Advisory Circular (AC) No. 500-016 Issue 1 - Appendix A

From: Transport Canada

A.1 General

Appendix A includes the following tables of typical changes that meet the definition of a significant change or substantial change for each product line:

  1. Table 1 - Small Airplanes;
     
  2. Table 2 - Transport Category Aeroplanes;
     
  3. Table 3 - Rotorcraft; and
     
  4. Table 4 - Engines and Propellers.

The Appendix also includes typical changes that do not achieve the significant level.

The examples in the tables were developed from data collected from certification files and included industry review and input. They clearly are changes that we have seen in the past and will likely continue to see in the future. The Minister, or a ministerial delegate, has made the determination, based on applying the criteria, that these changes are significant or not significant.

The columns used in the tables correspond to the following regulations:

Column Corresponding CAR Subsection
Is there a Change to the General Configuration? 511.13(3)(a) and 513.07(3)(a)
Is there a Change to the Principles of Construction? 511.13(3)(a) and 513.07(3)(a)
Have the Assumptions used for Certification been invalidated? 511.13(3)(b) and 513.07(3)(b)
The column "Notes" provides typical rationale considered in evaluating the designation of the criteria.  

The tables can be used in one of two ways:

  1. To classify a proposed change that is listed in the table; or
     
  2. In conjunction with the three criteria, to understand the logic used in the table to help classify a proposed change that is not listed in the table.

The classification may change due to cumulative effects and/or combinations of individual changes.

A.2 Table 1 - Small Airplanes.

A.2.1 The following are examples of substantial changes to small airplanes:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Change in wing location (tandem, forward, canard, high/low). Yes No Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
2 Fixed wing to tilt wing. Yes Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
3 Increase in the number of engines from one to two. Yes Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
4 Replacement of piston or turbo-prop engines with turbojet or turbofan engines. Yes Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
5 Change in engine configuration (tractor to pusher). Yes Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
6 Change from an all metal airplane to all composite primary structure (fuselage, wing, empennage). No Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
7 Increase from subsonic to supersonic flight regime. Yes No Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
A.2.2 The following are examples of significant changes to small airplanes:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Conventional tail to T-tail or Y-tail, or vice versa. Yes No Yes Change in general configuration. Requires extensive structural, flying qualities and performance re-investigation.

Requires new AFM to address performance and flight characteristics.
2 Changes in wing configuration (addition of tail strakes or change in dihedral, or changes in wing span, flap or aileron span, angle of incidence of the tail, addition of winglets, or wing sweep of more than 10%. Yes No Yes Change in general configuration. Likely requires extensive changes to wing structure.

Requires new AFM to address performance and flight characteristics. Note: Small changes to wingtip are not significant changes. See table for not significant changes.
3 Tricycle / tail wheel undercarriage change or addition of floats. Yes No No Change in general configuration. Likely, at airplane level, general configuration and certification assumptions remain valid.
4 Increase in seating capacity resulting in a different certification category (e.g., from normal to commuter category where configuration or principles of construction changes or assumptions do not remain valid. Yes Yes Yes Change in general configuration. Change in principles of construction. Requires extensive construction re-assessment. Change in certification assumptions.

Requires new AFM and pilot type rating.
5 Passenger to freighter configuration conversion which involves the introduction of a cargo door or an increase in floor loading of more than 20%, or provision for carriage of passengers and freight together. Yes No Yes Change in general configuration affecting load paths, aero elastic characteristics, aircraft related systems, etc. Change in design assumptions.
6 A fuselage stretch would be considered significant if it would invalidate the existing substantiation, or would change the primary structure, aerodynamics, or operating envelope sufficiently to invalidate the assumptions of certification. Yes No Yes Likely extensive changes to fuselage structure, aerodynamics, aircraft systems performance, and operating envelope.

Requires new AFM to address performance and flight characteristics.
7 Replace reciprocating engines with the same number of turbo-propeller engines where the operating envelope is expanded. No No Yes Invalidates certification assumptions.

Requires new AFM to address performance and flight characteristics.
8 Addition of a turbo-charger that changes the power envelope, operating range, or limitations appreciably. No No Yes Invalidates certification assumptions due to changes in operating envelope and limitations.

Requires new AFM to address performance and flight characteristics.
9 The replacement of an engine of higher rated power or increase thrust would be considered significant if it would invalidate the existing substantiation, or would change the primary structure, aerodynamics, or operating envelope sufficiently to invalidate the assumptions of certification. No Yes Yes Invalidates certification assumptions.

Requires new AFM to address performance and flight characteristics. Likely changes to primary structure. Requires extensive construction
re-investigation.
10 A change in the type of material, such as composites in place of metal (or one composite fibre material system with another (e.g., carbon for fibreglass), for primary structure would normally be assessed as a significant change. No Yes Yes Change in principles of construction and design from conventional practices. Likely change in design/certification assumptions.
11 Change involving appreciable increase in design speeds Vd, Vmo, Vc, or Va. No No Yes Certification assumptions invalidated. Requires new AFM to address performance and flight characteristics.
12 STOL kit. No No Yes Certification assumptions invalidated. Requires new AFM to address performance and flight characteristics.
13 A change in the rated power or thrust is likely to be regarded as significant if the design speeds are thereby changed so that compliance needs to be re-justified with a majority of requirements. No No Yes Certification assumptions invalidated. Requires new AFM to address performance and flight characteristics.
14 Fuel state: such as compressed gaseous fuels, or fuel cells. This could completely alter the fuel storage and handling systems and possibly affect the aeroplane structure. No No Yes Changes in design/certification assumptions. Extensive alteration of fuel storage and handling systems.
15 A design change that alters the aircraft flight characteristics or performance from the type design would normally be significant if it appreciably changes the kinematics or dynamics of the aeroplane. No No Yes Certification assumptions invalidated. Requires new AFM to address performance and flight characteristics.
16 Weight increase which places the aircraft into the commuter category
(i.e., above
12500 lbs.)		 No No Yes Certification assumptions invalidated. Requires new AFM.
17 A change in the flight control concept for an aircraft, for example to fly by wire (FBW) and side-stick control, or a change from hydraulic to electronically actuated flight controls, would in isolation normally be regarded as a significant change. No No Yes Changes in design and certification assumptions. Requires extensive systems architecture and integration
re-investigation.
Requires new AFM.
18 Addition of cabin pressurization. No Yes Yes Extensive airframe changes affecting load paths, fatigue evaluation, aero elastic characteristics, etc. Requires extensive construction
re-investigation. Invalidates design assumptions.
19 Changes in types and number of emergency exits or an increase in passenger capacity in excess of maximum passenger capacity demonstrated for the aircraft type. No No Yes Emergency egress requirements exceed those previously substantiated. Invalidates assumptions of certification.
20 A change in the required number of flight crew, which necessitates a complete cockpit re-arrangement, and/or an increase in pilot workload would be a significant change. No No Yes Extensive changes to avionics and aircraft systems. Invalidates certification assumptions. Requires new AFM.
21 An appreciable expansion of an aircraft's operating envelope or operating capability would normally be a significant change. E.g., an increase in maximum altitude limitation, approval for flight in known icing conditions, an increase in airspeed limitations. No No Yes Invalidates certification assumptions. Requires new AFM to address performance and flight characteristics.
22 A major flight deck upgrade. No No Yes Extensive changes to avionics and electrical systems design. Invalidates certification assumptions. Extensive re-assessments of systems integration, flight crew workload, and human factors evaluation are required. Requires new AFM.
23 Introduction of autoland. No No Yes Invalidates original design assumptions.
A.2.3 The following are examples of not significant changes to small airplanes:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Addition of wingtip modifications
(not winglets).		 No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
2 Installation of skis or wheel skis. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
3 Forward Looking Infra-red Radar or surveillance camera installation. No No No Additional flight or structural evaluation may be necessary but the change does not alter basic airplane certification.
4 Litter, berth and cargo tie down device installation. No No No Not an airplane level change.
5 Increased tire size, including tundra tires. No No No Not an airplane level change.
6 Replacement of one propeller type with another (irrespective of increase in number of blades). No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
7 Addition of a turbo-charger that does not appreciably change the power envelope, operating range, or limitations (e.g., a turbo-normalized engine), (e.g., where the additional power is used to enhance high altitude or hot day performance.) No No No Not an airplane level change.
8 Replace a petrol engine with a diesel engine of approximately the same horsepower. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
9 Substitution of one method of bonding for another (e.g., change in type of adhesive). No No No Not an airplane level change.
10 Substitution of one type of metal for another. No No No Not an airplane level change.
11 Any change in construction or fastening not involving primary structure. No No No Not an airplane level change.
12 A new fabric type for fabric skinned aircraft. No No No Not an airplane level change.
13 Increase in flap speed or undercarriage limit speed. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
14 Structural strength increases. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
15 IFR upgrades involving installation of components (where the original certification does not indicate that the aeroplane is not suitable as an IFR platform, e.g., special handling concerns). No No No Not an airplane level change.
16 Fuel lines, where engine horsepower is increased but fuel flow is not increased beyond the certified maximum amount. No No No Not an airplane level change.
17 Fuel tanks, where fuel is changed from gasoline to diesel fuel and tank support loads are small enough that an extrapolation from the previous analysis would be valid. Chemical compatibility would have to be substantiated. No No No Not an airplane level change.
18 Limited changes in a pressurization system, e.g., number of outflow valves, type of controller, or size of pressurized compartment, but the system must be
re-substantiated if the original test data is invalidated.		 No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
19 Install a quieter exhaust system. No No No Not an airplane level change.
20 Changes in engine cooling or cowling. No No No Not an airplane level change.
21 Fuel type: AvGas to Diesel/Jet A, AvGas to Ethanol/Methanol. Changing to Multiple fuel systems containing fuel types (other than systems used for starting): such systems using as AvGas/Ethanol, or Jet A/Autogas (turbine). Unrestricted mixtures in one fuel system of different fuel types: Such as AvGas/Diesel or Jet A/Ethanol. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
22 Fuels of substantially the same type: Such as AvGas to AutoGas, AvGas (80/87) to AvGas (100LL), Ethanol to Isopropyl Alcohol, Jet B to Jet A (although Jet A to Jet B may be considered significant due to the fact that Jet B is considered potentially more explosive). No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
23 Fuels that specify different levels of "conventional" fuel additives that do not change the primary fuel type. Different additive levels (controlled) of MTBE, ETBE, Ethanol, Amines, etc. in AvGas would not be considered a significant change. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
24 A change to the maximum take-off weight of less than 5% unless assumptions made in justification of the design are thereby invalidated. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
25 An additional aileron tab (e.g. on the other wing). No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
26 Larger diameter flight control cables with no change in routing, or other system design. No No No Not an airplane level change.
27 Autopilot installation (for IFR use, where the original certification does not indicate that the aeroplane is not suitable as an IFR platform). No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid.
28 Increased battery capacity or relocate battery. No No No Not an airplane level change.
29 Replace generator with alternator. No No No Not an airplane level change.
30 Additional lighting (e.g., navigation lights, strobes). No No No Not an airplane level change.
31 Higher capacity brake assemblies. No No No Not an airplane level change.
32 Increase in fuel tank capacity. No No No Not an airplane level change.
33 Addition of an oxygen system. No No No Not an airplane level change.
34 Relocation of a galley. No No No Not an airplane level change.
35 Passenger to freight (only) conversion with no change to basic fuselage structure. No No No Although a major change to the airplane, likely the original general configuration, principles of construction and certification assumptions remain valid. Requires certification substantiation applicable to freighter requirements.
36 Installation of new seat belt or shoulder harness. No No No Not an airplane level change.
37 A small increase in cg range. No No No At airplane level, no change in general configuration, principles of construction & certification assumptions.
38 APU Installation that is not flight essential. No No No A major change to the airplane level, likely the original general configuration, principles of construction and certification assumptions remain valid. Requires certification substantiation applicable to APU installation requirements.
39 An alternative autopilot. No No No Not an airplane level change.
40 Addition of Class B Terrain Awareness and Warning Systems (TAWS). No No No Not an airplane level change.

A.3 Table 2 - Transport Category Aeroplanes.

A.3.1 The following are examples of substantial changes to transport category aeroplanes:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Change in the number or location of engines, e.g. four to two wing-mounted engines or two wing-mounted to two body-mounted engines. Yes No Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable requirements is required.
2 Change from a high wing to low wing configuration. Yes No Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable requirements is required.
3 Change from an all metal airplane to all composite primary structure (fuselage, wing, empennage). Yes Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable requirements is required.
A.3.2 The following are examples of significant changes to transport category aeroplanes:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Derivative model e.g. increased passenger payload, freighter version or complete update of a certified aeroplane. Yes Yes Yes Multiple changes packaged into a new model. Increase payload or new freighter would change the general configuration and assumptions. Updated aeroplane could change the principles of construction.
2 Reduction in the number of flight crew (In conjunction with flight deck update). Yes No No Extensive changes to avionics and aircraft systems. Impact to crew workload and human factors, pilot type rating.
3 Modify an aeroplane for flight in known icing conditions by adding systems for ice detection and elimination. Yes No Yes New aircraft operating envelope. Requires major new systems installation and aircraft evaluation. Operating envelope changed.
4 Conversion - passenger or combi to all freighter including cargo door, redesign floor structure and 9g net or rigid barrier. Yes No Yes Extensive airframe changes affecting load paths, aero elastic characteristics, and aircraft related systems for fire protection, etc. Design assumptions changed from passenger to freighter.
5 Change to pressurized cabin including the introduction of a pressurization system. No No Yes Essentially a
re-certification of airframe and systems associated with operating envelope change.
6 Addition of leading edge slats. Yes No No Requires extensive changes to wing structure, adds aircraft level systems, and requires a new aeroplane flight manual to address performance and flight characteristics.
7 Fuselage length change - lengthen or shorten fuselage. Yes No No Requires extensive changes to fuselage structure, affects aircraft level systems, and requires a new aeroplane flight manual to address performance and flight characteristics.
8 Extensive structural airframe modification, such as installation of a large telescope with large opening in fuselage. Yes No No Requires extensive changes to fuselage structure, affects aircraft level systems, and requires a new aeroplane flight manual to address performance and flight characteristics.
9 Changing the number of axles or number of landing gear done in context with a product level change that involves changing the aeroplane gross weight. Yes No No Requires extensive changes to aircraft structure, affects aircraft systems and requires AFM changes.
10 Primary structure changes from metallic material to composite material. No Yes No Change in principles of construction and design from conventional practices.
11 Typically, an increase in design weight of more than 10%. No No Yes When it requires extensive
re-substantiation of aircraft structure, aircraft performance and flying qualities and associated systems.
12 Wing changes in span, sweep, and tip designs or wing chord.
(Note: Potentially substantial if it is a change from a high wing to a low wing, or a new wing.)		 Yes No No When it requires extensive changes to wing structure, adds aircraft level systems, and requires a new aeroplane flight manual to address performance and flight characteristics.
13 Change in type or number of emergency exits in conjunction with an increase in the number of passengers demonstrated. No No Yes The new emergency egress requirements exceed those previously substantiated.
14 Comprehensive flight deck upgrade. No No Yes Affects avionics and electrical systems integration and architecture concepts and philosophies. This drives a
re-assessment of flight crew workload and other human factors issues, and requires a re-evaluation of the original design assumptions used for the cockpit.
15 Change in primary flight controls to fly by wire (FBW) system. (Some airplanes have some degree of FBW. Achieving full FBW may be a not significant change on some airplanes.) Yes No Yes When the degree of change is so extensive that it affects basic aircraft systems integration and architecture concepts and philosophies. This drives a complete re-assessment of flight crew workload, handling qualities, and performance evaluation, which are different from the original design assumptions.
16 Replace reciprocating with turbo-propeller engines. Yes No No Requires extensive changes to airframe structure, adds aircraft level systems, and requires a new aeroplane flight manual to address performance and flight characteristics.
17 Typically a thrust increase of more than 10%. No No Yes When it requires extensive
re-substantiation of powerplant installation, and has a marked effect on aircraft performance and flying qualities.
18 Initial installation of an autoland system. No No Yes Baseline airplane not designed for autoland operation, potential crew work load and systems compatibility issues
19 Installation of a new fuel tank, e.g. horizontal stabilizer tank or auxiliary fuel tank in the fuselage outside the wing in conjunction with increased maximum takeoff weight and takeoff thrust. No No Yes Requires changes to airframe, systems and AFM. Results in performance changes.
20 Main deck cargo door installation. Yes No No Redistribution of internal loads, change in aero elastic characteristics, system changes.
21 Conversion from a passenger floor to a cargo floor and installation of a cargo handling system. No No Yes Completely new floor loading and design. Redistribution of internal loads, change in cabin safety requirements, system changes.
22 Initial installation of an APU essential for aircraft flight operation. No No Yes Changes emergency electrical power requirements, change in flight manual and operating characteristics.
A.3.3 The following are examples of not significant changes to transport category aeroplanes:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Alternate engine installation or hush kit at same position. No No No Although an aeroplane level change, it is not significant so long as there is not more than a 10% increase in thrust or a change in the principles of propulsion.
2 Fuselage length change - lengthen or shorten fuselage. No No No A small change in fuselage length due to re-fairing the aft body or radome for cruise performance reasons, where such changes do not require extensive structural, systems or AFM changes.
3 Re-fairing of wing tip caps (e.g. for lights, fuel dump pipes) and addition of splitter plates to the trailing edge thickness of the cruise airfoil. No No No Does not require extensive structural, AFM, or systems changes.
4 Additional power used to enhance high altitude or hot day performance. No No No Usually no change in basic operating envelope. Existing certification data can be extrapolated. Could be significant product change if the additional power is provided by installation of a rocket motor or additional, on demand engine due to changes in certification assumptions.
5 General avionics changes. No No No These modifications are generally adaptive* in nature, and do not change the original certification assumptions, alter basic cockpit design architecture concepts and philosophies, and do not have a major impact on crew workload or man/machine. *Adaptive means the change adapts to the existing airplane buses, power, structure, .
6 Initial installation of an autopilot system. No No No Modification is generally adaptive in nature, with no change to original certification assumptions.
7 Integrated modular avionics. No No No The basic functionality of the systems is unchanged. No change from analog to digital.
8 Installation or rearrangement of an interior in an aircraft. No No No Special conditions could be used for new and novel features.
9 Change from assembled primary structure to monolithic or integrally machined structure. No No No Method of construction is well understood.
10 Modification to ice protection systems. No No No Re-certification required, but certification basis is adequate.
11 Brakes: design or material change, e.g. steel to carbon. No No No Re-certification required, but certification basis is adequate.
12 Redesign floor structure. No No No By itself, this is not a significant product level change. It could be a significant change if part of a cargo converted passenger airplane.
13 Novel or unusual method of construction of a component. No No No Special conditions could be required if there are no existing standards that adequately address these features. The component change does not rise to the product level change.
14 Initial installation of a non-essential APU. No No No A stand-alone initial APU installation on an airplane originally designed to use ground/airport supplied electricity, and air-conditioning. In this case, the APU would be an option to be independent of airport power.

