(10) The substantiating data should show that the hydraulic components will perform their intended function reliably under the most adverse continuous and short-time environmental conditions to which they are exposed. These variables include but are not limited to temperature, humidity, vibration, altitude, and shock.
Paragraph AC 29.1309.b.(9)(ii)(A) is a method of temperature correction to cover the entire operating temperature envelope being certified.
(11) The system component strength must be sufficient for its material fatigue life to exceed the number of cycles imposed by pump ripple pressure.
c. Installation Precautions and Fire Protection.
(1) All components and tubing routed through fire zones may be designed to comply with the fire protection requirements of §§ 29.1183, 29.1185, and 29.1189. As an alternative, a fireproof shield may be used around the component to be protected.
The component should be sufficiently protected to assure fluid leakage will not occur and fuel the fire.
(2) All hydraulic lines should be sufficiently isolated from the engine bleed air lines, environmental control unit, oil cooler, or other heat source to assure expected line life.
(3) If flammable hydraulic fluid is used, the hydraulic components should be isolated from ignition sources to assure that failure of any of the hydraulic components will not result in a fire or explosion. In t he case of electrical ignition sources in the proximity of hydraulic components, the electrical equipment should be hermetically sealed or otherwise substantiated as not being an ignition source. (Reference paragraph AC 29.1309.b.(9)(i)(D).)
(4) The installation detail should be thoroughly reviewed for adequacy of line clamping and clearance from sharp edges. As much physical separation as possible should be provided between hydraulic lines and electrical cables.
(5) While the control system is being moved from stop to stop, observation should be made to determine that hose flexing and tube bending is minimized.
d. Testing.
(1) Individual components should be substantiated by either vendor’s or primary manufacturer’s laboratory test reports. These tests should establish performance ratings such as pressures, flow rates, environmental capability, etc., to be approved.
(2) After the total system is installed, ground tests should be conducted to assure the system performs as intended and that each component is functioning within its design rating.
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AC 29-2C, Chg 4 5/1/2014
(3) If the total system design permits each combined independent power source and actuator to be disabled by shutoff valves, engine shutdown, etc., each combination should be disabled and the remaining combination verified to perform the necessary control functions. The test should be accomplished again with the functioning combination disabled and the disabled combination functioning. These tests should be accomplished first by ground tests, then repeated in flight.
(4) Temperature and pressure instrumentation should be provided at the critical points in the system to meet the provisions of d(2) above. Temperature results should be corrected for hot day conditions. (Paragraph AC 29.1309.b.(9)(ii)(A) gives a recommended procedure.)
(5) All controls should be cycled throughout their complete range of travel while accomplishing d(2) above.
(6) Satisfactory hydraulic system performance should be verified while the pump drive sources (rotor, engine, etc.) are individually varied throughout their approved operating range.
(7) Flight tests should be conducted throughout all altitudes, maneuvers, and control ranges while the system is instrumented as in d(2) and (4) above to determine that component ratings are not exceeded.
AC 29.1439. § 29.1439 PROTECTI VE BREATHING EQUIPMENT.
a. Explanation. This paragraph prescr ibes minimum requirements for eye and respiratory protection from toxic atmospheres during in-flight emergencies if one or more cargo or baggage compartments are to be accessible in flight. The equipment provided shall assure the crew protection against an oxygen deficient, toxic or highly irritating environment such as smoke.
b. Procedures.
(1) The equipment should provide a good fit for the range of intended users.
(2) A donning procedure should be provided by the manufacturer, evaluated, and the final procedure included in the Rotorcraft Flight Manual.
(3) The equipment should accommodate crewmembers who wear corrective glasses. Nominal position of eyeglasses should not be compromised. The equipment should not cause distortion or undue discomfort.
(4) The equipment donned under the stress of emergency should orient to the face and head, and interface to mating equipment, if required, in an obvious and Page F – 118
uncomplicated manner. Respiratory and eye protection should be provided in a manner that does not compromise the crew’s ability to perform required tasks.
(5) Any system that interfaces with existing components, should demonstrate satisfactory performance when operated with these components.
(6) For systems that require positive pressure to furnish satisfactory protection, a positive pressure vs. gas consumption curve should be supplied with the system along with instructions on the proper matching of the system or components to assure the minimum duration requirements of the standard are met.
