Question about ILS/DME

[nosehair]

So, if you fly the back-course upside down, will the windshield wipers still work?

 

[Princedietrich]

Dude, your plane has WIPERS?!

 

[nosehair]

for the oil over-spill when flying upside down.

 

[VW Pilot]

No Inverted approaches for me......

 

[epic!]

for the oil over-spill when flying upside down.

you only get in when flying inverted. lucky.

 

[Amish RakeFight]

...by the way there's also a marker sensitivity switch which should be checked along with the marker lights. Before executing the ILS, one of the checks is to ensure that each of the three markers light up. The markers are sometimes refered to as "fan markers" and only while above the marker will you hear the specific morse code identifier for each. By setting the sensitivity of the fan marker, you can adjust how long the dots and dashes of morse code go on for. A low sensitivity will allow for a shorter duration of the marker compared to the high sensitivty where the marker signal is picked up further away and sounds for a longer time as you traverse across each marker.

 

[Amish RakeFight]

A couple of other things.

The reason there are even markers are to provide you "milestones" along the approach as you descend on the ILS.

Normally, glideslope intercept is considered the FAF for the approach. This usually occurs before reaching the OM although one can theoretically intercept it at an altitude concurrent with the OM GS intercept altitude. On non-precision approaches, you'll use the OM as the point where you begin timing the approach and where you'll start a descent down to your MDA (minimum decision altitude).

For a CAT I ILS approach which allows for a 200' DH, the MM (middle marker) would correspond to this altitude. IOW, the MM tone can be used as a backup of when to commence the MAP or whether to continue on and land.

For a CAT II approach an inner marker might be installed between the landing runway and the MM. It would also correspond to the DH on this type of approach and make a distinct morse code informing you of your position along the approach.

 

[lawfly]

"DME lights"?

 

[nosehair]

"DME lights"?

Yeah, he means Marker lights - we think. Sort of a logical misstatement. The markers are at a known measured distance.

 

[nosehair]

...only while above the marker will you hear the specific morse code identifier for each.

Actually, there's not a morse code identifier. It's just a continuous series of dashes, or dot/dash, or dot/dot. The markers are also differentiated by tone and time between dashes and dots.

The Outer Marker: (low tone)Doh,..Doh,..Doh,..
The Middle Marker: (high-middle tone) Dah,Dot,Dah,Dot,
Inner Marker: (high pitched shriek!)Deet!Deet!Deet!Deet!