Malaysia Airlines Flight MH370 and Payne Stewart

Please take this post for no more than what it is: reasonably well-informed speculation. It's not a prediction nor a claim.

At the time of this writing, the fate of Malaysia Airlines Flight MH370 remains a mystery. It's been gone for 11 days, and all that's known is that it made a radio communication, mysteriously turned west, and 7 hours later an automated system made a handshake communication with a satellite which could have come from any point along two arcs on the Earth's surface a certain radius from the satellite. Most news reports are saying it's being treated as a deliberate action.

I read a lot of aviation news and am an aviation enthusiast (and amateur aerodynamicist), but definitely not a pilot. I've had enough friends and family who were pilots to teach me it's too deep of a rabbit hole for me, but in return I've gotten my fill of stick time. I've found so far that aviation web sites have had substantially better reporting of MH370 than mainstream news sites, some of which still don't understand the basic technologies involved; specifically, the various aircraft communications systems, how each works, and what type of information each carries.

I've seen about a half dozen theories, and my distillation of them is what I'm going to present here. It requires nothing extraordinary and ticks all the boxes of what we know about the missing aircraft. It's not too unlike what happened to Payne Stewart, the pro golfer whose private jet took off in 1999, but for some unknown reason the pressurization system did not engage. The crew was quickly incapacitated, and the plane climbed to its preprogrammed altitude and flew a straight line until it ran out of fuel and made an uncontrolled tumble out of the sky. For hours, the flight was headline news as fighter pilots flew alongside and tried to figure out what was going on with this unresponsive, self-flying airplane.

First of all, it's been 11 days, and nobody's seen the plane nor picked up any emergency locator beacon signal. We can safely assume that it's underwater.

What could have incapacitated the crew? A lot of things, but we're looking for something consistent with the other events:

• The turn west. From the aircraft's last reported position, they turned for an alternate emergency landing site: possibly Palau Langkawior back to Kuala Lumpur. They knew they had a serious problem.

• Automated communications went silent. This means they were either damaged or deliberately disabled.

• No signals came from the emergency locator beacon while the plan was in range of any nearby receiving stations. This can't reasonably be manually disabled, so most likely there was no trauma that would have triggered it until it was well out of range over water.

A catastrophic decompression, Payne Stewart style, wouldn't have disabled the communications systems and would have triggered the emergency beacon. However, an isolated fire could have disabled them, and would not have triggered the beacon (a number of things can trigger (shock, temperature, immersion, pressure) but not the faint smell of smoke from elsewhere on the plane. The smell of smoke certainly would have prompted the pilots to head for an emergency landing site, and if it increased it could have easily disabled them. The smell of smoke also would have prompted the crew to turn off all unnecessary electrical systems, very possibly including communications systems.

The press has made much of the ACARS system, and asked why didn't it transmit all the pilots' actions. The reason is that ACARS is not intended to do this; it does not log cockpit actions or transmit details about the flight. ACARS sends (mainly) engine maintenance data, and can also receive certain types of data like gate changes or weather reports. Malaysia Airlines' subscription to service providers sent such data only every 30 minutes. A change of direction by the crew, or the disabling of systems, would not be included in an ACARS report. Inmarsat (the satellite operator) has reported that normal signals from ACARS were received, and were forwarded to Malaysia Airlines.

"Primary radar" is what we usually think of as radar: a signal sent from an antenna, bounces off the plane, and comes back to the antenna, telling you where the airplane is. This is fine but it has limited range, and doesn't see over the horizon. Flights over water are usually below the horizon and/or out of range for primary radar, so it's not surprising that we have limited radar information for MH370.

"Secondary radar" and the "transponder" we hear so much about are different. These signals reach farther but don't give us good position information if outside of primary radar coverage. The plane receives the signal, but unlike primary radar which is passive, the plane responds with its own radio transmission of a 4-digit code that is "squawked". Air traffic controllers will tell a pilot to squawk a certain code on a certain frequency, when they want to identify an aircraft. The MH370 pilots had already said "Good night" to the air traffic control area they were leaving, so they may or may not have continued proactively squawking. Even if they had, an electrical problem may have disabled the system, or it may have been one the pilots shut down in the event of smoke.

The pilots (and possibly others on board) were disabled by whatever was going on aboard the plane,and it continued south to reach the Inmarsat arc that's over water. This direction could have been part of an approach to Palau Langkawi, or could have been back south to Kuala Lumpur, but it took them past a point where they were spotted on military primary radar over the Malacca Strait. I propose they were headed south at this point. The plane continued on this automated headingout over the open ocean; past the arc where Inmarsat received its last handshake, then ran out of fuel and dropped into the drink. As there was no fuel left there would have been no significant explosion (which imaging satellites might well have been able to see) and probably even not much of an oil slick.

It may be a long time before we find the wreckage. When we do -- and we will eventually -- it will be in this area.No terrorism, hijacking, murders, international spy stories, or pilot suicides needed.

The accompanying image shows a blue dot at the last reported radar contact in the Malacca Strait; the Inmarsat southern arc in red; the plane's southbound course in blue and the proposed crash site in yellow.