How Does It Work

        What is AOA?

The Angle of Attack (AOA) is defined as the angle at which relative wind meets an airfoil or the cord of the wing to the flight path. Every aircraft has a defined range of AOA, from Cruise to Stall (Critical Alpha Angle) or CAA. Too high of an AOA results in a loss of lift and can cause an aircraft to Stall the wing. A fixed wing aircraft will always Stall at the same CAA regardless of airspeed, CG, weight changes, G loading, bank angle or altitude density.

        How the Probe works.

Our AOA probe instantaneously measures differential ram air pressure across two ports at the bottom of the probe. This is very similar to a vane or wing AOA system, except we have no moving parts. So nothing that will wear out over time. This differential pressure reading is then directly correlated to your aircraft's specific angle of attack, or coefficient of lift, through our three point calibration procedure. And just like angle of attack, no matter your altitude, attitude, speed or weight – you will always stall at the same angle of attack and the same differential pressure reading on our probe. The probe is not measuring air speed, which is a common misconception.

        What if my aircraft is pressurized?

No problem. We sell pressurized units of all our AOA systems. For pricing and install information, please contact us at 763-506-9990 or

        Is there any difference between your AOA systems?

Being that no two pilots are alike, we have created a variety of systems to accommodate each pilot specifically. That being said, we have single systems, dual systems, pressurized systems, and even dual pressurized systems. Please contact Alpha Systems for more information.

        How do I calibrate?

Calibration of the Alpha Systems AOA is easy, intuitive and all by the push of a button. Highly identifiable illuminated LED segments stay in your peripheral vision to identify your entire Angle of Attack range.
Three simple set points: 1)Zero-Offset Calibration (ground calibration), 2)Optimum Alpha Angle (OAA), 1.3 Vs for that flight, 3)Cruise, The aircraft is calibrated at a maneuvering speed (alpha). This set-point allows the system to display a range of LED segments from Cruise (green) to OAA (1.3Vs, blue) and up to Stall (1.0Vs, red), or Critical Alpha, 4)Stall (Optional). A pilot will fly accurate V speeds and input those Angle of Attack values for the entire Alpha range of the aircraft. See our quick calibration guides for Eagle, Falcon,,and Merlin.

        Why should I calibrate with Flaps Up or Clean?

  • If you calibrate our AOA system “clean” (flaps up), when flying with flaps down the indicated AOA (or lift reserve) is less than the actual lift you are generating.

  • If you calibrate our AOA system “dirty” (flaps down), when flying with flaps up the indicated AOA (or lift reserve) is more than the actual lift you are generating. (Alpha Systems AOA by DepotStar, Inc. finds this situation to be DANGEROUS and therefore we strongly urge our customers to calibrate “clean”).

        Can the Alpha Systems AOA integrate with other aircraft components?

We do not, at this time, integrate with any other aircraft components. And while it is possible, the reason we currently do not is that our minor alteration status with the FAA states that we are a stand alone advisory system, and to keep this status we must not integrate with any other aircraft components.

        Flap Input?

Yes! The I/O module expands the Alpha Systems with the capabilities of up to four flap inputs; analog flap input, gear advisory, master brightness control, squat switch, and other inputs and outputs allowing the expansion for the future upgrades with this system. The I/O module is plug and play with a required software upgrade to the display module. For more information click here.

        How often should the AOA be calibrated after the initial calibration process?

We recommend to calibrate at least once a year to verify the performance and accuracy and re-calibrate as necessary. It's easy to check calibration simply by flying a known Alpha Angle (OAA) and verifying that the display gives you the correct information.

        What are your cases made from?

Our cases are made from cast aluminum.

Display Options

        Why all the different AOA displays to choose from?

Because no two pilots are ever alike, we believe you should never be stuck with just one AOA display option from which to choose.

        Which AOA display would you recommend?

As far as which of our AOA systems we would recommend, it depends on how you want your Angle of Attack to be displayed. Our new flock of AOA’s are each pilot specific to their personal preference. Some pilots, such as ex-Military, are used to flying the doughnut or a chevron style, other pilots, such as the steam gauge guys, are used to the needle movement, where others simply like the bar graph style. In the end, it is what you relate to. Our top sellers are the Eagle and Falcon displays with the Valkyrie HUD (heads up display). We strongly suggest the display be mounted in your peripheral vision and the Valkyrie HUD takes any of our new 2 ¼” displays and reflects the display image into the heads up glass that is sure to impress.

        Do your displays have programmable LED brightness levels?

Yes, all of our AOA displays have 16 different LED brightness levels to choose from, which are programmed at the display by you. The brightness button, when depressed repeatedly, will increase the light level through 16 steps until its maximum then drops to the minimum level and steps up each time the button is depressed. Another feature the displays have is an imbedded photocell diode. The Photocell will automatically adjust LED intensity by sampling ambient cockpit light levels and switch between two preset brightness levels. Each display has a different number of highly visible, colored LED segments that will illuminate to indicate the available Lift throughout the AOA range of an aircraft, once calibrated. When you turn the system off, it will go back to your programmed brightness settings.

        What if I want my display to indicate my AOA one LED at a time, instead?

Our Falcon, and Merlin displays come with three different display output options, choice of which is programmed by you. So yes, you can have just one LED on. Then when in the red, all the LEDs stack up. Click here to view videos of the different Falcon segment options.

        What if I want two AOA displays?

No problem, we offer dual display options for our AOA systems. For pricing and install information, please contact us at 763-506-9990 or

AOA Miscellaneous

        The cables that came in my kit are too short.

No problem! The 6ft cables fit 99% of the aircraft out there. We can custom build extra cables in house for an additional $75.00/each upon request, plus shipping & handling charges. For more information go here.

        What is the Alpha Systems AOA Warranty?

One year from date of purchase to the original owner under our Warranty Registration policy; and we stand behind our product with a 100% satisfaction guarantee.View Warranty

        What can I find on your website

Here you will find installation documents, pictures of installs, AOA product videos, videos of our AOAs in flight, information about our AOA Systems, and articles about Angle of Attack.

        Where is Alpha Systems manufactured?

All the software, mechanical/electrical design, and cable builds are done in house at DepotStar Inc. located in Ramsey, Minnesota.

        What types of aircrafts are Alpha Systems AOAs currently installed in?

View a full list here.

        Will vortex Generators negatively affect the performance of the AOA?

There should be no negative affect with Vortex Generators; however, the customer should always calibrate after the VG's are installed to guarantee accuracy.

        Is there any magnetic interferences when you place the AOA display next to a compass?

Our product has been tested on numerous airplanes directly next to a compass; however, due to the vast number of manufacturers of those compasses, we always recommend verification of non-interferences by the installer. See video.

        What's the difference between the heated and non-heated probe?

There is no difference between performance, reliability or accuracy. The heated option allows for the temperature to keep the probe from freezing until out of ice.

        Is your heated probe certified?

It is not certified known ice; however, it has been tested in known ice conditions by major aircraft manufacturers and passed their flight tests.

        Is your heated probe polarity sensitive?

No, it is not polarity sensitive.

Technical Specifications

        Spec Sheet

Complete kit weight is less than 3 lbs

Complete Kit Weight Less than 3.00 lbs
AOA Interface Module size In Inches: 5.75 x 2.60 x 1.65
System Voltage Requirements 12 - 28 Volts DC
System max Power Draw 0.250 Amps
System Power Cable 6 ft, three wires: power, ground and shield
Heated Probe Voltage Requirements 12 or 24 VDC (must specify when ordering)
Heated probe Power Draw 86 Watts at 12VDC / 172 Watts at 24VDC
Heated Probe Current Draw 8 Amps at 12VDC and 8 Amps at 24VDC
Heated Probe Power Wire Supplied by others
Audio Output 1 Volt P-P max at 300 ohm input impedance
Aux (Audio) Cable 6 ft, three wires: AP audio, AP ground and shield
Audio Options Four
Mute Switch Eagle, Falcon, Merlin, on switch panel.
LED brightness Levels 16, from ultra dim to very bright
Photocell Diode On display, allows for custom daytime/nighttime brightness settings
Pressurized Version Yes

        Kit Components Weights
Eagle Display .21 lb | 3.36 oz
Falcon Display .205 lb | 3.28 oz
Merlin Display .22 lb | 3.52 oz
Valkyrie HUD Mounting Kit .22 lb | 3.52 oz
Standard Probe with Elbows .29 lb | 4.64 oz
Heated Probe 12V or 24V .53 lb | 8.48 oz
Switch Panel Module .11 lb | 1.76 oz
Display I/F Module .605 lb | 9.68 oz
Sensor I/F Mod (Pressurized Only) .43 lb | 6.88 oz
Probe Mounting Kit .425 lb | 6.8 oz
White Hose 25ft .26 lb | 4.16 oz
Blue Hose 25ft .265 lb | 4.24 oz
Power Cable .105 lb | 1.68 oz
Display Cable .235 lb | 3.76 oz
AUX Cable .16 lb | 2.56 oz
Switch Panel Mount Cable .16 lb | 2.56 oz
Sensor I/F Mod Exterior Cable (Pressurized Only) .56 lb | 8.96 oz
Sensor I/F + Audio Interior Cable (Pressurized Ony) .335 lb | 5.36 oz


        What is the importance of your FAA Letter?

