Glideslope Antenna Reflector Design Change

[kontiki99]

Looking for substantiation to replace a hollow tube antenna reflector element with one made from solid round stock. My background with these models in rusty to non-existent. Anybody know of good reference to come up to speed quickly. These antennas are mounted on NLG, Ground personnel are killing these things with tiedown chains.

Thanks

In theory, there is no difference between theory and practice; experience suggests that in practice, there is.

 

[ncaero]

Pull the analysis/substantiation for the currently installed equipment. You might find the margins will support the added weight without redesign; if not, you will at least have a starting point.

 

[kontiki99]

Thanks ncaero,

I wish I had access to the design data. I'm at the operator level looking thinks over after many hands have been in the pie. Looks like replacing them is now a non starter now any way.

They are mounted behind the ILS antennas, all on the nose landing gear. Ground handlers bend them with tie down chains. The current issue is, if the reflector behind the left ILS antenna is bent, does it affect the reception pattern of the RH antenna?

Tendency most casual observers have is to discount it as obviously no. My concern is that the whole assembly is very irregular and you just never know how all the nulls and reflections affect each other.

Absent data, can bending the reflector materially change the receptioon on the antenna all the way to the other side? With no data, for a safety critical system, I think we have to assume yes.





In theory, there is no difference between theory and practice; experience suggests that in practice, there is.

 

[debodine]

As you probably already know, the Glide Slope carrier frequency band is approximately 329 MHz to 335 MHz. At that frequency it is very easy to get squirrely reflections and lobes that can do funny things. However as long as both antennas get the RF carrier without disruption, they both should still be able to decode the 90 Hz and 150 Hz directional signals.

My recommendation would be to have a couple of ground handlers fired to make the others pay attention. Alternatively, make them pay for damaged antennas. But of course both options require them to be caught with the evidence.