Originally Posted by
RatherBeOnATrain
The air in the atmosphere moves relative to the ground (ocean surface), so there are two "speeds" to calculate: Airspeed (speed of 777 relative to the air) and Groundspeed (speed of 777 relative to the ground).
Airspeed is a function of the fuel burn rate while the Groundspeed is what they need in order to calculate where the flight ended. (Groundspeed multiplied by the time flown will give the distance to the point where the flight ended.)
My reading of the updates is that the recalculations found a higher air speed and lower ground speed than originally calculated.
No - the new search area has nothing to do with this... here is from the AMSA official release #24 on 28 March 2014...
The new information is based on continuing analysis of radar data between the South China Sea and the Strait of Malacca before radar contact was lost.
It indicated the plane was travelling faster than previously estimated, resulting in increased fuel usage and reducing the possible distance it travelled south into the Indian Ocean.
As they know how long the plane was in the air (thanks to the satellite pings continuing until 8:11AM) they must have worked out the plane slowed down on its journey down south or else it would have run out of fuel before the 8:11AM ping. The slower speed means it did not travel as far south as originally anticipated - see also this chart release by AMSA yesterday showing the new search area compared to previous days - note the possible routes based on MH370 speed over the Indian Ocean...
https://s3-ap-southeast-2.amazonaws....ch_handout.pdf
I think besides the faster speed in the initial phase (before the plane turned south) the climb to 45,000 feet and the fact the plane flew at low altitude on its way to the Strait of Malacca would have also contributed to the increased fuel consumption...