picked up (compacted snow); or
    3. ice, including wet ice.
  2. "Damp runway". A runway is considered damp when the surface is not dry, but when the moisture on it does not give it a shiny appearance.
  3. "Dry runway". A dry runway is one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain "effectively dry" braking action even when moisture is present.
  1. "Wet runway." A runway is considered wet when the runway surface is covered with water, or equivalent, less than specified in subparagraph (a)(2) above or when there is sufficient moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water.

EU Ops 1 and JAR OPS are also intended for commercial aviation only.

Bombardier Example

[Bombardier BD-700 Airplane Flight Manual, §07-03-01-1, ¶1.B.]

  1. RUNWAY CONTAMINATED BY STANDING WATER, SLUSH OR LOOSE SNOW
    A runway is considered to be contaminated, when more than 25% of the runway surface area (whether in isolated areas or not), within the required length and width being used, is covered by more than 3 millimeters (1/8 inch) of standing water or its equivalent in slush or loose snow (see table below):
  2. STANDING WATER SLUSH LOOSE WET SNOW LOOSE DRY SNOW
    3.2 mm (0.125 in) 3.8 mm (0.15 in) 7.6 mm (0.30 in) 15.2 mm (0.60 in)
    6.4 mm (0.25 in) 7.6 mm (0.30 in) 15.2 mm (0.60 in) 30.5 mm (1.2 in)

  3. RUNWAY CONTAMINATED BY COMPACTED SNOW
    A runway is considered to be contaminated by compacted snow when covered by snow which has been compacted into a solid mass which resists further compression and will hold together or break into lumps if picked up.
  4. RUNWAY CONTAMINATED BY ICE
    A runway surface condition where braking action is expected to be very low, due to the presence of ice.

Gulfstream

[Gulfstream G450 Operational Information Supplement, G450-OIS-02, Section A.]

  • A runway is considered dry if it is clear of visible moisture. A damp runway, which has a moisture layer that is non- reflective, is also considered dry.
  • A runway is considered to be wet when there is sufficient moisture to cause it to appear reflective but the depth of the water is not more than 3 mm (0.125 in.).
  • A runway surface is considered contaminated when more than 25% of the runway surface area is covered with standing water, slush, loose snow (dry or wet), compacted snow or ice.

2. Runway Contamination Measured

Braking Action Reports

[Aeronautical Information Manual §4−3−8]

  • When available, ATC furnishes pilots the quality of braking action received from pilots or airport management. The quality of braking action is described by the terms "good," "fair," "poor," and "nil," or a combination of these terms. When pilots report the quality of braking action by using the terms noted above, they should use descriptive terms that are easily understood, such as, "braking action poor the first/last half of the runway," together with the particular type of aircraft.
  • For NOTAM purposes, braking action reports are classified according to the most critical term ("fair," "poor," or "nil") used and issued as a NOTAM(D).
  • When tower controllers have received runway braking action reports which include the terms poor or nil, or whenever weather conditions are conducive to deteriorating or rapidly changing runway braking conditions, the tower will include on the ATIS broadcast the statement, "BRAKING ACTION ADVISORIES ARE IN EFFECT."
  • During the time that braking action advisories are in effect, ATC will issue the latest braking action report for the runway in use to each arriving and departing aircraft. Pilots should be prepared for deteriorating braking conditions and should request current runway condition information if not volunteered by controllers. Pilots should also be prepared to provide a descriptive runway condition report to controllers after landing.

When considering pilot reports, consider the aircraft type. It may seem counter intuitive, but it may actually be easier to stop a larger, heavier aircraft than a smaller one. More weight on the wheels can make it easier for a Boeing 747 to stop than a Cessna 150.

More about this: Braking Action.

Canadian Runway Friction Index (CRFI) Decelerometers

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Runway friction tester, from ICAO Doc 9137, Part 2, figure 5-6.

[Transport Canada Aeronautical Information Manual, ¶1.1.4] Many airports throughout Canada are equipped with mechanical and electronic decelerometers which are used to obtain an average of the runway friction measurement. The average decelerometer reading of each runway is reported as the Canadian Runway Friction Index (CRFI). Experience has shown that results obtained from the various types of decelerometers on water and slush are not accurate, and the CRFI will not be available when these conditions are present.

Canada is one of the few countries that has stepped up to the plate and tried to quantify runway friction values and their impact on runway performance. More about this: Runway Friction. Even if the airport you are using doesn't have these decelerometers, the CRFI can be of use to you.

See below, Pilot Procedures and Techniques.

Friction Reports μ (Mu)

[Aeronautical Information Manual §4−3−9]

  • MU (friction) values range from 0 to 100 where zero is the lowest friction value and 100 is the maximum friction value obtainable. For frozen contaminants on runway surfaces, a MU value of 40 or less is the level when the aircraft braking performance starts to deteriorate and directional control begins to be less responsive. The lower the MU value, the less effective braking performance becomes and the more difficult directional control becomes.
  • When the MU value for any one-third zone of an active runway is 40 or less, a report should be given to ATC by airport management for dissemination to pilots.
  • No correlation has been established between MU values and the descriptive terms "good," "fair," "poor," and "nil" used in braking action reports.

