MyFlyDream Crosshair User manual

MFD Crosshair automatic landing
www.MyFlyDream.com
V1.2
Performing an automatic landing requires a perfectly tuned plane.
Please make sure your plane follows routes perfectly before you try to
land it automatically. "Cross-track error" is very important during the
landing procedure. About "Cross-track error" please refer to appendix A
of this document.
The above photo is the sonar used for auto landing. The "Trig/TX" pin
connects toD11 pin of the AP. The "Echo/RX" pin connects to D10 pin of
the flight controller. You also need to provide+5V power to the sonar.
We recommend to use the CAN-BUS connector of the harness included

it AP kit to connect with the sonar. In this case you need to temporary
discard the CAN-BUS function.
Take the yellow and white wires out from the 24pin connector (Port
D).Insert the yellow wire of the black CAN-BUS connector into D10,
insert the white one into D11.
Once the sonar is connected successfully, point the sonar at the wall
within 2 meters. Another green altitude reading will display below the
original white altitude reading.
The sonar alt reading only displays below 3 meters.

The sonar altitude here is used to detect when to turn off the motor and
adjust the attitude to touch down. Please test it several times to ensure
it works perfectly.
The above picture shows a Laser Range Finder connected to a MFD
Crosshair AP. To activate the Laser Range Finder please set menu [SENSORS
SETTINGS->2ND ALTIMETER] = "LASER" instead of "SONAR".

This Laser Ranger Finder which is capable to measure 20meters is highly
recommended for a more precise and reliable accuracy of auto-landing.
You may find it particularly useful if you need to land somewhere remote.
In this case you will probably want to utilize the Laser with our "Runway
Scan" function(more on it later).
The[AUTO LANDING] menu allows you to define three runways, but only
one of them can be activated at a time. Enter Menu [AUTO LANDING
->Runway1] for editing.
To define a runway you need to specify two points.
Throughout the landing procedure we will use4 points:L1, L2, L3, L4.
Please note: some of them are on the ground level, others are in 3D
space, and have altitude in addition to coordinates.
Please refer to the below diagram and the following explanation.

L1 is the location for final touchdown. Place the plane at this point and
make sure that 12 or more satellites are locked by AP. Select the
menu [L1 - SET] to let the AP record theL1 position. (Alternatively, you

may enter L1 coordinates via your ground station software in case you
are planning a flight to a remote location; more about that later).
TheL1 coordinates(longitude/latitude)will be displayed at the bottom of
the screen.
L2 is the runway entry point. Following the above steps, record the L2
position.L2 altitude can be defined by the menu [L2 - ALT] in cm.
L3is the approach point from which the plane is supposed to head for
the runway, and start to descend to L2.This L3 point is automatically
generated by the AP, and it lies on the extension of the line
connectingL1andL2 . The distance between L3 andL2is defined by the
user. [Runway menu: L2-L3 distance]. L3 altitude is also defined by the
user[Runway menu: L3 - ALT].
L4 is the center of a circle on which L3 lies. L4 is also automatically
generated by the AP.LineL3-L4is perpendicular to the direction of the
runway.L4 and L4 altitude must be the same.
You can define the radius of this circle by [AUTOPILOT SETTINGS->CIRCLE
RADIUS].

Auto Landing Procedure
The above figure is a flight path of an automatic landing. In this example
we selected[AUTO LANDING->RUNWAY1/2/3 ->TURN LEFT/RIGHT=LEFT],
so the plane will circle on the right side of the runway before
approaching. If you set [AUTO LANDING->RUNWAY1/2/3 TURN
LEFT/RIGHT =RIGHT], the plane will use the left side of the runway. Each
runway has its individual circling direction setting.
To activate the automatic landing:
In RTH mode, with throttle in low position, move the elevator to any
corner, and draw a square. For example: upper left->upper
right->bottom right ->bottom left.

If there is an active runway set and available, the flight mode on the
upper left of the OSD screen will change to "LND 1"and the first stage of
the landing procedure will be executed. The plane will fly towardL4 .
When the distance from theL4 is close to the standard circle
radius(defined by [AUTOPILOT SETTINGS->CIRCLE RADIUS]), the plane
will turn right, flying into the tangent of the circle and begin to circle
aroundL4 .The plane will climb/descend to L3 altitude at the highest
rate.
AsL3lays on the circle, the plane will fly closer to L3 with every circle.
Ideally the plane should align to the runway when it reaches L3.
If the altitude and distance are close enough to L3(<10m), the plane will
enter the second stage of landing, LND 2.
Here, the plane gradually descends along the L3-L2line, and flies
towardL2at the speed defined by [AUTO LANDING->LANDING
SPEED] . Once it reachesL2, the plane enters LND 3 stage.
It begins to monitor the altitude using the sonar, and flies toL1 to touch
down. Once the sonar altitude is less than the throttle cut altitude (can
be defined by [AUTO LANDING-> THR CUT ALT]), the AP enters LND
4 stage to turn off the motors and prepare for touchdown.
LND 5 stage is only used if the brake function of the AP is set active by
[AUTO LANDING- BRAK ALT]. The plane will enter LND 5 stage to brake

or reverse the thrust if the sonar altitude is less than the [BRAK
ALT].During the brake period, the E9 port of AP outputs a 1800us PWM
signal. After the plane stops or braking time (4 seconds)is up it restores
to 1000us.
The menu item[AUTO LANDING-> Landing Angle] is used to define the
attack angle for touchdown in LND 3/4 stage. In LND 3/4 stage when the
airspeed of the aircraft is greater than[AUTO LANDING-> LANDING
SPEED], the AP flies with a 0 degree attack angle. As the speed of the
plane decreases, the attack angle will automatically increase
progressively. At a speed of 35km/h the attack angle reaches the value
defined by the user.
WARNING: In LND 1/2/3 stages of the landing, once the THR stick on the
transmitter is moved to a position greater than 50%, the plane
temporarily enters STB mode. The mode switches of the transmitter are
still in positions of RTH combination. The mode switch doesn't match the
flying mode until you re-switch it.
The RUNWAY-SCAN Function:
The aforementioned automatic landing process is highly dependent on
the barometer. Circling around L4, approaching L3, and descending to L2
and ready to turn-off the engine. These actions rely on the barometer. If
the barometric altimeter reading is higher than the actual altitude, the

plane will mistakenly think that there is still enough altitude below, and
continue to land and hit the ground unexpectedly.
The barometric altimeter relies on the recorded air-pressure of the
takeoff point. After a long flight ( > 30 minutes, or even several hours),
the air pressure at takeoff will likely change. At this time, the barometric
altimeter will not be able to accurately estimate its altitude relative to
the takeoff point. It can be worse if we fly from point A to point B and
land automatically. The barometric altimeter readings will hardly make
any sense at the remote runway.
In order to solve the above problems and reliably perform automatic
landing, we need to use a non-barometric tool. Theoretically, sonar can
also be used for runway scanning but practically it should be avoided.
We take runway-1 as an example to explain how it works.
First, activate the runway scan in the menu and change the setting of
[AUTO LANDING-> RUNWAY 1-> SCAN RUNWAY]from "Disable" to "2
Times".
Second, set[AUTO LANDING-> SCAN RUNWAYALT = 25](25 is taken as an
example only). These settings will allow the plane to start scanning from
the altitude of 25 meters and fly over the runway no more than 2 times.
The APwill use the laser altimeter to measure the altitude above the