Appendix 1 TABLE 1-1. OPERATIONAL RUNWAY CONDITION ASSESSMENT
MATRIX (RCAM) BRAKING ACTION CODES AND DEFINITIONS Airport Operator Assessment Criteria Control/Braking Assessment Criteria Runway Condition Description Code Deceleration or Directional Control Observation Pilot Reported Braking Action
• Dry 6 --- ---
• Frost
• Wet (Includes damp and less than 1/8 inch depth of water) Less than 1/8 inch (3mm) depth of:
• Slush
• Dry Snow
• Wet Snow 5 Braking deceleration is normal for the wheel braking effort applied AND directional control is normal.
Good -15ºC and Colder outside air temperature:
• Compacted Snow 4 Braking deceleration OR directional control is between Good and Medium.
Good to Medium
• Slippery When Wet (wet runway)
• Dry Snow or Wet Snow (any depth) over Compacted Snow 1/8 inch depth or greater of:
• Dry Snow
• Wet Snow Warmer than -15ºC outside air temperature:
• Compacted Snow 3 Braking deceleration is noticeably reduced for the wheel braking effort applied OR directional control is noticeably reduced.
Medium 1/8 inch depth or greater of:
• Water
• Slush 2 Braking deceleration OR directional control is between Medium and Poor.
Medium to Poor
• Ice 1 Braking deceleration is significantly reduced for the wheel braking effort applied OR directional control is significantly reduced.
Poor
• Wet Ice
• Water on top of Compacted Snow
• Dry Snow or Wet Snow over Ice 0 Braking deceleration is minimal to non-existent for the wheel braking effort applied OR directional control is uncertain.
Nil Operational RCAM Version 2014.1 Note: The unshaded portion of the RCAM is associated with how an airport operator conducts a runway condition assessment.
Note: The shaded portion of the RCAM is associated with the pilot’s experience with braking action.
Note: The Operational RCAM illustration will differ from the RCAM illustration used by Airport Operators.
Note: Runway condition codes, one for each third of the landing surface, for example 4/3/3, represent the runway condition description as reported by the airport operator. The reporting of codes by runway thirds is expected to begin in October of 2016.
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e. Aiming Point. The aiming point is the point on the ground at which, if the airplane maintains a constant glidepath and does not execute the round out (flare) maneuver for landing, it would touch the ground.
f. Maximum Braking Effort. Maximum braking effort is defined as maximum brake application by the pilot.
g. Adjusted Landing Distance. Is the actual landing distance adjusted for a landing safety margin in accordance with the operator’s standard operating procedures (SOP). This should not be confused with the landing distance associated with the dispatch requirements.
h. Target Touchdown Point. As discussed in the current edition of FAA-H-8083-3, Airplane Flying Handbook, the target touchdown point is defined as a touchdown point approximately 1,000 feet (ft) down the runway. Additionally, the operator may define the desired target touchdown point in their SOP.
i. Touchdown Zone (TDZ). As referenced in the current edition of Airline Transport Pilot (ATP) Practical Test Standards (PTS) FAA-S-8081-5, Airline Transport Pilot and Aircraft Type Rating Practical Test Standards for Airplane, the TDZ is referred to as a point 500-3,000 ft beyond the runway threshold not to exceed the first one-third of the runway. This reference is not used in landing distance performance calculations.
j. Unfactored or Certified Landing Distance. The landing distance determined during certification as required by 14 CFR part 23, § 23.75 and 14 CFR part 25, § 25.125. The unfactored landing distance is not adjusted for any safety margin additives. The unfactored certified landing distance may be different from the actual landing distance because not all factors affecting landing distance are required to be accounted for by certification regulations.
For example, the unfactored certified landing distances are based on a dry, level (zero slope) runway at standard day temperatures, and do not normally take into account the use of autobrakes, autoland systems, HGS, or thrust reversers. This is considered the baseline landing distance from which all subsequent user calculations emanate.
k. Factored Landing Distance. For applicable operations, the dispatch landing distance allows the airplane to land and stop within 60 percent of the available runway when the runway is dry. The factored landing distance is the certified landing distance multiplied by 1.67, which can then be compared directly to the available landing distance. When the runway is wet, the certified distance is multiplied by 1.97 to account for the 15 percent additional runway requirement.
