Descent below MVA

[ATC124]

Recently, an approach controller at my facility was told they were wrong by to descend an aircraft below the MVA although the aircraft would clearly never go below the MVA without reaching the next MVA sector (which was lower, obviously.) The controller argued the use of anticipated separation, familiarity with aircraft characteristics/rate of descent, and the use of “best judgment”(as defined in 1-1-1).

Thoughts?

 

[BravoLima6]

100% legal. And whether it’s positive control or not will depend on the details

 

[kombucha23]

I saw this come up once at a facility. Controller assigned an altitude below the MVA anticipating it, from 130 to 90 MVAs. QA/QC called it a loss for assigning the next altitude before they crossed into that MVA.

I’m also pretty sure anticipating separation is applicable only to same runway sep.

 

[32andBelow]

This conversation reminds me of a trainer I once had that wrote me a box 1 for climbing an aircraft that was 4k below a crossing aircraft as the targets merged. Told me I has no positive separation... like the aircraft was going to magically climb multiple thousands of feet in the 1 second before we had divergence.

A lot of trainers would write someone up for that

 

[PooseMaGoose]

Y'all need traffic

Our bad. I guess we all forgot 10s, 11s, and 12s shall not discuss interpretations or separation rules. Thanks for setting us straight.

 

[r9s]

Go 4 it. Anticipate that shit. Just gotta watch them more tho.SWA nope. AAL 737, all day long.

AAL takes a long time to do anything...

 

[PooseMaGoose]

But this is wrong. We assume this kind of thing all the time. Swapping altitude with two planes pointed at one another 100 miles apart is an example. Turning a base toward a higher MVA without anything assuring the aircraft won't accelerate to 1000 miles an hour straight across final into terrain is another.

Airplanes are bound by the laws of physics and basing how you work around this inescapable fact is never an unwise way to work.

I don’t think you’re comprehending what I’m saying. Im not saying whether we do it all the time or not. I’m saying that issuing control instructions and ensuring separation with any level of “assumption” is unwise, albeit legal on its face.

Yes airplanes are bound by the laws of physics, but what I’m talking about isn’t about the laws of physics. It’s about assuming performance characteristics like “southwest always rolls right away” (reference the AUS near miss) or “I work this GA tail number all the time and they never climb quickly” etc etc.

The particular example I’m giving is that it’s unwise to do something like the following: aircraft is 15 miles from the boundary to entering a lower MVA. Controller issues a descent appropriate for the lower MVA the aircraft will enter in 15 miles but not appropriate for the MVA it is currently operating in. The controller did so based off an assumption that the aircraft will descend at a particular rate as to not bust the current MVA during that 15 mile flight path leading up to the lower MVA. Not wise. I’ve seen it work out. I’ve also seen it not work out plenty of times. It’s not a loss unless the aircraft actually proceeds below the MVA but it’s unnecessary.

So yes.. as to your point, we assume things all the time. That doesn’t mean we SHOULD. Chances are it will never come back to bite you. But if you are ever talking to the NTSB or God forbid sitting in a courtroom, it would be great if you didn’t have to use the phrase “I assumed” when providing testimony. That’s my point.

A lot of trainers would write someone up for that

Yes they would and I’m one of them. My trainee’s job is to prove to me that he or she recognizes the conflict and positively separates them. They can start doing whatever they please on their own ticket once they certify, but I’ll need verification that they aren’t just “lucking” their way into not getting steak-sauces

 

[Dolan]

I saw this come up once at a facility. Controller assigned an altitude below the MVA anticipating it, from 130 to 90 MVAs. QA/QC called it a loss for assigning the next altitude before they crossed into that MVA.

I’m also pretty sure anticipating separation is applicable only to same runway sep.

Similar one at mine but an a/c was over a 7000 ft MVA at 9000 and issued 7000. Problem is that on their heading 30 miles away was an 8000 ft MVA so yeah not positive sep.

 

[32andBelow]

The FAA is really into positive control rn. It’s not illegal but it’s not positive control

 

[PooseMaGoose]

Relax Mr cool guy steak sauce, you just said you'd a1 someone for climbing aircraft 1 who is directly underneath aircraft 2 by 4 thousand feet passing tail to tail, if that's true you're a fool and you legitimately do need to be set straight

People are taking such hardline stances here I mean what are we talking about? Is the guy 2 miles from the MVA boundary and 10k above the MVA? Obviously it's fine to descend him. Is he 100 miles from the MVA boundary 200 feet above the MVA? Obviously this is not okay. Many trainees have bad judgement and some trainers have a lower tolerance, but certainly there are some cases where it's totally safe to issue the descent prior to crossing the MVA boundary. If you're telling me that it's never okay to issue the descent prior to crossing the MVA boundary even if the guy is 1 mile away and 100 thousand feet above it, totally ridiculous

I never said I would A1 somebody for that. I said i would “write them up” because they didn’t show me that they saw it. Black and white rules in a grey world allow for various interpretations and applications. A trainee’s job is to err on the side of black and white as much as possible. They have the rest of their career to wander into the grey on their own ticket.

It’s not a hardline stance to say exactly what I’ve said this entire time: it’s not wise to lean on assumptions in air traffic.

I’m eager to be set straight though. Sounds kinky.

 

[Dolan]

30 miles away? Are they going to be turned before it? If yes, then it's perfectly fine! If we used this logic with everything we couldn't do our jobs.

Idk, if they lose radio comms they're going right into that 8000 MVA at 7000. You cool betting everyone in the plane's life on that?

Just saying, either they're both "positive control" or niether one is