Appendix 3 A3-7
4. Equation Method
a. A single test day value of V MCA can also be corrected to standard conditions (using all the appropriate variables) without using this graphical method, provided either the slope of the Cna vs CLsin relationship is known (from wind tunnel, or analytical estimates), or one is willing to use a default (conservative) value. Thrust extrapolation using slope values not based on flight test is limited to 10% of the test day thrust. The following analysis shows the derivation of this single-point correction equation:
b. If the test day engine C na curve was added to the previous plot, it would be possible to see how far, and in what direction, the correction from test to standard day was made. Assuming that a single value of VMCA was determined at 3000 feet at a weight of 9000 lbs, a test day engine Cna curve could be plotted using the same technique used for the standard day curve, except substituting the 3000 ft thrust values from the engine spec:
Ve Fna Cna CLsin 70 2,634 0.073 0.204 90 2,589 0.043 0.123 110 2,554 0.029 0.082 130 2,528 0.02 0.059 150 2,510 0.015 0.044
c. The following C na vs CLsin plot shows the airframe curve, the standard day engine curve, and the test day curve:
Airframe .048 .052 Standard Day Engine Test Day Engine .124 .147
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09 0 0.05 0.1 0.15 0.2 0.25 CLsin Cna
From the airframe/engine curve intersections:
Appendix 3 A3-8
C nt = 0.052 C ns = 0.048
C Lsint = 0.147 C Lsins = 0.124
VMCAt = 82.4 kts VMCAs = 89.7 kts
d. This is a thrust correction of approximately 8%. If the constant C n method had been used, the test value of .052 would have applied, and the corresponding VMCAt would have been
85.7 kts, an error of 4 knots (5%) in the non-conservative direction.
e. Noting that the correction from test day to standard day is along the C n vs CLsin curve, which is a straight line, and denoting the slope of the airframe curve as K the intersection of the standard day thrust line with the airframe curve as Cns and CLsins, and the intersection of the test day thrust line with the airframe curve as Cnt and CLsint, the following equation can be derived:
Given the point-slope form of a straight line,
Y 2 - Y1 = m(X2 - X1)
Correspondingly,
C ns - Cnt = K (CLsins - CLsint )
C ns - K CLsins = Cnt - K CLsint
Fl qS b na e s s - K Ws i nqSsss FlqS bna et t K Ws i nqSttt
Substituting q = V295e2 and then multiplying through by VS295e2S
Fnas lbe - KWs sins = VVe 2 e 2 s t F lb KW s i nnat e tt
Appendix 3 A3-9
and finally,
VMCAs = VMCAt F lb KW s i n F lb KW s i n na e ss na e tt s t 1 2 for Turbojets
VMCAs = VMCAt 326 SHPV lb KW s i n 326 SHPV lb KW s i n SS S MCA e ss tt t MCAt e tt s 1 2 for Turboprops
In the simplified form of the lateral directional equations, K is CCny which is the directional static margin. The value of K typically varies from approximately 0.14 to 0.19, depending on the lateral/directional characteristics of the airplane being tested. As with the graphical method, if K is determined by flight test, thrust corrections to VMCA are based on an interpolation of flight test defined airframe capability, and there is no limit on the amount of the thrust correction to VMCA. A somewhat conservative default value of 0.20 for K may be used if flight test data is not available; however, in this case, any thrust extrapolation is limited to 10% of the test day thrust. To assure that corrections for bank angle and weight do not result in standard day VMCA values at or below stall speed, the corrections made by either the graphical or equation method should not result in a VMCA which is based on a CLsin that is greater than CLMAX sin5.
Appendix 4 A4-1
Appendix 4
History of Jet Transport Performance Standards
1. When the first jet transport airplanes were certificated in the late 1950’s, the applicable transport category airworthiness regulations were contained in part 4b of the Civil Air Regulations (CAR 4b). The airworthiness requirements of CAR 4b were developed from years of experience with propeller-driven airplanes powered by reciprocating engines. The different powerplant operating principles, and expanded speed and altitude envelopes of the first generation jet-powered airplanes required comprehensive changes to the performance requirements of CAR 4b. Special Civil Air Regulation No. SR-422 was adopted in July 1957 as a supplement to CAR 4b, containing airworthiness and operational requirements that were applicable to transport category airplanes powered by turbine engines (turbojet and turbopropeller).
