Lost Radar Contact
AIM says that if radar contact is lost the pilot/aircraft must resume
"normal position reporting". This means
using the PTAEN
mnemonic for position, time, altitude, ETA to next and name of fix that follows.
Estimates should be based upon time but distance is o.k. as an add-on.
A proficient IFR pilot should be able to fly using partial panel to minimums in
Turn coordinator vs Needle
Needle/ball vs turn coordinator. The turn coordinator is not as good as the
needle in showing a turn or wings level since it shows wings level before the
wings are level. A pilot may make several tries before getting wings level when
using the turn-coordinator. The needle 'senses' the turn
The attitude indicator gives
instantaneous indication of pitch and bank. It is the only instrument on the
panel that provides a clear picture of the flight attitude of the aircraft.
Most modern AIs permit full 360-degree rotation about the roll axis with pitch
stops at 60 degrees. Marked to show + 50 degrees nose up/down and 20
degrees when inverted. but no specific degrees by markings. Do not have caging
The attitude indicator (called
the artificial horizon in former years) has a vertical gyro as its spin axis.
They do precess but it has an erection system activated by gravity that resets
it back to the vertical. The AI has bank markings up to 90 degree banks. The
first thirty degrees is divided into 10 degree units. Very close to the standard
rate turns can be achieved by reference to the AI. Every airspeed has a degree
of bank (coordinated) for a standard rate level turn; this is about 15% of
airspeed; 15 degrees at 100 kts, 12 degrees at 90 knots. Use turn coordinator
with ball centred to confirm angle required.
A Navy study found that during major attitude changes 85% of experienced IFR
pilots focused on the AI. When the AI is set for level flight its
movement can be set to position the nose for any selected climb speed. There
will be a consistent correlation between power, trim, nose attitude and AI
attitude. Knowing this removes the aircraft as a problem.
Instrument interpretation means
to look at the instrument and make an appropriate correction for the indication.
Instruments in a given flight condition are selected for pitch, bank and power.
You set the aircraft attitude and power to get the trend you want. You fine tune
using the instruments with numbers. Begin any manoeuvre using the attitude
indicator (AI). Set the AI, check the trend of climb,
descent, level, and turn. Now go to the numbers for making the selected
flight condition precise.
Ability to scan from the Set
AI to check the trend to the numbers back to the set
requires prior knowledge of where you are going to move your eyes. In level
flight, with a predetermined power and airspeed, the scan can be a relative easy
and slow AI, HI, AI, Alt, AI. The scan must be changed and accelerated if a
change of heading is required and even more speed if a descending turn is called
for. The sequence of required instrument scan is not so important as keeping
the eyes moving always back to the AI
Use the AI as the central
instrument. It gives direct indication of pitch and bank information. It is
the best single source of aircraft attitude. Flying the AI makes you safe.
Make your turns with AI, check TC for accuracy, the VSI for perfection and use
the HI (numbers) to measure results. Scan should include the AI in every
second or third fixation. (You can't see when your eye is moving.)
The AI gives pitch attitude,
bank attitude and bank angle
Attitude Indicator Errors
The erecting mechanism operates
continuously but is limited to 3 degrees per minute to avoid errors due to
sensed 'gravity' during banks. During prolonged banks in one direction this
error can be significant. Very shallow bank turns or flying out of rudder trim
for long periods can produce errors. Any manoeuvre that displaces straight and
level will result in AI error if it lasts long enough. Coordinated and
uncoordinated turns will do this. It is for this reason that holding patterns
have the one-minute level flight legs after each minute of turn. This leg
allows the AI to settle itself. This may be the reason the FAA prefers the
45/180 for the procedure turn instead of the simpler 90/270.
When making a 180-degree steep
turn and then rolling out your attitude indicator will show a nose up and wing
down in a direction opposite the turn. The error is inherent to the erecting
mechanism. The errors tend to cancel in 360 degrees. Taxiing turns are always
skidding turns. It is normal for the AI to show up to five degrees of tilt
during taxi turns. Any more requires investigation. AI gyrations during initial
start of the engine is normal. If the bar fails to stay horizontal or tips over
5 degrees during taxi, it must be deemed unreliable.
A vacuum powered attitude
indicator gives warning of failure. It
will be slow to erect and may go through gyrations while erecting. It may be
sluggish in flight. To see what an instrument does when it loses power--when the
vacuum pump fails, for example--watch it run down after shutdown. There is no
way to predict what an instrument with an internal problem will do. Don't
chance flying IFR with an instrument that has failed and then recovered.
