Radar SID turn Altitude vs Diverse Departure tower instructions

RamRise

Well-Known Member
I know this discussion has been had ad nauseum on my company's facebook, which I'm no longer part of, but I wasn't able to find anything in a 30 minute search on the subject in other parts of the internet. so here goes...

When cleared for a SID, that prescribes a turn altitude other than the normal 400 above DER (see Chattanooga 6), if you are then subsequently given by the tower a vector departure during takeoff, and no concomitant altitude instructions, do you turn at 400', or the published MSL on the SID?
Doesn't the vector constitute a new/amended clearance?
The AIM says if a higher altitude is prescribed in a non rnav DP, turn at that altitude..but doesn't mention if vectors are given.

Some controllers will say "passing xxxx, turn right/left hdg xxx" with an altitude that matches the SID altitude, like in milwaukee. But this doesn't always occur. Some clarification would be appreciated in those instances? (without having to ask for clarification on freq, thank you very much ;0 )
 

RamRise

Well-Known Member
91.175f3 and f4
I think that's part of the equation. 91.175 f3- must use odp to get to mea. But is a radar vector an "alternate procedure" that is complied with and the altitude reverts to 400 afe?

91.175f4- obstacle requirements means turns no lower than 400 in vmc or 1000 in imc.
 

MidlifeFlyer

Well-Known Member
With no separate altitude instruction, I would follow the SID altitude. Here's why:

1. At its most basic, a SID is just a canned clearance. The SID instruction to climb to a certain altitude is exactly the same as if the clearance was read to you word by word. Plus, this one says you are going to receive vectors. So, your runway 20 instruction with, say, a vector heading of 180 from the Tower on takeoff is, to partially quote the instructions, "Climb heading 202° to 2200 before turning, thence...." fly heading 180. Without a new altitude specified, there was no change to the instruction to climb before turning.

2. Those obstructions, baby! You know, the ones surrounding the airport that are probably the reason for the climb before turning (they are also in the Takeoff Mins and ODP section)
 

gotWXdagain

Highly Visible Member
I’m gonna go with “alternate instruction.” A SID starts at the runway, so if they give you a new instruction, you aren’t on the SID until they put you back on it.
 

RamRise

Well-Known Member
I tend to agree with midlifeflyer

AIM reference is ¶5-2-8.b. which starts...

"What criteria is used to provide obstruction clearance during departure?
1. Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn..."


It says "unless specified otherwise" the sid specifies otherwise in this case.

The problem I still see is there are plentiful examples of recieving a RNAV sid in a pdc...then getting a vector (diverse departure) during the lineup; and we all know to turn at 400.

But it could be easily misconstrued when you're given a vector sid on your PDC or clearance, with an altitude specified other than 400 afe (uncommon but exists), and then recieve the vector on takeoff. Original question restated basically.
 

NovemberEcho

Dergs favorite member
When given vectors by tower, it replaces any previously issued SID clearance. The SID no longer exists in your clearance and any SID altitudes don’t matter. Forget the SID even exists. If they happen to give an altitude to turn out that matches the SID, that’s just for obstruction/obstacle clearance and is specific to that locale, it doesn’t apply anywhere else and is just coincidental.
 

RamRise

Well-Known Member
When given vectors by tower, it replaces any previously issued SID clearance. The SID no longer exists in your clearance and any SID altitudes don’t matter. Forget the SID even exists. If they happen to give an altitude to turn out that matches the SID, that’s just for obstruction/obstacle clearance and is specific to that locale, it doesn’t apply anywhere else and is just coincidental.
Makes sense, but I just can't find the source document/FAR/aim guidance that says it
 

NovemberEcho

Dergs favorite member
Makes sense, but I just can't find the source document/FAR/aim guidance that says it
Why would they need a regulation to tell you that? Subsequent clearances/vectors replace the preceding ones. If you’re given a heading to fly by tower after you had been given a clearance with a SID, they heading means you’re no longer on the SID.