The Aeronautical Information Manual seems to discount any connection between MU and good/fair/poor/nil qualifiers and you hardly hear the term "mu" in the United States. But the ICAO calculated coefficient seems suspiciously similar.

ICAO SNOWTAMs

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Figure: SNOWTAM Format, from ICAO Annex 15 Appendix 2.

A SNOWTAM is a "Special Series NOTAM"

[ICAO Annex 15] ¶5.2.3] Information concerning snow, slush, ice and standing water on aerodrome/heliport pavements shall, when reported by means of a SNOWTAM, contain the information in the SNOWTAM Format in Appendix 2.

USAF Runway Condition Reading

[U.S. FAA Order JO 7110.10W §4-4-3 ¶11] USAF has established RCR procedures for determining the average deceleration readings of runways under conditions of water, slush, ice, or snow. The use of RCR code is dependent upon the pilot's having a stopping capability chart specifically applicable to his/her aircraft. USAF offices furnish RCR information at airports serving USAF and ANG aircraft.

Our Air Force flight manual charts had performance numbers with Runway Condition Readings (RCR). An RCR of 23 was considered dry, 9 was wet, and 4 was icy. The exact number tends to change a few points here and there, but those are close. If you are at an airport with military airplanes, they might just have an RCR for you. Can you enter your chart with an RCR? Probably not. But it is more information than you had before you asked.

Conclusion

Chances are you will be basing your landing decision on words like "good," "fair," "poor," and "nil." If you are lucky, you might have decelerometer data with a CRFI, μ, or RCR number to evaluate. What you do with these reports depends on your the regulatory guidance applicable to your operation, your aircraft manufacturer's procedures, your operator's standard operating procedures, and your personal pilot techniques and preferences. If your flight manual doesn't have the guidance you are looking for, there is a way to bring another conservative approach to contaminated runways, shown below under Pilot Procedures.

3. Regulatory Limitations

Commercial Operators

[14 CFR 121, §121.195(d)] and [14 CFR 135, §135.385(d)] Unless, based on a showing of actual operating landing techniques on wet runways, a shorter landing distance (but never less than that required by [the dry runway rules] of this section) has been approved for a specific type and model airplane and included in the Airplane Flight Manual, no person may take off a turbojet airplane when the appropriate weather reports or forecasts, or any combination of them, indicate that the runways at the destination airport may be wet or slippery at the estimated time of arrival unless the effective runway length at the destination airport is at least 115 percent of the runway length required under [the dry runway rules] of this section.

[ICAO Annex 6, Part 1, Att C, Page C-7]

  • 7.2.1. When the appropriate weather reports or forecasts or a combination thereof indicate that the runway at the estimated time of arrival may be wet, the landing distance available should be at least 115 per cent of the required landing distance determined in accordance with [dry runway conditions].
  • A landing distance on a wet runway shorter than that required by 7.2.1 but not less than that required by [dry runway conditions] may be used if the flight manual includes specific additional information about landing distance on wet runways.
  • Part 1 of Annex 6 applies to commercial aircraft and basically says you will use 115% of dry runway data unless your flight manual gives you data that allows a smaller factor. There does not appear to be a similar requirement for general aviation aircraft.

[JAR OPS, §1.480]

  1. An operator shall ensure that when the appropriate weather reports or forecasts, or a combination thereof, indicate that the runway at the estimated time of arrival may be wet, the landing distance available is at least 115% of the required landing distance, determined in accordance with [dry runway rules]
  2. An operator shall ensure that when the appropriate weather reports or forecasts, or a combination thereof, indicate that the runway at the estimated time of arrival may be contaminated, the landing distance available must be at least the landing distance determined in accordance with sub- paragraph (a) above, or at least 115% of the landing distance determined in accordance with approved contaminated landing distance data or equivalent, accepted by the Authority, whichever is greater.
  3. A landing distance on a wet runway shorter than that required by sub-paragraph (a) above, but not less than that required by [dry runway rules], may be used if the Aeroplane Flight Manual includes specific additional information about landing distances on wet runways.
  4. A landing distance on a specially prepared contaminated runway shorter than that required by sub-paragraph (b) above, but not less than that required by [dry runway rules], may be used if the Aeroplane Flight Manual includes specific additional information about landing distances on contaminated runways.

[JAR OPS, §1.565(c)(5)] On a wet or contaminated runway the take-off mass must not exceed that permitted for a take-off on a dry runway under the same conditions.

Fractional Operators

[14 CFR 91, §91.1037(e)] Unless, based on a showing of actual operating landing techniques on wet runways, a shorter landing distance (but never less than that required by [dry runway rules] of this section) has been approved for a specific type and model airplane and included in the Airplane Flight Manual, no person may take off a turbojet airplane when the appropriate weather reports or forecasts, or any combination of them, indicate that the runways at the destination or alternate airport may be wet or slippery at the estimated time of arrival unless the effective runway length at the destination airport is at least 115 percent of the runway length required under [dry runway rules] of this section.

