In controlled airspace. In uncontrolled airspace no ATC
service is available and neither is a clearance. But IFR is
possible using the big sky random principle.


§ 91.177 Minimum altitudes for IFR operations.
(a) Operation of aircraft at minimum altitudes. Except when
necessary for takeoff or landing, no person may operate an
aircraft under IFR below-

(1) The applicable minimum altitudes prescribed in parts 95
and 97 of this chapter; or

(2) If no applicable minimum altitude is prescribed in those
parts-

(i) In the case of operations over an area designated as a
mountainous area in part 95, 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.

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,
when within 22 nautical miles of the VOR concerned (based on
the pilot's reasonable estimate of that distance).

(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.



91.179 IFR cruising altitude or flight level.

(a) 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.

(b) In uncontrolled airspace. Except while in a holding
pattern of 2 minutes or less or while turning, each person
operating an aircraft under IFR in level cruising flight in
uncontrolled airspace shall maintain an appropriate altitude
as follows:

(1) When operating below 18,000 feet MSL and-

(i) On a magnetic course of zero degrees through 179
degrees, any odd thousand foot MSL altitude (such as 3,000,
5,000, or 7,000); or

(ii) On a magnetic course of 180 degrees through 359
degrees, any even thousand foot MSL altitude (such as 2,000,
4,000, or 6,000).

(2) When operating at or above 18,000 feet MSL but below
flight level 290, and-

(i) On a magnetic course of zero degrees through 179
degrees, any odd flight level (such as 190, 210, or 230); or

(ii) On a magnetic course of 180 degrees through 359
degrees, any even flight level (such as 180, 200, or 220).

(3) When operating at flight level 290 and above in non-RVSM
airspace, and-

(i) On a magnetic course of zero degrees through 179
degrees, any flight level, at 4,000-foot intervals,
beginning at and including flight level 290 (such as flight
level 290, 330, or 370); or

(ii) On a magnetic course of 180 degrees through 359
degrees, any flight level, at 4,000-foot intervals,
beginning at and including flight level 310 (such as flight
level 310, 350, or 390).

(4) When operating at flight level 290 and above in airspace
designated as Reduced Vertical Separation Minimum (RVSM)
airspace and-

(i) On a magnetic course of zero degrees through 179
degrees, any odd flight level, at 2,000-foot intervals
beginning at and including flight level 290 (such as flight
level 290, 310, 330, 350, 370, 390, 410); or

(ii) On a magnetic course of 180 degrees through 359
degrees, any even flight level, at 2000-foot intervals
beginning at and including flight level 300 (such as 300,
320, 340, 360, 380, 400).

"Doug" wrote in message
ps.com...
| Misposted a bit, radar coverage is not mandatory for IFR
flight but ATC
| clearance is and it USUALLY includes radar coverage.
|