b. Procedure. The following items should be specifically addressed when evaluating a vacuum system installation:
(1) Pressure and Temperature Protection. The high pressure outlet of the vacuum pump should have a means to automatically relieve the pressure if it becomes excessively high or the air temperature becomes excessively hot.
(2) Fire Hazard Protection. The components of the vacuum system which are mounted in a designated fire zone should be fire resistant. This includes engine or transmission driven pumps if they are in a fire zone. The discharge side of the pump may emit flammable fluids. This discharge side of the pump, along with its associated lines and fittings, should meet the criteria in Paragraph 585 of this AC.
704. § 29.1435 HYDRAULIC SYSTEMS.
a. Reference Regulations. The following sections of Part 29 are either incorporated in the provisions of § 29.1435 or are otherwise applicable to hydraulic system design:
(1) Section 29.695. Paragraph 287 of this advisory circular covers power boost and power operated control systems.
(2) Section 29.861. Paragraph 361 of this advisory circular covers fire protection of structure, controls, and other parts.
(3) Section 29.863. Paragraph 362 of this advisory circular covers flammable fluid fire protection.
(4) Section 29.1183. Paragraph 585 of this advisory circular covers lines, fittings, and components.
(5) Section 29.1185. Paragraph 586 of this advisory circular covers flammable fluids.
(6) Section 29.1189. Paragraph 588 of this advisory circular covers shutoff means.
(7) Section 29.1309. Paragraph 621 of this advisory circular covers the requirements for functioning and reliability, and prevention of hazards if malfunctions or failures occur.
(8) Section 29.1322. Paragraph 633 of this advisory circular covers warning, caution, and advisory lights.
Par 703 1077
b. System Design. It is assumed that the hydraulic system is to be utilized to operate the primary control system of the rotorcraft and the rotorcraft cannot be safely operated without the hydraulic system.
(1) Section 29.1309, Paragraphs (a) and (b), provides for functioning reliably under any foreseeable operating condition and prevention of hazards after any malfunction or failure.
(2) The substantiating data should include a failure analysis that considers every possible system component failure, such as (but not limited to) ruptured lines, pump failure, regulator failure, ruptured seals, clogged filters, broken pilot valve connections, etc.
(3) The requirements of § 29.1309(a) and (b) are met by dual independent hydraulic systems from the reservoir, hydraulic pump, regulator, connecting tubing, and hoses through the actuators. There must be no commonality in the fluid-containing components. A break in one system should not result in fluid loss in the remaining system.
(4) The pumps should be separated as far as practicable; i.e., on opposite sides of the rotor drive transmission, on separate engines, or one pump on an engine and the other on the rotor drive transmission. The tubing and hoses should also be routed with as much physical separation as practicable. The purpose of this separation is to prevent total loss of the hydraulic systems in the event of a malfunction such as fire, or rotor burst wherein one projectile could disable both systems.
(5) Dual actuators must be designed to assure that any single failure, such as a cracked housing, broken interconnecting input, or output link, does not result in loss of total hydraulic system function.
(6) If the assumption under (b) above does not apply and the pilot can control the rotorcraft without undue fatigue after loss of the hydraulic system, then a single hydraulic system is acceptable.
(7) The pressure-indicating system required by § 29.1435, Paragraph (a)(3), can be satisfied with a dial, vertical scale, or digital indicator. The indicator should enable the crew to detect pressure trends. Paragraph 633 of this advisory circular concerns § 29.1322 regarding proper colors for annunciators if they are used to supplement the indicating system.
(8) An analysis or a combination of analysis and tests must be included in the substantiating data file to show compliance with Paragraphs (a)(1), (a)(2), and (a)(4) of § 29.1435.
1078 Par 704
(9) Extra caution should be exercised to assure that control input forces at the mechanical connection to the actuator pilot valves do not exceed their intended value.
Consideration should be given to the most adverse tolerance buildup in parts fabrication and control system rigging.
(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 621, b(2)(i), of this advisory circular 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 the 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 621b(1)(i) of this advisory circular.)
(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 Par 704 1079
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.
(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 621b(2)(i) of this advisory circular 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.
705. § 29.1439 PROTECTIVE BREATHING EQUIPMENT.
a. Explanation. This paragraph prescribes 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.
1080 Par 704
(3) The equipment should accommodate crewmembers who wear corrective glasses. Nominal position of eyeglasses should not be compromised. The equipment should not cause distortion nor 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 uncomplicated manner. Respiratory and eye protection should be provided in a manner which does not compromise the crew's ability to perform required tasks.
(5) Any system which interfaces with existing components, should demonstrate satisfactory performance when operated with these components.
(6) For systems which 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 786 of this document.
706. § 29.1457 (Amendment 29-6) COCKPIT VOICE RECORDER.
a. Explanation. The function of the cockpit voice recorder (CVR) is to provide a record 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 areas 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.
Par 705 1081
(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 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) Inteligibility 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 which 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 which 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 which 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.
(ії) The crash impact forces will not cause activation of the bulk erasure function.
1082 Par 706
(¡i) Inadvertent actuation of the bulk erasure function is minimized.
Usually, this is accomplished by requiring two separate actions to operate the bulk erasure.
707. § 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 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.
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 Vross to VNE in level flight, and an accuracy of 10 knots from a speed 10 knots less than Vross to a speed of 10 knots more than Vy in climb.
(i¡) 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).
(ill) Direction. The flight recorder should be capable of recording the magnetic heading of the rotorcraft within at least 10 degrees for any heading.
Par 706 1083
(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 10.2 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.
(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) Elight 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 which 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.
1084 Par 707
(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.
708. § 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.
Par 707 1085
(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.
1086 Par 708
709.-717. RESERVED.
Intentionally Left Blank Par 709 1087 (thru 1095)
AC 29-2B 7130/97 SECTION 40. OPERATING LIMITATIONS
718. § 29.1501 (Amendment 29-15) 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.
719. § 29.1503 AIRSPEED LIMITATIONS: GENERAL.
a. Explanation. This section requires 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 limitations 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 720.
(II) VNE (One Engine noperative (OEL)). See Paragraph 720.
(iii) VNE (Power Off). See Paragraph 720.
(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.
(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.
1096 Par 718