This applies only the 14 CFR 91 Subpart K Fractional Operators.

Conclusion

There isn't a lot of regulatory guidance to deal with runway contamination, other than to say add 15% on a wet runway if you are a commercial operator. Pilot's should understand their aircraft manufacturer provided guidance, to be sure. But they should also employ a safety margin, as became clear because of mishap in 2005.

4. Safety Alert for Operators (SAFO) 06012

[SAFO 06012]

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.

5.f. Airplane flight manual (AFM) landing performance data are determined during flight- testing using flight test and analysis criteria that are not representative of everyday operational practices. Landing distances determined in compliance with 14 CFR part 25, section 25.125 and published in the FAA-approved AFM do not reflect operational landing distances (Note: some manufacturers provide factored landing distance data that addresses operational requirements.) Landing distances determined during certification tests are aimed at demonstrating the shortest landing distances for a given airplane weight with a test pilot at the controls and are established with full awareness that operational rules for normal operations require additional factors to be added for determining minimum operational field lengths. Flight test and data analysis techniques for determining landing distances can result in the use of high touchdown sink rates (as high as 8 feet per second) and approach angles of -3.5 degrees to minimize the airborne portion of the landing distance. Maximum manual braking, initiated as soon as possible after landing, is used in order to minimize the braking portion of the landing distance. Therefore, the landing distances determined under section 25.125 are shorter than the landing distances achieved in normal operations.

5.i. Manufacturer-supplied landing performance data for conditions worse than a dry, smooth runway is normally an analytical computation based on the dry runway landing performance data, adjusted for a reduced airplane braking coefficient of friction available for the specific runway surface condition. Most of the data for runways contaminated by snow, slush, standing water, or ice were developed to show compliance with European Aviation Safety Agency and Joint Aviation Authority airworthiness certification and operating requirements. The FAA considers the data developed for showing compliance with the European contaminated runway certification or operating requirements, as applicable, to be acceptable for making landing distance assessments for contaminated runways at the time of arrival.

5.e. Runway surface conditions may be reported using several types of descriptive terms including: type and depth of contamination, a reading from a runway friction measuring device, an airplane braking action report, or an airport vehicle braking condition report. Unfortunately, joint industry and multi-national government tests have not established a reliable correlation between runway friction under varying conditions, type of runway contaminants, braking action reports, and airplane braking capability. Extensive testing has been conducted in an effort to find a direct correlation between runway friction measurement device readings and airplane braking friction capability. However, these tests have not produced conclusive results that indicate a repeatable correlation exists through the full spectrum of runway contaminant conditions. Therefore, operators and flightcrews cannot base the calculation of landing distance solely on runway friction meter readings. Likewise, because pilot braking action reports are subjective, flightcrews must use sound judgment in using them to predict the stopping capability of their airplane. For example, the pilots of two identical aircraft landing in the same conditions, on the same runway could give different braking action reports. These differing reports could be the result of differences between the specific aircraft, aircraft weight, pilot technique, pilot experience in similar conditions, pilot total experience, and pilot expectations. Also, runway surface conditions can degrade or improve significantly in very short periods of time dependent on precipitation, temperature, usage, and runway treatment and could be significantly different than indicated by the last report. Flightcrews must consider all available information, including runway surface condition reports, braking action reports, and friction measurements.

5.e.(1) Operators and pilots should use the most adverse reliable braking action report, if available, or the most adverse expected conditions for the runway, or portion of the runway, that will be used for landing when assessing the required landing distance prior to landing. Operators and pilots should consider the following factors in determining the actual landing distance: the age of the report, meteorological conditions present since the report was issued, type of airplane or device used to obtain the report, whether the runway surface was treated since the report, and the methods used for that treatment. Operators and pilots are expected to use sound judgment in determining the applicability of this information to their airplane's landing performance.

7.d. If wet or contaminated runway landing distance data are unavailable, the factors in Table 2 should be applied to the pre-flight planning (factored) dry runway landing distances determined in accordance with the applicable operating rule (e.g., sections 91.1037, 121.195(b) or 135.385(b). Table 2 should only apply when no such data are available. The factors in Table 2 include the 15% safety margin recommended by this guidance, and are considered to include an air distance representative of normal operational practices. Therefore, operators do not need to apply further adjustments to the resulting distances to comply with the recommendations of this guidance.

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Figure: Multiplication factors to apply to the factored dry runway landing distances when the data for the specified runway condition are unavailable, from SAFO 06012, Table 2.

* The factored dry runway landing distances for use with Table 2 must be based on landing within a distance of 60% of the effective length of the runway, even for operations where the preflight planning (factored) dry runway landing distances are based on landing within a distance other than 60% of the effective length of the runway (e.g., certain operations under part 135 and subpart K of par t91). To use unfactored dry runway landing distances, first multiply the unfactored dry runway landing distance by 1.667 to get the factored dry runway landing distance before entering Table 2 above.

