Appendix 3
(2) Examples:
Sample Aircraft Type Typical Tire Pressure (psi) Typical VREF (Approach Airspeed, kts) Hydroplane Threshold (Groundspeed, kts) Citation 100 112 86 Challenger 160 125 108 Gulfstream 180 125 115 These examples highlight the elevated risk levels automatically reached by most aircraft as they contact the runway at groundspeeds higher than their calculated hydroplaning speed.
b. Directional Control. The pilot should expect significant degradation in directional controllability on a contaminated runway, depending on the level of available runway friction, especially with an engine shut down or with a crosswind. Some manufacturers provide maximum crosswind values, derived through simulation and calculation, for landing on contaminated runways.
NOTE: Runway surface conditions are rarely consistent over the full length of the runway. Even dry runways will present different friction coefficients due to heavy rubber deposits in the touchdown zone (TDZ) and large paint markings such as the 1,000 ft markers or centerline stripes. The degree of runway surface contamination due to ice, packed snow, or standing water varies along the length of the runway. The pilot will sense changes in the deceleration rate as the airplane transitions from one contaminant condition to another.
12. BRAKE FAILURE VERSUS REDUCED BRAKING. How does the pilot differentiate between reduced braking capability and a brake failure with reduced, and occasionally very low, deceleration rates due to runway contamination? The best answer is for the pilot to be thoroughly familiar with all operating characteristics of the airplane. Experience is the best tool, and until the pilot has the experience, training and knowledge of aircraft performance is the best tool.
All pilots should take advantage of the opportunity to experience braking capability in the simulator on different contaminants when possible. While decelerating, scan the airspeed display in order to relate the change in speed to the kinesthetic perceptions. During the period of maximum brake application after touchdown, the antiskid system is working to keep the tires on the verge of a skid. The pilot may perceive small, abrupt pulses as the tires occasionally get a solid grip prior to skidding, followed by a short release of brakes to allow the tires to spin up again. As the surface condition becomes more challenging, the antiskid system will command longer brake releases to maintain a proper level of friction between the tire and the runway.
As the airplane decelerates, the braking effectiveness will increase but may never attain dry runway levels. As long as the pilot senses the cycling of the antiskid system, the pilot knows the brakes are performing to the maximum extent permitted by the runway surface condition.
Appendix 3 NOTE: The pilot cannot modulate the brakes better than the antiskid system. Pilot response time to the changing conditions is measured in seconds, and the antiskid system can adjust in milliseconds. The best braking performance will occur when the pilot presses hard on the brake pedals and maintains a constant pressure. Let the antiskid do all the modulation but be sensitive to that same antiskid operation. Be perceptive and make note of the antiskid pulses. That is the pilot’s firsthand knowledge of proper brake operation.
13. PERFORMANCE DATA NOTES. Every pilot should read and understand the information presented in the contaminated runway supplemental data before using the information to calculate performance. When the pilot thoroughly understands the operation of the antiskid system, becomes familiar with the runway condition at the destination, and completes and applies conservative landing distance calculations, the pilot will mitigate the risk of a runway overrun.
14. TABLES FOR RUNWAY MITIGATION. These tables are included to assist the pilot in the application of the concepts presented to mitigate the risks associated with the hazard of a runway overrun. Table 3-1, Memory Jogger: Can U Stop?; Table 3-2, All Factors Present Cumulative Landing Distance Example; and Table 3-3, All Factors Cumulative Landing Distance Example—All Elements Increasing Landing Distance Assessed, provide guides to be considered in order to mitigate a runway overrun. Table 3-1 provides a memory jogger for the concepts pilots must exercise to mitigate the risk of a runway overrun. Table 3-2 provides a sample of what can occur if all the runway factors to consider are present in a landing. Table 3-3 demonstrates the benefits of a stabilized approach, choosing to land with favorable winds, and timely deceleration.
NOTE: These items cannot replace the information contained in the AFM.
They are provided to help the flightcrew member recognize the possible increase in risk associated with certain conditions. The information presented in this AC must not be used to replace or supplant AFM landing performance or associated contaminated runway performance information provided by the manufacturer.
Appendix 3 TABLE 3-1. MEMORY JOGGER: CAN U STOP?
Can U StoP?
C–Calculate Use the manufacturer’s or company data to determine the landing distance required prior to departure and again prior to landing based on company standard operating procedures (SOP).
Be sure to consider factors as dry/wet runways and associated contamination, planned touchdown point, speed and height over the landing threshold, runway slope, tailwind/wind speed and direction, inoperative equipment, and any special cases.
U–Understand The manufacturer’s AFM landing data and it is derived based on flight test data. Factors to be applied to the data to adjust it for the current conditions. If data is not available, employ the information contained in Safety Alert for Operators (SAFO) 06012, Landing Performance Assessments at Time of Arrival (Turbojets).
S–Stabilized Ensure that you understand all the requirements of a stabilized approach and you are able to fly one given the actual conditions. If not, go around!
P–Professional Land like a professional using the airplane’s capabilities as described in the AFM and SOPs.
A professional puts safety ahead of style.
