changeAirAsia Mystery Key Questions About QZ8501

By Tracy Connor

The investigation into the disappearance of AirAsia Flight 8501 has centered on one moment:a request by the pilot to climb 6,000 feet because of weather,which was denied by air trafficc ontro l.

But what the crew was experiencing before that—which led them to make the request—isunknown.And what happened to the plane in the following minutes also remains a mystery,two days after the aircraft vanished from radar.

Indonesian officials have said they believe the Airbus jet went straight to the bottom of thesea,presumably killing all 162 on board.But Greg Feith,a former investigator for theNational Transportation Safety Board and NBC News'aviation expert, says there are manyquestions about the incident that still need to be answered.

Did weather really take down the jet?

It's possible,of course,but a half-dozen other planes passed through the storm-struck areawhere the AirAsia jet vanished. "What did those pilots know that the accident crew didn'tknow?"Feith wonders. "What were they using for decision-making that allowed them to getthrough that line?"

The weather system was big, so climbing from 32,000 to 38,000 feet would not have allowedthe QZ8501 pilots to completely avoid it,he said.But the request for a 6,000-foot change—as opposed to, say,2,000 feet—had to be rooted in a concrete concern.

He noted that it's customary for pilots to report unusual conditions to air traffic control andthat any other cockpit on that frequency would hear them.Feith wants to know whatwarnings the AirAsia crew heard about turbulence or heavy rain and whether they promptedthe altitude change request.

Or did they—along with the air traffic controllers—think they could safely get through thestorm,just like the other planes did,but conditions deteriorated too quickly? "Thunderstormslike this are very dynamic,"Feith said. "It's a high-energy situation."

Who was in control of the plane?

Typically, the crew of a commercial airliner will fly it on autopilot as long as possible,evenwhen making an altitude change.But the j et could have hit turbulence from the storm thatbecame too much for autopilot to handle—forcing the pilot to take over,Feith said.Or thepilot could have decided he could do a better job of responding to the changing weatherconditions.

Why haven' t they been able to find the jet?

where it went down.A very dense thunderstorm could have prevented the signal frombouncing back,Feith said.A change in the plane's attitude—whether it is pitching up ordown or banking to the left or right—could also interfere with radar.As a result, the planecould have flown on for some minutes off radar before it crashed.

After the crew lost control, the aircraft would not necessarily have plunged straight downinto the water. It could have gone into a spiral,reversed course or shot off in any directionbefore hitting the water,making for a large search area. If the plane was intact when it hit thewater, there will be less debris than if it broke up in midair.

Did the plane have ACARS?

The Aircraft Communications Addressing and Reporting System sends flight data fromsensors to ground stations in short bursts,providing vital clues in the case of an accident.When Air France 447 crashed into the Atlantic in 2009,putting its black boxes out of reachuntil 2011, it was ACARS messages that revealed the pilots were getting incorrect speed data."I would love to know if AirAsia had an ACARS subscription and if not,why not?"Feithsaid.

But in the case of another flight,Air France Flight 447,which disappeared off the coast ofBrazil in 2009, investigators had access to a cascade of error messages that were sent overthe ACARS system that indicated,among other issues,a problem with the plane's airspeedsensors that ultimately disabled the plane's autopilot system.

AirAsia and local officials have so far not divulged much technical information about theflight,but Indonesia on Monday asked U.S. investigators,via the State Department, to assistin the search—so perhaps more knowledge will be forthcoming.

Friends, Relatives Await News on

Missing AirAsia Jet

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Tracy Connor

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Tracy Connor is a senior writer for NBC News.She started this role in December,2012.Connor is responsible. . .Expand Bio