NOTE: These factors assume maximum manual braking, autospoilers (if so equipped), and reverse thrust will be used. For operations without reverse thrust (or without credit for the use of reverse thrust) multiply the results of the factors in Table 2 by 1.2. These factors cannot be used to assess landing distance requirements with autobrakes.

e. The landing distance assessment should be accomplished as close to the time of arrival as practicable, taking into account workload considerations during critical phases of flight, using the most up-to-date information available at that time. The most adverse braking condition, based on reliable braking reports or runway contaminant reports (or expected runway surface conditions if no reports are available) for the portion of the runway that will be used for the landing should be used in the actual landing performance assessment. For example, if the runway surface condition is reported as fair to poor, or fair in the middle, but poor at the ends, the runway surface condition should be assumed to be poor for the assessment of the actual landing distance. (This example assumes the entire runway will be used for the landing). If conditions change between the time that the assessment is made and the time of landing, the flightcrew should consider whether it would be safer to continue the landing or reassess the landing distance.

5. Pilot Procedures — Computing Balanced Field Takeoff Distances

6. Pilot Procedures — Computing Landing Distances

6.a. Computing Distances With Manufacturer Provided Contaminated Runway Charts

Even if your aircraft manufacturer provides landing performance charts that consider contaminated runways, you should also consider the following:

  • The methods and procedures used to measure runway contamination are not consistent, have not been demonstrated to reliably translate to actual stopping distances, and more often than not are subjective.
  • The performance numbers provided by the manufacturer are designed to produce minimum distances using techniques that line pilots may not be able to reproduce: high descent angles, high rates of descent at touchdown, immediate application of drag devices, full braking until the aircraft is completely stopped.
  • The performance numbers provided by the manufacturer might not include any safety margin at all. The FAA considers 15% to be the minimum acceptable safety margin.

With these considerations in mind, I recommend the following:

  • Pilots should strive to land their aircraft in a consistent manner to achieve touchdown in the distance recommended by the aircraft manufacturer. Be advised that the touchdown rate will probably be higher than most passengers will deem a "good landing," but they should be taught that a good landing is not a soft landing, a good landing is on speed and in the touchdown zone.
  • Pilots should compute landing distances based on available braking action reports. If their aircraft manufacturer charts do not provide the 15% safety margin, they should add 15% on their own. This assessment should be made using the most recent data and as close to actual landing time as possible. Typically an assessment can be made just prior to top of descent.
  • If the charted distance with the safety factor exceeds the runway available, another airport or runway should be selected and the landing distance assessment should be repeated.
  • If the charted distance with the safety factor says the landing can be made but the runway is contaminated and the numbers are close enough to cause any doubt, the assessment should be repeated using the Canadian Runway Friction Index, as follows.

6.b. Computing Landing Distances Without Manufacturer Provided Contaminated Runway Charts

Canadian Runway Friction Index (CRFI) — Another Source of Advisory Data

What are you to do if your aircraft manufacturer leaves you without the proper charts for contaminated runways or the airport has nothing better than braking action reports? You should make a "no go" decision based on the regulatory guidelines and the airplane flight manual; if they say you should divert, you should. But what if nothing "by the book" says you can't takeoff or land but you still have your doubts? You might consider applying the techniques offered in the Transport Canada Aeronautical Information Manual, ¶1.6.6, CRFI Application to Aircraft Performance. If the CRFI verifies your "go" decision, you can proceed with added confidence. If the CRFI says "no go" but the AFM says "go," you should think long and hard before pressing on. But how do you apply the CRFI?

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Figure: Runway Surface Condition Equivalent, from G450-OIS-02, Table 6a.

A. Convert Subjective Rating to CRFI.

Gulfstream offers the conversion chart for some of the aircraft, the G450 as an example. Your aircraft manufacturer may do the same. In any case, however, this is considered advisory only.

  • You first convert the Runway Surface Condition (RSC) to the Canadian Runway Friction Index (CRFI) using Table 6a:
  • Remember that anything over 0.125 inches is contaminated.
  • Where you have a range of numbers, 0.30 to 0.60 on wet asphalt for example, you should note both numbers because the high and low could result in "go" and "no go" decisions.

B. Determine Landing Distance from Aircraft Flight Manuals. Consult your AFM for a landing distance on a dry runway.

Be careful to select an unfactored distance. That is, the actual landing distance that reflects AFM procedures over the runway threshold, touchdown, and braking.

C. Determine a CRFI Recommended Landing Distance (Without Reverse Thrust)

Enter the appropriate chart (with or without reverse thrust or propeller discing) with the unfactored, dry distance and the CRFI. The result, read below the CRFI, will be the recommended landing distance.

[Transport Canada Aeronautical Information Manual, ¶1.6.6.]