A.4 Table 3 - Rotorcraft.

A.4.1 The following are examples of substantial changes to rotorcraft:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Change from the number and or configuration of rotors (e.g. main & tail rotor system to two main rotors. Yes No Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
2 Change from an all- metal rotorcraft to all composite rotorcraft. Yes Yes Yes Proposed change in design is so extensive that a substantially complete investigation of compliance with the applicable standards is required.
A.4.2 The following are examples of significant changes to rotorcraft:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Comprehensive Flight Deck Upgrade. Yes No Yes The degree of change is so extensive that it affects basic avionics and electrical systems integration and architecture concepts and philosophies. This drives a complete reassessment of flight crew workload and other human factor issues, and requires a re-evaluation of the original design assumptions used for the cockpit.
2 Certification for flight into known icing conditions. No No Yes  
3 (Fixed) flying controls from mechanical to fly by wire. Yes Yes Yes  
4 Addition of an engine; e.g. from single to twin or reduction of the number of engines; e.g. from twin to single. Yes No Yes May be Substantial -depend upon project details.
5 A fuselage modification that changes the primary structure, aerodynamics, or operating envelope sufficiently to invalidate the certification assumptions. Yes No Yes  
6 Application of an approved primary structure to a different approved model (e.g. installation on a former model of the main rotor approved on a new model that results in increase performance. No Yes Yes  
7 Extensive Primary structure changes from metallic material to composite material. No Yes Yes Change in principles of construction and assumptions used for certification for the product level change. Changes of a few individual elements from metal to composite are not typically considered a significant change.
8 Emergency Medical Service (EMS) Configuration with primary structural changes sufficiently to invalidate the certification assumptions. Yes No Yes Any EMS configuration will not be classified as significant. Modifications made for EMS is typically internal and the general external configuration is normally not affected. These changes should not automatically be classified as significant.
9 Skid landing gear to wheel landing gear or wheel landing to skid. Yes No Yes If the rotorcraft is such that the skid or wheel configuration is inherent in the basic certification design, the change may be not significant.
10 Change of the number of rotor blades. Yes No No The addition/deletion of rotor blades may not be significant provided the remainder of the basic propulsion system remains essentially unchanged.
11 Change tail anti-torque device (e.g. tail rotor, ducted fan or other technology). Yes Yes No  
A.4.3 The following are examples of not significant changes to rotorcraft:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Emergency floats. No No No Must Comply with the specific applicable requirements for emergency floats. This installation, in itself, does not change the rotorcraft configuration, overall performance, or operational capability. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.
2 Forward Looking Infrared or surveillance camera installation. No No No Additional flight or structural evaluation may be necessary but the change does not alter the basic rotorcraft certification.
3 Helicopter Terrain Awareness Warning System (HTAWS) for operational credit. No No No Certified per rotorcraft HTAWS AC guidance material.
4 Health Usage Monitoring System (HUMS) for Maintenance Credit. No No No Certified per rotorcraft HUMS AC guidance material.
5 Expanded limitations with minimal or no design changes, following further tests/justifications or different mix of limitations (CG limits, oil temperatures, altitude, minimum/
maximum weight, minimum/
maximum external temperatures, speed, ratings structure).		 No No No Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.
6 Installation of a new engine type, equivalent to the former one; leaving a/c installation and limitations substantially unchanged. No No No Refer to AC 27-1 or AC 29-2 for guidance
7 Windscreen installation. No No No Does not change the rotorcraft overall product configuration.
8 Installation of Snow skis, "Bear Paws". No No No Must comply with specific requirements associated with the change. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.
9 External Cargo Hoist. No No No Must Comply with the specific applicable requirements for external loads. This installation, in itself, does not change the rotorcraft configuration, overall performance, or operational capability. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type certificated product level.
10 IFR upgrades involving installation of components (where the original certification does not indicate that the rotorcraft is not suitable as an IFR platform, e.g., special handling concerns). No No No Not a rotorcraft level change.
11 An upgrade to CAT A certification approval. No No No Typically, these are engine and drive systems rating changes appropriate for CAT A and rotorcraft performance requirements. Rotorcraft modifications, if any necessary, do not typically invalidate the certification assumptions, or change the general configuration of principles of construction.
12 Reducing the number of pilots for IFR from 2 to 1. No No No May be significant if there are extensive equipment and design changes such that the certification assumptions are invalidated or the general configuration of the rotorcraft is changed.

A.5 Table 4 - Engines and Propellers.

