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Why we should stay out of the air today

by Had Robinson

Earlier today (April 10, 2013), I had this discussion with our RGSA Safety Officer, Robin Hastings, why pilots might want to stay on the ground.  Be sure to also read the Introduction to Weather in the Southwest if you have not already. 

Do we want to get hurt, wreck our equipment, or have something worse (!) happen?  It is extremely important that we understand the weather in our region.  It is some of the most dicey air in the world because it can change so RAPIDLY and/or be completely different just a few hundred feet up or down or a mile or two in one direction or the other.  One minute the air is a pussycat.  Then, in seconds, it can be brutal.  For this reason, pilots who learn how to safely fly in the desert southwest have the tools that can enable them to fly anywhere in the world.

Here is a report from an experienced pilot who was flying in Colombia during the 2015 season. She personally discovered why studying the weather can prevent an accident.

Colombia was actually very rowdy this year, with a lot of accidents and one death. I had to throw my reserve the first flight of my first day, heading north towards La Union. I was a couple hundred feet off the ground when I hit the bad air and my wing took two huge collapses on opposite sides and went into a spiral. I threw the reserve and hit the ground 4 seconds later. I had a badly bruised heel and slightly sprained ankle--and I credit my Hanway paragliding boots for saving my bones. My wing was fine and we were able to repack my reserve and I flew the rest of the week, but it wasn't as enjoyable as I had hoped, and the realization of throwing the reserve kind of came in waves afterwards. I have never thrown in 8 years. Everyone said the drought is creating volatile conditions. Water for the city was turned off every day from 2-7pm. There were still lots of low clouds but not a lot of rain in the Roldanillo area. We also got to fly Pietachichu which I thought was beautiful. A fast storm blew in after we landed and two tandem paragliders actually launched into the approaching squall! They really got it handed to them, and right over the buildings--they barely made it with their lives and their passengers. It was unbelievable that they would choose to do that.

Why is our air so fickle and potentially so dangerous for our sport, especially for paragliding?  It is mainly because 1.) We are far from the ocean, 2.) We are relatively high in altitude, 3.) We are located in the Horse Latitudes. 4.) We are in the vicinity of mountains and deep valleys.

Briefly, these four factors add up to air that is usually descending (high pressure) which makes for sharp, intense, narrow thermals with rough edges (vertical shear).  Dry air from constant high pressure means few clouds which are a great help in locating thermals when we have them.  Usually, we have to guess where the air is going up.  Lack of clouds and intense sun makes the thermals very strong during the middle of the day.  Being in the Horse Latitudes ensures that winds are often light and variable and can change direction often.  We can be exposed to radically different layers of air in the atmosphere as we fly up through it.  That is, the direction, speed, moisture content, and temperature can be all over the place.  The oceans have enormous thermal mass.  Air that is next to great bodies of water tends to be stable or, at least, predictable, like our southern Pacific coast.  But this is the land of mishmash air.  Without careful analysis or help from our local weatherman, we can put ourselves in danger quickly. For example, this is what a fully inflated paraglider looks like when encountering virga – not a pleasant experience.  Thankfully, the pilot was not cocooned in the glider, there was no cravat, and the glider started safely flying again quickly.  Anything else would have required a reserve toss over mountainous territory – also a less than good option.  The entire event took less than 3 nerve-wracking seconds.

paraglider collapse from virga

Salton Sea Cold Front Event Feb. 11, 2012  Like the southwest, the desert just east of the Sierra Nevada can have sudden weather events that are dangerous to ultralight aircraft.  The pilot below failed to heed clear warnings of a rapidly moving wave of strong air that was moving east across the desert from the Pacific coast.  With help, he was barely able to land without injury or being blown out over water – this time.  Another pilot was, in fact, blown out to sea.  He narrowly escaped drowning.  Both pilots should have landed but chose not to.  Is it "cool" to risk your life?  Many pilots choose to deliberately play a form of Russian Roulette.  The search and rescue team that attempted a rescue of the latter pilot must think ultralight pilots are foolish and careless.  This is not to mention the waste of taxpayer's money that resulted from sending a fully equipped rescue helicopter for someone who did not need any help because he had reached land was having a great time visiting with the locals.

