Trig TT21 Transponder ... reports?

On 8/20/2010 2:11 PM, Darryl Ramm wrote:
On Aug 20, 8:33 am, Alex wrote:
On Fri, 20 Aug 2010 07:14:01 -0700, Andy wrote:
draws 0.8 amps @ 12v

I've not been near an airfield for 10 years now, but are there no
advances in solar power/battery technology since then that improve a
glider's power supply? What is a typical glider's current requirement?

--
Alex

On Aug 20, 8:33 am, Alex wrote:
On Fri, 20 Aug 2010 07:14:01 -0700, Andy wrote:
draws 0.8 amps @ 12v

I've not been near an airfield for 10 years now, but are there no
advances in solar power/battery technology since then that improve a
glider's power supply? What is a typical glider's current requirement?

--
Alex

With gliders we fly you cannot easily stick solar panels over large
areas of the glider because of cost and critical aerodynamic concerns
and concerns about solar heating the underlying composite structure.
There are specialized solar project exceptions. The manufacturer who
dominates solar panels for gliders today is Strobl (http://www.strobl-
solar.de ) and their panels are available preinsalled from all leading
glider manufacturers or as add-on for a large number of gliders. See
my blog at http://www.darryl-ramm.com/2007/01/s...or-sailplanes/
for what a retrofit kit looks like.

They typically deliver 15-30 watt maximum for several thousand dollars
outlay. The Stobl systems use crystalline wafers in a semi-flexible
ETFE (hey that what is used on Trefzel wire, oops another thread...)
type plastic encapsulation. Likely all hand-built. The panels are
attached with 3M ultra-high-bond double sided tape. Some installations
will have molded in recesses for the panels some use hand applied
filleting, some wedge trim strips around the panels. The crystalline
cells give relatively high efficiency even with only partial fill
factor on the panels. Other options emerging might be to use amorphous
thin film panels but you are typical starting with low efficiency. I
have the larges set of Strobl panels I can get on my ASH-26E engine
bay doors that gives a peak spec of 30W (2.5A @ 12V). The actual
delivered power is *much* lower. And you should rely not plan on solar
panels to significantly boost battery capacity for a single flight as
output drops dramatically under cloud streets, overcast sky etc. I
really like the Strobl panels but it may be more useful/safer to think
of them for use for ground charging of a tied down glider (e.g. some
airports have issues with separate panels near the aircraft when tied
down) and as a way of stretching capacity over several days when usual
ground charging infrastructure is not available.

Although it obviously varies widely a typical power consumption number
for a glider avionics is roughly around 0.8 amp (as Evan noted his is)
for what I am guessing is a typical setup of C302 style computer, a
PDA, and VHF radio. Owners should measure and calculate the loads in
the glider and estimate the battery capacity needed or run time
available from the batteries they have. Do not just divide the nominal
"Ah capacity" by amp load, especially at higher loads, you need to use
the discharge curves data from a manufacturer to estimate the
available run time of a battery at a particular load (most good VRLA
batteries are close enough to use another manufacturers spec sheet for
a similar sized battery).

Transponders (and their encoders) used to be considered a large power
hog. And in the days of horse drawn buggies, steam locomotives and
traveling wave tube amplifiers etc. they were. While they are much
more efficient nowadays, you do need to make sure they fit within a
ships power budget. Modern transponders range in power consumption
from ~0.5A for a Becker 4401 175W and ACK A30 encoder to around ~0.3A
for a Trig TT21 (with built in encoder). Transponder power consumption
will vary depending on interrogation rates and temperature (for the
encoder heater). i.e. The Trig TT21 uses less power than large PDAs
like the iPAQ 4700. The numbers here are realistic for typical glider
operations.

The NavWorx ADS600-B specs implies it consumes 0.8A at 12V. I have no
idea if this is accurate or not, it may be less in practice. Today you
need a separate display with third party software to get traffic
information/warnings from the device, so guess around 0.45A (e.g. for
a iPAQ 4700 PDA dedicated to the UAT data display).

Most gliders have some combination of one or more "7Ah" or "12Ah" VRLA
batteries. So to give a rough idea of maximum run time from typical
single batteries ... (These number are very rough, I don't have my
discharge spreadsheet handy that will do this properly, but they give
the flavor.)

2.0A load = guess of typical glider load + NavWorx ADS-600B + iPAQ
4700 for UAT traffic display
@2.0Ah load a typical "7Ah" VRLA battery ~ 2.7 hours
@2.0Ah load a typical "12Ah" VRLA battery ~ 5.2 hours

---

Since one scenario is people with Mode C might go UAT vs. buy a new
Mode S/1090ES capable transponder. A UAT is does not make a glider
visible on TCAS, so if you fly near airliners or fast jets that
transponder is a good idea. If you do not then just look at the
numbers above)

2.5A load = guess of typical glider load + Becker Mode C + ACK30 +
NavWorx ADS600-B + iPAQ 4700 for UAT traffic display
@2.5Ah load a typical "7Ah" VRLA battery ~ 2.2 hours
@2.5Ah load a typical "12Ah" VRLA battery ~ 4.1 hours

---

All these are numbers are for effectively fully discharging the
battery, you should really not plan on running down batteries this
much on typical flights and having no safety margin. Some fudge (20%)
should be deducted from these numbers for typical battery aging. For
very cold flights (e.g. wave) then maybe halve these run times. And
again do the real calculations for your actual setup.

How much battery capacity do you need? My longest flight was 8-9 hours
(in my old glider with no solar panel). A typical "serious" XC flight
for me is around 5-6 hours.

This all assumes the the NavWorx ADS600-B nominal 0.7A spec at 14VDC
nominal (i.e. 0.8A at 12VDC) is correct. It could be lower in
practice. I'm not even sure why we are down this rat hole. None of
this is not a slight on NavWorx, their UAT transceiver was not
designed for the glider market, NavWorx does not claim it is intended
for the glider market, or target any marketing to the glider market
AFAIK. And issues with incompatibility with all existing (Flarm serial
display protocol based) glider traffic display/software, lack of any
third party traffic display/warning product tuned for glider specific
type environments (esp. gaggles), lack of traffic collision/alert
warning from the receiver box etc. are also issues for use in the
glider market. I am convinced that a company who wanted to target the
USA glider marker with a UAT product would have no deep technical
issues addressing these items, or reducing the power consumption
significantly today. The issue is justifying a business case for a
company to do that for the intersection of the relatively small USA
UAT market and the much smaller USA glider market.

BTW some older slides and spreadsheets on glider batteries at
http://www.darryl-ramm.com/glider-batteries/ but I don't think these
make much sense unless you've seen me present them. I originally made
that presentation because of confusion around batteries and
transponders. That confusion went both ways, people way under capacity
for their loads (BTW interestingly often with PDAs and ClearNav type
devices not just transponders) and people thinking they could never
use a transponder, often based on out of date info on transponder
power requirements.

Darryl

Has anyone thought about using a very small ram air turbine to provide
power in a glider? How big would such a turbine have to be to generate
10 watts? How much would this reduce L/D?

--
Mike Schumann