METARs report true wind but runways are magnetic? Huh?

kicktireslightfires

kicktireslightfires

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kicktireslightfires
METARs report wind true, right? But runways are magnetic? Doesn’t that mean that if a METAR says the wind is 200 and the runway your landing on is 180, it’s not actually 20 degrees of wind difference? You actually need to also calculate the magnetic variance in order to know the true number of degrees the wind is running relative to the runway? Are there any fast tricks for doing this?

So before I even pull out my E6B or crosswind chart to calculate the crosswind, I need to first find the magnetic variance and then add or subtract that -- based on the direction the wind is traveling -- from the METAR wind reading?

Am I overthinking this and there's a simpler way?

Thanks in advance!
 
You could look at the windsock or any smoke/steam in the area to get the wind direction and compare that to the runway heading (which itself may be off by 5 degrees). My opinion is that precision in wind direction is rarely important. You need a general idea so you can pick the right runway, then you do what it takes to fly the airplane off of or back to the ground.
 
Yes, you have it right. Metar is true, atis is magnetic.

There is an easier way and that is to ignore the variance unless you’re somewhere where the variance is large. There just isn’t that much difference in 10 degrees of angle.
 
bflynn said:
Yes, you have it right. Metar is true, atis is magnetic.

There is an easier way and that is to ignore the variance unless you’re somewhere where the variance is large. There just isn’t that much difference in 10 degrees of angle.
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Yeah, that.
 
What you read in the METAR (true) back when you got your briefing or when you're enroute and looking at the ADS-B weather is nice but aren't you going to get the ATIS/AWOS (magnetic) before landing? The most current information before you're on the runway has the format you want. Who cares whether some hour-old information was 20 degrees off? The wind can shift by 20 degrees in that time anyway.
 
I suspect the OP is having to do the exact calculation as part of flight planning training exercises to compare with the published demonstrated maximum crosswind capability of the airplane...before setting out.
 
If you get really concerned about the crosswind component with a magnetic variance of +-2 or +-3, as a student pilot, or ANY pilot for that matter, the next thing in your head should be "No Go for 1000 Alex!"

The actual crosswind delta will be a couple of knots at best.

Sent from my SM-N986U using Tapatalk
 
Iceman21 said:
If you get really concerned about the crosswind component with a magnetic variance of +-2 or +-3, as a student pilot, or ANY pilot for that matter, the next thing in your head should be "Find an instructor for 1000 Alex!"

The actual crosswind delta will be a couple of knots at best.

Sent from my SM-N986U using Tapatalk
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Fixed. ;)
 
kyleb said:
You could look at the windsock or any smoke/steam in the area to get the wind direction and compare that to the runway heading (which itself may be off by 5 degrees). My opinion is that precision in wind direction is rarely important. You need a general idea so you can pick the right runway, then you do what it takes to fly the airplane off of or back to the ground.
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so we’ll put, especially for practical flying.

on a recent long trip in the ol Cessna 140 winds were very stiff but called for right down the runway, AWOS said the same. We land and it was one of the rare ones I’m happy with and I look over and the windsock is 45 to the runway. I guess my crosswind capabilities are higher than my max preference :)
 
Remember, too: the runway number is chosen to the closest increment of 10 degrees. So theoretically the runway could have an actual direction of 265 and be marked 26 or 27. If you really wanted to be picky, I suppose you could have a look at the approach plate for the S-ILS if there is one and base your crosswind calculations from that course. But the reality is, eventually you just want to know which side the crosswind is coming from and how hard it's blowing. Your superior skill as an aviator will take care of the rest
 
Aileron into the wind, opposite rudder. It really is that simple.

Search around and I too was over thinking crosswinds - completely. But at the end of the day, the more you do them, the more you realize it’s all about technique than any kind of in-flight mental math (obviously the crosswind component has to be within the limits of your plane).

Last week, I did my first 14G22 *direct* xwind landing in a 172. Nailed it!
 
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Just move & fly to the Midwest, where that ‘0’ line is, problem solved.
 
Trogdor said:
Last week, i did my first 14G22 *direct* xwind landing in a 172. Nailed it!
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Nice! They don't have to be greasers either. In fact, I prefer to land just a little firm and under control vs trying to make it smooth and spending more time in a nose-high attitude near stall when it's gusty. Just plant the dang thing on the centerline and make it quit flying.
 
There’s a couple of issues here.

1). What is my crosswind component, I need to know for an administrative requirement?

OP is exactly correct. Convert everything to magnetic, (true virgins make dull companions at weddings is the memory aid), go to your e6, calculate precisely, apply administrative criteria.

Even in 757s there is a limit. It’s in knots, to the nearest knot. Say 25 kts. 26 is not legal. 25 is legal. Therefore you should apply everything to be accurate to a knot. It matters. It’s not a safety thing, it’s administrative.

Anecdote, one day in Orlando, bunch of us sitting at end of runway, same planes, different carriers, different limits. Direct crosswind, easy math... Tower would ask next guy for takeoff what his limits were, and magically with the gusts in a few moments he would revise the observed winds, report them on the recording, said next guy would ask to take off. Lather rinse repeat. Such is the nature of administrating safety.

2). What are the winds, I WANT to go flying?

Relying solely on reports is probably the unsafest thing you can do. Go observe, apply common sense with due diligence. Evaluate your experience, revise personal criteria. End of story.

Tools
 
True - degrees true
Virgins - variance
Make - magnetic
Dull - deviation (instrument specific)
Companions - compass heading

At Weddings - add west (if variance is west, add to true, if east, subtract from true).

For this wind calculation, simply stop at Make (or magnetic). This memory aid is what ship drivers use to convert degrees true on a chart to the actual heading they need to steer. Ship drivers have VERY precise “compass swing cards”. That’s where the deviation comes in.

The opposite is Can Dead Men Vote Twice At Elections.

Tools
 
Oh to really get you confused I think “Wind checks” are magnetic if I recall correctly....
 
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