A single undocumented cleaning step can ground an aircraft, fail an audit, and invalidate an airworthiness release. In New Zealand aerospace and defence maintenance, where NZCAA Part 145 and AS9100 Revision D govern every process from incoming inspection to final sign-off, cleaning is not a housekeeping function. It is a controlled, validated, and fully traceable process step, and the regulatory framework treats it as nothing less.
For maintenance, repair, and overhaul organisations operating under these constraints, industrial ultrasonic cleaning equipment represents a technically and procedurally defensible solution. Unlike manual solvent methods or generic spray washers, purpose-built ultrasonic systems deliver programmable cycle parameters, logged process data, and reproducible cavitation performance across high-value components including fuel nozzles, hydraulic actuators, and turbine blades.
This analysis works through the specific compliance architecture that applies to component cleaning in New Zealand aerospace and defence. It examines how AS9100 classifies cleaning as a special process, what NZCAA Part 145 actually requires at the component level, where informal cleaning methods create audit exposure, and how to specify, validate, and operationalise an ultrasonic cleaning process that satisfies both the standard and the regulator.
Why ‘Clean Enough’ Fails the AS9100 and NZCAA Audit
Under AS9100 Revision D, component cleaning is not a background task. Clause 8.5.1.2 classifies cleaning as a special process when residual contamination cannot be fully detected after assembly, and special processes carry a mandatory control burden: validated procedures, qualified equipment, defined acceptance criteria, and retained objective evidence. A technician’s visual judgement satisfies none of these requirements. Neither does a soak tank with no temperature log and no chemistry concentration record.
NZCAA Part 145 approved maintenance organisations face an equivalent and parallel obligation. Component cleaning must be performed in accordance with approved data, typically the OEM maintenance manual, and the maintenance release attests that this occurred. Where the actual cleaning method deviates from the approved procedure, or where no procedure exists, the release is deficient regardless of how clean the part looks. Records must be traceable to the specific component by part number and serial number, to the applicable work order, and to the operator who performed the process, the specific traceability elements required are detailed in the Part 145 section below.
When an auditor reviews a Part 145 organisation, the expectation is concrete: a written cleaning process specification, evidence that the equipment used is qualified and maintained, confirmation that the approved chemistry was used at the correct concentration, and a cycle record that ties back to the work order. Organisations that cannot produce this documentation package receive a finding, not a conversation.
Defence maintenance contractors operating under NZDF technical airworthiness frameworks carry compliance obligations across multiple layers. The RNZAF has adopted the Defence Aviation Rules aligned with international military best practice, and AS9100 certification, NZCAA airworthiness approvals, and OEM-specified cleaning procedures must all be satisfied simultaneously. Informal or undocumented cleaning practices create a systemic compliance gap across all these frameworks at once. For organisations evaluating their current position, understanding what procurement and specification criteria genuinely matter for industrial ultrasonic cleaning equipment is a practical starting point before any process improvement programme begins.
How AS9100 Revision D Defines Cleaning as a Special Process
Understanding precisely where cleaning sits within AS9100 Rev D is essential before evaluating any process or equipment decision.
Clause 8.5.1 governs production and service provision and contains the special process requirement. A special process is any process where the output cannot be fully verified by subsequent inspection. Component cleaning meets this definition directly: once a fuel nozzle is reassembled or a hydraulic actuator is reinstalled, residual contamination in internal passages is no longer accessible for detection. The cleaning outcome is locked in. That places cleaning unambiguously in the special process category, requiring validation, parameter control, and documented evidence, not post-process inspection alone.
Clause 7.5 on documented information extends this obligation into record-keeping. Every cleaning process input, including chemistry type, concentration, temperature, cycle time, and ultrasonic frequency, must be documented and retained, along with acceptance criteria and equipment parameters. For a broader overview of compliance frameworks, supporting ISO and industry certification provides useful context.
