The International Cessna^® 170 Association

Good Afternoon Everyone,

Still moving forward (slowly) on my panel project and I have a couple of questions about my KX-125. From what I can dig up on the webb, this radio will "channel" a seperate glideslope receiver and "drive an external CDI, with or without a converter, such as the Bendix/King KI 208".

Does this mean in order to drive a glideslope, no matter if it's in a stand alone NAV head, or an HSI such as the Century NSD 360 - I need a seperate glideslope receiver, and does the "Channel" mean that the KX-125 will send the signal from the G/S receiver to the indicator?

One more - does that also mean the KX-125 would allow the G/S channel selection?

Long story short - can I use the 125 to drive a Century HSI, or am I going to have to get another radio / NAV head combo - or... consider a NAV 122 ???
Too many choices

Hope everyone is well....


Kyle T.

Without addressing the KX125 specifically, ... when a nav radio is said to "channel" a glideslope receiver, that only means it will "converse" with the GS to co-ordinate the output signals of both receivers. (A VOR receiver is a navigation receiver which operateds in the VHF-band, while a GS is a seperate receiver which operates in the UHF-band. The UHF portion is "tied" with the VHF portion in a pre-arranged pairing. This assures that an ILS at one airport does not interfere with that of another airport nearby. (Ever hear of "false" GlideSlopes? It's one reason that a pilot should ALWAYS confirm that the GS being used displays "on-glideslope" at the appropriate, published altitudes along the course, ... i.e., if your approach indicates you should be at 2440' MSL at the outer marker, and you see that your altitude is 3100" at that point... you are receiving a false GS. I"ve seen THREE different GlideSlope indications on the same approach to KSGR (near Houston) due to reflections off a cooling-pond associated with the electric-utility plant nearby.)

Anyway, The KX125 has an internal, LCD readout for azimuth (CDI-Course Deviation Indicator) and requires an external nav-head, coupled with a seperate GS reciever, to display a full ILS.

Thanks George... So if I understand you correctly, the way this works is that the KX 125 would read the signal picked up by the glideslope receiver, and then send it to an indicator, at the same time it sends its own NAV signal to the same receiver.

Further (If I have this right) setting an ILS freq. on the KX 125 tells that glideslope receiver which frequency to look for, and then once found the above process takes place. If the ILS signal on the approach goes down, and it turns into a localizer approach, then is the 125 is still getting that localizer signal from the glideslope receiver and not it's indepentant NAV function?

I'm just a bit confused as when I dial in the ILS freq at Provincetown (PVC) 111.10 - I receive on my KX 125 the localizer signal, and get the correct localizer indications on the internal CDI.

Thanks - Kyle

Close...but no cigar. The KX125 (and most other receivers) simply t ell the GS rcver which LOCalizer freq it is tuned to. The GS rcver then tunes it'self to the paired UHF freq and sends the GS signal to the resolver within the nav-head. The KX 125 is powering the LOC needle on the nav head. If t he GS rcvr fails...then the only thing lost is the GS indication. The KX125 will still be driving the LOC signal on the nav head.

George, Thanks for clarifying. It's all starting to make sense. My next steps are to take the 3 basic equipment combinations I've come up with, list all the needed equipment to make it work and decide which way to go. When I do, I'm trying to be realistic and knowing the more individual parts and pieces you have in a system (couplers, wiring, trays, mounts etc.), the more work involved for the avionics shop and hence the cost of the install goes up.

My panel is currently a 7 hole, and the 8 hole panel we are making is just about done so I have some flexability in the configuration.

The three are:

1) Narco NAV 122
2) My KX 125 / Individual NAV head
3) My KX 125 / Century NSD 360A HSI - non-slaved vacume driven

Comments welcome...

Thanks again for the explanations

I had an early-Nav-122 in my C-206 and it did good service and takes up no additonal space than an instrument, should you require a full ILS capability.

However, from an economics point of view... what is the reality of your need for a full ILS? 99% of all your flying will never require a full ILS and the few days the wx is so bad to require a GS you probably won't want to fly a single-engined airplane anyway. Therefore, statistically it's the least economical choice you could make. A localiser only, or a GPS will get you into virtually all airports with approaches except on the days so bad you don't want to fly anyway....and the GPS will be useful not only on approach (the ONLY place a GS is useful) .... a GPS will also be useful on departure, climbout, cruise, descent, AND approach. Just my view.

and the GPS will be useful not only on approach (the ONLY place a GS is useful) HMmmmmm???? The ONLy place a GPS is useful? - Well if it came from George it must be so.

Joel
N3437D

n3437d wrote:and the GPS will be useful not only on approach (the ONLY place a GS is useful) HMmmmmm???? The ONLy place a GPS is useful? - Well if it came from George it must be so.

Joel
N3437D

My point is that a GPS is useful not only on approach..but on departure and cruise AND approach.... and that GS (Glide Slope) is ONLY useful "on approach". It's useless ALL the rest of the flight.

What didn't you understand, Joel?