17. When should a Direct Indicating Compass be “swung”?

[Cron]

When should a Direct Indicating Compass be “swung”?

I have information stating 'change of mag lat' and 'lightning strike' but would appreciate more information. Humorous reasons also welcomed. Thanks in advance.

[fireflybob]

I guess the relevant maintenance schedules will list the occasions when a direct reading compass must be reswung but a few spring to mind:-

Whenever there is a significant change in a/c components which might affect deviation - eg new wing etc!

At certain calendar periods (two years ?)

Whenever the correct operation of the compass is in doubt - pilot report in tech log?

Hope this helps a little

[oxford blue]

The full list which we teach is:

a when compass componenets are installed or replaced

b whenever the accuracy of the compass is in doubt

c after a maintenance inspection, if required by the schedule

d after a significant aircraft modification, repair or replacement involving magnetic material

e when carrying unusual ferromagnetic payloads

f when the compass has bee exposed to significant shock (heavy landing?)

g if the aircraft has been struck by lightning!

h after significant modifications to the aircraft radio or electrical system

i if the aircraft has been in long term storage standing on one heading

j if a change to a new theatre of operations involves a large change of magnetic latitude (though quite honestly, I don't think this one has much application in practice - after all they don't re-swing an aircraft compass on every turn-round on long-haul from UK to Singapore and back!)