Mountain flights - a challenge for man and machine
The Alps and other mountain ranges hold a great fascination for many aviators. The imposing landscape, thermal sources and the opportunity to fly long distances in gliders or motorised aircraft are what make them so attractive. At the same time, however, the complexity also increases:
- Diverse traffic: Gliders, motorised aircraft, helicopters and paragliders often share the same airspace.
- Limited airspace: Narrow sectors, control zones and complex routing require precise flight planning.
- Turbulence and wind systems: Downdrafts, lee waves and rotors can occur unexpectedly.
A thorough Briefing before take-off is therefore mandatory. If you prepare your route carefully, you will have more capacity for navigation and airspace observation during the flight.
Flight tactics in the mountains
Different laws apply in the mountains than in the lowlands. The following principles are essential:
- Valley entry only with sufficient height: At the entrance to a valley, you should be at least 1,000 feet above the level of the pass, preferably 2,000 feet in windy conditions. This leaves enough reserve for unforeseen downwinds.
- Flying sideways instead of in the centre: If you are flying along the side of a valley, you can initiate a reversal turn at any time. The right-hand side is the usual choice - unless there are downwinds. In this case, the left-hand side is used, but this requires maximum attention due to oncoming traffic.
- Pass crossing at a 45-degree angle: This makes it easier to return to the valley in the event of unexpected downdrafts. The variometer and altimeter are constantly in view - if the altitude drops unexpectedly, a new approach is the safer option.
Density Altitude - why height is not the same as altitude
On hot summer days, the lower air density reduces lift and engine performance. The term Density Altitude (density altitude) describes how high the aircraft actually is from an aerodynamic point of view. Even at 30 °C and medium altitude, the effective density altitude can be several thousand feet above the aerodrome level.
The consequences are serious:
- Extended starting distance: The aircraft takes off later.
- Poorer climb rate: Obstacles such as trees or power lines can become critical.
- Changed control behaviour: The rudder has a slower effect, especially when landing, as the wing produces less lift in thin air. A higher approach speed is necessary to maintain the same safety distance from the stall.
Especially in alpine terrain, poor climb performance can be dangerous when crossing passes or mountain ranges. An exact calculation of the take-off and climb performance is therefore an essential part of flight preparation.
Thermals and warm air turbulence
Summer thermals are a joy for gliders, but often a challenge for motorised aircraft. The uneven heating of the ground - due to tarmac surfaces, fields or rocks - leads to rising warm air bubbles. These often break up suddenly and can cause critical turbulence on approach.
Especially in the Short Final warm air turbulence is dangerous. The aircraft is slow, its energy reserves are low and there is hardly any time to compensate. Sudden gusts can lead to stalls or uncontrolled movements.
Tips for minimising the risk:
- Schedule flights in the morning or evening hours when the thermals are weaker.
- In strong thermal conditions, increase the approach speed slightly to have a safety margin against stalling.
- If possible, choose slopes that offer a free flow of air without disturbing heat sources.
Good airmanship in practice
Experience shows that many accidents are not caused by technical defects, but by pilots' misjudgements. Even locals who know their region well can get into critical situations.
Good flying practice therefore means
- Never underestimate the weather, terrain and performance.
- Plan alternatives and make decisions in good time.
- Don't be afraid to cancel a flight even in summer if the conditions seem too demanding.
Conclusion: Preparation is everything
Summer heat and alpine terrain are a fascinating but dangerous combination. Those who take into account the physical principles, adapt their tactics and fly carefully can certainly benefit from the special attractions. Flying in the mountains requires respect, discipline and a good dose of humility before the forces of nature. Those who take these principles to heart will be richly rewarded - with unforgettable impressions over one of the most beautiful landscapes in Europe.
Source references:
Staysafe.aero