Appendix 9
(a) Production indicated airspeed, test indicated airspeed, and configuration.
(b) Correct the test indicated airspeed for instrument error and, in the case of electronic devices, any known dynamic effects. Static pressure in the bottle is assumed to result in no position error. These corrected airspeed values may be assumed to be CAS.
(c) Calculate the amount of system error (difference between corrected trapped static indicated airspeed and production indicated airspeed).
(d) Plot IAS versus CAS within the required range of speeds. See Figure A9-8 for a sample plot.
A9-23
lJ' V
V ,,, ,,, / I/ V V
V , ,,, / I/ V V , , ,, / 1,,1 V / , ,,, ,,, / I/ V / I' ,,, ,,, 11/16/2011 AC 23-8C Appendix 9 Figure A9-8 - Ground Airspeed Calibration 110
GROUND AIRSPEED
CALIBRATION 100 90 CAS KNOTS 80 70 60 50 40 40 50 60 70 80 90 100 110 120
IAS - KNOTS A9-24
Appendix 9
c. Distance Measuring Unit Method. The distance measuring unit method consists of utilizing the readouts of ground speed to obtain CAS values within the required range of speeds. These values are compared with readings at the same instant on a production airspeed indicator. Airspeed indicator readings may be recorded by film or video cameras for mechanical airspeed indicators or by electronic means if a transducer type device is being utilized. There should be a method of correlating recorded airspeeds with the CAS values obtained from the distance measuring unit system.
(1) Test Conditions.
(a) Air Quality. The surface wind velocity should be steady, as low as possible, and not exceed 10 knots. The wind direction should be as near as possible to the runway heading.
(b) Weight and C.G. Same as for the trapped static source method.
(c) Speed Range. Same as for the trapped static source method.
(2) Test Procedures.
(a) Align the airplane with the runway.
(b) Conduct a takeoff acceleration using normal takeoff procedures. The distance measuring unit should be recording/determining the ground speeds. The camera should be recording speeds from the production airspeed indicator and the time or counting device utilized to correlate speeds.
(c) The takeoff may continue or be aborted when beyond the maximum required speed.
(d) Record surface wind velocity and direction; surface air temperature and runway pressure altitude for each run.
(e) Repeat steps (a) through (d) of this paragraph until there are sufficient runs to provide adequate calibration curves for the required configurations.
(3) Data Acquisition and Reduction. Read the recorded data (film or video) at increments of airspeed arbitrarily selected within the required range. For these same increments, determine the ground speeds from the distance measuring unit system. See Table A9-3 for a sample data reduction. Record and perform the following:
A9-25
<--, TIME DMl WIND TAS (I) SHIP'S (2) SHIP'S CORRECTED (3) GROUND SPEED COMPONENT (KNOTS) CAS !AS AIRSPEED SHW'SIAS GROUND (KNOTS) DOWN THE (Ki'lOTS) (KNOTS) INSTRUMENT AIRSPEED
RUNWAY CORRECTION ERROR 07:00 :09 48.0 3 51.0 50.1 49 0 49 +LI :IO 52.8 I 55.8 54.8 54 I 54 +0.8 :II 56.8 I 59.8 58.7 59 I 59 -0.3 :12 61.0 I 64.0 62.8 63 I 63 -0.2 :13 64.2 I 67.2 66.0 68 I 68 -2.0 :14 67.3 I 70.3 69.0 71 I 71 -2.0 :15 70.9 I 73.9 72.5 75 I 75 -2.5 :16 74.0 I 77.0 75.6 78 I 78 -2.4 :17 77.2 I 80.2 78.7 82 I 82 .3.3 :18 80.7 I 83.7 82.2 83 I 83 -0.8 :19 83.9 I 86.9 85.3 87 I 87 .1.7 :20 87.0 I 90.0 88.3 89 I 89 -0.7 :21 90.6 I 93.6 91.9 92 I 92 -0.1 :22 93.8 I 96.8 95.1 95 I 95 +0.1 :23 96.9 I 99.9 98.1 101 I IOI -2.9 :24 100.3 I 103.3 101.4 103 I 103 -1.6 <--, :25 103.6 I 106.6 104.7 106 I 106 .IJ :26 106.6 V 109.6 107.6 110 V I IO -2.4 11/16/2011 AC 23-8CAppendix 9 Table A9-3 - Sample Ground Airspeed Calibration Using a Distance Measuring Unit Test Conditions:
Notes:
Pressure Altitude - 1240 ft. 1. CAS = TAS Temperature - 52 °F 2. Obtain from instrument calibration - 0.982 3. CAS minimum corrected Ship's IAS Runway - 1 4. Corrections must be added Wind - 350/3 A9-26
Appendix 9
(a) Production indicated airspeed, ground speed, surface air temperature, runway pressure altitude, wind velocity and wind direction with respect to runway heading.
