Appendix A A-9 The following examples are for SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes A change in the required number of flight crew, which necessitates a complete cockpit rearrangement, 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 a new aircraft flight manual (AFM).
Expansion of an aircraft’s operating envelope.
No No Yes An appreciable expansion of operating capability would normally be a significant change (e.g., an increase in maximum altitude limitation, approval for flight in known icing conditions, or an increase in airspeed limitations). Merely operating a product to an expanded envelope for which it was originally designed is generally not a significant change. In this case, the assumptions used for certification of the basic product remain valid and the results can be applied to cover the changed product with predictable effects or can be demonstrated without significant.
Appendix A A-10 The following examples are for SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Replacement of an aviation gasoline engine with an engine of approximately the same horsepower utilizing diesel fuel.
No No Yes A major change to the airplane. The general configuration and principles of constructions will usually remain valid;
however, the assumptions for certification are invalidated.
Comprehensive flight deck upgrade, such as conversion from entirely federated, independent electromechanical flight instruments to highly integrated and combined electronic display systems with extensive use of software and/or complex electronic hardware.
No No Yes Affects avionics and electrical systems integration and architecture concepts and philosophies.
Introduction of autoland
No No Yes Invalidates original design assumptions
Appendix A A-11 The following examples are for SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Airframe life extension No No Yes This modification pertains to fuselage and/or wing limits, and aging airplane concerns.
An increase from the original life limit which constitutes a reevaluation of certification design assumptions.
Extensive structural airframe modification, such as a large opening in fuselage Yes No No Requires extensive changes to fuselage structure, affects aircraft systems, and requires a new airplane flight manual to address performance and flight characteristics.
Appendix A A-12 The following examples are for SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Fuselage stretch or shortening in the cabin or pressure vessel Yes No Yes Cabin interior changes are related changes since occupant safety considerations are impacted by a cabin length change. Even if a new cabin interior is not included in the product level change, the functional effect of the fuselage plug has implications on occupant safety (e.g., the dynamic environment in an emergency landing, emergency evacuation, etc.), and thus the existing cabin interior becomes an affected area.
Conversion from normal category to commuter category airplane
Yes No Yes In many cases this change could be considered to be a substantial change to the type design. Therefore, a proposed change of this nature would be subject to an FAA determination under 14 CFR § 21.19.
Appendix A A-13
The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Addition of wingtip modifications (not winglets) No No No A major change to the airplane. Likely the original general configuration, principles of construction, and certification assumptions remain valid.
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.
FLIR or surveillance camera installation No No No Additional flight or structural evaluation may be necessary, but the change does not alter basic airplane certification.
Litter, berth and cargo tie down device installation No No No Increased tire size, including tundra tires No No No 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.
Appendix A A-14 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Addition of a turbocharger that does not change the power envelope, operating range, or limitations
(e.g., a turbonormalized engine, where the additional power is used to enhance high altitude or hot day performance) No No No Substitution of one method of bonding for another (e.g., change in type of adhesive) No No No Substitution of one type of metal for another No No No Any change in construction or fastening not involving primary structure No No No A new fabric type for fabric skinned aircraft No No No
Appendix A A-15 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes 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.
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.
Instrument flight rules (IFR) upgrades involving installation of components (where the original certification does not indicate that the airplane is not suitable as an IFR platform, e.g., special handling concerns) No No No
Appendix A A-16 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Fuel lines, where engine horsepower is increased but fuel flow is not increased beyond the certificated maximum amount No No No 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 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 resubstantiated if the original test data are invalidated.
No No No Although a major change to the airplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.
Appendix A A-17 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Install a quieter exhaust system No No No Changes in engine cooling or cowling No No No Changing 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.
Fuels that specify different levels of “conventional” fuel additives that do not change the primary fuel type. Different additives (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.
Appendix A A-18 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes A change to the maximum take-off weight of less than 5 percent 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. (Unless this weight increase would result in a shift to commuter category.)
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.
Larger diameter flight control cables with no change in routing, or other system design No No No Autopilot installation (for instrument flight rules (IFR) use, unless the original certification indicates that the airplane 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.
Increased battery capacity or relocate battery No No No
Appendix A A-19 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Replace generator with alternator No No No Additional lighting
(e.g., navigation lights, strobes) No No No Higher capacity brake assemblies No No No Increase in fuel tank capacity No No No Not a product level change, unless it is tied with an increase in gross weight.
Addition of an oxygen system No No No Relocation of a galley No No No 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.
New cabin interior with no fuselage length change No No No
Appendix A A-20 The following examples are for NOT SIGNIFICANT changes for Small Airplanes (Part 23):
Description of change Is there a change to the general configuration?
14 CFR §
21.101(b)(1)(i) Is there a change to the principles of construction?
14 CFR §
21.101(b)(1)(i) Have the assumptions used for certification been invalidated?
14 CFR §
21.101(b)(1)(ii) Notes Installation of new seat belt or shoulder harness No No No A small increase in
c.g. range No No No At a product level, no change in general configuration, principles of construction, and certification assumptions.
APU installation that is not flight essential No No No Although a major change to the airplane level, likely the original general configuration, principles of construction, and certification assumptions remain valid.
An alternative autopilot No No No Addition of Class B terrain awareness and warning systems (TAWS) No No No