Circling to Land
A circle at night is hazardous,
combined with low visibility it is suicidal. Low level manoeuvring flight with
few visual cues is as dangerous as flying can get. The circle to land is the
second option to the straight in and if you have not
briefed the circle you should execute the missed as a safer option. A straight
in approach with high minimums or more than 30 degrees off the centre line is
going to require a circle because you won't be able to get down to the
runway on the straight in.
Your decision to circle requires
that you fly the altitude and distance from the runway according to your
aircraft category. Fly below 91 knots you are Category A; fly above 91 a bit and
you're Category B. The distance difference is 2/10ths of a mile from 1.3 to 1.5.
Maintaining the altitude
during the circle is critical and the pilot must know the power and trim
required to fly the bank angle at one altitude while keeping the runway in
sight. Left turns are best if you need to keep the circle tight due to reduced
Once you lose sight of the runway you are expected to turn toward the airport,
intercept the missed approach
and fly the missed as published. If your circle lines you up on the runway get
configured and slowed so as to
get down in the runway landing zone.
Avoiding the Circle-to-Land
The design of the approach determines the requirements
Less than 400' per mile from FAF to threshold
Within 30 degrees of centreline
Course must cross extended centreline
Descent rate is from FAF to MDA at threshold may exceed 400 fpm.
Exceeds 30 degrees of centreline but not necessarily.
Course must cross extended centreline
You are expected to fly straight
in and make descent if able. If unable, you must circle and keep runway in sight
during your circle. Do not descend below circling altitude until established on
final. Advise ATC of intentions.
On Circling to Land
Circling to land is a relatively dangerous manoeuvre. It contains the
worst elements of IFR flight. There is a minimum obstruction clearance, a
limited space in which to manoeuvre, an absence of visual reference, and trying
to keep the runway in sight while preparing to land. At night it is a quite a
bit more than dangerous. The required continuous turn in marginal conditions
that keeps the airport in sight is hazardous. Many approaches that are aligned
with the runway will have only circling minimums. You still may be able to land
straight-in. Set up the missed approach procedure before beginning to circle. A
circle to land requirement is a contact type of approach or otherwise a visual
manoeuvre done with reference to instruments.
Because of the hazards associated with circling, flying the airplane must not be
part of the problem. You must know the power settings and airspeeds that provide
some safety margins. Trim the aircraft for the lightest possible touch. Let go
when you look for the airport. Practice the flying about an isolated airport in
good VFR to hone the MDA skills required in MVFR or LVFR conditions as for
During training you should make
every circle to land approach with as close and short approach as you can handle
without exceeding a 30-degree bank and your short field approach speed. This
will give you a steep approach. If your circle puts you on a right downwind you
might opt (tell ATC) to make a left downwind circle for better visual to the
runway. Don't hesitate to take advantage of any wind to get down steeper and
shorter. You are required to keep an identifiable part of the airport in
distinct view except when concealed by a banked wing.
On an ILS approach you must have
a localizer approach with a circle to land option. Most other approaches circle
to land minimums published as well and straight-in. Circling minimums only are
allowed for all approaches with a letter designation such as VOR-A. No
straight-in minimums are published if the approach is more than 30 degrees; off
the runway or a normal descent cannot made from MDA altitude. However, you are
allowed to land straight in with the runway in sight and an ATC clearance.
Request a 360 if you need to get down. In any circling approach keep the runway
in sight and stay at MDA until clear of obstructions. If the VOR plate has a
runway number it means that the approach is within 30-degrees of the runway and
straight-in minimums will be published.
If you lose sight of the runway,
overfly the airport, turn to your missed approach heading, and climb. The
published missed approach is valid only when begun at the missed approach point
at the MDA or higher. You are not promised terrain clearance if you do not
follow the published procedure. No turns should be made until reaching the
published missed approach point. Any other time you are on your own. The
circling minimums presume a high degree of pilot proficiency and familiarity
with the airport.
You have planned both the
circling manoeuvre toward the airport and the missed procedure. You have
pre-decided, because of the ATIS information, the approach angle sets which side
to look for the airport. There are no required circling manoeuvres. With ATC
clearance you are free to manoeuvre to a landing as long as the runway is in
sight. Requirements of distance from airport centre (Category A 1.5 nm) and 300'
clearance above obstacles are figured into the circling minimums.
Each category has a different
minimum circling radii requirement that is stated in nautical miles for the
aircraft category. Conversion of this to statute miles equals the visibility in
statute miles as stated on the approach plate. The minimum obstacle clearance
within each approach category circling manoeuvring area is 300 feet. Height
Above Airport. (HAA) is 350 feet for Category A planes. VASI and PAPI equipped
runways allow descent when within 10 degrees of interception. Publish minimums
provide obstacle clearance only within the protected airspace.
ILS descent must not be below
circling minimums for circling to be allowed. If there is a circling approach
listed for the airport the circling altitude is the MDA. The MAP is based upon
the FAF for the procedure as shown on the chart. An ILS approach for runway 27,
circle to land runway 9 has its missed approach point at the designated missed
approach point based on DME or on time and is a NON-PRECISION approach.
