When controllers are trained, they learn, somewhere, that they can assign altitudes other than published at certain times. From a pilot's perspective, this translates to what they might expect, or what not to be surprised by, when an assigned altitude doesn't match up with what's on a chart. I'm looking for that guidance, or regulations, preferably in an FAA publication.
7110.65. In my experience they put you where they need you. I don’t sweat it. If you’re given an altitude that conflicts with something published or that you’re uncomfortable with, simply ask for clarification and request something different if that’s what you want. Don’t blindly comply if you aren’t sure.
I was IFR out of Teterboro, heading back to home base in Michigan. ATC assigns 9,000. Controller hands me off to the next guy, who says, "What are you doing at that altitude? Either climb to 10 or descend to 8, your choice!" I told him I was just following the altitude that I was cleared to. Talk to the guy who handed me off. Geesh. Gotta love New York. (Yeah, I know... I lived there for six years.)
https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/mva_mia/mva/ https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/mva_mia/mia/
Ah. Being able to assign Altitudes below the MEA/MOCA/Segment Altitudes but at or above their MVA for Approach Controls or MIA for Centers. I’ll get back later with quotes from their rules. Remind me in a day or two if I don’t. EDIT: @Clip4 touched on it above
§ 91.177 Minimum altitudes for IFR operations. (a) Operation of aircraft at minimum altitudes. Except when necessary for takeoff or landing, or unless otherwise authorized by the FAA, no person may operate an aircraft under IFR below - (1) The applicable minimum altitudes prescribed in parts 95 and 97 of this chapter. However, if both a MEA and a MOCA are prescribed for a particular route or route segment, a person may operate an aircraft below the MEA down to, but not below, the MOCA, provided the applicable navigation signals are available. For aircraft using VOR for navigation, this applies only when the aircraft is within 22 nautical miles of that VOR (based on the reasonable estimate by the pilot operating the aircraft of that distance); or (2) If no applicable minimum altitude is prescribed in parts 95 and 97 of this chapter, then - (i) In the case of operations over an area designated as a mountainous area in part 95 of this chapter, an altitude of 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or (ii) In any other case, an altitude of 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown. (b) Climb. Climb to a higher minimum IFR altitude shall begin immediately after passing the point beyond which that minimum altitude applies, except that when ground obstructions intervene, the point beyond which that higher minimum altitude applies shall be crossed at or above the applicable MCA.
Sounds like this is what you are looking for. The minimum instrument altitude is a combination of the various charted altitudes we see and ATC's "minimum vectoring altitude" (MVA for terminal airspace) and "minimum instrument altitudes" (MIA for center airspace). The MVA and MIA are generally at ir below the charted ones - there's your variance. If that's what you are looking for, the place to start is here, the FAA's MVA/MIA page. You will probably need to do some searching on how to make sense of them. I did an article, Minimum Altitudes, discussing them last year. This one is not behind a paywall.
Here’s some Controller rules about it. Note a. 2. (a) 4−5−6. MINIMUM EN ROUTE ALTITUDES (MEA) Except as provided in subparagraphs a and b below, assign altitudes at or above the MEA for the route segment being flown. When a lower MEA for subsequent segments of the route is applicable, issue the lower MEA only after the aircraft is over or past the Fix/NAVAID beyond which the lower MEA applies unless a crossing restriction at or above the higher MEA is issued. a. An aircraft may be cleared below the MEA but not below the MOCA for the route segment being flown if the altitude assigned is at least 300 feet above the floor of controlled airspace and one of the following conditions are met: NOTE− Controllers must be aware that in the event of radio communications or GNSS failure, a pilot will climb to the MEA for the route segment being flown. 1. For aircraft using VOR, VORTAC or TACAN for navigation, this applies only within 22 miles of that NAVAID. 2. When radar procedures are used, the following actions are taken: (a) In the absence of a published MOCA, assign altitudes at or above the MVA or MIA along the route of flight, and (b) Lost communications instructions are issued. 3. The aircraft is GNSS equipped.
Excellent info guys - thanks. FWIW I took my IR written a few years ago, and just after finishing flight requirements, the plane I used for training went into the shop, then again, for about 5 months. Which led into the pandemic... Long story short, just getting back into it now. I have to take the written again, so along with studying. I'm trying to dig a little deeper. It's helpful to learn from the controllers' perspective, too. Thanks again.
WAFDOF wrong altitude for direction of flight. Sometimes atc needs for separation, sometimes the pilot has incorrectly chosen the wrong altitude.
I verified the altitude with the first controller, but apparently he didn't explain it to the next one.
My favorite ATC exchange was this one I did a while back: 27K: Navion 27K would like higher. Center: What altitude would you like? 27K: Something around seventy degrees. It's pretty hot down here. Center: Climb and Maintain 70 degrees. Let me know what altitude that ends up being.
There is no WAFDOF for IFR operations in controlled airspace. The correct altitude is whatever the controller assigns. 91.179a: In controlled airspace. Each person operating an aircraft under IFR in level cruising flight in controlled airspace shall maintain the altitude or flight level assigned that aircraft by ATC. However, if the ATC clearance assigns “VFR conditions on-top,” that person shall maintain an altitude or flight level as prescribed by § 91.159. Paragraph b, where it mentions the "odd and even thousands" only applies to uncontrolled airspace. Now, obviously there are ATC letters of agreement and such, but complying with those falls on the controller, not the pilot.
I have requested and received block altitudes, too, when I knew I was near the tops of the clouds but didn't necessarily want to climb two thousand feet.
yes there is! Unless you mean there is no longer the term "wafdof" (wrong altitude for direction of flight), now they insist on that silly pandering to the terminally snowflakey people; iafdof (inappropriate altitude for direction of flight) <insert eyeroll over that term here> I refuse to accept it and will always use my archaic terms. TRSA to you!