Our letter from the FAA states that the install of our AOA system is considered a minor alteration for certified aircraft, as long as certain provisions are met. No 337 required. Said provisions are listed in our FAA Letter, which can be found here.

        What is the average install time?

We have engineered and manufactured our Angle of Attack Systems to be easy to install and use. But because installation times can vary widely depending on aircraft, probe location on wing, and room in cockpit for AOA Kit devices, we do not like to quote install times for aircraft sight unseen. If you want to receive quotes for install, please feel free to contact any of our dealers listed on our dealer map here.

        What does a typical AOA System weigh?

A single display weighs less than 3.00 lbs

        Where should I install the AOA display?

We strongly urge all our customers to mount the AOA display up in the pilots primary field of view, preferably on top of the glare shield (dash mount) or near the very top of the instrument panel. This way, when in the pattern, the pilot will not risk getting distracted because of looking down at the panel to check their Angle of Attack.

        How do I install your AOA display in my dash?

All our AOA displays come standard with the ability to flush mount into the instrument panel of your cockpit via supplied flush mounting brackets in a 2 ¼” opening or surface mount using 6-32 threaded screws; however, we strongly urge your display be mounted as high as possible in your peripheral vision. We have the following mounts available at an additional charge: solid mount kits, swivel mount kits and the Valkyrie HUD (heads up display). Please contact Alpha Systems at (763) 506-9990 or for more information regarding mounting kits.

        Where are the typical AOA Interface Module Installation Locations?

The most common locations are either underneath the glare shield, instrument panel, glove box, under the floorboards or even under the kick panel of the passenger side of the cockpit. If no room there, some have installed behind the last row of seats with the addition of longer cables. Really, it is wherever you have room and can be out of the way. All cables in the standard kit are 6 ft. in length, so the interface module needs to be within 6 ft. of the display. Custom length cables are available for $75.00 each plus shipping & handling. For the pressurized system, the interface module is separated into 2 boxes, 1.) AOA sensor module which connects the 2 , ¼ inch hoses from the AOA probe outside the pressure vessel and is attached in the wing or nosecone area (for twins) and has 4 electrical connections that utilize the existing aircraft bulkhead connectors and pins to act as the “pass through” into the cabin. 2.) The Display Interface module connects to the 12 to 28 volt DC power, Display, Switch Panel, Audio panel, wing bulkhead connector. This box must be mounted within 6 feet of the display or instrument panel. The cables that go to the Bulk head connector are 15 feet on the inside and outside allowing for a wide range of mounting possibilities.

        What size is the AOA Interface Module?

The IF (interface module) box, including the attached mounting brackets, is: In Inches: 5.75 long by 2.60 wide and 1.65 deep.

        How do I determine the proper location for the AOA Probe on my aircraft's wing?

The way to determine the proper location for AOA Probe is to choose an inspection cover/plate location that meets one of the following:

  • The AOA probe is mounted a minimum of 24 in. outboard of the propeller arc.
  • The AOA probe is mounted a minimum of 9 in. inboard of the wing tip.
  • The AOA probe is mounted, with clearance, inboard or outboard of any struts or landing gear.
  • The AOA probe is mounted between 10% to 90% of the Mean Aerodynamic Chord (MAC), or 6” inches from the leading edge and 10” inches from the trailing edge - center span optimal.
  • If the heated probe is to be installed, the AOA probe must first be checked to verify that there is NO effect when turned on to any equipment such as a remote compass system.
For twin-engine aircraft, the AOA probe can be mounted on the nose on a non-structural area if approved by your A&P mechanic. Remove the inspection cover and use it as a template to cut our standard 9” x 9” AOA probe mounting plate to the same shape and drill the same holes. If required, install a “doubler” plate for strength.

        How do I install your probe in my Fabric Wing?

On fabric wings, typically a doubler with nut plates attached between 2 ribs acting as a solid mount internal to the wing, manufactured by installer. Please refer to Regulation 43.13 which states doubler and thru bolt spacing requirements .The Alpha Systems AOA mounting plate would be cut to a smaller size as needed, drilled with matching holes, lining up with the nut plates, and be screwed to the wing, capturing the fabric between the AOA probe mounting plate and the stiffener inside the fabric. The AOA probe must be mounted in a way that is secure and solid, no movement of the plate after installation is allowed. See our doubler plate here.

        Why do you manufacture and sell custom AOA Probe mounting plates?

In order for the install of our AOA system to be considered a minor alteration, the installer must not make any modifications to the wing. In order for this to be the case, the installer will use an existing inspection cover location on the wing and cut our standard mounting plate to fit. The standard mounting plate is then bolted to the wing thru the existing bolt holes the inspection cover used. BUT if that existing inspection cover does not bolt into place, but instead snaps into place such as with composite wing aircraft, you cannot use the standard mounting plate. You must instead use the custom mounting plates, as they clamp into place and therefore require no modification to the wing. Click here for more mounting plate options.