If you were in the air and cleared direct abc, and then given a vector, you wouldn’t fly direct abc and then turn to the assigned heading. It’s the same concept.
 

RamRise

Well-Known Member
“Unless specified otherwise.”

ATC has specified otherwise.
Did you read the paragraph...it says turn at 400 unless atc specifies otherwise... a tower vector does not include an altitude typically so they haven't "specified otherwise". however a SID altitude in your clearance could be considered "ATC" specifying otherwise. Are we confused yet?


I think the "alternate procedure" point you made earlier is what you were trying to reiterate? and possibly what is ultimately correct to do.
 
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RamRise

Well-Known Member
Why would they need a regulation to tell you that? Subsequent clearances/vectors replace the preceding ones. If you’re given a heading to fly by tower after you had been given a clearance with a SID, they heading means you’re no longer on the SID.

If you were in the air and cleared direct abc, and then given a vector, you wouldn’t fly direct abc and then turn to the assigned heading. It’s the same concept.
Yeah I get it. Just the looming feeling that obstacle clearance is the onus of the pilot at times, and atc at other times. Though I believe once you receive vectoring they are assuming obstacle clearance, vs simply hearing "radar contact"

In other words, the fact that tower is providing vectors means they are ensuring obstacle clearance...I suppose
 

T/O w/FSII

Well-Known Member
Yeah I get it. Just the looming feeling that obstacle clearance is the onus of the pilot at times, and atc at other times. Though I believe once you receive vectoring they are assuming obstacle clearance, vs simply hearing "radar contact"

In other words, the fact that tower is providing vectors means they are ensuring obstacle clearance...I suppose
You do know they have a MVA to follow right? A minimum vectoring altitude.
 

T/O w/FSII

Well-Known Member
however a SID altitude in your clearance could be considered "ATC" specifying otherwise. Are we confused yet?
A sid altitude has nothing to do with anything when your not on a sid. Also a sid is absolutely NOT ATC.

Pro tip: The PIC is always responsible for terrain and obstacle clearance. Always.
 

NovemberEcho

Dergs favorite member
This might help:

 

RamRise

Well-Known Member
I mean... this topic really is as complicated as I make it out to be when you start to dig into it, even if the answer is straightforward.
 

RamRise

Well-Known Member
Pro tip: The PIC is always responsible for terrain and obstacle clearance. Always.
It's more nuanced than that... and GPWS is a last resort measure if that's what you're alluding to.
Can you proclaim you calculated minutest of obstacle clearance and TERPS requirements for every single takeoff and know every moment you meet the requirements?

Just read the article... diverse departure is different from diverse vector area is differnt from minimum vectoring altitude. The rabbit hole is indeed deep.
 

z987k

Well-Known Member
It's more nuanced than that... and GPWS is a last resort measure if that's what you're alluding to.
Can you proclaim you calculated minutest of obstacle clearance and TERPS requirements for every single takeoff and know every moment you meet the requirements?

Just read the article... diverse departure is different from diverse vector area is differnt from minimum vectoring altitude. The rabbit hole is indeed deep.
It's really not more nuanced because if you dont take that responsibility you die.
 

RamRise

Well-Known Member
Sure I mean obviously CFIT is not nuanced.

The PIC is responsible to make sure lots of things are occuring as they are suppose to, but unless you're are omniscient, the fact of the matter is we rely upon a plethora of asistance, ATC included.

The PIC is responsible to prevent a midair collision...In IMC. Using TCAS RA. It should never get to that point. If someone doesn't do their job it might.

Sounds like ODPs and vector SID altitudes are "safer" than tower vectors because of TERPS vs eyeballing. Ever heard of TLAR?
Will you deny a radar vector from a field thats IFR with surrounding hills cause you'd rather play it safe and comply with the lost coms altitude, effectively what the Chattanooga 6 departure provides? Or will you assuming they've analyzed the vector and it meets your airplane/operating requirements.
 
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