Max Gust Limit

Raindeer wrote:

Any thoughts on max wind gusts in mountainous vs flat areas for landing? Above 12kt gust I tend to avoid approach but only fly in flat lands. What are other people’s gust limits?

Would entirely depend on aircraft, pilot and direction. Why would mountains make any difference?

During my PPL training my FI sent me up to do solo circuits in 20G30. Wind direction was perfectly aligned with the runway though, so it was no problem. Landing speed was 70 kts with a Vs of 49, so plenty of buffer in case of gusts.

As Jason said, depends on wind direction, aircraft and pilot. Terrain can “deflect” or channel gusts, in case of EDWF where I trained the first half of RWY26 has trees on both sides of the runway, which create a pretty turbulent ride when the wind is strong. All local pilots thus aim for the second half of the 1200m runway in windy conditions, while guests are thusly advised by AFIS.

My crosswind limit varies with my crosswind currency.
With runways near a hill, the wind direction and gusts can vary. Glenforsa can have an unacceptable right-hand crosswind at the West end, but straight down the runway by midpoint.
With runway 19 Oban, and an 80° crosswind from the west, I’ve asked for, and got, 01 to avoid the gusts I could see on the sea.
With CBs nearby, gusts in mountainous areas can cause an unrecoverable stall. An instructor who checked me out a few times was seriously injured trying to go-around at Grand Junction, Colorado. The NTSB failed to convince me recovery was possible, considering the wind records.

Need to be really careful with terrain in the vicinity of the airport when windy. I had a little scare taking off from Calvi RWY 18 in August with something like 190/17G25. I used the full runway length and gained as much altitude I could before turning right. During the turn I was flipped over to a 60° bank or so despite countering with full aileron deflection to the left. Pushed the stick forward to unload the wings and traded altitude for speed, completed the turn and came wings level. Quite scary stuff.

I had a rather interesting flight today…. at 4500 ft we partly had 160 kts true and 80 kts GS (!). Along with the usual up and down drafts. Wind at landing was directly 90 degrees from the left, 18 kts, with 26 kts gusts. Worked. But don’t want it every day…

Why would mountains make any difference?

In mountainous terrain, the METAR is likely to include a TEMPO with a high gust factor (at places where you actually have a METAR). It’s common here (at ENVA) to have 5-10 knots from the SE, with a TEMPO of 15G30 for instance. Slightly more wind with large gusts come and go at random fashion.