I keep reading in the manual about the JS-4100 having a radar altimeter but I cannot locate it,  is anyone aware of a radar altimeter on this aircraft?

 

 

is anyone aware of a radar altimeter on this aircraft?

 

I believe it will show up on the PFD (attitude indicator or whatever BAe calls it) when the aircraft is below 2500 feet.

• Most radar altimeters can be controlled and adjusted,   never seen one like that before.

The radio altitude will display next to the attitude indicator (bottom right corner). The decision height can be adjusted by using the DH knob on the glareshield panel. Refer to page 30 in the Pilot Introduction PDF.

 the PFD (attitude indicator or whatever BAe calls it)

It's the EADI, same terminology as Boeing, ATR, McDD use for them. The screen below it is (no prizes for guessing this one), the EHSI.

 

 

It's the EADI

 

Thanks for the correction.

No problem, aviation is a soup of acronyms, some of which the manufacturers can't agree on!

Ok.....it seems that the decision height feature and radar altimeter are one in the same,  the names are interchangable,   so the decision height adjuster is what can be called the radar altimeter.....right? 

Sort of, but the terms are not interchangeable as they mean different things.

• The Radio/Radar Altimeter is the instrument that gives your height above the ground below you (simply known as height or AGL).
• Decision Height is a concept, it's the lowest you can descend on approach without having a runway visual reference, which you can set on most radio altimeters (or avionics packages in the case of the J41) so they provide you with a visual and/or audio warning (i.e. "100 above", "Approaching Minimums", "Minimums", "Decision").
  
  Basically, you can't let your radar altitude (aka height) be less than the decision height without being able to see some part of the runway (such as a light)

Ok.....it seems that the decision height feature and radar altimeter are one in the same,  the names are interchangable,   so the decision height adjuster is what can be called the radar altimeter.....right? 

Following on from what Chris said above, I assume you are used to a separate radio altimeter indicator with a DH adjust knob. The difference with EFIS equipped aircraft like the J41 is that there often isn't a separate radio altimeter indicator but there will be some means to select DH. The EADI combines a number of traditionally separate indications, including the RA.

Ok Kevinh,     I can understand the combining of features within the EFIS,   I guess I am just used to radar altimeter adjustment knobs,   that to me would be the whole Idea of having it on the aircraft as indication of a specific altitude reached,  but well taken on what everyone has said.  much appreciated.

The Rad Alt serves other purposes besides DH (although that is its primary function, it's part of the equipment required for CAT II and III approaches). For example, many GPWS functions are dependent upon it, as are the altitude callouts (e.g. "TERRAIN, TERRAIN" or "TOO LOW, GEAR" and "300, 200, 100").

Ok...that makes sense...thanks!

^{I found it,  the radar altimeter is always on,   this one has no adjustment.}

The radio altitude will display next to the attitude indicator (bottom right corner). The decision height can be adjusted by using the DH knob on the glareshield panel. Refer to page 30 in the Pilot Introduction PDF.

^{I found it,  the radar altimeter is always on,   this one has no adjustment.}

It most definitely IS adjustable, as PHXMD-11 has already said. The knob for it is on the glareshield with the EFIS controls and labelled "TEST", it's directly below the WX push button.