The dog days of summer – hot, sticky, sweaty, and potentially dangerous for pilots. Aircraft performance in high temperature conditions is not as good as it is on cooler days.
In the United States, late July through late August is known for being especially sweltering. Of course, depending where you live and fly, you could be dealing with uncomfortable heat and its impacts on air travel at any time of the calendar year.
Does that mean you have to park your plane in the hangar and fly a simulator until the cool weather returns?
We’ve already shared 7 pieces of gear that will help you beat the heat in the cockpit. Now we’re going to take it one step further by reviewing what’s different about flying in the summer and what you can do to practice summer flying safety.
Plan for and Practice Hot Starts (But Try to Avoid Needing Them)
For starters, know that when fuel injected engines sit in hot conditions, especially when a hot engine is turned off for fifteen to thirty minutes during a quick turn, it can cause major problems when you try to start up. Yes, that’s right – we’re talking about the dreaded vapor lock.
Vapor lock starts when your liquid fuel becomes so hot that it turns to vapor. When you try to start your engine, the fuel pump has no feed pressure and is unable to pump the vaporized fuel through the fuel lines that are designed for liquids.
The only way to fix the problem once it’s happened is to replace the vaporized fuel with liquid fuel. You can use a boost pump to push liquid fuel into the lines, but it’s risky because you could also flood the engine if you pump too much.
The best solution is to prevent the problem before it happens. Take these extra steps to keep your plane cool while sitting on the ground, especially if the engine is already hot from a flight:
- Park in the shade
- Park with your nose facing into the wind so the engine gets airflow while you’re stationary
- Open the cowling flaps and oil access door if your aircraft design allows and conditions safely permit
Try to keep your plane cool, but if you turn on the battery and see the oil temperature is already in the green arc, you will most likely need to do a hot start.
Your pilot operating handbook (POH) is the best resource for how to do a hot start on your plane since the procedure varies by aircraft.
Pro Tip: Don’t wait until you’re baking on the sweltering tarmac with a plane that won’t start or an engine that’s hot and flooded because you tried to start it normally without realizing you needed to use a hot start procedure. Review your POH’s hot start instructions in advance so you’re ready for summer flying.
Adjust Your Fuel Mixture for Takeoff, Climb, and Landing
Vaporization isn’t the only fuel-related variable pilots need to consider on hot days. If you’re flying a carbureted engine aircraft, your usual fuel mixture may also need to be adjusted to compensate and provide the best power for summer ground operations, takeoffs + climbs, and landings.
Here’s a general overview of what you need to know about summer fuel mixtures (with the caveat that every aircraft is different, so consult your POH for the best settings for your plane):
Best Summer Fuel Settings for Ground Operations
Instead of using your usual fuel mixture while idling and taxiing, manually lean out on hot days. The ambient air is less dense than normal on a hot day, so your standard settings can result in an overly rich blend that creates carbon build up on the spark plugs.
If buildup occurs, your engine will run rough and have less power for takeoff, which is an even bigger problem because takeoff power is already reduced thanks to higher density altitude (more on that later).
Best Summer Fuel Settings for Takeoff + Climb
As you begin your takeoff roll, confirm your mixture is at the correct richness by listening for engine roughness. You want the mix to be just rich enough that the engine runs smoothly but no richer. This provides maximum takeoff and climb power for your conditions. Remember, full rich settings in high density altitude conditions actually provide less available power, not more.
In addition to listening to the engine sounds, you can also refer to your exhaust gas temperature (EGT) gauges while adjusting the mixture. Target temperatures between 75- and 100-degrees F. Some fuel flow gauges give target rates for marked altitudes, so look for that as well.
Finally, if your plane has a fixed pitch prop but no EGT gauge, lean until the prop’s RPM drops then enrichen slightly until RPM recovers.
Pro Tip: During your climb, as the density altitude increases, keep monitoring engine performance and EGT temps. You may need to make additional leaning adjustments. Again, always consult your POH and follow its guidance.
Best Summer Fuel Settings for Landing
You leaned out your fuel mixture for taxi and takeoff, then leaned it more as you climbed to cruise altitude. Now you need to enrichen it for landing.
As you descend, your density altitude will decrease, your air density will increase, and your engine will need more fuel. You still won’t want to go full-rich on a higher-density altitude day, but you do want to ensure your setting provides full power to support a potential go-around.
Again, use your EGT target temperatures and fuel flow gauge markings (if equipped), or on a fixed pitch prop plane with no EGT gauge, adjust using RPM as a reference.
Pro Tip: If your flight was short and you’re landing at the same airport you took off from, use your takeoff fuel mix setting as an approximation for your landing setting then tweak as needed.
Consider How Full to Fill Your Fuel Tank
Hot fuel expands, so you’re asking for a fuel venting problem if you fill your tanks completely full then sit on the tarmac for a while before takeoff. As the hot fuel expands it can backflow and siphon out through the fuel tank’s vent lines. Don’t be “that person.”
When making your fuel calculations, factor in slightly less fuel than normal if you know you’ll need to park in the heat after your top off. Another option is to take on your remaining fuel right before takeoff, but if your taxi to the fueling pump is too far, your engine may get hot enough during the taxi to trigger a hot start situation when you finish fueling.
Be Conservative with Your Aircraft Performance Calculations
Beware the density altitude dangers that have contributed to or caused too many summer crashes. Remember that in addition to weather, one of the most dangerous impacts of hot summer weather is its effect on aircraft performance.
Once pressure altitude is corrected for nonstandard temperatures (and humidity), you get density altitude (DA) – the altitude your aircraft feels like it is flying at. The hotter and more humid the day, the higher your density altitude and the worse your aircraft performance.
As you run your aircraft performance calculations for the increased density altitude factor on a sweltering day, remember to leave extra margin for error. Pilots like this one who factor density altitude incorrectly can find that they don’t have enough lift to get off the runway and clear terrain obstacles during their climb.
Run your numbers then pad in a significant safety margin, and you will be a lot better off. The density altitude calculation formula is pressure altitude in feet + (120 x (OAT – ISA temperature).
Watch Your Weight
Let’s say you’ve done your performance calculations using conservative estimates to reflect the effects of higher-than-normal density altitude. That’s great, but you’re not done yet.
Reducing your takeoff weight is another way to improve your plane’s summer performance and avoid extended takeoff rolls and slow climb performance that could be dangerous in areas with low terrain features. After all, the heavier your plane is, the more lift it needs to generate in thinned summer air.
Pro Tip: Run your performance calculations at your usual weight, then run them again at even 100 pounds lighter. The difference could mean hundreds of feet on your takeoff roll and 50’ obstacle numbers. Consider whether you could jettison some weight in exchange for better performance and enhanced safety.
Check for Icing
Ice on a hot summer day? It sounds very counterintuitive, but if you’re also dealing with humidity and flying a carbureted engine, your engine could indeed ice up. Here’s how:
The design and workings of a carbureted engine significantly reduces its internal temperature. Add high humidity and a dewpoint close to the ambient temperature, and you could be looking at ice even on a steamy August day.
The rule of thumb is that if relative humidity is above 50% and/or the dew point is within five degrees of the ambient temperature, you should take steps to reduce the risk of icing.
Check your POH for specifics, but you will likely see guidelines to use full carb heat at lower power settings and to install and monitor a carburetor temperature gauge so you know if you are approaching icing potential.
Plan Your Flight to Minimize Turbulence
You’re not imagining it: hot summer days are some of the worst for turbulence. Temperature extremes mean greater thermal air mass instability. On a hot day, as the sun bakes the ground, it creates hot surface air that rises into the atmosphere. The upward airflow is felt as convective turbulence.
The best way to avoid this type of turbulence is to plan your flights for earlier in the day while the relative ground and air temperatures are more stable and no hot air masses have been created.
If you or your passengers are not early risers, consider waiting until early evening when the air temperatures have stabilized. The worst time to fly is mid-day.
Altitude is also a factor. The closer you are to the ground, the worse convective turbulence will be. Cruise at 5,000 feet or higher and plan a descent that doesn’t unnecessarily linger in low altitudes.
Learn How to Recognize (and Avoid) Developing Thunderstorms
Speaking of convection, the same unstable shifting air masses that cause turbulence can also develop into frontal thunderstorms. Preflight weather briefings help you recognize and avoid areas of frontal thunderstorm development.
Also know your cloud types and be on the lookout for clouds with rapid vertical development as these can contain dangerous thunderstorms and hail.
Remember that the FAA recommends skirting storm cells by twenty miles where possible and at a minimum flying no closer than 5 miles to thunderstorms. Avoid the temptation to fly underneath a thunderstorm, since severe turbulence, windshear, and hail are likely.
Heated air masses can produce spontaneous storm cells away from front lines. These types of thunderstorms are less predictable, but you should be alert for air-mass thunderstorms and related severe weather in the following conditions:
- Humidity above 50% and/or temperature and dewpoint within 5 degrees F of each other
- Winds aloft blowing from over a body of water, as this adds moisture to the air
- Winds blowing upslope (even more dangerous in the mountains)
- High pressure paired with colder than usual air aloft
- Strong Jetstream above your flight path
- Weather reports indicating unstable air, severe weather, and/or hail
Watch for Weather Report Updates
Always check the convective forecasts and flight radar reports before flying. While en route, reference a weather app and tune in for real-time radio-based Flight Watch services on 122.2 MHz.
All the various types of weather reports give you the information you need when you need it so you can make the best possible flight decisions.
Weather reports warn of many dangerous summer weather conditions, and thunderstorms are one of the biggest threats. A Convective SIGMET is issued to warn pilots of:
- An area of thunderstorms affecting 3,000 square miles or greater, with thunderstorms affecting at least 40% of the area.
- A line of thunderstorms at least 60NM long, with thunderstorms affecting at least 40% of the length.
- Severe or embedded thunderstorms affecting any area that are expected to last 30 minutes or more.
Pro Tip: Brush up on your METAR, TAF, and PIREP understanding with the interactive computer-based Aviation Tutorials Weather Statements 3.0 training course. Gleim Aviation Weather and Weather Services and the ASA Navigating Weather guide are also excellent pilot weather resources.
Avoid “Get-Home-It is”
Finally, remember that summer weather is unpredictable. The chances of getting caught overnight due to sudden inclement weather are high.
Although you may be tempted to take off or continue home through marginal conditions, make a personal commitment to avoid scud running or threading the needle between cumulonimbus clouds and other unstable weather masses. It’s just not worth it.
Instead, plan ahead and keep an overnight bag stowed onboard so you have everything you need to comfortably wait out an overnight delay. It’s better to arrive home safely tomorrow morning than to have a classic case of pilot “get-home-itis” and risk a crash by pushing to make it back tonight.
Read these Posts to Brush Up on Pilot Weather Reporting Systems and Tools
- AIRMET vs SIGMET: Everything You Need to Know (Guide)
- AWOS vs ASOS: What You Should Know
- How to Read METAR Aviation Reports (Complete Guide)
- How to Read a TAF (Terminal Aerodrome Forecast)
It’s Your Turn
We’d love to hear from you. What strategies do you use to make summer flights safer and more enjoyable for you and your passengers? Any memorable summer flight stories you’d like to share with your fellow pilots?