Heading RCADev

 

HOME

PHANTOM UAV

VACUUM FORMING

OpenTX

CONTACT ME

 

Previous Page – App Note 34

Next Page – App Note 36

OpenTX - Application Note 35

Air Speed Sensor

This application sets up the Air Speed sensor with air speed displayed on a telemetry screen, air speed announcements and a stall warning.

 

Mounting the Sensor and Pitot Tube

The pitot tube is mounted under a wing about 40 cm out from the fuselage, well out of the turbulence caused by the propeller.

 

 

 

 

 

 

The two silicon tubes from the pitot tube go into two holes through the balsa sheet of the wing and then to the sensor.

 

The sensor is mounted in the aileron servo access hatch. Two smart bus cables are connected to the sensor. One cable goes to the FrSky receiver smart bus connector and the other goes to the next smart sensor on the smart bus, in this case, a current sensor.

 

Taranis Transmitter Configuration

Search New Sensors

Turn power on the receiver. On the Taranis telemetry set up screen, select “Discover new sensors” and press Enter. The variable “ASpd” appears with an ID of 10. 10 is the default address that this sensor has on the smart bus. Press Exit to stop discovery.

 

Modify Variable Parameters

Edit the “ASpd” parameters to set the unit to kph (instead of knots) and to enable logging, tick the “Logs” box.

Data Logging

To log data on the SD card, use the following special function to enable data logging when switch SC is in the middle position.

 

Special Function

Source

Function

Par 1

Par 2

Check Box

SF10

SC-

SD Logs

0.1s

 

Telemetry Screen Display

Display air speed ‘ASpd’ and maximum air speed ‘ASpd+’ on a telemetry screen.

 

Announcements and Warnings

Switch SD is used to enable a stall warning and air speed announcements as follows.

 

Switch SD

Stall Warning

Air Speed Announcement

SD

OFF

OFF

SD

ON

OFF

SD↓

ON

ON

 

The stall warning is announced if the airspeed is less than a set value. This value is dependent on your aircraft. The air speed value, when enabled, is announced every 4 seconds.

Stall Warning

The first thing to do is to determine the aircraft stall speed. Enable data logging so that the airspeed is logged. Fly to a ‘three mistakes high’ altitude (very high but in good visual range), turn off the throttle and raise the nose above level to slow the aircraft. Allow the aircraft to stall and recover several times. After the flight on Companion, display the graph of ASpd and determine what the stall speed is.

The following graph shows a graph of airspeed (blue) and throttle (red). The throttle was dropped to zero four times (with elevator pulled slightly back) during which the airspeed dropped until the plane stalled. The aircraft then fell nose first and picked up air speed again.

 

The following graph shows a section of the graph above. The airspeed drops to about 24 kph during the stall before rising again when the aircraft falls. I chose to set the stall warning at 30 kph.

 

 

Use this logic switch and special function to announce a warning when the airspeed drops below 30 kph..

 

Logical Switch

Function

V1

V2

AND Switch

Duration

Delay

L5

a < x

ASpd

30

!SD

---

---

 

Special Function

Source

Function

Par 1

Par 2

 

SF10

LS5

Play Track

stallwng

2s

 

The audio file ‘stallwng.wav’ says ‘stall warning’ and is not a standard Taranis file. It must be created and put in the [SOUNDS]/[en] folder of the SD card. To create audio files, refer to Application Note 4.

After taking off, switch SD to the middle or down position to enable this warning.

Announce Air Speed

During a landing approach is a good time to know what your airspeed is. Use these logic switches and special function to announce the air speed every 4 seconds when switch SD is in the middle position and the air speed is less than 50 kph. If switch SD is in the down position, the air speed is announced regardless of air speed..

 

Logical Switch

Function

V1

V2

AND Switch

Duration

Delay

L6

a < x

ASpd

50

SD-

---

---

L7

OR

L6

SD↓

---

---

---

 

Special Function

Source

Function

Par 1

Par 2

 

SF11

L7

Play Value

ASpd

4s

 

 

Phantom Divide

 

Previous Page – App Note 34

Next Page – App Note 36

 

Footer RCADev