302 Netto enhancement?

302 is an excellent instrument and after a recent problem, excellent local and central support. One (to me) glaring gap in it's functionality however is that of a 'Netto in cruise - t/e in climb' setting.

The Cambridge 'SuperNetto' function, which gives would-be climb rate in cruise, is great for Minden based ASW22's, but for those of us in North Europe, tip-toeing along at max LD under a cloud base of 3500 feet, I want to know what the airmass is doing, not what I could be climbing in, on the off chance there was lift. The current 302 Netto function works great in cruise, but you then get netto in climb...not much use.

Anyone else think this would be useful? Technically it can't be that difficult (even I can write code to detect a switch setting)

RSVP

On 4 Mar 2003 18:24:08 GMT, Chris Davison

If you have a 'relative netto' just put a small piece of white tape at the 1.5 to 2 knots down position on the outside of the vario scale. That then becomes the 'airmass zero' position. This position will vary slightly with altitude and ballast. You can make the tape a little wider and allow for this.

The B50 actually has a cruise/climb switch and can be configured for real netto in cruise. This design decision dates back to 1978 during the design of the B10 when I realised that there was no good way to get netto in cruise and TE vario in climb without a switch.

Mike Borgelt

Borgelt Instruments

Actually, if you're flying at min sink, the vario is telling you exactly what your climb (or sink) rate currently is. If you speed up and the airmass remains unchanged, it should continue to give you the same reading. So as you speed up, the vario automatically subtracts your sink rate at that speed. Pretty much like a netto - only the needle is offset by your minimum sink speed.

I don't understand why you'd need a netto value. If the needle is above 0, then start circling and you'll go up.

With a pure netto, you'll need to know that a value of X knots positive is needed to keep you from sinking. Seems to me that's more work you have to do in your head. Why not just let the 'smart' instrument do this for you.

Best I can tell, the only use for a netto is if you have a speed ring on it, as it will automatically cancel out the aircraft polar and give you a good speed to fly.

Am I missing something here?

-Tom ASH-26E (with 302)

I'm not sure it's useful, since you always maneuver for the least sink, so it doesn't matter if the Netto 'zero' is offset by a constant.

Nonetheless, the 302 does allow you to choose Netto if you wish. The setting shows up in the 'Configure Instrument' page of the 300 series utility (ver 2.5.3). I don't know what version of the 302 you need (I'm using ver 2.5) to use this option.

Tom, re 'Am I missing something here?'...yes, I think so.

There are many sitautions with a lower performance glider (esp lower than an ASH-26E ) where the flight is not fast-cruise / pullup / climb / fast cruise, but slow crawl through very weak lift (not strong enough to climb in or climb sensibly in) to maximise every inch of glide performance.

I don't want to stick white tape on my $2500 vario, I don't want to mentaly adjust for altitude and all up weight and I don't want to have to go into the 302 utilities to switch from t/e to netto and back again! I want my vario to do this for me!

Mike Borgelt's varios and indeed all of the LX range have a simple switch that does this, the climb / cruise switch. The lack of this function on the 302 is a BIG gap in functionality to my mind.

The thing Tom is missing is a lower performance glider flown in weaker conditions! Chris

At 03:24 05 March 2003, Tom Serkowski wrote:

the 302 has provision for a manual switch to change from cruise to climb. Read the wiring instructions its all detailed there.

It will also switch with the GPS/ASI inputs detecting slow/circling flight.

Al

Al, agree, be aware however, that does not change the function from Netto to t/e climb, it just stays as Netto...and Netto in climb is not much use (to me at least). Chris

At 08:00 05 March 2003, Al wrote:

Eh? Maybe it doesn't work with your 302, but with mine, with the switch in climb position, the audio/meter are indicating TE vario, and in the cruise position it's netto...

I think you've been confused here by the utility program. The 'Configure Instrument' dialog box configures what the meter shows in cruise mode only. In climb mode it always shows total energy. There are also statements in the manual (which may or may not be correct) suggesting that the audio is always super netto in cruise, and total energy in climb.

If you aren't using an external cruise/climb switch, it will probably give you exactly what you want...

Now I am confused. I have the 302 on my bench, with an external c/c switch and the setting of netto, when I switch to cruise, the LCD 'circling' icon goes away, the pointer shows 1.5 up (as the vario is on the bench to it assumes I am in rising air to keep it at that height). When I switch to climb, that cricling icon comes back and the needle stays at 1.5 up..it does not go back to zero to show that I am neither climbing nor sinking..

Can someone from Cambridge comment on what it is supposed to do please????

Thanks all - Chris

At 09:24 05 March 2003, Marc Ramsey wrote:

I still don't understand why you need netto. Once you've slowed down, the 'supernetto' behaves just like a normal compensated vario. If the netto says 100 fpm up and the supernetto says 20 fpm down (asuming 120 fpm glider sink rate at this speed) what's the difference. Once the needle indicates above 0 and you're flying straight ahead at near minimun sink, you're going up.

Bottom line is you fly at any speed you wish, if the supernetto says lift, then you slow down and start climbing. No need to circle. If the supernetto says sink, then there's nothing to do but keep poking around until it says lift. Or keep poking around and keep the sink at a minimum. Again, as long as you fly below a certain airspeed, the supernetto is just a plain compensated vario.

And even in high performance gliders one will fly around at max L/D sniffing for lift on a weak day. A pullup from that speed doesn't net much of a gain, since it's close to thermalling speed anyway.

I set up the audio sink tone and also use that to aid me in recognizing stronger areas of 'sink' or air that's buoyant, but not quite enough to climb in. As soon as the tone goes from constant to beeping, I know it may be time to circle.