        What are your AOA system's voltage requirements?

Our electronic AOA systems requires approximately 1/2 amp (500 mA)power within its acceptable voltage range of 12-28 VDC. Our recommendation would be to have the Alpha Systems AOA draw power from the avionics bus, through an on/off switch and with a 1 Amp fuse or breaker in-series with the positive lead for the IM (this would offer some protection from surges during startup and the on/off switch enhances operational flexibility).

        Do you supply a power cable for your AOA systems?

Yes, we supply a 6 foot power cable for our AOA systems.

        Does your AOA system have audio?

All of our electronic AOA systems have four audio options, plus a fifth we call Mute. However, our electronic AOA systems do not come with speakers. Instead, we tie into your aircraft’s existing audio panel. You can choose not to use audio option “Betty” by toggling the mute switch. The Eagle, Falcon, and Merlin displays have the audio mute switch on the switch panel.

        How does audio out work?

We provide an audio output, 1 Volt P-P max at 300 ohm input impedance, that your installer will tie down to an existing open audio input on your audio panel.

        Do you provide Audio Cable?

We provide an Aux Cable, 6 foot in length, three wires: AP Audio, AP Ground and Shield.

        Is the shield wire on the Aux Cable floating or grounded at the I/F module?

It is grounded.

        What are your heated probe voltage requirements?

The heated probe works on a separate power source, with a voltage supply of 12 or 28 VDC and a 8 Amp draw. We instruct customers to put the heated probe on a dedicated, switched, 10 amp breaker or fuse as called out in our install manuals.

        Which kits come with a separate switch panel?

If you purchase either the Eagle, Falcon or Merlin kits, you will notice they each come with a separate remote switch panel box. This switch panel includes the SEL/CAL buttons, along with the audio mute switch and audio mute light. These individual displays have more transition segments; therefore, we made the decision to make the display smaller in order to keep it within the 2 1/4" size. We strongly suggest the location of the switch panel be near the pilot for activation, calibration, and audio procedures. It can be anywhere within the cabin and comes with a 6ft extension cable.

        Where should the I/F module be mounted?

There really is no preferred location and it's really an installers preference. We have found that the typical location has been under the floorboards or behind the instrument panel. All of our cables are pre-wired and are 6ft in length. The AOA IM may be physically installed in a variety of locations while observing the following limitations: • The structure must support the additional load of the module. • The sense lines are routed so that they do not interfere with any moving controls or cables. • The electrical wiring does not interfere with any moving controls or cables and shall not come in contact with any line containing flammable fluids or gases. • The AOA IM must be bonded to the airframe (grounded for shielding). • The AOA IM must be mounted within six feet of the AOA indicator. • The AOA IM must be mounted within six feet of the power source, fused and connected with an on/off switch.
Note: If you need a custom cable length, please contact Customer Service at (763) 506-9990 for pricing and availability.

        Is your AOA ASTM Certified?

Yes we are now 14 CFR 21.8(d)certified. Check out our letter here.

        What if I don't have enough clearance in my wing for your standard AOA sense probe?

No problem! We sell a low profile heated probe option for wings that have tight space constraints - typically less than 6". Please visit here to learn more. Also, please note that when ordering a low profile heated probe you must specify which wing it will be placed into - left or right.

        Who can install the Alpha Systems AOA product?

In a Certified aircraft, an A&P can do the installation. In an Experimental aircraft, the owner/operator can complete the install; however, it must be signed off by an A&P for correct installation. Here is a map of our installers.

        How close does the probe angle need to be to get the unit to calibrate properly?

The Alpha Systems Angle of Attack system displays AOA / LIFT measurement of the aircraft by means of an AOA probe that’s mounted solidly to the aircraft. The AOA value consists of the AOA of the wing (when in flight) combined with the angle of the AOA probe to the chord of the wing measuring differential pressures derived throughout the entire flight envelope of the aircraft in which it’s installed.
The electronics must see data within a given range to allow for a linear and full-scale reading. Due to the number of aircraft and other variables; stall angles, wing designs, coefficient of lift, mounting locations, and so on, the probe angle will be initially set at an angle of 50 degrees to the chord of the wing. In most aircraft, starting angle would be derived from the bottom of the wing skin.
During the calibration flight, the display will give direct feedback if the pressure values received from the AOA probe are outside the range to give a proper full scale display indication, the system will flash combinations of background segments; RED + BLUE (pressures too low), or YELLOW + BLUE (pressures too high) which will indicate the direction to tilt the probe.