Butterfly vario side-by-side with ClearNav vario

The advent of varios with inertial probes that enable the compensation or identification of horizontal gusts will be especially useful in hot strongly thermic areas, like Arizona where I mostly fly.

This is especially true on days when the air is stable but still rises strongly because of very strong surface heating. Thermals in these conditions often have a strong horizontal outflow that increases the energy of the ship as you approach the thermal. Since your total energy increases, all conventional varios indicate lift, leading the pilot to turn too soon. Many experienced pilots know this and compensate as best they can, but it would be great to have a reliable vario do this for you.

Mike

On Friday, May 17, 2013 2:23:21 PM UTC-4, Mike the Strike wrote:
The advent of varios with inertial probes that enable the compensation or identification of horizontal gusts

So does the ClearNav
1)have an inertial probe and
2)does it have the software (at the moment) to filter out horizontal gusts?

So does an "inertial probe" and an "accelerometer" both provide the same sensor inputs to the software?

On Friday, May 17, 2013 2:59:18 PM UTC-6, son_of_flubber wrote:
On Friday, May 17, 2013 2:23:21 PM UTC-4, Mike the Strike wrote:

The advent of varios with inertial probes that enable the compensation or identification of horizontal gusts



So does the ClearNav

1)have an inertial probe and

2)does it have the software (at the moment) to filter out horizontal gusts?



So does an "inertial probe" and an "accelerometer" both provide the same sensor inputs to the software?

I'm not sure how it is actually being implemented but I would interpret "inertial probe" as an IMU (Inertial Measurement Unit). IMU's have 3-axis gyros and 3-axis accelerometers. The gyros keep the accelerometers aligned up-down, east-west and north-south. MEMS IMU's these days are nearly chip-size so one could be inside the vario with GPS position data serving as a calibration signal to compensate for drift. This means vertical acceleration can be measured and the integral (velocity) can be displayed as a vario signal. The advantages of an inertial vario include zero lag, gust insensitivity and complete freedom from TE probes and associated plumbing.

The gust/thermal discrimination is done by comparing the inertial-TE with air-data TE. If the air-data shows a gain in total energy but the inertial data doesn't, it's a gust.

The above is the most elegant implementation but partial implementation could also provide an advance over the old air-data only varios.

In theory, both the butterfly and the CN have enough innards to really advance variometry, because they have the potential to measure the vertical speed of air around the glider.

If you fly in to a thermal, the g meter increases. If you pull back on the stick the g meter increases. But the gyros can tell that the glider nosed up in the latter case. So, the vario can measure "netto g" if you will, the acceleration of the glider caused by changes in the surrounding air.

This is much faster than a vario. For a vario to work, you have to fly into the rising air, g increases, F = MA does its work, the glider starts rising vertically, then the vario can start to measure it. The system based on g and heading does it instantly, at least giving a second or two earlier lift detection.

Looking at sideways g, correcting for yaw, also can tell the vario if there is a sideways gust. Looking at fore and aft g can tell the vario if the glider has entered a wind shear on the nose rather than vertical thermal.

Eventually, by comparing the GPS track through space with the relative wind, these various could also measure outside air motion directly.

I don't know how much of this is currently programmed in to either one, but the potential seems intriguing.

John Cochrane

On Friday, May 17, 2013 6:20:24 PM UTC-7, wrote:
If you fly in to a thermal, the g meter increases. If you pull back on the stick the g meter increases. But the gyros can tell that the glider nosed up in the latter case. So, the vario can measure "netto g" if you will, the acceleration of the glider caused by changes in the surrounding air.


What happens when the flaps go positive?

Marc

What happens when the flaps go positive?

Marc

You get a single transient, which you know about because you just moved the flap handle

Yes, but the vario doesn't "know" that unless you have multiple switches on
the flap detents. Also, how does the vario "know", from increasing "g" that
a pitch up was caused by elevator travel or by the change in angle of attack
due to the vertical component of the thermal? Do we also need stick
movement measuring equipment?

This is all pretty intriguing to me as an engineer because of the
capabilities and the applications we can think up but (just speaking for
myself), I'm less impressed by a 1,000 km flight by a long winged, engine
equipped, highly instrumented glider than I am by a 300 km flight by a rag
and tube machine equipped with a pellet variometer. Still, I like my
LAK-17a!


wrote in message
...

What happens when the flaps go positive?

Marc

You get a single transient, which you know about because you just moved
the flap handle