3. STABILIZED APPROACH TO THE TOUCHDOWN AIM POINT. A stabilized approach is the safest profile, and it is one of the most critical elements to ensure a safe approach to a landing operation.
Appendix 1 FIGURE 1-1. STABILIZED APPROACH
NOTE: The approach descent rate will vary given the airplane’s ground speed as a result of the required approach speed per Airplane Flight Manual (AFM), weight, and wind additives.
a. Landing Configuration. The airplane should be in the landing configuration early in the approach. The landing gear should be down, landing flaps selected, trim set, and fuel balanced per the AFM or pilot’s operating handbook (POH). Landing checklist items should be completed. Ensuring that these tasks are completed will help keep the number of variables to a minimum during the final approach.
b. Stabilized on Profile. The airplane should be stabilized on profile before descending through the 1,000-ft window or through the 500 ft above TDZ elevation (TDZE) window in visual meteorological conditions (VMC). Configuration, trim, speed, and glidepath should be at or near the optimum parameters early in the approach to avoid distractions and conflicts as the airplane nears the threshold window. The electronic or visual glidepath or an optimum glidepath angle of 3 degrees should be established and maintained. For the purposes of this AC, approaches that require a glidepath angle greater than 3 degrees are a “special case.” The airplane must be in the proper landing configuration, on the correct lateral track, the correct vertical track and at the proper airspeed. It should be noted, as it applies to stabilized approaches, that following lateral and vertical tracks should require only normal bracketing corrections.
NOTE: An approach that requires abnormal bracketing does not meet the stabilized approach concept, and a go-around should be initiated.
c. Descent Rate. The optimum descent rate for a 3 degree approach path is based upon the airplane’s ground speed. A pilot must exercise discipline and situational awareness to maintain the airplane’s target approach speed. The following is a method to estimate the appropriate Page 5
Appendix 1 descent rate for a 3 degree descent path: Multiplying the ground speed in knots (kts) by 5 provides a usable target 3 degree descent rate in ft per minute. Combined with disciplined airspeed control, slight adjustments in the rate of descent to maintain the glidepath will ensure flying the descent/instrument landing system (ILS) glidepath. For example, see Table 1-2, Rates of Descent Estimate Concept for a Three-Degree Glidepath vs. Ground Speed, and refer to the ILS approach chart.
TABLE 1-2. RATES OF DESCENT ESTIMATE CONCEPT FOR THREE-DEGREE GLIDEPATH VS. GROUND SPEED Ground speed kts 70 90 100 120 140 160 Published 30 GS fpm 372 478 531 637 743 849 5×GS estimated fpm 350 450 500 600 700 800
d. Indicated Airspeed. Indicated airspeed should be not more than VREF + 5 or the POH published approach airspeed, with appropriate adjustments for wind or other factors, and never less than VREF or the appropriate airspeed in order to avoid the loss of aircraft control. There is a strong relationship between trim, speed, and power, and it is important to stabilize the speed in order to minimize those variables.
e. Turbojet Engine Speed. The engine speed should be at a setting that allows best response when and if a rapid power increase is needed. The stabilized approach parameters should be confirmed at 500 ft (VMC) or 1,000 ft instrument meteorological conditions (IMC) above airport TDZE. This is approximately 1-2 minutes from touchdown. If the approach is not stabilized at that altitude, a go-around/balked landing should be executed.
f. Touchdown Point. Extended flare and runway slope are two factors that affect pilot control of the touchdown point. Turbine airplanes should be flown onto the runway rather than being held off the surface as speed dissipates. A firm landing is both normal and desirable. The typical operational touchdown point is in the first third of the runway, and it may be farther down the runway than the 1,000 ft point. This additional distance should be accounted for in the landing distance assessment at time of arrival (TOA).
g. Downhill Runway Slope. Additionally, a negative runway slope affects the touchdown point. According to the Flight Safety Foundation (FSF) Approach and Landing Accident Reduction (ALAR) Briefing Note 8.3—Landing Distances, each 1 percent of runway down slope increases the landing distance by 10 percent. Depending upon the airplane’s manufacturer, runway slope may be included in the AFM/POH landing performance data.
