IR – Instrument Rating

IR stands for Instrument Rating and is our abilitation to operate without visual reference (mandatory for airline operations).
Here are a few tips concerning it.

Documents courtesy Amaury-de-la-Grange FTO

Index

Changing radial using 90° interception

With the turn:

4. Description

4.1 General method:

• Changing radial using the 90° interception method where the angular difference between the two radials is 30° to 60°.
• Intercepting the desired radial at 90°.

Example:

– Visualizing the example on the ADI

1. Visualize the radial to be intercepted
2. Visualize the current radial
3. Visualize the turn direction and the approximate TRK (m) (010 – 020)

4.2 In practice:

1-> Visualization and projection onto ADI
2-> Direction of turn
3-> TRK (m) / HDG (m)
4-> When established on heading: set the navigation instrument for the desired track and crosscheck
5-> Calculate T2 and the anticipation 20/T2′

6-> Add the effect of wind during the turn to the anticipation
7-> Calculate the next HDG (m)
8-> At the end of the intercepting turn and with wings level: start inbound timing using T2′-20″ (no wind)

Change of radial: 30°/40° Method

1. Introduction

30°/40° radial changes are aimed at optimising the flight path time for a procedure (required by pilot or ATC).

2. Objective

To be able to line up quickly on a reference radial while approaching overhead station.

3. Description

Overview: (angular difference of 20° to 60°)

1. Visualise where the aircraft is going
2. Visualise current position
3. Turn direction and calculation of magnetic track
4. Visualise the next radial 10° further along
5. Calculate next heading (if left turn then closing turn will be to the right and vice versa…)

Example:

Aircraft is currently on inbound radial 180, intercept inbound radial 240. Call out: “INTERCEPT INBOUND RADIAL USING 30°/40° METHOD”.
Left turn to approximate heading of 330°.

Detailed description:

30°/40° METHOD (for an optimum flight path in terms of time at three minutes before the station)

IF OPENING TURN INTO THE WIND
δ=X, 2/3 X, X/3

The calculation should be made on crossing each radial.

Key Points:

• Visualisation
• Direction of opening turn
• Heading stable, calculation of next track
• For δ use X, 2/3 X, X/3
• Integrate the wind factor throughout the manoeuvre and joining turn towards the desired track.

Common Errors:

• Bad visualisation
• Same calculation used for next radial
• Direction change too soon/late
• Drift calculation too long
• Bad anticipation, at the end of the exercise the 10° value is often incorrect due to wind
• Remember safety altitude which may vary during the radial change procedure.

Racetracks

Example:

Call-out: “RACETRACK OR HOLDING PATTERN ON INBOUND RADIAL 270, RIGHT TURN, OUTBOUND TIME 1 MINUTE”.

– Visualizing the example on the ADI

1. Visualize where the aircraft is going
2. Visualize where the aircraft is
3. Direction of turn and magnetic heading

Execution and verification of racetrack or holding pattern:

Know how to calculate rapidly (3 radials, the “skeleton” of the racetrack)

Aa: Anticipation angle
Ca: Check angle

1. Abeam QDM: is perpendicular to the track (using the needle arrowhead)
2. Check radial (Cr): calculation method 40/T (with the tail of the needle)

Outbound Time	1′	1’30’	2’00	2’30	3’00
Ca	40°	25°	20°	15°	10°
Aa	20°	12°	10°	5°	5°

3. Position verification radial calculated using the 20/T method
   • Verified using the parallel magnetic track
   • Verified using the needle arrowhead.

– Visualizing further the example on the ADI

Racetrack on inbound radial 270, right turn, outbound time 1 minute (no wind).

Method without wind:

1. Aircraft stabilize on heading: start timer
2. If the abeam point has not been passed: re-start timer when passing abeam QDM
3. Interception of position check radial (Cr)
4. Once at the perpendicular heading, verify position using 20/T
5. 30° before final heading, make a final verification

Using the ADI scheme:

1. **none**
2. Abeam QDM: QDM 360°
3. Check radial (Cr): 270 – 40 = 230
4. QDM 20/T is 090 – 20 = 70

Entry sectors:

Four entry sectors are defined and each sector has an associated flight path.
The manoeuvre begins when the aircraft passes overhead the holding fix.

