Flying in summer and mountains – what you need to bear in mind!

Last week, Fliegermagazin published an article on a final report by the SUST. The sad outcome: a flight over the Alps ended fatally for the three occupants. Last weekend, two paragliders also died in accidents in the Swiss mountains. The article goes on to say: “Flying in the mountains is challenging. Accidents happen time and time again because pilots overestimate the capabilities of their aircraft. Even locals and experienced pilots are not immune to this.”

Flying tactics in the mountains – better too high

A flight in the mountains must be well prepared. Forget about flying in a straight line over the Alps and through the mountains. Conditions in the mountains are completely different from those in the Swiss Plateau. The airspace is smaller, the wind and weather conditions are more challenging, and air traffic with gliders, motorized aircraft, helicopters, and paragliders is more varied and intense, especially on weekends. This means that pilots need to be fully focused. A detailed briefing is therefore essential to ensure that you have the necessary capacity to fly safely. The points to be observed have already been covered in the article Briefing, flight tactics and crossing passes. In brief, these are:

• Never fly into a valley unless you are at least 1000 feet (or 2000 feet in windy conditions) above the pass behind you at the entrance to the valley.
• Also, do not fly in the middle of the valley, but on one side or the other so that you always have enough space for a possible turn around. As a rule, this will be the right side of the valley, unless there are downdrafts there; be careful here, as you may encounter oncoming traffic on your side of the valley! See & avoid is therefore very important when flying on the left side of the valley!
• Always cross the pass at a 45-degree angle from the side so that you can easily turn back into the open valley if you can’t continue behind it. Keep an eye on the variometer and altimeter as you approach the pass. If your altitude suddenly drops, it’s the right time to turn back and try again.

Source: Runwaymap.com

Density altitude, climb performance, and control behavior

Some like it hot…aircraft do not! Hot air temperatures mean lower air density. In short, this means less lift and less performance. All pilots learn during their training that serious flight preparation includes calculating the takeoff distance. This is especially true in summer: in addition to a significant increase in the takeoff distance, the climb rate also decreases massively. Poor climb performance must be anticipated in flight planning, especially when flying over aviation obstacles or mountain ranges. Once in flight, it is (usually) too late.

Hot temperatures not only have a significant impact on engine performance during takeoff or cruise flight, but also on the flight and control characteristics of an aircraft during landing. Warm air is thinner, so the wing generates less lift at the same speed. To achieve the same lift, the aircraft must be flown at a higher approach speed. Control response can be sluggish, especially in slow flight shortly before touchdown. Pilots often have to apply greater rudder deflections to achieve the same control effect.

Source: UBC ATSC 113 – Density altitude, Determine “density altitude” and explain why pilots use it

Warm air turbulence during landing – the invisible danger

Flights can be turbulent, especially in summer. Most of the time, we just get shaken around a bit. Why is that? On sunny days, the ground heats up unevenly, with dark surfaces (asphalt, fields, rocks) warming the air more. When the warm air gains enough lift, it separates from the ground as a thermal bubble and rises. This rise can occur very suddenly.

Thermals: rising warm air – the natural lift in the troposphere – MeteoSchweiz

When approaching the short final – an already critical phase of flight – detaching warm air bubbles can pose a real danger, especially at low altitudes. This is because speed and energy are low during this phase and, depending on the situation, there is little time to compensate for the flight attitude.

How can this danger be minimized? If sweat is running down your back in the cockpit due to the hot summer temperatures, it is advisable to postpone your flight until the morning or evening. This is because the thermals are weaker at these times of day. If you don’t want to miss out on the experience, you should increase your approach speed slightly in turbulent conditions (safety margin) and be prepared for sudden wind changes or warm air bubbles. In addition, in strong thermal conditions, choose a runway with a clear approach and few heat surfaces on final approach, if possible.

Source: Michael F.H. Krutina, Schematic representation of the separation and ascent of a heated air parcel.