Down Drafts & Micro Bursts

[lv2plyguitar 172]

Leni, Randy,

 

Is there anyway to forsee a down draft or micro burst before flying into it.  When are weather conditions most likely to produce such conditions?   Your experience with the semi is something I never want to encounter.

[akflyer 1427]

that is the killer on micro bursts Jeff.. One minute your flying along in clear blue skys, not a breath of wind, the world is a perfect place to be, then wham.. your getting slammed down against the shoulder harness and the VSI is pegged out going the wrong direction.. We are not "spose" to have them up here, but I have hit them more than once!  At that point your just praying you can get to the edge of it before you hit the ground.  Think water fall effect.  It will go straight down in the center to the ground, but on the edges it will be shooting back up like the mist clouds on a good water fall.  The ones I hit I could not outclimb them, full power, nose pointed at the sky and still dropping at 2000+ FPM.  drop the nose and just try to find the edge is all I can say..

 

The down drafts can be a bit easier to predict if your flying in the mountains.  If your in a pass and the wind is coming across the mountain tops say left to right, your going to want to stay towards the right side of the pass as you will have a down draft on the left side with the winds coming over the top and dropping over the ridge, across the valley floor and probably an updaft on the far side.

 

There can be quite a bit of thermal activity over the hay fields etc in the plamer / wasilla area.  We use them ALOT to fly the model gliders etc.  Early in the morning, and later in the evening it is normally calm, but during the heat of the day, there can be some serious thermal activity in the area.  Nothing to worry about really, but it can get a bit bumpy with our light planes.

 

[EDMO 1078]

There are some good glider pilot's books available that will help you study the terrain and weather conditions - you just asked about the worst surprise for a pilot - these have caused large jet passenger planes to crash. Hopefully, none of us will fly into or try to outclimb a thunderstorm, but you cant see the wind all of the time.

I watched an NTSB film taken from a helicopter that was flying close to an INVISABLE TORNADOE - You couldn't see any sign of it except the trees and grass below being blown around in a circle.

EDMO

[SuberAvid 617]

Jeff,  First I try to avoid what I can see.  Don't fly under thunder head clouds or even close to them.  The varga rain you can see will have down drafts with it.  Any change in layers will be rough; you will notice this as you get up close to a cloud layer. If you can't avoid the thunderstorm, get on the ground and wait it out.

 

Like Leni says, when flying in the mountains, picture the direction of the wind and what it would be doing if it was water flowing over the ridges or canyons; it's going to cause an updraft on the front side of the ridge or mountain and a downdraft on the backside and also turbulance over and around the mountains and ridges.  If you have wind coming out of the north and you fly on the south side of Sleeping Lady, you are going to get a rude pounding.  Better give yourself some distance from it (like about to the edge of the inlet) so you don't get slammed to the ground.  Flying into canyons, I always try to get close and feel how rough it is getting and be prepared to turn around if it gets too bad.  If you see dust kicking up off the river sand bars you can expect the wind to be blowing about 30+ mph.  This may be flyable, even smooth if you are in the middle of a relatively flat or wide valley floor but be careful when you get toward the edges or transition into an intersecting valley or canyon.  30 mph makes for some nasty turbulence in in the mountains in our planes and anything above that is dangerous as far as my personal limits go.

 

Thermals are interesting and can give you some real lumps in the throat and stomach.  If you fly over the hay flats or the wetlands and lakes of the Kenai area when it heats up on a hot afternoon you will be going up and down at 1000 fpm pretty regularly, but on the same day if you go out to the edge of the Cook Inlet and fly the beach line it will be nice and smooth along the water.  If you fly down the the Soldotna pancake breakfast with us on 8 June you will get to experience this (if the day is a nice hot one).

 

For the invisible microbursts, about all I can say is they are going to be a lot more likely with thunderstorms around building or breaking down.  Like Ed said, if you happen to see dust on the ground, wind in the trees, grass, or water that looks like it is only in one spot, get the heck out of there.  You can't out climb it, just try to keep your wings and attitude as level as possible and try to fly out the side of it like Leni said.

 

Read the book on Mountain Flying by Sparky Imeson (I think that is his name).  Also, the book on flying in Alaska by Potts (can't remember the exact name).  Another great book by a friend of mine who lives on Wolf Lake is "Survival Flying" by C. Jay Baldwin.  These all give good advice on bush type flying from those who have learned things the hard way and provide good advice so hopefully we can avoid some of the negative lessons learned.  I always consider myself to be an amature, and learn from everyone else I can.

[EDMO 1078]

One last thought on all the good things that Randy told you:

If you see Lenticular clouds (normally by mountains) stay well away from them. You can encounter extreme turbulence, like the Evergreen 747 taking off toward the Chugach range and turning north over my house in East Anchorage - the turbulence took an engine off of it, and it dropped at Boniface and Northern Lights between the mall and apartments a block away from me.

EDMO