Appendix 4 A4-10
(2) The weight of the airplane, the configuration, and the power and/or thrust shall be constant throughout each segment and shall correspond with the most critical condition prevailing in the particular segment.
(3) The segmental flight path shall be based on the airplane’s performance without ground effect.
(4) Segmental takeoff path data shall be checked by continuous demonstrated takeoffs to insure that the segmental path is conservative relative to the continuous path.
4T.117 Takeoff distance. The takeoff distance shall be the horizontal distance along the takeoff path from the start of the takeoff to the point where the airplane attains a height of 35 feet above the takeoff surface as determined in accordance with 4T.116.
4T.118 Climb; general. Compliance shall be shown with the climb requirements of sections 4T.119 and 4T.120 at all weights, altitudes, and ambient temperatures, within the operational limits established by the applicant for the airplane. The airplane’s center of gravity shall be in the most unfavorable position corresponding with the applicable configuration.
4T.119 All-engine-operating landing climb. In the landing configuration, the steady gradient of climb shall not be less than 4.0 per cent, with:
(a) All engines operating at the available takeoff power and/or thrust;
(b) A climb speed not in excess of 1.4 V S0.
4T.120 One-engine-inoperative climb.
(a) Takeoff; landing gear extended. In the takeoff configuration at the point of the flight path where the airplane’s speed first reaches V2, in accordance with section 4T.116 but without ground effect, the steady gradient of climb shall be positive with:
(1) The critical engine inoperative, the remaining engine(s) operating at the available takeoff power and/or thrust existing in accordance with section 4T.116 at the time the airplane’s landing gear is fully retracted;
(2) The weight equal to the airplane’s weight existing in accordance with section 4T.116 at the time retraction of the airplane’s landing gear is initiated;
(3) The speed equal to the speed V 2.
(b) Takeoff; landing gear retracted. In the takeoff configuration at the point of the flight path where the airplane’s landing gear is fully retracted, in accordance with section 4T.116 but without ground effect, the steady gradient of climb shall not be less than 2.5 percent for two-engine airplanes and not less than 3.0 percent for four-engine airplanes, with:
Appendix 4 A4-11
(1) The critical engine inoperative, the remaining engine(s) operating at the takeoff power and/or thrust available at a height of 400 feet above the takeoff surface and existing in accordance with section 4T.116;
(2) The weight equal to the airplane’s weight existing in accordance with section 4T.116 at the time the airplane’s landing gear is fully retracted;
(3) The speed equal to the speed V 2.
(c) Final takeoff. In the en route configuration, the steady gradient of climb shall not be less than 1.4 percent for two-engine air-planes and not less than 1.8 percent for four-engine airplanes, at the end of the takeoff path as determined by section 4T.116, with:
(1) The critical engine inoperative, the remaining engine(s) operating at the available maximum continuous power and/or thrust;
(2) The weight equal to the airplane’s weight existing in accordance with section 4T.116 at the time retraction of the airplane’s flaps is initiated;
(3) The speed equal to not less than 1.25 V S1.
(d) Approach. In the approach configuration such that VS1 does not exceed 1.10 VS0, the steady gradient of climb shall not be less than 2.2 percent for two-engine airplanes and not less than 2.8 percent for four-engine airplanes, with:
(1) The critical engine inoperative, the remaining engine(s) operating at the available takeoff power and/or thrust;
(2) The weight equal to the maximum landing weight;
(3) A climb speed in excess of 1.5 V S1.
4T.121 En route flight paths. With the airplane in the en route configuration, the flight paths prescribed in paragraphs (a) and (b) of this section shall be determined at all weights, altitudes, and ambient temperatures within the limits established by the applicant for the airplane.
(a) One engine inoperative. The one-engine-inoperative net flight path data shall be determined in such a manner that they represent the airplane’s actual climb performance diminished by a gradient of climb equal to 1.4 percent for two-engine airplanes and 1.8 percent for four-engine airplanes. It shall be acceptable to include in these data the variation of the airplane’s weight along the flight path to take into account the progressive consumption of fuel and oil by the operating engine(s).
