(iii) For the purpose of establishing takeoff distances and takeoff runs, the clearway plane is defined in Part 1. The clearway is considered to be part of the takeoff surface, and a height of 35 feet may be measured from that surface. See figure 23-5.
Clearway 35' Takeoff Path Clearway Plane
1.25% Maximum
FIGURE 23-5 - CLEARWAY PROFILES
24. SECTION 23.61 TAKEOFF FLIGHT PATH.
a. Takeoff Flight Path - Section 23.61(a). The takeoff flight path begins 35 feet above the takeoff surface at the end of the takeoff distance determined in accordance with § 23.59. The takeoff flight path ends when the airplane's height is the higher of 1,500 feet above the takeoff surface or at an altitude at which the configuration and speed have been achieved in accordance with § 23.67(c)(3). See figure 24-1.
b. Net Takeoff Flight Path. - Section 23.61(b) and (c).
(1) The net takeoff flight path is the actual path diminished by a gradient of 0.8 percent for two-engine airplanes, 0.9 percent for three-engine airplanes, and 1.0 percent for four-engine airplanes. See figure 24-2.
(2) The net takeoff flight path is the flight path used to determine the airplane obstacle clearance. Section 23.61(b) states the required climb gradient reduction to be applied throughout the flight path to determine the net flight path, including the level flight acceleration segment. Rather than decrease the level flight path by the amount required by § 23.61(b), § 23.61(c) allows the airplane to maintain a level net flight path during acceleration but with a reduction in acceleration equal to the gradient decrement required by § 23.61(b). By this method, the applicant exchanges altitude reduction for increased distance to accelerate in level flight in determination of the level flight portion of the net takeoff path.
SEGMENT*
LANDING GEAR FLAPS POWER
AIRSPEED
ENGINES GROUND ROLL 1st 2nd ACCELERATION FINAL
DOWN RETRACTION RETRACTED
TAKEOFF RETRACTING ENROUTE POSITION
PROPELLER
TAKEOFF ABOVE 400 FT THRUST CAN BE REDUCED IF THE REQUIREMENTS OF 23.57(c)(3) CAN
BE MET WITH LESS THAN TAKEOFF THRUST
MAXIMUM
CONTINUOUS
ACCELERATING ACCELERATING VENROUTE
ALL OPERATING ONE INOPERATIVE
TAKEOFF ONE AUTOFEATHERED OR WINDMILLING ONE FEATHERED UP TO 400 FT 400 FT OR GREATER
V EF V LOF 35 FT
TAKEOFF DISTANCE (LONGER OF 1 ENG INOP TAKEOFF OR 1.15 ALL ENG TAKEOFF) PATH 1 PATH 2
TAKEOFF FLIGHT PATH 1500 FTHEIGHT > 1500 FT HEIGHT > 400 FT
HEIGHTS ARE
REFERENCED TO
RUNWAY ELEVATION AT
END OF TAKEOFF DISTANCE SEE NOTE SEE NOTE V2
Note: The en route takeoff segment* usually begins with the airplane in the en route configuration and with maximum continuous thrust, but it is not required that these conditions exist until the end of the takeoff path when compliance with § 23.67(c)(3) is shown. The time limit on takeoff thrust cannot be exceeded.
* Segments as defined by § 23.67.
FIGURE 24-1 - TAKEOFF SEGMENTS AND NOMENCLATURE 42
35' 35' Net Flight Path Level from Takeoff Surface >400' Obstacle Clearance
FIGURE 24-2 - NET TAKEOFF FLIGHT PATH
25. SECTION 23.65 CLIMB: ALL ENGINES OPERATING.
a. Explanation.
(1) Objectives. The climb tests associated with this requirement are performed to establish the airplane's all-engine performance capability for altitudes between sea level and not less than 10,000 feet with wing flaps set to the takeoff position. This is necessary to enable comparison with the minimum climb performance required and for AFM presentation of climb performance data of 10,000 feet including the effect of altitude and temperature (see § 23.1587) and including the effect of weight for aircraft over 6,000 pounds maximum takeoff weight (MTOW) and turbine engine aircraft.
(2) Cooling Climbs. Applicants with single engine reciprocating powered airplanes may vary the climb speeds to meet the requirements of § 23.1047. If variations in climb speeds are required to meet the cooling tests, the applicant may wish to establish the variation of rate of climb with speed.
(3) Sawtooth Climbs. A common method of determining climb performance is sawtooth climbs. A series of climbs, known as sawtooth climbs, should be conducted at several constant indicated airspeeds using a constant power setting and a prescribed configuration. A minimum of three series of sawtooth climbs should be conducted. The mean altitudes through which the sawtooth climbs are conducted should be:
(i) As near sea level as practical; and
(ii) Close to the ceiling (where 100 feet/minute can be maintained) for sea level engines;
and
(iii) An intermediate altitude, taking into consideration the power characteristics of the engine.
b. Procedures - Sawtooth Climbs.
(1) Climb Technique. With the altimeter adjusted to a setting of 29.92 inches Hg (pressure altitude), the series of climbs should be initiated at a chosen altitude. Stabilize airspeed and power prior to recording data. The time at the beginning of each run should be recorded for weight-accounting purposes, and the stabilized climb should be continued for 3 minutes or 43
3,000 feet minimum while holding airspeed substantially constant. Climbs should be conducted 90 degrees to the wind and, alternately, on reciprocal headings to minimize the effects of windshear. Since the rate at which the altitude changes is the primary consideration of the test, particular care should be taken to observe the precise altimeter indication at precise time intervals. Time intervals of not more than 30 seconds are recommended for altimeter readings. Airspeed, ambient temperatures, r.p.m., and other engine power parameters also should be recorded, permissibly at longer intervals. Rates-of-climb/sink observed for test conditions should be greater than +100 feet-per-minute. Rates of climb near zero tend to be unreliable. A running plot of altitude-versus-time provides an effective means of monitoring acceptability of test data as the run progresses, and a running plot of the observed rate of climb obtained for each airspeed enables similar monitoring of the sawtooth program. This procedure is recommended because it affords opportunity for promptly observing and economically rectifying questionable test results.
(2) Air Quality. In order to obtain accurate results, it is essential that the sawtooth climbs be conducted in smooth air. In general, the effects of turbulence are more pronounced in test data obtained at lower rates of climb and, when testing for compliance with minimum climb requirements, even slight turbulence may produce errors in observed climbs of such magnitude as to render the data inconclusive with respect both to rate of climb and best climb speed. Less obvious but equally unacceptable for climb testing is the presence of an inverse gradient in the ambient temperature.
(3) Test Airspeeds. The airspeeds selected for the sawtooth should bracket the best climb speed, which for preliminary purposes may be estimated as 140 percent of the power-off stalling speed. The lowest climb test speed should be as near the stalling speed as can be flown without evidence of buffeting or necessity for abnormally frequent or excessive control movements, which might penalize the climb performance. Although the example shown in figure 25-1 has 10-knot intervals, the interval between test speeds should be smaller at the lowspeed end of the range and should increase as the speed increases. Suggested intervals are 5 knots at the low end, varying to 15 knots at the high end. In addition, the maximum level flight speed and VS (or VMIN) at the approximate mid-range test altitude provide a useful aid in defining the curves in figure 25-2.
(4) Data Plotting. Sawtooth climb data is plotted on a graph using altitude and time as the basic parameters as shown in figure 25-1. After the sawtooth data has been plotted, draw in the mean altitude line. A tangent line can now be drawn to each of the sawtooth climb curves at the mean altitude intersection. By determining the slope of the tangent lines, the observed rate of climb at the mean altitude for each sawtooth can be determined.
(5) Data Corrections. For the density altitude method of data reduction (see Appendix 2), it is necessary to correct the data to standard atmospheric conditions, maximum weight, and chart brake horsepower before proceeding any further with the observed data. These corrections sometimes change the observed data a significant amount. The maximum level flight speed (VMAX) data points should also be corrected to assist in defining the curves in figure 25-2.
(6) Plotting of Corrected Data. After the observed data has been corrected to the desired standards, it can be plotted as shown in figure 25-2 with the rate of climb versus calibrated airspeed at various density altitudes. It should be noted that the stall speed points are not 44
usually true stabilized zero rate-of-climb data points. However, the stall speed points are useful in defining the asymptotic character of the left hand part of the curve.
