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Not a controller, but last week I had to turn down 2 offers for direct because out enroute net ceiling was lower than the grid MORA. I use the ISA # and A/I factor that's on the release and go from there.
As far as terrain clearance and drift down go, as soon as you're "light" enough to drift down above the grid MORA for the conditions you can go off route.
The place I work also has generic TC/DD charts for certian areas of the country that can pretty much let you take any reroute as long as your an an airway.
I know this wasn't what you were looking for but I'm currious if you've seen stuff you couldn't take after looking at the MORA's and generic pink pages...
I did calculate the enroute net ceiling. It was lower than the grid MORA. There are no specific or generic sector charts for the area I was in. I was simply unable to accept a reroute and the controller was extremely unhappy about it.
Im under the impression that controllers don't understand or don't care about the limitations of our aircraft and are unable to comply with their instructions because of it. Im hoping this was an isolated incident (although its happened twice to me in a certain center's airspace) and that other controllers in other facilities do in fact know about these rare situations and how they deal with it. Because I don't appreciate being bullied or threatened and having to call every time it happens to explain the situation and following it up with ASAP/ASRS.
Where were you at? What did they want you to do?
just out of curiosity, the E145 (based on your profile) will not hold 17000 on one engine? (16800 MEA)
just out of curiosity, the E145 (based on your profile) will not hold 17000 on one engine? (16800 MEA)
Im under the impression that controllers don't understand
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".
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.![]()
unable to comply with their instructions because 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!
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.
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.
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.
The guy even told me that I'm required to accept his clearance because that is regulation and it supersedes my terrain clearance regulation
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?
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.
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.