A.5.1 The following are examples of significant changes for turbine engines:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Traditional turbofan to geared-fan engine. Yes No Yes This change would affect the engine in terms of FOD ingestion, containment, etc.Note that this change is most likely substantial under 21.19.
2 Low bypass ratio engine to high bypass ratio engine with an increased inlet area. Yes No Yes Change in general configuration. Likely change in model designation. Not interchangeable. Assumptions for certification may no longer be valid in terms of ingestion, icing, etc.

Note that this change is most likely substantial under 21.19.
3 Turbojet to Turbofan. Yes No Yes Change in general configuration. Likely change in model designation. Not interchangeable Assumptions for certification may no longer be valid ingestion, icing, blade out criteria, etc.

Note that this change is most likely substantial under 21.19.
4 Turbo-shaft to turbo-propeller. Yes No Yes Change in configuration such as an additional gearbox. Change in model designation. Change in mission profile. Assumptions for certification may no longer be valid in terms of flight envelope, ratings, etc.

Note that this change is most likely substantial under 21.19.
5 Conventional ducted fan to unducted fan. Yes Yes Yes Change in configuration. Change in Type. Not interchangeable. Assumptions for certification may no longer be valid. Note that this change is most likely substantial under 21.19.
6 Conventional engine for subsonic operation to after-burning engine for supersonic operation. Yes Yes Yes Change in configuration. Change in Type. Not interchangeable. Assumptions for certification may no longer be valid. Change in operating envelope. Note that this change is most likely substantial under 21.19.
7 Increase/decrease in the number of compressor/turbine stages with resultant change in approved limitations*. (* Excludes life limits) No No Yes Change is associated with other changes that would affect performance envelope and may affect the dynamic behaviour in terms of backbone bending, torque spike effects on casing, surge and stall characteristics, etc.
8 New design fan blade and fan hub, or a bladed fan disk to a blisk or a fan diameter change that could not be retrofitted. Yes No Yes Likely change in model designation Change is associated with other changes that would affect engine thrust/power limitations and have affected the dynamic behaviour of the engine in terms of backbone bending, torque spike effects on casing, foreign object ingestion behaviour, burst model protection for the aircraft. If there is a diameter change, installation will be also affected.
9 Hydro-Mechanical to FADEC/EEC without hydro-mechanical backup. Yes Yes Yes Change in engine control configuration. Likely change in model designation. Not interchangeable. Likely fundamental change to engine operation. Assumptions used for certification are no longer valid or were not addressed in the original certification, i.e. HIRF and Lightning Protection, Fault Tolerance, Software Certification and other aspects associated with FADEC/EEC systems.
10 A change in the containment case from hard-wall to composite or vice-versa, that could not be retrofitted without additional major changes to the engine or restrictions in the initial limitations in the installation manual. No Yes No Change in methods of construction that have affected inherent strength, backbone bending, blade to case clearance retention, containment wave effect on installation, effect on burst model, torque spike effects.
11 Replacement of the gas generator (core) with a different one that is associated with changes in approved limitations*. (* Excludes life limits) No No Yes Change is associated with other changes that would affect performance envelope and may affect the dynamic behaviour of the engine. Assumptions used for certification may no longer be valid.
A.5.2 The following are examples of significant changes for piston engines:
 
1 Convert from Mechanical to Electronic Control System. Yes Yes No Change in engine control configuration: Installation interface of engine changed. Changes to principles of construction. Digital controllers and sensors require new construction techniques and environmental testing.
2 Add Turbocharger that increases performance and changes in overall product. Yes No Yes Change in general configuration. Installation interface of engine changed (exhaust system). Certification assumptions invalidated. Change in engine configuration. Change in operating envelope and performance.
3 Convert from air-cooled cylinders to liquid cooled cylinders. Yes No Yes Change in general configuration. Installation interface of engine changed (cooling lines from radiator, change to cooling baffles). Certification assumptions invalidated. Change in operating envelope and engine temperature requirements.
4 Convert from spark-ignition to compression-ignition. Yes No Yes Change in general configuration. Installation interface of engine changed (no mixture lever). Certification assumptions invalidated. Change in operating envelope and performance.
A.5.3 The following is an example of a significant change for propellers:
 
