Drift Down Routes

[ERJFO]

You're exactly correct. Say MORA, enroute net ceiling, or drift-down to 99% of US controllers and they won't have even a glimmer of an idea what you're talking about.

In 23 years, I've never received any training from FAA on any of these topics.

That's why I just say "we can't take that right now for terrain".

 

[Nevets]

That's why I just say "we can't take that right now for terrain".

Yeah, that's what I said, among other things. I also suggested that I could climb or descend but the controller was having none of it. He even threatened me with a pilot deviation if I didn't accept his clearance! Another controller asked me if I was declaring an emergency and asked me to squawk 7700! Oh well, I guess I will have to try to educate them one at a time.

 

[Coool Hand Luke]

Yeah, that's what I said, among other things. I also suggested that I could climb or descend but the controller was having none of it. He even threatened me with a pilot deviation if I didn't accept his clearance! Another controller asked me if I was declaring an emergency and asked me to squawk 7700! Oh well, I guess I will have to try to educate them one at a time.

Nevets, nice job on standing your ground despite the strong arm tactics.

 

[Cardinal]

unable to comply with their instructions because of it.

I disagree.

Half our routes were driftdown critical in the B1900 over the Rockies, so this was an unending source for checkride angst, FAA consultation, and continual study. But our philosophy as passed down by our FSDO and POI was quite clear: Traffic and Weather were valid reasons for deviating off a driftdown route. If a controller wanted you to do something else you just did it. If the instruction was just a generous direct-down-the-line, we'd come back with a "we need to stay on the route today" and all parties were satisfied.

He even threatened me with a pilot deviation if I didn't accept his clearance! Another controller asked me if I was declaring an emergency and asked me to squawk 7700!

Yikes. You probably should have. Which outcome would you prefer, the certainty of center-punching a thunderstorm / another aircraft or stay away from the high mountains where there is an extremely remote (1/eleventy billionth) chance of an engine failure and marginal terrain clearance?

What if you had two aircraft nose to nose, same altitude, both on driftdown routes. Better to just have a midair, quoting 121.191 on the way down? The example is extreme, but makes the point. When a conflict, however minor arrises, driftdown should be the first constraint thrown out the window.

 

[Nevets]

I disagree.

Half our routes were driftdown critical in the B1900 over the Rockies, so this was an unending source for checkride angst, FAA consultation, and continual study. But our philosophy as passed down by our FSDO and POI was quite clear: Traffic and Weather were valid reasons for deviating off a driftdown route. If a controller wanted you to do something else you just did it. If the instruction was just a generous direct-down-the-line, we'd come back with a "we need to stay on the route today" and all parties were satisfied.

Unfortunately for me, our FOM does not provide as much discretion. We are able to deviate from the route as long as its within 5 miles either side of the route.

Yikes. You probably should have. Which outcome would you prefer, the certainty of center-punching a thunderstorm / another aircraft or stay away from the high mountains where there is an extremely remote (1/eleventy billionth) chance of an engine failure and marginal terrain clearance?

What if you had two aircraft nose to nose, same altitude, both on driftdown routes. Better to just have a midair, quoting 121.191 on the way down? The example is extreme, but makes the point. When a conflict, however minor arrises, driftdown should be the first constraint thrown out the window.

It was not a situation in which our FOM requires us to declare an emergency and I didn't feel like it was either. So I declined. They asked me to squawk 7700 and that is fine with me if they wanted to declare the emergency. As long as I was able to stay on the route. In this particular instance, it was not weather related (I would do a 180 before punching through a thunderstorm). It was due to flow. I offered to slow down for them, but that wasn't good enough either. As for the traffic scenario, I offered to climb or descend. I think they just didn't like that I was not going to accept their clearance. The guy even told me that I'm required to accept his clearance because that is regulation and it supersedes my terrain clearance regulation. Needless to say, I very respectfully on the frequency disagreed with him.

Without it being an emergency, I'm not going to knowingly throw out any regulation out the window.

 

[Cardinal]

Unfortunately for me, our FOM does not provide as much discretion. We are able to deviate from the route as long as its within 5 miles either side of the route.

I just looked at my old one, and it says the same things, specifically allows for deviations in an emergency. However the operating philosophy described above was how we taught the matter, and how we demonstrated it to the Feds I had on aircraft on a weekly basis. Would your POI be more impressed with reasonable judgement or getting into a pissing match with ATC on the frequency?

The guy even told me that I'm required to accept his clearance because that is regulation and it supersedes my terrain clearance regulation

He is probably right. I perused 7110.65 and 121.191 but can't offer evidence for the assertion.

Another thought experiment: Any driftdown plan, using .191(a)1 or .191(a)2 makes a number of assumptions, many are bunk. A key assumption is the climb profile. Your planning software - necessary to comply with (a)2 - in all likelihood uses a best angle, uninterrupted climb from the runway to your planned cruise level. That never happens, and we all know it. So the data we're working from is invalid and doesn't comply with 121.191 the second we're held at an intermediate level. Are you crosschecking ISA deviation in the climb? One more way your data is in error and compliance is in question from the beginning.

The reg is a good one, it ensures you have options should an engine fail at an innoportune time, Fate Is The Hunter style. But take the broad view, comply with the letter of the law to the extent possible, then consider the spirit and principles behind it. Although I imagine I'm wasting my breath.

