Mavlink Command #70 from LabVIEW


i have to send the Mavlink Command #70 to a Pixhawk.
My created Message looks like this:
Start of Frame 254
PL length 18
Packet Seq. 0-255
Device ID 253
Comp. ID 0
Message ID 70
target_system 1
target_comp 0
ch1 1500 (205 and 3)
ch2 1500 s.o.
ch3-8 65535 (255 and 255)
CRC calculated by a tool

is this enough?
Its send roughly 2 times a second to the telemetry2 port
Could you tell me how the message looks like and if, what else messages do i have to send?
Do i maybe have to send a hearthbeat? I couldnt find useful information for me how to build a heartbeat message…
Useful means for me, what information contains every single byte, like above…

best regards