Every circle-to-land approach is
a non-precision approach. The MDA of a circling approach gives an obstacle
clearance of 300' but this is usually still lower than the normal pattern
altitude. Check the charts to see if circling can only be in one direction. Only
losing sight of the field due to banking is allowed. Any other failure to see
the field requires that you start your climb to the missed-approach altitude,
then turn in the direction of the protected obstacle-clearance region and fly
the missed-approach heading. If you leave the MDA before intercepting the final
approach course the FAA will blame you if you run into anything.
One way to fly circling minimums is to fly the glideslope down to the published
circling minimums for the localizer and then proceed at MDA on the localizer by
timing or DME if authorized. Another way is to fly the LOC to the straight-in
minimums and landing straight in. If the published ILS approach is to be flown
as a non-precision it makes sense to use the glide slope down to circling
minimums. Basic rule is to fly the shortest path to base of downwind leg even if
requiring you to overfly the airport. When appropriate all turns should be to
Since a high descent rate
usually has circling minimums only, you must be proficient in getting down
quickly and in cleaning up during the missed. If you become visual with the
runway by knowing where to look for the runway and are using a created VDP a
straight-in is possible. Use no more than 30-degree banks in turns and do not
rise above MDA by more than 50 feet. Only normal manoeuvres are allowed during
descent from MDA. If at any point you lose visual contact with the airport and
runway you must execute the missed. Don’t depart from the electronic glide slope
until within one mile of the airport.
You could use a 90 left/270
right course reversal in a circle to land situation if conditions require. If
possible, the turns should be made in the direction that gives the pilot in
command the best view of the runway during the turns. Unless otherwise directed,
the AIM procedure, if you lose sight of the runway, requires you to execute a
climbing turn back to the landing runway and continue the turn to establish
yourself on the published missed approach course. You are required to miss the
circling approach when an identifiable part of the airport is not distinctly
visible. If ceilings permit fly higher than MDA. A single pilot forced into
right turns should not be circling.
The circling approach area is
determined by approach category ("A" for C-172 for example). It is a series of arcs 1.3
miles in radius using all the runway ends and sides at the airport. Its size is
the largest area possible made from these arcs. Category B is 1.5 miles.
Primary obstacle clearance is only 300'. If obstacles are in the way no
circling will be allowed. Obstacles of less than 400' may not be charted on the
plates!!!! Circling in a specific direction may not be allowed. Study the chart.
Occasionally it is necessary to remain at a higher than published altitude when
transitioning to the approach. Occasionally, even the minimums vary according to
the approach category. If the descent requires you to fly at a higher approach
speed you must use the minimums for the higher category. Likewise, you must fly
the missed approach published for the higher category. Obstacle clearance is
assured only when using higher minimums for the speed flown. Higher minimums
apply if an aircraft is flown at a higher category airspeed.
FAA figures a 400-fpm descent
rate for the full approach but when circling is required the 400 fpm applies
only to the MDA. A higher rate may be required below the MDA for the straight in
approach. Don’t force it. Let the tower know if you do not plan to make a
straight in. The PTS in Task E of the instrument approach procedures requires
that an applicant know all the elements of the circle-to-land procedure. In a 22
word sentence the PTS says that the pilot must check the wind. At an
uncontrolled airport this means to overfly the airport and check wind
indicators. Basic procedure are to fly to the specified minimum, only if in
visual conditions you circle to land on the designated runway into the wind. You
are not allowed to descend below minimum altitude, go below visibility criteria
or make other than a normal landing.
The circle is after ATC
authorization when a straight-in landing is not the preferred option. Even if
cleared for a straight-in you can circle only if you have not descended below
the circling minimum. You have obstacle clearance if you remain within the
radius of your approach category based only on your normal approach speed. The
only way the examiner can participate in the flight is by maintaining a traffic
watch. The missed approach instructions are based upon a straight in landing.
Since the circling approach will
be coming in from nearly the opposite direction the direction of the missed turn
will be reversed from the one published. The way you fly the circle is more apt
to cause an accident than the weather. Circles are hazardous because you are
low, slow, and turning. However, you are more likely to fly into the ground
while on the centreline. Don’t circle if there is another option like landing
downwind. Don’t circle with ice aboard. Don’t bust MDA. Use shallow banks. Never
change from your decision to make the missed. A good missed is preferable to a
bad circle. Regardless of the clearance, every missed approach begins with a
straight-ahead climb with sufficient time to configure before initiating any
Circle to Land
A circle to land in daylight is bad but circling to land at night is
worse. Because two different procedures are involved. During the day the circle
to land is actually a contact approach in which you must keep the runway in
sight while remaining clear of clouds. At night the circle requires that you
remain clear of clouds and below any ceiling. You do not have time to scan the
instruments if you are watching the runway. It is best that you keep your speed
up until lined up with the runway.
Once you lose the runway, turn
to the runway and go for the published missed. If you haven't briefed the missed
you are in considerable do-do. If you are not well prepared for the missed it is
best to avoid making the circling approach. Go missed before you reach the
airport by climbing to the MAP before making any turns. Do this because it does
not require the flying skills, the planning and situational awareness that must
be part of any circling approach or missed. Don't go near an icing situation
during a circle to land.
Circling Not Allowed
A circling approach cannot be made
if straight in descent has gone below circling minimums. Any circling must
(should) be to keep the airport and runway to be used in sight from the pilot's
side. There are no circling minimums for an ILS approach. Minimum descent
altitudes may be published for straight-in-landings, circles-to-land or both.
Don’t use a lower straight in minimum for a circle because the 250’ obstacle
clearance only applies to the centreline of the approach. Because of obstacles
the direction to circle may be restricted to higher minimums. Read the chart
While the preflight preparation
included a complete run-through of the missed procedure, a review is done
outside the FAF perhaps by noting the procedure written in crayon on the
windshield. The prepared student asks questions about radio settings,
identifiers, and any changes from ‘as planned’. Among the vitals of position
awareness are your equipment settings.
You already have the missed
checklist out. At the missed you must have pre-decided the sequence of events
that you will perform. In addition to the sequence you have pre-decided the
timing you will use. Talking is way down on the list. Get the power in, go to
the heading, set pitch attitude, and remove some flaps. Gear later, talking
A mandatory reporting point. The
IFR missed approach is more demanding that a VFR go around because it will occur
in IFR conditions. The first consideration in low IFR conditions is to relate
these to your personal minimums. If a missed approach is a possibility, it would
be best to hand fly the approach instead of using autopilot. Controllers may be
unfamiliar with where a Missed Approach procedure goes. The published missed
approach is often a non-radar procedure and not very efficient. The missed
approach course usually approximates the approach course. If you forget the
missed procedure, add full power and climb on runway heading.
We often become slaves to our
training and fly the total time to the missed approach. Rather, at our
personal minimums and Visual descent point we would execute the missed. Get
away from the ground and obstacles, climb on course and don't turn until the
published time runs out. Don't clean up the plane until everything is under
control. Since you have memorized the first part of the missed approach
procedure and radios are pre-set you don't need to refer to the plate. Don't do
anything in a turn during the climbing missed except control the turn.
Should you experience a full CDI
deflection at any time you can climb but you MUST not turn before reaching the
missed approach point. There is no guaranteed obstacle clearance protection
beyond the full deflection of the CDI until we reach the missed approach point.
An early turn may present obstacles that exceed your maximum climb rate.
You are likely to make the
mistake of not applying full power only once. Power comes first, then pitch,
positive rate, gear and flaps. Any change in the order is going to be exciting.
Every missed starts with a climb. If you happen to have dual navs set them both
to the approach. The other option, of using the second nav for intersections or
missed or for distance means that re-setting is required. This distraction may
(will) create problems. With flip-flop nav critical fixes become relatively
The ILS missed approach point is
a given when the glide slope meets the decision altitude. If you are inside the
marker don’t try to salvage a poor intercept. Some say not to time for a
localizer approach if it detracts from the ILS. Fly one approach at a time.
VDPs (Visual Descent Points) are
not charted when DME is available or when there is no local weather advisory.
The VDP gives a charted point from which to commence a normal landing approach
with the runway in view. Use of the VDP is discretionary. While there are
complex ways to use the DME to find the VDP for normal and possible landing
slope to the runway the easiest way that will work consists of: Take 10% the MDH,
subtract that number in seconds from the approach time. At that time, if you do
not have the required runway visual indicators commence your missed approach
climb and turn when the time runs out. This method flexes and works for both
altitude and airspeed differences.
For the straight-in
non-precision approaches nothing beats having a pre-planned visual descent
point. There are several ways of getting a self-made VDP. The easiest way is to
take the MDA (HAT or HAA) and drop the last digit. Use the remaining figures (2)
as seconds to be subtracted from the approach time. The 3-degree descent rate
usually desired can be obtained by multiplying your ground speed by five. At 100
knots a 500 fpm descent is close to a three-degree descent.
Missed approaches do not occur
often but the missed approach should be a part of your proficiency training
after you have the rating. Get to a safe altitude before you become upset with
the weather forecast, ATC or yourself. The unexpected missed is the most
difficult IFR procedure of all. It will be much harder if some instrument fails
at this time.
The missed approach has several
problem areas. Following an incorrect procedure can fly you into an obstacle at
worst and at best may not return you to the correct fix. An approach flown too
far due to failure to determine the actual ground speed creates a distraction
problem. Looking for the airport is the most usual accident causing distraction.
A mistake in your ground speed that makes you look for the airport after you
have already passed it can be a fatal distraction. Use the ATIS wind direction
and speed to predetermine the indicated airspeed you will use on the approach.
Preparation for the missed
begins with the weather. An ATIS can be up to an hour old. Except
for training purposes successful non-precision approaches in minimum conditions
will create dangerous habits and presumptions. Save yourself the aggravation and
proceed to a precision approach facility.