Further, what are we actually going to do when the dreaded engine failure occurs? We had a leg from FMN-DEN, passed directly over ALS, which lies in an huge 80 mile wide valley, hemmed in on both sides by 14000' mountains. Most days the computer showed (a)2 compliance with no alternates, thus if an engine failure happened directly over ALS, one could make it over the intervening mountain range and stagger to DEN. So, given an engine failure on a VMC day over ALS, are we going to land at the near and suitable airport below us, or buzz the hikers for 170 miles to our "driftdown approved" destination? I know what I'd do.

Know the regs. Know that they are in conflict. Apply reasonableness.

 

[Cardinal]

Descent is another area where compliance is unlikely. Larks Arrival into DEN, turboprops get cleared down to 16,000, which is basically the MVA, and are held down there for 30 miles until buzzing a ridgeline with a little more than 2,000 clearance. The paperwork says continue to the destination, but if you had a worst case engine failure plus a little ice, then stayed on the approved route, you'd end up a splatter on the side of the mountain. Reality is not considered.

 

[Nevets]

I just looked at my old one, and it says the same things, specifically allows for deviations in an emergency. However the operating philosophy described above was how we taught the matter, and how we demonstrated it to the Feds I had on aircraft on a weekly basis. Would your POI be more impressed with reasonable judgement or getting into a pissing match with ATC on the frequency?

I don't want to impress anyone. I rather follow regulations and the company FOM.

He is probably right. I perused 7110.65 and 121.191 but can't offer evidence for the assertion.

Well, he cannot compel me to accept any clearance. He was not correct in that assertion.

Another thought experiment: Any driftdown plan, using .191(a)1 or .191(a)2 makes a number of assumptions, many are bunk. A key assumption is the climb profile. Your planning software - necessary to comply with (a)2 - in all likelihood uses a best angle, uninterrupted climb from the runway to your planned cruise level. That never happens, and we all know it. So the data we're working from is invalid and doesn't comply with 121.191 the second we're held at an intermediate level. Are you crosschecking ISA deviation in the climb? One more way your data is in error and compliance is in question from the beginning.

The reg is a good one, it ensures you have options should an engine fail at an innoportune time, Fate Is The Hunter style. But take the broad view, comply with the letter of the law to the extent possible, then consider the spirit and principles behind it. Although I imagine I'm wasting my breath.

Further, what are we actually going to do when the dreaded engine failure occurs? We had a leg from FMN-DEN, passed directly over ALS, which lies in an huge 80 mile wide valley, hemmed in on both sides by 14000' mountains. Most days the computer showed (a)2 compliance with no alternates, thus if an engine failure happened directly over ALS, one could make it over the intervening mountain range and stagger to DEN. So, given an engine failure on a VMC day over ALS, are we going to land at the near and suitable airport below us, or buzz the hikers for 170 miles to our "driftdown approved" destination? I know what I'd do.

Know the regs. Know that they are in conflict. Apply reasonableness.

First, this happened more than 500 NM after our departure airport. It had nothing to do with the climb profile. Which is also why crosschecking ISA deviation during the climb 500 NM ago doesn't apply. Plus, our FOM does not give discretion on using ISA deviations or anti-ice application other than what is on the release. After these situations, I believe my company is going to amend our FOM to give us more discretion to mitigate these situations in the future.

Second, if there is an engine failure, our release tells us what alternates to proceed to and what route to use to get there. We may have multiple alternates depending on where the engine failure occurs. It assures 2000 feet clearance to drift down to those alternates.

I think I know the regs and our FOM. I offered reasonable suggestions to the controller. He was not willing to apply reasonableness to the situation, IMHO.

 

[Nevets]

Descent is another area where compliance is unlikely. Larks Arrival into DEN, turboprops get cleared down to 16,000, which is basically the MVA, and are held down there for 30 miles until buzzing a ridgeline with a little more than 2,000 clearance. The paperwork says continue to the destination, but if you had a worst case engine failure plus a little ice, then stayed on the approved route, you'd end up a splatter on the side of the mountain. Reality is not considered.

Our drift down routes don't always start at the departure airport or end at the destination airport. They are usually between two or more points along our flight.

Look, I didn't post here to argue when to follow or not follow regulations or company procedures. Obviously, there is a time and place where you throw those things out. What I wanted to know is if controllers out west actually know about this or was this just a couple of isolated instances in a particular ATC facility. Controller input would be welcomed.

 

[gt1900]

Just curious.... What would you do if WX was covering the entire airway and ATC tried to vector you around it? Would you turn it down and fly through it because of driftdown? What if ATC had to send other A/C into your airspace because of WX and they needed to send you more than 5 miles off your route to clear them? Would you say no and send the other a/c into a thunderstorm?? Because ive seen tons of stuff like that happen out west. It sounds like your FOM is very vague and doesn't cover every situation, and thats not your fault. You don't know why ATC was trying to move you, but based off of how mad the controller got, I'm guessing there could have been something going on more important than your driftdown. But then again, maybe not. The controller could have just been a jerk.. My point is that we as pilots don't always know why ATC does the things they do. But I have several friends who are controllers and trust me, pilots may think they know everything, but we don't. Especially when it comes to ATC.. Who knows, maybe your company filed a route that conflicted with other traffic flow. Maybe ATC didn't catch it until you were already airborne..... Get it. Sometimes its better to just move.