b. Procedures. All of the policy material pertaining to this section remains in effect. Additionally, selection of the location and orientation of the fuel drain discharge in the design phase is important to assure that there is no impingement upon any part of the rotorcraft. The location and orientation should also ensure effective fuel drainage when the rotorcraft is parked on uneven terrain. To show compliance with the requirement, tests may be required, dependent upon whether the applicant has a previously approved design that is similar, or the system is a new design for which no previous experience is available.
AC 29.1001. § 29.1001 (Amendment 29-26) FUEL JETTISONING.
a. Explanation. Amendment 29- 26 adds § 29.1001 to set forth the certification requirements for a fuel jettisoning system if it is installed in the rotorcraft.
b. Procedures. In showing compliance with the requirements of § 29.1001, the following guidance is provided.
(1) The fuel jettison system should be demonstrated to be safe in all normal flight regimes. Takeoff, hover, and in- ground-effect maneuvers may be excluded if appropriate limitations are prescribed.
(2) The fuel jettison system, and its operation, should be shown to be free from fire hazard. If possible, the fuel should discharge clear of any part of the rotorcraft;
however, it should be shown that any fumes or fuel, that do impinge upon the rotorcraft in the form of a fine mist, does not form droplets that run along the exterior structure and enter any part of the rotorcraft (wheel wells, cargo area, tail boom, etc.). It should also be shown that jettisoned fuel is not ingested by the engines or the auxiliary power unit (APU). This demonstration can be conducted by jettisoning a glycol based, dye colored fluid and noting the pattern displayed on a dye sensitive coating applied to the rotorcraft exterior. The demonstration should be conducted over all flight regimes in which system operation is permitted. The demonstration should also take into account the maximum rate of descent and all airspeeds where fuel impingement upon the fuselage would most likely occur. Rotorcraft controllability should remain satisfactory throughout the fuel jettisoning operation and should also be demonstrated.
(3) The requirements in § 29.1001(c) were established to prevent complete fuel depletion and provide the capability to effect continued safe flight and landing.
(4) The controls for the fuel jettison system should be designed so that a “minimum” flight crew can perform the jettison operation and be able at any time to stop the jettison process or begin it again. These design requirements give the flight crew the capability and flexibility to manage their on-board resources.
(5) The requirements of § 29.901(c) are intended to emphasize that no single failure or malfunction or probable combination of failures of the fuel jettisoning system will jeopardize the safe operation of the rotorcraft.
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(6) If the rotorcraft has an auxiliary fuel tank, an auxiliary fuel jettisoning system may be installed to jettison the additional fuel provided the jettisoning system has separate and independent controls and it also meets all of the requirements of this section.
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AC 29-2C, Chg 4 5/1/2014
SUBPART E - POWERPLANT OIL SYSTEM.
AC 29.1011. § 29.1011 ENGINES: GENERAL.
a. Explanation.
(1) The oil system provided for each installed engine should provide all of the lubrication required by the engine and supply it at a temperature which is within the operating temperature limits established for that engine when it was certified.
(2) The usable oil capacity of each oil system should be sufficient to provide oil to the engine at the maximum oil consumption limit of the engine under critical operating conditions. All circulating requirements and operating temperature limits for the oil should be met.
b. Procedures.
(1) There are three basic engine oil supply and cooling system concepts that are used. There are self-contained systems (a complete system certified with the engine), systems that have both engine and airframe components, and systems that are totally supported by airframe components. Any one of these three concepts can be used to meet the requirement of having an independent oil system for each engine.
(2) Oil tank capacity is primarily determined by the engine’s oil consumption rate. Other factors which should be considered when sizing the oil supply system are the endurance of the rotorcraft under critical operating conditions, and the amount of oil circulating in the system to maintain proper cooling. Adequacy of the engine oil supply system can be shown by analysis supported by engine oil consumption and cooling system data. For reciprocating engines, the ra tio of one gallon of oil for each 40 gallons of fuel can be used; however, an oil-fuel ratio lower than 1:40 can be used if properly substantiated by oil consumption data on the engine.
(3) The engine oil cooling requirements are defined in §§ 29.1041 through
29.1049. The design of the engine oil cooling system will be influenced by hot day conditions, by the engine heat rejection rate, and other oil system operating data provided by the engine manufacturer. Si zing of the oil cooler will depend upon the engine data and whether the oil cooler will also be used for main transmission oil cooling. Oil cooler size should be kept as small as possible due to its effect on rotorcraft structure, but in all cases, adequate cooling should be demonstrated throughout the operating envelope of the rotorcraft.
