How EDAS Works on the Boeing 787: Inside the Dreamliner's Hybrid Laminar Flow Control System

Most passengers boarding a Boeing 787 have never heard of EDAS (Empennage Door Actuation System), and there is no reason they should. The system sits quietly on the tail of the aircraft, doing its job without a single visible moving part during most of the flight. Yet the EDAS is one of the more inventive pieces of engineering Boeing built into the Dreamliner, a hybrid laminar flow control setup designed purely to save fuel by cutting drag.  It is worth noting up front that EDAS is not a Dreamliner-wide feature. Only the 787-9 and 787-10 carry it. The original 787-8 was never fitted with the system.

What EDAS Actually Does

EDAS works by managing airflow across the leading edges of the tail surfaces. Rather than letting air become turbulent as it passes over the vertical stabilizer, and on earlier aircraft the horizontal stabilizer too, the system keeps that airflow smooth, or laminar, for longer. Less turbulence means less drag, and less drag means less fuel burned. Boeing has estimated the gain at around 25,000 gallons of fuel per year per aircraft, a meaningful number once multiplied across a fleet flying long-haul routes for decades.

Within those two variants, aircraft built before production line number 526 carry the system on both the vertical and horizontal stabilizers. Later 787-9s and 787-10s only have it on the vertical stab, though the underlying principle is identical regardless of which surface it sits on.
 

Millions of Holes You Will Never See

The leading edges involved are covered in roughly 27 million tiny perforations, each about the width of a human hair. These holes connect through internal ducting to a set of door assemblies mounted on the horizontal stabilizer, positioned near the leading edge, at the base of the tail, and toward the inboard section on the underside where applicable. Electric motors drive these doors, and depending on the phase of flight, they open in one of two directions to either pull air in or push it out.

Purge Mode, Then Suction

The sequence starts on the takeoff roll. The larger doors swing open in the forward direction, and the system enters what is known as purge mode. Airflow pressurizes the ducting and forces air back out through the microscopic holes, clearing away any moisture or debris that might have collected inside. It is essentially a self-cleaning step built into every departure.

Once the aircraft accelerates past 190 knots, those doors close and a smaller door opens in the opposite, aft-facing direction. This switches the system into suction mode. Airflow now creates a vacuum inside the ducting, drawing outside air in through the same microscopic holes and pulling the boundary layer along with it. That suction is what maintains laminar flow across the tail surfaces for the rest of the cruise. On approach, once speed drops below 180 knots, the doors close entirely and sit flush with the skin of the aircraft until the next departure.

A System That Has Not Always Lived Up to the Pitch

EDAS is an elegant idea on paper, and it represented a genuine first when Boeing introduced it on the 787-9. In practice, some operators and maintenance crews have reported that the real-world fuel savings did not always match expectations once the added complexity and upkeep were factored in, and a number of airlines are understood to have deactivated the system on portions of their fleets over time. That does not take away from the engineering achievement itself. Few passengers glancing at a 787's tail would guess that a network of hair-width holes and motor-driven doors is quietly working to shave fuel burn on every long flight.

For an aircraft already built around composite materials and efficiency gains, EDAS is a reminder that some of the Dreamliner's most interesting technology is also its least visible.