FIGURE 25-1 - OBSERVED DATA
(7) Speed Schedule Data Points. From the curves of figure 25-2, it is now possible to determine the airplane's best rate of climb speed schedule, VY. This is done by drawing a straight line through the peaks (highest rate of climb point) of each of the previously drawn curves of Rate-of-climb vs. CAS. Also, it is possible to obtain from this graph the best angle of climb speed schedule, VX. This is done by drawing tangent lines to the Rate-of-climb vs.
CAS curves from the graph origin and connecting each of the tangent intersect points with a straight line. It should be noted that the VX and VY speed lines intersect at "zero" rate of climb. This is because zero rate of climb occurs at the airplane's absolute ceiling and VX, VY, VMIN, and VMAX are all the same speed at this point.
(8) Speed and Rate of Climb. Directly from information obtained from figure 25-2, it is possible to plot the climb performance of the airplane into a more usable form. By reading the rates of climb at the VY intersect points and plotting them against altitude, as shown in figure 25-3, it is possible to determine the rate of climb from sea level to the absolute ceiling.
(9) Cowl Flap and Mixture. Cowl flaps should be in the position used for cooling tests. The mixture setting should be set to that used during the cooling test.
(10) Weight and C.G. For climb performance tests, the airplane's test weight, load distribution and engine power should be recorded. Usually, forward c.g. is critical for climb performance.
c. Continuous Climb. For engine changes where the objective is to determine that new climb performance is equal to or better than the old climb performance and the all-engine climb performance is obviously in excess of the requirements of § 23.65, a continuous climb may be used to obtain the data. The rate of climb data at a convenient number of points should be reduced to standard day conditions.
d. Extrapolation of Climb Data. The climb data expansion required by § 23.1587 from sea level to 10,000 feet and from ISA to ISA + 30 °C can be accomplished by the methods in Appendix 2. Normally, the same method used for data reduction should be used for data expansion. Use caution in extrapolating beyond altitudes that have not been verified by flight tests. Generally, data should not be extrapolated more than 3,000 feet in altitude.
FIGURE 25-2 - RATE OF CLIMB VS. AIRSPEED
e. Special Equipment or Instrumentation. Climb performance tests require an airspeed indicator, sensitive altimeter, and total air temperature indicator with a known recovery factor.
For reciprocating engine-powered airplanes, an induction air temperature gauge, engine tachometer, manifold pressure gauge, and cylinder head temperature indicator may be appropriate. For turbine-powered airplanes, indicators of power parameters, such as torque meter, EGT, N1, N2, and propeller r.p.m., may be appropriate. Either a fuel counter or fuel flowmeter, or both, is useful. All instruments should be calibrated, and the calibration data should be included with the test records. In addition, a stopwatch and appropriate data recording board and forms are required.
f. Climb Performance After STC Modifications. (Reserved)
26. SECTION 23.66 TAKEOFF CLIMB, ONE ENGINE INOPERATIVE.
Section 23.66(1) for normal, utility, and acrobatic category airplanes greater than 6,000 lbs. and turbine-engine powered airplanes in the normal, utility, and acrobatic category requires the propeller of the inoperative engine to be in the position it "rapidly and automatically assumes" for the determination of one-engine inoperative takeoff climb performance. This allows performance credit for a reliable system that rapidly drives the propeller to a low drag setting with no action from the pilot. If no such system is fitted, the propeller should be assumed to be in the most critical condition.
5,000 10,000 15,000 500 1,000 1,500
RATE-OF-CLIMB
DENSITY
ALTITUDE
AIRPSEED - KCAS NORMALLY ASPIRATED RECIP. ENGINE - FULL THROTTLE TURBO CHARGED RECIP. ENGINETURBOPROP ENGINE 90 100 VX VY
NORMALLY
ASPIRATED ENGINE
SHP VARYING
WITH ALTITUDE
MP VARYING WITH
ALTITUDE
CONSTANT
SHPCONSTANT MP
FIGURE 26-1 - RATE OF CLIMB AND SPEEDS
27. SECTION 23.67 CLIMB: ONE ENGINE INOPERATIVE.
a. Explanation.
