Compressor for aerospace, aircraft maintenance and subcontracting

An aircraft maintenance workshop or a medium-sized aerospace subcontractor usually needs 1 to 2 m³/min of dry, filtered air at 7 to 8 bar. An 11 kW 4-in-1 screw compressor such as the K 110, which delivers 1.7 m³/min (about 60 CFM) at 8 bar with a built-in dryer and filtration, covers a workshop where four people are drilling, riveting, sanding and painting at the same time. A flying club hangar often manages with a K 75 at 1.1 m³/min, while a subcontracting line running several shifts moves up to the S 220 PM, with a second compressor as backup.

What is compressed air used for in an aerospace workshop?

Aerospace uses compressed air at almost every stage, from making parts to maintaining them:

• Structural assembly: angle and straight air drills, rivet guns, blind rivet tools, deburring tools, screwdrivers and assembly tooling.
• Composites: orbital and angle sanders for preparing laminates, trimming, and repairs to panels and fairings.
• Painting and surface preparation: primer and topcoat spray guns, blowing down before painting, bead blasting and gentle paint stripping in a booth.
• Machining subcontractors: machining centres, sheet metal work, presses, surface treatment lines where air operates the valves and agitates the tanks.
• Line and hangar maintenance: tyre inflation, blowing down, dismantling tools, test benches.

One compressor therefore supplies very different tools, with two requirements in common: a flow rate that holds up when several stations are working at once, and air whose quality is known and documented.

How much air do the tools in an aerospace workshop use?

The figures below are indicative only, for a working pressure of around 6.3 bar. The exact consumption is in each tool's manual.

What weighs heavily is the tools that run continuously: the sander, the spray gun and the bead blaster. Drills and rivet guns use a lot of air, but in bursts, and the air receiver smooths out those demands. The detail tool by tool is in our article on air consumption of rivet guns and air drills.

How do you size the compressor for a maintenance workshop?

Take a maintenance workshop with four technicians working at the same time: one sanding a composite repair, one painting in the booth, and two drilling and riveting on a structure.

1. Sander: 350 l/min, continuous, counted in full.
2. Spray gun: 350 l/min, continuous, counted in full.
3. Two drills: 2 × 400 l/min, but in bursts. The air receiver absorbs the peaks, so they count at half: 400 l/min.
4. Subtotal: 350 + 350 + 400 = 1,100 l/min.
5. 25% safety margin for leaks and tool wear: 1,100 × 1.25 = 1,375 l/min.
6. 20% expansion margin for one more station: 1,375 × 1.2 = 1,650 l/min, or 1.65 m³/min.

These are the margins our configurator applies. The result points to the K 110, at 1.7 m³/min at 8 bar. Our flow and pressure converter turns the CFM figures in tool manuals into l/min.

Which compressor should an aerospace workshop choose?

• Flying club hangar, small maintenance workshop: the K 75, a 7.5 kW 4-in-1 screw compressor, delivers 1.1 m³/min at 8 bar. Compressor, 420 L air receiver, refrigerated dryer and filtration share one frame, so the air reaches the workshop dry with no system to design. If all you do is inflate tyres, blow down and drill a few holes, the S 55 at 0.6 m³/min is enough, with a separate receiver and dryer.
• Maintenance workshop with 3 to 5 technicians, single-shift subcontractor: the K 110 at 1.7 m³/min, or the K 150 at 2.2 m³/min if a spray booth and sanding run all day.
• Subcontractor on two or three shifts, machining and assembly: the S 220 PM, with its permanent magnet motor, delivers 3.6 m³/min at 8 bar. Beyond that, the S series goes up to 132 kW on quotation: see our industrial compressors from 30 to 132 kW.

The S and K series are variable speed. In a workshop where someone drills for a minute, sands for ten, then stops to inspect, demand changes all the time: the compressor follows it instead of switching between load and idle. The detailed choice by workshop size is in our article which compressor for an aircraft maintenance workshop.

What air quality do aerospace customers require?

In aerospace, air quality is not a matter of convenience. A drop of water or a film of oil under a coat of paint means an adhesion defect that can show up months later. On a composite, a contaminated surface compromises a bond or a repair. That is why prime contractors' specifications and product data sheets increasingly set an air quality class to ISO 8573-1.

The class is written as three digits: particles, water, oil. For water, class 4 corresponds to a pressure dew point of +3 °C, which a refrigerated dryer achieves; class 2 corresponds to -40 °C, which a desiccant dryer achieves. For oil, class 1 limits the content to 0.01 mg/m³.

Our screw compressors are oil-lubricated. Carried-over oil is captured by the filtration at the outlet, and for painting or surface preparation air you add fine filters and an activated carbon filter at the point of use. The class to achieve is defined with our technicians, based on your specification. See our guide to ISO 8573-1 air quality and the article on dry, clean air for aerospace painting.

How should you handle composite sanding?

Sanding carbon and glass fibre laminates produces a fine, irritating dust which, in the case of carbon, conducts electricity. Two rules: work with dust-extracting sanders connected to a dust extractor, and keep that dust away from the compressor. An air intake that draws in carbon dust clogs the intake filter and can reach electrical components. Sander consumption and how to organise dust extraction are covered in our article on sanding composites with compressed air.

How do you keep the air on at a subcontractor?

For a subcontractor, losing air means a late delivery and a non-conformance to explain. Two compressors taking turns are better than one bigger unit: if one is being serviced, the other keeps production going. Compressor hire from 5.5 to 132 kW can cover a breakdown or a peak in workload. For a customer audit, keep a maintenance log and dew point records. Our technicians can carry out a compressed air audit of your installation. See our article on keeping compressed air on at an aerospace subcontractor.

Installation and maintenance

• The room. Separate from the sanding area and the spray booth, ventilated, with a clean air intake. See our article on the compressor room.
• Condensate. An automatic condensate drain on the receiver and at the low points. This condensate contains oil: it must be collected and treated.
• Servicing. First service at 500 hours, then every 1,500 hours. Keep a service kit in stock and record every intervention: that is the basis of traceability. Compressors carry a 2-year warranty and parts remain available for 15 years.

To size your installation, start with the configurator, or send us the list of your tools and your customers' specifications with a quote request.

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