Cold weather operations for paramotors

by Had Robinson
updated February 20, 2021 – this page continues to be updated with important, tested information for flying in cold and very cold weather!

Cavanall Mountain in Poteau, OK

Cavanal Mountain in Poteau, OK – temperature was around 5F/-15C.

Launching PG in such conditions is not anything as difficult as launching with a paramotor.  It is hard to move around in the snow quickly and landing can mean falling down.  Always land with the engine off and only fall forward, if you have to fall, which likely will be most of the time.  Launching and landing with a twitchy glider is like being on an ice rink running around with a 50 lb. backpack.

Discussion per engine modifications

(for clothing tips, see the end of this page)

As the temperature drops, the oil in the gasoline gets thicker and does not pass as easily through filters and jets.  Using 100% synthetic oil help with this problem which may lean out the air/fuel mixture.  Additionally, the air/fuel mixture will not vaporize enough in the crankcase to burn well in the cylinder.  Heat is the only way to solve these problems.  Then there is also the possibility of carburetor icing that we must deal with.

Air temperature during a flight (photo below) was 28F/-2C with a 1/2 point spread between the temperature and the dewpoint.  It took less than 5 minutes for the coating of ice to develop.  I could not see the leading edge but I could see my risers and heated gloves begin to accumulate ice.  It was time to land – quickly.  As the cloud ceiling was about 300' AGL, getting down fast was easy.  Despite all of the ice, the glider did not miss a beat as its overall shape did not change but it was rapidly getting heavier which could, in another 10 or 20 minutes, make the glider unsafe to fly.  I have flown gliders that have gotten suddenly wet from a rain shower and the change in shape is apparent as evidenced by sluggish handling and increased stall speed.  I was watching for this and sped up the glider (a reflex model), just to be safe.

paraglider with ice on the leading edge

photo by Had Robinson

These are my latest observations (Feb 19, 2021) and what to do in the cold.  Without spending $100's on test instruments to measure the temperatures of various parts of the engine, a lot of this is trial and error.  When that fails, we spend the money and the time.

The secret of cold and very cold weather flying is make certain that the engine is HOT.  Pilots must do whatever it takes to keep their engines well into the hotter range that they would ordinarily experience during the summertime.

Prior to a flight in freezing weather, I covered up all of the ports on the engine cooling shroud and used some masking tape to hold the choke about 1/3 closed and launched.  Engine went to 3/4 throttle easily.  A few minutes later, during climb out, the engine began to stumble.  I let go of a brake toggle and completely opened the choke.  The engine ran perfectly for the next hour in temperatures below freezing, including a small drop as time went on.  I noticed that the engine temperature was 160C, which is higher than its normal 140C when operating near or above 70F/21C.

Having a hot engine when running in very cold conditions is the answer to cold weather operations.

The hot engine will warm up the carburetor (and the fuel going through it) enough so that the fuel/air mixture will be vaporized enough to burn efficiently in the engine.  At the same time, carburetor icing will not occur.  Vittorazi noted this when we briefly worked together on a military project in a country located in a very cold part of the world.  They removed an insulating gasket between the carburetor and the crankcase on one of their engines which helped.  However, this was a few years ago and I had not yet developed the preheat system which is the only solution for keeping the engine hot.  It is much the same on a carbureted aircraft engine.

From tests, it is clear that adjustments to the carburetor are unneeded if the engine is kept at the right temperature.  I had no way of measuring the carburetor air intake temperature, something that is on the "to do" list.  How hot was the air coming in so that the engine ran so well? 

As for now, the preheat system is a "go" but with some "as needed" mods to the cooling area of the engine.

An important question is: What is the best and fastest way to bring the engine up to running temperature?  The system I first used, starting with 1/3 choke for the first few minutes and then fully opening it, worked fine.  But this requires letting go of the toggles during one of our most dangerous moments in PPG: climb out.  Later I used duct tape to close up the cooling even more on the engine.  I started it and then fast idled it (screwed in the idle adjustment).  The engine warmed up to around 70C in 4-5 minutes which was sufficient, but the engine got really hot, over 160C.  Removing some of the duct tape after the flight brought the running temperature down a bit when I launched later that day.

Simple is always the best in aviation.

Steps to undertake when operating in cold weather (50F/10C to 70F/21C)

Cold weather operations require a perfectly operating fuel system and ignition.  Install a CHT and perform a thorough fuel system test to eliminate obvious problems.  Ninety percent of the engines we work on have fuel systems that are not fully functional.

Here are things to check/do.  The colder it is, the more pronounced the problems are and the more likely a lean condition will be experienced.  These fixes only address a little more than 1/2 the problems of cold weather.  At the time this page was updated, we were having record cold weather in SE Oklahoma which presented us with many challenges that needed solutions.  This is a work in progress so check these pages often.  The poor hamsters are running as fast as they can....

I am continually testing paramotors and fuel in all sorts of conditions and will post new information on these pages.  If pilots have helpful information, please contact us and it can be posted here.

We cannot expect the same performance in all ambient conditions as a $100,000 general aviation aircraft.  It is the price we pay for simplicity, attractive cost, light weight, and far less maintenance.  Think of it as tent camping versus using a fully equipped RV.

Clothing

There is no other way to figure this out than by doing it because all pilots respond to the cold differently.  I am about average and often fly in near freezing or below.  These are my suggestions.  The launch environment must be perfect, especially in snow where launching can be very difficult.  Count on falling (facedown, engine off) when landing unless you have Orangutan genetics.  However, snow is soft and fluffy.  Do NOT fall sideways if PPG.  Do not fly if you are already cold because you will not warm up in flight no matter how much clothing you are wearing.

vulture