VOR beacons operate at shorter ranges and are free from most of the errors that afflict NDBs.
They use line of sight frequencies in the VHF band.
Frequencies are between 108 MHz and 117.975 MHz.
Between 108 MHz and 112 MHz the band is shared with ILS so VOR frequencies are only allocated at even 100 KHz spacing
From 112 MHz to 117.975 MHz the band belongs to VOR alone and spacing is reduced to 50 KHz.
Thus 108.2 MHz and 113.35 MHz would be VOR frequencies and 108.1 MHz would not.
Q. Which of the following could be a VOR frequency?
a) 119.20 MHz
b) 111.80 MHz <-- This one
c) 108.3 MHz
d) 109.5 MHz
Within the VOR ILS shared frequency range, the allocated frequencies are as follows:
VOR = EVEN 100 kHz numerals
108.00. 108.05, 108.20. 108.25 to 111.80. 111.85
ILS = ODD 100 kHz numerals
108.10. 108.15, 108.30. 108.35 t0 111.90. 111.95
Types of VOR:
There are two types of VOR:
1) Conventional or Standard VOR.
2) Doppler VOR (modern type).
Standard VOR
The VOR ground station consists of a cylindrical cover containing a horizontal dipole which is spinning clockwise at a rate of 30 revolutions a second.
Slots in the cylinder combined with the rotating dipole produce a limacon shaped polar diagram which also rotates at 30 revolutions a second.
The ADF cardioid has a sharp null, but VOR limacon does not.
To a receiver listening to the signal the amplitude appears to go up and down 30 times a second as the limacon rotates.
i.e. the received signal is amplitude modulated (AM) at 30 Hz.
The exact phase of the AM signal differs depending on the bearing of the aircraft from the VOR.
To detect this phase difference, an omni-directional reference signal (also at 30 Hz) is also sent out by the transmitter.
In order that the two 30 Hz modulations can be distinguished the reference signal is frequency modulated (FM).
The signals are arranged so that the reference signal and the variphase signal are in phase to the magnetic north of the station.
Anywhere else will show a phase difference between 0° and 360°.
The receiving aircraft looks at the phase difference between the FM reference signal and the AM variphase signal and displays it as a radial, a QDR.
No phase difference means the receiver is on the 360° radial.
A phase difference of 150° means it is on the 150° radial.
If true bearings are desired the variation at the station must be used in the conversion.
This is because the radials are referenced to magnetic north at the station, rather than at the aircraft.
The Cone of Confusion
There is an area in the overhead of a VOR transmitter where it is not possible to obtain accurate bearing information.
A pilot flying towards the overhead would notice the deviation indicator become more sensitive and it would eventually move well off centre as the aircraft gets very close to the beacon.
The TO/FROM flag would reverse as the aircraft passed through the overhead and the deviation indicator would then move back towards the centre as it becomes less sensitive.
A crew navigating with an RMI would see the needle deviate then rotate through 180° as they pass through the overhead.
The signal strength in the overhead may also be low enough to make the OFF flag flicker.
The ICAO limits of the cone of confusion are up to 50° from the vertical
Identification
The VOR carries a three letter morse ident at seven words a minute repeating every ten seconds.
Sonic beacons have voice identifiers as well e.g. "This is Miami Omni Range .." followed by the morse.
Errors and Accuracy
The Designated Operational Coverage (DOC) of a VOR, the range, sector and altitude where freedom from interference is guaranteed, is given in the AIP.
This is valid both by day and by night (unlike NDBs).
Outside the DOC, interference from other stations is possible.
ICAO require bearing accuracy of ± 5° on 95% of occasions.
Because of its higher frequency and line of sight transmission VOR is free from sky wave interference and coastal refraction.
Any bending of the signal by the structure of the aeroplane would not affect the indicated bearing so quadrantal error does not exist with VORs.
Scalloping and Site Error
Reflections from terrain and man made obstructions can cause errors as two signals with different phase differences intefere.
This will cause the course deviation indicator on the VOR indicator to move rapidly from side to side - too fast for an aircraft to follow - and it will make the needle on an RMI wobble.
The effect is known as scalloping or, when reflections come from very near the beacon, site error.
Where scalloping is known to occur it is notified in the COM section of the AIP and on approach plates.
The unauthorised use of Passenger Electronic Devices can create a similar effect.