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AC 29.1013. § 29.1013 (Amendment 29-10) OIL TANKS .
a. Explanation. This regulation identifies the requirements that each oil tank must meet. It also specifies that the oil tank installation must meet the installation requirements of § 29.967.
b. Procedures.
(1) The oil tanks usually are constructed of aluminum, aluminum alloy, or stainless steel and are of such a design to permit installation in the aircraft as close to the engine as the design allows. The choice of materials will generally be determined by the selected location of the tank. The tank envelope or outline will generally be determined by the location within the structure of the rotorcraft.
(2) The design of the tank is required to meet the expansion space requirements as specified in the regulation for the particular installation. This is generally accomplished by locating the filler cap in such a manner that the expansion space cannot be inadvertently filled with the rotorcraft in normal ground attitude.
(3) The tank is required to be properly vented and the vent requirements are identified in the regulation.
(4) Unless alternate means are provided, it is good design practice to locate the oil tank with respect to the engine so that when the rotorcraft is in its normal ground attitude, a positive head to the oil pump inlet is provided.
(5) Sections of the regulation address specific requirements when Category A certification is requested.
(6) The designer should be aware of the requirements associated with the location of the oil tank outlet and the marking requirements specified in § 29.1557(c)(2).
(7) Flexible oil tank liners may be used; however, they must be approved or shown to be suitable for the particular installation.
(8) An “external oil system” which is defined as being those components, lines, etc., of an oil system which are outside the engine and not supplied as part of a certificated engine. The components of such a system which are within the fire zone and required to be fire resistant. Those outside the fire zone need not be fire resistant.
AC 29.1015. § 29.1015 (Amendment 29-10) OIL TANK TESTS.
a. Explanation. This regulation defines the tests that must be accomplished to show compliance for rotorcraft oil tanks.
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(1) The oil tank should be designed and installed so that it can withstand, without failure, any vibration, inertia, and fluid loads to which it may be subjected in operation.
(2) The installation should meet the requirements of § 29.965 except that for pressurized tanks used with turbine engines, the test pressure may not be less than 5 PSI plus the maximum operating pressure of the tank. For all other tanks, the test pressure may not be less than 5 PSI.
b. Procedures. The pressure tests require that 5 PSI plus operating pressure but in any case no less than 5 PSI be used to substantiate the oil tank. To accomplish these tests, the various tank openings are sealed. An adapter fitting is fabricated by which regulated, pressurized air is introduced into the tank. This air pressure is measured by means of a calibrated air pressure gauge. Any of several methods to determine whether the tank is leaking may be used. As an example, if the tank is relatively small, emergence in a tank of water may be used. Other means such as applying soapy water to the joints are also satisfactory. In any respect, the leak check using test fluid conforming to Federal Specification TT-S-735, Type III, may also be used.
AC 29.1017. § 29.1017 OIL LINES AND FITTINGS.
a. Explanation. This regulation outlines the certification requirements for oil lines and fittings.
b. Procedures. The oil system lines and fittings are required to meet the requirements of § 29.993; therefore, the routing and clamping described in paragraph 709, Chapter 14, Section 2, of AC 43.13-1A may be utilized as guidance for the system design. An evaluation carried out through the development and certification test period will usually surface any problems of interference and/or vibration.
(1) When flexible hoses are used in the lubrication system they must be substantiated. Hoses listed in TSO C53a may be used which would preclude certain substantiation requirements.
(2) Location of the breather lines and discharge should be carefully evaluated to determine that the requirements of this paragraph are followed.
(3) The routing of fluid lines should be such that drooping lines and fluid traps which are undrainable are avoided.
AC 29.1019. § 29.1019 (Amendment 29-10) OIL STRAINER OR FILTER.
a. Explanation. This regulation defines the requirements for the engine oil system strainer or filter. If a strainer or filter which meets the requirements of this paragraph is Page E - 132
incorporated as part of the type certificated engine, an additional airframe filter is not required.
b. Procedures. This paragraph requires an oil strainer or filter through which all of the oil flows for each turbine engine installation. The strainer or filter should be sized to allow oil flow at the flow rates and within the pressure limits as specified in the engine requirements. The effect of oil at the minimum temperature for which certification is sought should be accounted for.
