Explainer
Instructions for Continued Airworthiness (ICA)
The Definition
The Maintenance Half of a Design Approval
Certifying a design proves it is airworthy on the day it is approved. ICA are how it stays that way: the data a mechanic needs to service, inspect, troubleshoot, and repair the product, and the limits that must never be exceeded. They are part of what a design approval obliges its holder to deliver, not an optional extra the sales team adds later.
In the United States the duty is in 14 CFR 21.50(b). The holder of a design approval, including a type certificate or a supplemental type certificate (STC) for an aircraft, engine, or propeller applied for after 28 January 1981, must furnish at least one complete set of ICA to the owner at delivery or at the first standard airworthiness certificate, whichever is later. After that, the instructions and every change to them must be made available to anyone required to comply with them.
What the instructions contain is set by the rule the product is certified under: 23.1529 for normal category airplanes, 25.1529 for transport airplanes, 27.1529 and 29.1529 for rotorcraft, 33.4 for engines, and 35.4 for propellers. Each says the same thing in its own words: prepare ICA in accordance with that part's appendix, acceptable to the FAA. The instructions may be incomplete at type certification, but only if a program exists to complete them before the first delivery or standard airworthiness certificate.
Who Writes Them
Not Only the Airframe Manufacturer
The large manufacturers have publications departments built for this. The obligation reaches much further down. An STC is a design approval, so a company that certifies an avionics installation, an interior, or a cargo conversion owes ICA for that change. Part 21 also defines design approval to include PMA and TSO designs, so parts manufacturers should confirm their own position with their certification office. For how the FAA reviews an STC holder's ICA under Order 8110.54A, including the impact-assessment route and the "ICA incomplete" certificate statement, see ICA for STC holders.
That is where ICA most often go wrong. A small engineering team that has just won an STC rarely has anyone who writes maintenance data for a living, and the instructions get drafted late, by whoever is free, against a deadline set by the first delivery. The result is usually a thin document that answers the certification question and very little of the maintenance one. Writing ICA from engineering data is routine work for an experienced technical publications team, and it is far cheaper to do properly before delivery than to rebuild after operators start asking questions.
For where ICA sit among the other manuals an aircraft carries, see our guide to the types of aircraft manuals, and for why that data is licensed and controlled, our piece on where aircraft manuals come from.
Contents
What Goes in ICA: Appendix H as the Example
Appendix H to Part 25, for transport airplanes, requires the following manuals or sections, as appropriate, prepared in English:
- Airplane maintenance manual or section
- Introduction, a description of the airplane and its systems, how components and systems are controlled and operate, and servicing information: servicing points, fluids, pressures, access panels, lubrication, towing, mooring, jacking, and leveling.
- Maintenance instructions
- Scheduling information with recommended periods and the degree of inspection, an inspection program, troubleshooting, removal and replacement procedures, and general procedures such as ground-run system tests, weighing, lifting and shoring, and storage limitations.
- Access and inspection data
- Diagrams of structural access plates, details for special inspection techniques such as radiographic and ultrasonic testing, and how to apply protective treatments after inspection.
- Fasteners and tools
- All data on structural fasteners (identification, discard recommendations, torque values) and a list of the special tools needed.
- Airworthiness Limitations section
- A segregated, clearly distinguishable section setting out mandatory replacement times, structural inspection intervals and procedures, fuel tank and lightning protection limitations, EWIS replacement times, the limit of validity, and certification maintenance requirements.
- EWIS instructions
- Wiring maintenance and inspection requirements from an enhanced zonal analysis, standard wiring practices, separation requirements, identification methods, and electrical load data.
The Airworthiness Limitations section must carry a prominent statement that reads: “The Airworthiness Limitations section is FAA-approved and specifies maintenance required under §§ 43.16 and 91.403 of the Federal Aviation Regulations, unless an alternative program has been FAA approved.” Appendix H also makes the airplane's ICA include those for each engine, propeller, and required appliance, and requires the applicant to submit a program showing how changes will be distributed. Our explainer on the Airworthiness Limitations section covers what that section must contain and the terms it uses, and the one on the maintenance planning document covers how scheduling information reaches operators of transport aircraft.