The stress level of a second
approach after the missed approach is much greater than for the first. If the
miss is because of procedure or technique, you could try again. If the miss is
because of weather, find an alternate. The temptation to go below your personal
minimums is greater on a second approach. The second approach has a
disproportionate number of fatal accidents.
AN ATC warning of course or
altitude DEVIATION is sufficient notice to begin THE MISSED. If you do not
continue to fly the course procedure until the time has run out you will not
have guaranteed terrain clearance. Do not turn until past the missed approach
point. A climb is allowed but no turns.
Some characteristics of an emergency exist in the missed approach.
According to the FARs, you must
have only three variables under control to avoid the missed.
First, you must be able to make a normal descent to a landing.
Second, you must have a visually identified runway, runway markings or lights
Third, you must have the minimum flight visibility required for the procedure.
Recognition of these requires
judgment that is best acquired by experience. This experience requires that you
plan in advance as to how you will perform to the specific conditions as they
exist. For the non-precision approach you must come up with a
visual-descent-point plan, know where to look for the visual runway clues, and
know references for visual distance. For the precision approach there is no need
for a visual-descent-point, it is best that at some point on the approach, say
inside the inner marker, that you slow up and configure for landing. Runway
behind you has no value.
While the DH of the ILS will
allow a normal landing if you have slowed up, the MDA of the non-precision
approach allows no such option. If you reach the MDA you will not be able to
make a normal landing. You must accept the necessity for the circle-to-land
procedure. You can decrease this necessity by getting to the MDA as soon as
possible to increase your visual reference margin. Flying a slower approach
speed is another way to avoid the circling approach. It helps to know the length
of any lighting array and runway you are using. These should be a part of any
Some minimum altitudes are published
on charts. The published minimums are designed for the competent pilot. If you
are less than proficient raise the minimums. Other minimums are only
published for controller use. It is possible to request a lower than published
altitude, if it exists it may be authorized. Such distinctions exist where
flight along VOR to VOR routes have published altitudes but a vector airport to
airport may allow a lower altitude via RNAV or radar vectors.
IFR airspace flows with the
terrain. Minimum IFR altitudes in feet MSL are based upon obstacle clearance.
Approaches are based upon descent angles, manoeuvring area, aircraft speeds,
etc. FAR 91 operations have no landing minimums but according to aircraft and
pilot capability the safety of FARs 121 and 135 should be followed.
You must plan any flight with
knowledge of the underlying terrain. A vector may take you uncomfortably close
to the terrain. ATC has been known to assign headings and altitudes that
precipitate CFIT (controlled flight into terrain) accidents. As the ultimate
responsible party you must keep aware of your terrain proximity and clearance.
Where am I, cross-check?
No delay of missed
1. Confirms briefing data
2. Calls altitudes
3. Calls missed
4. Calls runway
ATC expects you to hold right on assigned altitudes as per FAR 91.123
regarding clearance deviation. In terminal areas ATC has a 200 foot margin
before they get on your case. This allows for turbulence and altimeter errors.
Centre and terminal rules have longitudinal, lateral and vertical minimums that
vary somewhat if in radar or non-radar environment. Laterally in terminals it 3
nautical, in centres it 5 nautical with radar. Without radar it varies. Aircraft
given vertical separation above 10,000 get merging traffic calls regardless but
below 10,000 ATC is not required to give a call.
By asking for a visual climb,
descent or separation the pilot has agreed to maintain VFR and visual
separation. ATC likes this because it relieves them of responsibility.
FAR 91.129 Applies to aircraft
on an ILS approach. It says that pilots are expected to remain at or above the
glide slope as indicated by either the ILS or the VASI. No glide slope will
intersect with an obstacle. Getting closer than the DA on an approach almost any
fly-up indication could mean that there is an obstacle in your future. Maximum
risk is inside the DH which is 200’ above the touchdown zone not the terrain
below. Obstacle clearance may be as little as 120 feet. In a step-down approach
you have a margin of 250’ obstacle clearance.
Your best way to handle obstacle
clearance below MDA or DH is to use an existing or make a visual descent point,
either by time or by DME. At three-degree glidepath intercepts these at a visual
descent point. Most actual approaches do not reach minimums before breaking out.
Slant range visibility is more important on an approach than vertical
Minimum crossing altitude MCA
Minimum descent altitude MDA
Minimum enroute altitude MEA
Minimum holding altitude MHA
Minimum obstruction clearance altitude MOCA
Minimum reception altitude MRA
Minimum safe altitude MSA
Maximum Elevation Minimums
Terrain figures for chart purposes are rounded off the nearest 100 feet
and then 200 feet is added. The chart figures thus makes the elevation with a
safety factor of from 201 to 299 feet. For obstacles made by man the figures are
rounded up to the nearest 100 feet and then another 100 feet is added. The
safety margin is then from 101 feet to 199 feet. The pilot is well advised to
add some more.
Below Minimums Part 91 Operations
Under FAR Part 91 flight rules:
A 24 hour monitored ASOS at an airport will allow for alternate minimums
Any type of FAA approved weather forecast may be used to determine if minimums
are met under FAR 912.169(c), including Area Forecasts.
