Follow us on Twitter Follow us on FaceBook Kitplanes Videos Get RSS Feed

Builder Spotlight

June 2016 Issue

Build Your Own Stall-Warning Device

Certified aircraft have had them for decadesóbut not Experimentals.

If you’ve flown in a certified aircraft that was built within the last 50 years, it probably was equipped with a stall-warning device. However, there’s no requirement for stall warning systems in homebuilts. That doesn’t mean it’s not a good idea to have one. And fortunately, it’s easy to build your own.

The device shown in this article uses a microswitch and small tab to activate a warning horn about 5 knots before the stall. An adjustable mounting plate is used to attach the device to the leading edge and fine-tune the point where the warning horn sounds.

How It Works

As a wing moves forward, the air splits into two flows. One flow passes above the wing, while the other goes under. The point on the leading edge where the flow splits is called the cutoff point. This point isn’t fixed—it moves up or down according to the wing’s angle of attack.

During cruise and other maneuvers where there’s plenty of airspeed to prevent a stall, the tab on the leading edge remains in the airflow that goes under the wing, and the microswitch remains off. However, as angle of attack increases and airspeed decreases, the tab moves into the airflow moving above the wing. When the air pushes the tab up (typically about 5 knots above stall speed), it activates the microswitch and sounds the horn.

During normal cruise, the cutoff point is located at Point C.

As angle of attack increases and the wing stalls, the cutoff point moves to Point D.

Positioning the Tab and Mounting Plate

You will probably have to do some testing to correctly position the tab and mounting plate. As shown in the drawing below, the tab needs to be somewhere between Point C and D in level flight. If the tab is always above Point C, the horn will be constantly on. If the tab is always below Point D, the horn will never come on. To locate Point C:

• Place the fuselage reference in a horizontal position.
• Use a bubble level or place a plumb bob tangentially to the leading edge.
• The contact point will be Point C, which will be the upper limit position of the tab.

The microswitch is activated by a small metal tab that extends through a slot in the mounting plate. The plate attaches to the wing’s leading edge with screws.

Fine-Tuning the System

You can move the mounting plate up or down by adjusting the screws that attach the mounting plate to the leading edge. If the tab is too close to Point C, the horn will sound too early. And if the tab is too close to Point D, the horn will sound too late.

Schematic for the electrical circuit that activates the warning horn.

As you make your adjustments, don’t forget:

• If the warning is too early, move the plate down.
• If the warning is too late, move the plate up.

Stall Strips

In order to improve the stall characteristics of some airplanes, it may be necessary to add stall strips. These strips are typically placed on the inboard portion of the leading edge, close to the fuselage. The goal is for the strips to create turbulence, which causes the inboard portion of the wing to stall first. Meanwhile, air is still flowing smoothly over the outboard portion of the wing where the ailerons are located, providing lateral control at the beginning of the stall.

Stall strips can be made from wood and are typically triangular in shape measuring 8 inches long by .25 inches tall. The strips are positioned the same as the tab, i.e., between Points C and D. The exact position will be determined by successive tests.

The tab and mounting plate should be located between Points C and D.

Like the tab and mounting plate, stall strips are also located between Points C and D.


A stall warning device isn’t something you’re likely to use on every flight. But should you ever get distracted, it can be a very nice thing to have. If it only saves you once, it’s worth it.

Download File

Homebuilder's Portal by KITPLANES
Photo by Richard VanderMeulen
Phillabaum-HelicycleFirst flight of my Helicycle helicopter was on January 31, 2019 after two years of part-time building. Previously, before I retired, I built an RV-8 and a Zenith 750. The Helicycle was my first post- retirement project. I discovered I had more building time when I was working. Now trips, lake time, skiing, etc. interfere …
I always wanted something to do in retirement that that would be both challenging and fun. I couldn't envision myself playing golf only during the summer months so I decided to build and fly my own airplane. Looked around at all of the offerings from the kit manufacturers and finally decided on a Zenith CH …
Pappas Waiex B TurboThis is my second Waiex build. My first appeared in a Kitplanes article in 2007. This one took 24 months of part time work and uses the Aerovee Turbo and an all-Dynon avionics HDX panel. Thanks to my friends Randy Krueger for the Corvette Torch Red paint and James Butler, pilot and A&P mechanic extraordinaire …

lycoming-thunderbolt-o-360-redAt Sun 'n Fun 2018 we interviewed Jeff Schans, Lycoming's Sales manager and we asked about the popular Thunderbolt Engines. Watch the short Product Minute video as Jeff describes the benefits of the Thunderbolt product line and what it means for the aircraft homebuilder.
Dynon Avionics' latest-generation SkyView integrated avionics called the SkyView HDX has a newly designed bezel and user controls for easier use while flying in turbulence, plus brighter displays and a reworked touch interface. Larry Anglisano takes a product tour of the HDX with Dynon's Michael Schoefield in this video.
At Sun 'n Fun 2016, Dynon continued to push into the world of non-certified avionics with its SkyView SE, a less expensive version of its popular SkyView EFIS system. Paul Bertorelli prepared this video report.
The G5 is a self-contained electronic flight instrument, which can be interfaced with Garmin's G3X/Touch avionics and autopilot for backup and flight instrument redundancy. The GMA245 and remote GMA245R Bluetooth audio panels have advanced entertainment input functions and onscreen programming.
At Sun 'n Fun 2016, Just Aircraft is showing off its new Titan-powered SuperSTOL XL. Harrison Smith took Paul Bertorelli for a half-day demo flight in the new airplane, and here's his video report.
Kit manufacturer Zenith Aircraft Company has released a new 360-degree VR short video to showcase its kit aircraft and to promote the rewarding hobby of kit aircraft building and flying light-sport aircraft.
Video Archive


All mailed correspondence, including subscription invoices, renewals, and gift notices, will bear our address:
PO BOX 8535
Big Sandy, TX 75755

Third parties claiming to be selling KITPLANES subscriptions are not legitimate.