Anti-skid coating on 737 wing


Well-Known Member
While flying on a USAirways 737-400 last weekend, I noticed that the wing area near the emergency exits was coated with an anti-skid coating, and the surface appeared very rough. Does this not disrupt the flow of the air over that section of the wing, much like frost or ice? I can understand the need for passenger safety in an emergency, so is the effect on the wing that negligible?
Doesn't parasite drag decrease with altitude? At around 300 kts, I'm assuming you would be fairly high up.
Induced drag decreases with airspeed, form and parasitic drag increase with airspeed.

The coating is probably so far aft on the wing and close to the fuselsausage that its effect is negligible. Sometimes a rough surface downstream of the transition from laminar flow can be beneficial by energizing the boundary layer from the free stream (similar function to vortillons).

Sharks have been imparted with this gift of textured skin too. On them, their skin has small ridges (like couderoy). 3M was working on a skin surface for Airbus a while back that had similar textures. Last I heard, they were experimenting with different ridge spacing and heights, but it was really expensive stuff ... like a hundred bucks a square foot. An A320's wing area is around 1300 ft², so it better offer big savings.

The ridges are called "riblets" is they're prependicular to the flow, "rivulets" if they're parallel, and they both make a swhooshing sound as the airplane taxis around the airport.

Up next, "speed holes"...

That "anti-skid" coating that you observed is actually utilized for the airlines de-icing procedures. Under certain situations, one of the cockpit crewmembers may be required to visually observe a section of the wing to inspect for ice contamination. The "rough-smooth-rough" strips that you noticed enable the pilot to determine if ice remains on that section of the wing from his vantage point inside the cabin.

Clear ice can be very difficult to discern from the grey, smooth section of the wing. The strips aid in the visual determination.

Hope that helps.

(BTW, the laminar flow boundary is so disturbed at that section of the wing that is provides almost no the placement of the "strips" at that location has a neglible affect on lift or drag.)
MD88Pilot would know!

He's the guy who gave me my Beech 1900 type ride!
Hi Doug,

I've been enjoying your website, lately. Not doing much flying on reserve....gotta do something!