GLIDING INSTRUMENTS

★ Compass

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○ Pendulum Mounted
– To prevent sticking during turns
– They are stabilized in fluid.
– They are calibrated in 10 degree or 5 degree divisions of a 360 degree scale with North at 0 / 360 degrees.
○ Magnetic Compass Errors
OSUN
Over shoot – South
Under shoot – North
ANDS
Accelerate – North
Decelerate – South
– They are subject to a complex series of false indications while turning or changing speed.
– Directional indications are reliable only in steady straight flight.
(1) Northerly Turning Error (In the Northern Hemisphere)
Turning    Indication
From a heading of North.    A turn in the opposite direction.
From a heading of South.    Much faster rate than is actually being experienced.
– Most apparent when turning to or from headings of north and south.
– The vertical components of the earth’s magnetic field cause the earth-seeking ends of the compass to dip to the low side of the turn.
– Over shoot rate = The Latitude – 1/2 the bank angle (36deg. – 10deg. = 26deg.)
– Under shoot rate = the Latitude + 1/2 the bank angle (36deg. + 10deg. = 46deg.)
(2) Acceleration / Deceleration Errors
Changing Speed    Indication
Accelerating    A turn to the North.
Decelerating    A turn to the South.
– Most apparent on headings of east and west and during airspeed changes.
– The momentary tilting of the card from its horizontal position results in error.
★ Yaw String

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Slip        Coordinate        Skid
Indicates    Yaw string
A Slip    Moving toward the outside of a turn.
A Skid    Moving toward the inside of a turn.
★ Inclinometer(Balance Ball)

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Indicates    The Ball
A Slip    Moves to the inside of the turn.
A Skid    Moves to the outside of the turn.
– A ball-bearing in a close fitting curved glass tube which is fitted with fluid for dumping.
– It provides slip / skid information when displaced from center.
★ Pitot Static Instruments

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ALTIMETER    VERTICAL SPEED INDICATOR    AIRSPEED INDICATOR

– The bases for the function is differential air pressure.
– The atmosphere pressure surrounding airplane changing various situations.
– As climb to higher altitude the density of air decrease therefore the pressure of air is lower. = Density altitude increase.
– Sense the changes atmosphere pressure in provides with information concerning airspeed, altitude, and rate of altitude change.
– While the pressure surrounding  airplane is vented to all three through a static port which is positioned an area relatively undisturbed air such as side of fuselage.
– Only the airspeed indicator receives the rum air pressure, which enter through the small hole at the front of the pitot tube, which is amounted as exposed to the relative wind.
★ Airspeed Indicator

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○ Operated by The Differences between Two Pressures.
– The pitot pressure is obtained from a tube facing forward and thus directly related to the forward speed.
– The static pressure is obtained from a static vents positioned so as to be least affected by speed and maneuvers of the sail plane.
– Measures difference between the rum air and static pressure and displays the result of indicate as airspeed.
– As the pressure differential changes the airspeed needle moves.
○ The PITOT
– Connected to the inside of an expandable capsule, it movement operates a pointer.
○ The Static Vent
– Connected to the inside of the instrument case which contains the capsule.
– Variations in pressure due to altitude are cancelled out.
○ Airspeed Indicator Errors
(1) Altitude Error
– Temperature variations are usually controlled in all instruments by incorporating bimetallic strips in the linkages.
– The atmosphere in not perfectly regular in its temperature variations, airspeed indicators are usually worst affected.
– They tend to under read by 1.5 ~ 2.0% per 1,000 feet up to 10,000 feet, and by more above that.
– The sailplane is actually traveling faster than the instrument indicates.
– As most gliding is done where the errors are small, they are usually ignored, except for performance testing.
(2) Mechanical Lag
– Whilst there is a small mechanical lag in most instruments delay in airspeed indicators is caused by the sailplane’s inertia.
○ Airspeed Indicator Marking & Extra Triangle Markings
> White Arc    Flap Operating Range
Flap speed maximums to indicate the relative flap position.
> Green Arc    Normal Operating Range
Covers the normal unrestricted control movement speed range to the Vno.
> Yellow Arc    Caution Speed Range
Extends from this to the Vne which is marked by red line.
Control movements in this speed range must be restricted to 1/3 of the maximum control deflection.
> Red Radial Line    The NEVER Exceed Speed
The maximum airspeed at which the sailplane should be flown in calm air.
> Orange Triangle    Maximum Sink Speed
Permits the least loss of altitude in a given time period.
> Blue Triangle
Correlate to the maximum horizontal distance covered.
> Yellow Triangle    Recommended Approach Speed.
An absolute minimum.
○ Pitot Static System blocked
○=OPEN, ×=CLOGGED
×    Air Inlet
○    Drain hole
○    Static
Indicator to drop to zero.
The pressure in the line will vent helps opening.
×    Air Inlet
×    Drain hole
○    Static
Performs like the altimeter
As climbs from altitude where the block occurred, the airspeed increases, conversely as descend the airspeed decreases.
The air pressure remains in line.
○    Air Inlet
○    Drain hole
×    Static
Indication is not correct.
Operating higher altitude then where the system become blocked, then the airspeed leads lower than it should, below the altitude, the airspeed indication is higher.
The greater the altitude change, the greater the error.
★ Altimeter