• SECTOR 1 = Parallel entry
• SECTOR 2 = Offset entry
• SECTOR 3 = Direct entry
• SECTOR 4 = Special 90° entry

Note: Sectors 1 – 2 and 3 are ICAO recommendations.
Sector 4 is a special procedure used by the operator (France only)

Parallel Entry:

When overhead the fix, start the timer and turn to take the reciprocal magnetic track to the inbound track for the racetrack of holding pattern and maintain this heading for:

Te =

• 1 min if tailwind or no wind
• 1 min 30 seconds if headwind

Turn at 25° of bank in the opposite direction to the flight path specified in order to join the inbound track.

Note:
Te = Outbound time
Tec = Corrected outbound time

Offset Entry:

When overhead the fix, start timer and set the heading which will allow a flight path to be followed for one minute which is at an angle of 45° to the inbound track on the racetrack or holding pattern side, then follow the parallel track for the planned time or for the specified time minus one minute.

With wind: the opening 45° turn will be modified by the drift δ of the racetrack or holding pattern track.

Time correction:

• if heading away from the crosswind then correct using 1′-δ” for the track
• if heading into the crosswind then correct using 2δ” for the track.

Direct Entry:

When overhead fix, start timer to carry out a turn in the specified direction in order to follow the outbound track for the planned time (holding pattern) or for an imposed distance (racetrack procedure) then turn in the specified direction to line up on the inbound track.

Special 90° Entry:

When the aircraft arrives in the 40° sector defined on the scheme on your right, the alteration of heading will be so large in direct entry that the quality of the outbound leg will be compromised by the reduction in the turn diameter.

A special 90° (direct) entry has been defined.

When overhead fix, start timer and follow a track perpendicular to the specified inbound track for 20 seconds. Turn in the specified direction to follow the outbound magnetic track for the planned time of 20 seconds (holding pattern procedure or for the imposed distance (racetrack procedure), then turn to line up on the inbound track.

4. Key Points

Organisation of workload:

• visualization of position
• Turn direction for holding or racetrack pattern
• Magnetic track/magnetic heading
• Calculation of abeam QDM
• Calculation of check radial (Cr) 40/T
• Calculation of anticipation radial 20/T
• Calculation of magnetic heading with alignment on track if necessary

5. Common Errors

• Bad visualization of position –> causes wrong entry type to be used
• Slow calculations
• Not respecting the verifications (abeam, lead radial)
• Forgetting the 1st or 2nd turn will be into the wind
• No verifications during 2nd turn

How to – use a VOR/HSI/ADF

source: Tim B. Carlson

Useful Formulae

Abbreviations

Simplified formulae

Ve = Groundspeed – TAS
Vt = δ x TAS (NM/min)
X = Vw . Bf

*Note: simplified calculation where no GPS or DME is available

TAS = IAS + 1% per 600 feet of altitude ± 1% for every 5% C difference from ISA

Note:

Anticipation

Interception Angle	120°	90°	60°	30°
Anticipation angle	30/T	20/T	10/T	2/T

Rapid join

te = 100 – α
tec (headwind) = (100 – α) + 2 Ve
tec (tailwind) = 100 – α

DME Arc

• Anticipation: D (NM) = Groundspeed/200
• Anticipation for final approach interception: A° = TAS/3D or 20/T

Racetrack (check radial and anticipation angle)

• *Ca = Check angle
• *Aa = Anticipation angle

Entry type	Outbound time Tec	Inbound time T (1)	Turn	20/T
Direct	Headwind: Vw = T + (T+1) Ve Tailwind: Vw = T – (T . Ve)	Headwind Vw = T + 1/2.Ve for every minute of T Tailwind Vw = T – 1/2.Ve for every minute of T	With headwind component: 3δ sec* 0 correction with tailwind component	+ 50% or 30/T with tailwind – 50% or 10/T if headwind
Perpendicular	Headwind: Vw = (T – 20″) + (T + 1) Ve Tailwind: Vw = (T-20″) – (T . Ve)		With headwind component: 20 sec ± 3 sec* 20 sec with tailwind component
Offset	Headwind: Vw = (T-1) + (T+1) Ve Tailwind: Vw = (T-1) – (T.Ve)		With headwind component: 1min + 2 sec 1min – δsec with tailwind component

NOTE:

• The product of (T-Ve) and (T+1) Ve is in seconds
• Ve, δ and δ sec on racetrack axis
• *if 3δ sec or 20 sec + 3δ sec > 30 sec then correct for drift

SNOWTAM DECODER

source: Sir Pat BOONE, Captain B737-B767 from www.b737mrg.net