Appendix 3 TABLE 3-2. ALL FACTORS PRESENT CUMULATIVE LANDING
DISTANCE EXAMPLE
1. Available runway length. 5,000 ft
2. Dry runway unfactored AFM landing distance for Density Altitude (DA) and planned landing gross weight. 3,000 ft AFM landing dist.
3. Runway Slope -1%: Add 10% of landing distance per 1% downhill slope.
Example: 1% downhill slope adds 10% to the landing distance. 10% × 3,000 = 300 ft.
3,000 + 300 = 3,300 ft
4. Excessive airspeed at 50 ft landing threshold, landing distance increase: For each 10% increase in landing speed greater than the AFM, add 20% landing distance or:
Example: 10 % fast (3,300 × 0.20 = 660 ft).
3,300 + 660 = 3,960 ft
5. Tailwind Condition: Add 21% to landing distance for each 10 kts in tailwind.
Example: 10 kt tailwind 0.21 × 3,960 = 832 ft.
3,960 + 832 = 4,792 ft
6. Extended Flare: Add 200 ft/sec flare time: Results in a 200 ft/sec additive (2 × 200 = 400 ft). 4,792 + 400 = 5,192 ft
7. Excess 50-ft height: Add 200 ft to the landing distance for each 10 ft above 50 ft.
Example: 10 ft excess.
5,192 + 200 = 5,392 ft
8. Minimum equipment list (MEL)/Configuration Deviation List (CDL) additions: Any additions caused by MEL/CDL requirements. No MEL/CDL additive 0 ft.
NA
9. Sum of before landing lines 2 through 8 added 2,392 ft to the AFM landing distance, or 80% greater than 3,000 ft. 5,392 ft
10. Wet runway SAFO safety margin. If wet, add 15% of line 9 or use AFM data if available: 0.15 × 5,392 = 809 ft. 809 + 5,392 = 6,201 ft
ADDITIONAL FACTOR THAT WILL INCREASE THE LANDING DISTANCE BEYOND LINE 10
11. Deceleration devices, add 200 ft per each sec greater than 2 sec.
Example: 3 sec deployment time (1 sec more than the 2 sec max). Add 200 ft or use AFM data if available.
6,201 + 200 = 6,401 ft
12. Less than maximum braking add 20% to cumulative number, or use AFM data if available.
Example: Less than max braking: 0.2 × 6,401 = 1,280 ft.
6,401 + 1,280 = 7,681 ft
13. CUMULATIVE LANDING DISTANCE IS: After landing factors lines 11 and 12 added 1,480 + 6,201 ft = 7,681 ft, 54% greater than the available runway. Cumulative landing distance increased 1.56% greater than the AFM computed landing distance required.
7,681 ft Page 8
Appendix 3 TABLE 3-3. ALL FACTORS CUMULATIVE LANDING DISTANCE EXAMPLE—ALL ELEMENTS INCREASING LANDING DISTANCE ASSESSED
1. Available runway length. 5,000 ft
2. Dry runway unfactored AFM landing distance for DA and planned landing gross weight. 3,000 ft AFM landing dist.
3. Runway Slope -1%: Add 10% of landing distance per 1% downhill slope.
Example: 1% downhill slope adds 10% to the landing distance.
+ 300 ft
4. Excessive airspeed at 50 ft landing threshold, landing distance increase: For each 10% increase in landing speed greater than the AFM, add 20% landing distance or:
Example: 10% fast (3,300 × 0.20 = 660 ft).
NA
5. Tailwind condition: Add 21% to landing distance for each 10 kts in tailwind.
Example: 10 kt tailwind 0.21 × 3,960 = 832 ft.
NA
6. Extended flare: Add 200 ft/sec flare time: Results in a 200 ft/sec additive (2 × 200 = 400 ft). NA
7. Excess 50 ft height: Add 200 ft to the landing distance for each 10 ft above 50 ft.
Example: No excess height to assess.
NA
8. MEL/CDL additions: Any additions caused by MEL/CDL requirements. No MEL/CDL additive 0 ft. NA
9. Sum of before landing lines 2 through 8 added 300 ft equals 10% greater than 3,000 ft. 3,000 + 300 = 3,300 ft
10. Runway condition is wet.
If wet, add 15% of line or use AFM data if available:
0.15 × 3,300 = 495 ft.
3,300 + 495 = 3,795 ft
11. Deceleration devices deployed within 2 sec of touchdown. NA
12. Maximum braking applied. NA
13. After landing factors lines 10 through 13 added 495 ft, leaving 1,210 ft runway remaining (this includes the 15% safety margin). Cumulative landing distance results in 76% of the total runway available.