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The Longest Pointer    Hundreds of feet.
A Shorter pointer        Thousands of feet.
A Very Small Pointer    Tens of thousand of feet.
A Small Subscale        Inches of pressure.

○ Sense Change in Surrounding Air Pressure.
– Essentially a barometer calibrated in feet.
– It consists of a number of linked, sealed, copper alloy capsules which expand as the air pressure reduces with height.
– The adjustment knob also sets a small subscale reading in inches of pressure.
– The expanding movement of the capsules in linked by mechanism to three pointers.
○ Altimeter Setting    7-2-2    91.121
(1) QFE – Height
– Aerodrome level pressure setting.
– At which the altimeter will read zero when the aircraft is on the ground at the aerodrome.
– In gliding, altimeters are usually set to zero on the airfield.
(2) QNH – Altitude
– Mean sea level pressure setting.
– At which the altimeter will read the aerodrome level above sea level when the aircraft is on the ground.
– This is the setting used by all powered aircraft operations below 18,000 ft.
– When landing away from the starting field, unless the height difference is known accurately, the indication are only a guide, for cross country flying.
– Station on root with in 100 nm.
(3) QNE – Flight Level
– Standard atmospheric pressure setting 29.92 in. (1013.2 hp)
– At which the internationally – agreed standard setting is set in the altimeter subscale.
– All aircraft flying above 18,000 ft are required to operate with this setting on their altimeters, to give a common reference above that level.
○ Altimeter Check
– Altimeters are checked to an accuracy of 50 feet at sea level and 200 feet at 20,000 feet.
– Within plus / minus 75 feet of the aircraft elevation.
○ Altimeter Errors
(1) Altimeter Stick
– Altimeters are made for power aircraft.
– As sailplanes lack vibration from the engine, they often stick slightly, usually not more than 200 feet.
– If they stick for greater amounts they should be over-holed.
(2) Temperature and Pressure Error
From High to Low or Hot to Cold, LOOK OUT BELOW!!
Altimeter Setting 29.96’in -> 30.11’in
30.11’in – 29.96’in = 0.15’in
1,000ft x 0.15’in = 150ft
Altimeter indicates 150ft HIGHER. You are flying 150ft below indicated.
– Colder than standard temperatures cause the altimeter to indicate an altitude higher than the sailplane’s actual altitude.
– The same situation exists when flying from a high pressure area to a lower pressure area without resetting the barometric pressure window.
○Pitot Static System Blocked

×    Static
×    Alternate Source
The altimeter freezes in place.
×    Static
○    Alternate Source
The altimeter will read higher than airspeed faster than the normal.
The pressure  inside of the cabin slightly lower than that surrounding.
If the alternate source is not available, brake the grass of the VSI.
★ Vertical Speed Indicator (VSI)