Scalloping should be differentiated from 'beam bends' which are also caused by reflections from buildings but which are more predictable slight curves within the system tolerances.
Atmospheric Ducting
Atmospheric ducting can lead to synchronous transmissions even within the DOC.
Ducting is unpredictable no allowance can be made for it.
It illustrates the need to check the station ident whenever a beacon is used.
Power and Range
The power output of the transmitter continues to affect the range.
An output of 200 watts achieves ranges of up to 200NM.
An output of 50 watts will only be good for short range transmissions.
The maximum theoretical range can be calculated using the formula:
Max theoretical range = 1.23 x square root of H1 + 1.23 x square root of H2 (H1 and H2 are heights of transmitter and receiver).
Equipment Errors
Within the ± 5° total bearing accuracy the aircraft equipment must be accurate to ± 3°.
VOR transmitter is monitored to make sure it puts out bearings accurate to ± 1°
If the monitor detects a greater bearing error the transmitter is shut down and a standby transmitter is brought on line.
A station will also be shut down if the signal strength drops by more than 15% or if the monitor fails.
During the transfer period the station ident ceases or is replaced by a continuous tone.
The ident is resumed when the standby transmitter is operating within limits.
Doppler VOR
Standard VORs were usually sited well away from all obstructions to minimise site error.
For beacons to be sited on airfields Doppler VOR transmitter was developed.
It has a much larger diameter aerial that, because of its size, suffered much less from site error.
The Doppler VOR transmitter is a ring of stationary dipoles about 45ft in diameter.
A VHF signal is switched continuously around the ring of aerials so that it appears to come towards the aircraft and then move away.
The relative movement of the origin of the signal produces a Doppler shift, a shift in frequency, that varies with bearing.
This means the variphase signal in this system is now FM.
If the variphase signal is FM the reference signal must be AM.
This would produce reverse sensing at the aircraft receiver.
So the Doppler VOR signal rotates anti-clockwise at 30 Hz rather than clockwise.
This reverses the signal once again so the phase relationship at the receiver remains the same and instrument displays are unaffected.
VOR Applications
VORs are used for en-route navigation, usually to define airway centrelines.
The overall required accuracy of the displayed information is ± 5°.
When European airways were first plotted out a lower accuracy of ± 7.5° was assumed.
To keep an aircraft within the confines of an airway 10NM, maximum distance between the beacons was calculated to be 80NM. As a consequence many European VORs are about 80NM apart.
A terminal VOR is a low power beacon used as part of an airfield approach. TVORs share the lower frequencies with ILS.
A broadcast VOR is usually a terminal aid with a voice broadcast giving out the airfield weather (ATIS) superimposed on the carrier wave.
A test VOR (VOT) is a very low power beacon sited at airfields.
It puts out a constant phase difference of zero in all directions.
This allows aircraft to test the accuracy of their equipment on the ground.
The VOR test function is selected with a course of 000° set.
The Course Deviation Indicator should centre with FROM indicated, the RMI should indicate 180° QDM.
The beacon ident for a test VOR is a series of dots.
Aircraft heading 160o (M)
Aircraft is on radial 240o from a VOR
Selected course on HSI is 250o
The HSI indications are deviation bar:
ahead of the aeroplane symbol with the FROM flag showing
ahead of the aeroplane symbol with the TO flag showing behind the aeroplane symbol with the FROM flag showing
behind the aeroplane symbol with the TO flag showing
On an HSI (Horizontal Situation Indicator) used in combination with a VOR receiver:
A pictorial presentation of aircraft deviation relative to VOR radials is provided
The lubber line will indicate the reciprocal value of the received radial
The lubber line will indicate the selected radial
There will be no Omni Bearing Selector knob, as this function is automatic on this type of indicator
When using a two dot HSI, a deviation of one dot from the computed track represents
a) 2°
b) 5°
c) 5 nm d) 2 nm
The phrase "computed track" suggests an RNAV system. On a 2 dot HSI, one dot = 2.5 nm (assuming enroute phase). I guess option (d) is the closest if my assumptions are correct. Incase of VOR navigation, on a 2 dot HSI, one dot = 5°
Decimetric waves correspond to the frequency range:
3000 to 30000 MHz 3000 to 30000 KHz 300
to 3000 MHz 300 to 3000 KHz
Decimeter: A metric unit of length, equal to one tenth of a
meter.
Decameter: A metric unit of length, equal to 10 meters.
According to ICAO Annex 10, in which frequency
band(s) does a locator normally transmit?
HF/VHF MF/HF HF LF/MF
A locator outer marker, or LOM, is a navigation aid used as
part of an instrument landing system (ILS) instrument approach. LOM is a
non-directional beacon (NDB) co-located with the outer marker beacon in the ILS
approach, so that aircraft can navigate directly to the location using the NDB
as well as be alerted when they fly over it by the beacon.
A low or medium frequency radio beacon transmits
nondirectional signals whereby the pilot of an aircraft properly equipped can
determine bearings and "home" on the station. These facilities
normally operate in a frequency band of 190 to 535 kilohertz (kHz), according
to ICAO Annex 10 the frequency range for NDBs is between 190 and 1750 kHz, and
transmit a continuous carrier with either 400 or 1020 hertz (Hz) modulation.
All radio beacons except the compass locators transmit a continuous
three-letter identification in code except during voice transmissions.
A marker beacon is a particular type of VHF radio beacon used
in aviation, usually in conjunction with an instrument landing system (ILS), to
give pilots a means to determine position along an established route to a
destination such as a runway. Markers operate at 75 MHz (VHF).
An aircraft travelling at 330 metres a second
transmits a signal at 10 GHz to a stationary receiver. If the aircraft is flying
directly towards the receiver and they are approximately at the same height the
received frequency will be:
Received frequecy = 10 GHz + 11,000 HZ = 10,000011000 Hz or
10.000011 GHz
Which of the following statements is correct in respect
of a RF signal:
the plane of polarisation is dictated by the oscillator unit
in the transmitter the
electrical component of the signal is parallel to the aerial the magnetic component of the signal is parallel to the aerial both the electrical and magnetic components are parallel to
the aerial
A half wave dipole aerial suitable for transmitting
an RF signal at 18 MHz should have an effective length of:
RF signal at 18 MHz has a wavelength = Speed of sound /
frequency
= 3 x 10^8 / 18 MHz
= 16.66 meters
Half wave dipole = 16.66 / 2 = 8.33 meters
Which of the following statements is true?
A broad bandwidth gives a narrow beam width A narrow bandwidth improves beam width A transmission's bandwidth is affected by the design of the
aerial Bandwidth
must be reduced in order to reduce noise
Diffraction of a RF signal is a displacement of its
propagation path due to:
reflection from the surface passing over or through mediums of different conductivity passing
over obstacles with dimensions close to the wavelength passing through ionised regions of the upper atmosphere
One major consideration that determines if radio waves are
blocked involves the concept of diffraction. This depends on the wavelength of
the radiation and the size of the obstacle in which it is attempting to
penetrate. Low frequencies have a easier time passing over large objects such
as hills, while higher frequencies work better with small obstacles such as
rooftops. This can be very useful in making a radio wave blocked using the
knife-edge diffraction method. If a wave does not have a line of sight over an
object, a sharp edge can be created, which causes the radio wave to be blocked
and redirected to where the broadcast should go.
Refraction of an electro-magnetic radiation is:
The
bending of its propagation path as it passes through or over areas of different
electrical conductivity The loss of power as it passes through or over areas of
different electrical conductivity Is bending resultant from reflection from objects Is loss of power through reflection from objects
With regards to radio waves, which statement is true?
They
are reflected by metallic objects with a size compatible to the wavelength The longer the wavelength the greater the surface attenuation They travel at 186,000 nm a second in a vacuum High frequencies need large aerials
You are at an altitude of 9,000 feet. At a range of
200 nm from a VHF communications transmitter, and you are receiving a good
signal.
You should expect this since the transmitter is at a height
of 2.000 feet You should have been receiving the signal from a range of 240
nm You are probably receiving a sky wave signal You
are probably receiving a duct propagation signal
To establish and maintain effective HF communications
the frequency used at a given range: "should be decreased at night"
sun down frequency down
Refer to figure.In the following diagram, the phase
difference between the two signals is: 180°
To determine phase difference find where your wave rises
through the neutral position and read the phase of the reference wave (solid
one in this fig) at that point.
Ground direction finding at aerodromes utilises what
frequencies?
