Cambridge 302 compensation opinions

[Caracole]

Can I get some opinions from some of the 302 users on the pros and cons
of using TE compensation verses electronic compensation?
Such as, which do you prefer and what your experience has been using each.
In short, what do you like and what are you not totally happy with about this
instrument.

M Eiler

[Eric Greenwell]

Caracole wrote:

> Can I get some opinions from some of the 302 users on the pros and cons
> of using TE compensation verses electronic compensation?
> Such as, which do you prefer and what your experience has been using each.
> In short, what do you like and what are you not totally happy with about this
> instrument.

I've used it both ways for several hundred hours each, and didn't notice
any difference in operation while gliding. This is on an ASH 26 E:
Prandtl tube on fin for pneumatic compensation; nose pitot/tail statics
for electronic compensation. I prefer the electronic compensation
because the vario works better when the motor is running.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Mark Zivley]

I found what I was pretty confident was a bug in the electronic
compensation code 1-2 years ago. I don't know if that issue was
corrected in subsequent firmware upgrades, but when I found it I
switched to TE input and have been happy with that.

The bug resulted (on the bench where things were totally stable) in the
vario "sticking" + or - a couple of knots after the system was
disturbed. If I dialed the electronic compensation back from 100 to 0
that error erased itself in a linear fashion. By going to a TE input
and setting the compensation to 0 eliminated that issue for me.

If anyone has a new unit that's on the bench I can certainly provide
details if you want to test it.

Yes, I did make 2-3 attempts to communicate this to CAI and once I was
sure they really knew about it I let it go. I never heard back from
them directly on a resolution.

Caracole wrote:

> Can I get some opinions from some of the 302 users on the pros and cons
> of using TE compensation verses electronic compensation?
> Such as, which do you prefer and what your experience has been using each.
> In short, what do you like and what are you not totally happy with about this
> instrument.
>
> M Eiler

[TomnKeyLargo]

I use the 302 on electrionic TE, my Sage is on a " B " box by Wil S. and a B-40
on the TE probe. The 302 works great and so do the others. The " B " box by
Wil S. is what I do most of my thermaling with, with weak lift I like the B-40.
The 302 is used for cruising and shows me what my climbs will be if I stop. I
use the DDV on the 302 along with the read outs on the 303 during climb so I
know when its time to leave. The 302 with the 303 is really a good setup. I
guess what ever you like is the best answer, fly with what you got and try it
several ways, then "you" decide. # 711.

[Tom Serkowski]

In my ASH-26E, I have the 302 set up for electronic TE and a Winter
varoi is connected to the TE probe. This way the 302 gives me correct
vario info while I search for a thermal in which to shut down the
engine. The few dive and zoom tests I've done show the instruments
agreeing fairly well.

I don't recall the exact numbers, but the audio is set to less than 1
sec and needle is around 2 seconds. A bit twitchy, but pretty much
matches my butt. I'll glance at the Winter in a very wild thermal if
I need a slower indication of trend.

I'd love to see CAI work on integrating the G meter to help filter out
horizontal gusts. Sure would make it easier to center lift in the
shear prone mountains of Colorado.

Also, I'd like to see some more work done on vector winds. With Glide
Navigator II, I can select an extra display of instantaneous headwind
component and a delta from the vector wind. If the delta is more than
a few knots, especially on a long glide, I'll turn 45 degrees, wait 10
seconds, turn back 60-90 degrees, wait another 10 seconds, then resume
the original course. Often, I'll see the vector wind update and the
HW component come down to 0. Other times it won't.

It sure would be nice if airspeed and wind info could be saved in the
IGC file as comment/custom records that could be later analyzed. CAI
could use this info to improve the software and programs like SeeYou
could use this to display wind information.

Tom Serkowski

[HL Falbaum]

I use a 302 on electronic comp, using the pitot and static from the Prandtl
triple probe. My other vario is a B40 using the TE from the triple probe.
The electronic comp setting is 105. It tracks the B40 quite nicely,
including some still air pull up's, dives and slips. I have the audio set on
0.8 sec and the needle on 3.0

Winpilot gives me thermal info for the "go" decision.

All in all satisfactory, and the two varios are as independent as possible.

I an using firmware 2.63 (or whatever is the latest).