Don't fly with one that is even suspected of being faulty. Being on partial
panel (real failure) in IMC requires landing at the nearest suitable airport.
Report failure to ATC. Airports with ASR approaches can give no-gyro approaches.
On final, turns should be at half-standard rate. If controller offers no-gyro
approach take it.
The AI and TC operate on vacuum
and electricity respectively. The AI has a device to automatically align it to
local gravity as seen in the cockpit If
the information is conflicting (you know the standard rate reading of the AI for
the different airspeeds) suspect one system has failed.
Go immediately to the Compass as a friend you can
Airspeed and VSI (VSI shows vertical trend after a few seconds)
Altimeter (FAA primary-with the numbers)
TC gives roll into turn rate, turn rate and coordination
HI (FAA primary-with the numbers)
Airspeed indicator-with the numbers
The turn coordinator is usually an
electrically driven gyroscope. It is mounted at an angle of 30 degrees with the
back slanted downward. It is dampened to reduce the reaction to turbulence. It
originally served to control single axis autopilot's. It senses both yaw
mostly and roll rate slightly. Initially it senses roll and when the bank is
established it senses yaw (rudder) input. Knowing the airspeed, the angle of
bank can be inferred. The TC ball (slip-skid) indicator is smaller than that
on the older needle and ball instrument. The TC will indicate the direction of a
spin so you will know which rudder application is opposite. This is not true if
the spin is inverted. In an inverted spin the turn coordinator will give
incorrect information for recovery. A
failed TC will "park" level. A very good reason not to use as a level flight
indicator except in emergency.
Overhaul calibration of both TC
and Needle is done by adjusting centring springs. As the springs weaken with
age sensitivity to yaw increases so does gyro friction increase with age with a
decrease in sensitivity. The net effect of these changes are unpredictable.
Ground check of T.C. operation is that in a left turn the ball moves to the
right and aircraft remains level.
The needle's gyro axis is mounted
horizontally and spins up and away from the pilot. It tilts on the roll axis up
to 45 degrees. It cannot move on the vertical axis. A yaw of the aircraft causes
the gyro to yaw in the opposite direction. Reversing linkage gives correct
direction and amount. Oscillations are prevented by a dashpot mechanism. British
slang name for turn and bank indicator is, "Bat and ball."
Use 45 degree markers on heading
indicator to fly 45 degree intercepts to airways, runways and 45 degree holding
pattern entries. Common procedure is to only set HI in level un-accelerated
flight. Setting the HI should be part of every instrument approach
checklist but especially the NDB approaches.
Even if the heading indicator perfect it could not compensate for the precession
caused by latitude. .This is the effect that latitude has to induce a constant
rate of precession for the latitude. Practically all great circle routes are of
a constant setting. Magnetic variation is not adjusted in an ordinary heading
indicator but can be self correcting if aircraft is equipped with a gyro compass.
A single instrument usually provides the best information for a
The use of secondary instruments is a MUST to provide the required redundancy to
verify the validity of the primary instrument. The eyes must flick stop and
flick from instrument to instrument. Any references to charts of paper should
not exceed 3-seconds. Learn to improvise and deal with what you have where you
have it. Control changes are made by finger pressure. IFR control input is
by pressure not movement.
Straight and Level
Bank Pitch Power
HI, TC, AI, Alt, VSI Controls airspeed
If power is not a variable then airspeed indicator is a pitch control.
Changing speed from cruise, to low cruise, to slow flight, full flap slow
flight and back again while maintaining headings and altitude.
Bank Pitch Power
AI then TC, AI VSI, altimeter, AI
Constant airspeed with throttle.
There are subtle difference in making
airspeed manoeuvres. If you are fast, slow or just right, in level-flight make
power raise or lower the nose for you. Trim after the attitude/airspeed is
acquired. Levelling off is done by leading by10% of the climb rate or
IFR Steep Turns
Practice with both full and partial panel
Roll into steep turn
Use VSI for pitch because of its sensitivity
Altimeter lag will make holding pitch/altitude more difficult.
Lock arm and elbow
Increase power as needed
Rollout requires immediate forward pressure and rudder application
Advanced practice would be doing 360s or 720s linked in both left and right
As with full panel instrument
flight, partial panel flight requires that the pilot be able to fly using pitch,
power, and trim in such a way that achieving and maintaining level flight can be
done using known performance factors of the aircraft. Once flying the airplane
is not part of the IFR problem then the pilot can use the instruments to achieve
desired performance. Partial panel flight control can only be reached using the
mind and eyes while interpreting instruments.
The lighter the touch the better.
In level flight the altimeter is
an indirect indication of pitch attitude being level. Any rate change in the
altimeter up or down is an indirect indication of a climb or pitch attitude with
constant power. The pilot must learn to interpret the rate of movement as an
indicator of attitude. What we wish to achieve is slow movement caused by
gentle changes. Any effort to react abruptly will result in over-control.
The pitch change occurs immediately but the instruments have delayed reactions.
Always make pitch changes slowly and smoothly. These will get the plane
where you want it with positive control. Your reaction to an altitude deviation
should be a slight change in pressure designed to slow down the needle movement.
If the needle reacts abruptly too much pressure has been used. The slower the
needle moves the closer the aircraft is to the desired attitude.
Using the vertical speed
indicator as a direct indicator of pitch attitude can lead to abrupt
over-control or chasing of the needle.
This is a most common student error since the VSI needle tends to be quite
active. The VSI is a trend as well as a rate instrument. Once again, only
very light control pressures can be used successfully to stabilize the VSI.
Rate Altitude Changes
In straight and level change to climb
Use power (full) to get 500 fpm climb
Adjust pitch for airspeed
Primary for pitch is VSI
Airspeed is primary for power
Coordinate pitch and power for performance
Reduce power for 500 fpm descent
(-Five rpm for five fpm)
Adjust pitch for constant ias
Ias is primary for pitch until VSI is 500 fpm descent
VSI becomes primary pitch
Power primary for airspeed
Coordinate pitch and power for performance.
Constant power and airspeed. From cruise, raise nose, then power, then
trim. Airspeed is primary pitch.
Power for airspeed to make airspeed
primary for airspeed. IAS and VSI for pitch.
Altimeter for pitch, power for
airspeed. (Do not reduce power until reaching desired airspeed.)
To fly well you must master
these basic manoeuvres. Though never written into the PTS there are several
identical pilot control applications that coordinate pitch and power to achieve
needed performance. Most control applications require that the pilot
anticipate errors because the corrections required are apparent.
power for airspeed. (do not reduce power until reaching desired airspeed.
The compass is the least likely to
fail and any change in its numbers would indicate the opposite direction of
turn. If ever the turn coordinator disagrees with the attitude indicator use
the compass to break the tie. Heading indicator as a vacuum partner with the
attitude indicator is a biased juror.
This material is included in the
VFR material but is repeated because of the partial panel requirements of the
IFR PTS. Mounted on the face of an aircraft compass is a chart. This chart is a
record of compass error called deviation. As a pilot of a particular aircraft
you should copy this chart for use in navigational planning.
Many airports have an area set
aside for a compass rose. This rose is aligned using the variation between the
True North and Magnetic North for this specific area. It shows the magnetic
directions such as are used to align the airport runways. It is a place where
aircraft are positioned and 'swung' through the various magnetic directions.
This 'swinging of the compass' is done
with all electric circuits functioning so that the operation of the compass will
reflect this fact when flying.
As the aircraft is positioned on
the eight magnetic courses a small pair of adjustable magnets are moved so as to
get the most accurate compass reading possible. As these adjustments are made, a
record is made of the compass direction of the aircraft on the rose as compared
with the best-adjusted reading of the aircraft compass. This record is
transcribed on to the deviation chart affixed to the compass.
In most cases this deviation is
only one or two degrees. This exceeds the straight line flying ability of a
pilot. However, with the advent of the Global Position System, it is becoming
important to note deviation as a factor in navigation beyond the Practical Test
Standards or the FAA written.
The numbers on the compass are
opposite in order and direction from the HI. The reversal of the two numbering
systems requires us to be consciously aware of the difference. Setting the
compass to the HI requires that we note the compass lubber line is between two
numbers either centred or near one than the other. These two numbers are
then located on the HI and the HI set to correspond.
