Compass Swings for Helicopters?
 

On the General Aviation & Questions thread there has been discussion about compass swings and what the regulations are in various countries - see HERE.

It’s claimed that in New Zealand a compass must be swung every twenty-four months. Can anyone advise if this also applies to a VFR helicopter? And does that mean the helicopter must be put into the air and hovered whilst the measurements are taken and that this must be performed every twenty-four months even if it is obvious that the compass has no faults and is accurate?

Usually it is done on the ground using its wheels, tow cart, etc... It is measured using another calibrated compass.

Here in the southie it is just like that

African procedure: Pickup. Turn. Setdown. Pickup. Turn. Setdown. Pickup. Turn. Setdown. Some 12-16 times. Great crosswind training for new pilots. :rolleyes:

It has to be done with rotors turning and the usual electrical load, so ground wheels and tow cart would be the exception.

Pick up, turn a smidgin, put it down. or on wheels, roll around a bit, stop. But it needs to be in an area free from external electrical fields, so doing it on a taxiway for example might pick up some errors from lighting cables.

The junior bograts were usually chosen, they could log command time, half of the engine time. The engineer with the Wild Datum Compass got a lot of walking time trotting around behind the machine to line up the reference points, take the reading, trot back into pilot's view, signal the next move, etc.

I did my first ones at Fleetlands in 1979. Been doing them ever since when required, last one done last year.

Procedure is as described by Hawkeye and Ascend Charlie.

Definitely without a towcart, that would have it's own magnetic field which would cause unknown errors.

Have to agree with Ascend Charlie & Shy Torque

When I was a bograt:{ and even up until I joined offshore, I spent countless times doing compass swings in machines at Bankstown airport and elsewhere.

They actually had a compass swing area near the main pad at Bankstown for those that flew there such as Ascend Charlie.

These were done engines running with the ginger beer and his compass thingy pointed at us when we gave him the thumbs up, but we used to have to keep it light on the skids on compass heading each time.:ok:

In the US it has to be done with engine(s) running, normal electrical load, battery charged. Charging the battery, turning on landing lights, etc all affect the compass, some by more than 30 degrees. I usually let the person on the ground stay in one place, and move the helicopter around him, since that's quicker and easier. I'm not trying to log extra time so I can get a real job any more. Once I passed 10k hours, I decided it wasn't possible. :rolleyes:

When I was on exchange at Boscombe Down, and we were doing a lot of Doppler testing, compass swings were done to a gnat's whisker of precision. This was necessary to know what was affecting the accuracy of the nav system. THree hour compass swings were not uncommon in the test Sea King - rotors running, all systems up.
A couple of years later I'm at Pax River and watch the USN do compass swings on their H-3s with blades folded and no engines on, and they wondered why their Doppler nav systems never were very accurate....

I always aimed for numbers like 135, 180, 225 etc. call me anal but that's what I landed on, not 136, 182...,,,,

To get back to Mr Smith's original gripe it seems he is miffed because somehow
the swing seems to be a special mission as it is out of phase with the rest of
his maintenance and he has had to go out of his way to do it.

Do it on your annual or each 2nd annual inspection?

If it takes more than 10 minutes I would be surprised. 4 cardinal points is all you
need to "check" it.

If not split the difference on the cardinals, adjust accordingly, swing on the points
of the correction card, average the errors to give you the lubber error and then
write up the card. Doddle.

If the juice has leaked out replace the gasket and fill with Jet A-1 that has stood for
a while to get the bubbles out. Stoddard solvent, mineral spirits, kerosene is also OK.

Your poor cousins to the east of you allow any LAME or Commercial pilot for that matter to swing a compass.

These days in the current machine I just swing/check it off the AHRS!

The regulations say 24 months minimum but I would say that as your aircraft would have an approved schedule
and possibly IFR it could be 12 months and you are obliged to follow the most restrictive - results may vary.

And the aircraft needs to be running and away from magnetic interference hence the compass rose at most larger airports.

In case you wondered why the Jetbox/Longbox compass is on the RH doorpost ask yourself where the battery cables are and you
will realise why it is not mounted on the windscreen centre post.

Does a compass get out of whack over time? Yes depending on what it is subjected to - see above.
If parked near a large steel object, as in my case a large steel boat, then yes and it screws the fluxgate as well but not for long.

If this is such an important safety issue how come it is not a requirement in the USA?

The FAA only promulgates bare minimum requirements. Recurring compass swings are covered in the manufacturer's inspection requirements. For commercial operations, compass swings are certainly required, and I've done many of them, in many different aircraft. I've never spent time investigating the inspection requirements for aircraft flown solely under Part 91.

Dick,

Maybe its about time you got out more often - no disrespect but look here.

And if you follow your nose you will find the requirements are in the Instructions for Continuing Airworthiness
(read Maintenance Manual, Service Bulletins) as part of the issue of a Type Certificate.

As to why Australia promulgated an AD, who knows maybe it was to cover older aircraft without an adequate maintenance manual?
Maybe it was the only method available at the time.

But then again CASA is hell bent on living in the dark ages by the looks. They still re-issue manufacturers AD's FFS! What a waste of time.
Every other NAA has woken up and uses the AD's issued by the state of manufacture which these days are readily available.
Non specific and General AD's notwithstanding of course.

How's about you just bung a ZK on the tail and life would be so much easier because you can!!

AUS Needs to get over itself and its so-called uniqueness and has been drinking its own Koolaid for far too long.

Its called Globalisation ya know. Lets not get onto the cluster called Part 61! :p

Wow....a simple compass swing, heaven forbid its a good thing helicopters are a simple machine and easy to operate. A pilot with a compass rose, a brass or plastic screw driver and a pen or pencil can have a swing done in a 0.1 flight time.....,:rolleyes: