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Landings at Megara LGMG limited to max demo crosswind in the POH

hmng wrote:

Maybe we can start some kind of prize for most “original” rule?

For that competition: Does anyone still remember that Siemens prohibited Pipistrel in 2014 from doing the first electric flight across the channel because “their engine is not certified for flights over water”

Germany

When seeing this thread, I immediately thought I had previously come across airport regulations regrading crosswind limits. No I found one of them. Guess where… Italy of course. AFAIK, nobody bats a lid on that one…

Last Edited by boscomantico at 22 Jan 15:10
Mainz (EDFZ) & Egelsbach (EDFE), Germany

“you are flying the aircraft outside chartered waters nonetheless.”
You may have flown these waters many times before.
PS an excellent example of a mixed metaphor, I think.

Maoraigh
EGPE, United Kingdom

You do understand that the max demonstrated x-wind figure in the POH does not mean that the test pilots have attempted takeoff/landing in stronger cross-wind and found that impossible or dangerous?

It means what it means. The aircraft behaves OK up to and including that figure, period. Above that value, you have to figure it out yourself. It may fly just OK, or it may not. It may require extraordinary skills, or it may not. There is no knowing exactly at what point the aircraft becomes uncontrollable, or why.

Flying with a cross wind component exceeding the demonstrated value, and you are in fact a test pilot. It’s fully legal, but you are flying the aircraft outside chartered waters nonetheless.

Nothing wrong with that, only funny looking at the other thread where people suddenly find it “dangerous” to do a dead stick landing, which is fully charted and a requirement for any PPL license.

The elephant is the circulation
ENVA ENOP ENMO, Norway

LeSving wrote:

Hmm, people don’t trust their own abilities in making a dead stick landing and would rather pull the chute than glide down to a runway. But, when it comes to cross wind landings everybody are all of a sudden expert test pilots showing the finger to the POH

For me, a high-crosswind (significantly above POH value) landing, on the Cessna single-engine high-wing planes I have most experience with, is definitely much less an event (much easier) than a dead stick landing in benign conditions.

ELLX

alioth wrote:

The crosswind reduction varies with the cosine of the offset angle you can use

No. It varies with the difference of the respective cosines of:

  1. the angle between the wind and the runway
  2. the angle between the wind and your landing track = the angle between the wind and the runway + the offset angle you can use

The result can be very different from what you describe:

  • A pure crosswind behaves as you describe. On runway track, you get cos(0°)=100% of the wind as cross, on 10° offset, you get cos(10°)=98.48% of it.
  • A 45° wind gives you cos(45°)=70.71% of the wind as crosswind on runway track, but cos(55°)=57.35% on a 10° offset. That’s a 19% relative reduction (81% of 70.7% is 57.275%).
  • A 60° wind gives you cos(60°)=50% of it as crosswind on runway track. On a 10° offset, that’s down to cos(70°)=34.20%, that is a 31.6% relative reduction.
ELLX

WhiskeyPapa wrote:

A big issue is gusting or not. A steady wind is much easier to deal with than gusts.

Also in gusts, the wind direction usually turns clockwise (in the Northern hemisphere) so it is better to have a gusty crosswind from the left than from the right.

ESKC (Uppsala/Sundbro), Sweden

A big issue is gusting or not. A steady wind is much easier to deal with than gusts. Another factor is the effect of terrain and changes on speed as you get closer to the ground. Higher winds amplify the variables…

Tököl LHTL

Peter wrote:

The max demo crosswind number is even less relevant for departures, not least because, with a big runway, you can depart on a slight diagonal.

More to do with the airflow over the rudder is higher on takeoff (in conventional single) with the propeller slipstream giving much better rudder authority (hence why pilots who are unfortunate enough to ground loop a tailwheel plane tend to do it on landing not takeoff).

Angling across the runway unfortunately won’t do much (unless the crosswind is so strong and the runway wide enough that you can just take off across the width!) The crosswind reduction varies with the cosine of the offset angle you can use (where taking off exactly on runway heading would be a 0 degree offset). The cosine doesn’t change much until the angle starts getting above 30 degrees (e.g. if you angled 10 degrees across the runway, which is quite a lot, the crosswind component you have at the start of the takeoff roll would be 0.98 times the reported crosswind, so it’s not a reduction that’s going to be noticeable).

Last Edited by alioth at 20 Jan 10:08
Andreas IOM

My crosswind limit depends on my crosswind currency, and also the runway surface.
Bumps on a grass runway reduce the crosswind acceptable.

Maoraigh
EGPE, United Kingdom
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