(b) Two engines inoperative. For airplanes with four engines, the two-engine-inoperative net flight path data shall be determined in such a manner that they represent the airplane’s actual climb performance diminished by a gradient of climb equal to 0.6 percent. It shall be acceptable
Appendix 4 A4-12 to include in these data the variation of the airplane’s weight along the flight path to take into account the progressive consumption of fuel and oil by the operating engines.
(c) Conditions. In determining the flight paths prescribed in paragraphs (a) and (b) of this section, the conditions of subparagraphs (1) through (4) of this paragraph shall apply.
(1) The airplane’s center of gravity shall be in the most unfavorable position.
(2) The critical engine(s) shall be inoperative, the remaining engine(s) operating at the available maximum continuous power and/or thrust.
(3) Means for controlling the engine cooling air supply shall be in the position which provides adequate cooling in the hot-day condition.
(4) The speed shall be selected by the applicant.
4T.122 Landing distance. The landing distance shall be the horizontal distance required to land and to come to a complete stop (to a speed of approximately 3 knots in the case of seaplanes or float planes) from a point at a height of 50 feet above the landing surface. Landing distances shall be determined for standard temperatures at all weights, altitudes, and winds within the operational limits established by the applicant for the airplane. The conditions of paragraphs (a) through (f) of this section shall apply.
(a) The airplane shall be in the landing configuration. During the landing, changes in the airplane’s configuration, in power and/or thrust, and in speed shall be in accordance with procedures established by the applicant for the operation of the airplane in service. The procedures shall comply with the provisions of section 4T.111(c).
(b) The landing shall be preceded by a steady gliding approach down to the 50-foot height with a calibrated air speed of not less than 1.3 VS0.
(c) The landing distance shall be based on a smooth, dry, hard-surfaced runway, and shall be determined in such a manner that reproduction does not require exceptional skill or alertness on the part of the pilot. In the case of seaplanes or float planes, the landing surface shall be smooth water, while for skiplanes it shall be smooth dry snow. During landing, the airplane shall not exhibit excessive vertical acceleration, a tendency to bounce, nose over, ground loop, porpoise, or water loop.
(d) The landing distance shall be corrected for not more than 50 percent of nominal wind components along the landing path opposite to the direction of landing and not less than 150 percent of nominal wind components along the landing path in the direction of landing.
(e) During landing, the operating pressures on the wheel braking system shall not be in excess of those approved by the manufacturer of the brakes, and the wheel brakes shall not be used in such a manner as to produce excessive wear of brakes and tires.
Appendix 4 A4-13
(f) If the Administrator finds that a device on the airplane other than wheel brakes has a noticeable effect on the landing distance and if the device depends upon the operation of the engine and the effect of such a device is not compensated for by other devices in the event of engine failure, the landing distance shall be determined by assuming the critical engine to be inoperative.
4T.123 Limitations and information.
(a) Limitations. The performance limitations on the operation of the airplane shall be established in accordance with subparagraphs (1) through (4) of this paragraph. (See also sec.
4T.743.)
(1) Takeoff weights. The maximum takeoff weights shall be established at which compliance is shown with the generally applicable provisions of this regulation and with section 4T.120 (a), (b), and (c) for altitudes and ambient temperatures within the operational limits of the airplane (see subparagraph (4) of this paragraph).
(2) Landing weights. The maximum landing weights shall be established at which compliance is shown with the generally applicable provisions of this regulation and with sections 4T.119 and 4T.120(d) for altitudes and ambient temperatures within the operational limits of the airplane (see subparagraph (4) of this paragraph).