Ceiling not a factor
Visibility as determined from the aircraft is
key factor. This flight visibility can not be less than required
No descent below DH or MDA unless:
1) Position to make normal landing, and
2) Approach light system; threshold markings; runway end identifier lights;
VASI; touchdown zone, its markings; or its lights or runway, its markings, or
its lights are visible and identifiable, and
If 1) is missing a missed approach is initiated, or
If 2) not even one of the features is visible and identifiable a missed
approach is initiated.
The FAA investigates all IFR
landings made where below minimums visibility is reported. I suggest that you
have difficulty hearing any ATC request for your flight visibility after an
a precision approach (glide slope) 600' ceiling and 2 miles
Obstacle clearance for precision approach is 121’ trapezoidal area tapering to
Obstacle clearance on intermediate segment (procedure turn) is 500’
Obstacle clearance on feeder and transition routes is 1000’ + depending on
For a non-precision approach 800' and 2 mile visibility
Obstacle clearance is minimum of 250’ trapezoidal area with no greater
clearance in any one area over another.
Procedures with a FAF all have 250’; a VOR without FAF is 300’; NDB with FAF is
300’ and without is 350’.
Obstacle clearance on intermediate segment (procedure turn) is 500’.
Obstacle clearance on feeder and transition routs is 1000’ + depending on
FAR 91.l15 allows descent below DH or MDA to TDZE+100 with any part of the
approach light system in sight. To descend below TDZE+100 requires having the
terminating bars, siderow bars etc. in sight.
ATC separation minimums are 1000
vertical and three miles laterally and 2000' and five miles above 29,000.
Visual separation by the pilot applies only if an approves form of separation is
confirmed. The purpose of
making the pilot responsible is to reduce radio congestion and reduce burden on
controllers. Once a pilot
acknowledges visual contact the responsibility for separation is his until he
says he no longer has visual contact.
Personal IFR Minimums
Every pilot who has flown into
unexpectedly low IFR conditions has come away with an appreciation that it is
necessary for him to set personal limits for his IFR flying. Every IFR flight
has to be weighted with the pilot's evaluation of his skill and experience,
familiarity with the aircraft and instrumentation, local awareness of terrain
and obstacles, and the 'need' to fly.
A second pilot in front with you
is always a good idea. The unexpected on takeoff that prevents a return due to
below minimums weather, requires an immediate flight to the nearest safe haven.
The setting up of departure and arrival procedures can always use another pair
of hands and a mind as back up. Single pilot IFR is very lonely. Any departure
from a field that cannot be returned to is certainly challenging the Gods.
Parts 91.167 and 91.169 spell
out the minimums that must exist one hour before until one hour after your ETA
at original destination must have 2000' ceiling and three mile visibility.
Should conditions be lower you must have an alternate airport with precision
approach limits of 600' and two-mile visibility or a non-precision approach with
800' and two miles. IFR Fuel requirements apply. The safety of a specific flight
at any specific point of this flight is directly related to the selection of
options you have available.
Set radios for the IAP for the other
end of the runway. An even better might be a GPS or VOR approach to a crossing
runway. Part 91 can depart but other Parts cannot depart if conditions will not
allow a return to departure airport. If conditions are below landing minimums
but above takeoff minimums we must have an alternate airport that is within
one-hour flight time. Taking off in zero-zero Part 91 is legal but you must know
where you will go if something stops working. Takeoff minimums are not mandatory
on FAR 91 operations but the Part 91 pilot should be aware of the FAR 121,129
and 135 minimums. A chart may show takeoff minimums and still not have an IFR
departure (Not Part 91)
There are no accident figures that
preclude zero-zero takeoffs as being dangerous. The acceleration of the aircraft
can cause a somatogravic illusion that you are more nose up than it seems.
Pilots who habitually make zero-zero Part 91 departures tend to be confident of
their abilities and the maintenance of their aircraft.
The risk in a low-visibility
takeoff lies in loss of control. Control can be lost during ground acceleration
or in the transition from seeing the ground and entering MIC. You do not have
any prep-period for the instantaneous change. Acceleration is a vertigo producer
and the pilot must know that illusions will occur and gauges must be believed.
The next immediate risk is loss
of power. Even if you know the area, low-visibility blinds you and trusting to
blind luck is not a good choice. It is for these reasons that the airline
minimums of one mile visibility are good minimums for the Part 91 pilot, too.
Low visibility takeoffs and departures have as an inherent factor flight close
to the ground and unseen obstacles. The hazard of the takeoff is the abrupt
transition to a full IFR workload. Part 91 has no minimums for takeoff but as
with any other IFR takeoff it has four phases:
This is where you taxi into position, align with the centreline, check and set
compass to HI, hold brakes while you use power to give you rudder control before
brake release, and go to takeoff power.
You use rudder rather than brakes to control rolling heading. If you can set a
localizer frequency the CDI has a one dot range of 70 feet to each side. Keep
the CDI centred. Acceleration can fool the AI into a nose-high indication so be
Rotation speed should be slightly faster than usual and relatively positive and
smooth. Let the plane fly off and get on the gauges. Apply right rudder. Get at
least 100' before changing gear or flaps. Waiting longer is usually better.
