Tool Control in Aviation: How MROs Keep Tools Out of Aircraft

Tool control in aviation is the routine that makes sure every tool taken to an aircraft comes back before the aircraft is released, because a tool left in an engine inlet, a wing bay or a control run is foreign object debris. MROs do it with kits that show a missing tool on sight, a check-out record for every tool that leaves the crib, and counts at shift change and before every panel closes.

TL;DR:

  • Aircraft tool control exists to stop tools and hardware becoming FOD. The FAA lists mechanics' tools among typical FOD items.
  • Day to day it runs on four things: foam kits with one pocket per tool, check-out and check-in, counts at shift change and before closure, and a lost-tool procedure.
  • FAA documents set the baseline (account for tools, keep them under control, calibrate them); the method is written into your own procedures.
  • Automated cabinets add a record of who took which tool and when. They support your FOD procedures; they do not replace them.

Table of Contents

Why Aircraft Tool Control Matters

A wrench left on a nacelle or a screwdriver dropped into a bay does not stay put. On engine run it can be ingested; in flight it can migrate into a control run. That is FOD: foreign object debris, and the foreign object damage it causes. Our guide to what FOD means covers the terms and examples.

The FAA's own FOD guidance lists the usual culprits:

  • aircraft and engine fasteners: nuts, bolts, washers, safety wire;
  • aircraft parts;
  • mechanics' tools;
  • flight line items such as pens, badges and luggage tags.

Tools and hardware are the part of that list a maintenance organization fully controls. That is why a tool control system sits at the center of most aviation FOD programs, alongside the housekeeping, training and inspection covered in our FOD prevention program guide.

What the FAA Documents Say

Here is what the primary documents say, with the document numbers so you can check them.

  • AC 150/5210-24A, Airport Foreign Object Debris (FOD) Management (2024). For aircraft maintenance it advises accounting for nuts, bolts, washers and safety wire, and for hand tools used in repair jobs. It names checklists, shadow boards and cut-out tool tray liners as aids, and refers to NAS 412 for running a tool control program. It is an advisory circular: guidance, not a regulation.
  • 14 CFR 43.13(a). Anyone performing maintenance must use the tools, equipment and test apparatus necessary to complete the work in accordance with accepted industry practices.
  • 14 CFR 145.109. A certificated repair station must have the tools it needs, and they must be on the premises and under the repair station's control when the work is done. Test and inspection tools used to make airworthiness determinations must be calibrated to a standard acceptable to the FAA.
  • 14 CFR 145.211. The repair station's quality control manual must describe how measuring and test equipment is calibrated, including intervals.
  • FAA-S-ACS-1, Aviation Mechanic Airman Certification Standards. Applicants must understand "tool and hardware use and accountability" and must be able to "perform a foreign object damage control procedure."

"Account for hand tools used in repair jobs." (FAA AC 150/5210-24A, section 3.3.2)

None of these documents prescribes one tool control method. The detailed procedure is your organization's own, written into its manuals and shaped by customer contracts. The industry references are the AIA's NAS 412 FOD prevention standard and SAE AS9146, which sets FOD prevention program requirements for aviation, space and defense organizations.

How MRO Tool Control Runs Day to Day

MRO tool control is a loop: tools leave against a record, are counted while they are out, and come back against the same record.

  • Kits and foam. Tools are issued as kits, not loose. Each kit has an ID, and each tool sits in its own foam pocket with a contrasting color underneath, so an empty pocket shows from a step away. The FAA's "cut-out tool tray liners" are exactly this.
  • Check-out and check-in. A kit leaves the crib against a technician and a work order or task card, by chit, scan or card. Returning it closes the record. Loose tools borrowed from another kit are where the loop usually breaks.
  • Shift-change counts. The outgoing technician counts the kit, the incoming one accepts it. An open count is handed over in writing, never verbally.
  • Pre-closure counts. Before an access panel, cowling or fairing is closed, before an engine run and before release, the kits used on that job are counted complete.
  • Hardware accountability. Nuts, bolts, washers and safety wire are counted in and out too, in a tray or tote, as the advisory circular asks.

Calibrated tools add one more check: the due date. A torque wrench past its calibration date is a controlled tool you should not issue.

The Lost-Tool Procedure

Every aviation tool control program needs a written answer to one question: what happens when a count does not close? Your quality and FOD procedures set the exact steps. A typical procedure runs like this:

  1. Stop work on the affected aircraft. Do not close panels, run engines or release the aircraft.
  2. Notify the supervisor or lead and quality straight away, with the kit ID, the tool, the aircraft and the zones worked.
  3. Search the work area, the aircraft zones and the technician's other kits and toolbox.
  4. Extend the search inside closed areas as your procedure directs, which can mean reopening panels or inspecting with a borescope.
  5. Record the result: found, where and by whom; or not found, with the decision and the name of the person authorized to make it.
  6. Find the cause and replace the tool before the kit is issued again.

What the hardware changes is step 2. With foam alone, a missing tool surfaces at the next count. With a record of who had the kit, the search starts with a name and a time.

Where Automated Cabinets Fit

An automated cabinet records what a manual count cannot: which user took which tool, and when. That matters most where several technicians or shifts share one cabinet.

The Teng Tools Smart Box automated tool control cabinet works like this:

  • Each user opens it with their own card. Any number of users per box; most existing company access cards work, with the card frequency confirmed before manufacture.
  • Sensors in the foam layout detect each tool as it is removed and returned. RFID tags on tools are available as an option; most sites do not need them.
  • Every change carries a user, a date and a time, on the cabinet screen and in the central platform, with outstanding tools listed.
  • Manager release, where you want it. Normal access stays locked until a supervisor verifies the cabinet and releases it, then reconciles outstanding tools at the end of the period.
  • The foam still works with the power off. Two-layer foam keeps the empty pocket visible during a physical inspection.

Be clear about the limit. The cabinet supports your FOD procedures; it does not replace them. It tells you a tool is outstanding and who opened the cabinet before it went. Your visual inspections, pre-closure checks and lost-tool procedure stay in place.

Smart Box is one of three tiers. A hangar can run foam everywhere, KIT digital audits on general kits, and automated cabinets on the critical ones. The tool control systems page compares the three. For RFID-on-tool systems, see RFID tool tracking in aviation maintenance; for other cabinet mechanisms, automated tool control compared.

What Most Aviation Tool Control Gets Wrong

Most aviation tool control is built around the end-of-shift count. That is the wrong count to rely on.

  • The count that matters is before the panel closes. A tool found missing at 6 p.m. may already be behind a fairing closed at 2 p.m. Count when the zone closes, not only when the shift ends.
  • Counting tools but not hardware. The FAA's list of typical FOD starts with fasteners and safety wire. A kit that is complete with a pocket of loose washers is not under control.
  • Treating the screen as the inspection. A cabinet showing every tool home proves the drawer is full. It does not prove the engine inlet is clean. Automated tool control speeds up the search; it is not the FOD walk.

Count when the zone closes, not when the shift ends.

Kit Out a Controlled MRO Workstation

Foam is where every aviation tool control program starts, and you can order it today.

Teng Tools 95 piece torque screwdriver and bit set in a FOAM2 contrasting foam tray

When several technicians or shifts share tooling and you need to know who removed what and when, the next step is an automated tool control cabinet built to your tool list. Smart Box is a Teng Tools cabinet with sensing and software from Automify (Tool Raptors Ltd, UK). Book a specification meeting with your tool list and how you audit today, or call (817) 767-3392. Government and defense buyers can start at our government page.

Sources

FAQ

What Is Tool Control in Aviation?

Tool control in aviation is the set of procedures that accounts for every tool and item of hardware used on an aircraft, so nothing is left behind as foreign object debris. It combines kits with one pocket per tool, check-out and check-in, counts at shift change and before closure, and a lost-tool procedure.

Does the FAA Require Tool Control?

Part 145 requires repair stations to keep the tools they need on the premises and under their control, and to calibrate tools used for airworthiness determinations. The FAA's FOD advisory circular, AC 150/5210-24A, advises that all tools be accounted for, and the mechanic certification standards test tool and hardware accountability. The specific method is set by each organization's own procedures.

What Happens When a Tool Goes Missing on an Aircraft?

Work stops and the aircraft is not closed up or released. The supervisor and quality are notified, the aircraft and work area are searched, and the outcome is recorded, including who authorized any release. The exact steps are set by the organization's FOD and quality procedures.

Can an Automated Tool Cabinet Replace FOD Checks?

No. An automated cabinet such as Teng Tools Smart Box records which user took which tool and when, and shows what is outstanding. Visual inspections, pre-closure checks and the lost-tool procedure stay in place; the cabinet supports them.