(1) Performance Matrix. For all multiengine airplanes, § 23.67 requires the one-engineinoperative climb performance be determined in the specified configuration. The requirements of § 23.67 are summarized in Table 27-1.
(2) Range of Tests. The primary objective of the climb tests associated with this requirement is to establish the airplane's climb performance capability with one engine inoperative for altitudes between sea level and 10,000 feet or higher and temperatures from ISA to ISA + 30 47
°C. This is necessary to enable comparison with the prescribed climb requirement at 5,000 feet altitude and for AFM presentation of climb performance data for altitudes and temperatures as prescribed in § 23.1587. Secondary objectives are:
(i) To establish the climb speed to be used in the cooling tests required by § 23.1041 through § 23.1047, including the appropriate speed variation with altitude; and
(ii) To establish the speed for best rate of climb (or for minimum descent, as appropriate) that, regardless of the speed used in demonstrating compliance with climb and cooling requirements, is required for presentation in the AFM in accordance with § 23.1587(c)(5).
(3) WAT Charts. For airplanes with an MTOW greater than 6,000 pounds and all turbine-powered airplanes, a WAT chart is an acceptable means to meet the performance requirements. See discussion in paragraph 8 of this AC.
Regulation 23.67(a)(1) 23.67(a)(2) 23.67(b)(1) 23.67(b)(2) 23.67(c)(1) 23.67(c)(2) 23.67(c)(3) 23.67(c)(4) Category Normal, Utility, and Aerobatic Commuter Engine Type and Airplane Weight Recip 6000 lbs or less Recips > 6000 lbs and Turbines VSO (kts) >61 ≤61 Power On Operative Engine ≤ MCP ≤MCP MTOP ≤MCP MTOP MTOP ≤MCP MTOP Configuration Flap and gear retracted Flap and gear retracted Take-off flap, gear retracted Flap and gear retracted Take-off flap, gear extended Take-off flap, gear retracted Flap and gear retracted Approach flap*, gear retracted Propeller Position on Inop Engine Minimum drag Minimum drag Minimum drag Minimum drag Position it automatically and rapidly assumes Position it automatically and rapidly assumes Minimum drag Minimum drag Attitude Wings level Climb Speed ≥1.2VS1 ≥1.2VS1 Equal to that achieved at 50ft demonstrating
23.53 ≥1.2VS1 V2 V2 ≥1.2VS1 As in procedures but ≥1.5VS1 Altitude (ft) 5000 5000 400 1500 Take-off surface 400 1500 400 Required Climb Gradient (%) ≥1.5 No minimum but must determine steady climb/descent gradient Measurably positive ≥0.75 Measurably positive ≥2 ≥1.2 ≥2.1
* Approach position(s) in which VS1 does not exceed 110% of the VS1 for the related allengines-operating landing positions
TABLE 27-1 - WAT Chart 48
b. Procedure.
(1) Critical Engine. To accomplish these objectives, it is necessary that sawtooth climbs be conducted with the critical engine inoperative and with the prescribed configuration and power condition. The "critical-inoperative-engine" for performance considerations is that engine which, when inoperative, results in the lowest rate of climb. The critical engine should be determined by conducting a set of sawtooth climbs, one engine at a time.
(2) Test Technique. One-engine-inoperative climb tests should be conducted at airspeeds and at altitudes as outlined for all-engine climbs under § 23.65. The test technique and other considerations noted under § 23.65 also apply. In climb tests with one engine inoperative, however, trim drag can be a significant factor and one-engine-inoperative climb tests should be conducted on a steady heading with the wings laterally level or, at the option of the applicant, with not more than a 5 degree bank into the good engine in an effort to achieve zero sideslip. A yaw string or yaw vane is needed to detect zero sideslip. The AFM should describe the method used and the approximate ball position required to achieve the AFM performance.
c. Commuter Category Airplanes.
(1) Climb Gradient. The required climb gradients are specified in § 23.67(c).
(2) Climb Performance Methods. Climb performance should be determined in the configurations necessary to construct the net takeoff flight path and to show compliance with the approach climb requirements of § 23.67(c). Some net takeoff flight path conditions will require wings level climb data. See paragraph 22g(1). If full rudder with wings level cannot maintain constant heading, small bank angles into the operating engine(s), with full rudder, should be used to maintain a constant heading. For all other conditions, climb performance may be determined with up to a 5 degree bank into the good engine. Two methods for establishing the critical one-engine-inoperative climb performance follow:
(i) Method No. 1. Reciprocal heading climbs are conducted at several thrust-to-weight conditions from which the performance for the AFM is extracted.
(ii) Method No. 2. Drag polars and engine-out yaw drag data are obtained for expansion into AFM climb performance. See Appendix 2. Reciprocal heading check climbs are conducted to verify the predicted climb performance.
(3) Landing Gear Position. The climb performance tests with landing gear extended in accordance with § 23.67(c) should be conducted with the landing gear and gear doors extended in the most unfavorable in-transit drag position. It has been acceptable to consider that the critical configuration is associated with the largest frontal area. For the landing gear, it usually exists with no weight on the landing gear. For gear doors, it is usually with all the gear doors open. If it is evident that a more critical transitional configuration exists, such as directional rotation of the gear, testing should be conducted in that configuration. In all cases where the critical configuration occurs during a transition phase that cannot be maintained except by special or extraordinary procedures, it is permissible to apply corrections based on other test data or acceptable analysis.
(4) Cooling Air. If means, such as variable intake doors, are provided to control powerplant cooling air supply during takeoff, climb, and en route flight, they should be set in a position that will maintain the temperature of major powerplant components, engine fluids, and so forth, within the established limits. The effect of these procedures should be included in the climb performance of the airplane. These provisions apply for all ambient temperatures up to the highest operational temperature limit for which approval is desired.
(5) Power. See paragraph 22b.
28. SECTION 23.71 GLIDE (SINGLE-ENGINE AIRPLANES).
a. Explanation.
(1) Gliding Performance. Section 23.71 requires the optimum gliding performance to be scheduled, with the landing gear and wing flaps in the most favorable position and the propeller in the minimum drag position.
(2) Background. The primary purpose of this information is to provide the pilot with the airplane gliding performance. Such data will be used as an approximate guide to the gliding range that can be achieved, but they will not be used to the same degree of accuracy or commercial significance as many other aspects of performance information. Hence, some reasonable approximation in its derivation is acceptable.
b. Means of compliance.
(1) Engine-inoperative Tests. Clearly the simplest way of obtaining accurate data is to perform actual engine-inoperative glides. These tests should be carried out over an airfield, thereby permitting a safe landing to be made if the engine does not restart at the end of the test.
(i) Fixed-Pitch Propeller. Most likely, the propeller will be windmilling after the fuel is shut off. If this is the case and the propeller does not stop after slowing to the best glide speed, then the gliding performance should be based on a windmilling propeller. Stalling the airplane to stop the propeller from windmilling is not an acceptable method of determining performance because the procedure could cause the average pilot to divert attention away from the primary flight task of gliding to a safe landing.
(ii) Constant-speed/Variable-pitch Propeller Airplanes. For these propellers, the applicant may assume that the means to change propeller pitch is still operational and, therefore, the propeller should be set at the minimum drag configuration. For most installations, this will be coarse pitch or feather.
(2) Sawtooth Glides. A method of determining glide performance is sawtooth glides. These glides can be flown using the same basic procedures in § 23.65 of this guidance material. For simplification, the test need only be flown at an intermediate altitude and gross weight generating one speed for the pilot to use. The best lift over drag speed is frequently higher than the best rate of climb speed; therefore, the airspeed range to flight test may be bracketed around a speed 10 to 15 percent higher than the best rate of climb speed.
(3) Performance Data. A chart or table should be constructed for the AFM that presents the literal (over-the-ground) gliding distances for the altitude range expected in service, at the best demonstrated glide speed. As a minimum, a statement of nautical miles (NM) per 1,000 feet loss of altitude at the demonstrated configuration and speed at maximum takeoff weight (MTOW), standard day, no wind, should be given.
29. SECTION 23.75 LANDING.
a. Explanation.
(1) Purpose. The purpose of this requirement is to evaluate the landing characteristics and to determine the landing distance. The landing distance is the horizontal distance from a point along the flight path 50 feet above the landing surface to the point where the airplane has come to a complete stop, or to a speed of 3 knots for seaplanes or amphibians on water.