2. As experience was gained, SR-422 was amended in July 1958 (SR-422A) and July 1959 (SR-422B) to better reflect the operating environment of these new airplane designs. These special civil air regulations, presented in this appendix, formed the basis for the current transport category airworthiness and operating performance regulations of parts 25, 121, and 135. Though the number of operational airplanes that were certificated to these requirements is continually decreasing, these special civil air regulations, and the related preamble material, still provide a worthwhile perspective on many of the issues behind the development of today’s regulations, and are therefore preserved for future reference in this appendix.
Appendix 4 A4-2 Special Civil Air Regulation No. SR-422
Effective: August 27, 1957 Adopted: July 23, 1957
(Paragraphs numbered 1 to 18.a.(1) in pages A4-2 to A4-5 are for reference purposes only.)
Turbine-Powered Transport Category Airplanes of Current Design
1. Part 4b of the Civil Air Regulations contains rules governing the design of transport category airplanes. For a number of years, this part has established airworthiness requirements for this category of airplanes by prescribing detailed provisions to be met for the issuance of a type certificate. However, the advent of turbine-powered airplanes (jets, turbo-props, etc.) has brought about operations at considerably higher speeds and altitudes than those involving reciprocating engine airplanes. These higher speeds and altitudes as well as certain inherent characteristics of turbine engines have introduced numerous new technical and design problems and have necessitated re-evaluation and amendment of many provisions in part 4b.
2. In recent years the Board has amended part 4b by introducing numerous technical provisions more specifically applicable to turbine-powered airplanes. These were included in amendments pertaining to structural, flight characteristic, powerplant installation, and other provisions. It is believed that part 4b as now written is applicable to turbine-powered airplanes with but one exception; namely, airplane performance. In the future, further amendments to this part, other than those relating to performance, will be comparatively minor in nature mainly reflecting the latest experience in the certification and operation of these airplanes.
3. The performance requirements presently in part 4b were first promulgated almost twelve years ago. They are now considered by the Board to be in a form not suitable for direct application to turbine-powered airplanes.
4. The administrator of Civil Aeronautics is in receipt of a large number of applications for type certification of turbine-powered airplanes. However, the so-called “non-retroactive” clause of section 4b.11(a) of part 4b does not make applicable to a particular airplane type any amendment which is adopted after an application is filed by the manufacturer for type certification of that airplane. Thus, most of these airplanes are not now required to meet some of the latest effective provisions of part 4b unless the Board prescribes otherwise. With so many applications for type certificates pending, it is essential that the Board establish adequate requirements which will effectively apply to the type certification of turbine-powered transport category airplanes. This Special Civil Air Regulation is being promulgated for that purpose.
5. This Special Civil Air Regulation is being made effective with respect to all turbinepowered transport category airplanes not yet certificated. In essence, it prescribes a revised set of performance requirements for turbine-powered airplanes and incorporates such of the recent amendments to part 4b as the Administrator finds necessary to insure that the level of safety of turbine-powered airplanes is equivalent to that generally intended by part 4b.
Appendix 4 A4-3
6. The performance requirements contained herein include not only the performance requirements necessary for the certification of an airplane, but also the complementary performance operating limitations as applicable under Parts 40, 41, and 42 of the Civil Air Regulations. In promulgating this new performance code, the Board intends that the resulting level of safety will be generally similar to the level of safety established by the performance code as expressed by the provisions now contained in Parts 4b and 40 (or 41 or 42 as appropriate) for reciprocating engine airplanes. To attain this, many of the performance provisions have been modified for better applicability to turbine-powered airplanes, some in the direction of liberalization, others in the direction of improvement in the required performance.
7. A significant change being made is the introduction of full temperature accountability in all stages of performance, except the landing distances required. The introduction of full temperature accountability will insure that the airplane’s performance is satisfactory irrespective of the existing atmospheric temperature. The performance requirements heretofore applicable did not give sufficient assurance in this respect.
8. The reason for omitting the direct application of temperature accountability in the requirement for landing distances is that this stage of performance always has been treated in a highly empirical fashion whereby temperature effects are taken into account indirectly together with the effects of other operational factors. Long range studies on rationalization of airplane performance so far have not yielded a satisfactory solution to the landing stage of performance.
The Board hopes, however, that continued studies will result in a solution of this problem in the near future.
9. The introduction of full temperature accountability has necessitated a complete reevaluation of the minimum climb requirements. Since the prescribed climb must now be met at all temperatures rather than to be associated with standard temperature, the specific values of climb have been altered. In each instance, the change has been in the downward direction because, although the previous values were related to standard temperature, a satisfactory resultant climb performance was attained at temperatures substantially above standard. While values of minimum climb performance specified in the new code will tend to increase the maximum certificated weights of the airplane for the lower range of temperatures, they will limit these weights for the upper range of temperatures, giving adequate assurance of satisfactory climb performance at all temperatures.
