procedure must also be established with representative in-service characteristics. The method used for simulating engine failure must be representative of the power decay characteristics that will occur during a real, sudden engine failure and acceleration of the remaining engine(s). In order to cushion a rejected take- off, it is acceptable for the engine and transmission transient range to be entered in order to droop the rotor provided performance credit is not taken for this additional power above the maximum permitted rating and it can be shown that the engine(s) will remain within these limits in all conditions requested by the applicant. Any excursion beyond established transient limits in this flight phase should be substantiated to the extent that it does not constitute an immediate hazard to the rotorcraft.
(8) Turbine engine power does not vary directly with density altitude (HD). At a given HD, turbine engine power available varies with ambient temperature. Turbine engines typically produce less horsepower as ambient temperature is increased (pressure altitude decreases) at a given density altitude, although some engines produce less horsepower at extremely cold temperatures. In either event, if one test sequence is to be utilized for a given HD, it would be appropriate to restrict test power to the lowest value attainable from a minimum specification engine through the approved ambient temperature range at the density altitude of the test. To attain maximum weights for varying ambient conditions, the applicant may utilize a parametric mapping of power available, pressure altitude, and temperature effects. For this case, engine topping may be adjusted throughout a range appropriate to the test HD.
(9) Aircraft Loading. Both forward and aft CG extremes should be briefly checked to determine the critical loading for takeoff distances. Forward center of gravity is usually critical for continued takeoff distance tests while aft CG may be critical for the rejected takeoff due to forward and downward field of view. A minimum of two weights should be flown at each altitude if the manufacturer elects to schedule field length variation as a function of gross weight. One weight should be the maximum weight for prevailing conditions and the other weight(s) should be low enough to attain a sufficient spread to verify weight effect.
(10) Extrapolation. Takeoff and landing data may be extrapolated up to 4000 feet along an established W/σ line, to the maximum gross weight of the rotorcraft.
However, extrapolation will not be considered valid if unacceptable or marginally acceptable landing gear loads are experienced during testing at weights below the W/σ limit. See paragraph AC 29.77b(5) for further discussion of landing gear loads.
(11) Ambient Conditions. Appropriate test limits for ambient conditions such as wind and temperature are contained in paragraph AC 29.45. Test data should be corrected for existing wind conditions during takeoff distance testing. Credit for headwind conditions may be given during flight manual data expansion. Refer to paragraph AC 29.1587(a)(3)(iii) under “Wind Accountability” for allowable wind credit.
Care should be applied in considering headwind credit for vertical operations as previous experience has resulted in difficulty collecting meaningful, repeatable data.
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AC 29-2C, Chg 2 4/25/06
(12) Vertical Takeoffs.
(i) General. Guidelines for rotorcraft certification using vertical takeoff techniques were developed and utilized for civil certification programs many years ago.
As experience has been gained, certain policy decisions have modified these guidelines. The reader should be familiar with the preceding discussion regarding conventional Category A takeoff profiles because duplicate information is not repeated here.
(ii) Takeoff Profile. A ty pical vertical takeoff profile for a ground level heliport is shown in figure AC 29.59A-1. The maneuver begins with the addition of sufficient power to initiate a climb to the TDP. It should be possible to make a safe landing without exceptional pilot skill if an engine fails at any point up to the TDP less engine failure recognition time. At the TDP, the pilot becomes “go” oriented and continues the takeoff if an engine fails. The rotorcraft should not be allowed to descend below 15 feet above the takeoff surface during the continued takeoff. A typical profile for elevated heliports takeoff conditions is shown in figure AC 29.59A-2. Descent profile below the takeoff surface is allowed, after clearing the platform by at least a 15 feet radial margin, provided that the drop down height from the takeoff surface and the distance to reach VTOSS with a positive rate of climb is given in the performance chapter of the RFM.
(iii) Takeoff Decision Point (TDP). For vertical takeoffs, the climb to the TDP is nearly vertical, and the TDP is typically defined primarily by height. Sufficient testing should be conducted to define a band of TDP conditions (heights) which will be consistent with anticipated variations in pilot technique and the minimum amount of equipment to be installed on the production aircraft. Rejected takeoffs are most critical from high TDP’s, and continued OEI takeoffs are most critical from low heights. Tests at the extremes of this band are intended to verify that the anticipated TDP band is safe and repeatable in service for reasonable variations in pilot technique. These extreme points should not be used for distance determination when averaging takeoff performance data.