3,795 ft Page 9 (and 10)
Appendix 4 APPENDIX 4. UNSTABILIZED APPROACH CASE STUDY You, the first officer, obtained Automatic Terminal Information Service (ATIS) information during the descent that indicated strong westerly winds on the ground and field elevation of approximately 800 ft mean sea level (MSL). Because of terrain, the most common approach to the landing runway is via the instrument landing system (ILS) approach to another runway, and then to perform a circle-to-land maneuver to the landing runway.
a. Air traffic control (ATC) then advises you of updates to the ATIS and also to expect a straight-in approach. You have approximately 5 minutes to prepare for landing on the new runway. Without performing a completely new approach briefing, you prepare for the change in runway by confirming your previously planned flap setting of 40 degrees, with a reference landing airspeed (VREF) of 138 knots (kts). Given that the airplane is flying the ATC-assigned heading and descending steadily with the autopilot engaged, routine communications with ATC almost entirely consume the short time available to prepare the approach.
b. The newly assigned runway is relatively short and will have a tailwind; however, the landing distance is adequate, but provides little margin for error. While you are obtaining the new ATIS (indicating a tailwind for landing, but within the airplane’s tailwind limit), the captain receives and acknowledges an ATC instruction to maintain 230 kts or more until advised, with vectors to a base leg, and to follow another airplane to intercept the final approach path.
Then, when ATC clears your airplane for a visual approach to the runway, the airplane is at 230 kts, at 5,000 ft MSL, and almost 10 miles away from the runway. Noting that the airport’s elevation is approximately 800 ft MSL, the captain must both slow the airplane and descend relatively quickly to make the landing, while configuring the airplane for landing.
(1) Do You Continue With the Approach? ATC positions the airplane high and fast close to the runway, and now you face the difficult task of establishing a stabilized approach.
Alternative options include either extending the approach path in cooperation with ATC or abandoning the approach. However, 1 minute after ATC clears the airplane for the approach, you perform the first configuration change to get the airplane below 225 kts (the maximum speed to extend flaps to 5 degrees). The airplane is now descending to 3,000 ft, slowing through 225 kts, and slightly overshooting the final approach course on autopilot.
(2) What Would Your Landing Strategy Be? The captain then disconnects the autopilot and brings the airplane back on course, ordering gear extension and successive flap extensions, while maintaining 3,000 ft until 3 miles from the threshold. The captain then commands flaps 40 while the airplane is above 180 kts. (Maximum speed for flaps 40 is well below this speed.) The airplane then slows to 180 kts, and the captain is flying the approach at more than twice the normal 3-degree gradient to the runway in his or her efforts to touch down just beyond the runway threshold. When the airplane passes below 1,200 ft above ground level (AGL), and its descent rate increases through 2,900 ft/minute, the ground proximity warning system (GPWS) “sink rate” warning starts to sound continuously, later followed by the more stringent “whoop, whoop, pull up” warning.
Appendix 4
(3) What is Your Reaction? When the airplane reaches 1,000 ft above airport elevation, its airspeed has increased to almost 200 kts with a 14-knot tailwind, and it is descending at more than 2,600 ft/minute. When descending through 500 ft, 16 seconds from touchdown, speed is unchanged and descent rate is almost 2,000 ft/minute. You miss the 500 ft required callout as you are also concerned about the airplane that has landed ahead and has not yet cleared the runway. Despite all of this, the airplane continues at a steep gradient greater than 3 degrees until the captain begins the flare for landing at approximately 150 ft AGL. Although he manages to land the airplane within the normal touchdown zone (TDZ), he has not been able to slow the airplane while descending at that angle. Despite the engines remaining at idle, the airplane is flying on average some 45 kts faster than the target speed throughout the final approach and landing. The airplane touches down at a speed of 182 kts, with a 6-knot tailwind, some 2,150 ft beyond the runway threshold with approximately 3,900 ft of runway remaining. The captain does not apply and hold maximum brake pressure (as it was the airline’s policy to use manual braking rather than autobraking during landing rollouts), and uses reverse thrust. However, he is unable to stop the airplane on the runway, and the airplane overruns the runway.
(4) Lesson Learned. The lesson learned is that flying a stabilized approach is critical for safety, regardless of whether one is flying an airliner or a light airplane. Always fly per company procedures, use the manufacturer’s AFM/POH landing performance for the current landing conditions, exercise sound aeronautical decision-making (ADM), and ensure the following:
(a) The airplane is on the correct flightpath.
(b) Only small changes in heading/pitch are necessary to maintain the correct flightpath.
(c) For large airplanes, the airspeed is not faster than VREF (threshold crossing speed) plus 5 kts indicated speed, or as stated in the standard operating procedures (SOP) for windy conditions. Do not fly slower than VREF. For small airplanes, after aligning with the runway, fly the AFM/POH recommended approach airspeed, and adjust airspeed for windy conditions.
In the absence of a manufacturer’s recommended approach airspeed, use 1.3 × VSO (stall speed or minimum stead flight speed at which the airplane is controllable in the landing configuration), and use flaps per the wind conditions, or as recommended by the manufacturer to ensure positive lateral airplane control during the flare to touch down. (Refer to FAA-H-8083-3, Airplane Flying Handbook, for more information.)
(d) The airplane is in the correct landing configuration.
(e) Power setting is appropriate for the airplane configuration and is not below the minimum power for the approach as defined by the operating manual; and the crew has conducted all briefings and checklists.
Advisory Circular Feedback Form If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by contacting the General Aviation and Commercial Division (AFS-800) at 9-AFS-800-Correspondence@faa.gov or the Flight Standards Directives Management Officer at 9-AWA-AFS-140-Directives@faa.gov.
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