FLYING ON INSTRUMENTS

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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Fri Oct 12, 2018 4:36 am

Orientation using the RBI
The aeroplane can be orientated with respect to the NDB if you know:
The magnetic heading (MH) of the aeroplane (from the compass or direction indicator); plus
The relative bearing (RB) of the NDB from the aeroplane.
In practice, magnetic heading is flown using the direction indicator, which should be realigned with the magnetic compass in steady flight every 10 minutes or so.

The Rotatable-Card ADF
The rotatable-card ADF is an advance on the fixed-card ADF, because it allows you to rotate the card so that the ADF needle indicates, not relative bearing, but magnetic bearing to the NDB. Do this by aligning the ADF card with the DI compass card each time the aeroplane’s magnetic heading is changed.
To align a rotatable-card ADF:
• Note magnetic heading on the direction indicator; then
• Rotate the ADF card, setting magnetic heading under the index
When the ADF card is aligned with the DI, the ADF needle will indicate the magnetic bearing to the NDB. This eliminates any need for mental arithmetic. Note also that the tail of the needle, 180 degs removed from its head, indicates the magnetic bearing of the aeroplane from the NDB.
Any time the aircraft changes magnetic heading, you must manually align the ADF card with the DI (ensuring of course, that the DI is correctly aligned with the magnetic compass.
If desired, the rotatable card can still be used as a fixed card simply by aligning 000 with the nose of the aeroplane and not changing it. The next step up from a rotatable card is one that remains aligned automatically, a radio magnetic indicator (RMI)
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Sat Oct 13, 2018 1:29 am

The Radio Magnetic Indicator (RMI)
The RMI display has the ADF needle superimposed on a card that is continuously and automatically aligned with magnetic north. It is, if you like, an automatic version of the rotatable-card ADF – an automatic combination of the direction indicator and RBI.
The RMI is the best ADF presentation, and the easiest to use, but unfortunately the most expensive and usually only encountered in more sophisticated aircraft.
The RMI needle will always indicate the magnetic bearing to the NDB. The tail of the RMI needle will indicate the magnetic bearing from the NDB.
As an aeroplane turns and its magnetic heading alters, the RMI card (which automatically remains aligned with magnetic north) will appear to turn together with the ADF needle. In reality, of course, it is the compass card and the RMI needle that remain stationary, while the aeroplane turns about them. Before, during and after the turn, the RMI’s needle will constantly indicate the current magnetic bearing to the NDB.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Fri Oct 26, 2018 12:28 am

Dual Pointer ADF

Some aeroplanes are fitted with two ADF receivers, and have two needles superimposed on the one dial. Sometimes the indicator has a function switch that causes a needle to point, not at an NDB, but at a VOR ground station. This gives the pilot more flexibility in using radio navigation aids.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Fri Oct 26, 2018 12:42 am

THE RELATIVE BEARING INDICATOR (RBI)

Operational Use of the RBI – Orientation, using the RBI to Obtain a Position Line
A position line is a line along which the aeroplane is known to be at a particular moment. A position line (PL) is also referred to as a line of position (LoP). A position line may be obtained by a pilot either visually, or by radio means.

Two position lines that cut at a reasonable angle are needed for a fix. For the aeroplane to be on both position lines simultaneously, it must be at a point of intersection. It is possible to fix position using a combination of radio aids including ADF/NDB, VOR and DME.
A position line can be considered from two perspectives:
From the aeroplane, i.e., the position line from the aeroplane to the NDB that a pilot would see, as either a relative bearing (RB) or a magnetic bearing to the station (known in the UK as a (QDM); or
From the NDB ground station (which is necessary if the aeroplane’s position is to be plotted on a chart) as either a magnetic bearing from the station (known in UK as a (QDR) or a true bearing from the station (known in the Q-code as QTE).
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Tue Dec 11, 2018 4:39 am

Sorry for not being around for a while. I misplaced some of my notes when moving and, some of my scribbles I could not understand (as bad as my typing LOL). Anyway, I am back and hope to continue my thoughts on radio navigation and instrument flying. I am not a journalist so bear with me when I transcribe my notes into readable text. And, also, I may sometimes slip into my British mode when trying to describe some elements of my techniques and charts.