A usual student error is to make a mistake setting
Flying with the compass is quite
different from using the directional gyro. The compass has several inherent
errors relating to turn, speed and geographic latitude. The compass should
only be "read" in level un-accelerated flight. It is best (easiest) to
make compass turns using the turn coordinator and time. At 3 degrees a second a
turn of two minutes is 360 degrees, one minute 180 degrees, 30 seconds 90
degrees and 10 seconds 30 degrees. A normal count of 1, 2, 3, (4) will be close
to 10 degrees. On the ground a compass should only be checked while taxiing
straight or when stopped at a known heading.
The swinging and dipping of the
compass during a turn or acceleration due to changes in speed or direction is a
physical phenomenon caused when the north seeking end of the compass dives
toward the north magnetic pole. The higher the latitude the greater the dipping
tendency. Turns from a northerly heading lag behind the turn; turns from a
southerly heading lead the turn. When the card is banked the compass dips to
the low side of the turn. ANDS is the mnemonic for acceleration errors.
In a shallow 360 turn the compass is most accurate at 90 and 270 degrees. In a
smooth turn from a south heading the rate shown on the compass exceeds that of
the actual turn at a diminishing rate until at 90 or 270 degrees. See AC 61-27C
In the planning of a flight the
use of the mnemonic "True virgins make dull company" gives the order true
course, variation, magnetic course, deviation, compass course, wind, wind
correction angle, to provide the compass heading required for the flight. In
level un-accelerated flight the compass is unaffected by turning or acceleration
errors. The compass is the self contained and independent means of determining
FAR 91.175(c)(2) defines visibility prescribed for an approach.
FAR Part 1 defines both flight and ground visibility, and there Is a
difference in the two meanings.
what you will look for before beginning the approach.
Study the approach lighting and runway length.
MALS lighting system is 1400í; MALSR is 2400í
Learn to count runway lengths to the airport as a means of determining
Part 91 Visibility Factors
Part 91 takeoffs have no minimums
Part 91 landings have three prerequisites
1. Normal descent
2. Minimum visibility
3. Runway in sight
You cannot descend below DH or
MDA unless you have minimum flight visibility required by the approach plate.
This determination of minimum is done by the pilot. The IFR training program
does not teach you how to determine visibility. Reliance on a 45 minute old ATIS
is likely neither valid nor reliable.
The most difficult phase of any approach in actual conditions is where the
transition for instruments to visual actually occurs.
You will be at the decision
height about an eighth of a mile before you should see a runway at ILS minimums
of a half-mile. Seeing the runway before reaching decision height means you
have the required visibility. Seeing the approach lights but not the runway
allows you to continue but the missed is your best option. Knowing that each
group of lights are 200í apart gives you a handy distance reference to the
runway. If you see all of the MALSR you have required visibility. Seeing all of
a MALS system is less than a half-mile of visibility, go-around.
Average forward horizontal distance,
from the cockpit of an aircraft in flight, at which prominent unlighted objects
may be see and identified by day and prominent lighted objects may be seen and
identified at night. Flight visibility is determined by pilot. A pilot
may not land an aircraft unless the flight visibility is as prescribed in the
Prevailing horizontal visibility
near the earth's surface as reported by an accredited observer. Reported
ground visibility has no reflection on actual flight visibility. Landing and
takeoff visibility are ground-based measurements.
Visibility above the minimums is
a two-way street. It makes the takeoff safer but does not, necessarily assure a
safe landing. Regardless of conditions,
planning and flexibility are the keys.
Zero/zero takeoffs are in themselves
not particularly hazardous.
Its the Ďwhat-ifsí related to
engine failure on takeoff or having an immediate need for an alternate landing
field that makes such takeoffs ill advised.
A straight-ahead landing requires that you know what is there even though you
canít see. You must review and know the departure area to gain even some element
Low visibility takeoffs require
that you maintain runway headings and low visibility landings require a minimum
visibility. A Part 91 pilot can depart in zero/zero but must have visibility
minimums and the runway environment in sight before descending below MDA or DH.
What you hear on the ATIS is not controlling. Itís what you see.
Clouds or rain are most often as
stated. Fog can be variable and change rapidly. If fog is a factor be prepared
to go to an alternate. Use a second pilot to call outside the cockpit
while the first pilot stays on the instruments. In single pilot
operations the greatest hazard in such conditions is to let your sink rate
increase while you are looking for an opportunity to dive for the runway. Donít!
