Shop Talk: Angle of Attack Indicator - AeroElectric Connection
mount the vane assembly and routing the connecting cable through ... (small hole holds Hall sensor). Board with ... span position (bottom green display element ...
Angle of Attack Indicator An inexpensive alternative D AVE BARK ER, EA A 587700
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his device is really just a simple weather vane with the axis mounted horizontally to indicate relative wind in the vertical direction as opposed to an azimuth for a weather vane on the barn. Why an angle of attack (AOA) indicator? Because it can tell you what the aircraft is really doing compared to the typical variable incidence of the pitot tube that is rigidly mounted under the wing. The pivoting vane of the AOA indicator always flies directly into the relative wind. The angle it makes with the attack angle of the wing can be measured and provides accurate flight status in maneuvers such as short take-off and landing attitudes. It uses a magnetic field sensor called a linear Hall-effect sensor. This is a device that outputs a voltage proportional to the strength of a magnetic field. The vane carries a small permanent magnet that rotates it relative to the Hall sensor device located on the Delrin mount sleeve. The output voltage is used to drive a panel-mounted 10-segment multicolor bar graph display. The display LEDs change position and color from green to yellow to red as the angle of attack increases. AOA display boards require minimal panel space but should be mounted high on the panel to stay within your peripheral field of vision while looking outside. The hardest part of this project is deciding where to mount the vane assembly and routing the connecting cable through the wing to the sensor. The sensor vane needs to be located in the undisturbed airflow, away from 96
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prop blast and wing empennage effects. In many aircraft, mounting parallel to the side of the pitot tube structure is a good choice. My plane has a standard heated pitot tube structure, and I built a Delrin ring carrier for the Hall sensor and pivot bearing that slides on the pitot tube and positions the vane parallel and slightly behind the pitot intake port. The vane and fin itself can be formed from plastic. I used a piece of Delrin rod equipped with an aluminum fin. It mounts on a 1/8-inch stainless steel pivot shaft. The vane carries a small 0.375-inch-long rectangular permanent
AOA display boards require minimal panel space but should be mounted high on the panel to stay within your peripheral field of vision whle looking outside. magnet mounted in the inboard face of the vane about 1/4-inch ahead of the pivot shaft. The north-to-south side face of the magnet rolls about the pivot parallel to the Hall sensor face. By keeping the arc travel within the physical length of the magnet, we can achieve a linear position voltage output from the Hall sensor versus angle of displacement of the moving vane. To minimize aircraft panel real estate, the topside of the PC board is scored about .030-inch deep along the side of the bar graph display. Mount the bare board in a vice and back away from the score mark against a sharp (square) edge. A mill vice is perfect for this operation.
the moving vane equipped with its permanent magnet. The magnet moves across the face of the Hall sensor as the aircraft pitches up and down.
Assembly Hall output voltage versus position
By carefully pushing the display portion backwards over the sharp edge of machine vise, the PC board folds the display portion 90 degrees without breaking the connecting traces on the back surface. Hold it in the 90 degree position and fill the gap with glue. If this is done carefully, you will not break any of the copper traces on the backside of the board. However, if you do damage a copper trace, scrape off the green solder mask on the broken trace, tin and bridge solder it with fine copper wire. The sensor portion of the circuit board is cut all the way through and can be broken out completely after the display fold process. Trim off the unused portion of the Hall sensor board remnant, and install the Hall device magnetic field sensor, plug, and capacitor. This PC board is mounted on the Delrin ring sleeve support, which in turn carries
Populate the board with the components as shown on the board annotation and the photos. Solder the parts in place and additionally solder the touching display and driver chip leads at the board fold. (This will provide additional structural strength.) Install Hall sensor and plug on backside of the PC board. Mount in the pitot tube mount slot. The Hall sensor should be flush with the mount surface. The most tedious portion of the job is usually the routing of the connecting cable (two-conductor plus shield) from the sensor through the wing to the aircraft instrument panel.
Calibration The display board has two blue adjusting trimpots that allow scaling to fit the aircraft performance type. This will vary if you are flying a trike or a jet. The uppermost trimpot on the display board sets the gain (that is, how many bars the display
The panel display unit and sensor. Barker mated an aluminum fin to a Delrin rod to make the indicator. The Hall sensor is mounted on a Delrin ring that attaches the indicator to the pitot tube. EAA Sport Aviation
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shop talk
Mount and pivot bearing and vane shaft (small hole holds Hall sensor).
AOA Vane mounted next to Pitot tube.
Board with plug and Hall sensor mounted on bottom side of PC board.
Board with plug and Hall sensor mounted on bottom side of PC board.
All LEDs on (not the normal display).
(right) Top, bottom and overlay PC board layout.
(left) AOA circuit board schematic.
moves up and down with each degree of vane rotation). The lower trimpot is an offset adjustment. This moves the span position (bottom green display element turn on). This bottom LED should be on when the aircraft is in straight and level flight. The upper red light should turn on at the stall angle for your particular aircraft and wing design; a range of between 15 to 40 degrees for most aircraft types. Note: In ground calibration you will be pitching the vane downward to set the gain trimpot, which is the same as the wing pitching upward while the vane maintains a constant position to the relative wind. Please note the gain and offset pots are somewhat interactive and will require some 98
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iteration to zero in on optimum. Finally, please, if you are going to check out the limits of performance of your aircraft, do it with lots of altitude! This device is an indicator. It will not rescue you from sloppy piloting.
