A cleaning company that arrives at a truck wash is working inside a process it already understands. A cleaning company that arrives at a small aircraft is working inside somebody else's maintenance system, and the person who puts that aircraft back into service did not choose the cleaning method. That single difference decides what to ask before a crew unrolls a hose. The questions that matter are not about the machine or the price. They are about getting the boundary of the job written down while the answers are still cheap to obtain.
Two habits run through the list below. First, every answer should come from a document or from a named person, not from the way the airframe looks under hangar lighting. A decal edge that looks firm today can lift after heat, and a seam that looks sealed may hide a gap behind the trim. Second, silence is not permission. Where the aircraft's own manual says nothing about a method, treat that method as unproven on this airframe and put it on a test list rather than into a work instruction. The questions are grouped by who can answer them and by what the answer changes in your written job instruction, because a question that changes nothing in the instruction is only conversation.
Ask the maintenance organisation what its own documents allow
Start with the paperwork that governs the aircraft, because it can end the job or narrow it before you describe any method. Ask which manual applies to this registration and what its cleaning section says about cleaning agents, about the method itself, and about where water must not be directed. Many manuals name a cleaning solution, describe a method, and warn against directing water at openings, instruments and control surfaces. If a method is written there, that sentence is the boundary of your work, and no equipment supplier's claim overrides it.
- Is there a work order or task card for the wash, and who signs it once the work is finished?
- Who will return this aircraft to service after cleaning, and what does that person need to see first?
- Does the operator keep a wash record your crew must complete, and in what format?
- If the manual is silent about heat or about steam, is a small test area acceptable, and who authorises it?
Ask for the wording rather than a verbal agreement. A quoted paragraph belongs in your work instruction and protects your crew in a way a phone call cannot. If nobody can produce the document, you are not dealing with a relaxed operator. You are dealing with an unanswered question that will end up being answered by your own test area and your own signature.
Ask what the surface is, and where its limits are written
An aircraft is not one surface. Metal skin in original paint, a workshop respray, fabric covering with its own coating system, composite cowlings, and a radome with a conductive coating all respond differently to heat, and the differences are not cosmetic. Ask which of these you will be cleaning, area by area, and ask for records rather than for history as remembered.
- Is the finish original or a later respray? If it was resprayed, ask the paint shop for the coating system, its published continuous temperature limit, and the primer and clear-coat details.
- Are there fabric-covered surfaces, and does the covering manufacturer's cleaning instruction differ from the aircraft manual?
- Which areas carry decals, registration numbers, stripes or printed labels, and are any of them already lifting at an edge?
- Where is bare or worn metal, where is chalky oxidised paint, and where has sealant gone hard or cracked?
- Have modifications or repairs added penetrations, such as avionics, antennas, additional lights, static ports, or repairs that required new holes? Each one is a path for water.
The comparison that decides your distance, your mode and your travel speed is the coating's published limit against the temperature that actually reaches the skin after the hose, the stand-off distance and the speed an operator can hold. It is not a figure printed on an equipment data sheet. Areas whose finish nobody can identify should be masked out of the first pass or tested on a small area, and anything already lifting, crazed or brittle belongs on a defect list before work starts, because heat reveals a failing finish rather than improving it.
Ask which openings must stay dry, and who checks them afterwards
On a fuselage the risky surfaces are rarely the flat panels. They are the details beside them, and most of those details are small enough to be missed by a crew that has only washed vehicles. Write the list before the job, area by area, so the crew works from a list instead of from memory.
- Static ports and probes, and the covers or plugs the operator uses to protect them.
- Drain holes, fuel vents, and avionics cooling inlets and outlets.
- Control-surface gaps, hinge lines, and trailing edges where water can sit.
- Cabin and baggage door seals, window edges, cowling fastener lines, and any trim that already lifts.
- Low points along the keel line and at the wing roots, where everything that ran down finally collects.
Then ask the question most cleaning companies overlook: who confirms, after your crew has finished, that no water has entered the structure, and at which point in the process? The person who returns the aircraft to service carries that judgement, so it should be arranged before the work is booked rather than at hangar closing time with the airframe still cold and damp. Ask whether the manual requires drain holes to be confirmed clear in the areas you intend to wash, and who performs that check. Ask what a dry aircraft means for this operator: a waiting time, a visual condition, or a signature.
Steam condenses on any surface colder than the vapour, so the wetted area is always larger than the area you aimed at, and gaps hold water far longer than panels do. If the aircraft will go outside into falling temperatures, add one question to your walk-through: what water is still sitting in a gap, a seam, a drain hole or a control surface when the temperature drops below freezing?
Ask where the run-off goes and who owns that decision
Water is the part of the job an airport will hold you to, and it is almost never the equipment supplier's decision to make. Ask the facility contact or the operator's environmental contact where wash water may go, and ask for the rule in writing.
- Is washing allowed inside the hangar, on the apron, or only at a designated wash point?
- Is there a floor drain where you intend to work, and may it receive water carrying fuel, oil and detergent residue?
- Does the airport authority or a local drainage body require an oil-water separator, a containment mat, or collection and disposal off site?
- Where is the nearest water tap, and how far from it can the machine actually stand while working?
- What air movement exists in a closed hangar while steam is being generated, and is there low-angle light for the final inspection?
A method that produces little run-off is a genuine advantage in these rooms, and it is one reason operators begin by asking about low-water steam cleaning equipment. It is not an answer to the drainage question. Low run-off still leaves water on the floor and in the gaps, and part of the moisture in a hangar is generated by the room itself when warm vapour meets cold skin. Whoever owns the drainage rule also owns the question of whether your method is permitted at all, so get that answer before you price the work, not after the machine is standing on the apron.
Ask what the site can support, and measure reach before you quote
A fixed machine works from one point while the work reaches away from it, so the position is the decision rather than the machine. Mark where the crew will stand and where the unit will stand, then take a tape measure to the farthest surface you are expected to clean: the top of the opposite side, the keel line, the tail cone. Reach belongs to the position, and a floor plan will not tell you what the tape says. The top of a fuselage is usually the surface that fails this test, so decide now whether the answer is a platform, a second working position, a longer extension, or a smaller scope. Leaning on thin panels to gain a metre leaves dents that belong in the record alongside the cleaning result.
- Power: what supply exists at that position, and whose electrician confirms the circuit? A machine rated 6 kW at 220 V is a continuous heat load, and whether the building circuit supports it is your site's question, not the manufacturer's.
- Water: how far the machine may stand from the tap, and whether the inlet fitting supplied matches the site. The fixed unit in the PowerDe cleaning equipment range takes a tap-water inlet with a 1/2 inch internal-thread joint, which is a detail to confirm rather than assume.
- Drainage: where run-off goes from that exact position, and whether it passes through a separator on the way.
- Access: door widths, the taxi route, and the published overall size including handles, 1,200 x 800 x 1,200 mm, checked against the doors and lift you actually have, plus clearance to open the tank and reach the drain valve.
Ask your supplier in writing for the figures a listing does not publish: hose and lance lengths, warm-up time, how long one tank of 80 L delivers steam, how quickly the machine recovers after refilling, and water use per hour. Those numbers are what turn a measured reach and a real work window into an honest price. The protections a listing names, such as leakage, short-circuit, high-temperature, high-voltage, water-shortage and high-voltage explosion protection, guard the machine. They do not judge your circuit, they do not see a wet floor, and they do not stand between the operator and a hot nozzle.
Ask what clean means to the person who signs
Work on an aircraft is accepted by someone who inspects for a living, so ask for the acceptance wording in that person's own terms before the work starts, and put it into the job instruction where the crew can read it.
- No lifting at decal or registration edges when seen under low-angle light.
- No blistering or softening at chipped bare-metal edges.
- No visible gloss difference, from the same viewing angle, against an area you deliberately left untreated.
- No change at sealant surfaces, window edges or matte finishes.
- No standing water in gaps, hinge lines or under trim at handover.
Photograph fixed reference points from the same angle before you begin, and mark stubborn areas with tape so that both sides look at the same place. Then agree what happens to the defects cleaning cannot remove: paint that is already lifting, crazed windows, hardened sealant, loose fastener heads. Handing over a short defect list is part of a professional cleaning job, because heat shows up a finish that is failing rather than repairing it, and an inspector would rather hear it from you than discover it later. Agree the second check as well. Lifted decal edges, water marks and flash rust on bare metal often appear hours later or the next morning, so schedule that check with a name and a time, or it will not happen.
Ask the questions that can stop the job, and treat silence as a test item
Three answers, or the absence of them, decide whether a careful contractor books the work at all.
- Nobody can tell you what the surface is, or what its published limit is.
- Nobody can tell you where the water is allowed to go.
- Nobody will say who confirms that the aircraft is dry and inspected before it returns to service.
If any of those stays open, the honest output is neither a refusal nor a guess. It is a small test: three areas chosen on purpose, being the dirtiest lower skin, a decal or registration area, and an area of a different material, with half of each treated and half left as an untouched control, checked the same day and again the next morning against pass wording written before the first pass. That test costs a short visit and answers questions no brochure can answer.
Put the same discipline to your equipment supplier, in writing. The listing for the fixed unit in the range describes vehicle exteriors at gas stations and parking lots, interior vacuuming and disinfection, and engine compartments. It does not describe aircraft, so ask for written confirmation of suitability for aircraft surfaces and for the assumptions behind that answer. Ask whether the published 160 degrees Celsius and 0.8 MPa are measured at the generator or at the nozzle, since those two figures describe one saturated condition, and the value that reaches the skin after a long hose is a different number. Ask what the listing leaves out about water use, and treat any claim about a particular paint system as a question for the paint shop rather than for the machine.
Whether the job needs a fixed unit, a hand-pushed unit or a driving machine follows from the answers above rather than from a catalogue. If the hangar cannot support a fixed point, ask about customized steam cleaning equipment and the mobile options in the same range before you commit a crew to a position the building cannot serve. Comparing small aircraft fuselage cleaning equipment is a useful exercise, but only after the reach, drainage and responsibility questions have written answers.
Send back one page, not a confirmation email
The output of all these questions is a single page your crew can follow without you and the client can agree to. Keep it short and specific.
- What the aircraft's own documents permit, forbid, and do not cover, with the source quoted for each line.
- The surface list by area, with where each answer came from.
- The masking list, with the person who will fit each cover or plug.
- The water route, with the person who owns that decision.
- Power, water, drainage and ventilation answers, each with a name and a date.
- The measured reach from the marked position, and the scope that falls outside it.
- Which steam mode is used on which areas, and the reason.
- The acceptance wording, the reference photographs, and the format of the defect list.
- Three names: who cleans, who checks, and who returns the aircraft to service.
A page like this is the cheapest document in the job. It stops a crew from inventing answers when the person who asked the questions is not standing in the hangar, and it turns a price into a scope. Send it to the client for agreement before the crew arrives, and send the same page, as a record rather than a summary, to your equipment supplier with the open items marked; you can send it through the contact PowerDe page. Suppliers answer records and market to summaries, and that difference is where most aircraft cleaning jobs begin to go wrong.
A service provider who asks these questions before the first pass is not being slow. On an aircraft, the cleaning result and the maintenance result are examined by the same person, and these questions are how a cleaning company keeps the two from being confused.
