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Old 23rd Mar 2014, 12:41
  #7503 (permalink)  
Capt Kremin
 
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If MH370 wreckage found in Southern Indian ocean.....

Then it was very probably a deliberate act....

The "ghost plane after malfunction" theory does not work if any wreckage of MH370 is found in the SIO search area.

If a 777 reaches has a route discountinuity in the FMC, it reverts to HDG mode. All the MCP setting are referenced on magnetic unless in the polar regions (80 degrees N or S) or the HDG REF button is pushed. That would be a deliberate act of someone who knows the systems and implications.

In the case of the "Ghost plane" scenario the aircraft, after it turned WNW would have been either tracking to a programmed FMC waypoint or it would have been in a lateral AP mode referenced on magnetic north, HDG or TRK, it does not really matter. If tracking to the FMC waypoint, once it reached it, it would have reverted to HDG.

For the aircraft to track direct to the area of the last known ping and the current search area, there are only two ways to do it. One is a programmed FMC waypoint and the other is someone flying the aircraft via the HDG or TRK button and taking into account the 30-35 degree change in magnetic variation encountered along the route.

Here is the Isogonal chart for the Indian Ocean. The purple lines are magnetic variation.



Obviously if a pilot can take magnetic variation into account for 6-7 hours, he can also program an FMC to take him straight to the point. Deliberate action.

If a "ghost plane" had left the northern Malacca Strait and headed south in either HDG or TRK (remember TRK is still magnetic) going towards to the now search area, it would have had around 188 degrees (!) set in the HDG window. The following diagram indicate what would have happened in that case.




It is necessarily not definitive and works on a distance travelled every hour of 485 Knots GS and it takes the midpoint magnetic variation value in each leg.

The Pink line is the direct track.

The Yellow line is the approximate path a heading of 188 would have achieved if not changed from the northern Malacca Strait. The distance between the search datum/red line and the end of the yellow line is about 420NM.

The Red line is the approximate last ping satellite arc.

The Green line is an approximate track that a heading of about 197 would have taken to arrive at the search zone.

It is only valid if:

1. the previous pings match this approximate track and,

2. the fuel on board could have kept the aircraft flying for that length of time, and,

3. 197 was the last track set in the HDG window before the crew was incapacitated. This is approx 90 degrees away from the last known track.

It is also about 200nm longer than the direct track.

I haven't seen any evidence that the green line matches the track of the previous pings, nor know of any safety related reason why the crew would have selected a southerly heading after clearing the Malacca Strait.

Here is a closer view.



The Malaysian Govt has stated that direct interference is the primary suspect here. I believe that is based on evidence from the previous pings that would show a direct line being taken to the search area datum, which implies FMC input.

If nothing else, this shows that a "ghost plane" would have taken a curved path to the crash site due to reversionary AP modes and changes in magnetic variation.

Any direct line over such a distance however, must be deliberate programming of the FMC.
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