AC 23-8C

/ / / / / ?--­ -- 11/16/2011 AC 23-8C Figure 11 - Takeoff Segments and Nomenclature GROUND ROLL 1st 2nd ACCELERATION FINAL

DOWN RETRACTION RETRACTED

TAKEOFF RETRACTING ENROUTE POSITION

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

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 FT HEIGHT > 1500 FT HEIGHT > 400 FT

HEIGHTS ARE

REFERENCED TO

RUNWAY ELEVATION AT

END OF TAKEOFF DISTANCE SEE NOTE SEE NOTE V2 SEGMENT*

LANDING GEAR FLAPS POWER

AIRSPEED

ENGINES

PROPELLER / FAN UP TO 400 FT 400 FT OR GREATER 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 12- Net Takeoff Flight Path 35' 35' Net Flight Path Level from Takeoff Surface >400' Obstacle Clearance

9. § 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 (refer to § 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 47

- 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 three minutes or 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 whic h 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 result s, 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 th e 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 13 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 five 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 14.

(4) Data Plotting. Sawtooth climb data is plotted on a graph using altitude and time as the basic parameters as shown in figure 13. After the sawtooth data has been plotted, draw in the mean altitude line. A tange nt 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 met hod of data reduction (refer to 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 14.

130 K CAS w 4800 Q ~ i= -' < w c:: ::, V, 4400 .,, w R:

Vinoi:c• 165 IC CAS 4000 V111in• 72 IC CAS

TIME MINUTES 11/16/2011 AC 23-8C

(6) Plotting of Corrected Data. After the observed data has been corrected to the desired standards, it can be plotted as shown in figure 14 with the rate of climb versus CAS at various density altitudes. It should be noted that the stall speed point s are not usually true stabilized zero rate-of-climb data points. However, the stall speed point s are useful in defining the asymptotic character of the left hand part of the curve.

Figure 13 - Observed Data

(7) Speed Schedule Data Points. From the curves of figure 14, 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 V X 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. (Note: V MIN as used here is not related to the VMIN in stall testing.)

(8) Speed and Rate of Climb. Directly from information obtained from figure 14, 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 15, it is possible to determine the rate of climb from sea level to the absolute ceiling.

(9) Cowl Flap and Mixture. For propeller equipped airc raft, cowl flaps should be in the position used for cooling tests. The mixtur e setting should be set to that used during the cooling test.

(10) Weight and C.G. For climb performance tests, th e 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 da ta 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 extra polating beyond altitudes that have not been verified by flight tests.

ii -----I-LL.

I al ::E :::i u LL.

0 w I- < D::

1000 800 600 400 200 61250 Ho 0 4000 Ho 0 9200 Ho 0 ~---~---..----...-.fllJ:i----.-.J.._--.-------.---~fJ½.----e~---i~-- 0 20 40 60 80 100 120 140 160 180

CALIBRATED AIRSPEED- KNOTS 11/16/2011 AC 23-8C Figure 14 - 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 airpla nes, 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, exhaust gas temperature (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.

10. § 23.66 Takeoff Climb, One Engine Inoperative. Section 23.66(1) for normal, utility, and acrobatic category airplanes greater than 6,000 pounds 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 51

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.

Figure 15 - Rate of Climb and Speeds

MP VARYING WITH

DENSITY ALTITUDE SHP VARYING

ALTITUDE 15,000 10,000 5,000 NORMAL

LY ASPIR AT ED REC IP. EN GINE -

FULLTHROTTLE TURBO CHA RGEDRECIP.ENGOINRE

TURB P O P E NGINE VX VY

NORMALLY

ASPIRATED ENGINE

WITH ALTITUDE

CONSTANT

SHPCONSTANT MP 90 100 500 1,000 1,500

AIRPSEED - KCASRATE-OF-CLIMB

11. § 23.67 Climb: One Engine Inoperative.

a. Explanation.

(1) Performance Matrix. For all multiengine airplanes, § 23.67 requires the one­ engine-inoperative climb performance be determined in the specified configuration. The requirements of § 23.67 are summarized in Table 6.

(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 °C. This is necessary to enable co mparison 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 52

(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. Refer to Table 6 for specific climb requirements summary.

Table 6 - WAT Chart 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(d)(1) 23.67(d)(2) 23.67(d)(3) 23.67(d)(4) Category Normal, Utility, and Aerobatic Normal, Utility, and Aerobatic Turbojets > 6,000 lbs and Commuter Engine Type and Airplane Weight Recip 6,000 lbs or less Recips > 6,000 lbs and Turboprops Turbojets 6,000 lbs or less VSO (kts) >61 61 Power On Operative Engine  MCP MCP MTOP 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 retracted Flap and gear retracted Take-off flap, gear extended Take-off flap, gear retracted Flap and gear retracted Approach flap1, 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 demon­ strating

23.53 1.2VS1 Equal to that achieved at 50ft demon­ strating

23.53 1.2VS1 V2 V2 1.2VS1 As in procedures but 1.5VS1 Altitude (ft) 5,000 5,000 400 1,500 400 1,500 Take-off surface 400 1,500 400 Required Climb Gradient (%) 1.50 No minimum but must determine steady climb/ descent gradient  1.00 0.75  1.20 0.75 Measurably positive2 2.003 1.204 2.105 Notes:

1 Approach position(s) in which VS1 does not exceed 110 percent of the VS1 for the related all-engines-operating landing positions.

2 Measured positively for two-engine airplanes,  0.3 percent for three-engine airplanes, or  0.5 percent for four-engine airplanes.

3 2.0 percent for two-engine airplanes, 2.3 percent for three-engine airplanes, 2.6 percent for four-engine airplanes.

4 1.2 percent for two-engine airplanes, 1.5 percent for three-engine airplanes, 1.7 percent for four-engine airplanes.

5 2.1 percent for two-engine airplanes, 2.4 percent for three-engine airplanes, 2.7 percent for four-engine airplanes.

6 MCP is maximum continuous power 54

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-engi ne" 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 five-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. Jet Aircraft > 6,000 pounds and Commuter Category Airplanes.

(1) Climb Gradient. The required climb gradient s are specified in § 23.67(d).

(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(d). Some net takeoff flight path conditions will require wings level climb data. Refer to paragraph 23.57g(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 five-degree bank into the good engine. Two methods for establishing the critical one-engine-inoperative climb performance follow:

(i) Method No. 1. Reciprocal heading clim bs 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. Refer to appendix 2. Reciprocal heading check climbs are conducted to verify the predicted climb performance.

(3) Landing Gear Position. The climb performance test s with landing gear extended in accordance with § 23.67(d) 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 critic al 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 55

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 in take 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. Refer to paragraph 23.57b.

12. § 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 inform ation 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 pr opeller 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.

(iii) Turbojet airplanes. Reserved.

(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 AC minus the power considerations. For simplific ation, 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 MTOW, standard day, no wind, should be given.

13. § 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 three 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 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. 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 abrupt maneuvers using 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 applie s to portions of the approach prior to and after the 50-foot height.

(4) Adverse Landing Conditions. 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 is addressed in § 23.233. Op erations on wet (but not contaminated) runway surfaces have been simulated by disconnecting the nosewheel steering on large part 23 airplanes. The effect of wei ght on the landing distance due to its influence on controllability of reverse thrust should be considered. The criticality of the adverse landing conditions should guide the level of complexity applicants use in determining controllability.

Existing flight test practices have proven adequate for propeller driven part 23 airplanes, but they may not be adequate for small jets. Additional guidance may be found in AC 25-7B. Part 23 jets typically have higher landing speeds and little drag to help slow the airplane. Landing 57