1 Introduction of a different principle of blade retention. Yes Yes No Change in propeller configuration. Likely change in model designation. Propeller's operating characteristics and inherent strength require re-evaluation.
A.5.4 The following are examples of not significant changes for turbine engines:
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Change in the material from one type of metal to another type of metal of a compressor drum. No No No No change in performance. No likely change in model designation. Assumptions are still valid.
2 Increase/decrease in the number of compressor/
turbine stages without resultant change in performance envelope.		 No No No No change in performance. Model designation may or may not change. Assumptions are still valid.
3 New components internal to the FADEC/EEC the introduction of which does not change the function of the system. No No No No change in configuration.

Retrofitable.

Assumptions used for certification are still valid. Possible changes in principles of construction are insignificant.
4 Software changes. No No No  
5 Rub-strip design changes. No No No Component Level Change.
6 A new combustor that does not change the approved limitations*, or dynamic behaviour. (* Excludes life limits) No No No Component Level Change.
7 Bearing changes. No No No Component Level Change.
8 New blade designs with similar material that can be retrofitted. No No No Component Level Change.
9 Fan blade re-design that can be retrofitted. No No No Component Level Change.
10 Oil tank re-design. No No No Component Level Change.
11 Change from one hydro-mechanical control to another hydro-mechanical control. No No No Component Level Change.
12 Change to limits on life limited components. No No No Component Level Change.
13 Changes to limits on exhaust gas temperature. No No No  
14 Changes in certification maintenance requirements (CMR) with no configuration changes. No No No  
15 Bump ratings within the product's physical capabilities that may be enhanced with gas path changes that are limited to such changes as blade re-stagger, cooling hole patterns, blade coating changes, etc. No No No  
16 A change in principal physical properties and mechanics of load transfer of a material of primary structure or highly loaded components. For example, change from traditional metal to either an exotic alloy or a composite material on a highly loaded component. No No No Component Level Change.
A.5.5 The following are examples of not significant changes for piston engines
 
1 A change in principal physical properties and mechanics of load transfer of a material of primary structure or highly loaded components. For example, change from traditional metal to either an exotic alloy or a composite material on a highly loaded component. No No No Component Level Change.
2 New or redesigned cylinder head, or valves or pistons. No No No Component Level Change.
3 Changes in crankshaft. No No No Component Level Change.
4 Changes in crankcase. No No No Component Level Change.
5 Changes in carburetor. No No No Component Level Change.
6 Changes in mechanical fuel injection system. No No No  
7 Changes in mechanical fuel injection pump. No No No Component Level Change
8 Engine model change to accommodate new airplane installation. No change in principles of operation of major subsystems; no significant expansion in power or operating envelopes or in limitations. No No No  
9 No change in basic principles of operation, or a simple mechanical change. For example, change from dual magneto to two single magnetos on a model. No No No  
10 Subsystem change produces no change in base input parameters, and previous analysis can be reliably extended. For example, a change in turbocharger where induction system inlet conditions remain unchanged, or if changed, the effects can be reliably extrapolated. No No No  
11 Change in material of secondary structure or not highly loaded component. For example, a change from metal to composite material in a non-highly loaded component, such as an oil pan that is not used as a mount pad. No No No Component Level Change.
12 Change in material that retains the physical properties and mechanics of load transfer. For example, a change in trace elements in a metal casting for ease of pouring or to update to a newer or more readily available alloy with similar mechanical properties. No No No Component Level Change.
A.5.6 The following are examples of not significant changes for propellers
Item Description of change Is there a Change to the General Configuration? Is there a Change to the Principles of Construction? Have the assumptions used for Certification been invalidated? Notes
1 Change in the material of a blade bearing. No No No Component Level Change.
2 Change to a component in the control system. No No No Component Level Change.
3 Change to a de-icer boot. No No No Component Level Change.

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