(iv) Conduct of the Test. Vertical takeoff profiles should be flown from a pad simulating operational conditions because the sight picture may be critical to successful OEI operations, particularly for elevated heliports. At all points on the vertical takeoff flight path up to the TDP, the pilot, with reasonable head movement, shall be able to keep sufficient portions of two heliport boundaries (front and one side) or equivalent markings in view to achieve a safe landing in case of engine failure.
Normally, a minimum 1-second delay or pilot recognition time interval, whichever is greater, is applied after the EFP before pilot collective control corrections are allowed. If the rotorcraft incorporates an engine failure warning device, engine failure recognition should not be less than the time required for the engine to spool down and activate the device.
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(A) Establish the rejected takeoff distance as the horizontal distance from the rearmost point of the rotorcraft at the initiation of takeoff to the foremost point after the rotorcraft comes to a stop on the takeoff surface (including rotor tip path), assuming an engine failure in the vertical climb at the TDP.
(B) Establish the continued takeoff distance as the horizontal distance from lift-off to the point at which, following engine failure prior to the TDP, the rotorcraft achieves; for a ground level heliport, 35 feet above the takeoff surface and VTOSS with a positive rate of climb; for an elevated heliport, the lowest point of the takeoff profile and not less than VTOSS with a positive rate of climb. The continued takeoff profile from elevated heliports should clear the heliport obstructions by at least a 15 feet radial margin.
(C) When used, the back-up technique usually requires the pilot to keep sufficient portions of the helipad in view and involves a rearward movement from the takeoff point to the TDP. In such cases the rearward horizontal distance required should be established as the distance from the rearmost point of the rotorcraft at the initiation of takeoff to the rearmost part of the rotorcraft at TDP. As stated in AC 29.45, crosswinds and tailwinds should be considered if requested by the applicant. Typically, this will require flight-testing to evaluate performance, pilot workload, field-of-view, and visual cueing.
(D) If special helipad markings or other non-standard external references are required to achieve the vertical takeoff performance, these special references should be included in the limitations section of the RFM.
(v) Climb Requirements.
(A) Ground level heliport. The OEI takeoff profile should include a climb at VTOSS to 200 feet above the takeoff surface then an acceleration in level flight from VTOSS to VY and a climb at VY to 1000 feet above the lowest point of the takeoff profile.
The climb requirements of § 29.67(a)(1) and (a)(2) may be met at referenced points located respectively at 200 feet and 1000 feet above the takeoff surface. The distance required to accelerate from VTOSS to VY must be considered in determination of the climb gradient required by § 29.1587 (a)(6)(i) and (a)(6)(ii).
(B) Elevated heliport. The OEI takeoff profile should include a climb at VTOSS to 200 feet above the lowest point of the takeoff profile then an acceleration in level flight from VTOSS to VY and a climb at VY to 1000 feet above the lowest point of the takeoff profile. The climb requirements of § 29.67(a)(1) and (a)(2) may be met at referenced points located respectively at 200 feet and 1000 feet above the lowest point of the takeoff profile.
(vi) Extrapolation. Basic guidelines for extrapolation are contained in paragraph AC 29.45. Weight can not be extrapolated above test weight. Altitude extrapolation should be limited to a maximum of ± 4000 feet.
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AC 29-2C, Chg 2 4/25/06
(13) Night Operations.
(i) A minimum of three normal takeoffs (and landings) should be conducted to ensure that aircraft lighting (internal and external) is adequate to allow normal Category A operations at night.
(ii) Engine failures should be simulated from points along the requested takeoff and landing profiles. Night OEI rejected takeoffs and continued takeoffs from the TDP and OEI landings from the LDP should be conducted at the requested WAT limiting conditions to ensure adequate night field of view, suitability of aircraft external lighting, and meets the Category A profiles.
(iii) If special airfield marking or lighting is used as a reference or to define the TDP, the aircraft external lighting should be evaluated to assure that the airfield marking or lighting is adequate for night operations.
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ALL ENGINE
CLIMBOUT
ACCELERATE TO VY
WHEN CLEAR OF OBSTACLES
OEI CLIMBOUT
ACCELERATE TO VrOSS TDP
VERTICAL CLIMB 15' FIGURE AC 29.59A-1 CATEGORY A VERTICAL TAKEOFF PROFILE
GROUND LEVEL HELIPORT Page B - 55
ALL ENGINE
CLIMBOUT
TDP ACCELERATE
TO VTOSS
VERTICAL CLIMB & 15 FEET
TAKEOFF PATH REJECTED MINIMUM OEI FLIGHT PATH 200 ft.
| V'TOSS | and positive , rate of
• climb Takeoff distance FIGURE AC 29.59A-2 CATEGORY A VERTICAL TAKEOFF
PROFILE ELEVATED HELIPORT Page B - 56
AC 29.63. § 29.63 (Amendment. 29-12) TAKEOFF: CATEGORY B.
a. Explanation.
(1) Takeoff distance is the horizontal distance measured from an initial position to a point 50 feet above the takeoff surface with all engines operating within approved limits.
(2) The height-velocity diagram is normally developed and accepted prior to conducting takeoff distance tests. Takeoff distance tests are conducted avoiding the critical areas of the diagram. The amount of power utilized in determining takeoff distance may not be greater than that used in constructing the takeoff corridor and “knee” portions of the height-velocity diagram. Power might also have to be constrained, depending upon the amount of excess power available, so that a “reasonable” nose down pitch attitude is not exceeded during the initial portion of the takeoff run. Acceptable values used during past programs include:
limits)
(i) Hover power + 10 percent (not to exceed rated engine takeoff power
(ii) A percent transmission limiting torque (not to exceed rated engine takeoff power limits), and
(iii) Engine (or transmission) limiting power for the particular ambient conditions.
(3) The critical center of gravity should be used for takeoff distance tests.
Critical center of gravity should be established analytically or from previous testing and may be forward or aft depending on the type of rotorcraft. Items that should be considered in determining the critical center of gravity are climb performance and cockpit visibility. At least two gross weights should be flown at each test altitude, if weight accountability is desired, in order to validate the manufacturers prediction of weight effects.
(4) The speed utilized at the 50-foot point in the takeoff profile (V50 speed) may be largely determined by the ability to obtain reliable, repeatable airspeed indications which can also comply with § 29.1323. Section 29.1323 ties the airspeed system accuracy requirements to the climbout speed. The climbout speed should be that speed attained at 50 feet in complying with § 29.63.
b. Procedures.
(1) Instrumentation. A ground station will measure ambient temperature, humidity (if applicable), and wind. For allowable wind conditions and engine power considerations refer to paragraph AC 29.45. A photo panel or hand recording method Page B - 57
may be utilized, as necessary, to record engine and flight parameters. A phototheodolite, takeoff and landing camera, or other approved instrumentation is utilized to measure distance, heights, speed, and time.
(2) Conduct of the Test. If the applicant elects to show weight effects on distance, at least two weights should be flown and, depending on the range of takeoff and landing altitudes to be approved, at least two test altitudes should be flown.
Altitudes should be sufficiently far apart to include a major portion of the approved takeoff and landing altitude range. Takeoff profiles should be started from an initial condition. For takeoffs from a hover, the hover height should be determined by performing fixed collective takeoffs as described in paragraph AC 29.51. “Takeoff” power should be smoothly applied and the aircraft nose lowered as necessary to accelerate without gaining excessive altitude. It must be possible to conduct a consistent takeoff profile clear of the height-velocity diagram with normal pilot effort and skill. A minimum of five good runs should be flown by the FAA/AUTHORITY pilot at each altitude and weight. Runs by the company and FAA/AUTHORITY pilot may be averaged. Effects of missing the V 50 speed by some amount (± 5 knots, for example) or other small changes in profile should be evaluated to determine if gross performance changes result from small piloting errors. Engine failures should be conducted along the takeoff profile to assure safe landing capability. Past programs have shown the low speed point immediately after addition of power to be particularly critical. Night takeoffs should at least be qualitatively evaluated to assure the takeoff procedures are compatible for night operation.
(3) Test Results. Test results are utilized in constructing the flight manual takeoff distance charts required by § 29.1587. The takeoff surface utilized in conducting these takeoff distance and engine failure tests should be included in the flight manual.
The “climbout speed” should also be defined and included in the flight manual. The airspeed utilized at the 50-foot point in the conduct of these tests must be clearly defined to allow compliance with § 29.1323. Test results may be extrapolated in accordance with guidance contained in paragraph AC 29.45.
(4) Test Techniques. For the FAA/AUTHORITY test data runs which will result in rotorcraft flight manual (RFM) performance, only the operational cockpit instrumentation as shown on the minimum equipment list and the piloting procedures from the RFM should be used. A useful technique is to “lead” the targeted V 50 speed by a fixed amount, so that a smooth, consistent, and operationally realistic transition may be made between the acceleration and climbout phases; e.g., begin rotation at 35 knots to achieve 46 knots passing 50 feet. This and other pertinent information defining the takeoff flight path are required flight manual entries per § 29.1587(b).
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TAKEOFF PROFILE
HEIGHT ABOVE GROUND (FEET) AVOID
• 5 KTS MINIMUM MARGIN AVOID
VELOCITY (KNOTS) FIGURE AC 29.63-1 CONVENTIONAL TAKEOFF PROFILE CATEGORY B Page B - 59
AC 29.65. § 29.65 (Amendment 29-15) CLIMB: (ALL ENGINES OPERATING).
a. Explanation.
(1) Section 29.65 requires in part that the steady rate of climb be determined for each Category B rotorcraft with maximum continuous power on each engine for the range of weights, altitudes, and temperatures for which certification is requested. The climb airspeed should be the best rate-of-climb (VY) for standard day sea level conditions at maximum weight and at a speed(s) selected by the applicant for other conditions not to exceed VNE. The applicant can either publish a climb schedule in accordance with the above or utilize a constant climb airspeed for all conditions.
Equivalent levels of safety have been found wherein the applicant was allowed to select a climb airspeed that was not the actual VY. The selected airspeed must be consistent with the speed used to show compliance with such items as cooling, stability, etc. The rate-of-climb resulting from the selected climb airspeed versus that from the actual VY shall not differ to an extent that a pilot will be encouraged, by appreciable increases in climb performance to fly a climb airspeed different from that published in the Flight Manual.
(2) For Category A rotorcraft, if VNE at any altitude is less than the maximum gross weight sea level standard day condition VY, the steady rate-of-climb must be determined at the climb speed(s) selected by the applicant not to exceed VNE. The climb performance must be determined from 2,000 feet below the altitude from where VNE intersects VY up to the maximum altitude for which certification is requested. This should be done utilizing maximum continuous power on each engine with the landing gear retracted.
b. Procedure to Determine VY.
(1) Sawtooth climbs may be used to determine the best rate-of-climb airspeed VY. If such a technique is used, climbs should be flown in pairs on opposite headings 90° to the winds at the test altitude. This procedure will minimize any windshear effects.
All testing should be done in smooth air. Windshear is usually an indication of unstable air or a temperature inversion and should be avoided. The climbs are flown on reciprocal headings for approximately 5 minutes through a 1,000-foot band, or a comparable time/altitude band, using maximum continuous power at a constant airspeed. Periodic power adjustments may be necessary. Additional reciprocal heading climbs must also be conducted at different airspeeds sufficient to bracket the lowest point of the power required versus airspeed curve. This technique can be repeated at different altitudes to obtain VY throughout the altitude range.
(2) Level flight performance (speed power) may also be used to determine the best rate-of-climb airspeed (VY). The testing should be done in smooth air. The advantage of this method is that less time is required, and the accuracy is equivalent to the sawtooth climb method. The test can be repeated at various altitudes to determine the VY throughout the altitude range desired for the rotorcraft. The test at each altitude Page B - 60
should be conducted at a constant weight over sigma (W/σ). The test is normally started at the desired W/σ with maximum continuous power, or at VNE, in level flight. A series of points should be taken, reducing airspeed 10 to 15 knots between points, with the lowest speed point at approximately 20 to 30 knots. Weight should be computed for each point and the test altitude adjusted to maintain a constant W/σ. After the data are reduced to standard day conditions, the minimum power required airspeed will be the VY speed.
(3) Prior to the flight test, the rotorcraft should be ballasted to the desired gross weight and the critical center of gravity. The airspeed should be stabilized prior to data acquisition. Data to be recorded includes time, altitude, airspeed, ambient temperature, engine parameters, torque(s), rotor RPM, fuel reading, aircraft heading, external configuration, etc. Power setting, weight, and climb airspeed should be planned prior to flight. For some turboshaft engines, temperature and/or engine speed limits may be reached prior to a limiting torque. The test team should verify that the resulting power utilized in these tests closely approximates the power producing capabilities of installed minimum specification engine.
c. Procedure to Determine all Engine Operating Climb Performance.
(1) Background. Continuous climbs are conducted at the appropriate climb airspeeds as outlined above in order to obtain the rotorcraft’s climb performance for the flight manual. By -products are a qualitative evaluation of the rotorcraft handling characteristics in a climb and engine data to assist in the determination of installed power available.
(2) Techniques. The techniques used to determine this performance may be the same as those used in the VY determination. The climbs are conducted on reciprocal headings at the established airspeed(s) through the target altitude range.
The same parameters are recorded. The rotorcraft will usually climb very rapidly during the first few thousand feet; therefore, the data acquisition method must be timely if accurate results are expected. This procedure is usually repeated at weight extremes.
The resulting data must then be corrected for power and weight. Power and weight corrections are satisfactory, provided the test powers and weights closely approximate the target values to make the weight and power corrections accurate. Once this data is finalized and corrected for all the flight test variables, interpolation for intermediate weights can be made with a high degree of reliability. If the rotorcraft has any stability augmentation system, vent systems, etc., which may influence the climb performance, then it must be accounted for. Caution should be taken that anti -ice, air-conditioning, etc., are not on unless the performance is being established specifically for those conditions.
AC 29.65A (AC 29.64) §§ 29.64 and 29.65 (Amendment 29-39) CLIMB (GENERAL AND ALL ENGINES OPERATING).
a. Explanation.
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(1) Amendment 29-39 relocated and clarified the general climb requirements into a new § 29.64 and added requirements to determine Category A climb performance in § 29.65. The guidance material presented in paragraph AC 29.67 does not apply to rotorcraft certified with Amendment 29-39 or later. Sections 29.64 and 29.65 require that the steady rate of climb be determined with maximum continuous power on each engine for the range of weights, altitudes, and temperatures for which certification is requested. The climb airspeed should be the best rate-of-climb (VY) for standard day sea level conditions at maximum weight and at a speed(s) selected by the applicant for other conditions not to exceed VNE. The applicant can either publish a climb schedule in accordance with the above or utilize a constant climb airspeed for all conditions.
Equivalent levels of safety have been found wherein the applicant was allowed to select a climb airspeed that was not the actual VY. The selected airspeed should be consistent with the speed used to show compliance with such items as cooling, stability, etc. The rate- of-climb resulting from the selected climb airspeed versus that from the actual VY shall not differ to an extent that a pilot will be encouraged by appreciable increases in climb performance to fly a climb airspeed different from that published in the Flight Manual.
(2) If VNE at any altitude is less than the maximum gross weight sea level standard day condition VY, the steady rate-of-climb should be determined at the climb speed(s) selected by the applicant not to exceed VNE. The climb performance should be determined from 2,000 feet below the altitude from where VNE intersects VY up to the maximum altitude for which certification is requested. This should be done utilizing maximum continuous power on each engine with the landing gear retracted.
b. Procedure to Determine VY.
(1) Sawtooth climbs may be used to determine the best rate-of-climb airspeed VY. If such a technique is used, climbs should be flown in pairs on opposite headings 90° to the winds at the test altitude. This procedure will minimize any windshear effects.
All testing should be done in smooth air. Windshear is usually an indication of unstable air or a temperature inversion and should be avoided. The climbs are flown on reciprocal headings for approximately 5 minutes through a 1,000-foot band, or a comparable time/altitude band, using maximum continuous power at a constant airspeed. Periodic power adjustments may be necessary. Additional reciprocal heading climbs should also be conducted at different airspeeds sufficient to bracket the lowest point of the power required versus airspeed curve. This technique can be repeated at different altitudes to obtain VY throughout the altitude range.
(2) Level flight performance (speed power) may also be used to determine the best rate-of-climb airspeed (VY). The testing should be done in smooth air. The advantage of this method is that less time is required, and the accuracy is equivalent to the sawtooth climb method. The test can be repeated at various altitudes to determine the VY throughout the altitude range desired for the rotorcraft. The test at each altitude should be conducted at a constant weight over sigma (W/σ). The test is normally Page B - 62