  • The information contained in Tables 1 and 2 has been compiled and is considered to be the best data available at this time because it is based upon extensive field test performance data of aircraft braking on winter-contaminated surfaces. The information should provide a useful guide to pilots when estimating aircraft performance under adverse runway conditions. The onus for the production of information, guidance or advice on the operation of aircraft on a wet and/or contaminated runway rests with the aircraft manufacturer. The information published in the TC AIM does not change, create any additional, authorize changes in, or permit deviations from regulatory requirements. These Tables are intended to be used at the pilot's discretion.
  • Landing distances recommended in Table 1 are intended to be used for aeroplanes with no discing and/or reverse thrust capability and are based on statistical variation measured during actual flight tests.
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CRFI Recommended landing distances (no discing/reverse thrust), from Transport Canada Aeronautical Information Manual, ¶1.6.6., table 1.

[Transport Canada Aeronautical Information Manual, ¶1.6.6.]

  1. The recommended landing distances in Table 1 are based on a 95 percent level of confidence. A 95 percent level of confidence means that in more than 19 landings out of 20, the stated distance in Table 1 will be conservative for properly executed landings with all systems serviceable on runway surfaces with the reported CRFI.
  2. Table 1 will also be conservative for turbojet- and turboprop- powered aeroplanes with reverse thrust, and additionally, in the case of turboprop-powered aeroplanes, with the effect obtained from discing.
  3. The recommended landing distances in CRFI Table 1 are based on standard pilot techniques for the minimum distance landings from 50 ft, including a stabilized approach at VRef using a glide slope of 3° to 50 ft or lower, a firm touchdown, minimum delay to nose lowering, minimum delay time to deployment of ground lift dump devices and application of brakes, and sustained maximum antiskid braking until stopped.
  4. Landing field length is the landing distance divided by 0.6 (turbojets) or 0.7 (turboprops). If the aircraft flight manual (AFM) expresses landing performance in terms of landing distance, enter the Table from the left-hand column. However, if the AFM expresses landing performance in terms of landing field length, enter the Table from one of the right-hand columns, after first verifying which factor has been used in the AFM.

D. Determine a CRFI Recommended Landing Distance (With Reverse Thrust)

[Transport Canada Aeronautical Information Manual, ¶1.6.6.]

  • The information contained in Tables 1 and 2 has been compiled and is considered to be the best data available at this time because it is based upon extensive field test performance data of aircraft braking on winter-contaminated surfaces. The information should provide a useful guide to pilots when estimating aircraft performance under adverse runway conditions. The onus for the production of information, guidance or advice on the operation of aircraft on a wet and/or contaminated runway rests with the aircraft manufacturer. The information published in the TC AIM does not change, create any additional, authorize changes in, or permit deviations from regulatory requirements. These Tables are intended to be used at the pilot's discretion.
  • Table 2 may be used for aeroplanes with discing and/or reverse thrust capability and is based on the landing distances recommended in Table 1 with additional calculations that give credit for discing and/or reverse thrust. In calculating the distances in Table 2, the air distance from the screen height of 50 ft to touchdown and the delay distance from touchdown to the application of full braking remain unchanged from Table 1. The effects of discing and/or reverse thrust were used only to reduce the stopping distance from the application of full braking to a complete stop.
  • The recommended landing distances stated in Table 2 take into account the reduction in landing distances obtained with the use of discing and/or reverse thrust capability for a turboprop- powered aeroplane and with the use of reverse thrust for a turbojet-powered aeroplane. Representative low values of discing and/or reverse thrust effect have been assumed and, therefore, the data may be conservative for properly executed landings by some aeroplanes with highly effective discing and/or thrust reversing systems.
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CRFI Recommended landing distances (discing/reverse thrust), from Transport Canada Aeronautical Information Manual, ¶1.6.6., table 2.

[Transport Canada Aeronautical Information Manual, ¶1.6.6.]

  1. The recommended landing distances in Table 2 are based 3. on a 95 percent level of confidence. A 95 percent level of confidence means that in more than 19 landings out of 20, the stated distance in Table 2 will be conservative for properly executed landings with all systems serviceable on runway surfaces with the reported CRFI.
  2. The recommended landing distances in Table 2 take into account the reduction in landing distances obtained with the use of discing and/or reverse thrust capability for a turboprop-powered aeroplane and with the use of reverse thrust for a turbojet-powered aeroplane. Table 2 is based on the landing distances recommended in Table 1 with additional calculations that give credit for discing and/or reverse thrust. Representative low values of discing and/or reverse thrust effect have been assumed, hence the 4. data will be conservative for properly executed landings by some aeroplanes with highly effective discing and/or thrust reversing systems.
  3. The recommended landing distances in CRFI Table 2 are based on standard pilot techniques for the minimum distance landings from 50 ft, including a stabilized approach at VRef using a glide slope of 3° to 50 ft or lower, a firm touchdown, minimum delay to nose lowering, minimum delay time to deployment of ground lift dump devices and application of brakes and discing and/or reverse thrust, and sustained maximum antiskid braking until stopped. In Table 2, the air distance from the screen height of 50 ft to touchdown and the delay distance from touchdown to the application of full braking remain unchanged from Table 1. The effects of discing/reverse thrust were used only to reduce the stopping distance from the application of full braking to a complete stop.
  4. Landing field length is the landing distance divided by 0.6 (turbojets) or 0.7 (turboprops). If the AFM expresses landing performance in terms of landing distance, enter the Table from the left-hand column. However, if the AFM expresses landing performance in terms of landing field length, enter the Table from one of the right-hand columns, after first verifying which factor has been used in the AFM.

