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Descend to MSA when "cleared approach"

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Descend to MSA when "cleared approach"

Old 3rd Sep 2016, 18:38
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Descend to MSA when "cleared approach"

Imagine this:

You are cleared on a radar heading to 4000 ft and you are outside FAF on an ILS approach. Approach control clears on this heading for the ILS approach. Platform altitude is say 3000 ft at FAF. Can you legally descend to the MSA before you are established? I can imagine problems if you did that at certain busy airports. I would normally maintain 4000 ft until the glide. Some people told me that "cleared approach" allows you to descend to MSA and disregard the previous altitude clearance. Opinions ?
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Old 3rd Sep 2016, 21:00
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Good question. My take is:

1) If you were on a published arrival (STAR) and were cleared for the arrival initially, then further cleared to onto the ILS, then you can descend with the published arrival, which presumably would be 3000feet. Note, you must still maintain all step down height constraints as published.

2) On a radar heading the arrival is no longer in use. Therefore you cannot descend below the cleared altitude. At 4000, you need to be intercepting from at least 14nm away from glideslope. If you are being vectored inside that, ask for a lower altitude, reduce speed, configure early, be prepared to intercept from above and and above all, be prepared to ask for extra miles and go around.

3) Depending on your company, if VMC, you may ask for a visual approach whereby you can then descend at your 'leisure'. However you are not then cleared for the ILS approach, even though you will be using it as a reference.

Note, due terrain, some airports simply won't be able to descend you lower until you are clear of terrain. In this case, ATC should notify you 'standby for further descent'.

Hope that helps
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Old 3rd Sep 2016, 21:04
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In Spain, at least, once you are cleared for the approach you may descend to the platform altitude.
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Old 3rd Sep 2016, 22:50
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I'm with you on the STAR and request visual. It was not the piloting techniques I was after. The question was regarding case number two. On radar vector with altitude clearance and "cleared approach". Can you legally descend to MSA ? Why, or why not ?

Regarding descending to platform altitude (which could be below MSA) in Spain, where does it say that? I think you risk busting your terrain clearance.

On radar vectors ATC is responsible for your terrain clearance, as we know. Also for vectoring below MSA. What authorises you to leave the cleared altitude, because ATC says "cleared approach"? You could have a mountain below you but above platform altitude, between you and the FAF






Originally Posted by squawkident. View Post
Good question. My take is:

1) If you were on a published arrival (STAR) and were cleared for the arrival initially, then further cleared to onto the ILS, then you can descend with the published arrival, which presumably would be 3000feet. Note, you must still maintain all step down height constraints as published.

2) On a radar heading the arrival is no longer in use. Therefore you cannot descend below the cleared altitude. At 4000, you need to be intercepting from at least 14nm away from glideslope. If you are being vectored inside that, ask for a lower altitude, reduce speed, configure early, be prepared to intercept from above and and above all, be prepared to ask for extra miles and go around.

3) Depending on your company, if VMC, you may ask for a visual approach whereby you can then descend at your 'leisure'. However you are not then cleared for the ILS approach, even though you will be using it as a reference.

Note, due terrain, some airports simply won't be able to descend you lower until you are clear of terrain. In this case, ATC should notify you 'standby for further descent'.

Hope that helps
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Old 3rd Sep 2016, 23:03
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Let's get practical. You ask the question on here as to what you can do, or not. If in doubt ask ATC not prune. You are cleared, on HDG, to 4000' and cleared approach. This would suggest you are cleared to intercept the final track and descend on the procedure from 4000'. If you feel you will intercept the final track too close for 4000', i.e. be above the profile, you would ask ATC for further descent. If 4000' is OK for the distance at intercept there is no problem. It is not uncommon for ATC to forget to give you further descent, but is it necessary? Remember the PIC is responsible for navigating the a/c to a safe approach to landing. ATC is responsible for terrain clearance, but PIC has final responsibility for managing the energy and safety of their a/c. Situational awareness is the crew's responsibility. ATC can screw up as easily as you.
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Old 3rd Sep 2016, 23:26
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I agree with RAT 5 above. The part of the world I fly in, the answer is no. A clearance to 4000' followed by an approach clearance is a clearance to descend not below 4000' until established on the approach. If this will leave you high on slope, ask for further descent or a different vector. Joining an approach off a STAR shouldn't be an issue.

Can't speak for other parts of the world though.
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Old 4th Sep 2016, 02:04
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Originally Posted by president View Post
Regarding descending to platform altitude (which could be below MSA) in Spain, where does it say that? I think you risk busting your terrain clearance.
Can't remember, try the Spanish AIP. You can safely assume that the platform altitude is above the surrounding terrain and that where ATC clear you terrain will not be an issue.

What authorises you? That's what's they expect you to do!
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Old 4th Sep 2016, 03:14
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In the US, TW514 smashed into a ridge doing just this. Now, the approach clearance will be, "Turn (heading), maintain xxxx until intercepting, cleared ILS" or "maintain xxxx until established on a segment of the approach, cleared for approach". MSAs are sometimes procedural, sometimes emergency only.

GF
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Old 4th Sep 2016, 08:56
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Just to be clear. I know how to deal with energy, approach and landing. I am not looking for piloting advise. I am asking whether something is legal or not. Anybody with a legal reference ?
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Old 4th Sep 2016, 09:49
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You can safely assume that the platform altitude is above the surrounding terrain and that where ATC clear you terrain will not be an issue.

