29:
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as operating the aircraft under visual flight rules (VFR), and is the most common mode of operation for small aircraft. However, it is safe to fly VFR only when these outside references can be clearly seen from a sufficient distance. When flying through or above clouds, or in fog, rain, dust or similar low-level weather conditions, these references can be obscured. Thus, cloud ceiling and flight visibility are the most important variables for safe operations during all phases of flight. The minimum weather conditions for ceiling and visibility for VFR flights are defined in FAR Part 91.155, and vary depending on the type of
153:) above the contiguous 48 United States and overlying the waters within 12 miles thereof. Flight in Class A airspace requires pilots and aircraft to be instrument equipped and rated and to be operating under instrument flight rules (IFR). In many countries commercial airliners and their pilots must operate under IFR as the majority of flights enter Class A airspace. Procedures and training are significantly more complex compared to VFR instruction, as a pilot must demonstrate competency in conducting an entire
174:
254:, or through aircraft position reports in areas where radar coverage is not available. Aircraft position reports are sent as voice radio transmissions. In the United States, a flight operating under IFR is required to provide position reports unless ATC advises a pilot that the plane is in radar contact. The pilot must resume position reports after ATC advises that radar contact has been lost, or that radar services are terminated.
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many countries is "Special VFR" flight, where an aircraft is explicitly granted permission to operate VFR within the controlled airspace of an airport in conditions technically less than VMC; the pilot asserts they have the necessary visibility to fly despite the weather, must stay in contact with ATC, and cannot leave controlled airspace while still below VMC minimums.
149:(IMC), which is essentially any weather condition less than VMC but in which aircraft can still operate safely. Use of instrument flight rules is also required when flying in "Class A" airspace regardless of weather conditions. Class A airspace extends from 18,000 feet above mean sea level to flight level 600 (60,000 feet
340:
crashes. VFR flight into IMC is distinct from "VFR-on-top", an IFR procedure in which the aircraft operates in VMC using a hybrid of VFR and IFR rules, and "VFR over the top", a VFR procedure in which the aircraft takes off and lands in VMC but flies above an intervening area of IMC. Also possible in
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It is essential to differentiate between flight plan type (VFR or IFR) and weather conditions (VMC or IMC). While current and forecast weather may be a factor in deciding which type of flight plan to file, weather conditions themselves do not affect one's filed flight plan. For example, an IFR flight
106:
It is possible and fairly straightforward, in relatively clear weather conditions, to fly an aircraft solely by reference to outside visual cues, such as the horizon to maintain orientation, nearby buildings and terrain features for navigation, and other aircraft to maintain separation. This is known
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for aircraft landing on the same runway surface, but from opposite directions. Aircraft approaching from the north must make visual contact with the airport at a higher altitude than when approaching from the south because of rapidly rising terrain south of the airport. This higher altitude allows a
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In the UK, an IR (UK restricted) - formerly the "IMC rating" - which permits flight under IFR in airspace classes B to G in instrument meteorological conditions, a non-instrument-rated pilot can also elect to fly under IFR in visual meteorological conditions outside controlled airspace. Compared to
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system. Air traffic control may assist in navigation by assigning pilots specific headings ("radar vectors"). The majority of IFR navigation is given by ground- and satellite-based systems, while radar vectors are usually reserved by ATC for sequencing aircraft for a busy approach or transitioning
344:
During flight under IFR, there are no visibility requirements, so flying through clouds (or other conditions where there is zero visibility outside the aircraft) is legal and safe. However, there are still minimum weather conditions that must be present in order for the aircraft to take off or to
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It is important not to confuse IFR with IMC. A significant amount of IFR flying is conducted in visual meteorological conditions (VMC). Anytime a flight is operating in VMC and in a volume of airspace in which VFR traffic can operate, the crew is responsible for seeing and avoiding VFR traffic;
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In uncontrolled airspace, ATC clearances are unavailable. In some states a form of separation is provided to certain aircraft in uncontrolled airspace as far as is practical (often known under ICAO as an advisory service in class G airspace), but separation is not mandated nor widely provided.
135:
Visual flight rules are generally simpler than instrument flight rules, and require significantly less training and practice. VFR provides a great degree of freedom, allowing pilots to go where they want, when they want, and allows them a much wider latitude in determining how they get there.