Appendix 1 TABLE 1-3. SAMPLE COMPUTATION: RUNWAY LENGTH 7,000 FT
NOTE: When computing runway gradient, every 1.0 percent grade equals approximately 10 percent change in effective runway length. Also, for shorter runways, it does not take as large an elevation difference between runway ends to result in a 3 percent gradient. For example: for a 3 percent gradient for a 3,000-ft runway, the elevation difference between the runway ends would only be 90 ft.
h. Factors that Contribute to an Unstabilized Approach.
(1) An ATC clearance that requests an airspeed in excess of those airspeeds normally flown in the terminal area, and/or clearances that require an airplane to remain at altitude to a point where intercepting the normal glidepath is difficult to achieve, pilots should be aware that if they cannot achieve a stabilized approach profile, to advise ATC.
NOTE: A stabilized approach to landing is key to mitigating the risk of a runway overrun. If the pilot determines that a stabilized approach cannot be flown, the approach should not be accepted and a go-around should be initiated.
(2) It is paramount that the airplane arrives at the approach threshold window on speed. If the pilot has planned to carry additional airspeed beyond the threshold due to gusty surface wind conditions, then the effect of this additional airspeed/ground speed should be included in the actual landing distance. A balked landing maneuver should be executed if the airplane does not cross the runway threshold at the planned airspeed.
NOTE: A 10 percent excess landing speed causes at least a 21 percent increase in landing distance. The excess speed places a greater working load on the brakes because of the additional kinetic energy to be dissipated. Also, the additional speed causes increased drag and lift in the normal ground attitude, and the increased lift reduces the normal force on the braking surfaces. The deceleration may suffer during this range of speed immediately after touchdown, and it is more probable for a tire to be blown out from braking at this point.
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4. DISCUSSION OF LANDING DATA.
a. Landing Performance Assessment. Landing performance assessment is influenced by a multitude of variables. Airplane weight and configuration, use of deceleration devices, airport elevation, atmospheric temperature, wind, runway length, runway slope, and runway surface condition (i.e., dry, wet, contaminated, improved, unimproved, grass, etc.) are all factors in determining landing performance. The condition of airplane tires, brakes, and systems installed/operative/inoperative (e.g., antiskid braking, propeller reversing, thrust reversers, etc.), and pilot abilities/technique all have a direct impact on the airplane’s ability to come to a full stop after touchdown. However, there is no one standard format in which airplane manufacturers are required to provide this additional data. The pilot must be aware of the airplane’s landing data/performance. The pilot must also obtain the most current runway condition information within a reasonable time before initiating the approach phase of flight in order to assess the airplane operational landing distance to ensure that it does not exceed the landing distance available. To begin the assessment process of landing performance, we need to first address some basic principles of landing performance.
b. Data Provided. The data provided in the AFM/POH may only provide unfactored landing data, which does not reflect operational landing distances. The AFM landing data for most large airplanes operated in accordance with 14 CFR part 121 provide factored landing distances. Some manufacturers provide advisory or supplemental performance data in the AFM/POH which may account for conditions such as a dry runway, a wet runway, ground spoilers operative/inoperative, thrust reversers operative/inoperative, antiskid operative/inoperative, propeller reverse, tailwind, and/or headwind. Also, it is very important to understand that the factors that affect the stopping ability of an airplane are cumulative.
c. AFM Performance Section. The following includes general examples of aircraft performance factors required for certification, and inclusion in the airplane’s AFM. Landing performance is of primary interest in operating an airplane because it is a factor in defining the runway length requirements. In addition to the importance of proper piloting technique, any factor that affects the landing velocity or deceleration during the landing roll will affect landing distance.
(1) Factors Required to be Included in the Performance Charts:
• Pressure altitude,
• Standard Temperature,
• Gross weight,
• Wind, and
• Airplane configuration.
(2) For Small Airplanes Operation on Unpaved Runway Information. For airplanes less than 6,000 pounds (2730 kg) maximum weight, the factors given below may be quoted in the flight manual as an alternative to the scheduling of data derived from testing or calculation. It should be noted that these factors are intended to cover the range of airplane types in this category and are necessarily conservative (refer to the current edition of AC 23-8, Flight Test Guide for Certification of Part 23 Airplanes).
Appendix 1 TABLE 1-4. SMOOTH, FLAT RUNWAY Takeoff Landing Dry Grass 1.2 1.2 Wet Grass 1.3 1.6 NOTE: If the runway is not smooth, the grass is very long or very short, higher factors may be warranted. Very short grass = golf course length. Very long grass = un-mowed field or high interstate highway median grass length.
(3) Landing Distances for Large Transport Airplanes. Landing distances for large transport airplanes determined during certification tests are aimed at demonstrating the shortest performance distances for a given airplane weight with a test pilot at the controls. In addition, they are established with full awareness that operational rules for normal operations require the addition of factors to determine minimum operational field lengths. Therefore, the landing distances determined for large airplanes, under § 25.125, are much shorter than the landing distances achieved in normal operations. For small airplanes, under § 23.75 (reference AC 23-8), prescribes the requirements to certify a small airplane landing performance, though the factors of weight, speed, and pressure altitude are considered, the factors that extend the landing distance are not included. Therefore, given the factors that increase the airplane’s required landing distance, the pilot/operator should seriously consider the consequence of not assessing the landing distance required.
(4) Air Carriers and 14 CFR Part 91K Operators. To mitigate the risk of a runway overrun, air carriers and part 91K operators are required by regulation to multiply the airplane’s actual landing distance by a specified factor associated with a destination or alternate airport. All operations must mitigate the risk of a runway overrun by considering all the elements that affect the unfactored landing distance provided in the AFM/POH. This is to ensure that at the time arrival, the landing distance required will not exceed the landing distance available. (For the purpose of example, refer to the applicable part 91K, § 91.1037; part 121, § 121.195; and 14 CFR part 135, § 135.385 for more information.)
NOTE: Notwithstanding that non-air carriers/operators are not required by regulation to use a factored landing distance, they are strongly encouraged to adopt a factored landing distance methodology to mitigate the risk of a runway overrun.
d. Minimum Landing Distance Prediction. In the prediction of minimum landing distance from the AFM/POH data, the following should be addressed (see paragraph 4 above and the sample cumulative landing distance worksheet in Appendix 3 for more information):
• High airport elevation or high density altitude, resulting in increased groundspeed;
• Landing weight;
• Excess airspeed over the runway threshold;
• Landing beyond the intended touchdown point;
• Runway slope;
Appendix 1
• Excessive height over the runway threshold;
• Delayed use of deceleration devices;
• Tailwind landing; and
• A wet or contaminated runway.
e. The Effect of Wind on Landing Performance. Figure 1-2, Effect of Wind on Landing Performance, illustrates the general effect of wind by showing the percent change in takeoff or landing distance as a function of the ratio of wind velocity to takeoff or landing speed. For example, a tailwind velocity that is 10 percent of the landing airspeed produces a general effect of a 21 percent increase in the landing distance. (Refer to the current editing of the Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25, Aircraft Performance.)
NOTE: If the wind direction is variable (VRB) and a range is given, the value that provides to most negative condition must be used in performance calculations. If no range is given, the full value of the wind velocity must be considered a tailwind, since the possibility of this exists on landing.