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○ Senses How Fast The Surrounding Air Pressure Decreases or Increases As Climb or Descent.
-Displays the change as a rate in feet per minute.
– When a changing in altitude occurs, immediate resister the transit of moving, then stabilize show actual rate of altitude change.
○ Pitot Static System Blocked

×    Static
×    Alternate source
The VSI return to zero
×    Static
○    Alternate Source
Still react to change in the rate of climb or descend.
★ Variometers

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○ Show at What Rate The Sailplane is Gaining or Loosing Height.
– They all work by the reduction of pressure with height.
– They have a capacity flask which is usually a vacuum flask to insulate against heat variations, done through the static vents or a ventury
flask = フラスコ
(1) Mechanical Variometer
– These have a vane which the airflow moves as it flows in or out.
– This vane varies the size of the opening according to the rate of flow, linked to an indicator needle.
– As the airflows and forces they produce are very small, the moving parts are finely balanced and quite delicate.
– This type of instrument has a lag of one to five seconds.
(2) Electric Variometer
– These have sensing wires that carry a small electric current, in the “IN” and “OUT”
flow tubes.
– The electric conductivity of the metal used for these wire is very sensitive to temperature change. Any flow past them will provide cooling, and thus alter the electric current shown on the indicator.
– In these instruments the airflow provides no forces of operation and thus their response is very fast.
– Usually some from of mechanical or electrical ones, allowing changeable scales and adjustable damping at the flick of switch.
– As well as operating an indicator most electric variometers have an audio attachment, provides a varying or intermittent tone to indicate lift or sink.
(3) Netlo Variometer (Airmass Variometer)
– Shows at what rate the air around the  sailplane is going up or down, done by taking the sailplane’s normal height loss / speed relationship out of the instrument reading.
(From which the sink – rate of the glider at any given speed is subtracted.)
– It is most useful at high speeds and can be sometimes used to lead the sailplane to a thermal.
(Shown only sink rate of the air through.)
○ Total Energy Compensator
– For a variometer reduces the climb and dive errors that are caused by airspeed, and shows only when the sailplane is climbing in rising air currents.
– A total energy variometer has been compensated to respond only to changes in the total energy of the sailplane.
– A change in airspeed due to stick deflection does not register as sink as or lift.
– Variometers used in sailplanes are so sensitive that they indicate climbs and descents as a result of change in airspeed.
– If a sailplane is flown at speed, and then zoomed up, the variometer will show a climb as the sailplane will gain height.
– It will reduce airspeed at the same time.
– At any stage of this maneuver , the sum of its kinetic (speed) energy and its potential (height) energy will be the same.
– That is, although it has gained height, it has not increased the total energy in the system.
– Only the type of energy has changed.
(1) Total Energy Venturi
– Designed to prevent the variometer showing an “UP” reading for a gain of height caused by reduction in speed.
– If the zoom is made in a thermal and a real increase in total energy is achieved it will show “UP”.
– The venturi does this by producing a reduction of pressure equal to the pitot pressure increase.
(2) Mechanical Compensator
– May be used in order to do any with the drag of a venturi, but these are usually only accurate over a narrow height band.
(3) Electronic Compensator
Some electronic varios have this and have inputs of static and pitot pressure to provide the basic information.
○ Speed Director
– Combines elements of the airspeed indicator, variometer, and Mccready theoretical performance for the sailplane type.
(1) Mccready Ring Speed Director
– It is arranged so that the indicator needle reads zero when the sailplane is at the correct Maccready speed for the air movement around it at the time, the weight of the sailplane (ballast or not) and must be done smoothly and it needs practice to develop the skill.
(2) Electric Speed Director
– Usually have a sound system as well so that the pilot does not need to watch the indicator dial.
– Care must be taken to ensure the pilot, static and venturi tubes do not become blocked or bent to the wrong angle.
– Slip or skid in excess of 10 degrees can cause errors in some or all of the pressures, and thus cause incorrect indications.
★ Total Energy Compensators

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< < VARIOMETER >>
The variometer is essential for modern soaring flight. It is a very sensitive instruments that shows if the glider is clibming or descending, and how fast. The variometer can be calibrated in knots, feet per minutes, or meters per second.