In practice the maintenance manual is the core of most ICA: our explainer on the aircraft maintenance manual covers it in depth, and off-wing work usually lands in a component maintenance manual.
Mandatory?
Mandatory for Whom
“Are instructions for continued airworthiness mandatory?” has two answers, depending on who is asking.
For the design approval holder, producing and furnishing them is a regulatory requirement under 21.50(b), and keeping them available and current is a continuing one.
For the people maintaining the aircraft, the Airworthiness Limitations section is mandatory. 14 CFR 43.16 requires an inspection or other maintenance specified there to be performed in accordance with it, and 91.403(c) bars operating an aircraft unless its mandatory replacement times, inspection intervals, and related procedures have been complied with (or approved alternatives under an operations specification or an approved inspection program). For everything else, 43.13(a) requires maintainers to use the methods in the manufacturer's current maintenance manual or ICA, or other methods, techniques, and practices acceptable to the FAA. Part 121 and 135 operators work from their own manual under 43.13(c); see our explainer on operator maintenance manuals under 43.13(c).
Currency matters as much as content: ICA are revised, and the revision a mechanic works from has to be the current one. Our piece on keeping service bulletins and revisions current covers that problem.
Format
No Mandated Format, Several Accepted Ones
The FAA does not prescribe a format. Appendix H asks for a manual or manuals, as appropriate for the quantity of data, in a practical arrangement. EASA's guidance goes further in naming options: applicants may use S1000D (Issue 4 or higher), ATA iSpec 2200, or GAMA Specification No. 2, and ICA may be published as web pages, IT tools, or data modules rather than pages, as long as they are readily accessible and usable by everyone who must comply.
The same guidance sets some practical expectations that are worth meeting whoever your authority is: show each document's applicability and revision status, mark changes at the line (for example with change bars), explain abbreviations, give a metric conversion beside each non-metric value rather than relying on a general table, and put cautions and warnings at the start of each procedure. It also recommends a version in Simplified Technical English.
EASA
The European Equivalent
Under EASA's Part 21 the requirement sits in point 21.A.7. The acceptable means of compliance say the ICA should identify three things: the limitations necessary for continued airworthiness, the means to determine when the product has deteriorated to the point it is no longer airworthy, and the minimum actions required to restore it before then.
Two details are useful to anyone working across both systems. The complete set of ICA is identified in the type certificate data sheet or the STC, directly or through a listing such as a principal manual. And when the ICA reference supplier data, such as a component maintenance manual, that data is incorporated by reference and becomes part of the complete set, so the design approval holder owns the decision to rely on it. For a change or a repair, a statement that there are no changes to the ICA is an accepted answer where it is true.
Checklist
Ten Checks Before You Deliver ICA
Built from Appendix H and EASA's guidance. Other parts' appendices differ in detail, so read the one that applies to your product alongside it.
Name the rule that applies
Find the section your product is certified under (23.1529, 25.1529, 27.1529, 29.1529, 33.4, or 35.4) and work from its appendix, not from a generic template.
Cover everything installed
On a transport airplane the ICA include those for each engine, propeller, and required appliance, plus their interfaces. Where a supplier provides none, your ICA must carry the essential information.
Segregate the Airworthiness Limitations
A distinct section, in the principal manual if there are several documents, carrying the FAA-approved statement Appendix H prescribes.
Write the schedule and the inspection program
Recommended periods, the degree of inspection, wear tolerances, overhaul periods, and cross-references to the limitations section.
Include troubleshooting and removal and replacement
Probable malfunctions, how to recognize them, the remedy, and the order and method of removing and replacing parts, with precautions.
Capture servicing, fasteners, tools, and special techniques
Servicing points and fluids, fastener identification and torque values, special tools, special inspection techniques, and protective treatments.
Identify supplier data you rely on
A component maintenance manual your ICA points to becomes part of the complete set, so list it and own the decision to reference it.
Mark applicability and revision status
Every document should show the models it applies to and its revision, with changes marked at the line, for example by change bars.
Plan how changes are distributed
Appendix H requires a program showing how changes to the ICA, yours and your suppliers', will reach the people using them.
Deliver on time, and keep delivering
A complete set to the owner at delivery or first standard airworthiness certificate, whichever is later, then availability to everyone required to comply, revisions included.
For operators of a few aircraft on the receiving end of all this, our guide to small-fleet technical publications covers how to keep the delivered ICA usable.
FAQ
Questions We Hear
What are instructions for continued airworthiness?
Instructions for Continued Airworthiness (ICA) are the maintenance data a design approval holder must provide so that an aircraft, engine, or propeller can be kept airworthy in service: descriptions, servicing, inspection schedules, troubleshooting, removal and replacement, and an Airworthiness Limitations section. In the United States the requirement sits in 14 CFR 21.50(b), with the content set by each certification part's own rule and appendix.
Who must provide instructions for continued airworthiness?
14 CFR 21.50(b) puts the duty on the holder of a design approval, including a type certificate or supplemental type certificate for an aircraft, engine, or propeller, where application was made after 28 January 1981. That holder furnishes at least one complete set to the owner at delivery or at the first standard airworthiness certificate, whichever is later, and then makes the instructions and their changes available to anyone required to comply. Part 21 defines design approval to include PMA and TSO designs too, so parts manufacturers should confirm their own obligations with their certification office.
Are instructions for continued airworthiness mandatory?
Producing them is mandatory for the design approval holder. For the people maintaining the aircraft, the Airworthiness Limitations section is mandatory: 14 CFR 43.16 requires work it specifies to be done in accordance with it, and 91.403(c) bars operating an aircraft unless its limitations have been complied with (or approved alternatives). For the rest, 43.13(a) requires maintainers to use the methods in the manufacturer's current maintenance manual or ICA, or other methods acceptable to the FAA.
Is there a required format for ICA?
No specific format is mandated. Appendix H to Part 25 requires a manual or manuals in a practical arrangement, in English. EASA's guidance says applicants may use S1000D (Issue 4 or higher), ATA iSpec 2200, or GAMA Specification No. 2, and that ICA can be published as web pages, IT tools, or data modules rather than pages, provided they are readily accessible and usable.
How do EASA's ICA requirements compare with the FAA's?
The structure is similar. EASA's Part 21 places ICA in point 21.A.7, and its guidance says the ICA should identify the limitations necessary for continued airworthiness, the means to tell when a product has deteriorated beyond them, and the minimum actions to restore it. The complete set is identified in the type certificate data sheet or the STC, and supplier data the ICA reference, such as a component maintenance manual, becomes part of that set.
Does a modification need its own ICA?
A supplemental type certificate is a design approval under 21.50(b), so its holder owes ICA for the change. In practice these usually add the modification's own description, servicing, inspections, and removal and replacement to the aircraft's existing manuals. EASA's guidance also allows a change or repair to be accompanied by a statement confirming there are no changes to the ICA, where that is true.
Is it continued airworthiness or continuing airworthiness?
Both appear, and they are not interchangeable. The document is always "Instructions for Continued Airworthiness": the FAA requirement sits in 14 CFR 21.50(b) and EASA's in point 21.A.7. "Continuing airworthiness" is the term EASA's rules use for the ongoing management of an aircraft in service, as in a continuing airworthiness management organization, while FAA regulations use "continued" in titles such as Part 26, Continued Airworthiness and Safety Improvements for Transport Category Airplanes. When you name the deliverable, use "continued."
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Owe ICA for an STC?
We write instructions for continued airworthiness from your engineering data, structure them to the format your customers expect, and keep them current after delivery.