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21.A.112B Demonstration of capability

Annex I · Regulation (EU) No 748/2012 · EAR revision 27 Nov 2025

IRImplementing rule

21.A.112BDemonstration of capability

(a)An applicant for a supplemental type-certificate shall demonstrate its capability by holding a design organisation approval, issued by the Agency in accordance with Subpart J.

(b)By way of derogation from point (a), as an alternative procedure to demonstrate its capability, an applicant may seek Agency agreement for the use of procedures setting out the specific design practices, resources and sequence of activities necessary to comply with this Subpart.

(c)By way of derogation from point (a), in the case of products referred to in point 21.A.14(c), an applicant may demonstrate its capability by obtaining the Agency's acceptance of its certification programme established in accordance with point 21.A.93(b).

IR · 21.A.112B — Regulation (EU) No 748/2012 · Regulation (EU) 2019/897 · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

GMGuidance material

GM1 21.A.112BDemonstration of capability

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DEMONSTRATION OF CAPABILITY FOR SUPPLEMENTAL TYPE CERTIFICATE (STC) CASES See also AMC 21.A.14(b) for the details of the alternative procedures. The following examples of major changes to type design (ref.: 21.A.91) are classified in two groups. Group 1 contains cases where a design organisation approved under Part 21 Subpart J (‘Subpart J DOA’) should be required, and Group 2 cases where the alternative procedure may be accepted. They are typical examples but each STC case should be addressed on its merits and there would be exceptions in practice. This classification is valid for new STCs, not for evolution of STCs, and may depend upon the nature of the STC (complete design or installation).

ProductDisciplineKind of STCGroup
All aircraft
OSD
Major stand-alone change to any OSD constituent1
Products for which an alternative procedure may be accepted according to 21.A.14(b)All disciplines2
CS-23 (products where a Subpart J DOA is required for TC)
Notes: 1) An STC which leads to a reassessment of the loads on large parts of the primary structure should be in Group 1. 2) ‘2/1’ means that an assessment of consequences in terms of handling qualities, performance or complexity of demonstration of compliance may lead to classification in Group 1.
Aircraft
Conversion to tail wheel configuration1
Auxiliary fuel tank installations2/1
Glass fibre wing tips2/1
Fairings: nacelle, landing gear2
Gap seals: aileron, flap, empennage, doors2
Vortex generators2/1
Spoiler installation1
Increase in MTOW1
Structures
Stretcher installation2
Change to seating configuration2
Windshield replacement (heated, single piece, etc.)2
Lightweight floor panels2
Ski installations2/1
Propulsion
Engine model change1
Fixed pitch propeller installation2
Constant speed propeller installation2/1
Installation of exhaust silencer2
Installation of graphic engine monitor2
Installation of fuel flow meter2
Accessory replacement (alternator, magnetos, etc.)2
Inlet modifications: oil cooler; induction air2
Equipment
Avionics upgrades (EFIS, GPS, etc.)2/1
Engine instrument replacements2
Carburettor ice detection system2
Autopilot system installation1
Wing tip landing light; recognition lights2
WX radar installation2
Aeromedical system installations2
De-icing and anti-icing system installations1
Emergency power supply installations2
CS-25
Cabin Safety
Note: Basically, all changes related to cabin configuration should be in Group 2.Cabin layout (installation of seats (16G), galleys, single class or business / economy class, etc.)2
Floor path marking2
Crew rest compartment1
Change of cargo compartment classification (from class D to class C)1
Structure
Note: An STC which leads to a reassessment of the loads on large parts of the primary structure should be in Group 1.Cargo door1
Change from passenger to freighter configuration1
Avionics
Notes: For CS-25 products, the existence of an ETSO is not taken into account for the classification. The impact on aircraft performance, and influence of aircraft performance are criteria to assess the classification. Subjective assessment of human factors is considered for determination of the classification.CVR2
VHF2
NAV (ADF, VOR, GPS, BRNAV)2
Autopilot, HUD, EFIS, FMS1
DFDR2/1
Meteo radar2
ILS Cat 31
RVSM1
TCAS, EGPWS1
GPWS2
Powerplant
Auxiliary fuel tanks1
Thrust reverser system1
Hushkit1
Fire detection1
Fuel gauging1
Change of engine or propeller1
CS-27 or CS-29All disciplines
Note: 2/1 means that an assessment of consequences in terms of handling qualities and performance may lead to classification in Group 1.Replacement of main rotor or tail rotor blades1
Autopilot1
Engine type change1
GPS installation2
Jettisonable overhead raft installation2
Utility basket installation2/1
Nose or side mount camera installation2/1
Passenger access step installation2/1
Protection net & handle installation (parachuting)2
VIP cabin layout2
Navigation system installation2
Fuel boost pump automatic switch-on installation2
Decrease of maximum seating capacity2
Agricultural spray kit installation2/1
Long exhaust pipe installation2
Flotation gear installation2/1
Wipers installation2
Engine oil filter installation2
Skid gear covering installation2/1
Gutter installation (top pilot door)2
Cable cutter installation2
Auxiliary fuel tank fixed parts installation2
Cabin doors windows replacement2
Radio altimeter aural warning installation2
Standby horizon autonomous power supply2
Fire attack system2/1
Hoisting system installation2/1
External loads hook installation2
Emergency flotation gear installation2/1
Heating/demisting (P2 supply)2

GM · GM1 21.A.112B — Regulation (EU) No 748/2012 · ED Decision 2021/001/R · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

All rules in SECTION A — TECHNICAL REQUIREMENTS

Consolidated from the EASA Easy Access Rules (revision 27 Nov 2025, extracted 17 Aug 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.

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