Land and Hold Short

The featured article of the day on Wikipedia for Saturday 29 October is Metrication, the process of converting a country to metric from various historical units of measure. Now that Ireland has switched, the only three countries left not officially using metric (or in the process of changing) are Liberia, Myanmar (Burma), and the United States, though many people still informally use older systems for some things — for example, I use metric for temperature and distance (on the ground) and for buying food, but not for weighing myself, measuring my height, or buying lumber.

Because Canada and Mexico are metric while the U.S. is not, we’ve come up with a funny mishmash for North American aviation. We use nautical miles for distance and knots for speed (even most Americans don’t know those); statute miles for visibility (or feet under conditions of very low visibility); feet for elevation, altitude, and runway dimensions; inches of mercury for air pressure; and Celsius for outside air temperature (but not for cylinder head or oil temperature). Got all that? That’s right, if you’re six miles from the airport and there’s six miles visibility, don’t expect to see the airport, because six statute miles of visibility is 9,656 meters, while six nautical miles of distance is 11,112 meters, about a kilometer and a half further. Even American pilots use Celsius for temperature: you can always tell which Americans visiting Canada are pilots, because they’re the only Americans who understand the temperature on the Canadian weather report.

In Europe and most of the rest of the world, I know that they give runway dimensions in meters and air pressure in hectopascals (millibars), but I’m not sure if they use kilometers for distance, and I’m pretty sure they don’t use meters for altitude (or else standard altitudes wouldn’t mesh up). If the U.S. were finally to give in and go metric, would we switch to metric for all of aviation? It would certainly make things simpler for someone building a new plane or learning to fly from scratch, but there would be a lot of gauges to recalibrate, a lot of weight-and-balance to recalculate, and probably a lot of accidents caused by unit confusion until we straightened everything out. Remember that the Gimli Glider was, mainly, a result of confusion during metrication at Air Canada.

My Warrior’s engine is finally back from overhaul in Halifax after its lighting strike, and I hope to be back in the air in a bit over a week. Next month, I’m planning a long (7+ hour) flight from Ottawa down to Atlanta to speak at the XML 2005 conference. If you are one of the large group of people who share an interest in both technology and flying, I’d love to see you there: I don’t plan to talk about flying from the podium, but would love to chat about it in the halls or over a drink or meal.

This will be the longest single-direction flight I’ve done (though not the most hours I’ve flown in a single day). Since it will be icing season, I’m going to schedule in a lot of flexibility, and will use the airlines if nothing else works out.

According to this New York Times article (via Kottke), FedEx launches five mostly-empty jets every night — from Las Vegas, Duluth, Laredo, Fort Myers, and Portland (ME) — all heading for Memphis through various meandering routes. These flying spares often end up diverting mid-flight to deal with package overflows at hubs or with equipment failures on other FedEx flights. Constant diversion sounds like an interesting challenge both for the flight crews and for the dispatchers.