Hot weather may look deceptively benign on weather radar, but high temperatures should give pilots some pause during flight planning.
While the arrival of high summer temperatures is often lauded by the general populace as the perfect time to travel, extreme heat carries its own share of hazards and considerations for those operating aircraft. Lowered performance, abrupt formation of hazardous weather, and pilot health are brought to the forefront of our concerns during summer heat, and should be taken into consideration during flight planning.
Hot and high
One invisible effect of high temperatures is a reduction in density altitude and aircraft performance, specifically during takeoff. While especially noticeable at higher altitudes, where the air is thinner to begin with, high heat affects lower altitudes as well; recently exemplified at Phoenix Sky Harbor. In either case, the result is longer takeoff runs required to get airborne, possibly exceeding available runway length.
Factor in the altered density altitude when you plan your flight. If high density altitudes prohibit proper aircraft performance, change the plan. Reschedule the flight for earlier or later in the day (when temperatures are cooler), reduce passenger or cargo weight, and/or reduce fuel weight and plan for more enroute fuel stops. When planning enroute stops, calculate the density altitude and conditions before landing or risk flight delays due to a lack of available aircraft performance to accommodate another takeoff within your original timeframe.
Extreme summer heat produces the perfect environment for severe thunderstorms. It is not uncommon for clear morning skies to develop dark and foreboding clouds as the day wears on. Keep a watchful eye on the weather before and during your flight to avoid pop-up storms.
Try to plan flights outside of the hours of 4-7 p.m., especially in the midwestern United States, as this is when storms are most common and at their strongest. Fast-moving cold fronts are also a sign of powerful storms to come, as they often bring turbulence at best and tornadoes at worst. Avoid severe storms by at least 10 nautical miles--ideally 20. Never fly beneath a thunderstorm, and flying over one should be done with great caution, if at all--high winds above and within a storm will often blow hail out the top. If flying through a storm is unavoidable, maintain a straight course, rely on your instruments, and turn up cockpit lighting so as to reduce the effect of lightning on your sight.
You vs. the sun
Finally, we haven't yet spoken of the most important aspect of the aircraft: the pilot. The hot summer months can take a toll on humans just as they can on aircraft. Keep hydrated by drinking more water than usual, and avoid very salty snacks before and during flight. Stay cool with air conditioning whenever possible, and shade, cool rags, or drinks where not. Avoid strenuous physical activity for extended periods of time in the hot sun; try to relegate outdoor activities to cooler hours of the day. Whenever possible, perform aircraft-related tasks indoors or in a cool, shaded area. Dehydration, heat exhaustion and heat stroke not only impair your ability to fly, but can cause serious harm. Take good care of yourself, so you can take care of your aircraft and all your summer flights.
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