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Chapter 7 - Main Machinery

701. Definition  

Main machinery means all components used in the generation, transmission and conversion of power for lift and propulsion of the vehicle.

702. Main engines  

Main engines shall be installed such that they are provided with adequate services to ensure that no operating limitations to which they may be subject shall be exceeded.

703. In submitting date for approval, the designer shall include all engine manufacturer's design and test data relating to weight, power-torque-speed characteristics, safety devices, any recommended limitations, and any special installation or operating requirements or instructions relating to the particular variant or model of the engine proposed. The information shall include details of any previous certification or approval issued in respect of the engine model or variant.

704. Any engine design proposed, which has not previously been used in an A.C.V. or essentially similar installation, or which requires modification affecting it's structural integrity oroperating characteristics will require the provision of additional data as appropriate. Applicable engine testing may be required.

705. In designing the engine and transmission installation, the designer shall ensure that the engine output characteristics in terms of power, torque, speed and vibration will not induce any resonant vibrations or fluctuations throughout the power transmission system which would lead to premature component failure or structural damage throughout the engine operating envelope.

706. All services provided to a main engine shall include adequate protection against contamination, erosion and icing of the engine and of air, fuel, coolants and lubricants supplied to it.

707. In designs employing multiple engines or engines containing coupled power-packs, arrangements shall be made to ensure that the failure of one engine or power-pack, or of services supplying the engine or power-pack, may be isolated to permit continued operation of remaining engines or power-packs.

708. All engines shall be provided with warning and protection devices which will activate in the event of approved limitations being exceeded. Such devices should include, where applicable, engine r.p.m., power, torque, oil temperature or pressure, coolant temperature, and exhaust gas temperature. Warnings shall be provided at any station from which the engine may be controlled; protection devices should not shut the engine down except where it is essential to avoid immediate hazard to safety of the vehicle and occupants. Any undesirable effects resulting from the operation of a protection device are to be declared.

709. Main engines containing high-energy rotors shall be designed and installed so as to minimise damage or injury in the event of a rotor or engine failure.

710. All main engines shall be installed within Designated Fire Zones; multiple engine installations may be approved within one Designated Fire Zone subject to satisfactory arrangements for fire containment and suppression. (See Chapter 10).

711. The design of all exhausts of hot or noxious fluids and gases shall ensure minimum risk of damage to structure or components and injury to personnel; no such fluids shall be exhausted into the cushion. Where exhausts penetrate any vehicle structure, adequate insulation or shielding shall be provided. No exhaust shall be positioned such that failure or leakage could adversely affect the normal operation of controls, and discharges shall be so sited that exhaust fluids cannot be re-ingested into the vehicle or cushion. Any exhaust, the lowest point of which discharges less than 76 mm. above the surface of the water when the vehicle is floating at maximum certified weight shall be provided with means to prevent the ingress of water. (See also 1070)

712. The designer shall ensure that all appropriate measures have been taken by the engine manufacturer, and in the engine installation design, to minimise the effects of salt ingestion by the engine on it's operation, and generally to protect the engine from corrosion.

713. The designer shall establish with the engine manufacturer that design of the engine installation and of services to the engine are satisfactory for operation of the engine within established limitations.

714. The engine installation shall be such as to minimize any adverse effect upon it's operation of the failure of any component driven by it.

715 All engines and their accessories shall be mounted and secured such that they shall not break loose under the acceleration loadings quoted in Section 506.

716. Engine and engine accessory mountings and couplings shall ensure that the effects of any engine vibrations upon vehicle structure or other components are minimized.

717. All engines shall be installed such that any excess fuel or oil supplied to them is contained and drained to a safe fire-resistant receptacle.

718. The designer shall submit a fault analysis to indicate the effect of all likely faults of main machinery components and controls upon vehicle operational safety.

719. All machinery spaces containing main machinery components shall be adequately ventilated to disperse any accumulations of toxic, noxious or inflammable vapours. Designated Fire Zones containing engines shall have additional ventilation arrangements (see Chapter 10).

720. Any machinery space which may be entered by crew members while the vehicle is operating shall be treated to reduce noise levels as far as practical, and shall be provided with 2-way communication with the crew station from which the vehicle is normally maneuvered.

721. When Diesel engines are used as main machinery, fuel injector pipes shall either be double-walled or arranged so that, in the event of a leak or failure, the leaking fuel is contained and drained to a safe receptacle which is provided with a remote-reading level indicator displayed in the compartment from which the vehicle is normally maneuvered.

722. Diesel engines with a cylinder diameter in excess of 200 mm. or a crankcase volume in excess of 0.6 cu.m. are to be fitted with adequate crankcase explosion relief valves oriented so as to minimize the risk of damage and of injury to personnel.

723. Any arrangements for compressed air systems for starting or controlling Diesel or other engines shall be submitted for approval, with particular reference to precautions against fire and explosion.

724. The engine installation shall ensure that adequate lubrication and cooling is provided to maintain the engine within recommended limits under all normal and emergency motions and attitudes of the vehicle. Lubrication and cooling systems shall include appropriate warnings in the event of failure.

725. Engines and components to which liquid systems are connected shall be so installed and arranged that any leakage from a liquid system will drain to a receptacle containing an automatic bilge alarm providing indication at the station from which the vehicles normally maneuvered.

726. Controls for all main engines and permanently installed Auxiliary Power Units shall be provided in the compartment from which the vehicle is normally maneuvered such that power output may be varied and maintained within approved limits. At least two means of stopping engines, using controls connected directly to the engine, shall be provided; one shall be an emergency shut-down. Any undesirable effects resulting from operation of the emergency shut-down device shall be declared.

