(a) Limitations. The performance limitations on the operation of the airplane shall be established in accordance with subparagraph (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 the takeoff climb provisions pre scribed in 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 the landing and takeoff climb provisions prescribed in sections 4T.119 and 4T.120 for altitudes and ambient temperatures, within the operational limits of the airplane (see subparagraph (4) of this paragraph).
(3) Accelerate-stop distance, takeoff distance, and takeoff run. 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(a) and with 4T.117(b) if the takeoff distance is intended to include a clearway, 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.115(d), 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.117a(b), 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));
(3) Landing distance (see sec. 4T.122).
AIRPLANE FLIGHT MANUAL 4T.743 Performance limitations, information, and other data.
(a) Limitations. The airplane’s 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. Procedures established in accordance with section 4T.111(c) shall be given to the extent such procedures are related to the limitations and information set forth in accordance with paragraphs (a) and (b) of this section. Such procedures, in the form of guidance material, shall be included with the relevant limitations or information, as applicable.
(d) Miscellaneous. An explanation shall be given of significant or unusual flight or ground handling characteristics of the airplane.
3. 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, respectively, of the Civil Air Regulations, 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.84 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 Airplane Flight Manual shall be applied in determining compliance with the provisions of sections 40T.81 through 40.84. 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.
(a) No airplane shall be taken off at a weight which exceeds the takeoff weight specified in the Airplane Flight Manual for the elevation of the airport and for the ambient temperature existing at the time of the takeoff. (See secs. 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 and to the alternate airports, the weight on arrival will exceed the landing weight specified in the Airplane Flight Manual for the elevation of each of the airports involved and for the ambient temperatures anticipated 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 at which, in accordance with the minimum distances for takeoff scheduled in the Airplane Flight Manual, compliance with subparagraphs (1) through (3) of this paragraph is shown. These distances shall correspond with the elevation of the airport, the runway to be used, 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).)
(1) The accelerate-stop distance shall not be greater than the length or the runway plus the length or the stopway if present.
(2) The takeoff distance shall not be greater than the length of the runway plus the length of the clearway if present, except that the length of the clearway shall not be greater than onehalf of the length of the runway.
(3) The takeoff run shall not be greater than the length of the runway.
(d) No airplane shall be operated outside the operational limits specified in the Airplane Flight Manua1 (See secs. 4T.123(a) (4) and 4T.743(a).)
40T.82 Takeoff obstacle clearance limitations. No airplane shall be taken off at a weight in excess of that shown in the Airplane Flight Manual to correspond with a net takeoff flight path which clears all obstacles either by at least a height of 35 feet vertically 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 net takeoff 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 net takeoff flight path data in the Airplane Flight Manual, and that a maximum bank thereafter does not exceed 15 degrees.
The net takeoff flight 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. All airplanes shall be operated in compliance with paragraph (a) of this section. In addition, no airplane shall be flown along an intended route if any place along the route is more than 90 minutes away from an airport at which a landing can be made in accordance with section 40T.84(b), assuming all engines to be operating at cruising power, unless compliance is shown with paragraph (b) of this section.
(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 Airplane Flight Manual, will permit compliance with either subparagraphs (1) or (2) of this paragraph at all points along the route. The net flight path shall have a positive slope at 1,500 feet above the airport where the landing is assumed to be made after the engine fails. 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 statute miles (4.34 nautical 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 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 terrain and obstructions along the route within 5 statute miles (4.34 nautical miles) on either side of the intended track. The provisions of subdivisions (i) through (vi) of this subparagraph shall apply.
(i) The engine shall be assumed to fail at the most critical point along the route.
(ii) The airplane 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) An approved method shall be used to account for winds which would otherwise adversely affect the flight path.
(iv) 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 ensure a safe procedure.
(v) The alternate airport shall be specified in the dispatch release and shall meet the prescribed weather minima.
(vi) The consumption of fuel and oil after the engine is assumed to fail shall be that which is accounted for in the net flight path data shown in the Airplane Flight Manual.
(b) Two engines inoperative. 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 Airplane Flight Manual, 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 clearing vertically by at least 2,000 feet all terrain and obstructions along the route within 5 statute miles (4.34 nautical miles) on either side of the intended track. The net flight path considered shall be for the ambient temperatures anticipated along the route. The provisions of subparagraphs (1) through
(5) of this paragraph shall apply. (See secs. 4T.123(b) and 4T.734(b).)
(1) The two engines shall be assumed to fail at the most critical point along the route.
(2) The net flight path shall have a positive slope at 1,500 feet above the airport where the landing is assumed to be made after failure of two engines.
(3) 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 ensure a safe procedure.
(4) 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 1,500 feet directly over the landing area and thereafter to fly for 15 minutes at cruise power and/or thrust.