(2) Companion Requirements. Sections 23.143(a)(6), 23.153, 23.231, and 23.233 are companion requirements and, normally, tests to determine compliance would be accomplished at the same time. Additionally, the requirements of § 23.473 should be considered.
(3) Approach and Landing. The steady gliding approach, the pilot skill, the conditions, the vertical accelerations, and the airplane actions in § 23.75(a), (b), and (c) are concerned primarily with not requiring particularly skillful or abrupt maneuvers after passing the 50-foot point. The phrase "steady gliding approach," taken in its strictest sense, means power off.
However, it has generally been considered that some power may be used during a steady gliding approach to maintain at least 1.3 VS1 control sink rate on final approach. For those airplanes using power during approach, power may be decreased after passing the 50-foot point and there should be no nose depression by use of the longitudinal control. For those airplanes approaching with power off, the longitudinal control may be used as necessary to maintain a safe speed for flare. In both cases, there should be no change in configuration and power should not be increased. The landing distance and the procedure specified in the AFM are then based on the power used for the demonstration. The power used and the technique used to achieve the landing distances should be clearly stated in the AFM. This applies to portions of the approach prior to and after the 50-foot height. The airplane should be satisfactorily controllable when landing under the most unfavorable conditions to be encountered in service, including crosswinds, wet runway surfaces and with one engine inoperative. Demonstration of landing with an adverse crosswind of at least 0.2 VSO will be acceptable, and operation on wet (but not contaminated) runway surfaces may be simulated by disconnecting the nosewheel steering. The effect of weight on the landing distance due to its influence on controllability of reverse thrust should be considered.
(4) Landing Gear Loads. Sink rate at touchdown during landing distance determination should be considered and should not exceed the design landing gear loads established by § 23.473(d).
(5) Landing Distance Credit for Disking Drag and Reverse Thrust. Most turboprop installations embody provisions for reduction of propeller blade pitch from the "flight" regime to a "ground" regime to produce either a significant level of disking drag or reverse thrust or both, following touchdown on landing. For purposes of this discussion, disking drag is defined as not less than zero thrust at zero airspeed. Section 23.75(f) permits means other than wheel brakes to be used in determining landing distance, when the conditions specified in § 23.75(f) are met. Such disking drag or reverse thrust may be acceptable in showing compliance with § 23.75(f) provided the means is safe and reliable.
(i) 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.
For commuter category airplanes, § 23.1309 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.
Safe and reliable should also mean that it is extremely improbable that the system can mislead the flight crew or will allow asymmetric power settings, that is, 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 in the landing phase. Also, the approved performance data should be such that the average pilot can duplicate this performance by following the AFM procedures.
(ii) Safe. Compliance with the "safe" provisions of § 23.75(f)(1) will require an evaluation of the complete system, including operational aspects, to ensure no unsafe feature exists.
(iii) Disking Drag for Multiengine Installations with Flight Idle and Ground Idle.
Symmetrical power/thrust may be used, with power levers at flight-idle position during air run, and at ground-idle position after touchdown. Procedures for consistently achieving ground idle should be established to ensure that the operational pilot gets the power lever back to ground idle, thus providing consistent results in service. Two of the designs that have been found acceptable for ground-idle positioning are a dedicated throttle gate or tactile positioning of the throttle. In effecting thrust changes following touchdown, allowance should be made for any time delays that reasonably may be expected in service, or which may be necessary to assure that the airplane is firmly on the surface. See subparagraph b(2) for commuter category time delays. Associated procedures should be included in the AFM. If the disking drag or some other powerplant-related device has a significant effect on the landing distance, the effect of an inoperative engine should be determined and published in the AFM Performance Section.
(iv) Disking Drag for Single-Engine Installations with Flight Idle and Ground Idle.
Landing distances should be determined with the power levers at flight-idle position during air run, and at ground-idle position after touchdown. Procedures for consistently achieving ground idle should be established. Two of the designs that have been found acceptable for ground-idle positioning are a dedicated throttle gate or tactile positioning of the throttle. In effecting thrust changes following touchdown, allowance should be made for any time delays that reasonably may be expected in service, or which may be 52