12.2 Reading Type Data: Serial-Number-Specific Lookups & Interpreting Notes

12.2 Reading Type Data: Serial-Number-Specific Lookups & Interpreting Notes

[!NOTE] The IAR test supplies the data; it grades the lookup. The Computer Testing Supplement for Inspection Authorization provides excerpts of data sheets, specifications, ADs, and charts. Nothing in this section needs to be memorized aircraft by aircraft. What must be automatic is the method: identify the model section, confirm the serial number falls in range, apply the Notes, and read the right line.

Section 4.2 established what a TCDS and an Aircraft Specification are. This section is about working them.

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How a Data Sheet Is Organized

Every FAA data sheet follows the same skeleton, and knowing it turns a five-minute hunt into a fifteen-second lookup:

HEADER          Sheet number, revision number and date, TC holder, models covered
   |
   v
MODEL SECTION   Repeated once per model (e.g., "I - Model J3C-40", "II - Model J3C-50")
   |            Within each model section, in a consistent order:
   |               Engine
   |               Fuel
   |               Engine Limits
   |               Propeller and Propeller Limits (diameter max/min, static rpm)
   |               Airspeed Limits
   |               C.G. Range
   |               Empty Weight C.G. Range
   |               Maximum Weight
   |               Number of Seats (with arms)
   |               Maximum Baggage (with arm)
   |               Fuel Capacity (with arm)
   |               Oil Capacity (with arm)
   |               Control Surface Movements
   |               Serial Nos. eligible
   v
DATA PERTINENT TO ALL MODELS   Datum, leveling means, certification basis,
                               production basis, equipment
   |
   v
NOTES           Numbered notes that modify, restrict, or extend the data above

Two structural facts drive most lookup errors. First, the model section is authoritative for that model and does not carry over to the next model — engine limits for a J3C-50 tell you nothing about a J3C-65. Second, the Notes are not commentary; they are part of the approved data and frequently narrow eligibility by serial number.

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Serial Number Eligibility

Each model section ends with the serial numbers eligible under it, and Notes commonly carve out subsets. A worked example from Aircraft Specification A-691 (Piper J-3 series) shows the pattern: the base model carries a CG range of (+10.6) to (+22.7), and Note 3 lists specific serial numbers that are eligible only with a restricted CG range of (+10.6) to (+21.5) as a landplane, with different limits on floats.

For the IA this is the whole ballgame:

1. Read the data plate, not the paperwork, for the serial number.
2. Find the model section that lists that serial number.
3. Read every Note referenced in that section, and scan the Notes for any that name serial numbers.
4. Apply the most restrictive applicable value.

Skipping step 3 produces confidently wrong answers, because the base data looks complete on its own.

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Extracting Weight and Balance Items

Data sheets carry the constants that a weight and balance revision depends on, and the exam asks for them directly:

Unusable fuel and undrainable oil deserve special mention because they are the most commonly asked lookup. Empty weight includes unusable fuel (Section 6.1), so the data sheet's weight and arm of unusable fuel are inputs to the empty weight and empty weight moment. A question asking for "the location for weight and balance purposes of any unusable fuel" on a specific serial number is asking you to find the right model section, check the Notes for a serial-number-specific value, and read the arm.

The EWCG range shortcut, stated on the data sheet itself in the classic formula: "When empty weight C.G. falls within range given, computation of critical fore and aft C.G. positions is unnecessary." That sentence — printed on the specification, not merely a handbook convention — is the regulatory basis for the adverse-check exemption discussed in Section 6.1. Note the caveat that usually follows it: the range is not valid for non-standard arrangements.

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Interpreting the Notes

Notes carry the operational meat. Common Note types and what they do:

A useful discipline: read the Notes before the model data, not after. Notes reframe what you are about to read, and reading them last means re-reading everything.

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When the Data Sheet Does Not Have It

Not everything lives on the data sheet, and knowing where else to look is itself an exam topic.

• Marking and placard lists for many later aircraft are carried in the FAA-approved Airplane Flight Manual rather than in the TCDS Notes. The certification rules require operating limitations to be furnished in the form of placards, markings, and manuals, so on a modern airplane the AFM is the authoritative list. If a data sheet is silent on placards, the approved flight manual — not the maintenance manual and not the sales literature — is the next document.
• Operating limitations for an aircraft whose TCDS does not itemize them are found in the approved flight manual.
• Instructions for Continued Airworthiness, including any Airworthiness Limitations Section, come from the design approval holder under § 21.50(b), not from the data sheet (Chapter 7).
• Required equipment for a kind of operation comes from the Kinds of Operations Equipment List in the AFM and from § 91.205 (Section 7.3), not from the data sheet.

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A Repeatable Lookup Procedure

1. Read the data plate: make, model, serial number.
2. Open the correct data sheet and confirm the REVISION DATE in the header box.
3. Locate the model section that lists this serial number.
4. Read every Note that section references, plus any Note naming serial numbers.
5. Read the specific line asked for (engine, arm, capacity, travel, seats).
6. Apply the most restrictive applicable value.
7. Cross-check against the aircraft's records for STCs or 337s that changed it.

Step 7 is the one an inspector adds that a test-taker sometimes forgets: the data sheet describes the aircraft as type certificated. Approved alterations legitimately move the aircraft away from that baseline, and the current approved configuration is the data sheet plus the STCs and Form 337s in the records.

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High-Yield Exam Traps

• Serial number governs. Model alone is not enough; Notes routinely restrict specific serial ranges.
• The revision date is in the box on page one, and it is the date of the most recent revision.
• Unusable fuel has both a weight and an arm, and both are on the data sheet.
• "When empty weight C.G. falls within range given, computation of critical fore and aft C.G. positions is unnecessary" — and the range is not valid for non-standard arrangements.
• If the data sheet is silent on placards or operating limitations, go to the approved flight manual, not to the maintenance manual.
• The data sheet is the type-certificated baseline; approved STCs and 337s in the records modify it.