AC 29-2C, Chg 4 5/1/2014 discharge pressure are most likely to function and reduce power on a hot day at low altitude.
(C) The adjustments to the normal power assurance check procedures for deteriorated engines will be influenced by the preferences of the aircraft manufacturer and by any special stipulations of the engine certification region established as a condition for the engine to remain in service when below specification. Possibly, more stringent and more complicated procedures will be introduced for deteriorated power;
for example, an in-flight trend monitoring program with the associated bookkeeping duties may be required. Such an in- flight procedure must be evaluated by flight tests as described in paragraph b.(6) above. Normally, however, the manufacturer would be expected to present a modification, or extension of the power assurance procedure already in place for the specification engine, which could eliminate the need for flight test evaluation.
(D) If a complex power assurance procedure is presented with involved data reduction and trending requirements, consideration should be given to restricting the use of deteriorated power to operators where close control over operations is exercised or the operator has demonstrated the ability to operate safely with deteriorated engines.
(8) Engine Failure Testing Considerations
(i) For all tests to examine behavior following an engine failure, usually the failure of the engine is simulated in some way. For engines with a hydro-mechanical governing system, it is common practice to close the throttle quickly to idle. For rotorcraft equipped with a FADEC, and particularly those with a 2 minute/30 second OEI rating structure, it is common practice to simulate an OEI condition by using reduced power on all engines by means of a flight test tool.
(ii) In every case, it must be demonstrated that all aspects of rotorcraft and powerplant behavior are identical to those that would occur in the event of an actual engine failure with the remaining engine developing minimum-specification power. Of particular concern are “dead engine” power decay characteristics, “live engine” acceleration characteristics, and rotor RPM control.
(iii) To this end, it is expected that a number of actual engine shut down tests will be conducted to generate sufficient data to validate the fidelity of the flight test tool and methodology, which will then allow its use in developing regulatory performance data. In general, it is best to conduct the tests in a low hover with the rotorcraft stabilized below the HV low point. An engine is then shut down and, following the appropriate pilot intervention time, the collective is raised to cushion the landing.
Page B – 20
AC 29.45A. § 29.45 (Amendment 29-24) PERFORMANCE - GENERAL.
a. Explanation. Amendment 29-24 adds § 29.45(f) to the regulation. This section establishes the requirement for furnishing power assurance information for turbine powered aircraft. This information is to provide the pilot a means of determining, prior to takeoff, that each engine will produce the power necessary to achieve the performance presented in the RFM.
b. Procedures. All of the guidance material pertaining to AC section 27.45 remains in effect. In addition, the power assurance information included in the RFM should be verified. Although this requirement is normally met with a power assurance curve, other methods of compliance may be proposed.
AC 29.45B. § 29.45 (Amendment 29-24) PERFORMANCE - GENERAL.
a. Explanation. Although § 29.45 was not changed by Amendment 29-34, that amendment added requirements for certification of 30-second/2-minute OEI power ratings. For rotorcraft approved for the use of 30- second/2-minute OEI, partial power checks currently accomplished with approved power assurance procedures for lower power levels may not be sufficient to guarantee the ability to achieve the 30-second power level.
b. Procedures. MG 9 of this AC includes material on power assurance procedures to ensure that the OEI power level can be achieved. All of the guidance material pertaining to AC sections 29.45 and 29.45A remain in effect.
AC 29.45C. § 29.45 (Amendment 29-24) PERFORMANCE - GENERAL.
a. Explanation. Although § 29.45 was not changed by Amendment 29-51, that amendment added new performance and handling qualities requirements for transport category rotorcraft. Included within these regulatory changes is OGE handling qualities.
Additionally, hover performance requirements were re-identified from § 29.73 to § 29.49.
b. Procedures. All of the guidance material pertaining to AC sections 29.45,
29.45A, and 29.45B remain in effect. In addition, the following apply:
(1) OGE handling qualities may be extrapolated from test data up to a maximum of ±2,000 feet density altitude from the test altitude.
(2) Hover performance guidance that applied to § 29.73 is applicable to § 29.49.
Page B – 21
AC 29-2C, Chg 4 5/1/2014
CERTIFICATION BASIS 14 CFR pa rt 29 CAR 7 Rqms 29-Amdt. 21 29-Amdt. 1 Original Original HV CAT A Cat A & B (>9 Cat A: Cat A: Cat. A:
Ref. TEST pax seats): 1. MGW Sea 1. MGW Sea 1. MGW Sea
29.25 CONDITIONS 1. W.A.T. for Level Level Level
29.87 which t.o. and 2. Max. IGE 2. Max. IGE 2. Max. IGE wt.
29.1517 ldg. are wt. Max. wt. Max. Max.
29.1581 approved. alt. capability. alt. capability. alt. Capability.
29.1583 2. Failure of 3. Failure of 3. Failure of 3. Failure of
7.11 critical engine. critical engine. critical critical engine.
7.715 engine.
7.741 AC 29- CAT A 3. HV is 4. HV is 4. HV is 4. HV is 2C, RFM limitation. limitation. limitation. limitation.
Sections 4. Type of ldg. 5. Type of ldg. 5. Type of ldg. 5. Type of ldg.
29.45 & surface. Surface. surface. surface.
29.79 CAT B TEST
CONDITIONS Cat B (</=9 pax seats):
1. MGW Sea Level
2. Max. OGE wt. Max. alt.
Capability
3. Complete power failure, or failure of critical engine (w/eng isolation).
Cat B:
1. MGW Sea Level
2. Max. IGE wt. Max. alt.
Capability
3. Complete power failure, or failure of critical engine (w/eng isolation).
Cat B:
1. MGW Sea Level
2. Max. IGE wt. Max. alt.
Capability
3. Complete power failure, or failure of critical engine (w/eng isolation.)
Cat B:
1. MGW Sea Level
2. Max. IGE wt.
Max. alt.
Capability
3. Complete power failure, or failure of critical engine (w/eng isolation.)
CAT B 4. HV is perf. 4. HV is 4. HV is 4. HV is RFM Info.
5. Type of ldg.
surface.
limitation info.
5. Type of ldg.
Surface.
limitation info.
5. Type of ldg.
surface.
limitation info.
5. Type of ldg.
surface.
FIGURE AC 29.45-1. HV REQUIREMENTS Page B – 22
CERTIFICATION BASIS 14 CFR part 29 CAR 7 Requirement s 29-Amdt. 24 29-Amdt. 3 Original Original IGE
CONTROL Ref. 29.25
29.1583
7.121
7.743 AC 29-2C CAT A TEST
CONDITION S Cat A
1. W.A.T. for which
t.o. and ldg.
are approved.
2. Critical wt.
Critical CG Critical Nr
3. Wind not less than 17 kts.
1. Conditions selected by the applicant.
2. Critical CG Critical Nr
3. Wind not less than 17 kts.
1. Conditions selected by the applicant.
2. Critical CG Critical Nr
3. Wind not less than 20 mph.
1.
Conditions selected by the applicant.
2. Critical CG Critical NR
3. Wind not less than 20 mph.
CAT A 4. Max. 4. Max safe 4. Max safe 4. Max.
Sections
29.45 and
29.143 RFM allowable wind is limitation.
wind above max. alt. For which 17 kt.
Wind envelope is established is perf. info.
wind above alt.
for which 17 kt.
wind envelope is established is perf. info.
allowable wind above the altitude for which 20 mph wind envelope is est. is perf.
info.
CAT B Cat B:
TEST 1. W.A.T. for CONDITION which t.o. and S ldg. Are approved.
2. Critical wt.
Critical CG Critical Nr
3. Wind speed & quad selected by the applicant.
CAT B RFM
4. Max. safe wind is perf.
info.
FIGURE AC 29.45-2 IGE CONTROLLABILITY REQUIREMENTS Page B – 23
AC 29-2C, Chg 4 5/1/2014 600 500 CORRECTED SHAFT HORSEPOWER ENG S/N 12345 400 300 MIN CERTIFIED
SPECIFICATION ENGINE 200 100 1000 1100 1200 1300 1400 1500 CORRECTED TOT °F FIGURE AC 29.45-3 SHAFT HORSEPOWER VS TURBINE OUTLET
TEMPERATURE - SEA LEVEL STANDARD DAY Page B - 24
20 -30° to -50° 16 PRESSURE ALTITUDE - FEET (X 1000) 200 ЗОНІ 00 500
SHAFT HORSEPOWER AVAILABLE FIGURE AC 29.45-4 UNINSTALLED TAKEOFF POWER AVAILABLE Page B - 25
AC 29-2C, Chg 4 5/1/2014 20 10
TRANSMISSION PRESSURE ALTITUDE - FEET (X 1000) 200 300 400
SHAFT HORSEPOWER AVAILABLE FIGURE AC 29.45-5 INSTALLED TAKEOFF POWER AVAILABLE, ANTI-ICE OFF, 400 RPM Page B - 26
10000 FT B000 FT 2000 FT SEA LEVEL 80 100 PERCENT TORQUE EXAMPLE: OAT = 17.5°C TOT = 760° C Hp = 4000 FT REQUIRED TORQUE = 70% CONDITIONS: ZERO AIRSPEED RPM 100% ANTI-ICE OFF GENERATOR LOAD 100 AMPS OUTSIDE AIR TEMPERATURE - °C 800°C 760°C 740°C 720°C FIGURE AC 29.45-6 POWER ASSURANCE CHECK CHART Page B - 26.1
AC 29-2C, Chg 4 5/1/2014 AC 29.49. § 29.49 (Amendment 29-39) PERFORMANCE AT MINIMUM OPERATING SPEED.
(For performance at minimum operating speed and for hover performance prior to Amendment 29-39, see § 29.73 and section 29.73 of this AC.)
a. Explanation.
(1) Amendment 29-39 re-designated § 29.73 as § 29.49 to relocate the requirements for rotorcraft hover performance. For the purpose of this manual, the word “hover” applies to a rotorcraft that is airborne at a given altitude over a fixed geographical point regardless of wind. Pure hover is accomplished only in still air.
(2) Under § 29.49, hover performance should be determined at a height consistent with the takeoff procedure for category A rotorcraft and in ground effect (IGE) for category B rotorcraft. Additionally, out of ground effect (OGE) hover performance should be determined for both category A and B rotorcraft. Hover OGE is that condition, where an increase in height above the ground will not require additional power to hover. Hover OGE is the absence of measurable ground effect. It can be less than one rotor diameter at low gross weight increasing significantly at high gross weights. The lowest OGE hover height at gross weight may be approximated by placing the lowest part of the vehicle 1 ½ rotor diameters above the surface.
(3) The objective of hover performance tests is to determine the power required to hover at different gross weights, ambient temperatures, and pressure altitudes.
Using non-dimensional power coefficients (Cp) and thrust coefficients (Ct) for normalizing and presenting test results, a minimum amount of data are required to cover the rotorcraft’s performance operating envelope.
(4) Hover performance tests must be conducted over a sufficient range of pressure altitudes and weights to cover the approved ranges of those variables for takeoff and landings. Additional data should be acquired during cold ambient temperatures, especially at high altitudes, to account for possible Mach effects.
(5) The minimum hover height for which data should be obtained and subsequently presented in the flight manual should be the same height consistent with the minimum hover height demonstrated during the takeoff tests. Refer to section 29.51 of this AC for the procedure to determine the minimum allowable hover height.
b. Procedures.
(1) Two methods of acquiring hover performance data are the tethered and free flight techniques. The tethered technique is accomplished by tethering the rotorcraft to the ground using a cable and load cell. The load cell and cable are attached to the ground tie-down and to the rotorcraft cargo hook. The load cell is used to measure the rotorcraft’s pull on the cable. Hover heights are based on skid or wheel height above Page B – 26.2
the ground. During tethered hover tests, the rotorcraft should be at light gross weight.
The rotorcraft will be stabilized at a fixed power setting and rotor speed at the appropriate skid or wheel height. Once the required data are obtained, power should be varied from the minimum to the maximum allowed at various rotor RPM. This technique will produce a large Ct/Cp spread. The load cell reading is recorded for each stabilized point. The total thrust the rotor produces is the rotorcraft’s gross weight, weight of the cables and load cell plus cable tension. Care must be taken that the cable tension does not exceed the cargo hook limit or load capacity of the tie-down. For some rotorcraft, it may be necessary to ballast the rotorcraft to a heavy weight in order to record high power hover data.
(2) The pilot maintains the rotorcraft in position so that the cable and load cell are perpendicular to the ground. To insure the cable is vertical, two outside observers, one forward of the rotorcraft and one to one side, can be used. Either hand signals or radio can be used to direct the pilot. The observers should be provided with protective equipment. This can also be accomplished by attaching two accelerometers to the load cell which sense movement along the longitudinal and lateral axes. Any displacement of the load cell will be reflected on instrumentation in the cockpit and by reference to this instrumentation, the rotorcraft can be maintained in the correct position. Accurate load cell values may also be obtained by measuring cable angles and, through geometry, determining a corrected load cell value. Increased caution should be utilized as tethered hover heights are decreased because the rotorcraft may become more difficult to control precisely. The tethered hover technique is especially useful for OGE hover performance data because the rotorcraft’s internal weight is low and the cable and load cell can be jettisoned in the event of an engine failure or other emergency.
(3) To obtain consistent data, the wind velocity should be 3 knots or less. Large rotorcraft with high downwash velocities may tolerate higher wind velocities. The parameters usually recorded at each stabilized condition are:
(i) Engine and transmission torque.
(ii) Rotor speed.
(iii) Ambient and engine temperatures, such as measured gas temperature (MGT).
(iv) Pressure altitude.
(v) Fuel used (or remaining).
(vi) Load cell reading.
(vii) Generator(s) load.
(viii) Wind speed and direction.
Page B – 27
AC 29-2C, Chg 4 5/1/2014
(ix) Hover height.
As a technique, it is recommended the rotorcraft be loaded to a center of gravity (CG) near the hook to minimize fuselage angle changes with varying powers. All tethered hover data should be verified by a limited spot-check using the free flight technique.
The free flight technique in paragraph b.(4) below will determine if any problems, such as load cell malfunctions, have occurred. The free flight hover data must fall within the allowable scatter of the tethered data.
(4) If there are no provisions or equipment to conduct tethered hover tests, the free flight technique is also a valid method. The disadvantage of this technique as the primary source of data acquisition is that it is very time consuming. In addition a certain element of safety is lost OGE in the event of emergency. The rotorcraft must be reballasted to different weights to allow the maximum Ct/Cp spread. When using the free flight technique, either as a primary data source or to substantiate the tethered technique, the same considerations for wind, recorded parameters, etc., as used in the tethered technique apply. Free flight hover tests should be conducted at CG extremes to verify any CG effects. If the rotorcraft has any stability augmentation system, which may influence hover performance, it must be accounted for.
(5) Comprehensive hover performance tests are typically conducted at low, intermediate (approximately 7000 feet HD), and high altitude test sites with prepared landing surfaces, in conjunction with takeoff, landing, controllability, and maneuverability testing. Alternatively, a predicted hover performance model developed for high altitude may be used if verified by limited flight testing. The extrapolation guidelines in section
29.45.b.(2) of this AC are still applicable. These higher altitude hover tests could typically be conducted in conjunction with the limited controllability tests. If the applicant is able to demonstrate to the approving airworthiness authority a method to provide a reliable hover reference, it is acceptable to conduct OGE tests without ground reference.
Page B – 28
AC 29.51. § 29.51 TAKEOFF DATA - GENERAL.
a. Explanation. Section 29.51 details the conditions under which takeoff performance data can be obtained and presented in the FAA/AUTHORITY approved flight manual. The flight manual must also contain the technique(s) to be used to obtain the published flight manual takeoff performance. Technique should not be confused with exceptional pilot skill and/or alertness as mentioned in § 29.51. Rotorcraft are different from one another and due to this, different pilot techniques are sometimes required to achieve the safest and most optimum takeoff performance. The recommended technique that is published in the flight manual and used to achieve the performance must be determined to be one that the operational pilot can duplicate using the minimum amount of type design cockpit instrumentation and the minimum crew.
b. Background.
(1) Certain special takeoff techniques are necessary when a rotorcraft is unable to takeoff vertically because of altitude, weight, power effects, or operational limitations.
The recommended technique used to take off under such conditions is to accelerate the rotorcraft in-ground-effect (IGE) to a predetermined airspeed prior to climbout. Takeoff tests are performed to determine the best repeatable technique(s) for a particular rotorcraft over the range of weight, altitude, and temperature for which certification is requested.
(2) The primary factor which determines the rotorcraft’s takeoff performance is the amount of excess power available. Excess power available is the difference between the power required to hover at the reference height above the ground and the takeoff power available from a minimum installed specification engine. Utilizing the total power available to execute a takeoff may not be operationally feasible due to such items as HV constraints. In such situations, hover power required plus some power increment may be the maximum that can be used and the resulting performance determined accordingly.
(3) Landing gear height above the ground should not be greater than that demonstrated satisfactorily for HV, rejected takeoff, and that height for which IGE hover performance data is presented in the RFM, or less than that height below which ground contact may occur when accomplishing takeoff procedures. For rotorcraft fitted with wheels, a running takeoff procedure may be accepted. The hover reference height is established as the minimum landing gear height above the takeoff surface, from which a takeoff can be accomplished consistently in zero wind without contacting the runway.
Category B takeoff must be accomplished with power fixed at the power required to hover at the reference height (not greater than the height for which IGE performance data is presented).
c. Procedure. There are different techniques which may be used in order to determine which method is best for a particular rotorcraft. The most commonly accepted method is the hover and level acceleration technique. In this technique, the Page B – 29