On Thursday, July 23, 2020 at 10:03:12 AM UTC+12, Eric Greenwell wrote:
6PK wrote on 7/22/2020 10:54 AM:
I share this opinion. BTW the main rules are; keep the speed up (so you won't run out of ailron) and stay coordinated.
"Keep the speed up" isn't a rule, it's just encouragement. How can a pilot
determine the flying speed is fast enough? I don't fly faster just because I'm
circling near the slope of a ridge, or mountain face; generally, I think I fly
fast enough to handle the turbulence easily. Coupled with that is moving farther
from the rocks the bumpier the air is. So far, that's worked, but I have no idea
how to put that fuzzy advice into something another pilot can use.
The 'rule' I use and teach is the take your target thermalling speed and add five knots for terrain and five knots for turbulence, plus half the wind speed. So a bumpy thermal in ten knots of wind would have me starting turning fifteen knots faster than normal. As you get the feel for the thermal you might pull those margins in.
Running onto a ridge I arrive with all my safety margins and only ease them back if I'm really confident that things are better than I thought. Like most pilots who fly along ridges on unstable days I have been rolled towards the hill a few times. Nothing outrageous, but it gets the heart rate up when your are holding the stick hard on the stop and still not rolling away. I do notice many pilots aren't really using full control movement. I tell them the reason we have control stops is to give you somewhere to rest your hand while you wait for a response.
Using the rudder is important, but you do not want to get uncoordinated. Full aileron is likely to want a matching amount of rudder though. This varies from glider to glider and with speed, so you need to know your aircraft.
And, I'm sure the speed and distance depends a lot on the type of glider, in
addition to pilot skill, but I can't even tell someone how far I am from the rocks
- no way to measure, so it's just guessing if I mention a number, and the other
pilot is just guessing, too, when he tries to stay that far away.
Judging clearance is a skill that can take a while to learn. Some mountains lack features that indicate scale. Mountains with trees, roads, vehicles etc offer scale that people are used to. Bare rocks don't.
Best to be close enough to be in the lift, but not closer. I only rock polish on weak predictable days where you ned to be close to get lift. Gentle ridge lift or weak anabatic flows. If it's unstable you need a lot more room to allow for those thermals that might roll you into the hill. In thermic conditions I'd allow almost a full turn of space, maybe 150 - 300 meters. That's horizontal clearance. For vertical clearance you need to consider the slope and escape routes. Being close to steep slopes is generally safer than shallow slopes because your escape routes get more clearance sooner.
Maybe I'm just lucky, because I've never experienced the loss of roll control for
more than, say, 20 degrees. Or maybe I scare easily enough, that I've always given
myself enough airspeed and distance. How do I tell the difference between luck and
good piloting?
It's good piloting if you don't crash and bad luck if you do?
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
--
Phil Plane
Omarama