When ATC directs a lower-than-published glide slop/path intercept altitude?

-According to jeppesen Airway ManualYou are referring to the "platform" altitude. The altitude on the profile view that intersects the ILS glideslope.



It is not unusual for this to happen provided the airport is VFR. If the airport is below VFR limits approach would most likely directly you to fly the ILS from some point prior to the final fix. The important point is maintain terrain awareness during vectors and if in doubt ask the minimum vector altitude for your position. ATC would ensure you are at or above it, but it doesn't hurt to ask.



Always maintain situational awareness by monitoring your position relative to terrain and obstacles using available navaids, GPS mapping and the Min Safe Altitude (MSA) altitudes shown in the MSA circle.
At what part of the approach? The answer depends on several issues. As long as ATC clears terrain and obstacles it is not that unusual to be given an altitude to intercept from below a glide slope. Without knowing the particulars of the approach, there is no easy or correct answer.



If in doubt, you can always "verify" with ATC the altitude given and request a different one. Rarely have I seen ATC issue a dangerous clearence, I have often seen them issue one that clears me to a much lower than "normal" altitude to begin an approach. If the level given clears everything there isn't any problem with it.



Here is a good article for your reading http://progressiveair.weebly.com/1/post/鈥?/a>

From that

"The following additional advisory language will be added to the AIM 5-4-5 b:



2. The ILS glide slope is intended to be intercepted at the published glide slope intercept altitude. This point marks the PFAF and is depicted by the 鈥渓ightning bolt鈥?symbol on U.S. Government charts. Intercepting the glide slope at this altitude marks the beginning of the final approach segment and ensures required obstacle clearance during descent from the glide slope intercept altitude to the lowest published decision altitude for the approach. Interception and tracking of the glide slope prior to the published glide slope interception altitude does not necessarily ensure that minimum, maximum, and/or mandatory altitudes published for any preceding fixes will be complied with during the descent. If the pilot chooses to track the glide slope prior to the glide slope interception altitude, they remain responsible for complying with published altitudes for any preceding step-down fixes encountered during the subsequent descent."