(7) TSO-C99 and C116 are for Protective Breathing Equipment. If equipment is considered that is not qualified to one of these TSO’s, it is recommended that their provisions be reviewed and used as a basis for a qualification program for the equipment being considered. TSO -C99 provides minimum performance requirements for emergency equipment which provides flight deck and cabin crewmembers with eye and respiratory protection from toxic atmospheres during in-flight emergencies.
TSO-C116 results in protective breathing equipment that provides any crewmember with the ability to locate and combat a fire within the aircraft cabin or any other accessible compartment.
(8) Additional information regarding oxygen supply systems can be found in paragraph AC 29 MG 6.
AC 29.1457. § 29.1457 (Amendment 29-6) COCKPIT VOIC E RECORDER.
a. Explanation. The function of the cockpit voice recorder (CVR) is to provide a rec ord of the crew communications preceding an accidental crash of the rotorcraft.
Over the last several years, the National Transportation Safety Board (NTSB) has determined that CVR’s are invaluable in determining probable cause of an accident.
Because of this fact and acts of Congress, the use of CVR’s is required on many rotorcraft involved in passenger-carrying operations.
b. Procedures. The following a reas are of particular consideration in the approval of a CVR installation.
(1) Equipment Qualifications. The CVR must be approved. The most common way of obtaining an approval is to qualify the CVR (and associated control panel, if appropriate) to TSO C84.
(2) Cockpit Area Microphone (CAM). The third channel of recorded information is specified to be from a cockpit area microphone or from voice activated lip microphones at the first and second pilot stations. It should be noted that a continuously recording or “hot” microphone at both the first and second pilot stations would satisfy this CAM requirement. Due to the ambient noise level in rotorcraft, the use of “hot” microphone results in objectionable constant “hissing” in the pilot’s Page F – 119
headsets. Therefore, it is recommended that “hot” microphones not be used on rotorcraft.
(3) CVR Mechanical Installation. The CVR or the portion thereof which contains the recording should be physically located to enhance the probability of the recording surviving a crash. Normally, such a location would be in the lower portion of the rotorcraft as far aft as possible.
(4) Intelligibility of Recordings. Tests should be accomplished to determine that the recording is intelligible enough to make a positive identification of the speaker and the words or phrases spoken. This is usually accomplished by a flight test that provides an operation to produce the maximum cockpit background noise. The operation should provide for the normal speech of all crewmembers to be recorded on the pertinent channels. Then, during playback, preferably using a different listener, the listener should be able to identify the different crewmembers, the words and phrases spoken by the crew, and the radio communications made by and to the crew. The use of special filters and multiple playbacks to improve intelligibility is acceptable.
(5) Electrical Power Supply. The rule requires that the CVR should be supplied with power from a reliable source that does not jeopardize essential or emergency loads. For Category A rotorcraft, the CVR is not an essential load as specified in § 29.1309(e). However, since the functioning of the CVR is required by operating rules for some operations, it should be given priority over other nonessential loads.
(6) Self-Test Function. The CVR should be provided with a means in the cockpit that will allow a test to ensure the CVR is functioning properly. This may be accomplished by a manual playback feature.
(7) Bulk erasure. If this function is provided, the installation should be as follows:
(i) Any probable malfunction will not cause erasure of the recording medium.
(ii) The crash impact forces will not cause activation of the bulk erasure function.
(iii) Inadvertent actuation of the bulk erasure function is minimized.
Usually, this is accomplished by requiring two separate actions to operate the bulk erasure.
AC 29.1459. § 29.1459 (Amendment 29-25) FLIGHT RECORDERS .
a. Explanation. The function of the flight recorder, sometimes referred to as a flight data recorder, is to provide a record of various aircraft and air data parameters during the operation of the rotorcraft. This data is utilized by accident investigators to Page F – 120
aid in determination of the probable cause of an accident. The problems associated with acquisition of this data in aircraft not equipped with flight recorders has been complicated by the use of advanced instrument systems such as EFIS, EICAS, and IDS. The very nature of the operation of these systems precludes the deduction of post-accident data, as was possible with mechanical and electromechanical instruments, annunciators and switches. The National Transportation Safety Board (NTSB) therefore made a recommendation to the FAA that aircraft should be required to have flight recorders. Subsequently Congress mandated that flight recorders be required on many rotorcraft involved in passenger-carrying operations in accordance with FAR 91 and FAR 135.
b. Procedures. The following areas are of particular consideration in the approval of a flight data recorder installation.