True Bearings from an NDB
Normally when instrument flying, you would not bother to plot positions on a chart. However, if like me, you decide to do so, then the easiest method on a visual chart is to use true bearings from a ground station, i.e., bearings from a ground station related to true north (as indicated on the chart by the meridians of longitude)
Intercepting a track
Having orientated yourself with respect to an NDB, you know the answer to the question “Where am I?” Now ask “Where do I want to go”? and “How do I get there?”
STEP1 - Is always to orientate the aeroplane relative to the NDB, and to the desired track.
STEP2 – involves a turn to take up a suitable intercept heading, considering where it is that you want to join the track.
STEP3 – involves maintaining the intercept heading and waiting:
• For the head of the needle to fall if inbound;
• For the tail of the needle to rise if outbound:
• To + or – 030 for a 30 deg intercept;
• To + or – 045 for a 45 deg intercept
• To + or – 060 for a 60 deg intercept
• To + or – 090 for a 90 deg intercept
STEP4 – involves a turn onto the desired track and allowing for a suitable wind correction angle to maintain it.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Tue Dec 25, 2018 2:57 am

Visualising where you are, and where you want to go
The direction indicator (DI) can assist greatly in visualising the situation. All you need to do is visualise the desired track on the DI. With a model aeroplane on the tail of the needle tracking as desired, it becomes quite clear what turns are necessary to intercept a desired track.

If you become disorientated, a simple procedure is to take up the heading of the desired track. Even though not on track, the aeroplane will at least be parallel to it, and the ADF needle will indicate which way to turn to intercept it.

TRACKING
Tracking inbound to an NDB
The ADF/NDB combination is often used to provide guidance for an aeroplane from a distant position to a position overhead the NDB ground position. This is known as tracking. Just how you achieve this depends to a certain extent on the wind direction and speed, since an aeroplane initially pointing directly at the NDB will be blown off course by a crosswind.
Tracking towards an NDB, with no crosswind effect
With no crosswind, a direct track inbound can be achieved with a heading that maintains the ADF needle on the nose of the aeroplane.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Mon Jan 07, 2019 4:49 am

The Radio Magnetic Indicator (RMI)
The RMI combines the relative bearing indicator and direction indicator into one instrument, where the ADF card is aligned automatically with magnetic north. This considerably reduces pilot workload by reducing the amount of visualisation and mental arithmetic required. Even the rotatable card (which allows you to align the ADF card manually with magnetic north) lightens the workload, since it also reduces the amount of visualisation and mental arithmetic required.
The discussion that follows applies to both the RMI and the rotatable-card ADF, except whereas;
The RMI is continuously and automatically aligned with magnetic north;
The rotatable card must be re-aligned with the DI by hand following every heading change (and of course the DI must be re-aligned with the magnetic compass by hand every 10 minutes or so).
Orientation
An RMI gives a graphic picture of where the aeroplane is:
• The head of the RMI needle displays QDM (magnetic track to the NDB): and
• The tail of the RMI needle displays QDR (magnetic track from the NDB
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Mon Jan 21, 2019 1:37 am

VISUAL MANOEUVRING - IFR, Instrument flying

I want to skip ahead a little bit and discuss the above subject and introduce the basic reasoning for a circle to land scenario.

If the final approach direction of an instrument procedure does not align the aeroplane within + or – 30 degs of the landing runway, or position it suitably so that a reasonable flightpath to the touch-down point can be achieved comfortably, then it is technically no longer a straight-in procedure, and significant visual manoeuvring (probably involving at least a partial circuit) will be required to align the aeroplane with the landing runway.

Visual manoeuvring is also known as circling, or as a circle-to-land manoeuvre, and these terms are used to describe the visual phase of flight after completing an instrument approach, with the aim of manoeuvring an aircraft into position for a landing on a runway which is not suitably located for a straight-in approach.

The most common use of visual manoeuvring is after becoming visual at or above the circle-to-land minimum following an instrument approach based on an out-of-wind runway, and then manoeuvring visually for a landing on the into-wind runway, e.g. Using Runway 27 ILS to become visual, followed by a circling approach and landing on Runway 09.

The flightpath that you choose to fly will vary depending on the situation – for instance, you might choose to circle in a direction that avoids high terrain, low cloud, a heavy shower, etc.

A circling approach is a more difficult manoeuvre than a straight-in approach, because it often involves close-in manoeuvring under a low cloud base and in rain or poor visibility. It will require precise attitude flying, with close attention to maintaining height, while flying a suitable flightpath to position the aeroplane for a landing and keeping a very good lookout.

The circle-to-land MDH for a particular approach procedure that is aligned with a runway will generally be higher than the straight-in DH.


……………………..more to come
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Wed Jan 30, 2019 1:07 am

The Visual Circling Manoeuvre

If you become visual at or above the minimum descent height for the instrument approach, then you should maintain this height until within the circling area. When within the circling area, and remaining visual, you may fly at the visual manoeuvring obstacle clearance height (which at some aerodromes is lower than the MDH for the instrument approach). The visual manoeuvring obstacle clearance height may be referred to as the visual manoeuvring OCH, the circling height, or the visual manoeuvring height (VMH).

