REFLECTOR: Need a topic... gear down check

Thu Jan 24 21:41:34 CST 2013

I have this landing gear warning system installed in my Velocity XL-RG.  It
senses the ground just like radar or a laser except it uses microwaves
instead.  Seems like it's exactly what you are looking for.

http://www.flyingsafer.com/2037.htm

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Dave T Nelson
Sent: Thursday, January 24, 2013 3:48 PM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: Need a topic... gear down check

I agree with everyone that a key shortcoming of my plan is in having to
guess at the altitude (i.e., subtracting the destination airport altitude
from the Dynon altitude).  Short of a laser based or radar altimeter, a
better solution would be to find a north American elevation database
referenced to lat/long.  A bit of background...

I researched homebrew radar systems, even going so far as to exchange emails
with several experimenters.  Unfortunately, there was no simple, repeatable
design to be had...  The other factor to consider is that the architecture
of what I'm implementing is very highly configurable... there will be no big
problem in retrofitting a better solution in the future.  

Keep the input coming!

Dave

Dave T. Nelson
T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
Program Director, ISC ECAT NPI & Test Engineering

----- Message from James Lotspeich <jlotspeich34 at gmail.com> on Wed, 23 Jan
2013 22:28:08 -0600 ----- 

To:

Velocity Aircraft Owners and Builders list <reflector at tvbf.org>

Subject:

Re: REFLECTOR: Reflector Digest, Vol 94, Issue 37

It's been a while, but I believe Cloudcap builds laser altimeters for
precision autopilot landings (UAV autopilot).  The cost six years ago was
~$1k.  Worked pretty well when wings are level up to maybe 1000ft.  With an
IMU or AHRS unit, you can tell when you're level.  The laser will give a
good height above ground.  Both units feed serial data or CAN bus.  I'd
trust the laser over field elevation calculations.  Also could be used for
an auto gear down if you're feeling really experimental.

James

On Wednesday, January 23, 2013, Richard J. Gentil wrote: 

Hi Dave,

I'm sorry I didn't make myself clear. I was going on the premise of building
your own because the topic had mentioned building a single PCB computer to
do what you needed. My comment was on how Avidyne handled it with the
information from the Garmin and it was something that if you were thinking
of designing on your own could give you some ideas on how to implement it.
And I should add if you did build it, I would be happy to take one off your
hands. ;)

Richard 

Sent from my iPhone 5

On Jan 23, 2013, at 2:43 PM, Dave T Nelson <dtnelson at us.ibm.com> wrote:

I'll respond to Rich Ervin and Rich Gentil below...

From:
----- Message from Rich Ervin <rich_ervin at hotmail.com> on Wed, 23 Jan 2013
13:54:25 -0500 ----- 

To:

<reflector at tvbf.org>

Subject:

Re: REFLECTOR: Need a topic... gear down check

Any way to build this based on altitude or distance to ground? Some simple
range detecting device that can measure the distance to the ground?

What I'm planning is to use the Dynon altitude (referenced to MSL), and
subtract the altitude of the destination airport (using the three letter
identifier and a quick database look up)... to approximate the AGL altitude.
This is far from perfect... I've looked at trying to find an elevation
database I could use and reference via lat/long... but so far no luck.  

From:
----- Message from "Richard J. Gentil" <richard at naples-air-center.com> on
Wed, 23 Jan 2013 14:22:12 -0500 -----  

To:

Velocity Aircraft Owners and Builders list <reflector at tvbf.org>

Subject:

Re: REFLECTOR: Need a topic... gear down check

Rich,

You could use a radar altimeter. Also the Avidyne System in the Cirrus uses
the GPS to give you TAWS terrain warnings when you are more then 5 miles
from an airport and it calls out 500ft when you are on approach before
landing at an airport. 

I would think that something like that would be what you are looking for in
order to integrate with a gear warning if the gear is still up. 

Richard 

I've actually looked at homebrew radar altimeters for this application...
complicated and expensive.  The Avidyne system in a Cirrus is quite
different from my Garmin GNS-530W... my Garmin has terrain warnings, but
unfortunately does not output anything usable regarding terrain warning or
AGL altitude in the RS-232 data string.  As I'm not ready to by an Avidyne
(or a Cirrus), I'm kinda out of luck on that front and working on my own
solution.

To all - thanks for the input!

Dave

Dave T. Nelson
T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
Program Director, ISC ECAT NPI & Test Engineering

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