alternative McCready theory and variometers

Hi,

The "alternative McCready theory" has been around for decades now. http://www.tbss.us/txfiles/Kai_intro_XC.pdf
It's not opposing McCready, just making a strong case for steadier inter-thermal speeds. But as I'm reading it, it makes the speed command feature superficial.

Is there a variometer manufacturer that doesn't ignore that?

My ideas for features:

* showing equivalentMC http://www.lk8000.it/new-20-features...t-mcready.html
* automatic MC set from equivalent MC

Getting rid of speed command would mean you could have something useful in cruise mode instead. For audio I would probably choose:

* relative netto variometer indication with dead-band.

and more....

Any comments?

Tibor

Correct.



08:43 26 October 2014, wrote:
Hi,

The "alternative McCready theory" has been around for decades now.
http://www.tbss.us/txfiles/Kai_intro_XC.pdf
It's not opposing McCready, just making a strong case for steadier
inter-thermal speeds. But as I'm reading it, it makes the speed command
feature superficial.

Is there a variometer manufacturer that doesn't ignore that?

My ideas for features:

* showing equivalentMC
http://www.lk8000.it/new-20-features...t-mcready.html
* automatic MC set from equivalent MC

Getting rid of speed command would mean you could have something useful
in
cruise mode instead. For audio I would probably choose:

* relative netto variometer indication with dead-band.

and more....

Any comments?

Tibor

Frankly, people who think that "MacCready theory" is wrong and need an "alternative theory" don't understand MacCready theory.

That doesn't mean pushing and pulling and following the vario around. Vario lags make that strategy unproductive. MacCready theory with lags in the vario would say so. However, if you see a beautiful long cloud up ahead with all the signs of strong lift in it that will last several minutes, by all means slow up! If you're stuck in a long lasting river of sink, speed up!

The speed to fly mode remains, in my view, the most useful way to set up a vario for cruising flight. Set it on speed to fly mode with a narrow deadband and a pretty short time constant. So, if you're in zero air flying 80 knots at MacCready 2, it will be silent. If you're flying 60 it will give you a gentle boop boop to remind you that you're cruising too slowly, which your netto would not do. If you had set it on regular TE vario it would be screaming down. What's the point in that?

Then, the speed to fly vairo naturally tells you what the air around you is doing. If it starts rising, you're in better air. That's interesting information. You don't immediately pull back on the stick, as you're flying a basically constant speed. But if the trend is good, the air is smooth, and you see some clouds, then you do gently slow down. And vice versa.

The confusion is in the name. It says "speed to fly" mode, which gives off the air of listening to it and doing huge pulls and pushes. Maybe we should rename it "listen to the air in cruise mode" which is how it works.

This setup works best if the vario units remain in vertical knots, i.e. that the sensitivity of the vario is the same in cruise and climb mode. If you hit 2 knots of lift a previously silent vario should always make the same "2 knots" sound. Of my varios, the 302 and clearnav do that. The LX, while otherwise a very nice vario, is much more sensitive to ups and downs in cruise mode than in climb mode, rendering it pretty useless for this sort of flying.

John Cochrane

On Sunday, October 26, 2014 1:54:55 PM UTC+1, John Cochrane wrote:


The confusion is in the name. It says "speed to fly" mode, which gives off the air of listening to it and doing huge pulls and pushes. Maybe we should rename it "listen to the air in cruise mode" which is how it works.

This setup works best if the vario units remain in vertical knots, i.e. that the sensitivity of the vario is the same in cruise and climb mode. If you hit 2 knots of lift a previously silent vario should always make the same "2 knots" sound. Of my varios, the 302 and clearnav do that. The LX, while otherwise a very nice vario, is much more sensitive to ups and downs in cruise mode than in climb mode, rendering it pretty useless for this sort of flying.


Exactly! I would love to be able to listen to the air in cruise but the LX and ILEC sounds make little sense to me, I agree they are useless.

And If I understand you correctly the 302 and ClearNav then have what I called "relative netto" audio. (relative netto indicates the vertical speed the glider would achieve IF it flies at thermalling speed)
But how much is it skewed with MC settings?

On a given thay after a couple of thermals I have THE SOUND I want to hear in the next thermal in my mind. If in cruise I hear something ressembling that , or better, I'd pull up into the thermal - perfect.

On Mon, 27 Oct 2014 00:55:20 -0700, Tibor Arpas wrote:

And If I understand you correctly the 302 and ClearNav then have what I
called "relative netto" audio. (relative netto indicates the vertical
speed the glider would achieve IF it flies at thermalling speed)
But how much is it skewed with MC settings?

Not quite. 'Netto' mode tells you what the air mass is doing by
subtracting the glider's polar from the vario indication. When My SDI C4
vario is in cruise mode it bases its STF indication (both display and
sounds) on what it thinks the air mass is doing. I imagine that the 302
and Clearnav do much the same.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Monday, October 27, 2014 9:24:05 AM UTC-4, Martin Gregorie wrote:
On Mon, 27 Oct 2014 00:55:20 -0700, Tibor Arpas wrote:

And If I understand you correctly the 302 and ClearNav then have what I
called "relative netto" audio. (relative netto indicates the vertical
speed the glider would achieve IF it flies at thermalling speed)
But how much is it skewed with MC settings?

Not quite. 'Netto' mode tells you what the air mass is doing by
subtracting the glider's polar from the vario indication. When My SDI C4
vario is in cruise mode it bases its STF indication (both display and
sounds) on what it thinks the air mass is doing. I imagine that the 302
and Clearnav do much the same.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

302 audio and pointer give "relative netto" (I dislike this term, it should be "relative vario", but I've lost that battle) which is "the climb rate that you would achieve if you slowed to thermaling speed and adopted a 45 degree bank". Roughly speaking, it is netto - 2 knots, but the calculated value depends on polar, density altitude, wing loading & bugs. ClearNav CNv offers three cruise modes for audio, two for the pointer. Audio choices are relative netto, netto or STF. Pointer choices are relative netto or netto.

STF audio provides useful information, but I tire of the "chatter". I find I prefer relative netto modes, with sink tones off. It does mean that I need to scan the panel a little more often in cruise.

Evan Ludeman (on behalf of CNi)

On Monday, October 27, 2014 10:03:35 AM UTC-4, Evan Ludeman wrote:
On Monday, October 27, 2014 9:24:05 AM UTC-4, Martin Gregorie wrote:
On Mon, 27 Oct 2014 00:55:20 -0700, Tibor Arpas wrote:

And If I understand you correctly the 302 and ClearNav then have what I
called "relative netto" audio. (relative netto indicates the vertical
speed the glider would achieve IF it flies at thermalling speed)
But how much is it skewed with MC settings?

Not quite. 'Netto' mode tells you what the air mass is doing by
subtracting the glider's polar from the vario indication. When My SDI C4
vario is in cruise mode it bases its STF indication (both display and
sounds) on what it thinks the air mass is doing. I imagine that the 302
and Clearnav do much the same.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

302 audio and pointer give "relative netto" (I dislike this term, it should be "relative vario", but I've lost that battle) which is "the climb rate that you would achieve if you slowed to thermaling speed and adopted a 45 degree bank". Roughly speaking, it is netto - 2 knots, but the calculated value depends on polar, density altitude, wing loading & bugs. ClearNav CNv offers three cruise modes for audio, two for the pointer. Audio choices are relative netto, netto or STF. Pointer choices are relative netto or netto.

STF audio provides useful information, but I tire of the "chatter". I find I prefer relative netto modes, with sink tones off. It does mean that I need to scan the panel a little more often in cruise.

Evan Ludeman (on behalf of CNi)

I mis-wrote about the C-302. One can select TE or Netto modes for cruise in the PC/PDA configuration program, but I suggest that you probably won't like the results. I found these modes buggy and prone to indicating thermals that didn't exist. In relative netto mode, the 302 is a decent vario, and I still use one for backup.

-Evan

On Monday, October 27, 2014 3:55:21 AM UTC-4, Tibor Arpas wrote:
On Sunday, October 26, 2014 1:54:55 PM UTC+1, John Cochrane wrote:


The confusion is in the name. It says "speed to fly" mode, which gives off the air of listening to it and doing huge pulls and pushes. Maybe we should rename it "listen to the air in cruise mode" which is how it works.

This setup works best if the vario units remain in vertical knots, i.e. that the sensitivity of the vario is the same in cruise and climb mode. If you hit 2 knots of lift a previously silent vario should always make the same "2 knots" sound. Of my varios, the 302 and clearnav do that. The LX, while otherwise a very nice vario, is much more sensitive to ups and downs in cruise mode than in climb mode, rendering it pretty useless for this sort of flying.


Exactly! I would love to be able to listen to the air in cruise but the LX and ILEC sounds make little sense to me, I agree they are useless.

And If I understand you correctly the 302 and ClearNav then have what I called "relative netto" audio. (relative netto indicates the vertical speed the glider would achieve IF it flies at thermalling speed)
But how much is it skewed with MC settings?

On a given thay after a couple of thermals I have THE SOUND I want to hear in the next thermal in my mind. If in cruise I hear something ressembling that , or better, I'd pull up into the thermal - perfect.