(3) Takeoff and accelerate-stop distances. The minimum distances required for takeoff shall be established at which compliance is shown with the generally applicable provisions of this regulation and with sections 4T.115 and 4T.117 for weights, altitudes, temperatures, wind components, and runway gradients, within the operational limits of the airplane (see subparagraph (4) of this paragraph).
(4) Operational limits. The operational limits of the airplane shall be established by the applicant for all variable factors required in showing compliance with this regulation (weight, altitude, temperature, etc.). (See secs. 4T.113(a) (1) and (b), 4T.118, 4T.121, and 4T.122.)
(b) Information. The performance information on the operation of the airplane shall be scheduled in compliance with the generally applicable provisions of this regulation and with sections 4T.116, 4T.121, and 4T.122 for weights, altitudes, temperatures, wind components, and runway gradients, as these may be applicable, within the operational limits of the airplane (see subparagraph (a)(4) of this section). In addition, the performance information specified in subparagraphs (1) through (3) of this paragraph shall be determined by extrapolation and scheduled for the ranges of weights between the maximum landing and maximum takeoff weights established in accordance with subparagraphs (a) (1) and (a) (2) of this section. (See also sec. 4T.743.)
(1) Climb in the landing configuration (see sec. 4T.119);
(2) Climb in the approach configuration (see sec. 4T.120(d));
Appendix 4 A4-14
(3) Landing distance (see sec. 4T.122).
Airplane Flight Manual
4T.743 Performance limitations, information, and other data.
(a) Limitations. The airplanes’ performance limitations shall be given in accordance with section 4T.123(a).
(b) Information. The performance information prescribed in section 4T.123(b) for the application of the operating rules of this regulation shall be given together with descriptions of the conditions, air speeds, etc. under which the data were determined.
(c) Procedures. For all stages of flight, procedures shall be given with respect to airplane configurations, power and/or thrust settings, and indicated air speeds, to the extent such procedures are related to the limitations and information set forth in accordance with paragraphs
(a) and (b) of this section.
(d) Miscellaneous. An explanation shall be given of significant or unusual flight or ground handling characteristics of the airplane.
In lieu of sections 40.70 through 40.78, 41-27 through 41.36(d), and 42.70 through
42.83, of Parts 40, 41, and 42 of the Civil Air Regulations, respectively, the following shall be applicable:
Operating Rules
40T.80 Transport category airplane operating limitations.
(a) In operating any passenger-carrying transport category airplane certificated in accordance with the performance requirements of this regulation, the provisions of sections 40T.80 through 40T.894 shall be complied with, unless deviations therefrom are specifically authorized by the Administrator on the ground that the special circumstances of a particular case make a literal observance of the requirements unnecessary for safety.
(b) The performance data in the AFM shall be applied in determining compliance with the provisions of sections 40T.81 through 40T.84. Where conditions differ from those for which specific tests were made compliance shall be determined by approved interpolation or computation of the effects of changes in the specific variables if such interpolations or computations give results substantially equaling in accuracy the results of a direct test.
40T.81 Airplane’s certificate limitations.
Appendix 4 A4-15
(a) No airplane shall be taken off at a wei ght which exceeds the takeoff weight specified in the AFM for the elevation of the airport and for the ambient temperature existing at the time of the takeoff. (See sec. 4T.123(a) (1) and 4T.743(a).)
(b) No airplane shall be taken off at a weight such that, allowing for normal consumption of fuel and oil in flight to the airport of destination, the weight on arrival will exceed the landing weight specified in the AFM for the elevation of the airport of destination and for the ambient temperature anticipated there at the time of landing. (See secs. 4T.123(a) (2) and 4T.743(a).)
(c) No airplane shall be taken off at a weight which exceeds the weight shown in the AFM to correspond with the minimum distance required for takeoff on the runway to be used. The takeoff distance shall correspond with the elevation of the airport, the effective runway gradient, and the ambient temperature and wind component existing at the time of takeoff. (See secs.
4T.123(a) (3) and 4T.743 (a).)
