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Flying safely in the mountains: why tactics and altitude reserves are essential for survival

Last updated on 22 March 2025
Flying in alpine terrain is considered one of the most demanding disciplines in general aviation - and rightly so. The combination of topography, weather phenomena, low power reserves at high density altitudes and the frequent lack of evasive manoeuvres makes mountain flying a challenge for pilots. A tragic example of this is provided by an accident that occurred in Switzerland in summer 2019 and whose investigation report was recently published by the Swiss Transportation Safety Investigation Board (STSB).

A fatal flight through the Swiss mountains

The pilot concerned was part of a Triple formation flight from the Pays-d'Enhaut ins Wallis. As a young, inexperienced pilot, she relied on the group's joint planning and dynamics - a common mistake in group flying, where individual performance limits quickly fade into the background.

In the course of the flight, however, she underestimated the terrain requirements and altitude of the passes. Without sufficient altitude reserve, it flew into a valley from which it there was no longer a safe way outwhen it became apparent that the climb was not sufficient to cross the pass. The aircraft subsequently collided with the terrain - with fatal consequences.

In its report, the STSB states that this is a Concatenation of several wrong decisions traded:

  • Poor flight tactics in the mountains
  • Lack of consideration of the wind
  • Insufficient height reserves
  • Group pressure in formation flight
  • Lack of situational awareness

Mountain flying requires special preparation and flight tactics

In contrast to flights on flat terrain, pilots in the mountains not only have to take into account the height of the terrain, but also many other factors. include other factors in their planning:

1. altitude reserve for pass crossings

Basic rule:
At least 1000 ft (300 m) above the pass when there is no wind -
at least 2000 ft (600 m) with wind.

The Actual overflight altitude depends on wind direction, strength and risk of turbulence. A mountain saddle that seems accessible from the valley can turn out to be a treacherous trap in headwinds or strong thermals.

2. valley flights: only with alternative option

Flights in valleys should only be startedwhen it is certain that:

  • the course of the valley is known
  • the pilot has an overview of the terrain
  • there is a safe turning possibility
  • there is sufficient space for course corrections

Entry without a view of the end of the valley or without Sufficient altitude to fly over a slope or pass is highly risky - especially in unknown terrain or unpredictable wind conditions.

3. weather and wind: the invisible opponent

In the mountains Wind effects particularly pronounced. The so-called Foehn wind, lee turbulence, Downwind on the leeward side or sudden thermals can throw a stably planned flight into chaos within seconds.

Especially for strong wind from about 20 kt extreme caution is required. Experienced mountain pilots even advise in such cases to No flights over mountain passesas turbulence can intensify in a dangerous way.

4. power reserves and density level

Another critical point is the Motor and climbing performance with high density height - a phenomenon that occurs particularly on hot summer days.

  • Warm air = lower density = lower buoyancy force
  • Engine performance and propeller efficiency decrease
  • Starting distances increase dramatically
  • Climbing performance is often reduced by 30-50 %

This can have fatal consequences, especially at small mountain airfields with short runways.

5. do not underestimate group dynamics

Formation or group flights are particularly risky if Pilots with different levels of experience are travelling together. Less experienced participants tend to adapt to the behaviour of the group - even if they Exceed your own safety limits.

Supposed peer pressure, combined with difficult conditions, can lead to serious mistakes. Every pilot is ultimately solely responsible for their own safety and should never get into a critical situation due to peer pressure.

Conclusion: Flying in the mountains requires respect, preparation and discipline

The tragic accident in summer 2019 is not an isolated incident - but it is a Reminder to all pilotswho venture into alpine terrain. The combination of impressive scenery, narrow valleys, differences in altitude and weather dynamics makes mountain flying fascinating, but also a challenge. Dangerous if underestimated.

The most important rules at a glance:

Never fly "blind" into a valley - recognise early on whether you can leave it safely
Keep sufficient height reserve - if in doubt, too much is better than too little
Analyse wind conditions and avoid critical zones such as leeward sides and narrow sections in strong winds
Consider density altitude and aircraft performance, especially in summer
Avoid peer pressure - your safety comes before group goals


Source references:
Staysafe.aero

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