(4) Initial climb.
Maintain two bars on the AI and confirm airspeed and VSI both of which may lag
due to static error.
FAA climbs and climbs to minimum
altitudes are predicated on crossing the departure threshold at 35'. You are
required to report to ATC anytime you are unable to climb 500 feet per minute.
An airport that meets the weather
forecast may not be legal if it has non-standard minimums. (Jepp on airport
diagram sheet). A NOS chart may show an A for an airport where Jepp
charts may not because Jepp does not chart for Category E aircraft.
Sidestep landings to parallel
runways have higher minimums than straight in approaches. Sidestep should be
done as soon as runway is in sight.
Obstacle Clearance Minimums
Obstacle free zone (OFZ)
May be used in specific region near airport.
From end of runway away from MAP you have 1/2 nautical mile obstacle clearance
area. This area extends in an ever widening angle to 13.5 NM. At 13.5 NM the
primary safe area extends 4 nm to each side of centre line and the secondary
safety area is an additional 2 nm to each side. MOCAs insure obstacle clearance
by 2000' lateral and 1000' vertical and navigational signal within 22 nautical
of Navaid. In some instances as over the hills of Vallejo and Hayward the
proximity of the terrain is much closer.
Every airport with an instrument approach procedure also have a departure
procedure if obstructions are present in the terminal area.
An IFR departure is available for safety when terminal area obstructions
cannot be seen or avoided.
Obstacle clearance is assured if the departure end of the runway is crossed
above 35’ and climbs to 400’ before turning.
At this point a climb of 200 fpm will clear obstacles up to the enroute
This and any published rate of climb will clear obstacles by 35’.
NOS charts have a T to advise of non-standard requirements.
90 knots per nautical mile gives a climb rate per minute of 300 where only 200
fpm may be required.
If 350 fpm is required you should climb at 525 fpm.
If terrain is above runway elevation the obstacle clearance may be a little as
120’ even though the DH is at 200’.
The further away from the runway the greater the obstacle clearance.
Laterally the protected airspace is 1000’ wide when 200’ from the threshold.
At ten miles the lateral dimension is five miles to each side of the
centreline with the outside mile tapered upward.
Your obstacle clearance may be as little as 70 feet.
VOR/DME with FAF, Straight-in
VOR/DME, radial or arc final 500 500
NDB on airport, no FAF, straight-in 350 350
NDB obstacle clearances become wider toward the runway. This accounts for the
higher minimum descent altitudes
NDB w/FAF, straight in 300 300
Localizer, LDA, SDF 250 250
GPS approaches usually become narrower toward the runway. Therefore, the MDAs
are lower. Cannot be used to track courses unless there is an overlay. It is
o.k. to fly the missed or a transition but not the approach.
300 Tapers to 0
1,000 500DF Approach 500
In the secondary area the
obstacle clearance tapers to zero at the outer edge. The greatest clearance is
on the centreline.
Approaches with 500’ minimums
will have higher obstacles. Check the circling area.
If you intend to land, you must
at some point descend below the MDA and DH. The closer you get to the runway the
less your obstacle clearance becomes. The non-precision minimum is 250’. The
visibility minimums of all approaches are determined by the slope to the runway.
It is possible to have an obstacle intrude into the glide path inside the DH if
visibility minimums are over one mile.
Minimum Vector Altitudes
Controllers are required to issue an
altitude to maintain that provides obstacle clearance until on a published
segment of the approach. MVAs are used by radar controllers depending on radar
quality and the distance from the antenna. Controllers often put in their
personal fudge factor to protect themselves.
Minimum En route Altitude (MEA)
The MEA provides at least 2000' of
clearance above enroute obstacles when the route is over mountainous terrain and
An MEA assures reception of VOR signals. VHF communications are usually but
not always possible.
MEA guarantees radio communication on airways. Communication is guaranteed at
FAF and at missed approach point.
There is no assurance of communications anywhere else during the approach.
Don’t accept as gospel the MEA altitude during very cold conditions.
Request or fly at least a thousand above MEA.
Minimum IFR Altitude
The MIA is on unpublished direct ATC
routes established by the facility. Any ATC clearance will give restriction to
keep pilot above MIA.
Minimum Safe Altitude
If there is no nav facility within
30 nm of the airport, there will be no MSA. MSA provides 1000' clearance above
the highest obstacle in a defined sector. Be sure to check plates to see
facility used to determine MSA distances.
Minimums Off Airways Altitude
(Jepp MORA /FAA OROCA
IFR pilots operating on an IFR flight
plan off a designated airway must ensure they operate at a safe altitude based
upon the requirement of FAR 91.177. Actual flight information can only be
determined by use of sectional plus any NOTAMed new obstacles.
