АС 27-1A 7/30/97 40 30 AMBIENT TEMPERATURE - DEG F 20 - 10 -
• - -10 2000 4000 6000 8000 10,000
PRESSURE ALTITUDE - FT FIGURE 693-2. INTERMITTENT ICING - TEMPERATURE VS ALTITUDE LIMITS Figures 693-1 through 4 represent the approach to a 10,000-foot altitude limit.
See Paragraph b(5)(iii) for a discussion on this approach.
920 Par 693
1.0 - LIQUID WATER CONTENT - GRAMS/CUBIC METER 0.8 SEA LEVEL TO 10,000 FT PRESSURE ALTITUDE
0.6 AMBIENT TEMP °F
0.4
0.2 10 20 30 40 50
MEAN EFFECTIVE DROP DIAMETER - MICRONS FIGURE 693-3. CONTINUOUS ICING-LIQUID WATER CONTENT VS. DROP DIAMETER Figures 693-1 through 4 represent one approach to a 10,000-foot altitude limit.
See Paragraph b(5) (iii) for a discussion of this approach.
921 Par 693
2.0 SEA LEVEL TO 10,000 FT PRESSURE ALTITUDE LIQUID WATER CONTENT - GRAMS/CUBIC METER 1.6 AMBIENT TEMP
- 32 °F
1.2
- 14 °F
0.8
- 0 °F
0.4 10 20 30 40 50
MEAN EFFECTIVE DROP DIAMETER - MICRONS FIGURE 693-4. INTERMITTENT ICING-LIQUID WATER CONTENT VS DROP DIAMETER Figures 693-1 through 4 represent one approach to a 10,000-foot altitude limit.
See paragraph b(5)(iii) for a discussion of this approach.
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694.-700. RESERVED.
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701. RESERVED.
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SECTION 39. MISCELLANEOUS EQUIPMENT
702. RESERVED.
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703. RESERVED.
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704. § 27.1435 HYDRAULIC SYSTEMS.
a. References. The following sections of Part 27 are either incorporated in the provisions of § 27.1435 or are otherwise applicable to hydraulic system design:
§§ 27.695, 27.861, 27.863, 27.1183, 27.1185, 27.1189, 27.1309, and 27.1322.
b. System Design. It is assumed that the hydraulic system will be utilized to operate utility systems and the primary control system of the rotorcraft.
(1) Section 27.1309(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, and so forth. Also, consideration of the specific requirements of § 27.1435 should be included.
(3) If the rotorcraft cannot be safely operated without the hydraulic system, the requirements of § 27.1309(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 systems. 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.
(4) Dual actuators must be designed to ensure 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.
(5) If installed, the pressure-indicating system is normally included as a dial, vertical scale, or digital indicator. The indicator should enable the crew to detect pressure trends. Paragraph 633 of this AC concerns § 29.1322 regarding proper colors for annunciators if used to supplement the indicating system.
(6) A combination of analysis and tests should be included in the substantiating data file to show compliance with the provisions of § 27.1435.
(7) Extra caution should be exercised to ensure that control input forces at the mechanical connection to the actuator pilot valves do not exceed their intended value.
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Consideration should be given to the most adverse tolerance buildup in parts fabrication and control system rigging.
(8) 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 621b(2)(i) of this AC contains a method of temperature correction to cover the entire operating temperature envelope being certified.
(9) 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 ensure expected line life.
(3) If flammable hydraulic fluid is used, the hydraulic components should be isolated from ignition sources to ensure 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 AC.)
(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 a vendor's or a primary manufacturer's laboratory test reports. These tests should establish performance ratings such as pressures, flow rates, environmental capability, etc., to be approved.
934 Par 704
(2) After the total system is installed, ground tests should be conducted to ensure the system performs as intended and that each component is functioning within its design rating. System testing should consider the provisions of § 27.1435(b).
(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. Temperature results should be corrected for hot day conditions.
(Paragraph 621b(2)(i) of this AC gives a recommended procedure.)
(5) All controls should be cycled throughout their complete range of travel while accomplishing the provisions of Paragraph 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 Paragraphs d(2) and (4) above to determine that component ratings are not exceeded.
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706. § 27.1457 (Amendment 27-22) COCKPIT VOICE RECORDER.
a. Explanation. The function of the cockpit voice recorder (CVR) is to provide a record of the crew communications preceding and during rotorcraft accidents. 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 mandates of Congress, the use of CVR's is required by the operating rules 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 should be approved. The most common way of obtaining an approval is to qualify the CVR (and associated control panel, if appropriate) to TSO C84 or C123.
(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) 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 flight operations to produce the maximum cockpit background noise. The operation should provide for the normal speech of all crew members to be recorded on the pertinent channels. Then, during playback, preferably using a different listener, the listener should be able to identify the different crew members, 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 the most reliable source which does not jeopardize essential or emergency loads. Since the functioning of the CVR is required by operating rules for some operations, it should be given priority over other nonessential loads.
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