The Downwind Turn Revisited

In 2018, a Junkers Ju 52 crashed in the Swiss Alps while attempting to cross a 10,000-foot saddle from south to north amid gusting winds.

Peter Garrison

Monday, November 05, 2018 at 11:39 PM ET

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The fatal August crash of a Junkers Ju 52 brings to mind some aspects of downwind turns that are worth discussing. JU-Air

Key Takeaways:

The 2018 Ju 52 crash in the Swiss Alps, potentially caused by a rapid turn in gusty mountain winds, highlights the dangers of gust-induced stalls in challenging conditions.
A common misconception that turning downwind causes an aircraft to lose airspeed is incorrect; airspeed is relative to the air mass, unaffected by a steady wind's direction change relative to the ground.
The actual hazard in turbulent conditions lies in how strong gusts—especially those with a vertical component (e.g., a horizontal gust hitting a banked aircraft)—can rapidly increase the angle of attack, potentially leading to a stall, particularly when an aircraft's stall margin is already reduced in a steep turn.

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In August 2018, a sightseeing flight crashed in the Swiss Alps, killing all 20 aboard. The airplane, a Junkers Ju 52, was attempting to cross a 10,000-foot saddle from south to north. The wind was out of the north, gusting to 25 knots. Witnesses said the airplane approached the saddle, then banked sharply to the left and suddenly dived to the ground, “as if following a plumb line.”

The official analysis of the accident will not emerge for some time. I don’t have an opinion as to what actually caused it. But the accident did bring to mind some aspects of downwind turns that are worth discussing.