6.c. Computing Takeoff Distances

Very little is written on the problem of computing takeoff distances on contaminated runways. Since we are able to begin our takeoff roll more consistently than the landing roll, perhaps it isn't as much an issue. Nonetheless, a rejected takeoff at V1 on a balanced field will require the pilot do everything right the first time. Pilots should practice this in the simulator and evaluate their own performances. Then, realizing the same problems with braking action reports will exist on takeoff, they should use at least a 15% safety factor for their balanced field computations. Note this is not a part of SAFO 06012. It is just me, Eddie, saying what I do.

7. Pilot Procedures — Dealing with Crosswinds

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Table: Crosswind Limits for CRFI, from Transport Canada Aeronautical Information Manual, ¶1.6.6., Table 3.

[Transport Canada Aeronautical Information Manual, ¶1.6.6.] This chart provides information for calculating headwind and crosswind components. The vertical lines indicate the recommended maximum crosswind component for reported CRFI.

Many aircraft are silent on the subject of crosswind limits. In fact, some aircraft only publish a demonstrated crosswind limit number for dry runways. The CRFI crosswind chart offers an idea of what Transport Canada has determined for recommended limits.

Remember the 0.30 to 0.60 CRFI range for a wet asphalt runway? The recommended limit is between 10 and 35 knots.

Bombardier Example

[Bombardier BD-700 Airplane Flight Manual, §07-31-01-2, ¶2.A.(7)]

  • The maximum crosswind component for take−off and landing on a contaminated runway is 10 knots (5 meters/sec).
  • Operation on runways contaminated with ice is prohibited.

8. Pilot Procedures — Avoiding Hydroplaning

[Transport Canada Aeronautical Information Manual, ¶1.6.5

  • Hydroplaning is a function of the water depth, tire pressure and speed. Moreover, the minimum speed at which a non-rotating tire will begin to hydroplane is lower than the speed at which a rotating tire will begin to hydroplane because a build up of water under the non-rotating tire increases the hydroplaning effect. Pilots should therefore be aware of this since it will result in a substantial difference between the take-off and landing roll aircraft performance under the same runway conditions. The minimum speed, in knots, at which hydroplaning will commence can be calculated by multiplying the square root of the tire pressure (PSI) by 7.7 for a non-rotating tire, or by 9 for a rotating tire.
  • Gently "kissing" the runway with the tire increases the chances it will not be rotating when it finally makes rubber-to-runway contact and therefore increasing the likelihood of hydroplaning.

  • This equation gives an approximation of the minimum speed necessary to hydroplane on a smooth, wet surface with tires that are bald or have no tread. For example, the minimum hydroplaning speeds for an aircraft with tires inflated to 49 PSI are calculated as:
  • Non-rotating tire:7.7 X √49 = 54 kt; or Rotating tire: 9 X √49 = 63 kt

    These are good numbers to know for each aircraft you fly. For example, a typical Gulfstream's main gear tire pressures will be around 190 psi. That means you can expect to begin hydroplaning around 125 knots and will not regain friction until 106 knots. The nose gear is typically about 135 psi, which means directional control via the nose wheel can be suspect around 105 knots.

  • When hydroplaning occurs, the aircraft's tires are completely separated from the actual runway surface by a thin water film and they will continue to hydroplane until a reduction in speed permits the tires to regain contact with the runway. This speed will be considerably lower than the speed at which hydroplaning commences. Under these conditions, the tire traction drops to almost negligible values, and in some cases, the wheel will stop rotating entirely. The tires will provide no braking capability and will not contribute to the directional control of the aircraft. The resultant increase in stopping distance is impossible to predict accurately, but it has been estimated to increase as much as 700 percent. Further, it is known that a 10-kt crosswind will drift an aircraft off the side of a 200-ft wide runway in approximately 7 sec under hydroplaning conditions.

9. Pilot Procedures — The Flare

[AC 91-79, appendix 1, ¶6.]

  1. The flare reduces the approach rate of descent to a more acceptable rate for touchdown. If the flare is extended while additional speed is bled off, hundreds or even thousands of feet of runway may be used up. An extended flare may also result in an increase in pitch attitude which may lead to a tail strike A firm landing does not mean a hard landing, but rather a deliberate or positive touchdown at the desired touchdown point. A landing executed solely for passenger comfort considerations, which terminates beyond the TDZ, is not impressive, desirable, or consistent with safety or regulations. It is essential to fly the aircraft onto the runway at the target touchdown point consistent with the operator's SOP. See Figure 2 as an example of the results of an extended flare.
  2. A proper approach and flare positions the airplane to touchdown at the target touchdown point consistent with the operator's SOP. Once the main wheels have contacted the runway, the pilot must maintain directional control and initiate the stopping process. The runway distance available to stop is longest if the touchdown was on target. Once the aircraft is on the ground, ground spoilers, wheel brakes, and reversers, as applicable, are much more effective in slowing the aircraft than the aerodynamic drag produced in the flare maneuver.

Bombardier Example

[Bombardier BD-700 Airplane Flight Manual, §04-08-16, ¶12] FULL STOP LANDING — Perform partial flare, and touchdown without holding off.

Gulfstream Example

[G450 Aircraft Operating Manual §13-03-20] Landing distances based on 3.0° glide path at 50 feet and 6 FPS sink rate at touchdown.

10. Pilot Procedures — Braking

[AC 91-79, appendix 1, ¶6.]

  1. There are two primary forces available for deceleration during the rollout process: wheel braking, and reverse thrust/propeller reversing, if available. The deployment of ground spoilers, if installed, immediately upon touchdown on the runway has the effect of dumping the lift generated by the wings and placing the aircraft's weight on the wheels, which enhances the effects of wheel braking after touchdown. Deployment of drag devices such as ground spoilers and the selection of thrust reverse or propeller reversing are most effective at higher speeds and are not affected by runway surface conditions. Their application immediately after touchdown provides the greatest benefit.
  2. (1)When the runway is wet or slippery, reverse thrust may be the dominant deceleration force just after touchdown. As the aircraft slows down, the wheel brakes become more effective and provide most of the stopping force during the landing rollout. When the runway length is limited, the wheel brakes should be applied fully and immediately after touchdown, and they should not be released until the aircraft slows to a safe taxi speed for the conditions. If the airplane is equipped with autobrakes, manufacturers recommend the use of the autobrakes for all landings on contaminated runways. Generally, autobrakes are applied earlier in the landing roll and with more application pressure than pilot deployed manual brakes. The landing rollout distance will depend on the touchdown speed, the forces applied, and on the timely application of the stopping forces. A firm touchdown at the target touchdown point, followed by the deployment of ground spoilers, the timely selection of thrust reverse (if installed), and the smooth application of max braking will result in the shortest landing distance ground roll, particularly on wet or contaminated runway surfaces. Braking systems and braking procedures vary by airplane make and model. Therefore, adhere to the procedures contained in the AFM for the specific airplane being operated.

    (2) The nose wheel should be lowered onto the runway immediately after touchdown. Placing the nose wheel on the runway will assist in maintaining directional control. It also decreases the wing angle of attack, thereby decreasing lift and placing more load onto the tires, which increases tire-to-ground friction.

    (3) As previously discussed, ground spoilers, if installed, should be deployed immediately after touchdown because they are most effective at high speed. Timely deployment of spoilers will increase drag by 50 to 60 percent, but more importantly, deployment of the spoilers increases wheel loading by as much as 200 percent in the landing flap configuration. This increases the tire-to-ground friction force making the maximum tire braking forces available. Many aircraft with auto-spoilers installed require weight-on-wheels to deploy the spoilers, which reinforces the requirement for a positive touchdown.

    (4) Thrust reversers, if installed, are also most effective at high speeds and should be deployed as soon as possible after touchdown. However, the pilot should not command significant reverse thrust until the nosewheel is on the ground. In the event of an asymmetric deployment, the nosewheel on the ground will aid in directional control. If the thrust reversers deploy asymmetrically, or if the aircraft begins to drift due to a crosswind, close the thrust reversers, and reestablish directional control utilizing the rudder. Once the aircraft track down the runway is reestablished, redeploy the thrust reversers. Use aircraft steering in accordance with the AFM procedures. The pilot should begin braking as soon as possible after touchdown and wheel spin-up. Maximum brake pressure should be applied, without skidding the tires, until the aircraft reaches a safe taxi speed or comes to a full stop.

    (5) Application of brakes is different for aircraft equipped with a functioning anti-skid braking system than for airplanes without such a system.

    (a) Without Antiskid. Brakes should be applied firmly throughout the deceleration process, and the pilot must recognize the point that wheel skid occurs. Maximum braking effectiveness occurs just prior to the point where wheel skidding occurs. Should a skid occur, releasing brake pressure can stop skidding and effective braking can be reestablished by reapplying brake pressure firmly until the deceleration process has been completed.

    (b) With Antiskid. Brakes should be applied firmly throughout the deceleration process. When maximum braking is required, it is accomplished by holding maximum brake application pressure and allowing the anti-skid system to operate. Letting up on the brakes (unless required to regain directional control) defeats the purpose of the anti-skid system. The pulsation caused by the modulation of the brake pressure by the anti-skid system indicates that the anti-skid system is operating normally although the pulsation may be disconcerting to the pilot. Releasing the pedal application when the anti-skid begins to work and alternately applying, releasing and reapplying brake pressure does not enhance braking effectiveness. Pilots should avoid this type of braking technique.