FIGURE 1-2. EFFECT OF WIND ON LANDING PERFORMANCE
Appendix 1 FIGURE 1-3. BASIC LANDING DISTANCE CHART Conditions Flaps lowered to 40° Power off LANDING DISTANCE Hard surface runway Zero wind weight Gross Approach speed AS, MPH Ground roll At sea level & 59 °F Total to clear 50 ft OBS Ground roll At 2,500 ft & 59 °F Total to clea 50 it OBS Ground roll At 5,000 ft & 41 °F Total to clea 50 ft OBS Ground roll At 7,500 ft & 32 °F Total to clear 50 ft OBS 1,600 60 445 1,075 470 1,135 495 1,195 520 1,255 Note FIGURE 1-4. CUMULATIVE TYPE OF LANDING CHART PLOTTING DENSITY
ALTITUDE, LANDING WEIGHT, HEADWIND/TAILWIND, AND OBSTACLE
CLEARANCE 3,500 Associated conditions Weight at 50 feet Speed Power Retarded to maintain 900 feet/on final approach (pounds) KTS MPH Reference 3,000 Flaps Down 2,950 70 80 2,800 68 Landing gear Runway Down Paved, level, dry surface 2,600 65 • 2,500 Approach speed IAS as tabulated 2,400 63 Braking Maximum 2,200 60
• 2,000
• 1,500
• 1,000 500 C -40° -30° -20° -10° 0° 107 20° 30° 40° 50° 2,800 2,600 2,400 2,200 0 10 20 30 • 50 Outside air temperature Weight Wind component Obstacle (pounds) (knots) height (feet) -40° -20° 0° 20° 60° 80° 100° 120°
f. Stabilized Approach. Without the benefit on an AFM/POH performance chart that accounts for the variables this AC is discussing, the concept in Figure 1-1, Stabilized Approach, provides an appreciation of the factors that increase the airplane's landing distance, and it keeps the pilot engaged in landing distance assessment.
(1) Figure 1-2, Effect of Wind on Landing Performance, illustrates the general effect of wind by showing the percent change in takeoff or landing distance as a function of the ratio of wind velocity to takeoff or landing speed.
(2) Figure 1-4, Cumulative Type of Landing Chart Plotting Density Altitude, Landing Weight, Headwind/Tailwind, and Obstacle Clearance, provides the manufacturer's airplane performance data accounting for density altitude, landing weight, wind, and obstacle clearance height. It also illustrates a performance chart which plots the cumulative effect of each condition as the pilot progresses to obtain the landing distance.
Appendix 1
g. Airplane Landing Weight. Calculate the anticipated landing weight by starting with the airplane gross takeoff weight at departure and subtracting the anticipated normal consumption of fuel required to arrive at the destination airport. If the en route fuel burn is less than planned, the airplane will arrive at its destination at a weight heavier than expected. Therefore, relative to the airplane’s actual landing weight, a recalculation of the airplane’s landing performance is essential prior to attempting a landing maneuver to validate the dispatched landing distance available.
h. Extended Flaps. Flaps may be fully extended to give the airplane a lower stalling speed during the approach to landing. This also allows the airplane to land in a shorter distance. The higher lift and drag associated with fully extended flaps produces greater drag permitting a steeper approach. The greater lift permits a lower landing speed to the landing site but imposes handling difficulties in airplanes with very low wing loading (the ratio between the wing area and the weight of the airplane). Winds across the line of flight, known as crosswind, causes the windward side of the airplane to generate more lift and drag, causing the airplane to roll, yaw, and pitch off its intended flight path. As a result, many light airplanes have limits on how strong the crosswind can be while using flaps. Furthermore, once the airplane is on the ground, the flaps may decrease the effectiveness of the brakes since the wing is still generating lift and preventing the entire weight of the airplane from resting on the tires, thus increasing stopping distance, particularly in wet or icy conditions. Thereby, usually the pilot will raise the flaps as soon as possible for airplanes without spoilers to prevent this from occurring under wet or icy conditions, and done with caution. Notwithstanding the possible effect of a full flap landing, achieving the target airspeed over the threshold, and flying the slowest approach speed for the wind conditions, selecting the maximum flap setting approved by the airplane manufacturer will provide the shortest operational landing distance.