(d) No airplane shall be operated outside the operational limits specified in the AFM (See secs. 4T.123(a) (4) and 4T.742(a)).
40T.82 Takeoff obstacle clearance limitations. No airplane shall be taken off at a weight in excess of that shown in the AFM to correspond with a takeoff path which clears all obstacles either by at least a height equal to (35 + 0.01D) feet vertically, where D is the distance out along the intended flight path from the end of the runway in feet, or by at least 200 feet horizontally within the airport boundaries and by at least 300 feet horizontally after passing beyond the boundaries. In determining the allowable deviation of the flight path in order to avoid obstacles by at least the distances prescribed, it shall be assumed that the airplane is not banked before reaching a height of 50 feet as shown by the takeoff path data in the AFM, and that a maximum bank thereafter does not exceed 15 degrees. The takeoff path considered shall be for the elevation of the airport, the effective runway gradient, and for the ambient temperature and wind component existing at the time of takeoff. (See secs. 4T.123(b) and 4T.743(b).)
40T.83 En route limitations.
(a) One engine inoperative. No airplane shall be taken off at a weight in excess of that which, according to the one-engine-inoperative en route net flight path data shown in the AFM, will permit compliance with either subparagraph (1) or subparagraph (2) of this paragraph at all points along the route. The net flight path used shall be for the ambient temperatures anticipated along the route. (See secs. 4T.123(b) and 4T.743(b).)
(1) The slope of the net flight path shall be positive at an altitude of at least 1,000 feet above all terrain and obstructions along the route within 5 miles on either side of the intended track.
(2) The net flight path shall be such as to permit the airplane to continue flight from the cruising altitude to an alternate airport where a landing can be made in accordance with the provisions of section 40T.84 (b), the net flight path clearing vertically by at least 2,000 feet all
Appendix 4 A4-16 terrain and obstructions along the route within 5 miles on either side of the intended track. The provisions of subdivisions (i) through (vii) of this paragraph shall apply.
(i) The engine shall be assumed to fail at the most critical point along the route.
(ii) The airplanes shall be assumed to pass over the critical obstruction following engine failure at a point no closer to the critical obstruction than the nearest approved radio navigational fix, except that the Administrator may authorize a procedure established on a different basis where adequate operational safeguards are found to exist.
(iii) The net flight path shall have a positive slope at 1,000 feet above the airport used as the alternate.
(iv) An approved method shall be used to account for winds which would otherwise adversely affect the flight path.
(v) Fuel jettisoning shall be permitted if the Administrator finds that the operator has an adequate training program, proper instructions are given to the flight crew, and all other precautions are taken to insure a safe procedure.
(vi) The alternate airport shall be specified in the dispatch release and shall meet the prescribed weather minima.
(vii) The consumption of fuel and oil after the engine becomes inoperative shall be that which is accounted for in the net flight path data shown in the AFM.
(b) Two engines inoperative. No airplane shall be flown along an intended route except in compliance with either subparagraph (1) or subparagraph (2) of this paragraph.
(1) No place along the intended track shall be more than 90 minutes away from an airport at which a landing can be made in accordance with the provisions of section 40T.84(b), assuming all engines to be operating at cruising power.
(2) No airplane shall be taken off at a weight in excess of that which, according to the two-engine-inoperative en route net flight path data shown in the AFM, will permit the airplane to continue flight from the point where two engines are assumed to fail simultaneously to an airport where a landing can be made in accordance with the provisions of section 40T.84(b), the net flight path having a positive slope at an altitude of at least 1,000 feet above all terrain and obstructions along the route within 5 miles on either side of the intended track or at an altitude of 5,000 feet, whichever is higher. The net flight path considered shall be for the ambient temperatures anticipated along the route. The provisions of subdivision (i) through (iii) of this subparagraph shall apply. (See secs. 4T.123(b) and 4T.743(b).)
(i) The two engines shall be assumed to fail at the most critical point along the route.
Appendix 4 A4-17
(ii) If fuel jettisoning is provided, the airplane’s weight at the point where the two engines are assumed to fail shall be considered to be not less than that which would include sufficient fuel to proceed to the airport and to arrive there at an altitude of at least 1,000 feet directly over the landing area.
(iii) The consumption of fuel and oil after the engines become inoperative shall be that which is accounted for in the net flight path data shown in the AFM.
40T.84 Landing limitations.
(a) Airport of destination. No airplane shall be taken off at a weight in excess of that which, in accordance with the landing distances shown in the AFM for the elevation of the airport of intended destination and for the wind conditions anticipated there at the time of landing, would permit the airplane to be brought to rest at the airport of intended destination within 60 percent of the effective length of the runway from a point 50 feet directly above the intersection of the obstruction clearance plane and the runway. The weight of the airplane shall be assumed to be reduced by the weight of the fuel and oil expected to be consumed in flight to the airport of intended destination. Compliance shall be shown with the conditions of subparagraphs (1) and (2) of this paragraph. (See secs. 4T.123(b) and 4T.743(b).)
(1) It shall be assumed that the airplane is landed on the most favorable runway and direction in still air.
(2) It shall be assumed that the airplane is landed on the most suitable runway considering the probable wind velocity and direction and taking due account of the ground handling characteristics of the airplane and of other conditions (i.e., landing aids, terrain, etc.).
If full compliance with the provisions of this subparagraph is not shown, the airplane may be taken off if an alternate airport is designated which permits compliance with paragraph (b) of this section.
(b) Alternate airport. No airport shall be designated as an alternate airport in a dispatch release unless the airplane at the weight anticipated at the time of arrival at such airport can comply with the provisions of paragraph (a) of this section, provided that the airplane can be brought to rest within 70 percent of the effective length of the runway.
Special Civil Air Regulation No. SR-422A
Adopted: July 2, 1958 Effective: July 2, 1958
(Paragraphs numbered 1 to 24a.(1) in pages A4-18 to A4-25 are for reference purposes only.)
Turbine-Powered Transport Category Airplanes of Current Design
1. On July 23, 1957, the Board adopted Special Civil Air Regulation No. SR-422 which sets
Appendix 4 A4-18 forth airworthiness requirements applicable to the type certification and operation of turbinepowered transport category airplanes for which a type certificate is issued after August 27, 1957.
Included in that regulation was a new set of performance requirements, with respect to which the Board indicated that consideration would be given to any changes found necessary as a result of further study and experience. The preamble to SR-422 contains the relevant considerations leading to its promulgation and is considered to provide the basic background for this regulation.
2. Since the adoption of SR-422, considerable study has been devoted to the new performance requirements by all interested parties. As a result of these studies and of further experience gained in the design, certification, and operation of turbine-powered airplanes, certain issues with respect to SR-422 require re-evaluation. This regulation reflects the resolution of most of the outstanding issues in the light of the best information presently available to the Board.
3. The following provisions of this regulation di ffer from, or are additional to, the provisions of SR-422; Introductory paragraph; item 1; sections 4T.111(c);
4T.112;
4T.114 (b), (b)(1), (b)(4), and (c); introductory paragraph of 4T.116;
4T.116 (b), (c), (e), and (g);
4T.117;
4T.117a;
4T.119;
4T.120 (a), (a)(1), (b), (b)(1), (c), (c)(2), (c)(3), (d), and (d)(3);
4T.121 (a) and (b); introductory paragraph of 4T.122;
4T.122 (b), (f), and (g);
4T.123 (a)(1), (a)(2), (a)(3), and (b);
4T.743(c);
40T.81 (b) and (c); 40T.82;
40T.83 (a)(2)(iii), (b)(2), and (b)(2)(ii);
item 4;
and item 5.