11. Pilot Procedures — Reverse Thrust

Bombardier Example

[Bombardier BD-700 Airplane Flight Manual, §06-01-1, ¶1.A.(7)] The take-off field length data on wet runways are based on both thrust reversers operable and assumes that maximum available reverse thrust is used down to a complete stop.

[Bombardier BD-700 Airplane Flight Manual, §06-01-1, ¶1.A.(7)] ACTUAL LANDING DISTANCE ON CONTAMINATED RUNWAYS — The following charts are used to obtain the actual landing distance on contaminated runways, for a slat OUT / flap 30° landing, for a given value of airplane weight, airport pressure altitude, reported wind, landing approach speed (VREF) increment and number of operable thrust reversers.

Gulfstream Example

[Gulfstream G450 Airplane Flight Manual, §05-02-10, ¶1] No reverse thrust credit was taken for accelerate-stop distances computed for dry runways; however, the use of reverse thrust is recommended to reduce the braking distance and the kinetic energy absorbed by the brakes. Wet runway accelerate-stop distances are calculated assuming the deployment of one or both thrust reversers.

[Gulfstream G450 Airplane Flight Manual, §05-11-20, ¶3.B.(3)] Deploy thrust reversers as required. Note that reverse thrust credit is not shown in the landing distance charts, but the use of reverse thrust will result in distances less than those computed and significantly improve brake wear characteristics.

12. Aircraft Manufacturer Approaches to Runway Contamination

You can learn something from how other aircraft operate when making your contaminated runway decisions:

  • Bombardier BD-700-1A10
    • Tightly defines contaminated runways to a higher degree of specificity than the EU standard
    • Has fairly comprehensive performance data for contaminated runways
    • Performance charts assume the runway is either completely contaminated or not, there are no braking action, μ numbers, runway condition numbers, or contaminant depths to consider
    • Does not include SAFO 06012 safety margin (15%) in landing distances
    • Specifies a single number crosswind limit on contaminated runways
    • Does not specify a touchdown rate other than "partial flare"
    • Takes thrust reverser credit for takeoff on wet runways and for landing on contaminated runways
  • Gulfstream G450
    • Defines contaminated runways closely with EU standard
    • Has fairly comprehensive performance data for contaminated runways
    • Performance charts include conversions for braking action, runway condition numbers, and contaminant depths, as well as CFRI recommendations
    • Includes SAFO 06012 safety margin (15%) in most landing distances
    • Recommends using CRFI charts for crosswind limits on contaminated runways
    • Specifies a touchdown rate of 6 FPS (360 fpm)
    • Takes thrust reverser credit for takeoff on wet runways and for landing on contaminated runways

    References

    14 CFR 91, Title 14: Aeronautics and Space, General Operating and Flight Rules, Federal Aviation Administration, Department of Transportation

    14 CFR 121, Title 14: Aeronautics and Space, Operating Requirements: Domestic, Flag, and Supplemental Operations, Federal Aviation Administration, Department of Transportation

    14 CFR 135, Title 14: Aeronautics and Space, Operating Requirements: Commuter and On Demand Operations and Rules Governing Persons on Board Such Aircraft, Federal Aviation Administration, Department of Transportation

    Advisory Circular 91-79, Runway Overrrun Prevention, 11/06/07, U.S. Department of Transportation

    Aeronautical Information Manual

    Bombardier BD-700-1A10 Airplane Flight Manual, Publication No. CSP 700-1A, Revision 80, Jun 03, 2014

    European Union Regulation No 859/2008, Technical requirements and administrative procedures applicable to commercial transportation by aeroplane, 20 August 2008

    FAA Air Traffic Organization Policy, Flight Services, Order JO 7110.10W, March 7, 2013

    Gulfstream G450 Operational Information Supplement, G450-OIS-02, Contaminated Runway Performance, Revision 1, August 3, 2011

    Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013

    ICAO Annex 6 - Operation of Aircraft - Part 1 Commercial Aircraft, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part I, July 2010

    ICAO Annex 15 - Aeronautical Information Services, International Standards and Recommended Practices, Annex 15 to the Convention on International Civil Aviation, July 2010

    Joint Aviation Authorities JAR-OPS 1, Commercial Air Transportation (Aeroplanes), 10 May 2007

    NTSB Aircraft Accident Report, AAR-07/06, Runway Overrun and Collision, Southwest Airlines Flight 1248, Boeing 737-7H4, N471WN, Chicago Midway International Airport, Chicago, Illinois, December 8, 2005

    Safety Alert for Operators, SAFO 06012, Landing Performance Assessments at Time of Arrival (Turbojets), 8/31/06, U.S. Department of Transportation

    Transport Canada Aeronautical Information Manual

    Revision: 20131027
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