(1) For each oil strainer or filter required by § 29.1019(a) which has a bypass, the bypass should be sized to allow oil flow at the normal rate through the oil system with the filtration means completely blocked.
(2) For each oil strainer or filter installed per this rule, the capacity must be such that the oil flow and pressure are within the operating limits established for the engine. The mesh requirements are determined by the engine specification for the filtration of particle size and density.
(3) Section 29.1019(a)(3) requires an indicator that will show when the contaminant level of the filtration system, as specified in § 29.1019(a)(2), has been reached. The indicator should signal a contaminant level which has not caused the filter to go into a bypass condition. Consideration should also be given so that the contaminant level at which the indicator is activated is such that the filter would not bypass during a flight time based on full fuel at a cruise condition with the lubricant contaminated to the degree used to show compliance with § 29.1019(a)(2).
(4) An evaluation of the construction and location of the bypass associated with the strainer or filter should be accomplished. The appropriate installation of the filter based on this evaluation would preclude the release of the collected contaminants in the bypass oil flow.
(5) If an oil strainer or filter installed in compliance with this regulation does not have a bypass, there must be a means to connect it to the warning system required in § 29.1305(a)(18). This warning should indicate to the pilot the contamination before it reaches the capacity established in § 29.1019(a)(2). Section 29.1019(b) covers the blocked oil filter requirements associated with reciprocating engine installations. The lubrication system should be such that the normal oil flow will occur with the filter completely blocked.
AC 29.1019A. § 29.1019 (Amendment 29-26) OIL STRAINER OR FILTER.
a. Explanation. Amendment 29- 26 relaxes the requirements of § 29.1019(a)(3) from requiring an indicator to indicate the contamination level of oil filters. The rule change allows acceptance of a “means to indicate” the contaminate level to allow a wider range of acceptable methods of compliance.
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b. Procedures. Unless the filter is located at the oil tank outlet, § 29.1019(a)(3) requires that the oil strainer or filter have the means to indicate when the contaminant level of the filtration system, as specified in § 29.1019(a)(2), has been reached. If the indicator is installed, it should signal a contaminant level that will allow completion of the flight before the filter reaches a bypass condition. The indicator may be a pop-out button or other maintenance cue that is checked on each preflight inspection.
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AC 29.1019B. § 29.1019 (AMENDMENT 29-59) OIL STRAINER OR FILTER.
a. Explanation. Amendment 29-59 revised § 29.1019(a)(5) to correct a reference from § 29.1305(a)(18) to § 29.1305(a)(19). When § 29.1305 was updated at Amendment 29-40, the numbering sequence was changed. The oil filter contamination warning, § 29.1305(a)(18), was referenced in § 29.1019(a)(5) but was not updated at Amendment 29-40 to account for the change in numbering sequence.
b. . The policy pertaining to the procedures in this section remains unchanged, Procedures however the reference to the § 29.1305 oil filter contamination indicator has been corrected.
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AC 29.1021. § 29.1021 OIL SYSTEM DRAINS.
a. Explanation Procedures Explanation Procedures.
a. Explanation Procedures . This regulation requires provisions be provided for safe drainage of the entire oil systems and defines certain requirements for assuring that no inadvertent oil flow occurs from the system provided.
b. . The design of the oil system must provide a means for safe drainage of the entire oil system. This may require one or more drains dependent upon the design of the system. If a valve is used for this function, it must provide a means for a positive lock in the closed position. The method by which the lock is accomplished may be manual or automatic.
AC 29.1023. § 29.1023 OIL RADIATORS.
a. . This regulation defines the installation requirements to be considered for oil system radiators.
b.
(1) The primary concern with respect to oil radiators is that they are sized to provide the required heat rejection and to provide adequate fluid flow within the prescribed pressure limits.
(2) The structural design of the radiator must consider the system oil pressure requirements and the service involvement of the intended application. The selection of the location of the radiator can have a significant bearing on its ability to withstand the vibration and inertia loads.
(3) If the system design incorporates an air duct to direct the airflow, the effects of a fire as defined in this regulation must be considered.
AC 29.1025. § 29.1025 OI L VALVES.
. Thi s regulation identifies the requirements which oil system valves must meet. In addition to the items specified in this rule, this regulation specifies compliance with the requirements of § 29.1189.
b. . T he closing of the oil shutoffs may not preclude a safe autorotation. Compliance with this requirement is best accomplished in the design Page E - 134.2
phase. This can be accommodated by proper orientation of the valve and/or system plumbing routing. Another means is to design adequate entrapment of lubricants to provide for the autorotation state. The design of the oil shutoff valve must consider the stop or index provisions of this rule. The installation must be such that the loads specified in the rule are addressed.
AC 29.1027. § 29.1027 (Amendment 29-26) TRANSMISSION AND GEARBOXES:
GENERAL.
a. Explanation. Amendment 29- 26 adds a new § 29.1027. This new section provides the regulations for rotorcraft transmission and gearbox lubrication systems. It incorporates lubrication system requirements that were removed from § 29.1011 and adds additional lubrication system requirements that were derived from existing engine-oil system requirements. These additional requirements have been adjusted or modified to reflect the needs of transmissions and gearboxes. Transmission and gearbox lubrication system regulations are similar to those for engines; therefore, reference is made to the engine lubrication sections as applicable.
b. Procedures.
(1) The pressure lubrication systems for rotorcraft transmissions and gearboxes should comply with the same requirements as the engine lubrication systems stipulated in § 29.1013 (except §§ 29.1013(b)(1), 29.1015, 29.1017, 29.1021, and 29.1337(d)).
These sections provide the requirements for oil tanks, tank tests, oil lines and fittings, and oil system drains.
(2) Each pressure lubrication system for rotorcraft transmissions and gearboxes should have an oil strainer or filter. The strainer or filter should:
(i) Remove any contaminants from the lubricant that may damage the transmission, gearbox, or other drive system component and any contaminants that may impede the lubricant flow to a hazardous degree.
(ii) Be equipped with a means to indicate that the bypass system (required by § 29.1027(b)) is at the point of opening, due to the collection of contaminants on the strainer or filter; and,
(iii) Be equipped with a bypass system that will permit lubricant to continue to flow at the normal rate if the strainer or filter is completely blocked. In addition, the bypass system should be designed so that contaminants, that have collected on the filter, will not enter the bypass flow path when the system is in the bypass mode.
(3) Section 29.1027(b)(2) requires a screen at the outlet of each lubricant tank or sump that supplies lubrication to rotor drive systems and rotor drive system components. The screen should remove any object that might obstruct the flow of Page E - 135
lubricant to the filter required by § 29.1027(b)(1). The requirements of § 29.1027(b)(1) do not apply to the tank outlet screen.
(4) Splash-type lubrication systems for rotor drive system gearboxes should comply with §§ 29.1021 and 29.1337(d).
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SUBPART E - POWERPLANT
COOLING AC 29.1041. § 29.1041 COOLING - GENERAL.
a. Background.
(1) Few substantive changes have been made to the cooling provision requirements, §§ 29.1041 through 29.1049, since the rules were defined in the Civil Air Regulations, Part 7, effective August 1, 1956. Testing procedures utilized have not precisely followed those rigorously set forth in §§ 29.1045 through 29.1049 as industry and the FAA/AUTHORITY have recognized the need to vary procedures slightly to accomplish the practical test objectives.
(2) In the paragraphs which follow, the cooling regulations will be explained, and in some instances where the regulations provide specific procedures, “alternative procedures” which have been found acceptable in achieving the rule objectives will be presented. The intent of providing those alternative procedures is not to promulg ate new regulations, but rather to provide recognized, accepted procedures for compliance with the objective of the current standards.
b. Explanation.
(1) The rotorcraft design should provide for cooling to maintain the temperatures of all powerplant, auxiliary power unit, and power transmission components and fluids within the limitations established for these items.
(2) Cooling provisions should be adequate for shutdown and for water, ground, and flight operating conditions.
(3) The adequacy of the cooling provisions should be demonstrated by flight testing.
c. Procedures.
(1) Detailed procedures for the demonstration of climb, takeoff and climb, and hover cooling are given in §§ 29.1045 through 29.1049. Other test conditions and procedures necessary to demonstrate adequate cooling for water, ground, flight, and shutdown conditions must be negotiated between the applicant and the FAA/AUTHORITY certification engineer. A cooling test proposal which defines the agreed test points and procedures should be prepared well in advance of the official certification testing.
(2) The test conditions selected, in addition to those in §§ 29.1045 through
29.1049, would typically include cruise at various airspeeds and altitudes, shutdown Page E - 137