Why do you need MSA in departure procedures (DP)?

[B747ERNG]

Hi all,

I was asked a question today regarding the departure procedure, the question was why do they give you MSA information in the departure procedures?

For example, if we look at YBBN Runways 01/19 WEST SID. The minimum required climb gradient is 3.3%. My understanding is that if you follow the SID and you make sure the aircraft is able to perform the min climb gradient, then obstacle clearance can be guaranteed. So why is it necessary for them to offer you the MSA info in the SID plate?

I'm very confused, could someone with more experience shed some light on my question?

cheers

[404 Titan]

What if you have a failure on departure which would result in you unable to maintain the required climb gradient? The MSA in this situation would be handy to know, no?

[muffman]

How high are you going to need climb in the event of an engine failure? Particularly in a procedural SID where yo may not be established on your track, the MSA is the only info you have about what is a safe height.

The 3.3% or whatever is required by the SID is only necessary until you reach the relevant minimum altitude (which, within 25nm, may be the MSA). After that, obstacle clearance is guaranteed anyway.

[ad-astra]

B747ERNG

Knowing your abilities to avoid terrain is one of the first things you learn.
Particularly handy in the likes of PNG etc.

From visual departures via the lowest terrain to SIDs to DME Departure procedures (yes they do exist) to MSA's to LSALT's on various outbound/inbound radials they all serve in giving you the situational awareness that you need to stay safe.

There are all sorts of reasons why you may discontinue a SID and no longer have its associated protection.

Weather, ATC, Navaid unserviceability, Aircraft unserviceability etc will all occur at the most inopportune time!

No less important in Australia.

[Metro man]

Lost COMMS comes to mind with a requirement to climb to MSA. On GPWS equipped aircraft a terrain warning requires an immediate climb to above MSA.

Basically above MSA you are safe, below that you had better be in compliance with procedures for flight below MSA or risk becoming another CFIT.

[compressor stall]

There is something beyond the magenta line.

Clearly you've never seen it, hopefully you never do. But if you need to explore life beyond the magenta line, for the sake of your 150 passengers know what's out here. Please.

[B747ERNG]

Many thanks to everyone for answering my question, very valuable information, thanks!:ok: