Radar Altimeter; alarm sound?

[lionheart]

Hey guys,

Im doing a Radar Altimeter. Yesterday I looked all over for information on how they work and found nothing about if they have a sound alarm. They have a small light that comes on, labeled DH, but nothing about a sound.

Anyone know if they do make a sound and if so, what it might sound like?

From what I gathered from the manual, you push 'test' and the system turns off the Altimeter system or radar, so that flag should flip down when test is depressed. I would think the alarm would also sound off during 'test' mode. (If it has a sound to it).

 

[rpmc]

Bill,

Yeah, some have capability of a short duration audio output at Decision Height. Your attached pic looks like a Collins ALI-55, but if you were designing a similar Bendix/King, Honeywell radalt unit, then you could refer to this:

Honeywell KRA 405B Installation Manual

page 2-6.

And, what does it sound like?

587 Hz Tone

... the music note "D"

Here is an old brochure of another Bendix/King Radar Altimeter, the KRA 10A. It also discusses operation of the audio tone. Between these two publications, you should be able to accurately replicate the operation of at least the Bendix/King line of radar altimeters:

Bendix/King KRA 10A Radar Altimeter

Now, if you want to build a very "tricked-out" radar altimeter, then add radar altimeter unlocking error as a function of terrain reflectivity based on (A:SURFACE TYPE, enum) and high bank angle (A:ATTITUDE INDICATOR BANK DEGREES, degrees). You will have to come up with something original to model unlock due to loss of reflectivity, but that shouldn't be hard for anyone who has designed an electric plane before. Only joking.

If your project grows into a GPWS/TAWS, then certainly audio would be important for realism.

Bob

 

[lionheart]

A thousand thanks Bob.

By the way, Luka just posted a great way to do Reflectivity Failure for pitch and bank.

This page; http://www.fsdeveloper.com/forum/showthread.php?t=428739

Code:

<Value>
(L:RA_Active,bool) 
(A:PARTIAL PANEL ELECTRICAL,enum) 0 == and 
(A:PARTIAL PANEL AVIONICS,enum) 0 == and 
if{ 
	0.45 5.83 (A:Plane bank degrees,radians) rng 
	(A:Plane pitch degrees,degrees) abs 25 > or 
	if{ 762 } (* max *) 
	els{ (A:Radio height,meters) } 
} 
els{ -5 } (* fail *) 
-5 max 762 min (* limits *) 
</Value>

Bill

 

[rpmc]

By the way, Luka just posted a great way to do Reflectivity Failure for pitch and bank.

Great! Can't wait to see what you come up with for terrain reflectivity

Bob

 

[SkippyBing]

Of course if you're being really accurate you allow for the RADALT over reading when you're not in level flight...