10. In considering the various stages of flight where minimum values of climb have been heretofore established, the Board finds that in two of the stages (all-engines-operating en route and one-engine-inoperative en route) the establishment of minimum values of climb is unnecessary because, in the case of the all-engines-operating stage, it has been found not to be critical and the case of the one-engine-inoperative stage is now more effectively covered by the en route performance operating limitations.
11. Considering that the minimum climbs being prescribed affect mainly the maximum certificated weights of the airplane but not the maximum operating weights, the Board, in adopting the new performance code, places considerable emphasis on the ability of the airplane to clear obstacles on takeoff and during flight. To this end, criteria for the takeoff path, the en
Appendix 4 A4-4 route flight paths, and the transition from takeoff to the en route stage of flight have been prescribed to reflect realistic operating procedures. Temperature is fully accounted for in establishing all flight paths and an expanding clearance between the takeoff path and the terrain or obstacles is required until the en route stage of flight is reached.
12. In order to insure that the objectives of the prescribed performance are in fact realized in actual operations, the manufacturer is required to establish procedures to be followed in the operation of the airplane in the various conditions specified in the regulation. These procedures, each designed for a specific airplane, will permit the operator to utilize the full performance capabilities of the airplane more readily than if the regulations prescribed all-inclusive procedures. The use of these procedures in determining compliance with the requirements governing takeoff, en route, and landing stages, will also add considerable flexibility to the regulation.
13. The new performance requirements established more clearly than heretofore which of the performance limitations are conditions on the airworthiness certificate of the airplane. In addition to the maximum certificated takeoff and landing weights, there are included limitations on the takeoff distances and on the use of the airplane within the ranges of operational variables, such as altitude, temperature, and wind. Since these limitations are in the airworthiness certificate, they are applicable to all type operations conducted with the airplane.
14. The new performance code contains values for minimum climb expressed as gradients of climb, in percent, rather than as rates of climb, in feet per minute, as has been the case heretofore. The Board believes that the gradient of climb is more direct in expressing the performance margins of the airplane. Use of the gradient eliminates the influence of the stalling speed on the required climb. Heretofore, higher rates of climb were required for airplanes with higher stalling speeds. The only differentiation in the new code with respect to the required climb is between two and four-engine airplanes. This type of differentiation is of long standing in the regulations, being applicable to the one-engine-inoperative stage of flight. It is now being expanded to the takeoff and approach stages.
15. The new performance requirements contained herein are based on the best information presently available to the Board. It is realized, however, that due to the present limited operating experience with turbine-powered transport airplanes, improvement in the requirements can be expected as a result of the direct application of the code to specific designs of new airplanes.
There are certain areas in the new requirements where additional refinement of details might be advisable. This is so particularly in the case of the requirements pertaining to the landing stage of flight. It is anticipated that, after further study of the regulation and especially after its application in the design, certification, and operation of forthcoming turbine-powered airplanes, the desirability of changes may become more apparent. It is the intent of the Board to consider without delay such changes as might be found necessary. Only after the provisions of this Special Civil Air Regulation are reasonably verified by practical application will the Board consider incorporating them on a more permanent basis into Parts 4b, 40, 41, and 42 of the Civil Air Regulations.
Appendix 4 A4-5
16. This Special Civil Air Regulation is not intended to compromise the authority of the Administrator under section 4b.10 to impose such special conditions as he finds necessary in any particular case to avoid unsafe design features and otherwise to insure equivalent safety.
17. Interested persons have been afforded an opportunity to participate in the making of this regulation (21 F.R. 6091), and due consideration has been given to all relevant matter presented.
18. In consideration of the foregoing, the Civil Aeronautics Board hereby makes and promulgates the following Special Civil Air Regulation, effective August 27, 1957.
a. Contrary provisions of the Civil Air Regul ations notwithstanding, all turbine-powered transport category airplanes for which a type certificate is issued after the effective date of this Special Civil Air Regulation shall comply with the following:
(1) The provisions of part 4b of the Civil Air Regulations, effective on the date of application for type certificate; and such of the provisions of all subsequent amendments to part 4b, in effect prior to the effective date of this special regulation, as the Administrator finds necessary to insure that the level of safety of turbine-powered airplanes is equivalent to that generally intended by part 4b.
