Archive of the categories: Aviation Weather

Understanding IFR Weather: AWOS-1, AWOS-2, and AWOS-3


I know for the instrument checkride next month I will be asked about the different types of weather reporting. This is important to know, because as a pilot, you need to be able to not just interpret the weather, but also know what types of weather reports you need. At KCRQ (Carlsbad), there is an ATIS. At KOKB (Oceanside), there is an ASOS. F70 (French Valley) has an AWOS-3. So what’s an AWOS?  AWOS stands for Automatic Weather Observation System. It is a unit that measures and reports local weather at an airport to pilots.

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There are four basic levels of AWOS: 

  1. AWOS-A: Reports only the altimeter setting. 
  2. AWOS-1: Reports altimeter setting, wind data, temperature/dew point and density altitude. 
  3. AWOS-2: Reports the information provided by AWOS-1, plus the visibility. 
  4. AWOS-3: Provides the visibility provided by AWOS-2, plus cloud-ceiling data. 

For Part 121 or 135 operators, AWOS-3 is the only type of AWOS that’s acceptable without restriction. 

Instrument Checkride Prep: Reading Aviation Winds and Temperatures Aloft Forecasts

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On the instrument check ride next month, I know the examiner will be asking me about the Wind & Temps Aloft forecast. This is issued 4 times daily for different altitudes and flight levels.  The format is DIRECTION – SPEED – TEMPERATURE. If it says 9900 then that means light and variable. Wind direction is from true north, according to

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Things get a little tricky when the wind is is about 100 or 200 knots. Just remember “Between 51 and 86.” 

When the wind speed is 100 knots or greater, wind direction is coded as a number between 51 and 86. And then you subtract 50 from that number – that’s your direction. And then you add 100 to the second set of numbers. That is your wind speed. Let’s practice: 


  • Direction (75-50) Winds coming from 250°
  • Speed (19 + 100) 119 knots  

Above 24,000 feet, the temperature is assumed to be negative. If this forecast was issued at 34,000, you would assume the temperature to be negative 50 degrees. 

Let’s try another one, from tonight’s forecast

At 39,000 feet over SAN: “771357” 

  • Direction=  (77-50) winds coming from 270°
  • Speed = (13 + 100) 113 knots 
  • Temperature = -57 degrees

another one, just for fun. at 39,000 feet over BLH: “761358” 

  • Direction= (76-50) winds coming  from 260°
  • Speed= (13+100) 113 knots 
  • Temperature -58 degrees 

All levels through 12,000 feet are true altitude (MSL). The levels 18,000 feet and above are pressure altitude. 

Instrument Checkride Prep: Reading and Interpreting the METAR

I’m taking the instrument check ride next month and I’m going to be blogging nightly on different topic in preparation for all of the stuff I think will come up on the oral part. I am preparing for lots of aviation weather talk, so at least the next week will be over those topics. I will have to explain things like the difference between a stable and an unstable atmosphere, what standard temperature and pressure values are, and the two basic ways that fog may form. 


One very basic thing I will have to do is hop on and read and interpret a METAR. The first thing I will do is going to and click on METAR – it’s in the upper left hand corner of the website. Then I will scroll down to near the bottom of the page – on the right, where it says “Request Metar Data”, and I’ll type in the identifier of my airport – in this case KCRQ. 

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The METAR reads: Data at: 0358 UTC 23 Mar 2016 KCRQ 230353Z AUTO VRB03KT 10SM CLR 15/10 A3004 RMK AO2 SLP169 T01500100

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 Here’s how I’d read this: Airport is KCRQ, Carlsbad, CA Time – 23nd of March at 03:58 Zulu Time. I convert the time and it’s the 22nd of march at 20:58 Pacific Daylight time. The AUTO, when it appears just after the time group, means that the observation is from an automated station. Winds are light and variable at 3 knots, visibility is 10 or more statute miles, sky is clear, Temperature is 15 degrees, Dew Point is 10 degrees. Remarks: A02 means the station has a precipitation discriminator. SLP stands for Sea Level Pressure, which is another measure of atmospheric pressure. The Last digits that start with a “T” are the he hourly air and dewpoint temperatures to the nearest 1/10 C degree.

Tomorrow night I think I will review the Winds and Temperature aloft chart, and what valuable information can be determined on there, like the most favorable altitude, areas of possible icing, temperature inversions, and turbulence.

IFR Checkride Prep: Alternate Airports and the 1-2-3 Rule

Screen Shot 2016-03-02 at 9.49.08 PMNext month I will be taking my Instrument Rating checkride! I am very excited, not because I have any desire to fly straight into some big puffy clouds, but because it is an important step in my progress of being a more experienced and qualified pilot. I’ve finished two big hurdles already, I have gotten my 50 hours cross country PIC time, including a few solo cross country flights, and I’ve passed the FAA written exam. I’m also about half way through the commercial ground school. I was planning on taking that written exam before the Instrument checkered, but I’m not sure if that will happen yet. In any event, I will be studying aviation every night. 

One question that I anticipate coming up on the checkered is “How do you know if you’ll need to list an alternate airport on your IFR flight plan?” And no, it’s not acceptable to just say, “I’ll list one anyway, just to be safe.” The examiner is going to give me a weather forecast at an airport and I’ll have to tell him whether or not I need an alternate. I will refer to the 1-2-3 rule of IFR flying. It’s pretty simple. 

From ONE hour before to ONE hour after your planned ETA at the destination airport, the forecast has to be at least 2,000 foot ceiling and 3 mile visibilities. If those weather minimums are met, than no alternate airport is required. But if the ceiling or visibility is less than TWO thousand feet and THREE miles, then you need an alternate. And there are some rules about your alternate, depending on the available instrument approaches. 

If an IAP is published for that airport, you must be able to land at the alternate minimums specified in the procedure, or if none are specified: 

(1) for a precision approach procedure: ceiling 600 feet and visibility 2 statue miles. 

(2) for a non precision approach procedure, ceiling 800 feet and visibility 2 statute miles. 

(3) If there is no instrument approach procedure published for your alternate airport, the ceiling and visibility minimums are those allowing descent from the MEA, approach, and landing, under basic VFR. In class Echo airspace below 10,000 feet MSL, basic VFR is 3 statute miles visibility and cloud clearance of 500 feet below, 1,000 feet above, and 2,000 feet horizontal. 

Instrument Checkride Oral Portion Prep: Explaining Wind Shear and How to Handle It

I’ve been busy preparing for the instrument checkride. I did well on my private pilot checkride, but this time I want to be even more prepared, so I will be less nervous. I’m going to start tackling subjects that I anticipate will be on the instrument checkride. Here is a video I made about wind shear, what it is, and what I will do if I encounter it.

YouTube Playlist Specifically for Studying for the IFR Written Test

I’ve been busy studying for the IFR written test, which I plan to take in the next month. When I took the Private Pilot written test, I found it helpful to listen to test questions while driving around in my car. There were some good apps for this, but I nothing on Youtube. For the IFR written, I’ve decided to make my own study guide, and publish it on YouTube. I’ve been putting questions together on a YouTube playlist. I cover everything from hazardous weather to aircraft icing, airport signs to gyroscopes. I’m trying to add videos daily. Some of the questions are “easy” and some are harder. I do some questions that are challenging to me, and some questions that I think might help others. Check it out!

Understanding Pressure Altitude and Density Altitude

At my next stage check, I know I’m going to have to explain pressure altitude and density altitude. And when I become a CFI I’m going to have to teach other people what they are, so I need to learn it. And understand it. And most importantly, be able to explain it. Thank goodness for Youtube videos, I can get some free education that will supplement everything I’m paying to learn at Pinnacle.

Pressure altitude is simple – it’s what you get when you dial 29.92 in your altimeter.

Density altitude is pressure altitude corrected for temperature and humidity. Or, pressure altitude corrected for nonstandard temperature. Another way of thinking about density altitude is this: Density altitude is the altitude the airplane feels like it’s at.

At some point my examiner is going to ask me to calculate density altitude. I know there are two pieces of information I need to figure this out. Pressure altitude and temperature. I can get the temperature right off the thermometer. I can find the pressure altitude by setting the altimeter to 29.92 and reading the altitude off the altimeter. Another method of calculating pressure altitude: take standard pressure, subtract the current pressure, multiply it by 1,000 and add the field elevation.

If you don’t have a flight computer, or an E6B, you can find density altitude using this formula:

Density Altitude = PA + (120 x (OAT – ISA Temp)

PA = 120 x (Outside Air Temperature – Standard Temperature (always 15))

In the wintertime, when it’s cool, and especially near sea level, density altitude isn’t really a big deal. In the summer time, when it heats up and air is humid, density altitude can be a big deal. Not so much here in Carlsbad, but in other areas, particularly high elevation areas where it gets hot, density altitude is very important. Remember, a high density altitude is NOT a good thing.

A surprisingly accurate rule of thumb (usually any error will be less than 200-300 feet) for determining the density altitude is easy to remember. For each 10-degrees Fahrenheit above standard temperature at any particular elevation, add 600 feet to the field elevation. (And, conversely for each 10-degrees F below standard temperature, subtract 600 feet from the field elevation.)

Example: It is 79 degrees Fahrenheit at Carlsbad, so that’s 20 degrees about standard temperature (standard temperature is 15C/59F) Add 1200 feet (600×2) to the field elevation of 330. Density altitude calculated by the rule of thumb method would be 1550. Using the 29.92 barometric pressure calculated on a flight computer, density altitude would be 1,673. So, pretty close.

Understanding True Course, True Heading and the Wind Correction Angle

I am prepping for cross-country and beginning to think everything would be easier if wind didn’t exist. When you’re planning your route, you have to constantly correct for wind. And this involves something called the wind correction angle. It is the difference between the magnetic course you want to fly, and the magnetic heading you actually fly. In order to stay on course to a point, you need to compensate for the effects of the win, and steer the nose of the airplane into the wind. We use our E6B flight computer to find the effect of the wind in regard to ;

Groundspeed (rate of airplane’s progress over the ground)
Airspeed (rate of airplanes progress through the air)
Drift angle (angle between course heading and track)
Heading (the direction in which the nose of the airplane is headed)
Course (the intended path of the airplane over the ground).

Using the wind correction angle and your E6B flight computer, you can convert your true course to your true heading, and also find out what your ground speed will be for your flight. So again in summary, the difference between the magnetic course and the magnetic heading is the wind correction angle.