483:. Flight under IFR beyond six months after meeting these requirements is not permitted; however, currency may be reestablished within the next six months by completing the requirements above. Beyond the twelfth month, examination ("instrument proficiency check") by an instructor is required.
408:
Specific procedures allow IFR aircraft to transition safely through every stage of flight. These procedures specify how an IFR pilot should respond, even in the event of a complete radio failure, and loss of communications with ATC, including the expected aircraft course and altitude.
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routing, where only the destination, or a few navigational waypoints are used to describe the route that the flight will follow. ATC will assign altitudes in its initial clearance or amendments thereto, and navigational charts indicate minimum safe altitudes for airways.
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land; these vary according to the kind of operation, the type of navigation aids available, the location and height of terrain and obstructions in the vicinity of the airport, equipment on the aircraft, and the qualifications of the crew. For example,
412:
Departures are described in an IFR clearance issued by ATC prior to takeoff. The departure clearance may contain an assigned heading, one or more waypoints, and an initial altitude to fly. The clearance can also specify a departure procedure (DP) or
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use cockpit instruments as secondary aids to navigation and orientation, but are not required to; the view outside of the aircraft is the primary source for keeping the aircraft straight and level (orientation), flying to the intended destination
331:
Although dangerous and illegal, a certain amount of VFR flying is conducted in IMC. A scenario is a VFR pilot taking off in VMC conditions, but encountering deteriorating visibility while en route. Continued VFR flight into IMC can lead to
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however, because the flight is conducted under instrument flight rules, ATC still provides separation services from other IFR traffic, and can in many cases also advise the crew of the location of VFR traffic near the flight path.
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is required so that the pilot practicing instrument approaches can wear a view-limiting device which restricts his field of view to the instrument panel. A safety pilot's primary duty is to observe and avoid other traffic.
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defines IFR as: "Rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the
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The aircraft must be equipped and type-certified for instrument flight, and the related navigational equipment must have been inspected or tested within a specific period of time prior to the instrument flight.
265:, which is the farthest the aircraft can fly without a new clearance. In addition, a clearance typically provides a heading or route to follow, altitude, and communication parameters, such as frequencies and
301:(VMC) en route does not automatically change to a VFR flight, and the flight must still follow all IFR procedures regardless of weather conditions. In the US, weather conditions are forecast broadly as VFR,
144:
When operation of an aircraft under VFR is not safe, because the visual cues outside the aircraft are obscured by weather, instrument flight rules must be used instead. IFR permits an aircraft to operate in
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of flight visibility and a distance from clouds of 500 feet below, 1,000 feet above, and 2,000 feet horizontally. Flight conditions reported as equal to or greater than these VFR minimums are referred to as
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872:
563:. From 1999 single-engine helicopters could not be FAA-certified for IFR. Recently, however, Bell and Leonardo have certified the single engine helicopters for instrument flight rules.
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Instrument pilots must carefully evaluate weather, create a detailed flight plan based around specific instrument departure, en route, and arrival procedures, and dispatch the flight.
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Any aircraft operating under VFR must have the required equipment on board, as described in FAR Part 91.205 (which includes some instruments necessary for IFR flight). VFR pilots
471:(meet recency of experience requirements). In the United States, to file and fly under IFR, a pilot must be instrument-rated and, within the preceding six months, have flown six
503:
the rest of the world, the UK's flight crew licensing regime is somewhat unusual in its licensing for meteorological conditions and airspace, rather than flight rules.
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flight crew to clear the obstacle if a landing is aborted. In general, each specific instrument approach specifies the minimum weather conditions to permit landing.
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in which the aircraft is operating, and on whether the flight is conducted during daytime or nighttime. However, typical daytime VFR minimums for most airspace is 3
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Because IFR flights often take place without visual reference to the ground, a means of navigation other than looking outside the window is required. A number of
876:
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Despite the protection offered by flight in controlled airspace under IFR, the ultimate responsibility for the safety of the aircraft rests with the
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361:(TAWS), these are primarily backup systems providing a last layer of defense if a sequence of errors or omissions causes a dangerous situation.
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commences. An instrument approach terminates either by the pilot acquiring sufficient visual reference to proceed to the runway, or with a
704:
Keel, Byron; Stancil, Charles; Eckert, Clifford; Brown, Susan (June 2000). "Aviation
Weather Information Requirements Recommendations".