Single Pilot IFR
The IFR pilot can fly into IFR in
three different ways. He can fly into un-forecast conditions or into forecast
conditions. Regardless of the planning some un-forecast conditions are a
probability to be either better or worse. The degrees of certainty of a
forecast is still making an IFR flight a study in risk taking.
A pilot needs to interpret a weather briefing, ask appropriate questions and get
the notams. Additionally, pilot must have the assurance, skills, knowledge,
references, preparation and experience needed to avoid an accident. The aircraft
must be IFR capable and the cockpit must contain the requisite charts and
publications for the flight. Just having them may not be enough.
Availability is an essential.
Is single pilot IFR a risk
taking exercise out of proportion to any possible needs? It certainly is if you
succumb to those pressures inside and outside that take you past any personally
imposed minimums. It certainly is if you cannot or have not planned the flight
with an escape route. It certainly is if your gut-feeling is that you are in
over your head.
It is not possible to substitute IFR simulation for the experience of actual
IFR conditions. Only actual conditions can give you the turbulence,
precipitation, wind shear and lighting changes that can cause vertigo.
Compounding these conditions will be ATC speed-talk, demands, clearances,
inquiries, and requests for readback. Worst of all will be that the controllers
who have concocted the clearance are not talking the language of the controllers
who direct traffic.
The IFR pilot must have
automatic control of the aircraft through coordinated turns, stalls and
patterns. The fundamental skills of IFR are straight level flight, turns,
airspeed climbs and descents, a light or hands-off yoke touch, and throttle
movement. A weakness in any of these areas will compound any procedure
problems. Early mastery of these basics will reduce training time in the long
run. If you can't fly using the gauges without thinking about it, you won't have
the ability to think about all the other things involved in navigation and
Primary instruments are always
the ones with the numbers. (Never say
always.) For straight and level it is the altimeter for pitch, the heading
indicator for bank and the tachometer for power.
When an airspeed is assigned then the
IAS is primary
for power as the throttle is adjusted to maintain airspeed.
Ability to maintain heading and altitude over a distance is a basic requirement.
The turn requires that the altimeter be used for pitch and the turn
coordinator for bank. Tachometer is primary for power. As before,
required airspeed is controlled by power adjustments. The TC should be
calibrated by doing timed turns. The rate of turn is based on airspeed and
angle of bank. Turn rate decreases with reduced angle of bank and an
increase of airspeed. Standard rate turns can be figured by using 10% of
and adding five. Limit your angle of bank to the angle of small heading changes.
Five degrees for five degrees. Use the standard 1/2 angle lead in rolling out
to a heading.
Constant airspeed/power uses the
airspeed for pitch, the HI or TC for bank, and tach for power. Lead altitude by
10% of your rate of climb or descent. A constant airspeed climb/descent while
turning you decrease pitch with increase of bank angle. Airspeed will be
constant but descent rate will increase and climb rate will decrease. Pitch,
bank and power are all changed.
You can practice constant
headings first by constant airspeed and them by constant altitude. The variables
are made through power changes from full to idle. This requires great attention
to the rudder, elevator and throttle coordination. For constant airspeed the
hands move in opposite directions to get pitch and power. Initiate the climb
until stabilized then set up the descent. Repeat until you can anticipate the
coordination required to keep constant airspeed.
The constant altitude requires a
sequenced movement of both hands in the same direction. This exercise will
require trim adjustments. Power is changed from full to idle and back again.
Rudder applications must be anticipated to hold constant heading. Using power go
from full power and back to idle several times.
Never make descent below DH or MDA unless you can see at least one of
visual items required by FAR 91.175.
IFR to VFR Scud Running
Contrary to popular opinion, there are valid occasions where reliance on
scud running skills will be both useful and successful. There are several
criteria that determine both usefulness and success.
Fly only into improving weather.
Fly only in VERY familiar areas
Know the Class G airspace rules for visibility and cloud clearance.
Long distance scud running is not recommended.
SVFR and contact approaches must be requested by the pilot.
Know your limits.
Not everywhere nor every time.
Donít fly instruments unless you are
current and proficient.
ATC facility malfunctions are rare but happen due to lightning strike, phone
line cuts, computer crashes and saturation of system.
Aircrew problems such as repeated failure to execute approach, severe weather
beyond crew competence, fuel and situational awareness
Aircraft equipment failure, maintenance or capability
Don't let a situation become dire before taking actions and know what to do
ahead of time. Most dangerous inadvertent unusual attitude is the spiral dive
with increasing airspeed:
What to do:
Level flight by watching altimeter.
