Category Archives: Weather

Gliders, Snow, Soaring, Weather

Soaring in the snow

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I have been very fortunate to have met some great people soaring in England. I’ve had the pleasure of flying with three different clubs. Over a recent long weekend, I had arranged to visit two of those clubs and work on aerobatic flying. My four-day trip did not go exactly as planned, but this is not about that or aerobatics even.

I’ve often admired the English countryside with hedges dividing fields of many different shades of green. This time, the hedges outlined fields of white snow.

The first day at London Gliding Club (LGC) I was found safe to practice solo aerobatics the next day (Note, “safe” is not a synonym for “good” or “proficient.”) When I went to bed, the forecast had potential. When I got up the next morning, the real world had snow!

The tow plane is from a company called Avions Robin in France. I visited the factory once in 1987. The LGC clubhouse and hangar are visible just above the cockpit.

At the glider field I spoke to the tow pilot who told me he was getting freezing mist on the canopy at 4,000 feet. The sky was completely covered, with little to no horizon. It’s hard to do aerobatics in the clouds. No visible horizon doesn’t help either. Aerobatic flying was out, but I heard someone say, “There’s wave over Tring Road.” I know where Tring Road is!

The wing runner has the tow rope, ready to connect it. Two more crazy people ready to fly. The glider is an ASK-21, the most common training glider in the world.

I added myself to the launch queue and waited my turn. I asked instructor Alan Harrison if he would go with me. Even though I had flown the day before, flying with heavy clouds in the air and snow on the ground was something new for me. “New” started with the takeoff’s ground run.

Most of my friends think I’m pretty crazy, but look at this, I am nowhere near alone in trying to fly. Ready to go, too? Ridge in the background.

Important background: 1) gliders are normally airborne before the towplane, 2) LGC’s runway is described as “undulating” grass, and 3) any takeoff is longer on snow/mush/etc. The takeoff run at LGC starts down a long slope, does up then down a short slope, then up a longer one. The tow plane rolls over the crest of the middle hump, with me already in the air. I can’t get too high without putting the towplane at risk. He’s rolling down hill as I’m flying up. However (There’s always a “but” or a “however”!) the ground is going up faster than I am. Bump! I’m back on the ground and roll over the hump, back in the air again. This, of course, put a brief, but noticeable load on the tow plane – further lengthening the takeoff run.

Looking at Dunstable from about 2,000′. The glider field and ridge are are on the other side of the glider. This is about where we found the best lift.

Finally we’re both in the air. Motors and wings perform well in the cold. We climb to 3,000 feet and release in light wave. For the most part, there is only enough energy to reduce sink from a typical 2 knots to about 0.5kts. Even if we’re “only” going down more slowly than usual, that’s a good thing. Woosh! Glider pilots know the feeling of upward acceleration when entering a thermal. Alan and I felt a strong upward shove as we found real lift. We worked hard to keep ourselves well within that lift for several minutes. You already know where this wave was, right? Yes, right over Tring Rd.

Diagonally across the picture you see the Chiltern Ridge that LGC is famous for. Centered is the takeoff/landing area.

The view from the cockpit was incredible. I’ve often admired the English countryside with hedges dividing fields of many different shades of green. This time, the hedges outlined fields of white snow. And, my iPhone was inaccessible in my pocket. Thankfully, Alan had his phone and took several pictures.

The northern end of Chiltern Ridge has a hook or bowl. I actually hovered over this spot once, matching my airspeed to the speed of the wind, giving me a ground speed of zero.

Many thanks to Chief Flight Instructor and manager Andy Roch for hosting me and to the fine instructors who flew with me.

PS The wind came from behind the ridge and down its front. I suspect this was an example of “hydraulic jump” where the wind actually ricochets off the ground and back up. You see this with water flowing over a dam or spillway.

London Gliding Club viewed from the top of the ridge. The “undulation” in the takeoff run i clearly visible.
Weather

10 great online weather tools you may not know about

[This content is courtesy of John Zimmerman at Air Facts Journal.]

All pilots are required to conduct a weather briefing before each flight, whether that means calling Flight Service or looking up the weather online. But for true weather geeks, a pre-flight weather briefing can be a lot of fun, not just a requirement to be completed as quickly as possible. And for pilots looking to go beyond the basics, there is a wealth of information online with details about ceilings, visibility, turbulence, icing and more.

G-AIRMET

Everyone has their list of favorite weather sites. Here is my top 10 list of useful weather websites that aren’t as well known as they should be (and they’re all free):

1. Graphical AIRMET tool
AIRMETs have a well-deserved reputation for being fairly worthless. They are hard to understand unless you can see them on a map, and they often warn of turbulence over half the country. But this new tool rescues the AIRMET from the trash bin, with some nice enhancements to the classic product. For example, you can quickly overlay multiple AIRMETs (low level turbulence, high level turbulence, icing, etc.) on the same chart, and you can view predicted AIRMET coverage areas about 12 hours into the future. It’s a nice way to view the trend, so you can get a feel for whether conditions are improving or deteriorating. It’s also easy to hide AIRMETs that don’t affect your flying (for example, high level turbulence if you fly a Cessna 172).