I too have written CAI about their plans to use the g-meter to improve gust
filtering. No response at all!

--
Hartley Falbaum
ASW 27B "KF"


"Caracole" > wrote in message
om...
> Can I get some opinions from some of the 302 users on the pros and cons
> of using TE compensation verses electronic compensation?
> Such as, which do you prefer and what your experience has been using each.
> In short, what do you like and what are you not totally happy with about
this
> instrument.
>
> M Eiler

[John Galloway]

I can't see the attraction in electronic TE. There
is no theoretical advantage in taking your pressure
data from two probes instead of one - it just introduces
a possible time error between the sources. Also glider
statics and static probes are much more sensitive to
yaw angles than a well designed TE probe. (Only the
flat Brozel designed STATEK probe is more yaw insensitive).

My (ex) 302 in a Duo was much better on the TE probe
then with electronic TE.

For motor gliders it doesn't matter if there is no
TE with the engine running. Just switch the TE probe
to static and if there is a fin pitot switch it to
a nose pitot.

BTW - if considering a triple probe for a MG get a
double TE/static probe instead. That way the varios
etc can take dynamic pressure off the fin pitot (switchable
to nose with the engine on), the TE can be switched
to static and the double probe static won't be bothered
much whether the engine is running or not. Thanks
to Karel Termaat for that scheme - as used on his Ventus
2CXT.

John Galloway

[Eric Greenwell]

In article >, says...

>BTW - if considering a triple probe for a MG get a
>double TE/static probe instead. That way the varios
>etc can take dynamic pressure off the fin pitot (switchable
>to nose with the engine on), the TE can be switched
>to static and the double probe static won't be bothered
>much whether the engine is running or not. Thanks
>to Karel Termaat for that scheme - as used on his Ventus
>2CXT.

I didn't understand this:

-are there two identical probes, each with a TE venturi and a static?

-a single probe with two TE venturis and one static port?

-regardless, why won't the static on the probe(s) be bothered by the
engine propwash?

-is there a separate pitot tube, or is that incorporated into the
"double TE/static probe"?

--
-------
Eric Greenwell USA

[John Galloway]

Eric,

Karel's scheme on his Ventus 2cxt which I intend to
copy is:

a standard fin pitot with an Ilec extension used for
the ASI and vario which is switchable to nose pitot
when the engine is running (SH include a manual switch
for this but Karel's glider switches the pitots automatically
with little electrical driven pneuatic switches)

a fin double probe for vario TE and static only - with
the engine up the TE is pneumatically switched to fuselage
static.

(The ASI system on SH gliders is specified to use the
fuselage statics and fin/nose pitots)

The problem with using a triple probe for all the vario
inputs is that with the engine running the probe TE
and ASI fin pitot are switched leaving the probe pitot
in the propwash. A third pneumatic switch could be
added but that would add more lengths and complexity
to the pneumatic plumbing and there is no real advantage
in using a triple probe pitot over a standard fin pitot
with an extension.

A very simple and sensible plan and Erwin Salzinger
who makes the probes also recommends it for MGs when
I contacted him. He makes a special order TE/static
probe that is not pictured on his website but consists
of a two pronged TE probe with the static as a central
extension. The probe is mounted with the twin prongs
horizontal so as not to interfere with the pitot probe
underneath. He says that the probe works well horizontally
and has good pitch and yaw insensitivity.

John Galloway


At 03:36 27 June 2004, Eric Greenwell wrote:
>In article , says...
>
>>BTW - if considering a triple probe for a MG get a
>>double TE/static probe instead. That way the varios
>>etc can take dynamic pressure off the fin pitot (switchable
>>to nose with the engine on), the TE can be switched
>>to static and the double probe static won't be bothered
>>much whether the engine is running or not. Thanks
>>to Karel Termaat for that scheme - as used on his Ventus
>>2CXT.
>
>I didn't understand this:
>
>-are there two identical probes, each with a TE venturi
>and a static?
>
>-a single probe with two TE venturis and one static
>port?
>
>-regardless, why won't the static on the probe(s) be
>bothered by the
>engine propwash?
>
>-is there a separate pitot tube, or is that incorporated
>into the
>'double TE/static probe'?
>
>--
>-------
>Eric Greenwell USA
>