"VHF at civil aerodromes and UHF at military aerodromes"
The distance a surface wave can travel is limited by surface
attenuation (which decreases at lower frequencies and over the sea). Surface
waves are around:
100 NM long in the HF band. 500 NM long in the MF band. 1000 NM long in the LF band. 4000+ NM long in the VLF bands.
Surface waves and space waves occur together and the
combination is called a ground wave
As the frequency of a transmitter is increased, the
range of the ground wave will:
Decrease Decrease only at night Increase only over the sea
A radio beacon has an operational range of 10 NM. By
what factor should the transmitter power be increased in order to achieve an
operational range of 20 NM?
Eight Six Four Two
If an NDB with a transmitter power of 25 KW which has
a range of 50 nm is adjusted to give a power output of 100 KW the new range of
the NDB will be approximately: "100 nm"
An RMI indicates aircraft heading. To convert the RMI
bearings of NDBs and VORs to true bearings the correct combination for the
application of magnetic variation is: NDB: aircraft
position, VOR: beacon position
The speed of a radio wave in nm/sec is:
300,000 161,842 163,842 186,000
A radio wave with a horizontal magnetic component
would be best received by a ___ aerial.
magnetic parabolic horizontal vertical
The question is about a horizontal magnetic component which
means the electrical component is vertical.
An aircraft is HOMING
to a radiobeaconwhilstmaintaining a relativebearing of zero. If the magnetic
heading decreases, the aircraft
is experiencing:
left drift right drift
a windfrom the west zero drift
Magnetic heading decreases
= Windfromleft = Drift towardsright
An
NDB transmits a signalpattern in the horizontalplanewhich is:
a beamrotating at 20 Hz bi-localcircular
a cardioidbalanced at 30
Hz omnidirectional
Using
an NDB it is possible to experiencewhich of the followingerrorsorlimitations?
Coastalrefraction, timingerror and nighteffect Nighteffect, stationinterference and latitudeerror Nighteffect, stationinterference and lack of a failurewarningsystem Coastalrefraction, timingerror and lack of a failurewarningsystem
Timingerror and latitudeerrorare the oddones.
Factorsliable to affectmost NDB/ADF systemperformance and reliabilityinclude:
Which of the following is likely to have the greatesteffect on ADF accuracy?
InterferencefromotherNDBs, particularlyduring the day Frequency drift at the groundstation InterferencefromotherNDBs, particularly at night Mutualinterferencebetweenaircraftaerials
Whichcombinationgives the greatestreduction in reliability of ADF:
Station interference; Staticinterference; Lane slip Mountaineffect; Station interference; site error Nighteffect; Staticinterference; Quadrantalerror Nigheffect; Quadrantalerror; Station interference
Which of the followingmaycauseinaccuracies
in ADF bearings?
staticinterference, heighteffect, lack of failurewarning stationinterference, mountaineffect, selectiveavailability coastalrefraction, slantrange, nighteffect lack of failurewarning, stationinterference, staticinterference
With a transmissionfrom an NDB aerial, the ___ componenttravels in the ___ plane and the signal is ___ polarised.
find the loop NULL position
stop looprotation hear the IDENT and mustalways be switched ON hear the IDENT of some
NDB stationsradiating a continuouswavesignal
The purpose of the BFO switch
on the ADF receiver is to make
the signalaudible
Whenreceiving an NDB signal on an ADF receiver the BFO
can be selected OFF for the:
tonesignal on N0NA1A identsignal on N0NA1A tonesignal on N0NA2A identsignal on
N0NA2A
The firstsymboldescribes the transmittedwaveform, the seconddescribes the modulation and
the thirddescribes
the type of informationcarried. EmissionClassification: http://www.theairlinepilots.com/forum/v ... .php?t=809
Whenconsidering the propagation of ADF transmissionsnighteffect is mostpronounced:
at dusk and dawn during the longwinternights
at ornear the coast whenflying at lowaltitude
Inorder to obtain
an ADF bearing the: "signalmust be receivedbyboth the sense and loopaerials"
An
ADF uses a sense aerial to:
"resolveambiguousbearings".
An
NDB signalcrossingfromland to sea
will ___ speed and bend ___
the normal.
decrease, towards increase, towards decrease, awayfrom increase, awayfrom
Errorscausedby
the effect of coastalrefraction on bearings at loweraltitudesaremaximumwhen
the NDB is:
inland and the bearingcrosses the coast at an acuteangle inland and the bearingcrosses the coast at rightangles
When ADF equipmentwhichincorporates a sense aerial and a loopaerial is tuned to a NDB and the loopaerial is rotatedsothat
a sharpnull is found the aerial is:
either at rightanglesor in linewith the incomingsignals in linewith the incomingsignals
at rightangles to the incomingsignals alignedwith the aircraftnose
misalignment of the loopaerial signalbendingcausedbyelectricalinterferencefromaircraftwing signalbendingby the aircraftmetallicsurfaces skywave/groundwavecontamination
Whichone of the followingdisturbances is mostlikely to cause the greatestinaccuracy in ADF bearings?
