(iv) Tire Speed Limits. If tires approved through the technical standard order (TSO) process are used, it should be determined, within the weight, altitude, and temperature for which takeoff performance is shown in § 23.1587, that the TSO tire speed ratings are not exceeded at VL0F. If the tire speed rating would be exceeded under some combinations of weight, altitude, and temperature, then the tire speed limit should be established as an operating limitation. In compliance with § 23.1581(a)(2), a maximum takeoff weight limited by tire speed chart should also be included in the AFM performance section.
b. Procedures.
(1) Takeoff Distance Tests. The takeoff distance should be established by test. It may be obtained either by takeoffs conducted as a continuous operation from start to the 50-foot height or synthesized from acceleration segments and climb segment(s) determined separately. Recording theodolite or electronic equipment that is capable of providing horizontal distance and velocity, and height above the takeoff surface is highly desirable for takeoff distance tests. Additional required special ground equipment includes a sensitive anemometer capable of providing wind velocity and direction, a thermometer capable of providing accurate free-air temperature under all conditions, and an altimeter or barograph to provide pressure altitude.
(2) Segment Technique. For the segment technique, the airplane should be accelerated on the surface from brake release to rotation speed VR and on to the speed selected for the 50-foot height point. Six acceptable runs are recommended to establish the takeoff acceleration segment. VR should be selected so that the 50-foot speed can be achieved. A climb segment based on the rate of climb, free of ground effect, is added to the acceleration segment. See paragraph 25 of this AC and Appendix 2 for climb performance methods. Total distance is the sum of the acceleration segment plus the climb segment. For AFM presentation, the ground run would be the ground acceleration distance to VL0F, and the air distance would be the horizontal distance to climb at the 50-foot speed for 50 feet plus the ground acceleration distance from VL0F to the 50-foot speed. For those airplanes with retractable gear, the landing gear should be extended throughout or an alternative method of retraction may be initiated at a speed corresponding to a safe speed for gear retraction following liftoff in normal operations. If takeoff distance is determined using the "segmented" method, actual takeoffs using the AFM takeoff speed schedule should be conducted to verify that the actual takeoff distance to the 50-foot height does not exceed the calculated takeoff distance to the 50-foot height.
(3) Weight. Takeoff distance tests should be conducted at the maximum weight, and at a lesser weight if takeoff distance data for a range of weights is to be approved. The test results may be considered acceptable without correction for weight if a ±0.5 percent weight tolerance is observed.
(4) Nose wheel/tail wheel. In the absence of evidence to the contrary, the "critical" c.g.
position for takeoff distance tests may be assumed to be forward.
(5) Wind. Wind velocity and direction should be measured adjacent to the runway during the time interval of each test run. See paragraph 6.a.(5) of this AC for wind velocity and direction tolerances. For the ground run portion of the segment technique, the following relationship was developed empirically and is an acceptable method for correction of lowwind conditions:
SG = SGW 1 18 5 ±⎛⎝⎜ ⎞⎠⎟VV WTOW .
Where: S G = no-wind takeoff ground distance (feet) S GW = takeoff ground distance at a known wind velocity (feet) V W = wind velocity (feet second) V TOW = true ground speed, at lift-off with a known wind velocity (feet/second)
Notes: 1. + is used for headwind and - for tailwind
2. Wind, then slope corrections should be applied before further data reduction.
(6) Runway Slope. The effect of runway gradient can be significant for heavy airplanes or for low thrust-to-weight ratio airplanes, even if the gradient of the runway is small. Gradient should be controlled by proper runway selection. The correction is as follows:
SG = θsin21 1 1 ⎟⎟⎠⎞⎜⎜⎝⎛± TOGS GS V gS S
Where: S GS1 = ground distance on a sloping runway g = acceleration of gravity, 32.17 ft./sec2 V TO = airplane velocity at lift-off in ft./sec. (true) θ = angle of the slope in degrees (not percent)
+ for upslope and - for downslope
c. Commuter Category Airplanes.
