According to ATSB, aircraft systems don't compensate for vertical velocity at all. (Unlike horizontal velocity, which is compensated for, but with assumptions about stationary satellite.)
I'm trying to understand this.
Total (or uncorrected) horizontal velocity is much greater than vertical velocity. But are you suggesting the aircraft corrects for its own ground speed? And so vertical velocity becomes relatively greater when compared to horizontal velocity corrected for ground speed? That is, vertical velocity makes a significant contribution to BFO because horizontal velocity is corrected for ground speed.
Have I got that right?
Presumably the aircraft uses GPS to establish its ground speed. Would GPS always have been available? Presumably GPS does not rely on satcom, and someone piloting the aircraft around the tip of Sumatra would have relied on GPS.
How about the postulated fuel exhaustion at the end, and the final partial log on perhaps due t APU. Would the aircraft system have a GPS derived ground speed available in order to apply the necessary correction at this log on. Or would ground speed still be in the process of being established at the time of the satcom log on, and would a ground speed of zero be assumed and no correction be applied (it would make sense I guess for the system to initially assume aircraft not moving when system booted up).
Sorry for all the questions. A lot of this technical stuff is beyond me.