MH370 Flight Simulator Claim Unravels Under Inspection

SimPhugoid

In last month’s New York magazine article about Zaharie Ahmad Shah’s flight simulator, I cautioned against treating the recovered data as a smoking gun:

…it’s not entirely clear that the recovered flight-simulator data is conclusive. The differences between the simulated and actual flights are significant, most notably in the final direction in which they were heading. It’s possible that their overall similarities are coincidental — that Zaharie didn’t intend his simulator flight as a practice run but had merely decided to fly someplace unusual.

What I failed to question was the report’s assumption that the six points all belonged to a single flight path. On closer examination that assumption seems ill supported. Rather, it seems more likely that the six points were recorded in the course of  two or possibly three separate flights. They were interpreted as comprising a single flight only because together they resembled what investigators were hoping to find.

The first four points do appear to show a snapshots from a continuous flight, one that takes off from Kuala Lumpur and climbing as it heads to the northwest. Between each point the fuel remaining decreases by a plausible amount. Each point is separated from the next by a distance of 70 to 360 nautical miles. At the fourth point, the plane is at cruise speed and altitude, heading southwest in a turn to the left. Its direction of flight is toward southern India.

The fifth and sixth points do not fit into the pattern of the first four. For one thing, they are located more than 3,000 miles away to the southeast. This is six or seven hours’ flying time. Curiously, at both points the fuel tanks are empty. Based on its fuel load during the first four points, the plane could have flown for 10 hours or more from the fourth point before running out of fuel.

The fifth and sixth points are close together—just 3.6 nautical miles apart—but so radically different in altitude that it is questionable whether they were generated by the same flight. To go directly from one to the other would require a dive so steep that it would risk tearing the aircraft apart.

The picture becomes even more curious when we examine the plane’s vertical speed at these two points: in each case, it is climbing, despite having no engine power.

The ATSB has speculated that in real life MH370 ran out of fuel shortly before 0:19 on March 8, and thereafter entered into a series of uncontrolled porpoising dives-and-climbs called phugoids. In essence, a plane that is not held steady by a pilot or autopilot, its nose might dip, causing it to speed up. The added speed willl cause the nose to rise, and the plane to climb, which will bleed off speed; as the plane slows, its nose will fall, and the cycle will continue.

Could a phugoid cause a plane to climb—663 feet per minute at point 5, and 2029 feet per minute at point 6? The answer seems to be yes for the fifth point and no for the sixth. Reader Gysbreght conducted an analysis of 777 flight-simulator data published by Mike Exner, in which an airliner was allowed to descend out of control from cruise altitude in the manner that the ATSB believes MH370 did.

A diagram produced by Gysbreght is shown at top. The pink line shows the plane’s altitude, starting at 35,000 feet; the blue line shows its rate of climb. Worth noting is the fact that the phugoid oscillation does indeed cause the plane to exhibit a small positive rate of climb soon at first. But by the time the plane reaches 4000 feet — the altitude of the sixth point — the oscillation has effectively ceased and the plane is in a very steep dive.

Gysbreght concludes:

As expected for a phugoid, the average rate of descent is about 2500 fpm, and it oscillates around that value by +/- 2500 fpm initially. The phugoid is apparently dampened and the amplitude reduces rapidly. I was slightly surprised that it reaches positive climb values at all. Therefore I think that 2000 fpm climb is not the result of phugoid motion.

Not only is the plane climbing briskly at the sixth point, but it is doing so at a very low airspeed—just above stall speed, in fact. If the pilot were flying level at this speed without engine power and pulled back on the controls, he would not climb at 2000 feet per minute; he would stall and plummet. In order to generate these values, the plane must have been put into a dive to gain speed, then pulled up into a vigorous “zoom climb.” Within seconds after point six, the simulated flight’s speed would have bled off to below stall speed and entered into an uncontrollable plunge.

Perhaps this is why Zaharie chose to record this particular point: it would have been an interesting challenge to try to recover from such a plunge at low altitude.

What he was doing at points 5 and 6, evidently, was testing the 777 flight envelope. This might seem like a reckless practice, but I think the opposite is the case. From time to time, airline pilots do find themselves in unexpected and dangerous conditions. For instance, as Gysbreght has noted, “On 7 october 2008 VH-QPA, an A330-303, operating flight QF72 from Singapore to Perth, experienced an In-flight Upset west of Learmonth, West Australia. The upset was caused by a freak combination of an instrumentation failure and an error in the flight control software, which resulted in an uncommanded pitch-down. The vertical acceleration changed in 1.8 seconds from +1 g to -0.8 g.” It would be better to experience a situation like this for the first time in a flight simulator in one’s basement, rather than in midair with a load of passengers and crew.

What Zaharie clearly was not trying to do was to fly to McMurdo Station in Antarctica, as some have speculated.

For one thing, while a 777 is fully capable of flying from Kuala Lumpur to Antarctica, it was not carrying enough at point 1 to make the trip. And if one were trying to reach a distant location, one would not do so by running one’s tanks dry and then performing unpowered zoom climbs.

The misinterpretation of the flight simulator data offers a couple of cautionary lessons. The first is that we have to be careful not to let a favored theory color our interpretation of the data. The investigators believed that MH370 flew up the Malacca Strait and wound up in the southern Indian Ocean, and they believed that Zaharie was most likely the culprit; therefore, when they found data points on his hard drive that could be lumped together to form such a route, that’s what they perceived.

A second lesson is that we cannot uncritically accept the analysis made by officials or by self-described experts. Science operates on openness. If someone offers an analysis, but refuses to share the underlying data, we should instinctively view their claims with suspicion.