A circling approach is a visual flight manoeuvre, and you must remain visual throughout, otherwise a missed approach is to be carried out.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Fri Feb 01, 2019 2:34 am

Each circling situation is different because of variable such as:
The final approach direction of the instrument approach
The runway layout
Wind direction and speed, and the selected runway for landing
Local terrain
• Meteorological conditions (especially cloud base and visibility)

For instance, wind direction and strength usually determine which runway should be used for landing. Cloud base usually determines what circuit height (at or above visual manoeuvring OCH) is flown. If there is a fog bank on one side of the aerodrome, then a circling approach on the other side of the aerodrome in good visibility is preferable, irrespective of whether a left or right circuit is involved.

Generally , though, it is advisable to follow the normal circuit pattern, which at most aerodromes is left-handed to provide the captain in the left seat with a good view of the runway, and at the usual 1,000 ft. aal. Should the cloud be lower, a circling approach is legal at heights down to the visual manoeuvring OCH.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Tue Feb 05, 2019 2:09 am

TIP
"Keep your circle-to-land approach as close to a normal circuit as the conditions permit".

The term circling does not imply that the visual manoeuvring should follow a circular pattern, but rather that the circuit pattern should be adjusted to suit the conditions. As a general rule, circling should be as close to a normal circuit as conditions allow. This helps other traffic in the circuit, as well as ATC, and keeps things as standard as possible for the pilot.

If, for instance, you become visual at 2000 ft. aal on the instrument approach, well above the permitted minimum, then you should continue descent to normal circuit height and fly a normal circuit, rather than descend to the visual manoeuvring obstacle clearance height, which may be as low as 400 ft. aal. While training (if you are receiving VATSIM supported supervision) however, your instructor may ask you to fly a circuit assuming a particular cloud base, even though actual conditions do not require it.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Tue Feb 05, 2019 7:54 am

HOT TIP :teach:


“Control your attitude (don’t get angry or upset – :lol: just joking), airspeed and altitude carefully during a circle-to-land approach.

Good attitude control is essential in the circling manoeuvre, with bank angle limited to 20 degs or rate 1 (maximum 30 degs), altitude maintained at or above visual manoeuvring obstacle clearance height, and airspeed as desired. The aeroplane must also be configured for landing (with the landing gear and flaps extended as required), and all checks completed, before the landing is made.

A well-flown circling approach is the sign of a competent pilot. :banjo:
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Wed Feb 06, 2019 3:48 am

Descent below the Visual Manoeuvring Height

Descent below the visual manoeuvring obstacle clearance height should not be made until:
• Visual reference with the aerodrome environment is established and maintained;
• The landing threshold is in sight; and
• The required obstacle clearance can be maintained on approach and the aeroplane is in a position to carry out a landing.

TIP
The most appropriate time to commence the descent from the visual manoeuvring OCH for a landing is when the normal landing descent profile is intercepted.

The lower the circling height, the closer this will be to the aerodrome. If, for instance, the aeroplane is circling at the lowest permissible visual manoeuvring OCH at an aerodrome with no obstacles (which is 400ft aal), the landing descent will not be commenced until on final. For higher visual manoeuvring OCHs, the descent for a landing may be commenced earlier to avoid unnecessarily high descent rates on final.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Fri Apr 19, 2019 4:05 am

Pilot Initiative and Judgement is Required

It is impossible to design a single procedure that will cater for all situations – this is an area for pilot judgment and decision. Because the circling manoeuvre may have to be carried out in poor conditions, you must be able to make firm decisions quickly. This ability will come with experience and good planning. The basic assumption in circling approaches is that, after initial visual contact, the runway environment (the runway, the runway threshold or approach lighting aids, or other markings identifiable with the runway) should be kept in sight while manoeuvring in the circuit at or above the visual manoeuvring height.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Sun Apr 21, 2019 10:33 am

CLOUD BASE
The actual height to be flown while manoeuvring in the circling area will be governed by the visual manoeuvring obstacle clearance height and the cloud ceiling. It is unusual for a cloud base to be perfectly flat; normally it is rather “furry” or “lumpy”, and fluctuates in height. For this reason, it is recommended that a gap of at least 200 ft exist between aeroplane (flying at visual manoeuvring height or higher) and the estimated cloud base. This gap is impossible to measure accurately, of course, so it requires realistic estimation by the pilot, who must:
Remain visual: and
Not descend below the visual manoeuvring obstacle clearance height until in a position for a safe descent for landing.
If, for example, the visual manoeuvring OCH published for a particular aerodrome is 550 ft aal, then you know, seeing a forecast cloud base of 800ft aal, that you will probably be operating in marginal conditions where 200 ft above the circling OCH may or may not exist. You must not circle at a lower height than the visual manoeuvring OCH, no matter what the cloud does. Your way out, of course, is a missed approach.
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