NDT Requirements for Aerospace FAI: A Practical Guide

I worked with a Tier 2 aerospace supplier whose magnetic particle inspection vendor had let their NADCAP certification expire by three months. The supplier did not know. Every FAI submission referencing that vendor for those three months had cited an uncertified inspector. The customer's annual quality audit caught it. Forty-seven FAIs had to be redone, the customer issued a formal supplier escalation, and the precision shop spent six weeks rebuilding the documentation trail. NDT certification chains are the part of FAI that quietly breaks.

Non-destructive testing (NDT) is the verification layer that catches defects that visual or dimensional inspection cannot. Internal porosity in a casting. Surface cracks in a fatigue-loaded structural part. Inclusion in a forging. Bond integrity in a composite assembly. Each NDT method has its own physics, its own acceptance standards, and its own certification flow-down requirements. Aerospace FAI documentation depends on all three being right.

This guide covers NDT requirements for aerospace FAI: which methods apply to what defect types, the NADCAP flow-down requirements, how to document NDT on Form 3, and the certification chain mistakes that quietly produce non-conforming FAI packages. The general AS9102 baseline is in How to Balloon a Drawing for FAI and AS9102 Form 1 vs Form 2 vs Form 3 Explained.

NDT Requirements for Aerospace FAI: The Method Landscape

Each NDT method detects a specific class of defect through a specific physical phenomenon:

Liquid Penetrant Inspection (LPI / PT / FPI)

Detects surface-breaking defects on non-porous materials (typically non-ferrous metals like aluminium, titanium, stainless). The part is cleaned, a penetrant dye is applied, excess is removed, a developer is applied, and surface-breaking defects show as visible indications.

When to apply:

• Cast aluminium parts after surface preparation

• Forged titanium parts before final machining

• Welded aluminium assemblies after welding

• Any non-ferrous structural part where surface cracks would be safety-critical

Documentation on Form 3: one Form row per LPI requirement, with acceptance standard (ASTM E1417, customer-specific) and inspector certification reference.

Magnetic Particle Inspection (MPI / MT)

Detects surface and near-surface defects on ferromagnetic materials (carbon steel, some stainless grades). The part is magnetized, magnetic particles are applied, and defects show as particle accumulations at the defect location.

When to apply:

• Steel forgings after surface preparation

• Welded carbon steel assemblies

• Heat-treated steel parts after heat treat

• Critical fatigue-loaded steel components

Ultrasonic Testing (UT)

Detects internal defects throughout the volume of the part. A high-frequency sound wave is transmitted; reflections from defects indicate size and location.

When to apply:

• Forged steel parts (internal defects)

• Full-penetration welded structures

• Thick aluminium plate

• Critical bond integrity (composites)

Radiographic Testing (RT / X-ray)

Detects internal defects through density variation. X-rays pass through the part; defects show as density variations on film or digital detector.

When to apply:

• Cast aerospace components (porosity, inclusions, shrinkage cavities)

• Welded structures where UT is impractical

• Composite parts (void content)

• Brazed assemblies (joint integrity)

Eddy Current Testing

Detects surface and near-surface defects via electromagnetic induction. Used on conductive materials.

When to apply:

• Aircraft skin inspection for fatigue cracks

• Heat exchanger tube inspection

• Some thread inspection applications

We covered casting-specific NDT in Casting Surface Defect Inspection Requirements for AS9102 FAI. The composite-specific applications are in Composite Parts FAI: Why Layup Inspection Differs from Machined Parts.

NADCAP Flow-Down Requirements

Aerospace NDT is governed by NADCAP (National Aerospace and Defense Contractors Accreditation Program). The flow-down is strict:

• The NDT processor must be NADCAP-certified for the specific method being used

• The certification must be in scope for the specific test parameters

• The certification must be current at the time of inspection

• The inspector performing the NDT must have current personnel certification (per ASNT or equivalent)

A NADCAP-certified MPI vendor whose certification has expired is, for FAI purposes, equivalent to an uncertified vendor. The FAI documentation falls.

We covered NADCAP basics in NADCAP Special Process Requirements for AS9102 FAI and the audit preparation is in NADCAP Audit Preparation for Aerospace Shops.