(5) The consumption of fuel and oil after the engines are assumed to fail shall be that which is accounted for in the net flight path data shown in the Airplane Flight Manual.
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 Airplane Flight Manual 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) amd 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.
4. In lieu of section 43.11 of Part 43 of the Civil Air Regulations the following shall be applicable.
43T.11 Transport category airplane weight limitations. The performance data in the Airplane Flight Manual shall be applied in determining compliance with the following provisions:
(a) No airplane shall be taken off at a weight which exceeds the takeoff weight specified in the Airplane Flight Manual for the elevation of the airport and for the ambient temperature existing at the time of the takeoff. (See secs. 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 and to the alternate airports, the weight on arrival will exceed the landing weight specified in the Airplane Flight Manual for the elevation of each of the airports involved and for the ambient temperatures anticipated 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 at which, in accordance with the minimum distances for takeoff scheduled in the Airplane Flight Manual,
compliance with subparagraphs (1) through (3) of this paragraph is shown. These distances shall correspond with the elevation of the airport, the runway to be used, 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.734(a).)
(1) The accelerate-stop distance shall not be greater than the length of the runway plus the length of the stopway if present.
(2) The takeoff distance shall not be greater than the length of the runway plus the length of the clearway if present, except that the length of the clearway shall not be greater than onehalf of the length of the runway.
(3) The takeoff run shall not be greater than the length of the runway.
(d) No airplane shall be operated outside the operational limits specified in the Airplane Flight Manual. (See secs. 4T.123(a) (4) and 4T.743(a).)
5. The following definitions shall apply:
(a) Clearway. A clearway is an area beyond the runway, not less than 500 feet wide, centrally located about the extended centerline of the runway, and under the control of the airport authorities. The clearway is expressed in terms of a clearway plane, extending from the end of the runway with an upward slope not exceeding 1.25 percent, above which no object nor any portion of the terrain protrudes, except that threshold lights may protrude above the plane if their height above the end of the runway is not greater than 26 inches and if they are located to each side of the runway.
NOTE: For the purpose of establishing takeoff distances and takeoff runs, in accordance with section 4T.117 of this regulation, the clearway plane is considered to be the takeoff surface.
(b) Stopway. A stopway is an area beyond the runway, not less in width than the width of the runway, centrally located about the extended centerline of the runway, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff: To be considered as such, a stopway must be capable of supporting the airplane during an aborted takeoff without inducing structural damage to the airplane. (See also sec. 4T.115(d) of this regulation.)
APPENDIX 2
HISTORICAL DEVELOPMENT OF ACCELERATE-STOP TIME DELAYS
1. Explanation.
a. As the rules pertaining to transport category airplane accelerate-stop distances have developed over the years, the interpretation of those rules, with regard to pilot actions, recognition times, and delay times, has also changed. The paragraphs below provide a historical perspective on the application of pilot recognition and delay times, with references to the applicable 14 CFR part 25 amendment number.
b. In accordance with the stipulations of §§ 21.101(a) and (b), the certification basis for a derivative airplane type may be the regulations specified in the type certificate of the basic airplane, depending upon the extent and nature of the changes to the airplane. For those cases where the original certification basis can be retained, the guidance presented in paragraphs 2a and b., below, may be used to show compliance with the appropriate regulations. (For more information related to determining a derivative airplane's certification basis, see FAA Order 8110.4A, "Type Certification Process.")
c. Regardless of the certification basis, the effects of brake wear state on energy absorption capability and stopping performance must be addressed. The responsible FAA Aircraft Certification Office (ACO) should be contacted to establish the applicable brake wear criteria for a specific airplane type.
2. Procedures .
a. Pre-Amendment 25-42 Accelerate-Stop Time Delays . Parts 1 and 25 of Title 14 of the CFR, prior to Amendments 1-29 and 25-42, respectively, defined V 1 as the critical engine failure speed. When this definition of V1 was applied to the accelerate-stop criteria of § 25.109 and the V 1 criteria of § 25.107(a)(2), the implication was that engine failure and engine failure recognition could occur simultaneously. It was recognized that this simultaneous occurrence could not be achieved in actual operations, and that defining V 1 as the engine failure speed resulted in a conflict with § 25.101(h), which requires allowance for time delays in execution of procedures. In order to resolve this conflict, V 1 was applied as the engine failure recognition speed, and appropriate time delays were developed for showing compliance with § 25.101(h). Figure 1 shows a pictorial representation of the accelerate-stop time delays that were considered acceptable for compliance with § 25.101(h) before Amendment 25- 42 (effective March 1, 1978). Paragraph b(1)(vii) of this appendix provides guidance on reflecting these time delays in the Airplane Flight Manual accelerate-stop distances.
FIGURE 1. ACCELERATE-STOP TIME DELAYS (Pre-Amendment 25-42)
(1) ∆trec = engine failure recognition time. The demonstrated time from engine failure to pilot activation of the first deceleration device, this action indicating recognition of the engine failure. For AFM data expansion purposes, in order to provide a recognition time increment that can be executed consistently in service, it has been found practical to use the demonstrated time or 1 second, whichever is greater. If the airplane incorporates an engine failure warning light, the recognition time includes the time increment necessary for the engine to spool down to the point of warning light activation, plus the time increment from light "on" to pilot action indicating recognition of engine failure.
(2) ∆ta1 = the demonstrated time interval between activation of the first and second deceleration devices.
(3) ∆ta2 = the demonstrated time interval between activation of the second and third deceleration devices.
(4) ∆t = a 1-second reaction time delay to account for in-service variations. If a command is required for another crewmember to actuate a deceleration device, a 2-second delay, in lieu of the 1-second delay, should be applied for each action. For automatic deceleration devices that are approved for performance credit for AFM data expansion, established times determined during certification testing may be used without the application of the additional time delays required by this paragraph.
(5) The sequence for activation of deceleration devices may be selected by the applicant in accordance with § 25.101(f). If, on occasion, the desired sequence is not achieved during testing, the test need not be repeated;
however, sufficient tests must be conducted to establish acceptable values of ∆ta.
(6) If additional devices are use d to decelerate the airplane, their respective demonstrated times, plus any additional required time delays, should be included until the airplane is in the full braking configuration.
(7) For the purpose of flight manual calculations, the 1-second del ay for each action may be added at the end of the total demonstrated time. Regardless of the manner in which the time delays are applied, the flight manual calculations must assume the airplane does not decelerate during the delay time increments.
b. Amendment 25-42 thru Amendment 25-91, Accelerate-Stop Time Delays . Amendment 25-42, effective March 1, 1978, introduced several new requirements affecting accelerate-stop distance determination. One of the most significant changes of Amendment 25-42 was the requirement to determine an all-engines-operating accelerate-stop distance to account for the many rejected takeoffs that were not the result of an engine failure.
Amendment 25-42 also introduced into the regulations an engine -failure speed, VEF; redefined the takeoff decision speed, V1; revised the accelerate -stop distance criteria to correspond to the V EF and V1 definitions; and added a 2- second time delay between V 1 and the first action to decelerate the airplane during which the airplane continues
accelerating with the operating engines at takeoff thrust. Figure 2 shows a pictorial representation of the acceleratestop time delays in accordance with the provisions of part 25, including Amendment 25-42:
FIGURE 2 ACCELERATE-STOP TIME DELAYS (Amendment 25-42 thru Amendment 25-91)
(1) ∆trec - § 25.107 defines the relationship between V EF and V1 as follows:
"VEF is the calibrated airspeed at which the critical engine is assumed to fail. V EF must be selected by the applicant, but may not be less than V MCG determined under §
25.149(e). V1 , in terms of calibrated airspeed, is the takeoff decision speed selected by the applicant; however, V 1 may not be less than V EF plus the speed gained with the critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's application of the first retarding means during accelerate-stop tests."
(2) Demonstrated engine failure recognition times less than 1 second should be carefully reviewed to assure the conditions under which they were obtained were representative of that which may reasonably be expected to occur in service. A sufficient number of demonstrations should be conducted using both applicant and FAA test pilots to assure that the time increment is representative and repeatable. The pilot's feet should be on the rudder pedals, not brakes, during demonstration tests.
(3) ∆ta1 = the demonstrated time interval between activation of the first and second deceleration devices.
(4) ∆ta2 = the demonstrated time interval between activation of the second and third deceleration devices.
(5) If a command is required for another crewmember to activate a deceleration device, a 1 -second delay, in addition to the delays specified in paragraphs (3) and (4) above, should be applied for each action. For automatic deceleration devices which are approved for performance credit for AFM data expansion, established system times determined during certification testing may be used. These established times cannot be assumed to
start until after the pilot action that triggers them; that is, they cannot be triggered before the first pilot action and, hence, cannot begin until at least 2 seconds after V 1.
(6) The sequence for activation of deceleration devices may be selected by the applicant in accordance with § 25.101(f). If, on occasion, the desired sequence is not achieved during testing, the test need not be repeated; however, sufficient tests must be conducted to establish acceptable values of ∆ta.
(7) Figure 2 shows a pictorial representation of how to apply time delays with up to three deceleration devices. If more than three devices are used to decelerate the airplane, the respective demonstrated time plus a 1-second reaction time delay should be included for each device beyond that represented pictorially in Figure 2 until the airplane is in the full braking configuration.
