Hi All,
I was imagining I might be able to stay silent, but I can't help myself...
Please, no offence to Mike or any others, it is just that we all see things
slightly differently, thank heavens.
I don't think I ever watch the vario needle while flying. I would very
happily fly at any level with a good audio and a large, easily read digital
averager set high on the panel, and pretty much nothing else. Soon I plan to
fly some comp days with everything else covered up, just to see whether I
really do ignore it, but I have had a number of people flying in the back
seat while I am in front comment on the fact that I almost never look at the
panel.
I prefer my audio to have a single tone, and find no need for any indication
of whether I am in rising air that is above or below my Macready setting. I
simply want to know if I am going up, or if I am not. I also do not use
relative netto during the cruise, but this is a very personal choice. This
audio MUST be as close to perfectly compensated as is possible with the
system that you are using. I have to say that very few gliders I have
borrowed/stolen have a vario that really works. And I have to agree totally
with Mike - if the vario signal is coming from one source, then make it a
good one, and if it is coming from two sources, pitot and static, then give
it a good chance of working and keep the lines from both as close to the
same length as you can. This doesn't have to cost heaps of money. Work on
the KISS principle...
The decision to stop and climb in any particular bit of rising air comes
from other sources, primarily the structure of the thermal that is felt as
you fly into it, much more than any peak vario indication. Usually you find
that a well-structured thermal will produce a better bottom-to-top average
than one which shows strong gusts and high peak readings as you approach it.
As you are arriving at the edge of a thermal is not a good time to be
watching the panel, for a lot of reasons.
I have taken too much space already... back into my box.
BT
----- Original Message -----
From: "Mike Borgelt" <[EMAIL PROTECTED]>
To: "Discussion of issues relating to Soaring in Australia."
<[email protected]>
Sent: Thursday, November 16, 2006 1:17 PM
Subject: Re: [Aus-soaring] varios(was FLARM maths)
At 06:46 PM 14/11/2006, David Griffiths wrote:
I am impressed
I did not even know that this type of gear was available.
Is this all prototype stuff or is it in production?
You might like to look at the B500 on our site at
www.borgeltinstruments.com
Australian designed and manufactured, sold worldwide.
Before getting too excited about varios without visual indicators people
might like to consider how they decide whether to turn in a particular
thermal that is encountered. The vario pointer isn't the only thing but I
bet it is an important part of your decision. Relative netto was designed
to help with this - see our website for details if you don't know what
relative netto does(it is in articles).
Changing the audio at the MacCready setting as we do in the B500 and B50
lets you know to look at the vario but for reasons explained by John
Cochrane in his paper and nearly 40 years ago by Anthony Edwards, you fly
at Macready settings that are quite low compared to the actual rates of
climb you get so you might not make the decision to turn just based on
that audio change.
Likewise when picking a best path through the air, particularly when
streeting, including the vario pointer in your scan is important. To be
really useful here the vario pointer should be high resolution too. We
rejected LCDs on the grounds that the pointer resolution was too coarse.
When working very weak lift the speed of response and resolution of the
vario itself becomes important. When working 5 knots at altitude a poor
vario will do. When at 600 feet over a paddock trying to avoid an
outlanding by working +/-0.5 knots you need all the help you can get.
With some vario technologies there are unavoidable speed of
response/resolution tradeoffs.
Lastly, Total energy is total energy whether it is done by a probe
providing suction below static pressure or whether you measure pitot and
static pressures and add them electronically to provide the same thing.
They both suffer from horizontal gust effects (see article on website) to
the same extent but the pitot/static scheme has some additional problems -
the pitot and static ports are more sensitive to yaw and sideslip than the
modern two hole TE probe is and you need to organise the pitot and static
signals to arrive at the same time at the instrument to avoid undesirable
transient effects.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
Int'l + 61 429 355784
email: [EMAIL PROTECTED]
website: www.borgeltinstruments.com
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