Radar altimeter, which is the right one?

[olymbec]

I ma back with another question. I am thunking of adding a radar altimeter to my new 407GX. For now I am looking at the FreeFlight Systems Radar Altimeter Ih terms of model there is the RA-4000 or the RA-4500 I am not sure if either is compatible with the Garmin G1000.
Besides FreeFlight would someone else recommend a different radar altimiter?
not sure which other manufacture would even be a good choice.

[SASless]

A quick call to Garmin Tech Support would get you an answer on compatibility issues.

Then a chat with your Avionics Tech that will do the install would be my next base to hit.

Then perhaps shop for price at various suppliers for whichever unit you finally decide to buy.

[olymbec]

So after doing my research I decided not to install a radar altimeter

[Aesir]

Why? What would the cost have been?

I have been flying a GX here that does not have Radalt and it really sucks, specially since we fly in whiteout conditions and over glaciers.

[olymbec]

The cost would have been supply and installed approx $12,000.00
I also spoke to two different Bell test pilots and after hearing their comments I decided against it.
here was what I questioned in an e-mail; I was doing some research and I wanted to know your opinion on Radar Altimeters. Would you ever see a need for me to install this option in the new 407GX?
I do plan on flying in the winter quite often and landing on snow covered lakes or other large snow covered areas.
You know I am all about safety and with my experience level far from being a professional I simply would rather be safe than sorry.

Here is the answer I received from one;
Rad. Alts. reflect off "terra firma" ground or water surface. They actually are in error in general over snow and do not address trees or obstacles.
This is what actually caused the Polar First Crew to crash in 2003 when they followed a Rad. Alt in error in Antarctica over loose snow.
That being said: It is a safety enhancing device if used properly. One can't knock safety items! It is designed to keep you from inadvertently descending into the ground or water by unintentionally losing altitude and provide a true reference to your actual height above ground (not altitude). As you know pressure altimeter has massive errors with temperature change. (- in cold, + in heat)
If you would rather be safe than sorry that is all good but you will also have to know how to use this equipment to your advantage.


So after reading this I am not sure if RadAlt will be good for your white out conditions over glaciers.

[SASless]

Whiteout conditions over glaciers....can having a RadAlt hurt?

RadAlts are like hammers in a tool bag.....different tasks require different hammers....but unless you want to use a pair of Electricians Side Cutters for a hammer....you best have at least one hammer in your tool bag.

Anything that assists you in determining your height above ground/water/snow is a plus.....and in this case I would much rather have the RadAlt than not.

As the Man said....understand how to use it to the best effect, understand what it doesn't do, be aware of situations where it is not completely reliable and you would be far safer than not having it at all.

Perhaps a review of your proposed flight operations with a view towards determining easily defined weather/Vis/lighting standards to ensure you always maintain safe and effective spatial orientation by purely visual means might be a very good step towards keeping you safe.

The problem with Whiteout is it can happen very quickly and while you are at very low height above the terrain, or in a valley with higher terrain on three sides....and create a very dangerous IIMC encounter as a result.

[Aesir]

So after reading this I am not sure if RadAlt will be good for your white out conditions over glaciers.

True RADALT can missread somewhat but in my experience flying many different helicopter types with RADALT the error is no more than 50-70 feet over loose snow or in some glacier conditions. Most of the time it is very accurate but one has to be aware of the errors and use secondary means of confirming altitude over ice at very low altitudes.

$12K is worth it expecially in the GX where you can use the integrated panel to give you voice altitude warnings. It also works with the barometric altimeter but much more accurate with the radio altimeter.

[olymbec]

I am going to try and find a helicopter in the area with a RadAlt and fly the helicopter and see exactly what information I am receiving. Since I never flew with this tool before I would like to try it before committing to it. I would love to hear from pilots who have flown with RadAlt and get their opinion on the pros and cons of this option. The cost factor is not what is preventing me from making a decision. With the new GX the HTAWS is also a feature which gives a tremendous amount of information as well.
I will fly her for a while as is and hopefully with some more cornet information and opinions I will be bale to make a proper decision for my exact needs.

[dammyneckhurts]

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[Squeaks]

olymbec,

Given the choice of radalt/no radalt I'd take a radalt any day, almost regardless of the tasking. Overwater it is invaluable and would be a primary reference over a baralt for all but a cruise altitude. Overland it becomes a better reference for many approach/departure parameters, having none of the lag found in most BarAlts. In emergencies it gives a precise indication for heights when in auto (flaring), LDP/CDP, etc etc.

[heated ice detector]

I think rad alts as we know them will a thing of the past, much cheaper and accurate to 5 mm are laser altimeters, not too sure if they are better for snow and water accuracy. I fitted a rad alt to the tail boom of a bk many years ago and you had to have two sensorl attachments a certain distant apart