3-Pin Plugs (2) 2-Pin Plug (1) Cable Termination Connectors (2) Power Terminal (1) 20 Feet of Two-Conductor plus Shield Cable
The AOA kit consists of: Electronic Components Double-Sided PC Display Boards, cut and scored N305 Hall Magnetic Sensor LM 78L05 Regulator LM 3914 Bar Graph Drive MV5A164 Multicolor LED Display 10K & 1K Pot 510-Ohm Resistor 1uF Capacitor 10uF Capacitor
Mechanical Parts ¼-inch x 4-40 Swage-Type Mount (2) Prefab Delrin Sensor Vane and Fin Post Axle Components Neodymium Magnet Delrin Pitot Tube Mount Assembly
ring carrier for the Hall sensor and pivot bearing that slides on ... position voltage output from the Hall sensor versus angle ... Note: In ground calibration you will.
applied to correct for nonstandard weight and/or load factors. 3 ... An airplane, by its very structure, ... is subjected to a high G-loading, as in a steep turn, the trim ...... In principle, the calibrated airspeed depends on true airspeed and on .
Here is a summary of the main ideas that will be explained in this chapter: .... Configuration changes can affect the airplane's preferred angle of attack. ..... you start the climb, you can bet that you will need roll those three sectors black out t
Thanks to Terry O'Neill for his suggestion to address angle of attack in "Test Pilot." Send your comments and suggestions to Test Pilot, EAA. Publications, P.O. ...
maneuvering the airplane affects stall speed. Because the stall AOA stays the same, the only thing that affects stall speed in our example is how much lift the ...
lots of things that could disturb the angle of attack, such as (a) an updraft, as depicted in figure 6.4, or (b) a ... VNE or below VS â leading to in-flight structural failure or a nasty stall. ... An amusing consequence of the decalage rule invol
Stall speed, maneu- vering speed, maximum range ... maximum range regardless of your airplane's weight? .... Checks weather along your route. ⢠Calculates ...
By Terrencc O'Neill(EAA 5572). This air-angle indicator was first offered to EAA members in a July,. 1970 SPORT AVIATION article by. Terrence O'Neill, EAA ...
gross weight and density altitude has ... the elevator to control AOA and power ..... 9 or 14V none unless heated. 12 to 28V. 4 Wan max. 14 or 28V. 0.3 amp.
convey a lot of meaning about the wire and its function - valuable information when ..... (2) Power control or steering diodes are used between the main bus and ...... storage at a float voltage just above the battery's own open circuit terminal ....
operational vehicles made analysis and correction of problems a breeze by comparison; US ..... In a pinch, build your own fixture by soldering two alligator clips ...
Angle of Attack Meter: Page 1. Angle of Attack (AoA) is a central concept to the mechanics of flight. It is important to understand the relationship AoA has on the ...
price anywhere from about $20 to $30. The alligator clips are Radio Shack part number 270-. 356. They have red and black vinyl coverings. I used No. 14 lamp ...
Circulation (By Mail and Outside the Mail): 1. Mailed Outside-. County Paid Subscriptions Stated on PS Form 3541 (Include paid distribution above nominal rate, ...
air data measurement methods; includes references and bibliography. ⢠Measurement of Static Pressure on Aircraft (Report 1364). ⢠detailed information on how ...
A flip of the switch turns the system on and off or reverses the current. Having wired one airplane without this, I will tell you that it is well worth the time and money.
To check the receiver IF for correct operation, inject a 10.7 Mhz carrier amplitude modulated ... E. Q520 failure can cause no-stow condition in the antenna mode. ... Refer to page 4-18, section 4.4.3 of the maintenance manual for ...... check A.C. r
the surfaces and eliminates the bonding needed for good sensitivity. ... The Audio Leveling Circuit of the COM units require an IC ...... Unit inop in the middle of the band: Warped wafer switches caused by the mounting lock Covered by Senlce ...
field more readily than some of the more complicated situations which arise. ... M e n bench testing the unit for a no reply light for instance, check the AOC voltage for around 4 ..... Corn receiver sens: 2 uv (hard) for 6db (s+nyn with 1 khz @30% m
Finishing Tape Timesaver. As I was covering my RANS S-7 using the Poly-Fiber system, I found that by using a drawing compass I could save a lot of time laying ...
latter from the former will show the Cleco is âmeasuringâ the grip length of the rivet you ... rod in the center is free to slide into position to transfer the required rivet ...
This project will show how to fabricate a standard three-terminal auxiliary aircraft battery .... lief cover must slide over the counter bored screw heads in the plug ...
Sep 10, 2004 - simple ideas in physics and matters of historical fact. ...... amperes/square-inch of current density and voltage ...... one I use in the lab that has a laptop port and a book full of features. ... with these â the jaws are not harde