Wednesday, June 1, 2005
12 Tips To Beat The Heat
Here are a dozen effective suggestions for safer summertime flying
10 THUNDERSTORMS AND SEVERE WEATHER. Frontal thunderstorms are pretty easy to anticipate with the scantest of preflight weather briefings. What’s much harder to predict, however, are the air-mass thunderstorms, those that crop up from the heat of the day away from surface fronts. Convection makes the atmosphere like a pot of water just about to boil—the potential is there, but you can’t tell all hell is about to let loose until it begins. Here are some telltale signs of air-mass thunderstorms and severe weather:
• Humidity above roughly 50% and/or a temperature and dew-point spread within 5 degrees F.
• Winds aloft blowing from the direction of a body of water, adding moisture to the air.
• A high-pressure system with colder-than-standard air aloft.
• Indication of a strong jetstream above your route of flight.
• Winds blowing upslope, especially in mountains.
• Unstable air, indicated by a negative number on the Lifted Index (ask your weather briefer).
• Widespread pilot reports of turbulence and/or building cumulus clouds.
• PIREPs or METARs indicating hail of any size.
• Local media reports of expected severe weather.
Just as with turbulence, air-mass thunderstorms tend to build with the heat of the afternoon. If conditions favor storm development, consider sitting out the hottest part of the day, flying instead in the morning as well as the early evening.
11 LEANING FOR LANDING. As the airplane descends, air density increases, so you’ll need to enrichen the mixture to prevent the engine from getting so lean it stumbles or quits. Ideally the mixture should be gradually returned to the full-rich position during the descent, so full power is available should you need to abort the landing. But what if you’re landing at a high-DA airport? In that case, the justification for full rich goes away. Instead, you need to aim for a mixture control position roughly appropriate to a best-power setting at full throttle for that possible go-around.
If you routinely fly in high-DA conditions, start looking at the physical position of the mixture control for takeoff in those conditions and return the control to that approximate position prior to landing. If you’re flying into an airport at a higher DA than you’re used to, you might work the mixture control to one-half to one inch away from fully forward as an initial landing position. Knowing this isn’t scientific, your go-around procedure would include advancing the throttle, establishing a climb attitude and then adjusting the mixture as necessary to hit your fuel flow, revolutions per minute or EGT target for your present altitude.
12 FUEL VENTING. Have you ever seen fuel dripping from a Cessna 172’s wing vent on a hot summer’s day? Aviation fuel expands with an increase in temperature. In some airplanes, the expansion may be huge enough that fuel begins to siphon through fuel tank vent lines. Don’t fill the fuel tanks completely to the brim if the airplane is going to sit in the heat for some time before flying. Remember, the fuel you have put in the tank may already be hot and expanded—meaning there’s less time in the tanks than it would appear. You may decide to wait until shortly before takeoff to top off the tanks in the hot season, although if you have to taxi to the fuel pump, you may be setting yourself up for a hot start after fueling.
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