The newly defined search area for Malaysia Airlines Flight 370 (MH370) is based on the convergence of analyses that combine revised assumptions and the few known data points in an attempt to predict the missing aircraft’s most likely flight paths.

A detailed report prepared by the search strategy working group (SSWG), released Thursday, explains the new assumptions, but offers few additional facts to what is know about MH370’s disappearance. The Australian Transport Safety Bureau (ATSB), SSWG’s coordinator, released the report.

The revised search area’s parameters are based on three factors: when MH370 made its final turn south, the aircraft’s performance limitations, and analysis of satellite communications data by Inmarsat detailing a series of seven “handshakes” between the aircraft and its network that helped establish the Southern Indian Ocean as the flight’s likely termination point (Aviation DAILY, March 26).

While the SSWG cautions that there is “uncertainty associated with each of these factors,” it is most sure about the search location being along the so-called seventh arc, which corresponds with the final handshake established by the Inmarsat analysis and lines up with the aircraft’s likely maximum range. 

When the flight turned south and how the 777 was flown—particularly its altitude and airspeed—are unknown.

Primary radar shows that MH370’s last-known positive fix was on a westbound track over the Malacca Strait, north of Indonesia. The Inmarsat analysis showed the aircraft turned south.

The SSWG took two approaches to determine the search area’s distance from the turn. One combined the satellite data with several assumed turning points, and one that analyzed the data independently.

The group then plugged in variables to determine how far MH370 could have traveled. Its assumptions started with information, including fuel quantity, relayed in the flight’s last routine ACARS transmission, which occurred 25 minutes after it departed. 

“During the period of the aircraft tracking to the south, there was no altitude or speed data available,” SSWG notes. As a result, the group used a variety of variables, such as how fast the aircraft flew and whether it changed tracks between the arcs.

“From each of the different analyses, the highest correlation paths were compared and each crossed the seventh arc within 450 km. (280 mi.) of each other,” the report explains.

SSWG compared satellite data from other flights to determine the variation between their known tracks and estimated ones. 

The group combined the results with other calculations, such as where the aircraft’s possible ranges intersect the seventh arc, and established the revised search area.

SSWG also analyzed three  types of accidents—loss of control, unresponsive crew/hypoxia, and “glide” events caused by engine failure or fuel exhaustion— seeking similarities to MH370. SSG found that factors in hypoxic events, such as a loss of radio communication and a long period of controlled flight with no track deviation, most closely match MH370. 

However, SSG cautioned that its assumptions were made to help pinpoint a search area, not suggest a theory.

The new search area covers 60,000 sq. km., extending 650 km. along the arc. It is 93 km. wide. Searchers scoured the area’s surface for five days during March and April’s six-week search. 

The search effort includes two phases. A bathymetric effort, expected to last three months, is underway. An underwater search phase is expected to begin in August and could last a year.