ADS-B - Pilots input requested

[ZeeDoktor]

Hi all,

we've talked about ADS-B already in another thread in this forum, now I'd like to know how ADS-B is implemented on the various airplanes you fly. If your plane is equipped, would you mind answering these questions please?

1. What's the data source for position information?

2. Can you (the pilot) influence in any way WHAT is transmitted in the ADS-B signal?

3. related to 1: How is it possible that position data sent is 4NM offset?


Cheers

[discountinvestigator]

I fly a VDL 4 equipped aircraft. The position source comes from the GPS on the aircraft which is the only certified source. However, we also have a second transmission coded in which comes from the GPS timing chip for the datalink. The chips are different and we have checked that the coding software for position solution is different. The aircraft source also has differential corrections added to it from the ground reference station.

We have a ground based computation which checks the official and timing based position solutions, plus the differential reference input to work out if we have confidence in the official solution. If the official solution is considered to have high integrity, then it is displayed to the controller.

Pilot influence consists of not switching the box ON. We do not need to enter a flight number into our system as that is handled on the ground from the 24 bit address/tail number/flight number function. Each aircraft has a hard coded set of pins which input the 24 bit address, so if we switch aircraft boxes, it is still OK as the connection pins do the coding for us. The controller looks out of the window at the registration as it goes past.

We have no offset function in our flight system for the routes flown.

Does that help? We also have stopwatch, map, flightlog and on a good day, the NDB to help us!