As a Clemson University professor, it has been my privilege to help hundreds of students prepare for the Part 107 knowledge exam. Invariably, I get asked the proverbial student question, “Why do I need to know this?”. The vast majority of the time, there is a very good reason why the FAA choose to include it. Sometime, I’m stumped. The lapse rate of 1” of pressure every 1,000 feet. Are you kidding me? How many thousands of feet do they expect us to be flying our drone? A common question I get asked about is the METAR and TAF weather forecasts. Why do I need to know that when you can get the weather from a million other sources? Well, my friends, let me give you two reasons and a simple hack to make the METAR and TAF an everyday useable tool.
How High Is that Low Hanging Cloud
First, one of the Part 107 rules is that you can’t fly your drone within 500 feet of the underside of cloud. Very reasonable regulation as there could be a manned aircraft in the cloud that you can’t see. The problem is, how in the world do you estimate the altitude of a cloud? That information is not provided with most weather apps or forecasts. The answer is the METAR and TAF. The METAR below from LAX indicates that we have scattered clouds at 700 feet. That means our ceiling is 200 feet to maintain the 500-foot buffer.
METAR KLAX 121852Z 25004KT 6SM BR SCT007 SCT250 16/15 A2991
Now, did you remember enough from your Part 107 exam prep to glean that information from the METAR? Most people wouldn’t. Don’t worry, METAR hack is coming later in the blog.
Documenting Cloud Cover for Solar Panel Inspections
Second, one of the leading use cases for drones is inspecting solar panels with aerial infrared imagers. I can spot a downed panel at 150 feet, and there are a lot more arrays in suboptimal service than you would think! With that said, according to IEC 62446-3, you can only have two oktas of sky covered by clouds. The “okta” is a unit of measure for cloud coverage in units of eighths. An okta of “four” would estimate that four-eighths of the sky is covered. If you remember from your Part 107 prep, the abbreviation of “SKC” meant sky clear (0 oktas) and “Few” meant few clouds (oktas between 1 to 2). If you’re inspecting a solar array, you absolutely need to document that cloud condition, or your report is meaningless. Checking to ensure you see a “SKC” or “FEW” in the METAR from the closest airport is the easiest and defendable way to do that.
Easy Hack for Getting and Decoding the METAR and TAF
Fortunately, Leidos Flight Services, thru 1800wxbrief.com can give us an easy way to have the METAR and TAF texted to us in plain text format. Using the number 358-782, text M, space, then the four-letter airport code. They will text right back the METAR at that airfield. Now, text M, space, then the four-letter airport code, space PT. That will give you the METAR in plain text. You can do the same thing with the TAF by typing “T” instead of “M” in the text message. I’ve given you four examples to try using the local airport near Clemson University.
· M KCEU
· M KCEU PT
· T KCEU
· T KCEU PT
I have METAR programmed into my phone as a contact with local airport codes saved as notes. That makes it very easy to call up the information in the field and store it for documentation in my reports later. This is just one example of the type of tips I provide in my courses offered through Clemson Drone. Safe flying everyone!