In lieu of sections 4b.110 through 4b.125, and 4b.743 of part 4b of the Civil Air Regulations, the following shall be applicable:
Performance
4T.110 General.
(a) The performance of the airplane shall be determined and scheduled in accordance with, and shall meet the minima prescribed by, the provisions of sections 4T.110 through 4T.123. The performance limitations, information, and other data shall be given in accordance with section 4T.743.
(b) Unless otherwise specifically prescrib ed, the performance shall correspond with ambient atmospheric conditions and still air. Humidity shall be accounted for as specified in paragraph (c) of this section.
(c) The performance as affected by engine power and/or thrust shall be based on a relative humidity of 80 percent at and below standard temperatures and on 34 percent at and above standard temperatures plus 50°F. Between these two temperatures the relative humidity shall vary linearly.
(d) The performance shall correspond with the propulsive thrust available under the particular ambient atmospheric conditions, the particular flight conditions, and the relative humidity specified in paragraph (c) of this section. The available propulsive thrust shall correspond with engine power and/or thrust not exceeding the approved power and/or thrust less the installational losses and less the power and/or equivalent thrust absorbed by the accessories
Appendix 4 A4-6 and services appropriate to the particular ambient atmospheric conditions and the particular flight condition.
4T.111 Airplane configuration, speed, power, and/or thrust; general.
(a) The airplane configuration (setting of wing and cowl flaps, air brakes, landing gear, propeller, etc.), denoted respectively as the takeoff, en route, approach, and landing configurations, shall be selected by the applicant except as otherwise prescribed.
(b) It shall be acceptable to make the airplane configurations variable with weight, altitude, and temperature, to an extent found by the Administrator to be compatible with operating procedures required in accordance with paragraph (c) of this section.
(c) In determining the accelerate-stop distances, takeoff flight paths, takeoff distances, and landing distances, changes in the airplane’s configuration and speed, and in the power and/or thrust shall be in accordance with procedures established by the applicant for the operation of the airplane in service, except as otherwise prescribed. The procedures shall comply with the provisions of subparagraphs (1) through (3) of this paragraph.
(1) The Administrator shall find that the procedures can be consistently executed in service by crews of average skill.
(2) The procedures shall not involve methods or the use of devices which have not been proven to be safe and reliable.
(3) Allowance shall be made for such time delays in the execution of the procedures as may be reasonably expected to occur during service.
4T.112 Stalling speeds.
The minimum steady flight speed at which the airplane is controllable, in
(a) The speed V S0 shall denote the calibrated stalling speed, in knots, with:
(1) Zero thrust at the stalling speed, or engines idling and throttles closed if it is shown that the resultant thrust has no appreciable effect on the stalling speed;
(2) If applicable, propeller pitch controls in the position necessary for compliance with subparagraph (1) of this paragraph;
(3) The airplane in the landing configuration;
(4) The center of gravity in the most unfavorable position within the allowable landing range;
Appendix 4 A4-7
(5) The weight of the airplane equal to the weight in connection with which V S is being used to determine compliance with a particular requirement.
(b) The speed V S1 shall denote the calibrated stalling speed, or the minimum steady flight speed at which the airplane is controllable, in knots, with:
(1) Zero thrust at the stalling speed, or engines idling and throttles closed if it is shown that the resultant thrust has no appreciable effect on the stalling speed;
(2) If applicable, propeller pitch controls in the position necessary for compliance with subparagraph (1) of this paragraph; the airplane in all other respects (flaps, landing gear, etc.) in the particular configuration corresponding with that in connection with which VS1 is being used;
(3) The weight of the airplane equal to the weight in connection with which V S1 is being used to determine compliance with a particular requirement.
(c) The stall speeds defined in this section shall be the minimum speeds obtained in flight tests conducted in accordance with the procedure of subparagraphs (1) and (2) of this paragraph.
(1) With the airplane trimmed for straight flight at a speed of 1.4 V S and from a speed sufficiently above the stalling speed to insure steady conditions, the elevator control shall be applied at a rate such that the airplane speed reduction does not exceed one knot per second.
(2) During the test prescribed in subparagraph (1) of this paragraph, the flight characteristics provisions of section 4b.160 of part 4b of the Civil Air Regulations shall be complied with.
4T.113 Takeoff; general
(a) The takeoff data in sections 4T.114 through 4T.117 shall be determined under the conditions of subparagraphs (1) and (2) of this paragraph.
(1) At all weights, altitudes, and ambient temperatures within the operational limits established by the applicant for the airplane.
(2) In the configuration for takeoff (see sec. 4T.111).
(b) Takeoff data shall be based on a smooth, dry, hard-surfaced runway, and shall be determined in such a manner that reproduction of the performance does not require exceptional skill or alertness on the part of the pilot. In the case of seaplanes or float planes, the takeoff surface shall be smooth water, while for skiplanes it shall be smooth dry snow. In addition, the takeoff data shall be corrected in accordance with subparagraphs (1) and (2) of this paragraph for wind and for runway gradients within the operational limits established by the applicant for the airplane.
Appendix 4 A4-8
(1) Not more than 50 percent of nominal wind components along the takeoff path opposite to the direction of takeoff, and not less than 150 percent of nominal wind components along the takeoff path in the direction of takeoff.
(2) Effective runway gradients.
4T.114 Takeoff speeds.
(a) The critical-engine-failure speed V 1, in terms of calibrated air speed, shall be selected by the applicant, but shall not be less than the minimum speed at which controllability by primary aerodynamic controls alone is demonstrated during the takeoff run to be adequate to permit proceeding safely with the takeoff using average piloting skill, when the critical engine is suddenly made inoperative.
(b) The minimum takeoff safety speed V 2, in terms of calibrated air speed, shall be selected by the applicant so as to permit the gradient of climb required in section 4T.120 (a) and (b), but it shall not be less than:
(1) 1.2 V S1 for two-engine propeller-driven airplanes and for airplanes without propellers which have no provisions for obtaining a significant reduction in the one-engineinoperative power-on stalling speed.
(2) 1.15 V S1 for propeller-driven airplanes having more than two engines and for airplanes without propellers which have provisions for obtaining a significant reduction in the one-engine-inoperative power-on stalling speed;
(3) 1.10 times the minimum control speed V MC , established in accordance with section 4b.133 of part 4b of the Civil Air Regulations.
(c) If engine failure is assumed to occur at or after the attainment of V 2 , the demonstration in which the takeoff run is continued to include the takeoff climb, as provided in paragraph (a) of this section, shall not be required.
4T.115 Accelerate-stop distance.
(a) The accelerate-stop distance shall be the sum of the following:
(1) The distance required to accelerate the airplane from a standing start to the speed V1;
(2) Assuming the critical engine to fail at the speed V 1, the distance required to bring the airplane to a full stop from the point corresponding with the speed V1.
(b) In addition to, or in lieu of, wheel brakes, the use of other braking means shall be acceptable in determining the accelerate-stop distance, provided that such braking means shall have been proven to be safe and reliable, that the manner of their employment is such that
Appendix 4 A4-9 consistent results can be expected in service, and that exceptional skill is not required to control the airplane.
(c) The landing gear shall remain extended throughout the accelerate-stop distance.
4T.116 Takeoff path. The takeoff path shall be considered to extend from the standing start to a point in the takeoff where a height of 1,000 feet above the takeoff surface is reached or to a point in the takeoff where the transition from the takeoff to the en route configuration is completed and a speed is reached at which compliance with section 4T.120(c) is shown, whichever point is at a higher altitude. The conditions of paragraphs (a) through (i) of this section shall apply in determining the takeoff path.
(a) The takeoff path shall be based upon procedures prescribed in accordance with section 4T.111(c).
(b) The airplane shall be accelerated on or near the ground to the speed V 2 during which time the critical engine shall be made inoperative at speed V1 and shall remain inoperative during the remainder of the takeoff.
(c) Landing gear retraction shall not be initiated prior to reaching the speed V 2
(d) The slope of the airborne portion of the takeoff path shall be positive at all points.
(e) After the V 2 speed is reached, the speed throughout the takeoff path shall not be less than V2 and shall be constant from the point where the landing gear is completely retracted until a height of 400 feet above the takeoff surface is reached.
(f) Except for gear retraction and propeller feathering, the airplane configuration shall not be changed before reaching a height of 400 feet above the takeoff surface.
(g) At all points along the takeoff path starting at the point where the airplane first reaches a height of 400 feet above the takeoff surface, the available gradient of climb shall not be less than
1.4 percent for two-engine airplanes and 1.8 percent for four-engine airplanes.
(h) The takeoff path shall be determined either by a continuous demonstration takeoff, or alternatively, by synthesizing from segments the complete takeoff path.
(i) If the takeoff path is determined by the segmental method, the provisions of subparagraphs (1) through (4) of this paragraph shall be specifically applicable.
(1) The segments of a segmental takeoff path shall be clearly defined and shall be related to the distinct changes in the configuration of the airplane, in power and/or thrust, and in speed.