ICAO
allocatedfrequencyband for ADF receivers is 190
- 1750 kHz
The
D layer of the ionosphereaffects the accuracy of NDB bearings:
by day and night by day only bynightonly never
Sky wavesarerefractedfrom the ionosphere. Where the iondensitychangesradiowaves will be refracted. Most of the refractionoccurs about 125km up, at what is known as the E layer.
NightEffectwhichcausesloss of signal and fading, resulting in bearingerrorsfrom NDB transmissions, is due to:
skywavedistortion of the nullposition and is maximum at dawn and dusk staticactivityincreasing at nightparticularly in the lowerfrequencyband
The accuracy of ADF within
the DOC (designated OP coverage)
by day is: +/-5 deg
The
95% accuracy for ADF bearings of an NDB by
day is:
±2° ±7°
±10°
±3°
The
signal to noiseratio for an NDB is ___ allowing
a maximumerror of ___ on
95% of occasionsduring ___
InaccordancewithDoc 8168, a pilot flying an
NDB approachmustachieve a trackingaccuracywithin ___ of the publishedapproachtrack.
+/-10°
+/- 5°
+/- 2.5°
+/- 2°
An
aircraft heading 315oM shows
an NDB bearing 180o on the RMI. Anyquadrantalerroraffecting the accuracy of thisbearing is likely to be:
zero, as quadrantalerrorsare not found on the RMI at a maximum
at a minimum zero, as quadrantalerrorsaffectonly
the VOR
TherearetwoNDBs, one 20 NM inland, and the other 50 NM inlandfrom the coast. Assumingthat the errorcausedbycoastalrefraction is the same for bothpropagations, the extend of the error is a positionlineplottedby an aircraftthat is overwater
will be:
the samefrombothbeaconswhen
the aircraft is on a relativebearing of 180o and 360o greaterfrom the beaconthat is 20 NM inland
the samefrombothbeaconswhen
the aircraft is on a relativebearing of 090o and 270o greaterfrom the beaconthat is 50 NM inland
An
aircraft 10 nmfrom a north-southcoastlinetakestwothree-positionlinefixesfrom
an inland NDB. The aircraft'sindicatedposition is:
Nearer to the coastlinethanitsactualposition Furtherfrom the coastlinethanitsactualposition Correctbecause the coastalrefractionerrors will canceloutbecausetwofixes have beentaken Correct in azimuth but false in range
Speed of a surfacewave is affectedby the surfaceoverwhich it travels
(fasteroverwaterthanland).
Thischange of speedmeans the wave is refracted at lowaltitude as it passesover a coastline.
Refraction is alwaystowards the coast. An aircraftreceiving a refractedwavewouldgive a falseindication of the beacon'sposition. It will place the aircraftnearer to the coastthan it actually
is. Thiseffect is worse the furtherbackfrom the coast
the beacon is sited. It can
be avoidedby:
1) Takingbearings at rightangles to the coast.
2) Flying at a higheraltitudes.
3) Choosingbeaconscloser to the coast
A
longrange NDB is likely to transmit on ___ and be classified as ___ Select the answer
to completethisstatement.
Oldersystemsinterrupt the carrierwave (Keying) to send an unmodulated (but alsoinaudible) Morsecodeident
(classified as A1A). User will have alsoerraticindicationswhile the signal is interrupted in thistype of beacon. To make the unmodulatedparts of the signalaudible, ADF equipmentincorporates a BeatFrequencyOscillator (BF0). More modern systemsimprint the identonto the carrierwaveby 'keying'
an audible, AM signal, in
time with the MorseCodeident (classified
A2A).
The
BFO:
creates the audioident for an NDB
is used to make the identfrom an A2A NDB audible is used to make the identfrom an A1A NDB audible
is used to determine the signalstrength of an NDB
According to anotherquestion the answer is: "hear the IDENT of NDBsusing N0N A1A transmissions"
Whatactuallyhappens
in the ADF receiverwhen
the BFO position is selected?
