Cleared a STAR, how low can you descent ?

[TheDrop]

Say you are cleared inbound a fix to a certain altitude. At this fix, there is a STAR, leading to your destination. You are cleared this STAR, but there are no specific instructions in the STAR plate of what altitudes and/or flight levels you may descent to.

On the tracks of the STAR, minimum altitudes/FL's are normally given, these are to my knowledge minimum altitudes for obstacle clearance.

I have talked with collegues about this, and there are two viewpoints of "the truth":

1) If there is a level or altitude on the STAR, you can descent when you want to that altitude/level.

2) Even when cleared the STAR, you cannot descent before cleared to do so, unless it is stated on the STAR that you can do so.

Which one is correct, why, and is there any references to specific regs about this anywhere ?


Also, another question, when under radar vectors, who is responsible for keeping your minimum obstacle clearance to terrain ? Will ATC always add allowances for wind over mountaineous terrain, QNH and temperature ?

1) When ATC tells you to descend on radar vectors, you are always safe to descent to the given altitude/level.

2) The commander is always responsible of keeping minimum obstacle clearance, and informing ATC if a given level is too low.


To both questions, I say 2) as answers.

I would very much like to hear whether you agree or disagree.

Thanks.

[Three-Twenty]

Agree - min altitudes on STARS are normally there to maintain separation from terrain or other air traffic routes.

They do NOT work in the same way as the altitudes on the Approach plate when cleared an approach eg. descend to 1800' when beyond 7d from fix etc. etc. I suspect this is where confusion has arisen.

If in doubt, check with ATC!

[AfricanSkies]

Agree - both 2).

[reynoldsno1]

Radar vectoring is achieved by issuing a pilot specific headings to maintain a desired track. The controller must, therefore, take into account the wind.
When vectoring IFR flights the controller will issue clearancs so that the required obstacle clearance exists at all times. In the UK those clearances are specified in the AIP (ENR) section 1.6

[ManaAdaSystem]

Hi Drop!
When cleared a STAR, you can descend to the altitudes given on that STAR, unless ATC has given you other instructions. I frequently get "cleared xxxxx B arrival, maintain FL so and so until xxxxx. Then you may fly the given track, but maintain alt until point xxxxx, or sometimes until ATC gives you a lower alt. This is sometimes a bit confusing.
Are you also cleared for approach when cleared a STAR? This is a tricky one, as the rules vary from airport to airport. A clearance to fly a STAR will at some airports also mean that you are cleared approach. At other airports you must enter the hold where the STAR terminates, unless given a specific approach clearence. Ask!

The controller is responsible for adequate terrain separation when vectoring, but the ultimate responsibility rests with the commander. ATC will NOT correct for wind, temp or QNH, and you must reject any clearance to altitudes below your corrected minimum altitude. Some controllers have no idea what corrections you are talking about.

[Roadtrip]

Trying reading the AIM, Section 5 and Section 4 5-4-1a1. For questions like these AIM usually has the answer. Also, try terps.com -- good site talking about instrument flight procedures and Terps criteria. While most of the world's controllers know they are responsible for terrain clearance while under radar contact, that's not necessarily the case in South America. I am always VERY VERY VERY VERY careful about accepting anything less than Min Safe Alt from a controller. A prudent choice in South America is to NOT use radar vectors (Min Sector Altitudes), but instead fly the entire letdown procedure. Controllers in other parts of the world have been fine (although I haven't flown in Africa), but don't trust South America.

[This message has been edited by Roadtrip (edited 15 September 2000).]

[This message has been edited by Roadtrip (edited 15 September 2000).]

[alosaurus]

Agree with manaadasystem one controller at a large Irish airfield descends you to 3000' downwind of a ridge line just under 2000'.Dont accept it serious rotor problems with southerly winds.

[mustafagander]

As I understand it, a STAR clearance is only a lateral clearance to navigate via a certain route. Unless and until you get clearance to a lower altitude descent is NOT authorised. There may be, however, crossing restrictions to comply with after a descent clearance is received.
This is how it is in LAX to my certain knowledge.
See also Oz AIP ENR 1.5-36 para 12.2.5.
In the USA we used to be cleared via "profile descent" which incorporated both lateral and vertical navigation in the one clearance, but these were separate from STARs.

[ManaAdaSystem]

Youre right Mustafagander. And wrong. The rules vary from country to country.