On process validation, AS9100 is explicit: objective evidence must demonstrate that a process reproducibly achieves the required outcome under defined conditions. The record must show consistent results across representative components under documented parameters, a requirement addressed in detail in the validation section below.
Equipment qualification follows directly. The ultrasonic cleaning unit must be maintained, calibrated where applicable, and confirmed to operate within validated parameters. Units without stable, characterised frequency and power output cannot support a validatable process; if equipment performance drifts after validation, the process is no longer controlled.
Clause 6.1 requires risk-based thinking. Organisations must identify the consequences of inadequate cleaning on specific components and implement proportionate controls. For fuel nozzles, hydraulic actuators, and turbine blades, those consequences include in-service failure. The risk register must reflect that, and cleaning process controls must be proportionate to it.
NZCAA Part 145 and Component Cleaning: What the Regulation Actually Requires
Where AS9100 Rev D establishes the quality management framework for special process control, NZCAA Part 145 imposes the airworthiness regulatory layer that directly governs how New Zealand approved maintenance organisations execute and document component cleaning.
Part 145 requires maintenance to be performed in accordance with approved data. For component cleaning, that approved data is typically the OEM maintenance manual, which specifies cleaning method, approved solvent or aqueous chemistry, soak times, and rinse requirements as mandatory parameters, not guidance. Substituting an alternative chemistry or method, even one that produces a visually acceptable result, is a departure from approved data.
The MOE creates a second compliance obligation. The accountable manager and quality manager are responsible for ensuring the Maintenance Organisation Exposition accurately describes how cleaning is actually performed. A gap between the MOE procedure and the shop floor practice is a non-conformance, regardless of whether the cleaned component meets its acceptance criteria. Outcome quality does not remedy a process deviation.
The maintenance release depends on it. As established above, a Part 145 maintenance release attests that work was performed in accordance with approved data. Where the cleaning process used is not the approved process, that attestation is false, rendering the release invalid regardless of physical condition.
NZCAA’s alignment with ICAO Annex 6 and its adoption of frameworks consistent with EASA Part 145 mean these expectations are internationally consistent. New Zealand MROs pursuing EASA bilateral recognition will face equivalent process documentation scrutiny during foreign authority assessments.
Traceability requirements sharpen the record-keeping obligation further. Cleaning records must link the specific component by part number and serial number to the work order, the approved data reference, the chemistry batch, and the technician. A paper logbook entry recording “cleaned” against a job number satisfies none of these requirements. The record must be structured, retrievable, and auditable.
The Compliance Failure Modes of Manual and Informal Cleaning Methods
Where Part 145 defines what the record must contain, manual and informal cleaning methods fail at a more fundamental level: they cannot consistently produce a record worth keeping.
Manual spray cleaning, hand wiping, and unagitated soak tanks introduce uncontrolled variables at every step. Dwell time varies by operator. Chemistry concentration drifts between batches. Mechanical agitation is neither defined nor measurable. The cleaning record, where one exists, typically captures only that cleaning occurred, not the conditions under which it was performed. That distinction separates a process record from a logbook entry.
Without defined, repeatable parameters, process validation is structurally impossible. An organisation can document that a component appeared clean to a specific inspector on a specific occasion. It cannot demonstrate the same outcome will be achieved on the next component, by a different technician, in different ambient conditions. AS9100 requires objective evidence of repeatable process performance; individual inspection acceptance is not a substitute.
The geometry problem compounds the documentation problem. Unagitated soak tanks rely on diffusion and gravity to carry chemistry into blind holes, internal passages, and tight clearances. For components such as fuel nozzles and hydraulic actuators, this is insufficient regardless of chemistry selection or extended soak time. Contamination in inaccessible areas simply remains. The same challenge applies across complex industrial components, as explored in this analysis of ultrasonic cleaning for mining and heavy engineering applications where hardened deposits defeat conventional methods.