I've had the chance to play around extensively with my ClearNav Vario using audio Speed To Fly vs. Relative Netto. For the reasons stated by others (i.e. moving away from chasing the STF and averaging over a longer period), I've found Relative Netto to be much, much more useful. If I'm flying along at 80 kts and I fly through a real solid core, I want to know that I'd be able to climb at 4kts if I stopped now. That's useful data. I already have a numerical speed to fly indication (e.g. "Fly 80kts") which I glance at to make sure the speed I'm using is "roughly right". That's in many ways similar to the wide STF dead-band that others are using.

I don't remember which of the top US national pilots said this, but his comment was something like: I have two speeds for a given day: Fast and Slow. Those absolute numbers change on any given day (ie. on a booming day, fast might be 90 knots and on a weakish day it might be 70kts), but I don't really worry about a lot of increments in between. Makes sense to me.

P3

On Monday, October 27, 2014 9:35:56 AM UTC-7, Papa3 wrote:
On Monday, October 27, 2014 3:55:21 AM UTC-4, Tibor Arpas wrote:
On Sunday, October 26, 2014 1:54:55 PM UTC+1, John Cochrane wrote:


The confusion is in the name. It says "speed to fly" mode, which gives off the air of listening to it and doing huge pulls and pushes. Maybe we should rename it "listen to the air in cruise mode" which is how it works.

This setup works best if the vario units remain in vertical knots, i.e. that the sensitivity of the vario is the same in cruise and climb mode. If you hit 2 knots of lift a previously silent vario should always make the same "2 knots" sound. Of my varios, the 302 and clearnav do that. The LX, while otherwise a very nice vario, is much more sensitive to ups and downs in cruise mode than in climb mode, rendering it pretty useless for this sort of flying.


Exactly! I would love to be able to listen to the air in cruise but the LX and ILEC sounds make little sense to me, I agree they are useless.

And If I understand you correctly the 302 and ClearNav then have what I called "relative netto" audio. (relative netto indicates the vertical speed the glider would achieve IF it flies at thermalling speed)
But how much is it skewed with MC settings?

On a given thay after a couple of thermals I have THE SOUND I want to hear in the next thermal in my mind. If in cruise I hear something ressembling that , or better, I'd pull up into the thermal - perfect.

I've had the chance to play around extensively with my ClearNav Vario using audio Speed To Fly vs. Relative Netto. For the reasons stated by others (i.e. moving away from chasing the STF and averaging over a longer period), I've found Relative Netto to be much, much more useful. If I'm flying along at 80 kts and I fly through a real solid core, I want to know that I'd be able to climb at 4kts if I stopped now. That's useful data. I already have a numerical speed to fly indication (e.g. "Fly 80kts") which I glance at to make sure the speed I'm using is "roughly right". That's in many ways similar to the wide STF dead-band that others are using.

I don't remember which of the top US national pilots said this, but his comment was something like: I have two speeds for a given day: Fast and Slow. Those absolute numbers change on any given day (ie. on a booming day, fast might be 90 knots and on a weakish day it might be 70kts), but I don't really worry about a lot of increments in between. Makes sense to me.

P3

If you go and do the math you find that achieved cross-country speed varies very little with cruise speed for minor deviations up to, say, 15 mph. Generally there are other considerations that tend to dominate, like depth of the effective lift band versus average distance between good climbs - where a small ratio may make it preferable to fly below the theoretical McCready STF. Almost nothing is worse than bombing along at high speed right into the dirt and digging out for 10 or 20 minutes.

The higher I am, the more likely I am to get closer to the theoretical McCready STF (unless there is convergence or cloud streets where staying closer to the "suck" matters). Certainly the transient drag losses from abusing the stick will exceed the benefit of hitting the optimal STF for anything but pretty long runs in air with significant vertical motion.

Seems like the best audio configuration for cruise would be relative netto that had a dead band up to maybe 2/3 of the McCready setting so you get a little advanced warning and a sink warning dead band that is adjustable both in terms of magnitude and duration of the sink encountered: 10-knots for 10 seconds, 5 knots for 20 seconds, 2 knots for 30 seconds, etc. Modern various are computers, you should be able to dial up whatever you want.

My LX 9000 is pretty configurable, but I still haven't figured out how to come even close to what I want - even something as simple as a consistent audio tone between climb and cruise modes so I don't jump every time it switches from one mode to the other.

9B

I have settled on flying constant MC speed with a failry large "speed to fly" dead band. I only react gently (this is key) in the moderate to extreme ups and downs. This seems to be working for me in a wide range of flying conditions.

I spent a lot of time flying with other pilots (knowing their flying styles) and adjusting my technique slightly in reference to their fairly constant flying style. That was very valuable and often eye opening.

Sean
7T