(1) Objective of Takeoff Requirement. Section 23.53(c) requires that performance be determined that provides accountability for the selected operating weights, altitudes, ambient temperatures, configurations, and corrected for various wind and runway gradient conditions.
(2) Takeoff Profile. Tests are required to determine the performance throughout the takeoff path as specifically defined by § 23.55 through § 23.59, and as discussed in paragraphs 21 through 23 of this AC.
(3) Expansion of Takeoff Data for a Range of Airport Elevations.
(i) These guidelines are applicable to expanding takeoff data above the altitude at which the basic or verifying tests were obtained.
(ii) In general, takeoff data may be extrapolated above and below the altitude at which the basic test data was obtained without additional conservatism within the following constraints.
(iii) When the basic takeoff tests are accomplished between sea level and approximately 3,000 feet, the maximum allowable extrapolation limits are 6,000 feet above and 3,000 feet below the test field elevation. If it is desired to extrapolate beyond these limits, one of two procedures may be employed.
(A) Extrapolation of Performance Data for a Range of Altitudes When Verifying Tests are Not Conducted. The approval of performance data for airport elevations beyond the maximum elevation permitted by basic tests may be allowed without conducting verifying tests if the calculated data include a conservative factor. This conservatism should result in an increase of the calculated takeoff distance at the desired airport elevation by an amount equal to zero percent for the highest airport elevation approved on the results of the basic tests and an additional cumulative 2 percent incremental factor for each 1,000 feet of elevation above the highest airport elevation approved for zero percent conservatism. The 2 percent incremental factor should have a straight line variation with altitude. When performance data are calculated for the effects of altitude under this procedure, the following provisions are applicable:
(1) Previously established calculation procedures should be used, taking into account all known variables.
(2) The calibrated installed engine power for the pertinent speed and altitude ranges should be used.
(3) The brake kinetic energy limits established by airplane ground tests should not be exceeded.
(B) Extrapolation of Performance Data When Verifying Tests are Conducted.
(1) If data approval is desired for a greater range of airport elevations, the performance may be calculated from the basic test data up to the maximum airport elevation, provided verifying tests are conducted at appropriate elevations to substantiate the validity of the calculations. The actual airplane performance data from the verifying tests should correspond closely to the calculated performance values.
(2) For the verifying tests, it has been found that normally three takeoffs at maximum weights for the elevations tested will provide adequate verification.
(3) If verifying tests substantiate the expanded takeoff data, the data may be further expanded up to 6,000 feet above the altitude at which the verifying tests were conducted. At altitudes higher than 6,000 feet above the verifying test altitude, the 2 percent per 1,000 feet cumulative factor discussed in paragraph (i) above should be applied starting at zero percent at the verifying test altitude plus 6,000 feet.
20. RESERVED
21. SECTION 23.55 ACCELERATE-STOP DISTANCE.
a. Explanation. This section describes test demonstrations necessary to determine accelerate-stop distances for airplane performance required to be published in the Performance Section of the AFM.
b. Procedures.
(1) Accelerate-stop tests should be determined in accordance with the provisions of this paragraph.
(i) Number of Test Runs. A sufficient number of test runs should be conducted for each airplane configuration desired by the applicant, in order to establish a representative distance that would be required in the event of a rejected takeoff at or below the takeoff decision speed V1.
(ii) Time Delays. The procedures outlined in paragraph 21.b.(12), as required by § 23.45(f)(5), apply appropriate time delays for the execution of retarding means related to the accelerate-stop operational procedures and for expansion of accelerate-stop data to be incorporated in the AFM.
(iii) Reverse Thrust. The stopping portion of the accelerate-stop test may not utilize propeller reverse thrust unless the thrust reverser system is shown to be safe, reliable, and capable of giving repeatable results. See subparagraph c.