2. TAF graphics.
The Terminal Aerodrome Forecast (TAF) is a valuable product, and is used by pilots of all levels. While the text has all the important details, sometimes a visual depiction of TAFs can offer clues about how widespread low ceilings are or what the trend is for low level winds. The TAF graphic makes it easy to view this information on a single chart, at three hour intervals in the future. You can also look at a single weather features–clouds, weather conditions, forecast winds and wind gusts–over time. This is an experimental product right now, and you’ll want to read the actual TAF for complete details, but there is a lot of information here at a glance.

3. Medium range forecasts.
Most aviation weather sites show the prognostic charts, with high/low pressure centers and fronts, up to 48 hours out. But sometimes you want to get an idea about the weather further out than just two days. That’s where this site, from the National Weather Service, comes in. It offers 3-7 day forecast graphics on a simple-to-use page, and you can even loop the images. The further out a forecast goes, the less reliable it tends to be, so you’ll want to use these charts as a general guide. But for long trips a few days out, I’ve found this to be a helpful tool.

4. CWSU national map.
This map is my favorite all-in-one tool for looking at surface weather trends. This nationwide map graphically shows all METARs, including ceiling, visbility, cloud cover, wind direction and speed and other data. You can mouse-over a station for current weather conditions and the TAF. Clicking on a station brings up an detailed page with the last 24 hours of weather information, including some graphs. This is an invaluable tool for VFR pilots planning cross-country flights, and even IFR pilots when faced with low visibilities. It’s a great way to find an alternate airport, too.

5. Historical METARs.
Have you ever completed a flight and wondered a few days later what the weather really was? Or maybe canceled a flight and wished you could see how it really turned out? This site, definitely for the real weather geek, has METARs archived all the way back to July 30, 1998. You pick the state, the date and the time and you’ll get a list of the METARs at that time. This isn’t really a pre-flight tool, but it’s an excellent way to learn about weather and improve your own forecasting.

Ceiling and visibility chart

6. C&V chart.
This is a slightly different take on the graphical METAR idea. Here, the chart tries to fill in the blank spots between airports, so instead of station plots you can see wide areas of ceiling and visibility restrictions. This is obviously an educated guess, but it can give the VFR pilot a reality check on low weather days, especially when METARs are widely scattered.

7. Skew-t/log-p charts.
Skew-t plots are where serious weather geeks really get excited. They are certainly not easy to read, and I wouldn’t argue that they be part of every pre-flight briefing. But they are educational and can offer some important clues for pilots, especially if you’re interested in convection or icing threats. The Skew-t chart, among many other things, shows the temperature, dewpoint and wind speed at different altitudes. With some practice, these graphs can reveal how stable the atmosphere is, where wind shear may exist and even how thick a cloud deck might be. There are a number of websites that provides Skew-t plots, but the RUC Soundings site from NOAA is the most powerful. You can view forecast Skew-t/log-p plots, and center it on an airport by entering the identifier. Be sure to click “Java-based plots” for the most full-featured display.

8. Full resolution looping NEXRAD.
Probably every pilot checks the radar before flying, and there are plenty of options for this. But this site is the full resolution image from NOAA, and it shows the entire country (you can even loop the image). It’s a big page, but it’s a fantastic look at the latest picture, and my go-to during thunderstorm season. You can also click a location on this big map for individual NEXRAD site radars, where you can compare base and composite reflectivity. On this map, you can click for the lat/long, which I’ve found to be helpful for flight planning around airspace.

9. Turbulence and icing forecasts.
The threat of turbulence and airframe icing are usually high on the list of concerns for pilots. Up until a few years ago, the only way to plan for these events was to combine PIREPs, area forecasts and a healthy dose of gut feel. But the Aviation Weather Center website has recently added some great new forecast tools. They both operate similarly, allowing you to view the probability of ice or turbulence at different altitudes at different times in the future. These are obviously models, but in my experience they are quite accurate (especially the icing tool). If you canceled every time there was a cloud deck and the temperature was below freezing, you would never fly in some parts of the country. This tool allows you to make a better plan, potentially changing departure time, route or altitude to minimize your exposure. PIREPs are still piece of the puzzle, but these charts can add more detail.

Flight Path Application

10. Flight Path Application.
This is really a downloadable Java application, not a website, so it’s definitely for power users. But for education or serious flight planning, it has some unique features that can’t be done in a web browser. You can enter your route of flight, then view different weather products along your route. You can also see a profile view of your flight, including the graphical icing forecast (above), allowing you to choose the right altitude quickly and easily.

To stay up to date on the latest weather tools from NOAA, check the ADDS website occasionally. This is the place to preview new products that aren’t ready for full deployment yet, some of which can be very handy for flight planning.

On top of these great websites, there are some fantastic iPad apps if you’re a tablet user. I’ll save that list for another article, but I will mention that RadarScope is my favorite app when it comes to serious weather watching.

What’s on your list?