The Flight Plan versus the actual route

The weather vertical cross-sections show conditions undergoing slight improvement during the northward part of the trip, and complement Captain Steigner’s belief that this would be a successful flight. The middle part of the journey, from Poretta to Marseilles, would take the plane across the sea, far from the Alps and into (theoretically) improving weather. The mystery is why the plane was so far from its planned route. While circulating winds might have forced the plane to drift eastwards, experienced pilots like Colonels Fair and Upham, not to mention Major Cobb, an experienced pilot in his own right, using the simple but reasonably accurate navigation equipment of the times, would have soon realized that they were going off course and done something about it. If we include the navigator, Lieutenant Ramirez, it is difficult to believe that four sets of eyes in the cockpit were all blind to such a deviation from the intended route…unless the deviation was a deliberate choice. Were they “cutting the corner”? And, if so, why?

French testimony identifies a flight path approximately over Mount Cenis. to the north of Turin. The Board of Enquiry estimated that the flight direction at the moment of impact was 350 degrees. Looking at the map for the flight plan this appears to take the aircraft reasonably directly from the area of Pisa towards Lyon, one of the waypoints on the original flight plan. While mere unchecked drift cannot be totally excluded, it is also possible to interpret this as a deliberate choice of heading. If we discount as improbable that this experienced flight crew were unable to comprehend they were being blown more than 90 miles off their route, then the logical conclusion is that they had decided to head straight for Lyon by overflying part of the Alps, rather than “going the long way round” across the Ligurian Sea towards Marseilles first. They had already been through the worst of the forecast weather. It may have been a rough trip, but they had a sturdy, nearly new plane (it had less than 200 flight hours). We could speculate from the Board of Enquiry’s recommendations that strict adherence to a flight plan and its time schedule were considered “nice to have, but not absolutely essential” by EATS crews of the time, particularly during night flights. Cutting half an hour from a bumpy flight may have looked an attractive proposition to the whole crew. The weather may even have seemed better to the East, away from the sea. But no-one had attempted to formulate or obtain a weather forecast to overfly the Alps. If we accept that the conditions forecast by the Capodichino weather experts were reasonably accurate, the route documented in the flight plan seems to be the safest one.

But this may be the key to the problem. We don’t know exactly how good or bad the conditions in the direction of Marseilles were at the time. Perhaps the weather was not looking too good over the sea. Recent research into the extremely reliable Swiss archives reveals that on November 1, 1946, 108 mm (more than 4 inches) of rain fell at Marseilles (that means very heavy thunderstorm activity), and that at the Great St. Bernard Pass (not far from Mont Blanc), 8/8 cloud, 97% humidity and 34 mm of rain were recorded. These are the kind of phenomena typical of South-South-Westerly currents generated by the known low pressure over the Gulf of Genoa at the time of the flight. This opens the door to the hypothesis that the plane’s Captain made a reasonable, weather-based decision to change course and go inland, but with the mountains most likely in thick cloud, he and his crew would be relying mainly on instruments.

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