The BFO circuit is activated,
and the receiveracceptsonly A1A modulatedsignals
The BFO circuitoscillates
at an increasedfrequency
in order to allowidentification of A2A NDBs
The BFO circuit is de-activated The BFO circuitimposes
a toneonto the carrierwave to make the NDB'sidentaudible
The
nominal maximumrange of an
NDB with a transmitterpower is 200 watts is:
50 to 60 nm
100 to 120 nm
150 to 170 nm
200 to 200 nm
Inanotherquestion it is mentioned 40 to 45
NM. Anywayamong the optionsitsalwayslessthan 100.
Withregard to the followingtypes of NDB whichstatements is correct?
Locators have 200 W power,
50 nmrange and are N0N A2A Locators have 15 W power,
10-25 nmrange and are N0N A2A Locators have 5000 W power,
50 nmrange and are N0N A2A Locators have 5000 W power,
50 nmrange and are N0N A1A
An
NDB aerial is (i) so as to ensure the range is (ii) byminimising (iii) due to (iv):
(i) horizontal; (ii) maximum;
(iii) diffraction; (iv) the groundwave (i) vertical; (ii) maximum;
(iii) attenuation; (iv) energylosses to the surface
(i) horizontal; (ii) maximum;
(iii) refraction; (iv) the D layer
(i) vertical; (ii) maximum;
(iii) attenuation; (iv) atmosphericrefraction
Whataccording to ICAO Annex 10 is the range of a locator?
50 - 100 NM
25 - 50 NM 10 - 25 NM
100 - 300 NM
Which of the following is correct regarding the range of an
NDB?
The range is limited to the
line of sight Aircraft height is not limiting
for the reception of signalsfrom the NDB
The range of an NDB will mostlikelyincrease at day time
compared to night time
The transmitterpower of
the NDB station has noaffect on the range
Whenusing ADF (i)BY
NIGHT, the accuracy is (ii)LESSthan(iii)BY DAY, because
the surfacewave is (iv)
CONTAMINATED BY SKY WAVES
Snow will NOT affect ADF.
An
NDB has a range of 50 nmwith a poweroutput
of 80 watts: The powerrequired to increase the range to 75 nm is:
120 watts
150 watts 180 watts
320 watts
If an NDB signal is received at a range of 1000 nm:
The signal is a surfacewave and is quiteusable
It will be a groundwave
and will be inaccurate
It is a spacewave and will
be inaccurate It is a skywave and is inaccurate
For
longrangeNDBs the mostcommontype is:
LF N0N A1A
LF N0N A2A
MF N0N A1A
MF N0N A2A
If an NDB has a publishedrange of 30 nm, itsaccuracy is: "onlyguaranteedby day to thatrange"
With navigation aids and the procedure design process, the various types of procedures that are available will be described in this article. Relatively little emphasis with be placed on conventional navigation aids as the aviation industry is rapidly shifting to a satellite based environment. For this reason, satellite based procedures will be described in detail.
RNAV Approaches are described by a series of waypoints, legs, speed and altitude constraints stored in the onboard navigation database. Safety is improved by providing pilots with better situational awareness than on conventional Non-Precision Approaches (NPA) thereby reducing the risk of controlled flight into terrain (CFIT). Better access can also be provided to runways that are not equipped with precision approach and landing systems. RNAV approaches have been made possible by the widespread availability of high performance RNAV systems on all types of aircraft and in particular by the use of GNSS.
Pilots are now benefiting from the proliferation of Area Navigation (RNAV) Global Positioning System (GPS) approaches and lower minimums provided by WAAS-enabled systems. As of July 2011, there were twice as many WAAS approaches as Instrument Landing Systems (ILS) approaches. Currently, there are over 3000 Localizer Performance without Vertical Guidance (LP) and Localizer Performance with Vertical Guidance (LPV) procedures.
Leveling off at the MDA can be problematic if there are distractions or turbulence. Keeping the airplane at the MDA until the runway is sighted is another issue. But the worst problem may be resisting the urge to descend when you spot the runway too far out. Flying a Continuous Descent Final Approach (CDFA) eliminates the MDA level off, puts the airplane in a position to land when the runway is sighted, and forces you to go around if the runway is not sighted before a normal visual descent point. It is easier to fly than a dive and drive approach.
Given: 
