Preceed direct XYZ

[silverfish]

If you are given a clearance from ATC to proceed direct to a fix that would take you off route, how do you know you are complying with the minimum altitudes required?

My initial guess is the grid MORA's that are on Low/High charts. However, does this mean that I have to get my chart out and look at them all the way to the next fix before I can comply with the direct routing. My other guess would be MVA's. But, I'm not really even sure what that is. I mean I read the definition of it in the Jepp intro, but still a little confused.

What am I missing here?

 

[CRJ puppy]

What am I missing here?

"Situational awareness".

 

[wmuflyguy]

If you are given a clearance from ATC to proceed direct to a fix that would take you off route, how do you know you are complying with the minimum altitudes required?

My initial guess is the grid MORA's that are on Low/High charts. However, does this mean that I have to get my chart out and look at them all the way to the next fix before I can comply with the direct routing. My other guess would be MVA's. But, I'm not really even sure what that is. I mean I read the definition of it in the Jepp intro, but still a little confused.

What am I missing here?

Pretty much, then get the chart out and make sure you can comply with the SE drift down terrain clearance.

They shouldn't be clearing you at an altitude that violates the minimum terrain clearance, but you need to check your aircraft's performance.

From the controllers hand book:
4-5-6 d. Where MEAs have not been established, clear an aircraft at or above the minimum altitude for IFR operations prescribed by 14 CFR Section 91.177.

http://www.faa.gov/air_traffic/publications/atpubs/atc/atc0405.html#atc0405.html.2

 

[labbats]

I doubt a controller would give you direct to a fix unless it was legal. That doesn't mean to put all of your trust in them, but if you are uncertain you could always ask them or pull out a chart.

Also, unless I'm mistaken anyone in the continental USA (not including Alaska) FL180 and above should be above any required drift down altitude.

 

[dojetdriver]

Also, unless I'm mistaken anyone in the continental USA (not including Alaska) FL180 and above should be above any required drift down altitude.

True, assuming your company springs for the drift down data, as opposed to the easier/cheaper terrain clearance data.

Some years ago, my company was in that boat. A controller cleared an aircraft direct to a fix, but the grid altitudes were ABOVE the TC limit. So the CA refused the clearance, and the controller threatened to violate him on the radio for not complying with an ATC clearance.

The CA ASAP'd it. The result? That ATC facility's controllers got training that not EVERY operator has DD data and may only have TC data, and to ask an aircraft if they can accept a direct route clearance.

 

[rtmcfi]

What am I missing here?

A couple of spelling lessons. I can't believe I was the first spelling/grammar Nazi.

 

[FORESTGUMP]

What am I missing here?

experience and common sense

 

[SEVEN]

Just cancel and go VFR with flight following.

 

[145BOSS]

If you're in a Boeing, there is not a direct in the Continental U.S. that will put you in an area where the Grid MORA is higher than the driftdown altitude.

When I was flying the EMB-145 and were filed on a route where Terrain Clearance was a consideration, we were not allowed to take direct routing from ATC, although everyone did.

 

[silverfish]

Thanks for the answers and sorry for the bad grammar. I have no clue how to correct it or delete this thread.

 

[paulsalem]

I doubt a controller would give you direct to a fix unless it was legal.

I agree with that flying in the US...in less developed foreign countries, it's another story.

 

[Flyprdu]

Minimum Vector Altitude > Minimum Obstacle Clearance Alt.

 

[paid4training]

Excuse my GA vocabulary, but what is drift down altitude or were can it be found? Thanks in advance and again excuse my GA ignorance, the lil' Cherokee doesn't get above 10k very often....

 

[wmuflyguy]

I know it is a Transport Canada site, but the definition is good

http://www.tc.gc.ca/eng/civilaviation/publications/tp11575-definitions-5515.htm