Appendix A to GM1 21L.A.63 Classification of changes to a type certificate

EXAMPLES OF MAJOR CHANGES PER DISCIPLINE The information below is intended to provide a few examples of major changes per discipline, resulting from the application of point 21L.A.63 and point 3.3 below. It is not intended to present a comprehensive list of all major changes. Examples are categorised per discipline and are applicable to all products (aircraft, engines, propellers). However, a particular change may involve more than one discipline, e.g. a change to engine controls may be covered in engines and systems (software). Those involved in the classification of changes should always be aware of the interaction between disciplines and the consequences this will have when assessing the effects of a change (i.e. operations and structures, systems and structures, systems and systems, etc.). Specific rules may exist which override the guidance of these examples. In Part 21 Light, a negative definition is given of minor changes only. However, in the following list of examples, it was preferred to give examples of major changes. Where in this list of examples the words ‘has effect’ or ‘affect(s)’ are used, they have always to be understood as being the opposite of ‘no appreciable effect’ as in the definition of minor change in point 21L.A.63. Strictly speaking, the phrases ‘has appreciable effect’ and ‘appreciably affect(s)’ should have been used, but this has not been done to improve readability.

1.Structure

(i)Changes such as a change of dihedral, addition of floats.

(ii)Changes to materials, processes or methods of manufacture of primary structural elements, such as spars, frames and critical parts.

(iii)Changes that adversely affect fatigue or damage tolerance or life-limit characteristics.

(iv)Changes that adversely affect aeroelastic characteristics.

2.Cabin safety

(i)Changes which introduce a new cabin layout of sufficient change to require a reassessment of the emergency evacuation capability, or changes which adversely affect other aspects of passenger or crew safety. Items to consider include but are not limited to: changes to or introduction of dynamically tested seats; changes to cabin layouts that affect evacuation path or access to exits; changes to the cabin area in striking distance of the occupant’s head or torso introducing potentially injurious objects

3.Flight Changes which adversely affect the approved performance or brake changes that affect braking performance. Changes which adversely affect the flight envelope. Changes which adversely affect the handling qualities of the product, including changes to the flight controls function (gains adjustments, functional modification to software), or changes to the flight protection or warning system.

4.Systems For systems assessed under CS 23.2510, the classification process is based on the functional aspects of the change and its potential effects on safety.

(i)Where the failure effect is ‘catastrophic’ or ‘hazardous’, the change should be classified as ‘major’.

(ii)Where the failure effect is ‘major’, the change should be classified as ‘major’ if: aspects of the compliance demonstration will use a means that has not been previously accepted for the nature of the change to the system; or the change affects the pilot–system interface (displays, controls, approved procedures); or the change introduces new types of functions/systems such as GPS primary, TCAS, predictive windshear, HUD. The assessment of the criteria for software changes to systems should also be performed. When software is involved, account should be taken also of the following guidelines: Where a change is made to software produced in accordance with the guidelines of the latest edition of AMC 20-115 (see AMC-20 document), the change should be classified as ‘major’ if either of the following applies, and the failure effect is ‘catastrophic’, ‘hazardous’ or ‘major’:

(i)the executable code for software, determined to be Level A or Level B in accordance with the guidelines, is changed unless that change involves only a variation of a parameter value within a range already verified for the previous certification standard; or

(ii)the software is upgraded to or downgraded from Level A, Level B or Level C; or

(iii)the executable code, determined to be level C, is deeply changed, e.g. after a software re-engineering process accompanying a change of processor. For software developed to guidelines other than the latest edition of AMC 20-115, the applicant should assess the changes in accordance with the foregoing principles. For other codes, the principles noted above may be used. However, due consideration should be given to specific certification specifications/interpretations. For example: Opening and listening on a User Datagram Protocol (UDP) port in an end system of an already certified topology. Activating a protocol in a point-to-point communication channel. The modification of a service between a system of a more closed, controlled security domain and a system of a more open, less controlled security domain. The modification of a security control between a system of a more closed, controlled information security domain and a system of a more open, less controlled security domain.

5.Propellers Changes to: diameter, aerofoil, planform, material, blade retention system, etc.

6.Engines Changes:

(i)that adversely affect operating speeds, temperatures, and other limitations;

(ii)that affect or introduce parts identified by CS E-510 where the failure effect has been shown to be ‘hazardous’;

(iii)that affect or introduce engine critical parts (CS E-515) or their life-limits.

(iv)to a structural part which requires a resubstantiation of the fatigue and static load determination used during certification;

(v)to any part of the engine which adversely affects the existing containment capability of the structure;

(vi)that adversely affect the fuel, oil and air systems, which alter the method of operation, or require reinvestigation against the type-certification basis;

(vii)that introduce new materials or processes, particularly on critical components.

7.Rotors and drive systems Changes that:

(i)adversely affect fatigue evaluation unless the service life or inspection interval is unchanged; this includes changes to materials, processes or methods of manufacture of parts, such as rotor blades, rotor hubs including dampers and controls, gears, drive shafts, couplings;

(ii)affect systems whose failure may have ‘hazardous’ or ‘catastrophic’ effects; the design assessment should include: the cooling system, the lubrication system, rotor controls;

(iii)adversely affect the results of the rotor drive system endurance test, the rotor drive system being defined in CS 27.917;

(iv)adversely affect the results of the shafting critical speed analysis required by CS 27.931.

8.Noise and emissions The examples provided below are not exhaustive and will not, in every case, result in an appreciable effect on the certified noise or emissions levels and, therefore, will not per se and in every case result in a major change classification.

(i)Examples of noise-related changes that might lead to a major change classification are:

(1)for propeller-driven aeroplanes: a change that might affect the aircraft’s take-off performance, including: a change to the maximum take-off mass; a change to the take-off distance; a change to the rate of climb; or a change to VY (best rate of climb speed); a change that increases the aircraft’s drag (e.g. the installation of external cargo pods, external fuel tanks, larger tyres to a fixed undercarriage, floats etc.); a change of engine or propeller type; a change in take-off power including a change in engine speed (tachometer ‘red line’) or, for piston engines, a change to the manifold pressure limitations; a change to the highest power in the normal operating range (‘top of green arc’); in the case of an aircraft where take-off power/engine speed is time limited, a change in the period over which take-off power/engine speed may be applied; a change to the engine inlet or exhaust including, if fitted, the inlet or exhaust muffler; a change in propeller diameter, tip shape, blade thickness or the number of blades; the installation of a variable or adjustable pitch propeller in place of a fixed pitch propeller and vice versa; a change that causes a change to the angle at which air flows into the propeller;

(2)for helicopters: a change that might affect the take-off and/or landing performance, including a change in take-off mass and VY (best rate of climb speed); a change to VNE (never-exceed airspeed) or to VH (airspeed in level flight obtained using the torque corresponding to minimum engine installed, maximum continuous power available for sea level pressure, 25°C ambient conditions at the relevant maximum certified mass); a change to the maximum take-off engine power or maximum continuous power; a change to the gearbox torque limits; a change of engine type; a change to the engine intake or exhaust; a change to the maximum normal operating rpm of the main or tail rotors; a change to the main or tail rotors, including a change in diameter, blade thickness or blade tip profile. Note: The effect on the helicopter’s noise characteristics of either carrying external loads or the installation of external equipment need not be considered.

(ii)Examples of smoke-engine-emissions-related changes that might lead to a major change classification are: a change in engine thrust rating; a change to the aerodynamic flow lines through the engine; a change that affects the engine thermodynamic cycle, specifically relevant engine cycle parameters (e.g. combustor pressure P3, combustor entry temperature T3, air fuel ratio (AFR)); a change to the compressor that might influence the combustor inlet conditions and engine overall pressure ratio; a change to the combustor design (geometry); a change to the cooling of the combustor; a change to the air mass flow through the combustor; a change that affects the fuel spray characteristics.

9.Power plant installation Changes which include:

(i)control system changes which affect the engine/propeller/airframe interface;

(ii)new instrumentation displaying operating limits;

(iii)modifications to the fuel system and tanks (number, size and configuration);

(iv)change of engine/propeller type.

10.Stand-alone changes to non-ALS ICAs that require additional work to demonstrate compliance with the applicable certification basis as follows:

(i)the introduction of novel technology for inspection purposes related to an ALS task;

(ii)changes that adversely affect the certification assumptions: e.g. some specific inspection procedures, such as inspection procedures for use after a hard landing, may include a decision-making chart based on the level of exceedance of the load in comparison with the certified limit loads; such criteria, and adverse changes, should be agreed with EASA.

Classification process

[Figure or form omitted from this preview — available in the Avioverse workspace library.]No No