i. Threshold Crossing Height and Airspeed. As previously discussed, the correct threshold crossing airspeed is specifically defined. Therefore it is essential to understand the impact of deviations in threshold crossing airspeeds.
j. Critical Condition Combinations. The most critical conditions of landing performance are combinations of:
• High gross weight, high density altitude,
• Wet/contaminated runway,
• Tailwind landing,
• Downhill slope,
• Less than maximum landing flap, and
• Short runway.
NOTE: In all cases, it is necessary to make an accurate prediction of minimum landing distance to compare with the available runway.
5. LANDING AND BRAKING TECHNIQUE. The flare, touchdown, and the braking technique, are also critical factors in completing a successful approach and landing maneuver.
Landing and braking techniques are discussed below from a point at the beginning of the Page 12
Appendix 1 approach flare through a point at which the airplane decelerates to normal taxi speed or has been brought to a full stop.
a. The Flare. 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, additional runway will be used. 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 extends the touchdown point beyond the TDZ, is not impressive, desirable, or consistent with safety or regulations. It is essential to fly the airplane onto the runway at the target touchdown point. See Figure 1-5, Effects of an Extended Flare, as an example of the results of an extended flare.
FIGURE 1-5. EFFECTS OF AN EXTENDED FLARE
b. Touchdown. A proper approach and flare positions the airplane to touch down at the target touchdown point. 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 airplane is on the ground, ground Page 13
Appendix 1 spoilers, wheel brakes, and reversers (depending on airplane equipage) are much more effective in slowing the airplane than the aerodynamic drag produced in the flare maneuver.
NOTE: General aviation airplane technique is to slowly apply backpressure to the yoke to assist braking and to avoid damage to the nose gear or propeller.
c. Braking. A distinction should be made between the procedures for minimum landing distance and an ordinary landing roll with considerable excess runway available. Minimum landing distance will be obtained by creating a continuous peak deceleration of the airplane; that is, extensive use of the brakes for maximum deceleration. On the other hand, an ordinary landing roll with considerable excess runway may allow extensive use of aerodynamic drag to minimize wear and tear on the tires and brakes. If aerodynamic drag is sufficient to cause deceleration, it can be used in deference to the brakes in the early stages of the landing roll. For instance, brakes and tires suffer from continuous hard use, but airplane aerodynamic drag is free and does not wear out with use. The use of aerodynamic drag is applicable only for deceleration to 60 or 70 percent of the touchdown speed. At speeds less than 60 to 70 percent of the touchdown speed, aerodynamic drag is so slight as to be of little use, and braking must be utilized to produce continued deceleration. Since the objective during the landing roll is to decelerate, the powerplant thrust should be the smallest possible positive value (or largest possible negative value in the case of thrust reversers).
NOTE: In addition to proper procedures, many other variables affect the landing performance. Any item that alters the landing speed or deceleration rate during the landing roll will affect the landing distance.
(1) There are three primary forces available for deceleration during the rollout process:
wheel braking, aerodynamic drag, 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 airplane’s weight on the wheels, which enhances the effects of wheel braking after touchdown. Deployment of drag devices are most effective at higher speeds and are not affected by runway surface conditions. In all cases, the pilot must ensure the automatic deployment of the deceleration devices occurs. If not, the pilot must immediately manually employ the devices to minimize the time lost to achieve as close as possible the assessed landing distance.
(2) 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 airplanes with auto-spoilers installed require weight on wheels to deploy the spoilers, which reinforces the requirement for a positive touchdown as a soft touchdown can delay the automatic deployment. Spoiler deployment immediately after touchdown provides the greatest benefit.
(3) When minimum landing distances are considered, braking friction forces predominate during the landing roll and, for the majority of airplane configurations, braking friction is the main source of deceleration when the runway is dry.