714 

14 CFR Ch. I (1–1–24 Edition) 

§ 91.177 

(B) The lights or markings of the 

threshold; 

(C) The runway touchdown zone land-

ing surface; or 

(D) The lights or markings of the 

touchdown zone. 

(4) Compliance Date. Beginning on 

March 13, 2018, a person conducting an 
EFVS operation to 100 feet above the 
touchdown zone elevation must comply 
with the requirements of paragraph (b) 
of this section. 

(c) 

Public aircraft certification and 

training requirements. A public aircraft 
operator, other than the U.S. military, 
may conduct an EFVS operation under 
paragraph (a) or (b) of this section only 
if: 

(1) The aircraft meets all of the civil 

certification and airworthiness re-
quirements of paragraph (a)(1) or (b)(1) 
of this section, as applicable to the 
EFVS operation to be conducted; and 

(2) The pilot flightcrew member, or 

any other person who manipulates the 
controls of an aircraft during an EFVS 
operation, meets the training, recent 
flight experience and refresher training 
requirements of § 61.66 of this chapter 
applicable to EFVS operations. 

(d) 

Exception for Experimental Aircraft. 

The requirement to use an EFVS that 
meets the applicable airworthiness re-
quirements specified in paragraphs 
(a)(1)(i), (a)(2)(iii), (b)(1)(i), and 
(b)(2)(iii) of this section does not apply 
to operations conducted in an aircraft 
issued an experimental certificate 
under § 21.191 of this chapter for the 
purpose of research and development or 
showing compliance with regulations, 
provided the Administrator has deter-
mined that the operations can be con-
ducted safely in accordance with oper-
ating limitations issued for that pur-
pose. 

[Docket FAA–2013–0485, Amdt. 91–345, 81 FR 
90172, Dec. 13, 2016; 82 FR 2193, Jan. 9, 2017] 

§ 91.177

Minimum altitudes for IFR op-

erations. 

(a) 

Operation of aircraft at minimum al-

titudes.  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, pro-
vided 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 air-
craft 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 nau-
tical 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 nau-
tical 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 inter-
vene, the point beyond which that 
higher minimum altitude applies shall 
be crossed at or above the applicable 
MCA. 

[Doc. No. 18334, 54 FR 34294, Aug. 18, 1989, as 
amended by Amdt. 91–296, 72 FR 31678, June 
7, 2007; Amdt. 91–315, 75 FR 30690, June 2, 2010] 

§ 91.179

IFR cruising altitude or flight 

level. 

Unless otherwise authorized by ATC, 

the following rules apply— 

(a) 

In controlled airspace. Each person 

operating an aircraft under IFR in 
level cruising flight in controlled air-
space shall maintain the altitude or 
flight level assigned that aircraft by 
ATC. However, if the ATC clearance as-
signs ‘‘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: 

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Federal Aviation Administration, DOT 

§ 91.183 

(1) When operating below 18,000 feet 

MSL and— 

(i) On a magnetic course of zero de-

grees 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 de-

grees 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 de-

grees through 179 degrees, any odd 
flight level (such as 190, 210, or 230); or 

(ii) On a magnetic course of 180 de-

grees 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 de-

grees 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 de-

grees 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 Re-
duced Vertical Separation Minimum 
(RVSM) airspace and— 

(i) On a magnetic course of zero de-

grees through 179 degrees, any odd 
flight level, at 2,000-foot intervals be-
ginning 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 de-

grees through 359 degrees, any even 
flight level, at 2000-foot intervals be-
ginning at and including flight level 300 
(such as 300, 320, 340, 360, 380, 400). 

[Doc. No. 18334, 54 FR 34294, Aug. 18, 1989, as 
amended by Amdt. 91–276, 68 FR 61321, Oct. 
27, 2003; 68 FR 70133, Dec. 17, 2003; Amdt. 91– 
296, 72 FR 31679, June 7, 2007] 

§ 91.180

Operations within airspace 

designated as Reduced Vertical 
Separation Minimum airspace. 

(a) Except as provided in paragraph 

(b) of this section, no person may oper-
ate a civil aircraft in airspace des-
ignated as Reduced Vertical Separa-
tion Minimum (RVSM) airspace unless: 

(1) The operator and the operator’s 

aircraft comply with the minimum 
standards of appendix G of this part; 
and 

(2) The operator is authorized by the 

Administrator or the country of reg-
istry to conduct such operations. 

(b) The Administrator may authorize 

a deviation from the requirements of 
this section. 

[Amdt. 91–276, 68 FR 70133, Dec. 17, 2003] 

§ 91.181

Course to be flown. 

Unless otherwise authorized by ATC, 

no person may operate an aircraft 
within controlled airspace under IFR 
except as follows: 

(a) On an ATS route, along the cen-

terline of that airway. 

(b) On any other route, along the di-

rect course between the navigational 
aids or fixes defining that route. How-
ever, this section does not prohibit ma-
neuvering the aircraft to pass well 
clear of other air traffic or the maneu-
vering of the aircraft in VFR condi-
tions to clear the intended flight path 
both before and during climb or de-
scent. 

[Doc. No. 18334, 54 FR 34294, Aug. 18, 1989, as 
amended by Amdt. 91–296, 72 FR 31679, June 
7, 2007] 

§ 91.183

IFR communications. 

Unless otherwise authorized by ATC, 

the pilot in command of each aircraft 
operated under IFR in controlled air-
space must ensure that a continuous 
watch is maintained on the appropriate 
frequency and must report the fol-
lowing as soon as possible— 

(a) The time and altitude of passing 

each designated reporting point, or the 
reporting points specified by ATC, ex-
cept that while the aircraft is under 
radar control, only the passing of those 
reporting points specifically requested 
by ATC need be reported; 

(b) Any unforecast weather condi-

tions encountered; and 

(c) Any other information relating to 

the safety of flight. 

[Doc. No. 18334, 54 FR 34294, Aug. 18, 1989, as 
amended by Amdt. 91–296, 72 FR 31679, June 
7, 2007] 

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