APPENDIX 3
CORRECTION OF AIR MINIMUM CONTROL SPEED TO STANDARD CONDITIONS The following analysis presents three methods of correcting a flight test derived value of air minimum control speed to standard conditions. These methods are applicable only to rudder deflection limited VMCA, for either jet or propeller driven airplanes. The effect of banking into the operating engine is accounted for, and the method will work with either fixed pitch or constant speed propellers, including the effects of windmilling drag. For rudder pedal force limited VMCA, see Appendix 4.
Theoretical Basis Given the static lateral/directional equations of motion for straight line, unaccelerated flight:
Fy∑ = 0 Cyb b⋅ + Cy aad d⋅ + Cy rrd d⋅ = CL · sin φ (1) Mx∑ = 0 Clb b⋅ + Cl aad d⋅ + Cl rrd d⋅ = 0 (2) Mz∑ = 0 Cnb b⋅ + Cn aad d⋅ + Cn rrd d⋅ = Cna (3) where:
CL = 295 2 ⋅ ⋅ W V Se Cna = 295 2 ⋅ ⋅ ⋅ ⋅ F l V S b na e e W = weight - lbs Ve = equivalent airspeed - kts S = wing area - ft2 Fna = asymmetric net thrust - lbs Fna = (Fn + Dw) for engine inoperative Fna = (Fn + Fi) for engine at idle Fn = net thrust of the operating engine - lbs Fi = idle engine net thrust - lbs Dw = windmill drag - lbs le = distance from aircraft center line to engine thrust line - ft b = wingspan - ft Constant Cn Method For the case where full rudder deflection is achieved, δr is a constant, and the system of equations can be resolved to an identity which shows that Cna is a linear function of CLsin φ.
Cna = A·CL ⋅ sinφ + B (4)
If it is assumed that test and standard day VMCA occur at the same angle of attack and bank angle, the asymmetric yawing moment coefficient will be constant, and V MCA can be corrected to standard conditions by the relationship:
VMCAs = VMCAt · F F na na s t for Turbojets VMCAs = VMCAt · THP THP s s t t ⋅ ⋅ s s 1 3 for Propeller driven where:
*THPs = Maximum AFM scheduled Brake/Shaft horsepower multiplied by sta ndard day propeller efficiency.
THPt = Test day brake/shaft horsepower where V MCA was achieved multiplied by test day propeller efficiency.
s s = Atmospheric density ratio at standard conditions.
s t = Atmospheric density ratio at test conditions.
*Windmilling SHP is not considered, because the current 14 CFR part 25 takeoff requirements for propeller driven airplanes result in such large performance penalties with a windmilling propeller that all part 25 turboprops to date have had autofeather installed.
Since both net thrust and shaft horsepower vary with speed, use of these equations will require an iterative solution.
Because this constant Cn method does not consider the effect on V MCA due to variations in bank angle, weight, sideslip angle, or adverse yaw, its use is limited to corrections of 5% or less in asymmetric net thrust or power.
For corrections beyond 5%, the relationship shown in equation (4) must be used, and enough flight test data must be obtained to define the correlation between Cna and CLsin φ.
Graphical Method In theory these data could be obtained by varying any combination of asymmetric thrust, airspeed, weight, and bank angle that would provide a representative variable set. However, since V MCA and stall speed are nearly coincident for most airplanes, there are some severe constraints on most of the variables. Typically, any reduction in maximum asymmetric thrust will cause V MCA to decrease below stall speed, and any increase in weight will cause stall speed to increase above VMCA; therefore, the only parameter that can reasonably be varied is bank angle.
To maximize the spread between stall and minimum control speed, V MCA tests are normally done at the lightest possible weight, at the maximum allowable asymmetric thrust (even with a short duration overboost, if the engine manufacturer will agree). At typical test altitudes (2000-3000 feet) and prototype gross weights, it will usually still not be possible to define V MCA with the full 5° bank, because of stall buffet.
To obtain the data necessary for extrapolation to the 5° bank limit, and to maximum asymmetric thrust, testing at three bank angles is required for the definition of the Cna vs CL sin φ relationship. These data should be obtained by shutting down the critical engine (normally the left), setting maximum allowable thrust on the operative engine, and slowing down while maintaining constant heading until full rudder deflection is achieved. The first point, a wings level condition, is easy to set up, and results in a speed well above stall buffet. A second point, at zero sideslip, will be achieved at approximately 2° - 3° bank (flown with a yaw string, or instrumented sideslip vane) and will provide an intermediate speed, still above buffet. The third data point is flown with as much bank angle that can be used without excessive buffeting (no more than would be accepted as the minimum level of stall warning). If necessary, an additional point can be obtained by banking 2° - 3° into the inoperative engine.