Greatest hazard is over-control.
FAR 91.3 states: "In an
in-flight emergency requiring immediate action, the pilot in command may deviate
from any rule of this part to the extent required to meet that emergency."
Two-way com failure is an IFR emergency.
Why and How to Detect Instrument Failure:
Instrument failure is not always
accompanied with a warning flag. As a
part of your pre-approach briefing you should crosscheck all instruments to
assure proper operation of primary instruments. Failure to make a verbal
approach briefing makes such a crosscheck essentially impossible.
Airspeed drops or stays at zero with probable cause blockage in pitot tube
Ice is most common cause.
If weather has been cold enough to freeze water, turn on pitot heat during
Failure to remove pitot cover is an embarrassing possible.
If blockage includes some indication of airspeed, the indicator reacts
as an altimeter.
An increase in altitude causes an increase in airspeed. Descents decrease
Vertical Speed Indicator
Cause is blockage at static port
Solution is use of alternate air or break VSI instrument glass
1. Airspeed will indicate higher than actual
2. Altimeter will indicate higher than actual
3. VSI will show false climb
Attitude Indicator and Heading Indicator Failure.
Suction gauge zero.
Cause is failure of suction pump
Solution is to go to back-up suctions
Cover HI and AI as soon as possible. Use paper, money, post-its, anything..
Airspeed indicator will act as pitch indicator
Turn coordinator for bank info.
Compass for heading
Electric System Failure
Safe IFR flight is possible
following an electrical system failure with only the pitot-static and vacuum
instruments. Electrical systems usually fail slowly if the problem is in the
alternator. Reduce electrical load to save battery. X-ponder only is good
option. Radios on only for assistance. No nav radios if being vectored.
Know where nearest VFR lies and head that way. ATC will provide traffic
Note: On average only one accident a
year occurs solely due to vacuum pump failure where the pilot detected the
failure and flew for nearly an hour before task overload precipitated the
accident. Usually only fatal accidents. Keep your partial panel skills and
cover failed instruments. Get down or VFR
Early warning of vacuum failure
is the need to repeatedly reset the heading indicator.
Vacuum systems tend to fail gradually. If the autopilot is coupled to the AI,
the failure of vacuum pressure will cause autopilot to follow AI as it spins
down until the autopilot's limits are exceeded. The inability of the pilot to
detect this failure is believed to be the cause of many 'structural failure'
accidents. The vacuum pressure gauge
must be part of the scan.
If the vacuum pump fails, an
electric turn coordinator and the pitot-static instruments provide sufficient
information for safe instrument flight.
An electric AI backup vacuum system is a worthwhile installation. See material
on C-182 RG and it's vacuum back-up system.
Vacuum pumps fail because of
contamination, heat and age. Pumps
are usually flown until failure but a lead-in clue is no pressure at idle.
The operation of the engine driven pump is to suck air across the instrument
gyro wheels and exhaust it into the engine compartment. The intake air comes
from the cockpit through a filter. Cigarette smoke ruins the filter.
Of the three systems subject to
failure, only the vacuum pump is normally flown until it fails. Fly long enough
and you will experience vacuum pump failure. Given a choice vacuum pumps
seem to prefer to fail in IFR conditions. A vacuum failure will cause
the AI to indicate a slow turn where none was made or intended. The HI will
begin to spin
Vacuum pumps die in several
ways. The slow death occurs due to age, heat and contamination. Clean filter,
good tubing and cooling will help prevent the slow death syndrome. Catastrophic
failure is lack of internal lubrication. The gyro instruments will begin to spin
down from their 17,000 rpm speed and the instrument will begin to tip or spin as
the case may be. It is this gradual failure that causes loss of control.
It is nothing like the sudden application of covers during simulated
Dual vacuum pumps have common manifold to gauge which isolates pump not in
use. Alternate use of pumps necessary to determine that both are functional.
Any failure unrecognized in IMC conditions is an emergency.
The longer the flight with a recognized failure continues the more
likely a loss of control accident.
Accidents have occurred when pilot departed into IMC knowing vacuum system is
Partial panel proficiency is, at best, a time limited 'parachute' in high
performance high task situations.
Standby vacuum back up or electrical back up advised for frequent IFR
aircraft and pilots.