The pilot is responsible when
operating off-airways on a direct routing for determining the minimum en route
altitude. In mountainous terrain the minimum IFR altitude for off-airway
operations is 2000' above the highest obstruction within 4 miles either side of
Minimum off route altitude. On Jepp shown at 6000' or lower gives obstacle
clearance of 1,000'. Above 7000' there is 2000' clearance. This is only obstacle
clearance no reception or navigation included. The acronym MORA stands for
minimum off-route altitude. It's a Jeppesen term, found only on Jeppesen charts
and defined in the company's chart glossary as "An altitude derived by Jeppesen...it
provides known obstruction clearance within 10 nm of the route centreline."
NOS Off-Route Obstruction Clearance Altitude (OROCA) and Jepp's Minimum
Off-Route altitude (MORA) are supposed to provide obstruction free direct
routes. These altitudes are the same as appear in each quadrant of the sectional
Minimum Descent Altitude (MDA)
As written by the FAA the lowest
altitude, expressed in feet above mean sea level, to which descent is authorized
on final approach or during circle-to-land manoeuvring, in execution of a
standard instrument approach procedure where no electronic glideslope is
Lowest mean sea level altitude during non-precision approaches.
This is one of the most
dangerous flight altitudes in all aviation. Single pilot operations that require
the pilot to find the runway indicators make the presence of an flight ‘looking’
assistant very desirable.
You cannot deviate from the
published approach procedure unless you are in VFR conditions and you have
cancelled IFR with ATC. The published IFR altitude for a final approach segment
is the minimum descent altitude. (MDA)
Requirements for descent below
Minimum Descent Altitudes. (MDA)
1. Aircraft in position to make normal approach and landing
2. Approach threshold or approach lights or other airport markings are visible
3. Flight visibility is not less than prescribed visibility for the approach.
4. Arrival at missed approach point or thereafter requires both 1, 2, and 3
above or a missed approach must be
commenced. FAR 91.175
5. Doing the published approach may give lower (ice free) altitudes than taking
vectors due to vector minimums.
#1 of the above creates a
particular problem for non-precision approaches where the runways are typically
shorter than for precision approaches. Any excess airspeed carried in the
approach but not required for landing must be dissipated. Diving for the runway
will not work. The placement of the non-precision missed approach point
precludes a normal landing unless the landing decision can be made prior to
reaching the missed approach point.
It is usually considered better to be at the MDA well before you reach the
missed approach point since it allows you to design a VDP from which you will be
able to perform a normal landing. An additional advantage is the stabilized
level arrival allows more time for creating the best landing configuration ahead
of time with sufficient time to configure for the missed approach. If you can't
make a normal landing you will be below the circling minimums, you must execute
Having the missed approach point
at the end of the runway will preclude the making of a normal landing approach
unless the runway is over a mile long. or if a strong headwind exists. Time and
airspeed must be under control or serious problems of decision making will
1. Do not descend or use flaps until
2. Any airspeed greater than 91 kts raises your category.
3. Lose sight of runway--GO AROUND by flying runway heading in a climb. You must
have an identifiable
portion of the airport in view visible to the pilot while above the MDA.
4. Only circling minimums are published in a letter coded approach (VOR-A)
straight-in minimums are not
authorized but if conditions allow you may land straight-in.
5. You do not need to worry about other aircraft inside the circling manoeuvring
area when in Class D airspace.
6. You may well be concerned about other aircraft when flying circling minimums
at an uncontrolled airport. Left
patterns unless contra indicated.
7. Circling at night is more dangerous than during the day.
8. Do not descend below MDA until on base leg. If at an unfamiliar airport fly
the MDA of the class D aircraft for greater flexibility and obstacle avoidance.
Non-ILS Circling Minimums
One way to fly glide slope down to
localizer circling minimums. Then proceed at MDA on the localizer by timing or
DME if authorized. Another way is to fly the LOC to the VDP and landing straight
in or fly the ILS to the circling minimums for the circle.
A straight-in approach has minimums
of alignment and descent. A descent gradient of 300' per mile from the FAF to
threshold is standard but 400' can be used. The approach course must be within
30 degrees. Some straight-in approaches have only circling minimums because of
obstacles. If visibility allows you see the runway requirements at the circling
minimums you can land straight-in. You should have a VDP pre-decided in such an
event. A straight in approach mandates than a procedure turn may not be
performed unless a specific clearance is obtained.
Non-precision criteria for
minimums can have obstacles above the MDA within one mile of the approach fix.
Chop it and drop it procedures are not ALWAYS the best way to fly. A straight in
may have only circling published minimums if the approach will not allow a
normal descent. If you maintain the circling MDA and can make a straight in
without excessive manoeuvring or rate of descent, get the clearance and do it.
Estimated Time of Arrival Minimums
If you find your ETA to a fix is
going to be off by over THREE minutes you should advise ATC. The safest ETA
estimates seems to be "6" minutes.
Alternate Airport Minimums
FAR 91.103 says that pre-flight
includes knowing runway length, aircraft performance and alternatives available
if the planned flight cannot be completed. FAR 91.167 adds fuel required to
destination, then to alternate and then for 45 minutes. Based on these FARs,
especially FAR 91.169, an alternate (plan) is required for all IFR flights
except when destination has an approach and is forecast to be 2000' and three.
