4.2 Type Certificate Data Sheets & Aircraft Specifications
Key Takeaways
- A Type Certificate Data Sheet (TCDS) issued under 14 CFR Part 21 is an official part of the Type Certificate defining the approved design configuration, operating limitations, and required equipment.
- Type Certificate Data Sheets originated in January 1958 and are part of the type certificate under 14 CFR 21.41, whereas the older Aircraft Specifications are FAA recordkeeping documents that are not part of a type certificate; both remain in effect and are used the same way to establish conformity.
- The TCDS establishes non-negotiable operational boundaries including approved engine and propeller combinations, power limits, airspeed limitations, center of gravity envelopes, and empty weight CG (EWCG) ranges.
- Control surface deflection angles and tolerances specified in the TCDS are flight safety limitations; measuring control surface travels with an inclinometer or protractor is a mandatory conformity check during an inspection.
- An Inspection Authorization holder must systematically audit physical hardware, installed accessories, and mandatory placards against TCDS specifications and serial number blocks to detect unapproved modifications.
4.2 Type Certificate Data Sheets & Aircraft Specifications
[!NOTE] The Bedrock of Type Design: A Type Certificate Data Sheet (TCDS) is a formal, legally binding component of an aircraft's Type Certificate under 14 CFR Part 21. It defines the approved engineering boundaries, equipment, operating limitations, and configuration standards to which each certificated aircraft must conform. For an Inspection Authorization (IA) holder, the TCDS is the primary standard for verifying Condition 1 of airworthiness: conformity to type design.
Origin, Legal Standing & Aircraft Specifications vs. TCDS
Under 14 CFR § 21.41, each Type Certificate issued by the FAA includes the type design, operating limitations, certificate data sheet, applicable regulations, and any other conditions prescribed by the Administrator. When an aircraft receives its standard airworthiness certificate, it is certified as conforming to this approved Type Certificate.
TCDS vs. Aircraft Specification: History, Legal Standing, and Revisions
The FAA test guide explicitly directs IA applicants to know the differences and history of these two documents and how revisions are noted, so treat this as a graded topic rather than trivia.
Type Certificate Data Sheets were originated and first published in January 1958. Under 14 CFR 21.41, the data sheet is part of the type certificate, which makes a TCDS evidence that the product has been type certificated. TCDSs are generally compiled from details supplied by the type certificate holder, and the FAA may require additional details when conditions warrant.
Aircraft Specifications originated during implementation of the Air Commerce Act of 1926 and are FAA recordkeeping documents issued for both type-certificated and non-type-certificated products found eligible for U.S. airworthiness certification. Three consequences follow, and each is testable:
- A Specification is not part of a type certificate. This is the sharp legal difference from a TCDS. It does not make the Specification any less usable for establishing conformity — it is still the FAA's official statement of the eligible configuration — but the two documents do not have the same certificate status.
- Specifications are no longer issued, yet they remain in effect and continue to be amended. An aircraft covered by a Specification does not "graduate" to a TCDS by age.
- Conversion is optional and has a price. A Specification covering a type-certificated product may be converted to a Type Certificate Data Sheet at the option of the type certificate holder — but doing so requires the holder to furnish an equipment list. That single requirement is why many legacy products still sit on Specifications.
Worked examples. Piper's J-3 series is covered by Aircraft Specification No. A-691; the Piper PA-18 Super Cub is covered by TCDS 1A2; the Cessna 172 series is covered by TCDS 3A12. Do not assume that "old airplane" means "Specification" — check the actual document number and its heading.
How revisions are noted. Each sheet carries a revision number and date in the box at the top of page one, and the FAA reissues the entire document at each revision rather than issuing errata pages. The date in that box is the date of the most recent revision — not the date the type certificate was issued, not the date the sheet was reissued to a new holder, and not a library upload date. Before using any sheet for a conformity determination, confirm from that box that you are holding the current revision, since engine eligibility, serial-number breaks, and notes change between revisions.
When inspecting a CAR 3 aircraft, the IA uses its Aircraft Specification exactly as an IA inspecting a Part 23 aircraft uses the TCDS: as the authoritative statement of approved engines, propellers, limits, placards, and equipment against which conformity is judged under 14 CFR § 43.15(a)(1).
Anatomy of a Type Certificate Data Sheet
An IA must navigate every section of a TCDS during an inspection or alteration audit:
| TCDS Section | Primary Data Contained | IA Conformity Verification Task |
|---|---|---|
| Title Block & Header | Sheet number, revision number and date, TC holder, approved models, certification basis (e.g., CAR 3 or Part 23) | Confirms the sheet is the current revision and identifies the baseline certification rules |
| Powerplant Limits | Approved engine models, rated horsepower, max continuous RPM, manifold pressure, oil limits | Verifies engine data plate matches approved model suffix; checks operating limits |
| Propeller Limits | Hub and blade models, diameter limits (max/min), pitch settings, static RPM limits | Measures blade diameter; ensures static RPM during run-up falls within tolerances |
| Airspeed Limits | $V_{NE}, V_{NO}, V_A, V_{FE}, V_{LO}/V_{LE}$ in IAS and CAS | Verifies airspeed indicator markings (arcs and red line) match TCDS |
| Datum & Leveling | Exact datum location (e.g., firewall) and leveling points (e.g., fuselage screws) | Identifies reference datum and ensures aircraft is leveled properly for weighing |
| CG & EWCG Range | Forward/aft operating CG limits; Empty Weight Center of Gravity (EWCG) ranges | Checks weight and balance; if EWCG falls within range, adverse checks are unnecessary |
| Maximum Weights | Maximum Takeoff Weight (MTOW), Ramp Weight, Landing Weight | Confirms aircraft loading schedules do not exceed structural gross weight limits |
| Capacities & Arms | Total and usable fuel capacity, fuel arm, engine oil capacity, unusable fuel arm | Ensures unusable fuel and oil quantities/arms match weight and balance records |
| Control Surface Deflections | Deflection angles (degrees/inches) and tolerances for all primary and secondary controls | Measures travel with protractor/travel board to verify stops are within angular limits |
| Placards & Notes | Required cockpit limitations, fuel octane markings, baggage limits, spin restrictions | Confirms all mandatory placards specified in TCDS Notes are legible and installed |
Approved Engine and Propeller Combinations
A critical IA duty during an annual inspection is verifying that installed powerplants and propellers match the TCDS:
- Engine Suffix Designations: A Lycoming O-320-E2D and O-320-D2J are not legally interchangeable without an STC or Form 337 field approval. Suffix letters designate critical differences in crankshaft flange thickness, dynamic counterweights, accessory drives, or fuel systems.
- Propeller Diameter Tolerances: Every TCDS specifies a maximum and minimum allowable propeller diameter (e.g., "Not over 76 inches, not under 74.5 inches"). While AC 43.13-1B permits dressing out minor nicks, cutting down a propeller below the minimum TCDS diameter invalidates airworthiness.
- Static RPM Verification: Full-throttle static RPM measured during the mandatory engine run-up under 14 CFR § 43.15(c)(2) must fall strictly within the TCDS static RPM bracket to ensure proper propeller pitch and rated engine power.
Control Surface Travels and Rigging Tolerances
Control surface travel limits listed on a TCDS are flight safety limitations established during certification flight tests to prevent flutter, loss of control, or aerodynamic stall overbalance.
| Control Surface | Typical TCDS Deflection Specification | Allowable Tolerance | Functional Flight Safety Purpose |
|---|---|---|---|
| Ailerons | Up 20°, Down 15° | ±1° | Prevents adverse yaw; ensures roll control and boundary layer attachment |
| Elevator | Up 28°, Down 17° | ±1° | Guarantees flare authority on landing; prevents aerodynamic overbalance |
| Rudder | Right 28°, Left 28° | ±1° | Provides crosswind authority; limits structural empennage yaw loads |
| Elevator Trim Tab | Up 22°, Down 7° | ±1° | Maintains longitudinal trim across the entire CG envelope |
| Wing Flaps | Down 0° to 40° | ±2° | Ensures symmetrical lift and drag performance during approach |
The IA measures travels using an inclinometer, universal propeller protractor, or rigging board. If travel stops allow deflection beyond or below published tolerances, the aircraft fails type design conformity and cannot be approved for return to service.
Physical Conformity Audits and Detecting Unapproved Modifications
During an annual inspection, the IA must systematically cross-reference the physical aircraft against the TCDS:
- Serial Number Eligibility: TCDS listings feature serial number breaks reflecting design updates (e.g., electrical system revisions or gross weight increases applicable only to serial numbers 17270000 and subsequent).
- Required Equipment Lists: Items preceded by an asterisk (*) or identified as required must be installed unless deferred under an approved MEL.
- Detecting Unapproved Modifications: Non-conforming avionics, aftermarket alternators, unauthorized propeller models, or unapproved seating arrangements violate type design unless substantiated by an STC, FAA Form 337, or manufacturer amendment.
- Mandatory Placards (TCDS Notes): Numbered Notes at the conclusion of the TCDS specify mandatory cockpit limitation placards, fuel filler octane labels, and baggage capacity warnings. Under 14 CFR § 91.9, missing or modified placards render the aircraft unairworthy.
Common Exam Traps & IA Watchpoints
[!WARNING] High-Yield Exam Traps for Section 4.2:
- Trap: Missing TCDS Placards: A missing baggage limit placard or fuel octane label is not a minor aesthetic flaw; it grounds the aircraft under 14 CFR § 91.9.
- Trap: Excess Control Travel: Excess travel is never "safer." Deflections exceeding TCDS maximums can cause aerodynamic flutter, control lockup, or primary structure overstress.
- Trap: Propeller Diameter Under Minimum: Shortening propeller blade length below the minimum TCDS diameter violates type design, even if the cut was made to dress out nicks.
- Trap: Engine Suffix Discrepancies: Engine model numbers must match the TCDS down to the exact suffix letter unless supported by an approved STC or Form 337.
- Trap: "A Specification Is Part of the Type Certificate": It is not. A TCDS is part of the type certificate under 21.41; an Aircraft Specification is an FAA recordkeeping document. Both are still used to establish conformity.
- Trap: The Date in the Box: The date printed in the box on the first page of a data sheet is the date of the most recent revision, not the date of original issuance or reissuance to a new certificate holder.
During an annual inspection of a light single-engine aircraft, the IA inspects the engine data plate and notes the installed powerplant is a Lycoming O-320-D2J. The aircraft TCDS specifies that approved powerplants are the Lycoming O-320-E2D and O-320-E3D. No STC, FAA Form 337, or manufacturer amendment is found in the aircraft records. What is the regulatory determination regarding the aircraft's airworthiness?
While inspecting the flight control system during an annual inspection, an IA measures the rudder deflection using a universal propeller protractor. The TCDS specifies rudder travel as 28° Right (±1°) and 28° Left (±1°). The IA measures 33° Right travel. What action must the IA take?
Where are mandatory operational limitations, weight and balance datum definitions, and required cockpit limitation placards published for an aircraft certificated under the Civil Air Regulations (CAR 3)?