AS9100’s explicit treatment of human factors means that a cleaning process governed by technician skill rather than defined parameters is a vulnerability the standard is designed to address; process-level corrective action, not a revised checklist, is the appropriate response. That distinction matters because corrective action requires root cause analysis, process redesign, and evidence of effectiveness.
The operational cost follows directly. Incomplete cleaning generates rework, extends component hold time, and consumes re-inspection capacity on high-value parts. In a high-value MRO environment, that throughput loss is not recoverable through increased technician effort.
How Industrial Ultrasonic Cleaning Delivers Documented Process Control
Acoustic cavitation solves the geometry problem that manual methods cannot. Industrial ultrasonic cleaning equipment transmits high-frequency sound waves operating in the ultrasonic frequency range suited to aerospace component geometry through the cleaning fluid. These waves generate and collapse microscopic bubbles across every wetted surface simultaneously, including internal passages, blind holes, and complex geometries that brushes, spray lances, and soak tanks simply cannot reach.
The compliance advantage, however, is parametric control. Every variable that defines the cleaning process, ultrasonic frequency, power output, solution temperature, chemistry type and concentration, and cycle duration, is set, enforced, and recorded. Kleentek industrial systems are engineered to exceed 20 watts per litre, delivering consistent, powerful cavitation rather than the inconsistent output that characterises under-specified commodity equipment. At that power density, the process is characterisable; characterisable processes can be validated; validated processes satisfy AS9100 clause 8.5.1.
PLC and HMI control systems take this further. Cleaning programmes are named, stored, and recalled by component type or work order number. The same parameters execute identically regardless of which operator initiates the cycle, eliminating the technician-to-technician variation that an AS9100 auditor identifies as a human factors risk. The stored programme is itself the documented process specification the standard requires.
Automated cycle logging then generates the audit trail that Part 145 traceability demands. Each record captures the programme used, cycle start and end times, solution temperature, and operator identification. That data exports as a quality record and presents to an auditor as objective evidence of process control, not a technician’s attestation.
Equipment duty rating matters here. A process validated on a unit that subsequently drifts in frequency or power output is no longer a controlled process. Industrial-duty construction, with quality transducers bonded for continuous operation and stable generator output, ensures the hundredth component is cleaned under the same conditions as the validation sample. For more context on industrial cleaning process considerations, the Kleentek technical blog covers related application and compliance topics.
Matched Chemistry: Why the Right Cleaning Fluid Is Non-Negotiable
Parametric control governs the cleaning cycle, but it is the chemistry that does the actual work. Cavitation energy is a delivery mechanism: it drives cleaning fluid into intimate contact with contamination across complex geometries. Without the correct fluid, that energy is wasted.
Aerospace components present fundamentally different contamination profiles, and a single general-purpose cleaner applied across all types is both a cleaning efficacy failure and a compliance risk. Carbon lacquer and coke deposits on fuel nozzle internals require a chemistry formulated for carbonaceous breakdown. Hydraulic fluid degradation products and metallic wear debris on actuator components respond to a different alkaline profile entirely. Oxide scale and thermal deposits in turbine blade cooling passages demand chemistry matched to the base metal and any thermal barrier coating present. Mismatching chemistry to contamination produces incomplete cleaning; applying the wrong chemistry to the wrong substrate can cause irreversible damage.
Material compatibility is not a preference, it is a regulatory requirement. OEM maintenance manuals and applicable industry standards document approved cleaning agents for specific substrate classes. Aluminium alloys, titanium fasteners, nickel superalloys, and steel hydraulic components each carry restrictions that, if violated, render the maintenance release invalid. An incompatible chemistry that causes surface attack or intergranular corrosion does not produce a non-conforming clean, it produces an unairworthy component.
Aqueous alkaline formulations are well suited to carbon, grease, and general hydrocarbon contamination on steel and aluminium substrates. Specialised biodegradable formulations are available that meet both cleaning performance requirements and environmental discharge obligations without compromising efficacy. Selecting the right formulation for each application is covered in detail in A Practical Guide to Ultrasonic Cleaning Fluids for Industrial Use.
Kleentek supplies matched ultrasonic cleaning chemicals validated in conjunction with their equipment’s specific frequency and power profile. Chemistry is specified and qualified as part of the cleaning system, not sourced independently, ensuring the combined process delivers the documented, reproducible cleaning efficacy that AS9100 process validation requires.
Component-Specific Cleaning Considerations: Fuel Nozzles, Hydraulic Actuators, and Turbine Blades
Chemistry selection sets the foundation; what follows is how that chemistry performs against three component types that define the upper end of aerospace cleaning complexity.
Fuel Nozzles
Fuel nozzle orifice geometry is engineered to tight dimensional tolerances. Carbon lacquer and coke deposits accumulate in internal passages where no manual tool can reach without risk of dimensional damage. Flow performance is a certification parameter; a partially blocked orifice alters spray pattern and combustion efficiency in ways that affect airworthiness sign-off. Ultrasonic cavitation, paired with matched carbon-removal chemistry at controlled temperature, reaches every internal passage simultaneously without mechanical contact. Probing or rodding these passages risks dimensional damage and is typically precluded by the geometry involved.
Hydraulic Actuators and Servo Valves
Contamination in hydraulic components combines fluid degradation products, ingested particulate, and metallic wear debris. Cleanliness acceptance is quantified, typically referenced to a quantified particle count standard, meaning the cleaning process must be validated against a measurable criterion. Visual inspection alone cannot satisfy this standard. The rinse stage carries equal weight to the wash stage; particles mobilised during cavitation must be fully removed, not redistributed. A poorly executed rinse invalidates an otherwise effective wash cycle.
Turbine Blades and Vanes
Turbine components accumulate oxidation products, thermal barrier coating residue, and cooling passage blockage. OEM-approved procedures specify chemistry type, temperature ceilings, and explicitly prohibited processes to protect coating integrity and prevent base metal attack. Programmable temperature control and stored cycle parameters allow a Kleentek system to replicate these conditions repeatably across every component in a batch, with logged evidence that parameters were held within specification.
Multi-Stage System Architecture
All three component types require a complete cleaning sequence. A wash tank alone is insufficient; residue or mobilised contamination remaining on the component causes corrosion, interferes with NDT, or compromises coating adhesion. Kleentek’s integrated multi-line systems combine ultrasonic wash tanks, ultrasonic or cascade rinse tanks, filtration, and drying stages in a configurable architecture. For MRO facilities cleaning a mixed component range comparable to locomotive and precision engineering applications, the system layout can be built around the cleaning sequence mandated by applicable OEM maintenance manuals, with tank sizing and throughput matched to work order volume.
Validating and Qualifying Your Ultrasonic Cleaning Process for AS9100 Audit
With the component-specific cleaning requirements established, the question becomes how to convert that operational knowledge into documented, auditable evidence of process control.
Process validation under AS9100 clause 8.5.1 follows a defined sequence: specify all process parameters (frequency, power output, solution temperature, chemistry type and concentration, cycle time), run the defined process against contaminated test coupons or representative production components, measure the outcome against the acceptance criterion, and retain the protocol and results as objective evidence. Parameter specification flows directly to equipment qualification: confirming that the ultrasonic unit actually performs to its specification requires power output measurement, frequency verification, temperature control calibration, and tank uniformity checks to confirm consistent cavitation across the full working volume. Kleentek’s industrial systems are designed from the outset to support these activities, with stable generator and transducer performance that does not drift across extended operational duty cycles.
Chemistry qualification runs in parallel with equipment qualification. The cleaning agent, at the validated concentration and temperature, must be confirmed effective against the specific contamination on the specific substrate. Qualification methods should be matched to the component type and acceptance criterion, for example, functional testing where performance parameters are the acceptance standard. The chemistry and equipment are qualified together as a system, which is why specifying matched Kleentek chemistry alongside Kleentek equipment simplifies the validation documentation and establishes a single point of accountability.
The complete documentation package, comprising the process specification, equipment qualification records, chemistry validation data, and ongoing maintenance records, is what an AS9100 auditor will review. Organisations presenting this as a structured quality record set demonstrate process maturity and reduce audit risk materially.
Kleentek’s cleaning trials and technical support are directly useful at this stage. A pre-validation trial on representative components with the proposed configuration generates real process data, identifies parameter adjustments before the formal qualification run, and reduces the risk of a first-attempt validation failure.
Industrial Ultrasonic Cleaning Equipment vs. Commodity Units: A Compliance-Critical Distinction
A validated process is only as durable as the equipment sustaining it. Once qualification parameters are established, the equipment must reproduce them consistently across every subsequent cycle, not just during the validation run.
In aerospace MRO, that consistency is a structural engineering requirement. Transducer bonding integrity, generator frequency stability, and thermal management determine whether a cleaning system maintains its validated output under continuous operational duty. These are not differentiating product features; they are the baseline standards that separate industrial ultrasonic cleaning equipment from commodity units. When transducer bonds degrade or generator output drifts, the process drifts with it. A validated process operating on degraded equipment is no longer a controlled process under AS9100 Rev D, regardless of how thorough the original qualification was.
Low-cost ultrasonic units available through general industrial or consumer channels typically share several disqualifying characteristics: power densities well below 20 watts per litre, consumer-grade transducers not rated for continuous duty, and no process control interface capable of logging cycle parameters. An organisation that validates a cleaning process on such equipment faces a structural problem: the validation is tied to an equipment baseline that cannot be confirmed stable over time. AS9100 auditors reviewing maintenance and calibration records will identify this gap.
PLC and HMI controls are the mechanism by which process parameters are enforced and cycle records are generated, as discussed in the process control section. Without them, organisations must implement manual compensating controls, reintroducing the human factors variability that a documented process is designed to eliminate.
Kleentek’s industrial ultrasonic cleaning equipment is designed around the compliance requirement from the outset: power densities consistently exceeding 20 watts per litre, generators and transducers engineered for stable long-term industrial duty, and PLC/HMI controls supporting programmable cycle management and automated data logging. The role of supporting reliable equipment performance in maintaining process control over the equipment’s service life is fundamental to this architecture.
The total cost of ownership argument is unambiguous. An AS9100 non-conformance, a NZCAA audit finding, a rework cycle on a turbine blade or fuel nozzle, or an in-service failure attributable to inadequate cleaning each carries a cost that far exceeds any capital price differential between industrial and commodity equipment. The procurement decision is, in practice, a compliance risk decision.
Operational Benefits: Throughput, Consistency, and MRO Workshop Efficiency
The compliance case for industrial-grade equipment is clear; the operational return on that investment is equally tangible.
Cavitation acts simultaneously across every exposed surface, including internal passages that manual methods cannot reliably reach. For a component like a fuel nozzle, where carbon lacquer accumulates in precision orifices, a validated ultrasonic cycle replaces a manually intensive process with a controlled, timed cycle, delivering a more consistent and repeatable outcome across every batch.
Automated multi-line systems remove operator time from the cleaning sequence itself. Programmed lift-and-transfer platforms advance components through wash, rinse, and dry stages without manual handling at each transition. The operator loads the batch, initiates the programme, and can progress other work order tasks while the cycle runs. Cross-contamination risk between stages is also reduced, because chemistry carry-over is controlled by the transfer sequence rather than by individual handling practice.
Parameter control reduces rework at the systemic level. Under a manual process, a component that fails post-cleaning inspection is re-cleaned manually, compounding labour cost with no guarantee the second attempt differs meaningfully from the first. Under a validated ultrasonic process, a non-conforming output triggers a process investigation. The distinction matters for AS9100 corrective action: one addresses the system; the other addresses the symptom.