730. Starting Systems. 

Installed sources of stored energy intended for use in starting main engines or auxiliary power units shall be of sufficient capacity to permit, without replenishment, 3 consecutive attempts to start any engine or auxiliary power unit to which it may be connected when following the engine or power unit manufacturer's recommended starting procedure.

731. Where starting of an engine or auxiliary power unit is dependent, in the absence of any other power source, upon such a source of stored energy, means shall be provided for replenishing the stored energy and maintaining it while the vehicle is in normal operation.

732. The starting system shall remain effective under conditions of failure of normal electrical power supply, and with the vehicle in any attitude as a result of damage considered in Chapter 3.

740. Fans. 

The installation of any fans designed for lift or propulsion shall be designed to minimize loss of performance due to obstructions, provided that adequate provision is made to safeguard intakes from ingesting foreign objects and to minimize the risk of injury. The effects of intake icing shall be considered.

741. In submitting design data for approval, the designer shall include fan manufacturer's design and test data relating to structural integrity, pressure-flow characteristic, power absorption and maximum speed. Any manufacturer's recommended operating limitations and special installation instructions or requirements shall also be included.

742. Fan installations shall be designed so as to minimize the risk of damage to the vehicle or injury to occupants in the event of disintegration. Where this is not achieved by physical separation or position, appropriate energy-absorbing physical protection may be required.

743. Any fan design proposed which has not previously been used in an A.C.V. or an essentially similar installation, or which requires modification affecting it's structural integrity or operating characteristics, shall be subject to an over speed test of 120% the maximum intended operating speed for at least 30 seconds. Where an existing fan design has been modified, details of the modifications shall be provided.

744. In designs incorporating the use of multiple lift fans, the installation shall include provision for preventing loss of lift air in the event of one lift system being inoperative.

745. Fans shall be so installed as to minimize damage due to contact with water.

746. The installation of fans shall make adequate provision to minimize the onset of corrosion and erosion.

Propellors 

760. Propellors shall be installed so that the swept area of the propellor disc is totally within the platforms boundary of the vehicle.

761. In submitting design data for approval, the designer shall include propellor manufacturer's design and test data relating to structural integrity, power absorption, thrust characteristics and maximum speed. Any manufacturer's recommended operating limitations and special installation instructions or requirements shall also be included.

762. The installation shall provide adequate safeguards against the ingestion of foreign objects and to minimise the risk of injury; the effects of icing shall be considered.

763. The installation shall be designed to provide as free inlet conditions as practical, and shall minimise the possibility of cyclic loading due to inlet turbulence.

764. Any propellor design proposed which has not previously been used in an A.C.V. or an essentially similar installation, or which requires modification affecting it's structural integrity or operating characteristics shall be subject to an overspeed test of 120% maximum intended operating speed for at least 30 seconds. Where an existing propellor design has been modified, details of the modification shall be provided.

765. Propellor manufacturers shall make adequate provision to minimise the effects of erosion of blades on structural integrity and performance.

766. The installation of propellors shall include measures to minimise the effects of corrosion, galvanic action or cavitation.

Transmissions 

780. The designer shall provide data as appropriate from the manufacturer of any gearbox, belt, clutch or coupling, the integrity of which under the intended service conditions is essential for the safe operation of the main machinery. Such data should relate to structural integrity, power loadings and speeds, and should include any manufacturer's recommended operating limitations or special installation requirements or instructions.

781. Design calculations for all shafting shall be submitted; first order critical (whirling) speed shall be not less than 110% the shaft maximum designed operating speed.

782. All transmission components shall be provided with adequate safeguards to prevent injury to personnel when operating, and to prevent injury or damage in the event of a failure.

783. No transmission components shall be situated in, or pass through, compartments normally occupied by passengers or crew members.

784. Components, or assemblies of components, of transmission systems may be required to be subjected to an agreed test schedule.

785. Selection and installation of any clutch shall ensure that normal engagement does not induce abnormally high stresses in the system; the system should also provide safeguards against dangerously high stresses being generated by inadvertent operation of the clutch.

786. Transmission systems shall, to the maximum extent practicable, incorporate safeguards such that a single failure in the system will not result in progressive damage which may hazard the safety of the vehicle or it's occupants.

787. Any lubrication system upon which the transmission depends for it's safe operation shall be designed and installed to ensure operation within recommended limits, and shall incorporate a warning device displaying at the vehicle control position.

Machinery Installation Testing. 

790. Any machinery testing required by previous sections of Chapter 7 - e.g. 704, 743, 764, 784 - shall relate to the individual integrity of the machinery component.

791. Additionally, testing shall be carried out of all machinerywhen installed in the vehicle. Such testing will be to an agreed schedule consistent with the configuration of the installation, specifically relating to demonstrating the structural integrity of the machinery in the designed installation under all conditions of the operating envelope of the machinery.

792. The test schedule referred to in 791 shall include tests to demonstrate, where applicable :-

1. Full and adequate control and governing of engine and power train components throughout the machinery operating envelope;
   
   
2. Adequate provision of cooling and ventilation media to ensure that approved limitations are not exceeded within the operational and environmental envelopes of the vehicle;
   
   
3. Freedom of all components of power trains when installed in the vehicle and operating at any point within the machinery approved limitations from any power surges, engine stalls and vibratory resonances likely to cause component or structural mounting failure;
   
   
4. Effectiveness of all warning and protection devices installed, including engine emergency shut-down.

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