[Grandad Flyer]

This should really be in the ATC Forum. In fact both these subjects have been discussed in depth over the last few weeks.

[TheDrop]

Thanks, Grandad, I did not know it existed there in ATC. I started this topic in R&N, and a moderated moved it here (without writing where it was moved to - or where does it say ?).

The topic you talk about is probably http://www.pprune.org/ubb/NonCGI/Forum6/HTML/000419.html

Very informative, so thanks.

[bizjet pilot]

SOmeone above posted the following.

"A prudent choice in South America is to NOT use radar vectors (Min Sector Altitudes), but instead fly the entire letdown procedure."

I very much agree. Two reasons. (1) Both copilot and captain know where they are and what minimum altitude is necessary. Not so if being vectored. (2) Knowing (1) requires virtually no common language with the controller except "cleared for the approach."

Much safer daytime. And, at night over mountains in the third world, I would actively refuse radar vectors. No reason for them really. I've got TCAS.

[This message has been edited by bizjet pilot (edited 21 September 2000).]

[TheDrop]

Bizjet pilot,

I s'pose you mean you have GPWS ?

[bizjet pilot]

I'm delighted to tell you that I've got GPWS, Enhanced GPWS (GPS mapped terrain warning system) as well as TCAS/ACAS.

But I still don't care for vectors at night in unfamiliar places, especially outside the lower 48 states. Flying only there can coax you into habits that may frighten you elsewhere.

Mildly irritating when the other fellow/woman wants to do a visual approach, squinting through the windshield etc. There are two IRSs, a gyro-powered AHRS, two FMSs amounting to $1 million in avionics. But he or she wants to use the Model 1A eyeball to find the airfield. (Don't mind me, I'm on a rant.)

[skynet737]

Answer to QUES 2 Drop... youre absolutely correct... the responsibility for terrain clearance is still with the PIC.... if ATC assigns you an altitude lower than your MSA on a radar vector... you should confirm if it is at or above the MVA(min. vectoring altitude...).... available in the AIP of the place.. AGA section.

[Stamatis]

And, at night over mountains in the third world, I would actively refuse radar vectors.

Bizjet Pilot, can you actually deny Radar Vectors? I am a non-pilot so excuse the ignorance.
What do you fly instead? The entire procedure exactly as published? What will your clearance sound like in such a case?

[This message has been edited by Stamatis (edited 24 September 2000).]

[Oz_Pilot]

As I understand, in Oz a controller can vector you but any given heading must keep you clear of terrain for at least three minutes, and they need to talk to you every 30 seconds if this is the case (allowing time to recognise comms failure and so on). As a pilot, don't have MATS here so... but the short answer to question 2 is that you can trust any radar vectored descent.

[mustafagander]

Oz_Pilot,
You can only ever trust radar vectors to the extent that you're prepared to bet your life that his equipment and training are adequate.
You've gotta be careful, real careful or else the ground may rise up and smite you mightily.

[TheDrop]

Another version:

ATC: "Descent 5000'

and later

ATC: "Follow the ABC 1 D arrival, report established on the localizer"

Are you still restricted to 5000 feet, if there is no mention of altitude (other than minim obstacle clearence) on the STAR ?

If you are not restricted to 5000', is it then because the altitude restriction wasn't repeated in the subsequent ATC call ?

Would it make a difference if the ATC terminology differs like this:

a) "Cleared the ABC 1 D arrival ..."

b) "Follow the ABC 1 D arrival ..."

c) "Expect the ABC 1 D arrival ..."

and so on - One thing is if pilots opinion differ, but how about ATC - it is like some of them expect you to descent (by yourself) with minimum altitudes stated on the STAR, so even if they gave you an altitude restriction earlier on ?

I'd still say that "cleared approach" and "cleared (a STAR)" is NOT the same - cleared approach let's you descent, UNLESS, it is accompanied with a "stop descent at ...".

Let's get this straight, references to the appropriate documents would be informative !

[Royan]

If you are not sure , always check , this will save you from alot of trouble , so don't fall in the trap that different countries do it different,it is true at times , but be carefull and double check at unfamiliar areas,always know where you are ,it happened to me more than once that the Radar Had malfunctions, one of them at 1500 feet high speed ,ATC asked for intentions . Never assume ,otherwise you'll be in error.This is what I do beside knowing Rules and regulation, Diffrences of ATC procedures(JEPPESEN)at different countries,Revise Emergency procedures for that country as well.And very thorough planning for every flight .