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?

 

[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

 

[Deuce]

Y'all need traffic

 

[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.

 

[Deuce]

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

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

 

[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.

 

[jdatc]

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

This sounds like a center math problem.

But let’s use 3000’ and pretend they are right for direction.

Aircraft A has a ground speed of 420knots leaving Denver headed to JFK flying at FL330. Aircraft B has an airspeed of 360knots and has left JFK flying to Denver at an altitude of FL300. As aircraft A passes over aircraft B, you grant aircraft B’s request to climb to FL340.

At what climb rate would it set off the snitch, and they have less than 5 miles assuming an instantaneous climb at the very moment they passed each other.

13 mile a minute closure rate, means that they would be 5 miles apart (and thus separated) in ~23.07seconds. To lose separation would require the climbing aircraft to reach FL321 in 23 seconds per se.

So if they suddenly managed a 5500 foot per minute climb rate, you’d totally have a deal… maybe.

Now imagine if we add 3 seconds for us to transmit it to them, and 3 for them to read it back, executing it immediately upon completion of the read back. ~2100 feet in 17 seconds. Isn’t that a greater than 7500fpm climb?

i like maths!

 

[Dolan]

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.

That's cool. I'd write them up for not doing it because it's completely safe and there's other things that need to be done.

It's almost like there's almost as many opinions on this stuff as there are controllers...

 

[32andBelow]

This sounds like a center math problem.

But let’s use 3000’ and pretend they are right for direction.

Aircraft A has a ground speed of 420knots leaving Denver headed to JFK flying at FL330. Aircraft B has an airspeed of 360knots and has left JFK flying to Denver at an altitude of FL300. As aircraft A passes over aircraft B, you grant aircraft B’s request to climb to FL340.

At what climb rate would it set off the snitch, and they have less than 5 miles assuming an instantaneous climb at the very moment they passed each other.

13 mile a minute closure rate, means that they would be 5 miles apart (and thus separated) in ~23.07seconds. To lose separation would require the climbing aircraft to reach FL321 in 23 seconds per se.

So if they suddenly managed a 5500 foot per minute climb rate, you’d totally have a deal… maybe.

Now imagine if we add 3 seconds for us to transmit it to them, and 3 for them to read it back, executing it immediately upon completion of the read back. ~2100 feet in 17 seconds. Isn’t that a greater than 7500fpm climb?

i like maths!

If the trainee said all that they’d have more leg to stand on. They usually don’t even understand what they are doing they are just emulating something they saw someone else do.

 

[SunnyATC]

I’m going to think of this thread every time I see a center flow control program for congestion.

 

[DankVectorz]

A lot of trainers would write someone up for that

Bad ones

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

Like this

 

[Move78]

Bad ones

Like this

Tried to like this more than once