# Trying to understand

Hello!

Trying to understand a few concepts. If the runway is named 9, and the METARS show the wind as 090, would you land on 9 or 18? When the METAR show the wind as 090, if you faced towards the east would the wind be in your face or behind you.

I unerstand if the questions seem to be common knowledge, I want to make sure I understand the concept.

Thanks,

Jeff

Winds are reported as the direction they are coming from, ie the direction you would be facing to feel the breeze on your face. Another way to think about it is if the windsock were above a compass rose, the wind is reported based on the compass heading where the mouth of the windsock currently is. Therefore, if the wind is reported as 090 you would land runway 9. In that example the wind is moving from the east to the west. The plane almost always is landed into the wind to minimize ground speed at landing (and minimize roll on take off), therefore runway 9. And, just to be clear, runway 9 would be a runway in which the landing plane would be on a roughly 90 degree heading to land on. Runway 27 would be the opposite landing to the west, (not runway 18 as you mention above as there are 360 degrees in the compass rose, so half of that is 180 degrees so the reciprocal heading of 90 is 270).

Thanks for the speedy response and great answer. Obviously I didn’t proofread my question, or I might have caught my error in the reciprocal heading.

Thanks!

Jeff

Furthermore, both runway number and METAR report directions, but runway is magnetic and winds are relative to true north.

Runway 09 goes to heading 090 magnetic.

METAR 090XXX comes from true heading 090.

Depending on your magnetic variation, not likely to be a significant difference, perhaps +/- 15-20 degrees in the US.

So, METAR 090005 would be a light 5 knot headwind closely aligned with landing on runway 09.

Cheers
Rick

BUT - wind direction as heard on ATIS/AWOS/ASOS is relative to magnetic north. So if you are hearing the winds while in flight, they should be aligned using the same basis as runway numbers. If you are reading the winds from DUATS or similar, they will be referenced to true north.

See how simple this is? [;)]

Rick:

What you are saying is only true for winds aloft. Surface wind reports are magnetic. So if the wind is reported at 090 degrees, that wind will be right down the runway.

Brian,

Surface wind reports when read in METARs and TAFs as displayed on DUATS, for example, are true. They are only magnetic when “read” over-the-air via ATIS/ASOS/AWOS report, as per my previous post…

Winds aloft are always true, as you describe.

Steve,

I don’t doubt that you are correct, but it’s the first time I’ve heard that explanation. What’s the authoritative source?

And just a practical application, the Metar that you read on your MFD via data-link is true, and may differ quite a bit from the ATIS (Magnetic) depending on your variation. This is most important when understanding which runway to expect when you have what appears to be a perfect crosswind to your destination airport. I seem to have a special talent for finding crosswinds at my destination [:(]

Jim,

Hey, this is an internet forum. It’s no fun if we have to back up our statements with authoritative sources! [;)]

This is the best I could do. For METARs and TAFs being in true, Chapter 12 of the Pilots Guide to Aeronautical Knowledge (an official FAA publication) says about METARs: “The first three digits indicate the direction the true wind is blowing in tens of degrees.” and about TAFs: "The first three indicate the direction of the wind in reference to true north." (my emphasis).

As for ATIS being in magnetic, section 4-1-13 of the AIM, says “ATIS information includes the time of the latest weather sequence, ceiling, visibility, obstructions to visibility, temperature, dew point (if available), wind direction (magnetic), and velocity, altimeter, other pertinent remarks, instrument approach and runway in use.” Section 7-1-2 (b) of the AIM describes AWOS and there’s a note that says "Wind direction broadcast over FAA radios is in reference to magnetic north."

Additionally, section 4-2 of the AIM, called “Radio Communications Phraseology and Technique” has a section, 4-2-10, which says “The three digits of bearing, course, heading, or wind direction should always be magnetic. The word “true” must be added when it applies.

So I think that, in general, what I said was true - if you hear it on the radio it’s magnetic and if you read it on paper, it’s true. But it’s more of a “rule of thumb”, or an easy way to remember things, than some iron-clad guarantee. I’m sure if you searched hard enough, you could find SOME kind of written weather product in magnetic direction; I’m mainly talking about the commonly used ones.

And as a quick note to Jeff (the OP), let me apologize for all of us, but especially myself, for taking such a straightforward question and twisting it into a long-winded explanation. Peter’s answer was best. If you hear winds 090@10, land on runway 9, not 27 or 18! [:)] Don’t worry too much about the rest of this stuff!

As others have said, wind direction is always the direction from which the wind is blowing.

If it helps, think of a Nor’easter. Strong winds from the northeast.

Also worth mentioning is that on charts, the barb also shows the direction from which the wind is blowing. I know this, but can still get a little dyslexic from time to time*.

That legend was the easiest one to find and link to, and doesn’t exactly match the “barbs” on aviation charts, but you get the idea.

*not helped by the fact that its easy to misinterpret them if you imagine them as little wind socks!

Yeah, it’s an oldie, but a goodie…

!(http://www.bowkera.com/images/Wyoming/Casper Friends/WYOWINDSOCK.JPG)

My question was fully answered, and I have enjoyed reading all the posts, learned a lot.

Another question, if I may. Say you are VFR without a flight plan, landing at an airport with two runways about 70 degrees difference between the two, and one end of each runway in close proximty to the other runway. What is the procedure if you are instruced by the air traffic control tower controller (sorry, not sure of the proper terms) to land on runway “A”. but you mistakenly set up for runway “B”, and the controller notices this, instructs you to land on runway “A”? I would guess it depends on how busy the airport is, how close you are when you discover the mistakeIs and other variables. Are there times when traffic on runway “B” would create a hazard if you tried to land on “B” or perform a go around on runway “B”, rather than try to recover from your mistake and land or go around on runway “A” pattern?

Thanks for all the information, I have learned a lot.

Jeff

Call your attorney, and/or your insurance carrier, depending upon some variables not mentioned here, and BTW, don’t forget to cancel your VFR flight plan when you land.

Jeff:

In your example the control tower would be managing the traffic on both runway A & B. If there is no control tower, everyone in the traffic pattern should announce where they are; you shown acquire that traffic and watch what it is doing (such as you do in your car) and you land on the runway that does not conflict with other traffic.

If the runways are 70 degrees from each other, this should not be a problem at all if you are watching your heading when you are still 2 miles out from the runway. Your heading will be very far off what it should if you are approaching the wrong runway. Looking early enough gives you plenty of time to correct.

Jeff,

If both runways are in “close proximity” then turning 70 degrees to line up with “A” shouldn’t be too difficult. But if on short final that kind of low speed maneuvering could be dangerous and saving the landing is not appropriate. Two miles out it should be easy, you go from a 2 mile final to a 2 mile base and turn the appropriate direction. But in either case it should not be hard to power up, level off, turn the 70 degrees, clean up the plane, then initiate a climb and finally declare a go around on the runway you were assigned - IN THAT ORDER. Always fly the airplane first. I think it would be inappropriate to try a go around or landing on runway B at this point. However it would not be wrong to ask if you can change to runway B. If they say no then you are reasonably assured there is a conflict and you need to immediately do what I suggested above.

Low speed/altitude maneuvering has deadly consequences and happens too frequently. BTW, I learned a long time ago (don’t ask why [:\$] been there, done that - it is easy to do) when assigned a runway to validate my heading on the HSI or DG matches the assignment - or at least the situational awareness matches (ie I am on downwind and the runway assigned is at the bottom of the HSI, or I am on left base and another left turn puts the HSI on the runway heading). That will keep you from lining up on a 70 degree error runway, but won’t help much on a parallel runway [;)]

Right questions, keep learning. When you stop learning its time to hang up your wings.

In another thread I just posted this technique of using the Garmin 430 to paint an extended centerline onto your moving map to align to the runway:

A generalized technique for any runway at any airport is to select the airport in the flight plan, hit the “Direct to” button ONCE, and then, in the Direct to screen that will be displayed, use the big knob to select the “CRS” (course) field and enter the runway heading (e.g. 230 for runway 23), then press Enter. That’ll put the extended paint stripe out there to follow.

For extra credit, select the bearing pointer on the PFD (2nd button on left side) and source it to the 430 you did the Direct to on, and now you have a bird dog pointer to the airport as well. I do this for all VFR arrivals.

Great picture Gordon![:)]