The week before an annual, a lot of owners do the same thing: roll the airplane out, pull the cowling, and look at a year’s worth of grime. Oil film on the engine case and accessories, a gray-black coat of exhaust soot along the belly, maybe some hydraulic fluid around the brakes or gear. None of it is unusual, but all of it gets in the way.
An inspector can’t evaluate what they can’t see. A crack, a chafed line, or a slow weep is easier to find on clean surfaces, and many shops would rather spend inspection hours inspecting than degreasing. On an owner-assisted annual, cleaning is often one of the jobs the owner is asked to take on.
A bigger bottle of a cleaner made for exactly this kind of buildup makes that prep day go faster, with enough left over for post-flight touch-ups the rest of the year.
Quick answer: Aero Cosmetics Belly Soap 32 fl. oz. is a heavy-duty spray-on, wipe-dry cleaner for aircraft bellies and engine areas coated with dried or baked-on hydraulic fluids and oils. It removes grease, oil, hydraulic fluid, and exhaust soot, is safe on wet or dry surfaces, and meets the Exterior BSS7432 specification. Aero Cosmetics part number: 789Q. Available on Skyfarer and at Skyfarer Shop.
What Belly Soap is made for
- Baked-on contamination. Dried or baked-on hydraulic fluids and oils on bellies and engine areas.
- Grease, oil, hydraulic fluid, and exhaust soot. The common contaminants on the underside of a piston airplane.
- Spray on, wipe dry. Simple application, safe on wet or dry surfaces.
- Exterior BSS7432. Aero Cosmetics lists it as meeting this exterior specification.
Prepping for an inspection
- Ask your shop first. Some inspectors want to see the engine before it’s cleaned, so they can spot where leaks are coming from. Check before you degrease.
- Work on a cool engine. Let the engine and exhaust cool completely.
- Spray and agitate. Apply Belly Soap to the dirty areas. For the toughest buildup, Aero Cosmetics recommends pairing it with the Aero Scrubber.
- Wipe dry. Use towels set aside for greasy work, such as Aero Towels On A Roll.
Pilot tip: On an owner-assisted annual, do only the jobs your A&P or IA asks you to do. Stick to cleaning, don’t disturb wiring, lines, or fittings, and tell your mechanic about anything you noticed while you were in there.
Choosing a size
- 16 fl. oz. For occasional post-flight touch-ups.
- 32 fl. oz. For owners who clean regularly or handle prep before inspections.
- 5 gallon For busy hangars, clubs, and small shops.
- 55 gallon For fleets, FBOs, and maintenance operations.
Where to buy
Aero Cosmetics Belly Soap 32 fl. oz. is sold by Skyfarer Shop. Find it on the Skyfarer marketplace or order directly from Skyfarer Shop. Either link shows the current price. In-stock items ship in 1–3 business days with tracking, U.S. orders over $70 ship free, and most items can be returned within 30 days of delivery.
Frequently asked questions
What does Belly Soap remove?
Grease, oil, hydraulic fluid, and exhaust soot, including dried or baked-on hydraulic fluids and oils on aircraft bellies and engine areas.
Does it need to be rinsed?
It’s a spray-on, wipe-dry cleaner, and it’s safe on wet or dry surfaces.
Is it only for aircraft?
No. Aero Cosmetics also lists it for RVs, cars, boats, and motorcycles.
What’s the part number?
789Q for the 32 fl. oz. size.
