Annex 8 - Procedures for Demonstration of Operational Safety

 This annex applies to all craft.

Tests to evaluate operational safety should be conducted on the prototype craft of a new design or of a design incorporating new features which may modify the results of a previous testing. The test should be carried out to a schedule agreed between the Administration and the manufacturer.

Where conditions of service warrant additional testing (e.g. low temperature), the Administration or base port State authorities, as appropriate, may require further demonstrations. Functional descriptions, technical and system specifications relevant to understanding and evaluation of craft performance should be available.

The object of these tests is to provide essential information and guidance to enable the craft to be operated safely under normal and emergency conditions within the design envelope of take-off mass, centre of gravity, speed and environmental conditions.

The following procedures should be applied for the verification of craft performance.

1 Definitions

1.1 Normal operating conditions

The wind and sea conditions in which the craft can safely operate at any heading and if in ground effect, at any allowable altitude while operated manually with auto-pilot assistance or with any automatic control system in normal mode.

1.2 Worst intended conditions

Has the meaning defined in part A of these Guidelines.

1.3 Minor effect

Has the meaning defined in part C of these Guidelines.

1.4 Tolerable risk

Level of risk, whereby the combination of the probability and likely consequences of an event can be demonstrated as acceptable to the Administration. This demonstration may be through actual trial or by risk analysis as described in part C of these Guidelines.

1.5 Flight-trim

To be interpreted as defined in chapter 16 of part B of these Guidelines.

1.6 Flight-trim speed

Speed to which a flight-trimmed craft will return after being disturbed by an external force.

1.7 Flight-trim angle

Angle to which a flight-trimmed craft will return after being disturbed by an external force.

1.8 Minimum normal ground effect speed

Lowest speed at which craft can be operated in ground effect throughout proven load and stability range, allowing sufficient safety margin for reasonable foreseeable transient variations in operating conditions.

1.9 Maximum normal ground effect speed

Highest speed at which the craft is normally operated in ground effect through its proven load and stability range allowing sufficient safety margin for reasonable foreseeable transient variations in operating conditions.

1.10 Maximum safe speed

The maximum speed at which the craft will continue to demonstrate safe stability characteristics. This speed should be no less than midway between maximum normal ground effect speed and absolute maximum craft speed.

1.11 Absolute maximum craft speed

Speed beyond which craft aerodynamic stability in ground effect cannot be assured. Craft controllability may also be jeopardised beyond this speed.

1.12 Landing speed range

Range of speeds that allow operator to maintain craft control throughout a landing manoeuvre.

2 General

2.1 The craft should meet the applicable operational provisions in chapter 16 of part B of these Guidelines and this annex for all extremes of passenger and load configurations for which certification is required. The limiting sea state related to the different modes of operation should be verified by tests and analyses of a craft of the type for which certification is requested.

2.2 Operational control of the craft should be in accordance with procedures established by the owner or operator for operation in service. Procedures should be established for starting and shutting down the craft, moving the craft on the ground, transferring it to and from the water, and operating in displacement, transition, planing, take-off/landing, ground effect and any other airborne modes.

2.3 The procedures established under 2.2 should:

• .1 demonstrate that normal manoeuvres and craft responses to failures are consistent in performance;

• .2 use methods or devices that are safe and reliable; and

• .3 include allowance for any time lag in the execution of procedures that may reasonably be expected in service.

2.4 Procedures required by this annex should be conducted over water of sufficient depth so that craft performance will not be affected.

2.5 Tests should be conducted through a range of mass and centre of gravity configurations sufficient to establish a safe operating envelope for every craft.

2.6 Testing should be conducted through a range of wind and sea conditions sufficient to establish a safe operating envelope for the craft in all of the circumstances described in 2.2.

2.7 No manoeuvre during either normal or emergency operations should require exceptional operator skill or excessive force on the craft controls.

2.8 The test regime assumes that passengers and cargo are secured during the transition, planing and take-off and landing stages of craft operation.

3 Performance trials

Tests are to be conducted in all modes of operation under the range of conditions described in 2.5 and 2.6.

3.1 Ground operations

For craft intended to be controlled by the operator when on the ground, the following criteria should be met:

• .1 The craft should demonstrate a stable attitude on flat ground when manoeuvring on its undercarriage. The limit of gradient up or down which the craft may safely be manoeuvred should be established.

• .2 The craft should not show any tendency to spin horizontally in cross winds up to the designed maximum wind velocity.

• .3 Operation of wheel brakes, if fitted, should not cause the craft to pitch nose down or spin horizontally.

3.2 Displacement mode

The following tests should be conducted to establish and/or confirm craft performance parameters in displacement mode:

• .1 Establish that the craft freeboard meets design and regulatory specifications.

• .2 Propulsion systems: Tests should be conducted to confirm that procedures for starting, engaging, disengaging, stopping are safe and effective.

• .3 Establish maximum safe operating speeds in both normal and worst intended conditions.

• .4 Determine turning radius and rate of turn.

• .5 Establish and confirm stopping distance and procedures in both normal and emergency situations.

• .6 Confirm berthing and anchoring procedures can be performed safely.

• .7 Establish/confirm the effects of failures as described in 4.3, appropriate for the displacement mode, and procedures to deal with failures.

3.3 Transition mode

The following tests should be conducted to establish and/or confirm performance parameters as the craft moves from displacement to planing mode:

• .1 Establish the speed at which the craft transits to planing mode in the range of configurations and conditions described in 2.5 and 2.6.

• .2 Confirm that the craft is stable and controllable during transition.

• .3 Determine procedures for safe transition to planing mode.

• .4 Establish/confirm the effects of failures as described in 4.3, appropriate for the transition mode, and procedures to deal with failures.

3.4 Planing mode

The following tests should be conducted to establish and/or confirm performance parameters for craft in planing mode:

• .1 Establish the range of speeds at which the craft will operate in planing mode in both normal and worst intended operating conditions.

• .2 Determine the range of loading conditions for which the craft displays a safe and stable condition.

• .3 Establish maximum velocity of 90º cross wind in which craft is controllable.

• .4 Determine maximum rate of turn and minimum turn radius in both normal and worst intended operating conditions.

• .5 Confirm that water spray does not impair operator visibility.

• .6 Establish/confirm procedures for safe operation of the craft in planing mode.

• .7 Establish/confirm the effects of failures as described in 4.3, appropriate for the planing mode, and procedures to deal with failures.

3.5 Take-off

The following tests should be conducted to establish and/or confirm craft performance parameters during take-off:

• .1 Establish the speeds at which the craft takes off over the range of load configurations in normal and worst intended conditions.

• .2 Determine the distance, from rest, to achieve take-off in the range of conditions described in 3.5.1.

• .3 Confirm that craft is aerodynamically stable and controllable during take-off.

• .4 Confirm that surface impacts during take-off do not cause horizontal or vertical accelerations that are likely to have more than a minor effect on craft or personnel.

• .5 Establish/confirm maximum velocity of 90º cross wind in which craft can safely take-off.

• .6 Confirm that water spray does not impair operator visibility.

• .7 Establish/confirm operating procedures to ensure a safe take-off manoeuvre is performed.

• .8 Establish/confirm the effects of failures as described in 4.3, appropriate for the take-off mode, and procedures to deal with failures.

3.6 Ground effect mode

The following tests should be conducted to establish and/or confirm craft performance parameters in ground effect:

• .1 Determine the range of loading conditions for which the craft is stable about its three primary axes.

• .2 The following control criteria must be demonstrated when the craft is flight-trimmed in ground effect mode:

  • .1 Elevator controls should have the following characteristics for all speeds within the craft's normal ground effect speed range:

    A push on the elevator control should cause the craft to flight-trim forward and increase speed from its previous flight-trim angle and speed. A pull should have the opposite effect. Airspeed and flight-trim angle should return to within 10% of original flight-trim speed and angle when the elevator control pressure is released.

  • .2 Longitudinal control must be demonstrated as follows:

    The elevator control force/speed curve must have a stable slope at all speeds within a range which is the greater of 15% of the flight-trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speed range, above and below the flight-trim speed (except that the speed range need not include speeds below minimum normal ground effect speed or greater than maximum safe speed, nor speeds that require an elevator control force of more than 20 kg), with:

    • .1 the centre of gravity in the most adverse position;

    • .2 the most critical weight between the maximum take-off and maximum landing weights;

    • .3 75% of maximum continuous power for reciprocating engines or for turbine engines, the maximum cruising power selected by the applicant as an operating limitation, except that the power need not exceed that required at maximum normal safe ground effect speed; and

    • .4 the craft flight flight-trimmed for level flight with the power required in .3 above.

  • .3 Lateral-directional control

    The rudder control force/speed curve gradient must meet requirements through the speed range between maximum normal ground effect speed and maximum safe speed, except that the dihedral effect (aileron deflection opposite the corresponding rudder input) may be negative, provided the divergence is gradual, easily recognised, and easily controlled by the operator.

  • .4 Any short period oscillation about any single axis, which occurs within the normal ground effect speed range, must be substantially dampened with the primary controls both free and in a fixed position. Any combined lateral-directional oscillation, which occur within the normal ground effect speed range must be positively dampened with the controls free and must be controllable with the primary controls without requiring exceptional operator skills.

• .3 Determine the controllability of the craft when out of flight-trim in accordance with:

  From an initial condition with the craft flight-trimmed within normal ground effect speed range the craft must have satisfactory manoeuvring stability and controllability with the degree of out-of-flight-trim in the craft nose-up direction which results from the greater of:

  • .1 a three-second movement of the longitudinal flight-trim system at its normal rate for the particular flight condition with no aerodynamic load (or an equivalent degree of flight-trim for craft that do not have a power-operated flight-trim system), except as limited by stops in the flight-trim system; and

  • .2 the maximum flight mis-flight-trim that can be sustained by the autopilot, if fitted, while maintaining level flight in the high-speed ground effect condition.

• .4 Craft speed

  • .1 Determine the range of safe operating speeds at which the craft will operate in ground effect mode in both normal and worst intended conditions.

  • .2 Investigate relationship between craft speed and altitude in ground effect mode.

  • .3 The following speed increase and recovery characteristics must be met:

    • .1 Operating conditions and characteristics likely to cause inadvertent speed increases (including upsets in pitch and roll) must be simulated with the craft flight-trimmed at any speed within the normal ground effect speed range. These conditions and characteristics include gust upsets, inadvertent control movements, low control force gradient in relation to control friction and passenger movement.

    • .2 Allowing for operator reaction time after effective inherent or artificial speed warning occurs, it must be shown that the craft can be recovered to a normal attitude and its speed reduced to maximum normal ground effect speed, without:

      • .1 exceptional operator strength or skill;

      • .2 exceeding the absolute maximum craft speed or its structural limitations; and

      • .3 buffeting that would impair the operator's ability to read the instruments or control the craft for recovery.

    • .3 With the craft flight-trimmed at any speed up to maximum normal ground effect speed, there must be no reversal of the response to control input about any axis at any speed up to maximum safe speed. Any tendency to pitch, roll, or yaw must be mild and readily controllable, using normal operating techniques. When the craft is flight-trimmed at maximum normal ground effect speed, the slope of the elevator control force/speed curve need not be stable at speeds greater than maximum safe speed, but there must be a push force at all speeds to absolute maximum craft speed and there must be no sudden or excessive reduction of elevator control force as that speed is reached.

• .5 Turning

  Determine the following characteristics in normal and worst intended operating conditions:

  • .1 maximum safe angle of bank;

  • .2 maximum rate of turn; and

  • .3 minimum turn radius.

• .6 Confirm that the maximum change of lateral or longitudinal centre of gravity that may be caused by the movement of passengers or cargo, is able to be counteracted with operator control input.

• .7 Establish/confirm the effects of failures as described in 4.3, appropriate for the ground effect mode, and procedures to deal with failures.