Appendix 4 A4-19
4. Of these provisions, the following differ from those proposed in Civil Air Regulations Draft Release No. 58-6: sections 4T.111(c); 4T.112(a)(4);
4T.114 (b)(4), (c), (c)(2), (c)(3), and (c)(4);
4T.116 (c) and (e);
4T.117 (b)(1) and (b)(2);
4T.119(a);
4T.120(a); 40T.81(c) and 43T.11(c).
5. With respect to the applicability of this regulation, experience with certification under SR- 422 indicates that a lead time of about two months between the date of adoption of the regulation and the date of issuance of the type certificate should provide a reasonable period of time within which to show compliance with this regulation. In view of this, and in the interest of having uniform regulations applicable to most of the turbine-powered airplanes, this regulation applies to all such airplanes for which a type certificate is issued after September 30, 1958. Turbinepowered transport category airplanes for which a type certificate is issued on or prior to September 30, 1958, may comply with the provisions of this regulation in lieu of SR-422. If this option is exercised, it is intended that compliance be shown with all the provisions of this regulation and it is not intended to permit a showing of compliance with portions of this regulation and portions of SR-422.
6. The provisions of this regulation involve the following technical issues:
a. A substantive change is made by introducing an all-engines-operating takeoff in establishing the takeoff distance. Presently, the takeoff distance is based only on a one-engineout takeoff. To insure that an adequate margin of safety will exist for day-in and day-out operations, the minimum takeoff distance is being related to both the one-engine-inoperative distance now prescribed and to the distance with all engines operating, with a factor of 1.15 being applied to the latter.
b. There are also included important changes with respect to the speeds applicable to the takeoff path. The provisions of SR-422 prescribe that the airplane shall be accelerated on or near the ground to the speed V2. This provision has been subject to varying interpretations having a marked difference in effect on the resultant level of performance. The issue in this matter is whether or not the airplane should be permitted to lift off the runway at some speed below V2.
Because of the increased acceleration of turbine-powered airplanes, the tendency to overshoot the lift-off speed will be greater than on piston-engine airplanes and this tendency increases with the reduction in weight of the airplane. To restrict lift-off to the minimum takeoff safety speed V2 would unduly extend the takeoff distance in cases where such overshooting of speed occurs.
Such a restriction would be unnecessarily conservative and would not reflect realistic takeoff procedures.
Appendix 4 A4-20
c. For these reasons this regulation permits the airplane to lift off the ground at a speed lower than the V2 speed, but prescribes certain limiting conditions. The lift-off speed is related to a rotational speed VR which must not be less than 95 percent of the minimum V2 speed and must be 10 percent greater than a speed at which no hazardous characteristics are displayed by the airplane, such as a relatively high drag condition or a ground stall.
d. The V 2 speed has been re-defined to take into account the increment in speed arising from overshoot tendencies. Under the new definition, the minimum V2 speed corresponds with the minimum takeoff safety speed as now defined in SR-422. With respect to the takeoff path, the V2 speed is required to be attained prior to reaching a height of 35 feet above the takeoff surface and thus is related to the selection of the rotational speed. Further, there is a revision which requires V2 to be maintained as close as practicable at a constant value from the 35-foot point to a height of 400 feet above the takeoff surface. This speed is the speed at which the prescribed minimum takeoff gradients must be met.
7. There is introduced in this regulation the concept of unbalanced takeoff field lengths. SR- 422 does not preclude unbalancing of field lengths, provided that the unbalancing is within the length of the runway. Other countries have employed unbalancing with respect to so-ca1led “stopways” and “clearways.” It appears that United States operators ultimately will find it advantageous to resort to the use of unbalancing, but probably not to the same extent as practiced in other countries. On the premise that only clearways will be utilized, the amendments have been formulated accordingly. Clearways, as defined herein, are areas not suitable for stopping the airplane in the event of an aborted takeoff, but adequate to provide additional takeoff distance for climb-out. To safeguard operations utilizing clearways, there is introduced the concept of a takeoff run which operationally relates to the determination of the minimum runway length required. The takeoff run is defined as the greater of the horizontal distances along the takeoff path to a given point with one engine inoperative or with all engines operating, with a margin of 15 percent being added to the latter. The takeoff run is measured from the beginning of takeoff to a point equidistant between the point where the airplane lifts off and the point where a height of 35 feet is reached. The required runway length must not be less than the takeoff run nor less than the accelerate stop distance.