(2) Airport Elevation. Accelerate-stop runs at different airport elevations can be simulated at one airport elevation provided the braking speeds used include the entire energy range to be absorbed by the brakes. In scheduling the data for the AFM, the brake energy assumed should not exceed the maximum demonstrated in these tests.
(3) Braking Speeds. The braking speeds referred to herein are scheduled test speeds and need not correspond to the values to be scheduled in the AFM, since it is necessary to increase or decrease the braking speed to simulate the energy range and weight envelope.
(4) Number of Runs. At least two test runs are necessary for each configuration when multiple aerodynamic configurations are being shown to have the same braking coefficient of friction, unless sufficient data is available for the airplane model to account for variation of braking performance with weight, kinetic energy, lift, drag, ground speed, torque limit, and so forth. These runs should be made with the airplane weight and kinetic energy varying throughout the range for which takeoff data is scheduled. This will usually require at least six test runs. These tests are usually conducted on hard surfaced, dry runways.
(5) Alternate Approvals. For an alternate approval with antiskid inoperative, nose wheel brakes or one main wheel brake inoperative, auto braking systems, and so forth, a full set of tests, as mentioned in paragraph 21.b.(4), should normally be conducted. A lesser number of tests may be accepted for "equal or better" demonstrations, or to establish small increments, or if adequate conservatism is used during testing.
(6) Maximum Energy Stop. A brake energy demonstration is needed to show compliance with the brake energy requirements. A maximum energy stop (or some lesser brake energy) is used to establish a distance that can be associated with the demonstrated kinetic energy.
An applicant can choose any level of energy for demonstration providing that the AFM does 28
not show performance beyond the demonstrated kinetic energy. The demonstration should be conducted at not less than maximum takeoff weight and should be preceded by a 3-mile taxi, including three full stops using normal braking and all engines operating. Propeller pitch controls should be applied in a manner that is consistent with procedures to be normally used in service. Following the stop at the maximum kinetic energy level demonstration, it is not necessary for the airplane to demonstrate its ability to taxi. The maximum kinetic airplane energy at which performance data is scheduled should not exceed the value for which a satisfactory after-stop condition exists. A satisfactory after-stop condition is defined as one in which fires are confined to tires, wheels, and brakes, and which would not result in progressive engulfment of the remaining airplane during the time of passenger and crew evacuation. The application of fire fighting means or artificial coolants should not be required for a period of five minutes following the stop.
(7) Maximum Energy Stop from a Landing. In the event the applicant proposes to conduct the maximum energy RTO demonstration from a landing, a satisfactory accounting of the brake and tire temperatures that would have been generated during taxi and acceleration, required by paragraph 21.b.(6), should be made.
(8) Instrumentation. Either ground or airborne instrumentation should include a means to determine the horizontal distance-time history.
(9) Wind Speed. The wind speed and direction relative to the active runway should be determined. The height of the wind measurement should be noted to facilitate corrections to airplane wing level.
(10) Configurations. The accelerate-stop tests should be conducted in the following configurations:
(i) Heavy to light weight, as required.
(ii) Most critical c.g. position.
(iii) Wing flaps in the takeoff position(s).
(iv) Tire pressure. Before taxi and with cold tires, set to the highest value appropriate for the takeoff weight for which approval is being sought.
(v) Engine. Set r.p.m. at applicant's recommended upper idle power limit, or the effect of maximum idle power may be accounted for in data analyses. Propeller condition should also be considered. See discussion in subparagraph (11), Engine Power.
(11) Engine Power. Engine power should be appropriate to each segment of the rejected takeoff and account for thrust decay times. See discussion of § 23.57(a)(2) in paragraph
22.c.(1). At the selected speed that corresponds to the required energy, the airplane is brought to a stop employing the acceptable braking means. The critical engine's propeller should be in the position it would normally assume when an engine fails and the power levers are closed.
(i) High-Drag Propeller Position. The high-drag position (not reverse) of the remaining engines' propellers may be utilized provided adequate directional control can be 29
demonstrated on a wet runway. Simulating wet runway controllability by disconnecting the nose wheel steering may be used. The use of the higher propeller drag position (that is, ground fine) is conditional on the presence of a throttle position that incorporates tactile feel that can consistently be selected in service by a pilot with average skill. It should be determined whether the throttle motions from takeoff power to this ground fine position are one or two distinctive motions. If it is deemed to be two separate motions, then accelerate-stop time delays should be determined accordingly and applied to expansion of data.
(ii) Reverse Thrust. See subparagraph (c) for discussion of when reverse thrust may be used. Demonstration of full single engine reverse controllability on a wet runway and in a 10-knot adverse crosswind will be required. Control down to zero speed is not essential, but a cancellation speed based on controllability can be declared and credit given for use of reverse above that speed. The use of reverse thrust on one engine on a wet runway requires that the reverse thrust component be equally matched by a braking component and rudder use on the other side. Experience has shown that using reverse with one engine inoperative requires brakes to be modulated differently between left and right while applying only partial reverse thrust, even on dry pavement. Disconnecting nose wheel steering will not adequately simulate a wet runway for a full reverse condition. The use of a reverse thrust propeller position is conditional on the presence of a throttle position, which incorporates tactile feel, that can consistently be selected in service by a pilot with average skill. Selection of reverse thrust from takeoff power typically requires the power lever to be retarded to idle, a gate or latching mechanism to be overcome, and the power lever to be further retarded into the ground/reverse range.
This is interpreted as three "distinctive motions," with each regarded as activation of a separate deceleration device. Accelerate-stop time delays should be determined accordingly and applied to expansion of data. Experience has shown that single engine thrust reverse, due to rudder blanking, may not be as critical as two-engine reverse, for controllability. If brake modulation is required and allowed for steering, then the reduced braking must be accounted for in the stopping performance.
(12) Accelerate-Stop Time Delays. Figure 21-1 is an illustration of the accelerate-stop time delays considered acceptable for compliance with § 23.45:
VEF V 1 ENGINE
FAILURE
ACTIVATION OF
FIRST DECEL DEVICE
ENGINE FAILURE
RECOGNITION trec
ACTIVATION OF
SECOND DECEL DEVICE t rec t a1 t a1 + t
ACTIVATION OF
THIRD DECEL DEVICE t a2 t a2 + t
DEMONSTRATION
TIME DELAYS
FLIGHT MANUAL
EXPANSION
TIME DELAYS
FIGURE 21-1 - ACCELERATE-STOP TIME DELAYS
(i) ∆trec = engine failure recognition time. The demonstrated time from engine failure to pilot action indicating recognition of the engine failure. For AFM data expansion purposes, it has been found practical to use the demonstrated time or one second, whichever is greater, in order to allow a time that can be executed consistently in service.
(ii) ∆ta1 = the demonstrated time interval between activation of the first and second deceleration devices.
(iii) ∆ta2 = the demonstrated time interval between activation of the second and third deceleration devices.
(iv) ∆t = a one-second reaction time delay to account for in-service variations. For AFM calculations, airplane deceleration is not allowed during the reaction time delays. If a command is required for another crewmember to actuate a deceleration device, a two-second delay, in lieu of the one-second delay, should be applied for each action. For automatic deceleration devices that are approved for performance credit for AFM data expansion, established times determined during certification testing may be used without the application of additional time delays required by this paragraph.
(v) The sequence for activation of deceleration devices may be selected by the applicant.
If, on occasion, the desired sequence is not achieved during testing, the test need not be repeated; however, the demonstrated time interval may be used.
(13) The procedures used to determine accelerate-stop distance should be described in the Performance Information Section of the AFM.
c. Use of Reverse Thrust. Section 23.55(b) permits means other than wheel brakes to be used in determining the stopping distance, when the conditions specified in § 23.55(b) are met. One of the conditions is that the means be safe and reliable.
