Section 5 Air propellers and lift fans
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules for the Classification of Air Cushion Vehicles, July 2022 - Chapter 4 Machinery - Section 5 Air propellers and lift fans

Section 5 Air propellers and lift fans

Parent topic: Chapter 4 Machinery

5.1 General requirements

5.1.1 This Section is to be read in conjunction with the General Requirements for Machinery in SSC RulesPt 9, Ch 1 General Requirements for Machinery.

5.1.2  The propeller or lift fan when suitably mounted and operated in accordance with the declared rating and operational limitations as required by CS-P 50, shall be of sufficient strength and stiffness to withstand the most adverse combination of loads which can arise during its use without exceeding acceptable stress levels. LR is to be notified of any limiting conditions associated with such equipment, e.g. icing limits.

5.1.3 Except for the requirements of 5.2, propellers are to be designed, constructed and tested in accordance with the requirements of European Aviation Safety Agency (EASA) Certification Specifications for Propellers CS-P. Other industry equivalent standards may be accepted in agreement with LR.

5.1.4 Lift fans are generally to be designed, constructed and tested in accordance with the requirements of European Aviation Safety Agency (EASA) Certification Specifications for Propellers (CS-P) as applicable. Other industry equivalent standards may be accepted in agreement with LR.

5.1.5 Organisation(s) responsible for design, construction and testing of propellers and lift fans are to be certified in accordance with EASA Part 21. Design Organisations and Production Organisations are to hold Design Organisation Approval and Production Organisation Approval respectively. It is to be demonstrated to LR that the required working practices are being applied throughout the organisation.

5.1.6 Air propellers and lift fans are to be installed and balanced in accordance with the EASA Part 21 'approved' manufacturer's requirements, taking into account the Instructions for Propeller Installation and Operation required by CS-P 30.

5.1.7 Air propellers are to be inspected and maintained in accordance with approved Manuals required by CS-P 40, Service Management Plan required by CS-P 160 and Service Bulletins produced by the EASA Part 21 'approved' manufacturer. Any organisation and personnel involved in maintenance is to be certified and act in accordance with the requirements of EASA Part 145. The maintenance organisation is to be also licensed by the propeller manufacturer for the propeller ‘type’.

5.1.8  Propellers and lift fans are to be capable of functioning satisfactorily without unacceptable damage when operated in the likely prevailing conditions of icing, spray, sand, aggregate, salt etc. Due regard shall be paid to effects of corrosion, electrolytic action between different metals, erosion or cavitation which may result from operation in the environments to which they are subjected. Materials particularly susceptible to the marine environment are to be avoided.

5.1.9 Materials for propellers and lift fans which comply with National or proprietary specifications may be accepted in lieu of those required by the Rules for Materials provided that they are approved by LR for the specific application.

5.1.10 Where aerospace grade aluminium alloy materials are proposed, specific consideration shall be given to their protection from corrosion in the marine environments in which they are intended to operate.

5.1.11 A compliance matrix detailing how the requirements for propellers and lift fans are to be verified is to be agreed with LR prior to production of propellers and lift fans. Any documentation referenced within the matrix which provides evidence of compliance is to be made available to LR on request.

5.1.12 A record of all work carried out on the air propeller is to be maintained. The record is to include details and authorisation of the persons carrying out this work. The scope of work permitted for on-board maintenance is to be defined by the Part 21 approved manufacturer.

5.1.13 Non-destructive examination of propeller and lift fan equipment is to be carried out by organisations and personnel approved in accordance with EN 4179:2009, Aerospace series. Qualification and approval of personnel for non-destructive testing, or a recognised equivalent 'standard' acceptable to LR.

5.1.14 For multi-propeller ACVs, with one air propeller or lift fan out of action, the ACV is to be capable of maintaining steerage. Propulsion systems comprising single essential components will be specially considered.

5.1.15 The failure of one air propeller or lift fan, or its control system, shall not render any other air propeller or lift fan inoperative.

5.2 Endurance testing

5.2.1  Endurance tests on the Propeller System type must be made on a representative engine and in accordance with Ch 4, 5.2 Endurance testing 5.2.2 or Ch 4, 5.2 Endurance testing 5.2.3, as applicable, without evidence of failure or malfunction. An analysis based on tests of Propellers of similar design may be used in place of the tests of Ch 4, 5.2 Endurance testing 5.2.2 and Ch 4, 5.2 Endurance testing 5.2.3.

5.2.2 Fixed Pitch Propellers and Adjustable Pitch Propellers must be subjected to one of the following tests:

  1. A 50-hour test where the Propeller must be operated at maximum power and rotational speed during at least five hours of this test, and at not less than 90 percent of the maximum power and rotational speed for the remainder of the 50 hours.

  2. A 50-hour test where the Propeller must be operated at maximum continuous power and rotational speed.

5.2.3 Variable Pitch Propellers must be subjected to the following tests:

  1. A 110-hour endurance test which must include the following conditions:

    1. 5 hours at maximum continuous power and rotational speed, and thirty 10-minute cycles composed of:

      • Acceleration from idle,
      • 5 minutes at maximum power and rotational speed,
      • Deceleration, and
      • 5 minutes at idle

    2. 50 hours at maximum continuous power and rotational speed

    3. 50 hours, consisting of ten 5-hour cycles composed of:

      • 5 accelerations and decelerations between idle and maximum power and rotational speed,
      • 4,5 hours at approximately even incremental conditions from idle up to, but not including maximum continuous power and rotational speed, and
      • 30 minutes at idle.
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