And if you are not under radar???
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Old 4th Sep 2016, 10:16
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I'm basically with Rat here and especially with his "if you are not sure, ask ATC" comment. But this is an unambiguous clearance. You have a heading, a level and clearance to join the ILS in the traditional way; localiser first. If you need a descent to allow an intercept of the localiser first you should ask for it. You were not cleared to descend to an intermediate level first.

The times when this type of clearance can become confusing is when you are on a heading to join an arrival procedure and at the same time cleared for the approach. This can happen in places like Marseille, Gothenberg, Alessund, Trondheim etc. Here you will be flying on own own below MSA (on an Arrival or Transition) and be responsible for your own let down (but according to the step down fixes on your charts). But you may descent because you have been cleared to do so.

PM
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Old 4th Sep 2016, 10:55
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Piltdown: Indeed. At BGY you start the approach at a FL over the VOR. You descend outbound to an Altitude and turn in descending further after a DME is passed, then intercept the ILS. Common for ATC to clear you to the VOR at FL and "cleared for approach". Why should radar talk you round & down the procedure? You follow the chart and they monitor you. Quiet, calm, relaxed and allows radar to give their attention to all traffic.
However, it was not uncommon for some airline crews, who were more used to being 'led by the hand', to ask, "can we descend?" ATC "you are cleared approach call finals." Only for the a/c to repeat the question. I guess confirming is safer, even twice, but which part of cleared approach from the VOR didn't you understand? May sound harsh, but it takes up radio time and makes one wonder.
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Old 4th Sep 2016, 11:16
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Originally Posted by RAT 5 View Post
You can safely assume that the platform altitude is above the surrounding terrain and that where ATC clear you terrain will not be an issue.

And if you are not under radar???
Then you'd be either visual or procedural. If you're procedural are you going to ignore level restrictions on the arrival and approach?
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Old 4th Sep 2016, 11:33
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Agreed.........
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Old 4th Sep 2016, 14:28
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president:

Just to be clear. I know how to deal with energy, approach and landing. I am not looking for piloting advise. I am asking whether something is legal or not. Anybody with a legal reference ?
As GF stated, it caused a CFIT for TWA 514 in 1974. Caused a regulatory change in the U.S. to maintain last assigned altitude until on a published route or segment of an approach. Also, in the U.S. MSAs are for emergency use only.

I've been in this business for a long time and this is the first time I've heard the term "platform altitude." That's not termed used in the U.S. Perhaps it is elsewhere. Do you know if there is an ICAO definition?
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Old 4th Sep 2016, 14:40
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What Piltdown has said is correct. You don't descend below cleared altitude unless cleared for full procedure on a published track like IAF to IF or fix with published descent altitude.
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Old 4th Sep 2016, 15:00
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GF:

In the US, TW514 smashed into a ridge doing just this. Now, the approach clearance will be, "Turn (heading), maintain xxxx until intercepting, cleared ILS" or "maintain xxxx until established on a segment of the approach, cleared for approach". MSAs are sometimes procedural, sometimes emergency only.
Attached is the chart used by the crew of TWA 514 on December 1, 1974.

Also, as you say, MSAs are not operational altitude in some countries. The U.S. is one of them. Also attached is a current RNAV approach in my area (KF70). The FAA discontinued sectorization of MSAs on RNAV charts. Note the altitude of the MSA and the profile altitudes of the procedure.
Attached Images
File Type: jpg
TWA 514 Chart.jpg (309.8 KB, 105 views)
File Type: jpg
F70.jpg (503.7 KB, 95 views)
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Old 5th Sep 2016, 01:38
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In the US, maintain last cleared altitude until established on an approach. FAA AIM Sec. 5-4-6:
e. The following applies to aircraft on radar vectors and/or cleared “direct to” in conjunction with an approach clearance:
1. Maintain the last altitude assigned by ATC until the aircraft is established on a published segment of a transition route, or approach procedure segment, or other published route, for which a lower altitude is published on the chart. If already on an established route, or approach or arrival segment, you may descend to whatever minimum altitude is listed for that route or segment.
Sec 5-4-7:
b. When operating on an unpublished route or while being radar vectored, the pilot, when an approach clearance is received, must, in addition to complying with the minimum altitudes for IFR operations (14 CFR Section 91.177), maintain the last assigned altitude unless a different altitude is assigned by ATC, or until the aircraft is established on a segment of a published route or IAP. After the aircraft is so established, published altitudes apply to descent within each succeeding route or approach segment unless a different altitude is assigned by ATC.
To reiterate that the use of MSA is NOT allowed in this case, Sec 5-4-5 says:
c. Minimum Safe/Sector Altitudes (MSA) are published for emergency use on IAP charts.
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Old 5th Sep 2016, 03:54
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Can anyone explain what it means "MSA is for emergency use only"? MSA is MSA, if you fly above it you won't hit anything - emergency, or not. What am I missing here?
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Old 5th Sep 2016, 08:07
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What am I missing here?
Just that the US meaning of the term differs from what you are probably used to. Not to derail the thread any further, but in FAA parlance, MSA is not a procedural altitude. It is merely an altitude which should keep you out of the weeds if you are off the procedural track and within 25 nm of the NAVAID depicted.

From FAR 97.3

MSA means minimum safe altitude, expressed in feet above mean sea level, depicted on an approach chart that provides at least 1,000 feet of obstacle clearance for emergency use within a certain distance from the specified navigation facility or fix.
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