(1) Reliable. Compliance with the "reliable" provision of the rule may be accomplished by an evaluation of the pitch changing/reversing system in accordance with § 23.1309. The methods of AC 23.1309-1 should be used in the evaluation, even though type-certificated engine or propeller systems may not have been subjected to the AC 23.1309-1 analysis during certification. Additionally, Society of Automotive Engineers (SAE) document ARP-926A, "Fault/Failure Analysis Procedure," will assist in conducting reliability and hazard assessments. Additionally, § 23.1309(d) requires the system to be designed to safeguard against hazards to the airplane in the event the system or any component thereof malfunctions or fails. An acceptable means for showing compliance with the requirement would be to conduct a Failure Modes and Effects Analysis (FMEA) of the system. An acceptable analysis would show that the effects of any system or component malfunction or failure would not result in a hazard to the airplane and that the propeller reversing system is reliable. SAE document, ARP-926A, contains acceptable criteria for conducting such an analysis.
(2) Safe. Compliance with the "safe" provisions of §§ 23.55 (b)(2) and 23.75(f)(1) will require an evaluation of the complete system, including operational aspects, to ensure no unsafe feature exists.
Safe and reliable also means that it is extremely improbable that the system can mislead the flight crew or will allow gross asymmetric power settings, for example, forward thrust on one engine versus reverse thrust on the other. In achieving this level of reliability, the system should not increase crew workload or require excessive crew attention during a very dynamic time period. Also, the approved performance data should be such that the average pilot can duplicate this performance by following the AFM procedures.
22. SECTION 23.57 TAKE-OFF PATH.
a. Section 23.57(a).
(1) Explanation.
(i) The takeoff path requirements of § 23.57 and the reductions required by § 23.61 are established so that the AFM performance can be used in making the necessary decisions relative to takeoff weights when obstacles are present. Net takeoff flight path data should be presented in the AFM as required by § 23.1587(d)(6).
(ii) The required performance is provided in the AFM by either pictorial paths at various power-to-weight conditions with corrections for wind or by a series of charts for each segment along with a procedure for connecting these segments into a continuous path.
(2) Procedures.
(i) Section 23.57(a) requires that the takeoff path extend to the higher of where the airplane is 1500 feet above the takeoff surface or to the altitude at which the transition to en route configuration is complete and a speed is reached at which compliance with § 23.67(c)(3) is shown.
(ii) Section 23.66 requires the airplane not to be banked before reaching a height of 50 feet as shown by the net takeoff flight path data.
(iii) The AFM should contain information required to show compliance with the climb requirements of § 23.57 and § 23.67(c)(3). This should include information related to the transition from the takeoff configuration and speed to the en route configuration and speed. The effects of changes from takeoff power to maximum continuous power should also be included.
(iv) Generally, the AFM shows takeoff paths at low power to weight that include acceleration segments between 400 and 1500 feet and end at 1500 feet. At high power to weight, these takeoff paths extend considerably higher than 1500 feet above the takeoff surface. On some airplanes, either the takeoff speed schedules or the flap configuration, or both, do not require acceleration below 1500 feet, even at limiting performance gradients.
b. Section 23.57(a)(1) - Takeoff Path Power Conditions.
(1) Explanation. The takeoff path should represent the actual expected performance at all points. If the path is constructed by the segmental method, in accordance with § 23.57(d)(2) and § 23.57(d)(4), it should be conservative and should be supported by at 32
least one demonstrated fly-out to the completed en route configuration. This is necessary to ensure all required crew actions do not adversely impact the required gradients.
(2) Procedures.
(i) To substantiate that the predicted takeoff path is representative of actual performance, the power used in its construction must comply with § 23.45. This requires, in part, that the power for any particular flight condition be that for the particular ambient atmospheric conditions that are assumed to exist along the path. The standard lapse rate for ambient temperature is specified in Appendix 7 of this AC under "Standard Atmosphere" and should be used for power determination associated with each pressure altitude during the climb.