a. According to the definition given, a clearway is subjected to the control of the airport authorities. It is not intended, however, that there be ownership by the airport authorities of the area in which the clearway lies. The objective for requiring control by the airport authorities is to insure that no flight will be initiated using a clearway unless it is determined with certainty that no movable obstacle will exist within the clearway when the airplane flies over.
b. It is anticipated that the introduction of clearways will offer further possibilities of increasing the utility of existing airport facilities in this country. When such areas can be integrated into existing facilities, economical benefits will accrue to the community and the operators. In addition, since clearways are presently available at some of the airports in other countries, United States operators will have the opportunity of taking advantage of such facilities.
Appendix 4 A4-21
8. There are included changes with respect to the prescribed minimum altitude of 1,000 feet relative to the takeoff path and to the one-engine-inoperative and two-engine-inoperative requirements applicable to the vicinity of the airport. Heretofore, the Civil Air Regulations have incorporated the reference altitude of 1,000 feet in respect of performance criteria over the airport. Obscure as is the significance of this altitude operationally, the altitude of 1,500 feet has worldwide precedent of being used as the altitude above the airport at which, generally, IFR approaches are initiated and go-around procedures executed. For this reason, the changes made extend the takeoff path to a minimum altitude of 1,500 feet and make this altitude applicable to the prescribed performance criteria above the airport for the one- and two-engine-inoperative en route requirements.
9. It is not anticipated that these changes will create any problems with respect to the en route stages of flight; however, it is realized that a further extension of the takeoff path might add to the problem of obtaining accurate data on obstacles relatively distant from the airport. The Board finds that the extension of the flight path to 1,500 feet is warranted in light of the operational significance of this altitude and because the extended flight paths will provide more fully for adequate terrain clearance at the end of the takeoff path.
10. There is included a change with respect to the takeoff path whereby the takeoff flight path is established as starting from a 35-foot height at the end of the takeoff distance and a net takeoff flight is prescribed for operational use. This latter change is for consistency with the specification of net flight paths for the en route stages of flight and to simplify determination of obstacle clearances operationally. The net flight path is specified to be the actual flight path diminished by a gradient of 1.0 percent. It is intended that the net flight path be obtained from the gross flight path by simple geometric means.
11. The change in the altitude from 1,000 to 1,500 feet previously mentioned, as well as a reevaluation in other respects of some of the climb gradients in SR-422, justify certain changes.
The gradients of l.4 and 1.8 applicable to the takeoff path and the final takeoff climb are being reduced to 1.2 and 1.7 for two-engine and four-engine airplanes, respectively. In addition, the gradients 1.4 and 1.8 in the one-engine-inoperative en route case are being reduced to 1.1 and
1.6, respectively.
12. Changes are made with respect to the one-engine-inoperative takeoff climb by interrelating more realistically the prescribed airplane configuration, weight, and power. These changes, in effect, permit meeting the prescribed gradients of climb at slightly higher airplane weights than would be possible under the presently effective provisions.
13. There is included a change to the provisions applicable to the one-engine-inoperative takeoff climb with landing gear extended which increases the prescribed minimum gradient from substantially zero to 0.5 percent for four-engine airplanes. This change is made to attain consistency in the difference between gradients applicable to twins and fours.
14. Changes are incorporated in connection with the two-engine-inoperative en route requirement. Representations have been made that the gradient of 0.6 percent now prescribed is unduly conservative. On the other hand, it has been pointed out that the fuel requirements for