We're happy to review prints or tooling layouts before they show up flagged in an audit.
+1 (262) 255 0223
EDGE SPEC
Why FAA & DoD Audits Don’t Care About Supplier Excuses
Issue 103
The issue that showed up at the worst possible time
We were just weeks out from FAA production readiness on a flight control module for a hybrid eVTOL program. Most of the subassembly was pretty standard: lightweight EMI shielding over a controller board, all housed in a compact magnesium chassis.
The stamped aluminum grounding bracket had already been through EVT and DVT cycles with no red flags. But when the first pre-launch production lot hit incoming inspection, the QA team paused it. A sharp edge — right on the grounding tab that makes chassis contact. The part wasn’t out of dimensional tolerance. But it didn’t meet FAA expectations for surface finish on contact features. And without a specified edge break or burr limit on the print, we had no clear basis for enforcing rework.
What made it worse was timing. The final FAA document package was in motion, PPAP Part Submission was next, and any change at this stage meant re-review, possibly revalidation. We weren’t at risk of a full stop — yet. But it was enough to trigger escalation.
Where the drawing and process weren’t aligned
The grounding tab had a modeled chamfer in CAD, but it wasn’t translated into a ballooned dimension or spec’d on the 2D print. The edge looked clean from a tooling standpoint — no visible burrs, no hanging material — but the profile came off the die sharp, with no radius and no control on contact resistance variation.
The tool itself used a high-speed progressive setup, and the forming station ran the tab through a basic bend and trim. No coining. No secondary deburr. No in-line edge break. From the supplier’s side, it met print. But from a compliance standpoint — particularly for electrical grounding in a flight system — it didn’t meet functional expectations.
These are the kinds of issues that don’t always show up in lab testing or pilot builds. They show up when regulators look for traceability, documentation, and process control — and ask, “How are you verifying this edge condition?”
How we addressed it (and avoided a finding)
We met with the tool builder, quality lead, and design owner. First, we updated the drawing to specify a 0.015” ±0.005” radius on the grounding edge — and flagged it as a CTQ feature linked to electrical performance.
Then we looked at feasibility. Adding a coining station wasn’t realistic this late in tool life. Instead, the supplier proposed a low-force rotary deburr station downstream, with a 100% inspection using an optical edge radius measurement setup. We validated five lots with this update, pulled contact resistance data, and closed the loop with the audit team through an ECN and supporting control plan.
Was it clean? No. We lost six business days on the re-approval process. But it saved us from a finding and avoided a formal deviation — and now that edge spec lives upstream where it belongs.
What I learned (again)
If you’re sourcing stampings for flight systems, and there’s any contact feature — grounding, bonding, fastener mating — you can’t leave the edge open to interpretation.
Spec the radius. Define the finish. Tie it to inspection.
And don’t assume a clean part equals a compliant one. In aerospace, you need to show how it’s controlled — not just how it looks.