(ii) Section 23.57(c)(4) requires that the power up to 400 feet above the takeoff surface represents the power available along the path resulting from the power lever setting established during the initial ground roll in accordance with AFM procedures. This resulting power should represent the normal expected variations throughout the acceleration and climb to 400 feet and should not exceed the limits for takeoff power at any point.
(iii) A sufficient number of takeoffs, to at least the altitude above the takeoff surface scheduled for V2 climb, should be made to establish the power lapse resulting from a fixed power lever. An analysis may be used to account for various engine bleeds, for example, ice protection, air conditioning, and so forth. In some airplanes, the power growth characteristics are such that less than full rated power is required to be used for AFM takeoff power limitations and performance.
(iv) Engine power lapse with speed and altitude during the takeoff and climb, at fixed power lever settings, may be affected by takeoff pressure altitude.
(v) Most turboprop engines are sensitive to increasing airspeed during the takeoff roll.
The applicant's procedure should be evaluated and, if acceptable, the procedure should be reflected in the AFM. The AFM takeoff field length and takeoff power setting charts are based on the approved procedure. Approved procedures should be ones that can be accomplished in service by pilots of normal skill. For example, if a power adjustment is to be made after brake release, the power should be adjustable without undue attention.
Only one adjustment is allowed.
(vi) A typical "non-rolling" takeoff procedure is as follows:
(A) After stopping on the runway, adjust all engines to a static takeoff power setting (selected by the applicant).
(B) Release brakes.
(C) Upon reaching 50 to 60 knots, adjust power levers to maintain torque and temperatures within limits. Only one adjustment is allowed.
(vii) A typical "rolling takeoff" procedure is as follows:
(A) Release brakes.
(B) Adjust power levers to takeoff power in a smooth motion.
(C) As speed increases, make a small adjustment as necessary to preclude exceeding torque or temperature limits.
c. Section 23.57(a)(2) - Engine Failure.
(1) Explanation. Propeller thrust/drag characteristics should represent conditions that occur when the engine is actually failed. The power time history used for data reduction and expansion should be substantiated by test results.
(2) Procedures. Sufficient tests should be conducted utilizing actual fuel cuts to establish the propeller thrust decay history.
d. Section 23.57(c)(1) - Takeoff Path Slope.
(1) Explanation. For showing compliance with the positive slope required by § 23.57(c)(1), the establishment of a horizontal segment, as part of the takeoff flight path, is considered to be acceptable, in accordance with § 23.61(c). See figure 24-2. See paragraph 24b(2) for further discussion.
(2) Procedures.
(i) The level acceleration segment in the AFM net takeoff profile should begin at the horizontal distance along the takeoff flight path where the net climb segment reaches the AFM specified acceleration height. See figure 24-2.
(ii) The AFM acceleration height should be presented in terms of pressure altitude increment above the takeoff surface. This information should allow the establishment of the pressure altitude "increment" (HP) for off-standard ambient temperature so that the geometric height required for obstacle clearance is assured. For example:
Given:
• Takeoff surface pressure altitude (Hp) = 2,000 feet
• Airport standard temperature absolute (TS ) = 11oC+273.2 = 284.2°k
• Airport ambient temperature absolute (TAM) = -20°C+273.2 = 253.2°k
• Geometric height required (∆h) = 1,500 feet above takeoff surface
Find:
• Pressure altitude increment (∆Hp) above the takeoff surface ∆Hp = ∆h(TS/TAM) = 1500 feet (284.2°k/253.2°k) ∆Hp = 1684 feet
e. Section 23.57(c)(2) - Takeoff Path Speed.
(l) Explanation.
(i) It is intended that the airplane be flown at a constant indicated airspeed to at least 400 feet above the takeoff surface. This speed should meet the constraints on V2 of § 23.51(c)(4).
(ii) The specific wording of § 23.57(c)(2) should not be construed to imply that above 400 feet the airspeed may be reduced below V2 but instead that acceleration may be commenced.