Basic variometers work by detecting a rate of airflow between a capacity and a static source.

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When the glider climbs, the air inside the capacity expands and flows out through the instrument; when the glider descents, the airflows into the flask.
The rate at which this air flows causes the needle to deflect the appropriate amount.
Electric variometer work on the principle of air flowing past thermistors causing differential cooling which requires differential voltage to keep the thermistors at a constant temperature.
Electric variometers tend to be much quicker than mechanical variometer has double that or even worse.
< < TOTAL ENERGY >>
A variometer installed as described will work just fine, showing when the glider climbs and descends.
The problem with this simple system is that if the pilot pulls the control stick back, the variometer will the resulting temporary climb.
These pilot induced climbs and descents are commonry called “stick thermals”. These stick thermals can be cancelled out by installing any one of several total energy devices.
The most common of these is a total energy probe.
A total energy probe is usually a bent tube with slots or tiny holes on the downstream side, mounted on the leading edge of the vertical stabilizer.

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There are other ways to produce total energy, but the T.E. probe is simple, effective and inexpensive.
Electric variometers can perform this task electronically, but require an accurate static source, which may not be available on the aircraft.

An important option is an audio device for the variometer.
This can be installed on either a mechanical varionmeter or an electric one.
The audio provides an audible sound when the variometer needle deflects.
The typical climb tone is a broken beep-beep-beep that increases in pitch and frequency as the climb rate improves.
The descending sound is a steady tone that decreases in pitch as the sink rate increases.

The variometer should be equipped with a speed-to-fly ring.

Competition pilots will often equip their gliders with the newest of the electronic gadgetry.
Audio speed-to-fly directors and flight computers are very useful to reduce the mental workload on the competition pilot so the pilot can concentrate on tactics, flying accurately and where to fly next in search of the best lift.

★ Glide Path Computer
– Available as an additional to the speed indicator.
– It uses the pitot, static venturi information from the direction as well as the Mccready setting and wing loading.
– When a distance is set, this information is computed to give a height required for that distance.
– As the distance is flown it reduces this (from the pitot / static information) and re-calicurating the height continuously.
– When a thermal is taken it must be switched from cruise to climb mode, the computer ignores the forward speed of the sailplane and allows for the wind drift.
– They are most useful in a glide to a destination (final glide) when only sufficient height for a circuit is desired on reaching the goal.
– By using a check point half way along a leg, discrepancies between the planned distance and actual distance covered are rectified by adjusting the wind component.
– These instruments are very helpful in conditions where navigation is difficult.
★ G-Meter (Accelerometer)
– To show what G load are being applied to the glider.
– A useful education aid for the teaching of aerobatics.
– It is not mandatory, unless specified in the glider’s flight manual as minimum equipment for aerobatics.
★ Global Positioning System (GPS)
– A satellite based navigation system of extreme accuracy.
– As well as giving an accurate lat / long position, it can also give height if enough satellites are acquired by the unit.
– Use the navigation signal transmitted from series of satellites.
– GPS receiver determines its position in terms of longitude and latitude by knowing prices location of each satellites and accurately measuring the times of signal takes to travel to the receiver.
– A minimum of 3 satellites are required for lateral guidance, while 4 are needed for lateral and vertical guidance.
★ Gyroscopic Instruments
Attitude Indicator    Vacuum or Electronic
Heading Indicator        Vacuum or Electronic
Turn Coordinator        Electronic
– They are usually operated vacuum or electrically.
– By having different power sources individual gyros have back up information if one system fails.
– They are used to give steady indications of horizontal, bank angle, rate of turn and direction when a visual reference is not available, when in cloud.
○ The Primary Element of Each Gyroscopic Instrument.
– A heavily constructed spinning gyro amounted in ginbos.
– If the gyro is freely or universally amounted, it remain fixed position no matter where moved its base.
– The degree of stability is principle called “Rigidity in space”.
– Inside the instrument a rapidly spinning gyro tends to resist the external forces produced as the aircraft maneuver around it.
★ Attitude Indicator
– By having the gyro remaining relatively fixed position, the aircrafts attitude can be majors in relation to the gyro and will be displayed on instrument face.
– It receive power from vacuum system for powered aircraft.
○ Wrong indications
– If accelerated rapidly the instrument may indicate the slight climb.
– When decelerate rapidly there the initial indication is that slightly descend.
★ Heading Indicator
– The spinning gyro on the heading indicator is aligned with vertical plane, allowing it to sense any changes airplane vertical axis.
– It receive  power from the vacuum system for powered aircraft.
○ Very Suspect-able To Gyroscopic Precession
– As maneuver the airplane the external forces acting on the gyro cause the heading to drift very slowly.
– Need to periodically realign it with the magnetic compass. – Every 15 minutes.
★ Vacuum or Suction Gauge
– Normally position on the instrument panel to allow to monitor the vacuum pressure.
– If the pressure is not on adequate level, the gyro instruments could be unreliable.
★ Turn Coordinator
– Incorporates principle called precession.
– Whenever aircrafts attitude changes the pressure is existed by external forces tend to make the gyros changed aircraft rotation or precession.
– The faster the change, the greater the pressures, therefore precession.
– Majors the precession of its gyro, and indicates the rate of turn.
– Uses electrical power.
● RADIO NAVIGATION
★ VOR – Very high frequency Omni-directional Range                  1-2-3
– Give an accurate position of the aircraft in relation to the station.
– OBS – Omni Bearing Selector
– CDI – Course Deviation Indicator
○ Distance Off Course