(b) Compute a CAS value for each data point. This is accomplished by identifying the wind component parallel to the runway; computing the corresponding true airspeed; computing the air density ratio; then computing the calibrated airspeed.
(c) Calculate the amount of system error (difference between CAS and production indicated airspeed).
(d) Plot IAS versus CAS within the required range of speeds. See Figure A9-8 for a sample plot.
A9-27
Appendix 10 Appendix 10. Guide for Determining Clim b Performance After STC Modifications (not applicable to SFAR 23, SFAR 41, or to commuter category)
1. Introduction. Section 23.1587 requires certain performance information to be included in the AFM.
These include the climb requirements and rate of climb information as specified by §§ 23.69, and 23.77.
Additionally, some turbine-powered airplanes may have the maximum weight of § 23.1583(c) limited by climb performance. If an airplane is modified externally (and/or an engine change) and the changes are deemed significant enough to produce measurable effects, any appropriate requirements and information should be determined for inclusion in the AFM supplement.
2. General. Supplemental Type Certificates involve modifications to in-service airplanes that may, for one reason or other, not exactly match Type Design climb performance data that was determined and published in the AFM. These effects can be the resu lt of engine power deteriorations, added antennae, exterior surfaces not polished or smooth, propeller nicks, or a variety of other reasons. In addition, it is difficult and costly to obtain calibrations of engine power output that may have been available during the original certification process. The extent of performance degradation observed after incorporating external modifications could be partially due to deficiencies present in the airplane prior to modification.
In other instances, the results of performance measurements indicate that there is little or no effect from the modification, and the test airplane closely matches the values contained in the basic AFM even though analysis indicates some degradation. For either of these situations, the actual loss in performance could be skewed or masked by these other variables. For these reasons, any climb performance measurements conducted as part of an STC modification should be conducted such that the actual effects of the modification are identified. One effective means of accomplishing this is to measure the performance of the unmodified airplane then repeat the same tests with the external modifications incorporated. Any variations from the basic performance predictions due to engine power or other variables will be minimized or eliminated.
3. Procedure for Extending Climb Performance to Additional Airplanes. The conditions to be evaluated should be identified from a review of the applicable regulations and related to the modifications to be incorporated. The instruments that are to be involved in the flight tests should have recent calibrations. The airspeed system should be verified to be in agreement with the basic airplane calibrations.
Prior to modifications, conduct a series of climbs utilizing the general procedures and information presented in paragraphs 25, 26, and 28 of this Flight Test Guide. Test speeds and other conditions may be abbreviated to those that are presented in the AFM. The AFM can also be utilized as a guide to identify how climb performance is predicated to vary with altitude and other conditions. Results should be corrected to some standard in accordance with Appendix 2, or some other acceptable method. The before and after tests should be conducted, as nearly as possible, at the same airplane weight.
After the modification, the series of climbs conducted above should be repeated. Apply the same procedures and corrections as before. Corrected re sults of climbs before and after the modification should be compared by plotting the combined results. The performance in the AFM is useful in identifying how climb performance was predicated to change with altitude and temperature. It is likely that there will be some scatter and variations in the final results. With a limited amount of testing, the effects of the modification should be determined conservatively and identified in a manner suitable for presentation in the AFM supplement.
A10-1
Appendix 10
4. "One Only" Airplane. Often, there are circumstances where the full range of performance tests before and after the STC modification are not warranted. These might include:
a. A limited effectivity such as a one-only modification.
b. An excessively conservative reduction in published climb performance, which would not limit normal operations of the airplane and limitations are not affected.
The conditions to be evaluated should be identified from a review of the applicable regulations and related to the modifications to be incorporated. The instruments that are to be involved in the flight tests should have recent calibrations. The airspeed system should be verified to be in agreement with the basic airplane calibrations.
If the reduction in climb performance is not limiting, then it may be acceptable to conduct tests of the modified airplane only and provide analysis that could be used to support and compare with the tests.
Values of climb degradation should be selected that are sufficiently conservative to overcome any variations or discrepancies that may have been present. This should not involve any requirements of §
23.1583. The information required by § 23.1587, however, could be excessively conservative without degrading normal operations of the airplane in service.
For example, analysis predicts that a particular modification will reduce the one-engine-inoperative climb performance by 50 feet-per-minute, and limited testing shows a reduction of 30 feet-per-minute.
In order to overcome the introductory considerations and variables, a degradation in climb performance should be obviously conservative. The higher of the two rate of climb degradation values could be doubled to achieve this objective. For this example, the AFM supplement would reflect a degradation in one-engine-inoperative climb performance of 100 feet-per-minute.
A10-2