What Am I? Tail Strakes

Adding stability and controllability

January 1, 2019 By Alyssa J. Cobb

The AOPA Sweepstakes Super Cub, a 1954 model, features the CubCrafters Vortex Generator Kit with tail strakes.

Take a look at an older-model backcountry airplane such as a Piper Super Cub or a Cessna 180, and you might notice something peculiar: a thin piece of metal mounted on each side of the fuselage in front of the horizontal stabilizer.

The tail strake looks like a little fin and was developed in the 1990s as a modification for backcountry airplanes. It is one part of a kit that includes vortex generators. (The tail strake is mounted horizontally on the rear fuselage, while the vortex generators are mounted vertically on top the thickest part of the wings.) Think of the tail strake and vortex generators “like mini wing tips,” said CubCrafters President Pat Horgan, whose company sells the kits. These mini wing tips create vortices and reenergize the air flowing over the surface of the wing and horizontal stabilizer; this keeps the air attached longer to those surfaces.

The kit can improve controllability at slow speeds and reduce stall speeds on aircraft that are rigged properly and operated within their limitations. That’s why the modifications are predominantly seen on aircraft that fly in the backcountry, where they need to fly at slower approach speeds to get into and out of short, remote airstrips.

New backcountry airplanes have been designed so that they no longer need a tail strake. Vortex generators, however, continue to be a common modification on many aircraft. You might even find them on top of the wings of your trainer.

Spoiler alert

Rotor talk

On some helicopters, running the length of thetail boom are L-shaped (or something similar) brackets that protrude about an inch. These are known astail boom strakes and they act like spoilers. Because thetail boom is underneath the rotor system, at a hover, very low airspeeds, or sideways flight, rotor downwash passes around the boom.

Like an airfoil, this produces high- and low-air-pressure areas that exert a force along thetail boom. This force decreases thetail rotor’s capability during hover and slow flight. At higher speeds the downwash moves to the rear and passes above thetail boom.

Strakes control the airflow around thetail boom, thus increasing thetail rotor’s efficiency and decreasing the turbulent air, which improves yaw control.

During the late 1980s, NASA and the U.S. Army performed wind tunnel and flight tests to analyze the performance gain from adding atail boom strake. The tests were performed using a Bell 204B helicopter. Published in 1993, NASA Technical Report 3278 stated a 5-percent improvement in pedal control margin will provide an additional 2,000 feet of altitude capability or 500 pounds of payload.

The report concluded that the strake improves handling qualities, reducestail boom fatigue, improves climb and cruise performance, and increases yaw control safety margins for all single-rotor helicopters with enclosedtail booms.—Tim McAdams

Tecnam P2010

Spin-resistant carbon-fiber fuselages provide little of the drag needed to help stop a spin, so the Tecnam P2010 has a strake on the bottom of the tail and vortex generators on the vertical stabilizer as part of the spin-resistance design. You can’t fly if more than three vortex generators in a row are missing from the vertical stabilizer.—AJC

Alyssa J. Cobb

The former senior director of digital media, Alyssa J. Cobb was on the AOPA staff from 2004 until 2023. She is a flight instructor, and loves flying her Cessna 170B with her husband and two children. Alyssa also hosts the weekly Fly with AOPA show on the AOPA Pilot Video YouTube channel.

Go to Alyssa J. Cobb's Profile