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– Number of dots x 200’ft x Distance from the station
– Distance off course (feet) / 600 (Nautical Miles)
○ Time to the station
– 60min x Minutes Flown / Degrees of bearing change
○ ILS Indicator – Instrument Landing System

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When you drift to left and above the course
↓
To return to proper approach path, you need to turn right and descent.
– The combination of localizer and glide slope.
– Around to visualize your position along the final approach path.
★ HSI – Horizontal Situation Indicator

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– Combination of the heading indicator and the VOR.
★ DME – Distance Measuring Equipment

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– A signal delay in time is measured in nautical miles from the station.
○ Construction
◎ Monocoque
– The skin carries all loads and becomes the only structure, is capable of being molded to accurate tolerances and superb finish.
– An increase in performance that may only be achieved in wood or metal structures at much greater expense.
★ Three Forces
– In steady flight, the total reaction force balances the weight.
– The point about which the sailplane would balance is called the center of gravity designed to be close to same point at which the total lift force acts ; the center of pressure.
– Naturally different pilot weights, and different airspeed, will cause small changes in the position of these two centers.
– The sailplane is designed so that the center of gravity is always ahead of the center of pressure.
– The tail-plane is designed to make a small down load which can be varied to achive a balance at different weights and speeds.
★ ADF – Automatic Directional Finder
– Needle in aircraft points to NDB station.
– NDB – Non Directional Beacon.
○ Magnetic Bearing “TO” the station – MBTS
– Magnetic heading (MH) + Relative Bearing (RB)
○ Magnetic Bearing “FROM” the station.
– MB to the station (MBTS) – 180Deg.
★ RMI- Radio Magnetic Indicator
– Needle in aircraft point to VOR station.
○ Time
– Minutes x 60 / Degrees
○ Distance
– Minutes x TAS / Degrees

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★ Pitot – Static Instruments

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○ Airspeed Indicator

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○ Altimeter

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○ Vertical Speed Indicator

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★ Gyroscopic Instruments

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○ Attitude Indicator

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○ Heading Indicator & Magnetic Compass

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○ Turn Coordinator

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★ Engine Instruments

○ Tachometer

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○ Oil Pressure & Temperature Gauge

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○ Cylinder Head Temperature Gauge

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○ Manifold Pressure Gauge & Fuel Flow Indicator

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○ Engine Gas Temperature Gauge (EGT)

★ Electrical Instruments

○ Fuel Quantity Gauge

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○ Ammeter

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★ NAV Instruments

○ Basic VOR Indicator

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○ Horizontal Situation Indicator

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○ Radio Magnetic Indicator

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