(2) Procedures. None.
f. Section 23.57(c)(4) - Configuration Changes.
(l) Explanation.
(i) The intent of this requirement is to permit only routine crew actions to establish the engine-inoperative takeoff path. The power levers may only be adjusted early during the takeoff roll, as discussed under § 23.57(a)(1) (paragraph 22b(2)(b)), and then left fixed until at least 400 feet above the takeoff surface.
(ii) Simulation studies and accident investigations have shown that when heavy workload occurs in the cockpit, as with an engine loss during takeoff, the crew might not advance the operative engines to avoid the ground even if the crew knows the operative engines have been set at reduced power. This same finding applies to manually feathering a propeller. The landing gear may be retracted, because this is accomplished routinely, once a positive rate of climb is observed. This also establishes the delay time to be used for data expansion purposes.
(2) Procedures.
(i) To permit the takeoff to be based on a feathered propeller up to 400 feet above the takeoff surface, automatic propeller feathering devices may be approved if adequate system reliability is shown in accordance with § 23.1309. Other automatic systems such as one which minimizes drag of the inoperative propeller by sensing negative torque may also be approved. Drag reduction for a manually feathered propeller is permitted for flight path calculations only after reaching 400 feet above the takeoff surface.
(ii) For flap retraction above 400 feet, a speed of not less than the lesser of 1.1 VMC or
1.2 VS1 should be maintained.
g. Section 23.57(d) - Takeoff Path Construction.
(1) Explanation. To take advantage of ground effect, AFM takeoff paths utilize a continuous takeoff path from VLOF to 35 feet, covering the range of power-to-weight ratios. From that point, free air performance, in accordance with § 23.57(e), is added segmentally. This methodology may yield an AFM flight path that is steeper with the gear down than up. The airplane should not be banked before reaching a height of 50 feet as shown by the net takeoff flight path. This requires determination of climb data in the wings level condition.
(2) Procedures. The AFM should include the procedures necessary to achieve this performance.
h. Section 23.57(e)(2) - Takeoff Path Segment Conditions.
(l) Explanation. Section 23.57(e)(2) requires that the weight of the airplane, the configuration, and the power setting must be constant throughout each segment and must correspond to the most critical condition prevailing in the segment. The intent is that, for simplified analysis, the performance be based on that available at the most critical point in time during the segment, not that the individual variables (weight, approximate power setting, and so forth) should each be picked at its most critical value and then combined to produce the performance for the segment.
(2) Procedures. The performance during the takeoff path segments should be obtained using one of the following methods:
(i) The critical level of performance as explained in paragraph 22h(l); or
(ii) The actual performance variation during the segment.
i. Section 23.57(d)(4) - Segmented Takeoff Path Check.
(1) Explanation. None.
(2) Procedures. The takeoff path should be checked by continuous demonstrated takeoffs.
A sufficient number of these, using the AFM established takeoff procedures and speeds, and covering the range of power-to-weight ratios, should be made to ensure the validity of the segmented takeoff path. The continuous takeoff data should be compared to takeoff data calculated by AFM data procedures but using test engine power and test speeds.
j. Turboprop Reduced Power Takeoffs.
(1) Reduced takeoff power is a power less than approved takeoff power for which power setting and airplane performance is established by corrections to the approved power setting and performance. When operating with reduced takeoff power, the power setting that establishes power for takeoff is not considered a limitation.
(2) It is acceptable to establish and use a takeoff power setting that is less than the approved takeoff power provided the following:
(i) The establishment of the reduced power takeoff data is handled through the type certification process and contained in the AFM.
(ii) The reduced takeoff power setting:
(A) Does not result in loss of systems or functions that are normally operative for takeoff, such as engine failure warning, configuration warning, autofeather, automatic throttles, rudder boost, automatic ignition, or any other safety related system dependent upon a minimum takeoff power setting.
(B) Is based on an approved engine takeoff power rating for which airplane performance data is approved.