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[Mohit_C]

Hi,

I am a little confused on how to tackle the following question. It's actually from Operational Procedures. Could someone give me a step by step solution to this?

An aircraft leaves point P (60°N 030°W) on a true
heading equal to 090° while the gyro compass, which is
assumed to be operating perfecly and without an hourly
rate corrector unit, indicates 000°.
The aircraft arrives at point Q (62°N 010°W) on a true
heading equal to 095°. On the journey from P to Q the
gyro compass remains in free gyro mode.
If the flight lasted 1 hour 30 minutes, the gyro heading at
Q will be :

A) 345°.
B) 003°.
C) 334°.
D) 328°.

Thanks.

[jamie230985]

Hey,

This question assumes that you are following an E - W track therefore the change in where your gyro compass is indicating is due to convergance.

Convergancy:

The change in direction along an E - W track as a result of the way direction is measured as a result of the converging meridians at the poles. The change in direction experienced between two points is know as convergency.

sorry I cant help u any more but if u look this up in your textbooks it should give you a formula!!

[Mohit_C]

Hiya,

I'm unsure what you mention about convergency. I was thinking along the lines of the precession, i.e. apparent and transport precession. As far as I know, the convergency, difference between initial and final headings apply to an ortodromic route but this question says "constant gyro heading" so I would assume it's talking about a loxodromic route.

[SW1]

Refer to your notes pages 9.1/9.2/9.3
3 types of error:

Earth Rate = 15 x sin lat (this is a rate of error)
Therefore:
Amount of Earth Rate Error = 15 sin lat x Flight time

Latitude Nut = 15 x sin lat (this is a rate of error)
Therefore:
Amount of Lat Nut error = 15 sin lat x Flight time

A correctly set latitude nut corrects for earth rate (look at the +/- table on page 9.3)

Transport wander = Degrees of longitude travelled x sin lat

For this question....no hourly correction has been set....ie no latitude nut correction....so we need to calculate Earth Rate and Transport Wander.

Earth Rate = 15 x sin 61 x 1.5 = 20

Transport wander = 20 x sin 61 = 17

Looking at the +/- table, both these errors are minus errors, so total error is -37.

We start with 090T, 000Gyro
We finish with 095T, so with no error we would expect 005Gyro
However, we have -37 of error, (005 - 37) = 328.

[Mohit_C]

Thanks SW1, that does make sense.:ok: