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Having said that, an onboard fire may not disable everyone or anyone, initially. However an exploding nose wheel tire can do alot of damage or one that "catches fire" . The nose wheel tire is located very near what is called the electronic and equipment bay or as some refer, the E and E bay. An exploding tire, or slow burn could theoretically damage critical components knocking out electric power to communication equipment. And or damage other electronic equipment so as to create a high load on other equipment, causing electric busses to start disengaging. A nose wheel tire can become overheated during the takeoff roll. It happens when a plane is heavily loaded, warm temperatures, long takeoff roll, late rotation, or rotation close to max tire speed. Not really uncommon. In the scenario many are suspecting, is that smoke began to fill the cockpit. Oxygen masks are on and an immediate turn to the nearest airport is made. The climbing and descending can be because the autopilot has also become disengaged, that would explain why it took so much altitude to recover. But as the 777 captain says, the oxygen system would have also become disabled or depleted and that is most unlikely. Very rarely to we find what is called dual failures. The airplane would not necessarily be on fire enough to bring it down immediately. Small, fire, damaging equipment, producing smoke and might even go away if the oxygen source, (high altitude in an unpressurized bay) goes away and or fuel source is not enough to continue the fire. Plausible but i am not buying it myself. But its the closest to Ocam razor that I have read.

All good points, but let's remember they flew to after leveloff, about 40 minutes after takeoff before they dropped off secondary radar.

First, as the captain (caller to Rush) pointed out, wheel fires are almost always brake-related. There are no nose gear brakes.

The 777 is a very sophisticated airplane. The caller could have gone on to say a nose gear fire would have manifested long before level-off. There are tire pressure sensors that would have generated alerts even before a fire might have happened, not only based on minimum or maximum pressures, but on pressure differentials with adjacent tires exceeding a preset value. These sensors would have alerted the crew to a tire in the process of deflation. We know they didn't have a tire failure (catastrophic) on takeoff or they would have returned immediately, or at least after dumping fuel, because the alert system would have told them they had a tire failure. Likewise if there were a nosewheel bearing failure -- the temps would have taken longer to climb but they would've blown the fuse plugs (deflating the nw tires) long before level-off. And lastly the temps at FL350 are very cold. The tires cool as they are exposed to the airstream before retraction, and then they cool again as the jet climbs rapidly to outside temps of around minus 50C at 35k. So the chances of an overheated tire causing problems are attenuated by the low temps in the unpressurized nosewheel well. Additionally, they weren't really very heavy -- they had 50 empty seats and only 8 or so hours of fuel. This is an airplane when fully fueled can go about 14 hours, so this was not a heavyweight takeoff, and it was at night when the temps are lower.

I think the nosewheel fire scenario is highly improbable.

Arghhhhh. LOL

You all are thinking too narrowly. The theory is saying the nose wheel tire was the "initial" source of the problem. Overheat due to exceeding tire speed limit on the takeoff roll or any other numerous causes.

The exploding tire OR tire on fire, who knows who cares, can and has created damage to critical components in the E and E bay. Any one of those damaged components then can cause shutdown of that component or others. And from that damage IS the source of the smoke or fire.

You make some very good points of why it can not be the nose wheel tire, however

Recheck you flight times. It was only 50 minutes after takeoff before the problem occurred. Not unusual for and exploding tire and damaged components to take that long to manifest itself.

One final thought re temperature and weight. Remember this is Malaysia where a cool night is 85 degrees and 90 percent humidity.

Yes 50 empty seats, but speculation is for the cargo weights to be high. Normal for that time and route of flight.

Another factor which is not and would not be known, is this area Southeast Asia has had a higher than normal incidents of tail strikes on takeoff. Due to many factors, mostly wrong weight calculated causing an early rotation. It would not surprise me nor anyone who understood the depth of that fact to find pilots are holding off rotation to prevent such an occurrence. Thereby leading to overlimiting the nose wheel tire speed.

It is always amazing to me to find and discover how one factor affects another. Thats why it is so fascinating