Exterior Dry Wash at Sion (LSGS)

Why does an Alpine valley airport need a dry-wash service?

Sion sits at 1,582 feet in the Rhône Valley, a natural funnel that channels weather, dust and insect activity between the peaks. Aircraft arrive from lower, warmer altitudes and collect bug strikes on the climb; they depart into cold air that accelerates ice adhesion on any residue left on leading edges or nacelles. Exhaust soot bakes onto belly panels during the descent, and hydraulic mist from gear retraction settles into seams. Left untreated, that film traps moisture against paint and brightwork, accelerating corrosion in the temperature swings typical of mountain flying.

A dry wash clears the contamination without requiring a wash bay—important here, because the aerodrome has no dedicated wash pad and water use on the apron is constrained by valley environmental rules. The process uses encapsulating chemistry that lifts soil into suspension, then wipes clean with microfibre, leaving no runoff and no standing water that might freeze on cold mornings. For operators running frequent rotations into Crans-Montana or Verbier, it keeps the aircraft presentable between deeper cleans at a home base equipped for wet work.

What changes at Sion that affects the wash schedule?

The aerodrome operates from the start of daylight to a maximum of 18:00 Zulu in summer (April through September) and 19:00 Zulu in winter (October through March), with administration hours starting at 05:00 Zulu in the warm months and 07:00 Zulu when days shorten. Signature Flight Support and Alpinejet Handling staff their terminals from 07:00 to 20:00 local in summer; in winter, hours compress to 08:00 until nightfall. Any movement outside those windows requires prior permission and puts services onto an on-request basis—practical translation: if you want a wash before departure, the aircraft needs to arrive during daylight with enough margin for the work.

Runway 07/25 runs 2,000 metres; a parallel 660-metre grass strip exists but is irrelevant to business jets. The single paved runway and IGS/RNP instrument approaches mean slots are not coordinated, but winter weather and the daylight-only curfew create natural pinch points in the schedule. Peak season is December through March, when the Valais resorts fill and ramp space tightens. Both FBOs offer hangar storage—Signature's facility handles aircraft to 77,000 kilograms, useful if you want the wash done inside, sheltered from wind or snow. Customs and immigration are on site during administration hours; airside access is controlled and requires an escort if your crew lacks an airport ID card.

Sion is 2.5 kilometres from the city centre, close enough that ground transport for passengers adds no meaningful time to a turnaround. For the detailing crew, that proximity means we can pre-position at the FBO and start work as soon as the GPU is connected and the engines cool, maximising the usable daylight window.

How does a waterless wash work on a cold-soaked airframe?

Cold-soaked aluminium and composite panels present no barrier to dry-wash chemistry; the surfactants in the product are formulated to work across a wide temperature range, and the mechanical action of the microfibre does the heavy lifting. We avoid washing an airframe still radiating heat from a recent descent—freshly landed nacelles and belly panels can flash-dry the product before we wipe, leaving streaks—but once the surface temperature stabilises, cold or warm, the process is identical.

What does change in winter is the working environment. Wind in the Rhône Valley can gust hard enough to blow spray and disturb the wipe pattern, so if conditions are difficult we move the aircraft into one of the hangars available at both FBOs. Inside, we have stable temperature, no precipitation and full lighting, which speeds the work and improves the result. The trade-off is co-ordination: hangar space during ski season is in demand, so if you want the wash done under cover, mention it when you file the PPR.

What does the dry wash include, and what does it leave for later?

We clean the entire exterior envelope: fuselage from nose to tail, wings upper and lower, empennage, nacelles, belly and gear doors. Bug residue comes off leading edges and windscreens; exhaust carbon lifts from the nacelle trailing edges and belly aft of the APU. Hydraulic film around actuator fairings and gear bays is degreased with a separate cleaner safe for seals and paint. Exterior windows, position lights and landing lights are polished clear. Brightwork—leading-edge strips, nacelle lips—gets a light touch-up to remove oxidation film, though this is not a full metal polish.

The wash does not include a sealant or wax coat; it removes soil but adds no protection. It does not address deep staining, corrosion bloom or paint defects—those need a wet wash, clay bar or compound, none of which we perform on the ramp. It does not touch the flight deck or cabin; it is an exterior-only service. If the aircraft is heavily soiled—trans-Atlantic with two weeks of ramp grime, or post-deicing with Type IV residue baked on—we will tell you during the walk-around; sometimes a dry wash is not enough, and pushing it results in streaks and wasted time.

How do you schedule a wash between ski-shuttle legs?

Most operators flying into Sion are running shuttles: drop principals at the resort, reposition empty to Geneva or Zurich, return two days later, repeat. The wash fits best on the outbound leg—aircraft arrives from the UK or Germany, passengers deplane, we wash while the crew files for the reposition and the handler refuels. Three to four hours covers a super-midsize; larger aircraft take longer, but if you have a six-hour gap before the next leg, we will finish. Alternatively, we wash overnight if the aircraft remains on stand and the FBO can provide ramp lighting and airside escort after administration hours close.

For aircraft staying at Sion—some operators hangar here for the season—we schedule washes every two to four weeks depending on utilisation. A jet flying daily accumulates enough exhaust and dust to justify a fortnightly clean; one flying twice a week can stretch to a month. We track the schedule with the chief pilot or handler, and we will prompt you if the interval is slipping. Recurring work at a single base is simpler for everyone: we know the aircraft, we know the FBO, we know the crew's timing, and the result is consistent.

Why not wait and wash the aircraft at the home base?

You can, and if the home base has a heated wash bay and a maintenance slot already booked, that may be the better choice. But waiting has costs. Bug residue and exhaust carbon harden with time and temperature cycling; what wipes off easily on day one requires compound and elbow work on day fourteen. Hydraulic fluid seeps into paint seams and softens the bond between base coat and clear coat. Leading-edge tape collects grit that acts as an abrasive against the tape itself, shortening its life. Every flight between Sion and home adds another layer of soil, and every night on a cold ramp lets moisture condense under that soil, against the aluminium.

A dry wash at Sion stops the clock. It does not replace the deeper detailing work you will do at home—it is not a polish, not a decon, not a sealant application—but it removes the active contamination that does harm while the aircraft is in service. For a charter operator running a tight schedule, it also means the aircraft presents well when it collects the next client, which matters in a market where appearance drives repeat bookings. The cost of the wash is a fraction of the cost of repainting a nacelle or replacing leading-edge tape early.