Flying Early in the Day Part 1

Part I: Getting an Early Start

I got a lot of positive feedback on the articles about flying in special circumstances (under an overcast and flying in the blue), so I thought some XC pilot readers might appreciate a few ideas on other XC circumstances that don’t get a lot of articles or written discussion. So what follows is a two-part article with the first part on soaring early in the day and the second part on flying late in the day.

If all you are interested in is competition, where we usually fly a 3-hour speed scored event in the meat of the day, you probably don’t need to learn how to plan a flight with a launch very early in the day. But if you are interested in setting distance records, doing very long OLC flights, or getting the maximum milage out of a day predicted to end early, then it will help to learn to take the earliest starts possible. So let’s talk about starting tasks very early in the day.

What kind of morning is it?

The first step in an early start is figuring out what kind of soaring morning it is going to be. For our purposes, we can generalize into two types of conditions in the morning of a predicted good day - and our strategy is different depending on which type of day it will be.

Deep Morning Inversion

The first type of day is one with a deep early morning inversion layer above the ground (determinable by the presence of an obvious low-level haze or dust layer, or by a tow pilot report that the morning air is “dead” or by a knee shaped reverse angle in the skew-T chart temperature line just above ground altitude). [Most of the modern online soaring prediction products have localized Skew-T charts available and if you need help learning to read one and determining the trigger temperature try this source: http://flsc.org/portals/12/PDF/Read_Skew_T.pdf ] These mornings require the surface temperature to heat the air to a trigger temperature where the surface air as builds up a buoyancy pressure that finally gets strong enough to overcome the inversion. Such days start a little later and have characteristic thermals that begin strong and go fairly high once they start. Not much useful happens before they start. Our strategy on these days is to be airborne and ready to climb when the trigger temperature is met so that we catch the first thermals. Monitoring the surface temperature before launch (and launching when - or just before - that temperature is reached ) is helpful here, as is watching for haze domes, variable surface breezes, and initial cumulus formation. We want to be in the air when those things start happening. These are the mornings that you might consider adding a little ballast if you would normally fly with it - because the initial thermals are pretty good. More on ballast later.

Little to No Surface Inversion

The second type of morning we can encounter is one where there is little to no surface inversion so that the sun warming the surface causes buoyant thermals to rise early with no inversion to retard them. These days start clear without haze or dust and have characteristic thermals that start early, cycle fast, and progressively grow in height, duration and strength as the morning progresses. Each thermal will be better than the last one. These days also have the advantage of substantial “thermal density” - meaning that although the thermals are low there will be more thermals in a given flying area and so we don’t need to glide very far to reach the next thermal. Our strategy on these days is to launch as soon as we think we can sustain soaring flight (our clues are trigger temperature, light/variable breezes on the ground, low level soaring birds, haze domes, and initial cumulus formation), and we fly “low and local” until the thermals bring us to an altitude where we are comfortable starting the task - weighing our personal margins, the land out options, the increased thermal density, cumulus clouds on course and the task layout technique discussed below. Because we all weigh those factors differently, determining exactly when to decide to start the task will be different for each of us. But we have put ourselves in a position to start as early as we are comfortable doing it.

Banner photo was taken by Sophie Mahieu

 Roy Bourgeois is a well-known US and South African glider pilot who serves as the Chief Pilot for the Greater Boston Soaring Club. He has held several US national records, competed in many US and Canadian Nationals, and has flown over a quarter million XC kilometers in his 4200 hours of gliding. He can be reached at royb@bw.legal