Vacuum failures are like earthquakes, it is going to happen, there is no
A slow failure of vacuum system is the more deadly of the failures since it
is unlikely to be noticed.
Single failure of one instrument, such as AI, is most apt not to be
Recognition of failure is just as, perhaps more, important than partial panel
Essential safety equipment is immediately available way to cover failed
HSIs can be either electric or pneumatic every pilot MUST know which he
Know how to use turn coordinator and clock to make 180 degree turn.
Ask for help
In a thunderstorm pitot-static instruments (airspeed, altimeter, VSI)
become unreliable due to radical pressure differences. The pitot heat should
be part of the "actual" IFR checklist. Use pitot heat at first sign of
visible moisture or loss of airspeed, expect high electric drain. Heavy
rain/thunderstorm pressure changes may affect IAS accuracy. Pitot/static systems
can be checked by use of alternate air. Breaking the VSI glass will cause
reverse reading by the needle. Best sign of blocked static is constant
System Cross-Check for Failure
There are three mutually
independent instruments that are available in IFR flight to correct bank.
If one of the instruments differs from the other two, believe the two and cover
the one. The AI, vacuum powered, is a bank (and pitch) instrument. The turn
coordinator is electric. The compass is the third independent bank indicator.
The failure of a single system only reduces the redundancy available to the
pilot, not the capability.
ATC, request assistance
Request vectors to best airport
Request radar assisted approach
Vectors to final
Shallow intercept outside FAF
Surveillance and course deviation information
Relying on memory to perform the
required cockpit procedures is a relatively dangerous way to fly.
Even the simplest aircraft will have over 100 specific steps required when
progressing from preflight to tie-down. A complex aircraft may have eight times
as many steps. All of these steps are as individualized as the aircraft and
pilot.. The best way to develop such a checklist is to break the list into
sections that can be counted on the fingers. Sections that can be designed
to flow in sequence across, up or down the panel. You need sections that are
systematically used in positioning and selecting cockpit switches and controls.
The key to a flow checklist is doing the same thing in the same order every
time. Only such a checklist can provide the maximum protection against
interruptions and distractions.
Some situations do not lend
themselves to checklists. Some numbers from the POH must be memorized and backed
up in a readily available source such as the back of a lap board. The PIREP,
standard frequencies, airspeeds, that might have a memory failure under stress
need to be quickly available. Any PTS checkride at any level either
states or implies that the pilot must comply with use of the appropriate
checklist at some point in every procedure. The pilot can make the
choice of before, during, or after in fulfilling this compliance.
Other situations do lend
themselves to short term memory use. In IFR approaches, having studied the
approach charts shortly before beginning the approach can enhance the ability to
recall essential altitudes, distances, radials, frequencies and procedures.
Ability to do this allows more time on the gauges and control input. Most
essential input into short term memory is the factors mentioned above as they
apply to the missed approach. If a communicator is unclear it is best to
re-enforce your memory bank by having the message repeated. Finally, short term
memory works best if exercised.
Once the entire approach
procedure has been reviewed and always in the same manner, there is no need to
feel under extreme time/procedure pressure to get everything done. Excess
pressure or quickness can cause the wrong thing to be done at the wrong time and
in the wrong order. A pilot who has the basic ability to perform an approach
sequence may fall into the dual traps of divided attention and limited time.
These weaknesses are usually due to poor habits and reduced management skills.
Basic to overcoming this weakness is the ability to say to yourself that a
particular task can wait until later.
Successful approach task
management means that you do the major 'killer' items at exactly the same place
during the procedure.
Knowing that you have already
made a complete approach review means that you know that the order of things can
be accomplished one at a time. When
you change to fullest tank, when you lower gear, when you adjust the propeller,
when you go to approach speed are fixed elements of the procedure. Co-tasks such
as the FAF and starting timer clock are always in sequence and before step down
descent. Good cockpit management is more a matter of attitude than it is of
technique. Your attitude should include the requirement of never looking
away from the instruments for over three seconds no matter how many times you
make the switch. Identing needs to be
done but not right away.
At some point in your training
you begin to filter the various differences of performance and procedure from
various sources and come up with your own way of doing thing. This is an
important phase of learning and flying. We have sorted out what we have
learned and settled on a preferred way of doing things. Some of these items
are requirements, such as changes in radio or clearing the runway procedures.
Some are optional procedures as for when to reduce power, use the fuel pump, or
C.H. Lastly there are invariable elements of flying such as clearing for turns
which have not alternate acceptable options.
The 'Whys' of IFR Approach Crashes:
Breakdown in situational awareness
Inexperience with conditions
Avoiding IFR Approach Accidents
Talking to any ATC facility is
NOT a guarantee of defence against your having a mid-air. Even IFR-VFR
separation is guaranteed only in Class A, B, or C. Most mid-airs occur at low
altitudes near uncontrolled airports because that's where the airplanes are.
Aircraft shadows are your best indicator of low level proximity. Watch
the ground. As with cars there are built in aircraft blind spots that can only
be uncovered by S-turns, head nodding, and a modicum of luck. Always check
the airspace you are about to enter.
Use standard approach procedures
Fly the procedure
Have personal limits of visibility
Have personal limits of pilot and aircraft ability
Consider the missed as an always available option
Have deviation parameters for executing the missed
Have flight path and speed deviation limits for missed
Have personal limits for a stabilized approach
Be clear and understanding in communications
Beware night and runway contamination
Know your personal altitude AGL limits
Go in knowing the numbers
Share what you are finding out and doing.
Recognize any inappropriate use of power
Practice recognition of unusual attitude problems
Recognize excessive and uncontrolled descent rates
Configure aircraft for low speed operation
Learn to recognize lack of preparedness
Establish mutual understanding between ATC and pilot.
Expect night, visibility and weather contamination of references
Use Radar/GPS and altimeter
The best of approaches is the ILS since it gets you within 200' of
the runway. The diagrams do not fully state the margins shown to you by the
needles. The following figures are generalizations that do not apply to all ILS
1. At the marker (5- miles out)a one-dot localizer deflection equals 300 feet.
2. At the middle marker (1/2 mile out) a one-dot deflection equals 100 feet.
The glide slope is even more
1. At the marker a one-dot deflection equals 50 feet of altitude.
2. At the middle marker a one-dot deflection equals 8 feet of altitude.
3. The glide slope flares a wingspan
above the runway.
The non-precision approaches
have minimums in the 500' range that usually means a low IFR condition will not
allow the runway environment to be seen.
Horizontal Situation Indicator
Functions as VOR, ILS and heading
Reverse sensing is eliminated
Lubber line serves as heading index
Course Deviation Indicator (CDI) gives course flown
To/From flag and needle points parallel the to or from without reverse
Miniature aircraft gives visual angle of heading and course flown
Glide slope usually on both sides of instrument
HSI can be set to give direct indication of back-course approaches
IFR Facts Without Instruments
You can lose orientation in less than
You can be upside down and not know it
Your inner ear can be giving false information
No pilot can fly in IFR conditions
without visual reference
Physical Causes of Disorientation
The inner ear is a three-axis gyro
that require visual input to maintain spatial orientation
The inner ear reacts to rate changes, not sustained change
The inner ear will falsely interpret rate and non-rate changes without visual
The inner ear may not be 'triggered' by smooth transitions in attitude on any
Knowing how to fly instruments is no
assurance that you are competent to 'trust' your instruments
Older types of Flux gate compass were an electro-magnetic device with
balanced currents flowing in a triangle of wire windings. The balance of
currents in windings is affected by the Earth's magnetic field. A newer type has
two small coils wound on ferrite cores at right-angles to each other. The
various windings are energized in phase at a low frequency. The Earth's magnetic
field produces a small phase-shift in the windings which depends on the relative
angle of the magnetic field. Just a magnet in a "high viscosity silicon fluid".
What makes it different is that the "magnet" is an electromagnet, it doesn't
rotate and it is suspended to make it hang parallel to the earth. The
electro-magnet is activated with a 400 Hz AC signal that magnetizes the core. A
second set of three-phase windings pick up the induced voltage from the
collapsing field. Depending on the relationship with the earth's magnetic field,
this induced voltage will vary in amplitude and will be either in or 180 degrees
out of phase. The phase-shift difference is detected and measured by a circuit
detector. It can be very accurate and does not have the problems the old WWII
mechanical magnetic compasses had. It is not very different from a regular
compass. This signal is fed to a control transformer that is attached to the HSI
or DG. The flux-gate has the same dip and acceleration errors as a normal
compass. It will "fast slave" the DG or HSI to it's initial heading and add a
precession correction to data coming from a gyro.