ILS Approach Clearance
 

ILS published procedure to RWY 99 starts at FIX / 3000 ft.

"Flight A, proceed direct FIX, descend to 6000 ft "

"Flight A, cleared for ILS approach RWY 99"


Questions :

1. Is flight A cleared to descend from 6000 ft to 3000 ft ?

2. Will flight A ask fir clearance to descend from 6000 ft to 3000 ft ?

3. Will flight A continue descend to 3000 ft or will it maintain 6000 ft until intercepting/establishing on glide slope ?


Please refer if it's a pilot or ATC opinion ...
Thanks

1. Yes
2. They might do since it's a reasonable drop, but they don't have to.
3. They can do either, but it would be an interesting procedure that allowed them to establish at 6000'.

(ATC opinion)

1. Yes
2. They might call leaving but don't have to.
3. I would anticipate the former

ATC opinion

1. No, at least in the US. Not until on a published segment of the approach or with further ATC descent clearance. Some may take cleared for approach as an inferred clearance to descend to the published altitude at the fix, but its not. Again, this applies to the US.

2. Likely yes unless the fix is quite a distance from the runway and losing the extra 3 thousand wouldn't be hard.

3. Remain at 6 until receiving a clearance for lower. Not so much to your example but it comes down to technique if one joins the GS further out and cross checks altitude at published fixes or if they descend to the altitude specified in the clearance or on the chart.

Pilot viewpoint.

As to number one, it changed to a published segment due to a crash back in the 70's I believe, perhaps TWA.

Rather than just "yes" or "no", I'd appreciate a reference to the regulatory document (e.g. MATS, PANS-ATM etc.) that confirms the answer to 1. I can't find anything, except in the AIM (5-5-4 a 3 (b)) to support West Coast's assertion.

Reference
 

West Coast's information agrees with the FAA Order 7110.65:

Chapt 5, Sect. 9

Controller/Pilot

ATC CHAT 24/7

Have experienced a similar situation; notified procedure had the fix at 5 dme 1600'Alt. When radar vectored, the a/c were at 2500' Alt before being descended to 1600' by the radar controller. Procedurally, planes levelled at 2000' ALt for terrain clearance until established, then when within 10 dme of the airfield, descending to 1600' Alt before the fix.

I never had a pilot descend from 2500' to 1600' without clearance but this was radar control service within class D airspace in the UK.

The answers will vary from country to country, control or advisory service, airspace type.

I (as a pilot) would love to know this answer per country. I know that in some countries, approach clearance includes descent clearance to approach altitude, but in some others it doesn't.

I've tried to find out but it's difficult to get it for most countries.

the clearance is missing something, they usually say clear for the approach and maintain ALT(6000) till establish. meaning once establish in the localizer you are clear to intercept the glide slope.

But what if they don't? They hardly ever use that phrase.

West Coast said,
Right on the money on that one. December 1, 1974. TWA 727. Not an ILS, but rather, VOR/DME 12 at IAD. NTSB, while noting the fact that the crew should have taken a better look at the approach plate, came down hard on the FAA for poor procedures and phraseology. Short version, cleared for the approach, started down from 7000 and ran into a ridge (a secret, government ridge, no less) 25 or so miles out from the airport at 1675 msl.

I’d recommend this accident report to anyone with an interest in this kind of thing. I’ve been through it many times and still find more each time I revisit it. Caution… reading it may make you very angry. Also, see “Sound of Impact: The Legacy of TWA 514” by Adam Shaw.

Quick related question.

In the example given is there a published hold at the fix where the aircraft could loose the height?

If there is a hold then the mater is further complicated by having the further possible option depending on the pilot and terrain of;

Enter the hold at the last cleared level and descend in the hold.

Also, is the aircraft already on the centerline or is it going to intercept at the fix.


As for my position (As a pilot)

a) Unless published as otherwise, the glideslope is only useable within 10nm from the runway. At 6000ft, and a MSL airfield the 3deg slope is intercepted at about 18nm.......well beyond the useable range of the glideslope.

Thus, while being "cleared to make the approach" I will request clearance to leave 6000 before I do.

I will plan to make this descent at an appropriate time so that I can firstly remain terrain safe and secondly if possible reach the fix altitude without having to go round the hold. (Ideally at about 300ft/nm).

Other factors could be staying a little high initially to avoid terrain turbulence or some low cumulus.

So basically, I will not descend without checking.............but the time at which I check (request) can vary from day to day and flight to flight so.....I would not expect such a clearance from ATC if they had traffic below which prevented the commencement of descent when asked (atleast 1000ft to get things started).

Regards,

DFC

Further to the above, a fellow pilot has also asked the very important question-

Is the fix you refer to on the airfield and require an outbound plus procedure turn or base leg or racetrack procedure?

I didn't think of it but is has been pointed out to me that in a procedural environment (not being radar vectored) it can sometimes happen that the aircraft passes through the localiser and glideslope while tracking to say a beacon/fix on the aerodrome where the procedure actually starts.

I have been to a few places where the beacon is approached along the localiser but the MSA prevents descent low enough to establish for a straight-in stabilised approach and we have to ignore the glide as we pass through it while tracking to the NDB on the feld.

Sorry to have assumed that the fix you referred to was some form of Centre Fix.

So many posibilities, so little time!!

regards,

DFC