What to Document on Form 3 for NDT

A typical NDT Form 3 row:

Field	Value
Characteristic #	67
Reference Location	Sheet 1, General Note 12
Designator	Major
Requirement	"Liquid penetrant inspect per ASTM E1417, Type 1 Method C"
Acceptance	"No linear indications, no rounded indications over 1.5mm"
Inspection Method	"LPI per ASTM E1417, NADCAP-certified vendor"
Vendor Cert Reference	"ABC NDT Lab, NADCAP cert MMM 2/2026, expires 2/2028"
Actual Result	"Conforming, no rejectable indications"
Conformance	Pass

The Vendor Cert Reference field is what saved the supplier above from a worse outcome — explicitly documenting the cert number and expiration is auditable evidence that they verified the vendor at the time of inspection. We documented broader designator assignment in How to Assign Designators in AS9102 Form 3.

How to Identify NDT Requirements on the Drawing

NDT requirements appear in several places on a drawing:

1. General notes block (most common): "Liquid penetrant inspect per ASTM E1417 after heat treat"

2. Material specification section: some material specs include NDT requirements as part of acceptance

3. Specific feature callouts: "Critical surface — radiographic inspect per AMS 2175 Class A"

4. Cross-references: "Inspection per Boeing PVS-XXXX-NDT" or "Per Airbus AIPS-XX-XX-XX-XX"

5. Process notes: post-weld NDT, post-heat-treat NDT, etc.

Missing the NDT callout from any of these locations means missing the inspection requirement entirely. The "last sheet attention drop" we documented in Manual Ballooning vs Auto-Ballooning Head-to-Head hits NDT requirements often because they tend to be on later sheets.

NDT vs Dimensional Inspection: They Are Both Required

Common misconception: "I CMM'd every feature, so the FAI is complete."

Wrong. Dimensional inspection verifies geometry. NDT verifies internal soundness. A part with perfect dimensions and a 2mm internal porosity defect at a fatigue-critical location is a failed part. The dimensional CMM cannot see the porosity. NDT does.

Aerospace FAI requires both. The Form 3 must include both dimensional rows and NDT rows. Each NDT requirement is its own row. We covered the dimensional methods in Inspection Method Selection: When to Use CMM, Calipers, or Bore Gauge.

Common NDT FAI Mistakes

Missing NDT requirement on Form 3. The drawing says LPI per ASTM E1417 but the supplier focuses on dimensions; LPI is performed but never documented on Form 3. Customer reviewer notices.

Vendor cert expired at inspection date. The supplier's LPI vendor's NADCAP cert lapsed. The supplier did not check. FAI references invalid certification.

Wrong NDT method for the material. Specifying MPI for an aluminium part (MPI requires ferromagnetic material). Inspector cannot perform the method. Wrong method specified.

Wrong acceptance standard. Drawing references AMS 2175 Class A; supplier inspects to ASTM E1417 (different defect classification). Same NDT method, different acceptance criteria.

Missing inspector certification on Form 3. ASNT-certified inspector performed the NDT but the personnel cert is not referenced on Form 3. Auditable evidence gap.

The broader pattern of FAI rejection causes is in Common AS9102 Form 3 Rejection Reasons and First Article Inspection Failure Causes. The corrective action workflow when rejection happens is in AS9102 FAI Rejection Response and Corrective Action.

NDT Cost and Timing for FAI Planning

For estimation:

Method	Typical cost per part	Typical lead time
LPI (small part)	$25–75	1–2 days
MPI (small part)	$30–80	1–2 days
UT (volumetric)	$100–300	3–5 days
RT (radiographic)	$200–500	5–10 days (with film development)
Eddy current	$50–150	2–3 days

NDT lead time often dominates FAI lead time. A supplier planning FAI submission needs to factor in NDT turnaround. We covered the broader FAI cycle time benchmarks in How Long Does FAI Preparation Take in Aerospace and the FAI cycle time reduction in Reduce FAI Cycle Time Without Adding Headcount.

Mavlon Identifies NDT Requirements from the Drawing

Mavlon reads general notes, material specs, and process callouts to identify all NDT requirements on a drawing. Each requirement becomes a Form 3 row with the correct method, acceptance standard, and the placeholder for vendor cert reference. The QE adds the actual vendor cert and inspection result at the time of inspection.

Upload a Drawing to see NDT-aware Form 3 generation.