gust front

While flying in the mountains to the northwest of the Sea, I saw the leading edge of this front sneaking in from miles away (dust kicking up).  The heavy, cold air went along the low areas and then spread out.  The mountains blocked the flow and were probably safe but why take a chance?  I landed ASAP.

dust being kicked up by a gust front

Today's Analysis (a sample of what pilots should always do before flying)

The NWS forecast is for some short wave impulses (low pressure waves moving along high in the atmosphere) that are on the tail end of the storm leaving the area.  These impulses cause the air in front of them to go up and cause gusting (forecast is for the effects to start about 9AM).  Things are calm here both in the valley and at the Dona Ana County Airport but it is because of the inversion which will soon be gone by mid/early morning. Conditions northwest of the Las Cruces Airport and further west of us are different. At 7AM, Deming is already west at 7 mph (not bad).

Things would have been flyable from maybe 7am until 9am but it would rapidly become too strong for all but the best PG pilots (west at 15 is forecast by the GFS model by late morning). It is the gusting from the short wave impulses and the Jet that should always concern pilots. It is extremely important that pilots take a look at the hourly weather forecast from the NWS or, at least, read the day's forecast discussion.  None of the models are designed to forecast atmospheric turbulence (gusting) that could be dangerous to ultralights.

So I am flying at 8:45AM and the gusting forecast was off a bit. It could be a concern. For example, I landed late Saturday and got whacked. Just as I touched down the winds took off 18+ or so and I got nicely dragged across some of the grass at the sod farm.  I knew gusting was forecast for the time I was in the air but it was so nice flying around.  As I went up, wind speed increased and there was turbulence – all signs of something strong coming in.  Getting dragged a bit at the sod farm is one thing (easy, no damage, no harm, etc.) but getting dragged anywhere else? It could damage equipment and cause injury. Lee Boone and I both have been rattled by gusting from the Jet, as well. It can happen so quickly and is completely without warning. I was at the top of Mt. Riley in nice balmy air but I wanted to be sure the Jet wasn't going to do stuff (it always does, anyway, but I wanted to be sure) so I waited around. Sure enough, a 35 mph gust came through out of nowhere. If I had been in the air, probably no problem but what if I was setting up for a landing or had been soaring close to the rocks?  I muttered some words and made the 40 minute hike back down the peak with all of my gear.  Why be careless? Those pilots who choose to ignore the weather might be lucky then again.... Today might have been safe for PG for 2 hours or so very early.  But, to be safe, we should get out of the air an hour before the gusting is forecast. That leaves a nervous hour to fly for us. I did not think it was worth it. These impulses combined with the Jet can cascade into a dangerous wave of turbulence which is what I think happened when I was at Mt. Riley.  Air and water are subject to the laws of physics and behave in similar ways.  The ocean coasts are subject to sneaker waves.  These are extremely dangerous waves that can be many times higher and stronger than the average wave coming in.  Many have been drowned by these monsters that appear out of nowhere, even on calm sunny days.

The atmosphere can be the same under certain conditions when the effects of extreme winds (the Jet) and short wave troughs/impulses are present and then combine.  Mixing of these effects can cause the dangerous turbulence which can spit a pilot out of the air.

Conclusion:  Make sure the air is relatively clean and smooth up to 30,000' MSL before flying in it.  This is why the NWS gusting forecasts are so critical for ultralight pilots.  Any pilot who has 100's of hours of flight time can tell you a story of how he was just flying along calmly and, suddenly, without warning got whacked badly out of nowhere.  We need to minimize or eliminate these frightening and potentially dangerous experiences.  That is why we carefully study the weather before flying in it.

Remember that you alone are responsible for determining whether it is safe to fly or not.