Approach Clearance

[On Glideslope]

I never gave this much thought until it came up one day.


Background:

Safe 100: 4,000' ASL
Safe 25: 2,500' ASL
Procedure Turn Alt: 2,200' ASL
Minimums: 900' ASL
Last Clearance Alt: 3,000' ASL

ATC - "Flight XXX Upon interception of the localizer, cleared straight in ILS RWY 25, over to tower now good night"

Flight XXX - "Upon interception of the localizer, cleared straight in ILS RWY 25, we're switching to tower now, good night"

Question: When can Flight XXX leave 3,000' ASL?

[error_401]

Hmmmmm...

Two possibilities as you are already cleared for the approach.

1st
I assume that the procedure turn starts somewhere on the straight in approach leaving the localizer either left or right. So it would be safe to descend to 2'200 ft within the DME range of the turn if clearly defined. This of course is just an assumption of mine but I think it a safe course of action. But ... on an ILS see 2nd.

2nd
On a straight in to an ILS when cleared for the approach and you capture the Glide Slope and the interception point is verified you may start the descent.

[kabz]

think I would use something like :

"maintain last assigned altitude til established on a published segment of the approach" (then descend)

[Spitoon]

Here's an answer that works in the UK.

Assuming it is a procedural clearance - it sounds like it is - the pilot is responsible for terrain clearance in such circumstances.

On the basis of the info yo have given (and a couple of assumptions) , inside 25 miles you can descend to 2500ft. After leaving the beacon and established on the outbound leg descend to 2200ft. Maintain 2200ft until established on the LLZ and then descent with the glidepath.

As I say, a couple of assumptions made there. The straight in bit might complicate matters if you are picking up the LLZ without following a complete published procedure. Theoretically you need some form of intermediate approach fix in order to ensure that you are on the true glidepath (i.e. not on a theoretically possible reflected signal etc.).

[Intruder]

Spitoon:

I don't think your way is legal in the US.

The aircraft is on vectors to intercept the ILS final, with last cleared altitude of 3,000', above the min safe altitude (and assumed to be at or above the minimum vectoring altitude). He must maintain that altitude until established on a segment of the published approach -- in this case, the ILS loclizer.

Maintain 3,000' until established on the localizer. Descend on the G/S when intercepted.

If G/S fails, and DME is available to determine position, follow LOC approach altitude limits after intercepting the localizer.

[On Glideslope]

Intruder:

I would have to agree with you on this. I guess I should have specified that the flight was on vectors for an intercept to final. The PT alt. is superfluous information as this is going to be a straight in.

Your last assigned altitude was 3,000'. One must maintain the 3,000', until established on the localizer. The clearance stated "upon interception of the localizer, cleared straight in ILS Runway 25". That would mean the approach (any further descent) may not commence until established localizer inbound.

That was how I interpreted the clearance.

Thanks for everyone’s input.

On Glideslope

[quid]

OG and Intruder,

FWIW, I'm in 100% agreement. You MUST be "established" prior to leaving 3000.

[Duke of Burgundy]

On Glideslope - In the UK we are not permitted to use the phrase "cleared for the ILS" when radar vectoring to the localiser. The reason for this is that in the past pilots have taken such a clearance as permission to descend to the altitude at which the procedure commences irrespective of the actual cleared altitude.

We either have to wait until the pilot reports established on the localiser before giving descent clearance on the glidepath or use the phrase " XXX when established on the localiser descend on the ILS."

[Spitoon]

One of my assumptions was that it was a procedural clearance.

If it was vectors then the answer is quite straightforward (in the UK), as others have said, maintain 3000ft, intercept the LLZ and then when the GP comes in leave 3000.

As DoB points out, we use non-ICAO phraseology in the UK in order to clarify the meaning of the clearance.