For defence maintenance organisations, surge demand is a recurring operational reality. Aircraft-on-ground events and scheduled deep maintenance inputs can spike component cleaning requirements sharply. A reproducible, scalable ultrasonic process absorbs that surge more predictably than manual cleaning, where throughput is directly constrained by available skilled technician time.
Remote monitoring on Kleentek’s PLC-equipped systems allows equipment performance issues to be diagnosed and resolved without waiting for on-site attendance. For New Zealand operators located at distance from major service centres, that capability directly reduces equipment downtime and protects schedule.
Specifying an Ultrasonic Cleaning System for a New Zealand MRO or Defence Facility
Translating those operational advantages into hardware begins with a structured specification process, not a catalogue selection.
Start with the component mix. The largest and heaviest components define minimum tank internal dimensions and basket load ratings. The most contamination-sensitive components, typically turbine blades and precision fuel nozzles, define rinse stage requirements and chemistry selection. The full material range across the component mix, nickel superalloys, titanium, aluminium alloys, and steel, sets the chemistry compatibility envelope that every approved cleaning agent must satisfy.
Tank configuration follows from that analysis. Aerospace MRO requires, at minimum, a heated ultrasonic wash tank, a heated ultrasonic or cascade rinse tank, and a drying stage. Wash tank filtration is not optional in this environment; it extends chemistry service life and prevents re-deposition of removed particulate onto cleaned surfaces. For turbine blade cleaning specifically, particulate re-deposition into cooling passages would recreate the original defect and invalidate the process.
Throughput drives the automation decision. Average components per shift and peak demand scenarios, such as aircraft-on-ground events, determine whether a manually operated or automated lift-and-transfer system is appropriate. At moderate to high throughput volumes, the capital cost difference between manual and automated configurations is typically recovered through labour savings and, critically, the consistency improvement that removes operator variability from the process equation.
PLC/HMI specification is compliance infrastructure. Named programme storage per component type, cycle logging with export capability, alarm and fault recording, and remote access for supplier diagnostics are the features an AS9100 auditor expects to find implemented. They are not enhancements to be value-engineered out.
Kleentek’s end-to-end scope, covering equipment design, chemistry supply, cleaning trials, commissioning, operator training, and ongoing support, maps directly to the AS9100 qualification and validation pathway. A single supplier accountable for both equipment and chemistry eliminates the documentation ambiguity that arises when process failures must be attributed to one or the other.
Conclusion: Building a Cleaning Process That Passes the Audit
Under AS9100 Rev D and NZCAA Part 145, component cleaning is a special process. It must be documented, validated, and parameter-controlled before any maintenance release is signed. Best-efforts manual cleaning, however thorough it appears, does not satisfy that obligation and will not withstand audit scrutiny.
Industrial ultrasonic cleaning equipment, specified with PLC/HMI controls, matched chemistry, and a multi-stage wash-rinse-dry configuration, provides the process control architecture both frameworks require. Parameters are defined, enforced, and logged automatically. Cycle records are exportable and traceable to individual components and work orders. The process is the same on the hundredth component as it was on the first.
The audit evidence package that transforms cleaning from a compliance liability into a compliance asset has three components: process validation records confirming the cycle achieves the required cleanliness outcome; equipment qualification records confirming the ultrasonic unit performs to its specified parameters; and chemistry qualification records confirming the cleaning agent is effective and compatible at the validated conditions. Together, these constitute objective evidence. Without them, an organisation is relying on assertion.
Equipment selection is a compliance decision before it is a capital one. Engaging Kleentek at the trial stage is the most efficient entry point. A cleaning trial using representative components, proposed chemistry, and the intended equipment configuration generates pre-validation data, confirms process feasibility, and identifies any parameter adjustments before formal qualification begins. It reduces risk on both the capital decision and the compliance pathway.