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In the United States, instruments required for IFR flight in addition to those that are required for VFR flight are:
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238:. The most important concept of IFR flying is that separation is maintained regardless of weather conditions. In
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320:(VMC). To operate safely in IMC ("actual instrument conditions"), a pilot controls the aircraft relying on
417:(SID) that should be followed unless "NO DP" is specified in the notes section of the filed flight plan.
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En route flight is described by IFR charts showing navigation aids, fixes, and standard routes called
316:(IMC). The weather is considered to be MVFR or IMC when it does not meet the minimum requirements for
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75:, and navigation is accomplished by reference to electronic signals." It is also a term used by
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693:, Oklahoma City, Oklahoma: Federal Aviation Administration, 11 February 2010, pp. PCG I−4
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426:. Aircraft with appropriate navigational equipment such as GPS, are also often cleared for a
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based on route, time, distance, speed, and altitude. ATC monitors IFR flights on
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The distance by which an aircraft avoids obstacles or other aircraft is termed
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672:, Oklahoma City, Oklahoma: Federal Aviation Administration, 2008, pp. G–9
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Although large airliners, and increasingly, smaller aircraft, carry their own
246:(ATC) separates IFR aircraft from obstacles and other aircraft using a flight
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was created from a revision of this article dated 9 December 2017
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708:. Hampton, Virginia: NASA Langley Research Center. pp. 40–41.
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ATC Communication, A complete pilot-to-ATC communication reference
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Federal
Aviation Regulations Title 14, Chapter I, Subchapter E,
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are available to pilots, including ground-based systems such as
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for "LOC RWY 16R", "ILS RWY 16R", and "ILS or LOC/DME RWY 34L".
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The main purpose of IFR is the safe operation of aircraft in
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51:) is one of two sets of regulations governing all aspects of
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for each part of the flight. A clearance always specifies a
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Practicing instrument approaches can be done either in the
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because the required visual reference is not seen in time.
349:(KRNO) in a mountainous region has significantly different
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of the pilot which is the cause of a significant number of
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an aircraft is flying, such as an IFR or VFR flight plan.
438:(STAR), describing common routes to fly to arrive at an
1095:
Hear audio of a US instrument rating checkride - Part 1
1017:
US Code of
Federal Regulations, 14 CFR 61.57(c) and (d)
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The approach portion of an IFR flight may begin with a
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750:"14 CFR 91.155 [ Basic VFR weather minimums ]"
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procedures and course interception and tracking with
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aircraft from takeoff to cruise, among other things.
779:"FAR Part 91 Sec. 91.205 effective as of 10/20/2009"
95:
16:
Civil aviation regulations for flight on instruments
947:
Aviation
Weather Center - METARs Help Page (4 of 5)
531:with a sweep-second pointer or digital equivalent,
132:, and avoiding obstacles and hazards (separation).
949:National Weather Center. Retrieved 29 January 2015
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257:IFR flights in controlled airspace require an ATC
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1001:
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706:Aviation Weather Information Requirements Study
309:), IFR, or LIFR (low instrument flight rules).
1100:"Blind Flying, January 1933, Popular Mechanics
996:
655:
1006:"Terrain Awareness and Warning Systems—TAWS"
1057:"Resurrecting single-engine helicopter IFR"
1048:
801:
799:
202:. Unsourced material may be challenged and
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139:
21:"IFR" redirects here. For other uses, see
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713:
222:Learn how and when to remove this message
1157:, and does not reflect subsequent edits.
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832:
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555:rate-of-turn indicator that is either a
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27:
838:
805:
463:To fly under IFR, a pilot must have an
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578:Acronyms and abbreviations in avionics
913:
806:Collins, Richard (11 November 2006).
1102:details on blind flying for that era
488:instrument meteorological conditions
359:terrain awareness and warning system
314:instrument meteorological conditions
200:adding citations to reliable sources
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157:solely by reference to instruments.
147:instrument meteorological conditions
90:
1055:Hirschberg, Mike (April–May 2015).
