WHEN TO USE
Visual inspection or customer report of localised pitting/minor corrosion on any external engine metallic surface.
No obvious cracking, deformation, or composite damage.
Aircraft may be AOG or line-stop; quick disposition required.
SCOPE
External metallic surfaces only (e.g., fan case skins, external cases, brackets).
Excludes confirmed cracks, deep material loss, composite/Kevlar/carbon wraps, or prohibited zones.
Always apply the current AMM/EMM/SRM and company procedures—this article does not quote numeric limits.
SAFETY & PRECAUTIONS
Apply engine safety: chocks in, tags out, confirmed engine safe/isolated, FOD control.
Protect nearby composites, seals, and paint systems with approved masking.
Avoid aggressive abrasion; use only approved tools/chemicals per AMM/EMM.
TRIAGE – QUESTIONS TO CAPTURE (WITH THE CALLER OR ON SITE)
Aircraft tail/MSN; engine position (1/2) and S/N; airport/stand; AOG (Y/N).
Exact location (clock position and/or frame station; proximity to known features like flanges, fasteners, wraps).
Estimated affected area (mm² or cm²) and deepest pit (mm) if measured; otherwise visual estimate.
Any signs of coating lift, staining, fretting, or cracks.
Recent exposure to de-icers, salt, cleaning agents, or fluid leaks.
Photos available now (context + close-ups)?
EVIDENCE PACK – REQUEST THIS EVERY TIME
1× context photo showing the general area; 2–3× close-ups orthogonal to the surface.
Clocking/landmarks in the notes (e.g., “at ~6 o’clock behind local flange, forward of composite wrap”).
Dimensions: length × width of area; note density of pits (isolated vs clustered).
If authorised, a depth gauge/replica reading; otherwise note “visual only”.
Ambient conditions; last wash/inspection date; any chemical use.
Maintenance already performed.
QUICK DECISION GUIDE (ALWAYS CONFIRM WITH AMM/EMM/SRM)
| Severity (visual guide) | Typical indicators | Action (subject to manuals) |
|---|---|---|
| A. Minor pitting / light corrosion | Discolouration, shallow pin-prick pitting; no coating lift or cracks | Clean & treat on-wing, re-protect, record and monitor |
| B. Localised moderate pitting | Clustered pits, slight coating lift; structure appears sound | Minor blend (if permitted) + treat & refinish; NDT if required |
| C. Suspect structural / out-of-limit | Deep pits, cracks, near prohibited zones, adjacent composite affected | Stop & escalate: engineering disposition, NDT/borescope; consider shop visit |
ON-WING WORKFLOW (FIELD CHECKLIST)
Stabilise & document: secure area, take photos, note clocking/landmarks.
Clean: remove loose corrosion/contaminants using approved media/chemistry.
Re-inspect: confirm pits are within permitted zones/limits; verify no cracks.
Treat: apply approved conversion/primer/finish per manual; record batch/lot and cure times.
If blending is permitted & required: perform light blend within allowable depth/taper; refinish.
Protect & release: ensure edges sealed, no debris; perform ops check if applicable; complete logbook and SCC case.
Escalate immediately if cracks, composite damage, coating delamination into protected areas, or out-of-limit depth/area.
PARTS, MATERIALS & TOOLING (EXAMPLES – USE LOCAL APPROVALS)
Approved corrosion remover/neutraliser, solvent wipes, lint-free cloths.
Masking for adjacent composites/seals/finishes.
Non-marring hand tools; measurement gauge/replica kit where authorised.
Approved conversion coating, primer, topcoat per finish specification.
PPE per SMS; waste disposal materials.
CUSTOMER MESSAGING – STOCK PHRASES
“Your photos show localised surface pitting on an external metallic surface; no cracking evident.”
“We’ll proceed with clean & treat on-wing in line with the maintenance manual; we’ll blend only if explicitly permitted.”
“If measurements exceed limits or we see cracks, we’ll escalate to Engineering and advise next steps.”
“Target on-site time 2–6 hours (access-dependent); we’ll provide hourly updates.”
SCC DISPATCH LOGIC
If the airport is Contoso-served, dispatch Contoso Engineers with materials/tooling above.
If partner-served, issue Service Authorisation Number (SAN) and Contoso work instructions; partner works under Contoso QA and documentation.
SCC posts timeline updates at dispatch / on-site / work started / work completed / RTS recommendation.
CASE CAPTURE – MINIMUM DATA (Dynamics 365)
Title: “Engine External Surface Pitting – [Location/Clocking]”
Tail/MSN | Engine S/N & position | Airport/Stand | Priority/AOG (Y/N)
Fault description (clocking, distance to features, nearby composites)
Photo links | Area (L×W) | Depth (if measured) | Materials used (batch/lot)
Work performed (clean/treat/blend) | Cure times | Disposition (GO/NO-GO) | Re-inspection interval
GO/NO-GO & RTS (RETURN TO SERVICE)
GO: within limits, treated/refinished, no secondary damage; schedule follow-up per manual.
NO-GO: out-of-limit depth/area, any crack indication, affected composites/prohibited zones, or uncertainty → hold, escalate, and document.
APPENDIX – 30-SECOND CALL SCRIPT
“Confirm tail/MSN, engine S/N/pos, airport/stand, AOG.”
“Describe location with clocking and landmarks (flanges/fasteners/wraps).”
“Send context + close-up photos and any area/depth estimates.”
“We’ll decide clean & treat vs minor blend vs escalate per manuals and confirm ETA.”