ILS intercept altitudes

[John Collins]

Thanks Dave

 

[Palmpilot]

The 95 degrees F is at the airport. Standard lapse rate is used from there. In LA an inversion is common, so the real altitude deviation can be worse.

And the record high temperature for Los Angeles is at least 112 deg. F.

From the Instrument PTS:

I mis-remembered.

It's odd that the PTS allows altitudes lower than some of the ones depicted as minimums on the charts.

 

[aterpster]

And the record high temperature for Los Angeles is at least 112 deg. F.

That is an extremely unusual event. The high temperatures are typically in the valleys and LA airport is cool and moist under coastal influence.

 

[Palmpilot]

That is an extremely unusual event. The high temperatures are typically in the valleys and LA airport is cool and moist under coastal influence.

Makes sense, but one still needs to watch those stepdowns.

 

[AlvinLamar]

As far I know the final approach fix on an ILS is glide slope intercept.But I really confused can anyone help me with more information about the FAF and ILS intercept altitudes.

 

[aterpster]

As far I know the final approach fix on an ILS is glide slope intercept.But I really confused can anyone help me with more information about the FAF and ILS intercept altitudes.

The profile view of:

FAA charts, the lightning bolt

Jepp charts, the beginning of the ILS "feather."

 

[coma24]

I've found, at least lately, that they'll get you do the altitude they want, 5,400 for example. Then even though the ILS intercept altitude is 5,000 they'll say "Maintain 5,400 until established cleared ILS 32." The last approach I flew about a week ago was at RAP and that's what it sounded like. Notice you're well above 5,500 even if you're not getting vectors to final, but they put you at 5,400 before clearing you on the approach. I think I was cleared a couple miles from RANCH. Glide slope came in like it was supposed to.. heck even saw the marker beacons, never shot an ILS with operative beacons before.

http://155.178.201.160/d-tpp/1306/00877IL32.PDF

There is absolutely zero requirement for the ATC assigned altitude to match the glideslope intercept altitude. They're two very different phases of flight.

Prior to being established on the localizer, you're on a random vector from ATC. They are responsible for your terrain clearance, and the MVA is going to be as low as they can get you. Under these circumstances, (random vector) they are also legally responsible for providing you an altitude to maintain until established on a segment of the approach.

The fact that they assigned you 5400 and the GS intercept is 5000 is unrelated.

Remember, the controller is not telling you what altitude to maintain until utilizing the glideslope for vertical guidance. The "until established" is a LATERAL reference of the localizer. So, you join the localizer, then you continue the approach from that point, and if that means you follow step downs, then that's what you do.

The purest example of this case is to consider something like the LOC RWY 27 approach at SAN (or any other LOC approach, really). The phraseology for the vectoring and approach clearance from ATC is going to be the same whether it's a LOC or ILS approach.

 

[aterpster]

There is absolutely zero requirement for the ATC assigned altitude to match the glideslope intercept altitude. They're two very different phases of flight.

Yes, but, they are supposed to turn you onto the localizer at or below the G/S and not below the G/S intercept altitude (P-FAF).

7110.65, Para 5-9-1

 

[coma24]

Agreed, my point stands, though. I was trying to decouple the altitude to maintain until established on the localizer from the glideslope intercept altitude.

 

[HPNPilot1200]

Here is a link to InFO 11009 which I believe is relevant in this discussion.

Regardless of cause, pilots are cautioned to adhere to published step-down fixes located outside the Final Approach Segment on an ILS approach. If a pilot elects to follow the glide slope while outside the Final Approach Segment he should be fully aware that this technique needs to be closely monitored and, if necessary, action must be taken to meet all stepdown altitudes. Examples of airports where multiple altitude deviations have occurred include, but are not limited to; LAX, ORD, ATL, SLC.

 

[aterpster]

Here is a link to InFO 11009 which I believe is relevant in this discussion.

That is it. However, they fail to mention that following an uncompensated Baro VNAV path until the P-FAF is the active waypoint will also resolve the problem. This applies to the G-1000 and many full-press FMSes.