An approved alternate must have
weather reporting (It can be an area forecast) and the instrument procedure must
be continuously monitored. If an airport is not authorized as an alternate one
of these factors is probably missing. Where a planned alternate has more than
one approach, one of them may be listed as NA as an alternate. The airport can
be used only if another approach is used.
Required if not:
Standard 600'& 2 precision; 800' & 2
non-precision. Requires operating weather observer on site or AWOS/ASOS
Mnemonic: ABCD123 = 1 hour After/Before, Ceilings 2000', Distance 3 miles.
Published in DPs, STARs, Terms and
On an IFR flight plan into an airport without an instrument approach, you MUST
have an alternate regardless of weather.
The prudent pilot sets his
sights on the "filed paper' alternate early on. If the ceiling is forecast at
the destination to be less than 2,000' AGL and visibility less than 3 miles, an
alternate is required. A terminal forecast (not Area) is required for
determining alternate weather minimums. "Occasional implies 50% chance or
greater and "chance" is less than 50%.
Terminal weather observation and
reporting facilities must be available for the airport to serve as an filed
paper alternate airport. If the weather is good as, required in FAR 91.169 to
descend from MEA and land in basic VFR, all you need for planning is an area
forecast saying so and a runway. Even when an alternate is not required you must
have options in mind.
ATC has no record of your filed
alternate option. As a Part 91 pilot you should have immediately at hand a
takeoff alternate with plates available. The idea is that if you can't return to
your departure field you should have a near-by airport available as an real
emergency as required alternate.
Minimum Sector Altitudes
MSA give 1000' obstruction clearance within 25 NM including mountains.
MSA is measured from markers on ILS approaches, the NDB on NDB approaches and
runway threshold on GPSs. MSA does not apply in mountains, which require 2000'
The Minimum Safe Altitude
The Minimum Safe Altitude (MSA)
circle has nothing to do with the approach or the initial approach altitude or
the approach segments or the procedure. The MSA is for emergency purposes only.
Minimum vector altitudes (MVA)are usually below the MSA. The required obstacle
clearance (ROC)of the TERPS procedures for making an instrument approach
procedure also set that the ROC of the MSA must be 1000’ higher than any
obstacle within the circle. The MSA circle may be divided into sectors for any
approach except for the GPS approaches. The MSA is essentially a non-functional
part of the approach plate.
Rule of Thumb:
Take half of your ground speed and add a zero. Read result as fpm descent
rate for a 3-degree slope. As with so many things about flying, getting away
with a descent below minimums may be the worst thing that can happen to you.
Just because something like this works at airport A is NO reason to believe it
will work at B. Obeying minimums is a guarantee that you will live to fly
Normal Landing After MDA
If you shoot a non-precision
approach at MDA and time, it is unlikely that you will be able to make a normal
landing. The nose will block your view of the runway at the missed approach
point. Your legal options are to apply flaps early to improve your ability to
see the runway. The more flaps you use the better you will be able to see the
runway and the lower will be your stall speed.
FAA Separation Requirements
The most tightly limited requirement relates to assigned altitude.
When in other than Classes B or C airspace, ATC is not charged with separation
of IFR from VFR traffic.
In Class E, ATC may call out traffic but there are no separation requirements.
Over 10,000 feet ATC will advise of traffic than is merging. POTUS gets
merging advisory all the time.
You have only one minute to ask for a vector to avoid traffic before you will
be meeting that traffic.
Course deviations are not as likely to cause a problem as are altitude
You can declare an emergency and then deviate. You may be asked to give an
Everything ATC says and that you say is tape-recorded.
Keep an ASRS NASA form in your flight bag and fill it out just in case.
Anything you say on the radio can be used against you.
Minimum En route Altitudes
Provides altitude buffer above controlled airspace of 500' and 300' for
transition areas with exceptions.
Guarantees communications if not with ARTCC then another ATC facility.
Will be above the MOCA, which provides 1000' as standard and 2000' in
Be at or above the MRA
Allow crossing VOR radial without DME
Exception is where MRA is higher and noted on chart.
Adequate for crossing a fix with higher MEA on other side.
Where MCA is established for a fix it is because the minimum climb rate
required exceeds standard.
Provide an acceptable navigational signal for route.
Where gaps occur, they are noted on the charts.
Minimum Descent Altitude (MDA)
— The lowest altitude, expressed in feet above mean sea level, to which descent
is authorized on final approach, or during circle-to-land manoeuvring in
execution of a standard instrument approach procedure where no electronic glide
slope is provided.
Minimum En route Altitude (MEA) — The lowest published altitude between
radio fixes that guarantees adequate navigation signal reception and obstruction
clearance (2,000 feet in mountainous areas and 1,000 feet elsewhere). It is
normally the lowest altitude you would use during an IFR flight on airways.
Minimum Sector Altitude (MSA) — The lowest altitude which may be used
under emergency conditions which will provide a minimum clearance of 300 m
(1,000 feet) above all obstacles, located in an area contained within a sector
of a circle of 46 km (25 nautical mile) radius centred on a radio aid to