916:"IFR Flight Prep: A Whole New Game"
13:
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1008:. Skybrary. Retrieved 11 July 2014
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55:aircraft operations; the other is
14:
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1083:
841:"The Basics: VFR Flight Planning"
691:Instrument Flight Rules (defined)
684:"Aeronautical Information Manual"
670:Instrument Flight Rules (defined)
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96:Comparison to visual flight rules
32:IFR in between cloud layers in a
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492:visual meteorological conditions
347:Reno-Tahoe International Airport
318:visual meteorological conditions
299:visual meteorological conditions
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118:visual meteorological conditions
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914:Goyer, Robert (30 April 2010).
436:standard terminal arrival route
385:as well as the satellite-based
64:Federal Aviation Administration
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808:"Getting an Instrument Rating"
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1:
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415:standard instrument departure
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324:and ATC provides separation.
280:, who can refuse clearances.
839:Wallace, Lane (3 May 2010).
757:Federal Aviation Regulations
663:"Instrument Flying Handbook"
613:Distance measuring equipment
307:marginal visual flight rules
292:IFR flying with clouds below
7:
759:: 721–722. 11 February 2010
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543:for the route to be flown,
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10:
1213:
638:Transponder landing system
573:Index of aviation articles
397:
283:
99:
68:Instrument Flying Handbook
20:
643:VHF omnidirectional range
628:Instrument landing system
873:"FAR Part 71 Sec. 71.33"
494:– in the latter case, a
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164:Separation and clearance
83:to indicate the type of
561:turn and bank indicator
140:Instrument flight rules
45:instrument flight rules
1135:
1115:Listen to this article
633:Non-directional beacon
334:spatial disorientation
293:
36:
1134:
961:"Safety Pilot in IMC"
473:instrument approaches
351:instrument approaches
291:
31:
1187:Aviation meteorology
1166:More spoken articles
442:(IAF) from which an
440:initial approach fix
196:improve this section
155:cross-country flight
23:IFR (disambiguation)
971:on 5 September 2007
879:on 23 February 2017
525:barometric pressure
521:sensitive altimeter
444:instrument approach
400:Instrument approach
244:air traffic control
240:controlled airspace
102:Visual flight rules
57:visual flight rules
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618:Flight instruments
583:Aeronautical chart
533:attitude indicator
322:flight instruments
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1061:Vertical Magazine
517:heading indicator
465:instrument rating
371:navigational aids
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151:pressure altitude
91:Basic information
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1067:on 19 April 2015
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1182:Aviation law
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1069:. Retrieved
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1038:. Retrieved
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973:. Retrieved
969:the original
965:IFR magazine
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881:. Retrieved
877:the original
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855:. Retrieved
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786:. Retrieved
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761:. Retrieved
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608:Bárány chair
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130:(navigation)
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1090:FAA website
932:27 November
857:27 November
824:27 November
783:rgl.faa.gov
763:27 November
732:|work=
623:Helmet fire
267:transponder
85:flight plan
81:controllers
73:flight deck
1176:Categories
1162:Audio help
1153:2017-12-09
649:References
553:gyroscopic
545:alternator
394:Procedures
365:Navigation
236:separation
34:Cessna 172
989:See KRNO
883:24 August
734:ignored (
724:cite book
710:CiteSeerX
603:Autopilot
549:generator
428:direct-to
259:clearance
248:clearance
183:does not
66:'s (FAA)
62:The U.S.
1192:Avionics
1164: ·
1071:11 April
1040:31 March
820:(11): 68
788:31 March
598:Autoland
567:See also
541:avionics
507:Aircraft
387:GPS/GNSS
109:airspace
41:aviation
1151: (
1122:minutes
1035:gpo.gov
928:(4): 56
853:(4): 61
559:or the
481:navaids
477:holding
469:current
423:airways
284:Weather
269:codes.
204:removed
189:sources
120:(VMC).
59:(VFR).
975:20 May
921:Flying
903:§71.33
899:§71.31
846:Flying
813:Flying
712:
537:radios
490:or in
77:pilots
1031:(PDF)
753:(PDF)
687:(PDF)
666:(PDF)
529:clock
459:Pilot
252:radar
1073:2015
1042:2018
977:2009
934:2010
885:2015
859:2010
826:2010
790:2018
765:2010
736:help
402:and
383:NDBs
381:and
379:VORs
303:MVFR
187:any
185:cite
79:and
926:137
851:137
818:133
547:or
375:DME
198:by
125:may
49:IFR
39:In
1178::
1120:20
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