(1) Equipment Qualification. The recommended procedure to obtain an approval for the flight recorder (and associated control panel, if appropriate) is to qualify the flight recorder to TSO C-124. The required underwater locating device should be qualified to the provisions of TSO C-121.
(2) Recorded Parameters and Accuracy.
(i) Airspeed. The installed flight recorder for a Category A rotorcraft should record the airspeed with an accuracy of 3 percent or 5 knots (whichever is greater) from a speed of 80 percent of VTOSS to VNE in level flight, and an accuracy of 10 knots from a speed 10 knots less than VTOSS to a speed of 10 knots more than VY in climb.
(ii) Pressure Altitude. The flight recorder should be capable of recording the pressure altitude of the rotorcraft with a range of -1,000 feet to the maximum certified altitude. The error of this recording at sea level, excluding instrument calibration error, should not exceed ±30 feet or a value of ±30 feet for each 100 knots of airspeed (whichever is greater).
(iii) Direction. The flight recorder should be capable of recording the magnetic heading of the rotorcraft within at least 10 degrees for any heading.
(iv) Vertical Acceleration. The flight recorder should be capable of recording the normal acceleration within the center of gravity range of the rotorcraft.
The recommended range of this recording is an envelope of -3 to +6 G with an accuracy of at least ±0.2 G.
(v) Time Correlation. The flight recorder should provide a time scaled correlation between the data recorded and the time at which this information was presented to the first pilot via his required flight instruments. This correlation should normally be established before flight, and should have an accuracy rate that does not diverge by more than 4 minutes and 4 seconds in 8 hours.
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(vi) Caveat. It should be noted that even though the requirements outlined above provide for compliance with the specific provisions of § 29.1459 regarding the acquired data and its accuracy, a flight recorder certified to these minimum standards will not meet the requirements of Appendix F of FAR 91 or Appendix C of FAR 135. If the flight recorder is to be used to comply with these operating rules, it is recommended that the appropriate appendix be consulted prior to requesting certification. The approved configuration may then be certified as meeting the requirements of the appropriate appendix.
(3) Flight Recorder Mechanical Installation. The non- ejectable flight recorder or the portion thereof which contains the recorded data should be physically located to enhance the probability of the recording surviving a crash. Normally, such a location would be in the lower portion of the rotorcraft as far aft as possible. However other locations in the rotorcraft may be suitable to meet the requirement to “minimize the probability of container rupture resulting from crash impact and subsequent damage to the record from fire.” The normal accelerometer should be located within the most restrictive center of gravity of the rotorcraft. The required underwater locator is usually mounted to the case of the flight recorder.
(4) Electrical Power Supply. The rule requires that the flight recorder should be supplied with power from a reliable source that does not jeopardize essential or emergency loads. For Category A rotorcraft, the flight recorder is not an essential load as specified in § 29.1309(e). However, since the functioning of the flight recorder is required by operating rules for some operations, it should be given priority over other nonessential loads.
(5) Self-Test Function. The flight recorder should be provided with a preflight test which will provide confirmation that the recorder and its recording medium are functioning properly.
(6) Data Erasure Feature. If this function is provided and the flight recorder is not powered solely by an engine or transmission driven generator, the installation should provide the following features:
(i) Any probable malfunction will not cause erasure of the recording medium.
(ii) The crash impact forces will not cause activation of the data erasure function.
(iii) Inadvertent actuation of the data erasure function is minimized.
Usually, this is accomplished by requiring two separate actions to operate the data erasure.
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AC 29.1461. § 29.1461 (Amendment 29-3) EQUIPMENT CONTAINING HIGH ENERGY ROTORS.
a. Explanation. This section contains requirements for the installation of equipment containing high energy rotors. A high energy rotor is any rotor which has sufficient kinetic energy to cause damage to surrounding structure, wiring, and equipment if a failure occurs. Turboshaft engine and APU rotors are not covered by this paragraph. One of the following requirements of § 29.1461 must be met.
(1) Paragraph (b) deals with damage tolerance, containment, and control devices.
(2) Paragraph (c) deals with containment and inoperative speed controls.
(3) Paragraph (d) deals primarily with equipment location.
b. Procedures.
(1) Compliance with § 29.1461(b) can be shown by a combination of analysis and test. A failure modes and effects and a stress analysis, together with a dynamic test, could be used to verify that the rotor would withstand the damage from environmental effects, and that the rotor case would contain any parts that may separate from the rotor shaft. The analysis and test should include a demonstration of the control device’s ability to prevent limitations from being exceeded.
(2) If compliance with the requirements of § 29.1461(c) is chosen, a test must be conducted which demonstrates that all parts from any type failure of a high energy rotor will be contained when that rotor is operating at the highest speed obtainable, with all speed control devices inoperative. This containment must not damage any components, systems, or surrounding structures that are essential for continued safe flight.
(3) If compliance with § 29.1461(d) is chosen, the location of the high energy rotor must be in an area where uncontained failed parts will not damage other components, systems, or surrounding structure which are essential for continued safe flight. It must also be shown that there is no possibility for failed, uncontained parts to enter the cabin area and endanger any occupant.
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CHAPTER 2. PART 29
AIRWORTHINESS STANDARDS
TRANSPORT CATEGORY ROTORCRAFT
SUBPART G - OPERATING LIMITATIONS AND INFORMATION AC 29.1501. § 29.1501 (Amendment 29-15) OPERATING LIMITATIONS - GENERAL.
This section simply requires specified operating limitations in addition to any other information necessary for the safe operation of the rotorcraft to be determined.
Secondly, it requires that this pertinent information be made readily available to the crewmembers as required in the various sections of this subpart.
OPERATING LIMITATIONS AC 29.1503. § 29.1503 AIRSPEED LIMITATIONS: GENERAL.
a. Explanation. This section requi res that a safe operating speed range be established for all rotorcraft. If the safe operating speed range varies with operating conditions (rotor speed, power, etc.), ambient conditions (altitude and/or temperature), rotorcraft configuration (gross weight, center of gravity, and/or external equipment), or type of operation (in ground effect (IGE), instrument flight rules (IFR), etc.), airspeed limitations that correspond with the most critical combinations of these factors must be established.
b. Procedures.
(1) Airspeed Limitations. The airspeed lim itations for each critical combination of factors are established by tests or analyses and verified by flight test. The following are airspeed limitations that are typically required depending on the particular rotorcraft design:
(i) VNE (Power On). See paragraph AC 29.1505.
(ii) VNE (One Engine Inoperative (OEI)). See paragraph AC 29.1505.
(iii) VNE (Power Off). See paragraph AC 29.1505.
(iv) VLO (Maximum Airspeed for Landing Gear Operation). Compliance with structural, handling qualities, and controllability requirements should be demonstrated at the airspeed limit.
(v) VLE (Maximum Airspeed Landing Gear Extended). If this airspeed limit differs from the maximum gear operation speed, compliance with the applicable structural, handling qualities, and controllability requirements should be demonstrated.
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(vi) Low Speed Flight Limitation. It is permissible for the applicant to establish a minimum airspeed operating limitation as a function of weight, altitude, and temperature as long as there is still a practical flight envelope.
(vii) VMINI (Minimum IFR Speed). The minimum speed for which compliance with the IFR handling qualities requirements has been demonstrated should be established as a limit for IFR operations.
(viii) Maximum Sideward and Rearward Flight Speed. The maximum demonstrated sideward flight or crosswind hover and rearward flight or tailwind hover airspeeds should be provided in the RFM. If these maximum speeds resulted from a control margin limitation, they should be included in the airspeed limitations section of the RFM. If adequate control margin remained fo r the critical combination of rotorcraft configuration and ambient conditions, the maximum demonstrated sideward or rearward flight airspeeds should be included in either the performance section or the limitations section of the RFM as the applicant desires.
(ix) Maximum Airspeeds for Special Configurations or Special Equipment.
Standard configuration airspeed limits frequently have to be reduced for specific changes or external modifications. The follo wing are examples of special equipment or configurations that have required additional airspeed limitations:
(A) Doors open or doors off.
(B) External hoist/cargo hook (stowed).
(C) Fixed or emergency flotation gear.
(D) External avionics equipment (large antennas, wires, etc.)
(E) External fuel tanks.
(F) Skid pad or ski equipment modifications to standard skid type landing gear.
(x) Maximum Airspeeds after Failure of Required Equipment. Rotorcraft that require auxiliary equipment such as stability augmentation systems to comply with FAR requirements throughout the approved operating envelope frequently require airspeed limitations following failure of part or all of this system in order to comply after the failure. The following are examples of auxiliary equipment that have required maximum airspeed limitations after failure of all or part of the system:
(A) Stability Augm entation Systems (SAS).
(B) Automatic Flight Control Systems (AFCS).
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(C) Fly-by-Wire Elevator Systems (FBW).
(D) Air Data Computer Systems (ADC).
(2) Groundspeed Limitations. Although not specifically required by this “airspeed limitations” regulation, it may be necessary to establish “groundspeed” limitations for wheel-gear-equipped rotorcraft. These limitations are required to show compliance with the ground-handling characteristic requirements, structural strength requirements, or the ground-loads requirements. However because of the operational similarity of groundspeed limits to airspeed limits, it is a common practice to include groundspeed limitations under the airspeed limitations heading in the flight manual. For this reason, groundspeed limitations are included in this paragraph of the AC.
Groundspeed limitations should be established with adequate safety margins to account for the possible inaccuracies associated with the necessity for the pilot to estimate groundspeed from indicated airspeed and available wind speed and direction information during actual operations. The following are examples of groundspeed limitations that have been required during past type certification programs:
(i) Maximum Groundspeed for Takeoff or Landing. The maximum acceptable groundspeed that can safely be used for wheel gear equipped rotorcraft takeoff and landing maneuvers should be determined based on landing gear limitations or ground controllability limitations. This speed should be fast enough to account for landing touchdown speeds at the maximum approved density altitude for normal takeoff and landing.
(ii) . The maximum speed at which the wheel b Maximum Groundspeed for Brake Application rakes may be applied without exceeding maximum brake energy capabilities should be determined for wheel gear equipped rotorcraft. This speed should be verified by test throughout the approved takeoff and landing envelope of the rotorcraft. The critical combination of gross weight and density altitude for brake energy considerations may be determined by analysis to minimize the required amount of testing. The maximum brake application groundspeed should be high enough to encompass brake application during landing at the maximum approved density altitude.
(iii) Other Groundspeed Limitations. For some rotorcraft designs with skid type landing gear, it may be necessary to establish a maximum landing touchdown speed for normal operations to comply with structural requirements. Optional equipment configurations such as float equipment, skis, etc., which are attached to conventional landing gear skids may require maximum landing groundspeed limits that are less than the limit for the basic rotorcraft.
AC 29.1505. § 29.1505 (Amendment 29-24) NEVER-EXCEED SPEED.
a. Explanation.
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AC 29-2C, Chg 1 2/12/03
(1) General. This rule requires the never -exceed speed (VNE) for both power-on and power-off flight to be established as operating limitations. The rule specifies how to establish and substantiate these limits.
(2) Power-on Limits.
(i) All Engines Operative (AEO).
(A) The all-engines-operating VNE is established by design and substantiated by flight tests. The V NE limits are the most conservative value that demonstrates compliance with the structural requirements (§ 29.309), the maneuverability and controllability requirements (§ 29.143), the stability requirements (§§ 29.173 and 29.175), or the vibration requirements (§ 29.251). The power -on VNE will normally decrease as density altitude or weight increases. A variation in rotor speed may also require a variation in the VNE. The regulation restricts to two the number of variables that are used to determine the VNE at any given time so that a single pilot can readily ascertain the correct VNE for his flight condition with a minimum of mental effort.
Helicopter manufacturers have typically presented never-exceed-speed limitation data as a function of pressure altitude and temperature. This information was placarded as well as contained in the flight manual. As the weight of some derivative models was increased, the FAA/AUTHORITY accepted altitude/temperature/VNE limitations that were categorized or contained within a weight range. Literal compliance with the regulation then required that the takeoff weight be calculated and then the indicated, appropriate airspeed limitation chart or placard be used for the entire flight. However, VNE charts or placards based on longitudinal center-of-gravity (c.g.) have been found to be unacceptable, since the same chart would potentially not be used throughout the flight and the pilot would thus be dealing with more than two variables to determine VNE.
Alternatively, rotorcraft that are equipped with air data computers or other similar equipment are allowed to vary as many parameters as desired, if the final results are no more than two parameters that define the VNE displayed to the pilot in an unambiguous manner. These rotorcraft must also have a method for determining V NE that complies with the regulation in the event the air data computer system fails. This method is usually more conservative than the automatic system because of the limitation in the number of parameters that can be varied.
(B) To ensure compliance with the structural requirements (§ 29.309), vibration requirements (§ 29.251), and flutter requirements (§ 29.629), the all-enginesoperating VNE should be restricted so that the maximum demonstrated main rotor tip mach number will not be exceeded at 1.11 VNE for any approved combination of altitude and ambient temperature. Previous rotorcraft cold weather tests have shown that the rotor system may exhibit several undesirable and possibly hazardous characteristics due to compressibility effects at high advancing blade tip mach numbers. As the center of pressure of the advancing rotor blade moves aft near the blade tip due to the formation of localized upper surface shock waves, rotor system loads may increase, the rotor system may exhibit an aerodynamic instability such as rotor weave, rotorcraft Page G - 4
vibration may increase substantially, and rotorcraft static or dynamic stability may be adversely affected. Which, if any, of these adverse characteristics are exhibited at high rotor tip mach numbers is dependent on the design of each particular rotor system.
FAA/AUTHORITY experience has shown some adverse characteristics exist for all the types of rotor systems (articulated, semirigid, rigid, etc.) and the various rotor blade designs evaluated at high advancing blade tip mach numbers during past certification programs. Therefore, it has been FAA/AUTHORITY policy to establish V NE so that it is not more than 0.9 times the maximum speed substantiated for advancing blade tip mach number effects for the critical combination of altitude, approved power-on rotor speed, and ambient temperature conditions. This policy was incorporated as a specific regulatory requirement with Amendment 29-24 to § 29.1505. High main rotor tip mach numbers obtained power off at higher than normal main rotor rotational speeds should not be used to establish the maximum power-on tip mach number VNE limit. In addition, since the onset of adverse conditions associated with high tip mach numbers can occur with little or no warning and amplify very rapidly, no extrapolation of the maximum demonstrated main rotor tip mach number VNE limitation should be allowed.
(C) A maximum speed for use of power in excess of maximum continuous power (MCP) should be established unless structural requirements have been substantiated for the use of takeoff power (TOP) at the maximum approved VNE airspeed. TOP is intended for use during takeoff and climb for not more than 5 minutes at relatively low airspeeds. However, FAA/AUTHORITY experience has shown that pilots will not hesitate to use TOP at much higher than best-rate-of-climb airspeeds unless a specific limitation against TOP use above a specified airspeed is included in the RFM. Structural and fatigue substantiations have not normally included loads associated with the use of TOP at VNE. Thus, a TOP airspeed limitation should be established from the structural substantiation data to preclude the accumulation of damaging rotor system and control mechanism loads through intentional use of the TOP rating at high airspeeds.
(ii) One Engine Inoperative (OEI). An OEI V NE is generally established through flight test and is usually near the OEI VH of the rotorcraft. It is the highest speed at which the failure of the remaining engine must be demonstrated. For rotorcraft with more than two engines, the appropriate designation would be “one-engine-operating” VNE and would be that speed at which the last remaining engine could be failed with satisfactory handling qualities. It is possible that a rotorcraft with more than two engines could have different VNE’s depending upon the number of engines still operating. It is recommended that the OEI V NE not be significantly lower than the OEI best range airspeed. For the last remaining engine failure case, a multiengine rotorcraft may require an OEI VNE if the handling qualities are not satisfactory, if the rotor speed decays below the power-off transient limits, or if any other unacceptable characteristic is found at speeds below the all-engine-operating VNE.
(3) Power-off Limits.
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