3.7 Landing

The following tests should be conducted to establish and/or confirm craft performance parameters during landing:

• .1 Determine the minimum distance required in normal and worst intended conditions to perform the landings specified below. The distance should be measured from the point of touchdown to the position of the craft when stopped:

  • .1 normal landing;

  • .2 emergency landing; and

  • .3 power-off landing.

• .2 Confirm that the craft is stable and controllable throughout the landing phase.

  The elevator control force/speed curve must have a stable slope, and the force may not exceed 35 kg, through the range of speeds specified as acceptable for landing with:

  • .1 maximum landing weight;

  • .2 power or thrust off on the engines; and

  • .3 the craft flight-trimmed for minimum normal ground effect speed with power or thrust off.

• .3 Confirm that surface impacts during landing on flat water do not cause horizontal or vertical acceleration that are likely to have more than a minor effect on the craft or personnel.

• .4 Perform a "hands-free" landing from steady state flight in ground effect mode to simulate total loss of ability to manipulate the control surfaces in fixed position when power-off.

• .5 Establish/confirm maximum velocity of 90º cross wind in which the craft can land safely.

• .6 Confirm that spray does not impair operator visibility.

• .7 Establish/confirm operating procedures for normal emergency and power off landing.

• .8 Establish/confirm the effects of failures as described in 4.3, appropriate for the transition mode, and procedures to deal with failures.

4 Effects of failures or malfunctions

4.1 General

4.1.1 The limits of safe operation, special handling procedures and any operational restrictions should be examined and developed as a result of full-scale trials conducted by simulating possible equipment failures.

4.1.2 The failures to be examined should be those leading to major or more severe effects as determined from the evaluation of the SSA in accordance with part C of these Guidelines.

4.1.3 Failures to be examined should be agreed between the craft manufacturer and the Administration and each single failure should be examined in a progressive manner.

4.1.4 The failures to be examined should be single failure events unless a single failure has an immediate and inevitable secondary effect.

4.1.5 If the manufacturer or Administration believes that a simulation of any failure or malfunction could endanger the craft or personnel, the effects of that failure or malfunction may be deduced by calculation and/or analysis in accordance with part C of these Guidelines. In the event, the Administration may require that systems or procedures be introduced or changed to reduce the risk to a tolerable level or may impose operational limits to achieve the same result.

4.2 Objectives of tests

Examination of each failure should result in:

• .1 Determining safe limits of craft operation at the time of failure or malfunction beyond which the failure or malfunction will result in a degradation of safety beyond a tolerable level.

• .2 Determining crew members' actions, if any, to minimize or counter the effect of the failure.

• .3 Determining craft or machinery restrictions to be observed with the failure present to enable the craft to continue to provide a place of refuge in the case of assisted and cargo craft and to enable the craft to continue to a place of refuge in the case of unassisted craft.

4.3 Failures to be examined

Equipment failures should include, but not be limited to, the following:

• .1 total loss of propulsion power;

• .2 total loss of lift power;

• .3 total failure of control of one propulsion system;

• .4 involuntary application of full propulsion thrust (positive or negative) on one system;

• .5 failure of control of one directional control system;

• .6 involuntary full deflection of one directional control system;

• .7 failure of control of flight-trim control system;

• .8 involuntary full deflection of one flight-trim control system element;

• .9 total loss of electrical power; and

• .10 loss of flight instrumentation.

4.4 "Dead ship" test

In order to establish craft motions and direction of laying to wind and waves, for the purpose of determining the conditions of a craft evacuation, the craft should be stopped and all main machinery shut down for sufficient time that the craft's heading relative to wind and waves has stabilised. This test should be carried out on an opportunity basis to establish patterns of the design's "dead ship" behaviour under a variety of wind and sea states.

4.5 Operating compartment functionality

Prior to and throughout the trial program a qualitative evaluation should be conducted as to the contribution of the operating compartment layout to the safe operation of the craft. Particular attention should be paid to the following:

• .1 operator comfort to minimise fatigue including noise, vibration levels, temperature and ventilation control;

• .2 visibility from operating position including any obstructions;

• .3 location of and forces required to operate primary controls;

• .4 accuracy and readability of all instrumentation; and

• .5 ease of use and interpretation of navigation and collision avoidance systems.