# Aircraft Gyros in ships



## R.Philip Griffin (Jan 16, 2006)

I first put this in the Shaw Savill block-silly me.When I was deep sea and in charge of the gyro[Sperry] it required 8-10 hours to settle and was generally a pain in the ginger. When I started offshore and travelled by helicopter, the gyro started when the pilot switched on the engines, and ten minutes later were relying on that gyro for direction to destination.
My query is, have the powers that be ever put aircraft gyros into merchant ships, and if not why not. Perhaps they are too light for continuous running. Perhaps someone could inform of a] are they in Merchant ships and b] the reasons why not.


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## athinai (Jan 18, 2006)

I sailed in the MN and also learned to Fly in the early 60s. I remember the Ships Gyro gave true headings while the Main Standard Magnetic Compass gave Magnetic headings, the latter requiring the application of errors such as Variation and Deviation etc., I am fairly sure the Aircraft Gyro compass was only a Glorified magnetic compass with Gyro Stability such that it settled down fairly quickly to the magnetic heading. Hence the Runways at all Airports continue to have the Magnetic headings painted on their Tresholds etc.,
and are named accordingly., And all Aircraft Airways (Lanes) are Magnetic headings. Best of Luck,


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## Allan Wareing (Apr 23, 2006)

*gyros*



R.Philip Griffin said:


> I first put this in the Shaw Savill block-silly me.When I was deep sea and in charge of the gyro[Sperry] it required 8-10 hours to settle and was generally a pain in the ginger. When I started offshore and travelled by helicopter, the gyro started when the pilot switched on the engines, and ten minutes later were relying on that gyro for direction to destination.
> My query is, have the powers that be ever put aircraft gyros into merchant ships, and if not why not. Perhaps they are too light for continuous running. Perhaps someone could inform of a] are they in Merchant ships and b] the reasons why not.


Philip, When I was 2nd mate in Joe Shell the sent me on a one week course to Sperry,s Works where , amongst other things, I learned how to settle the compass down on the correct heading using a bit of juditious pressure in the appropriate positions on the rotor case to reduce the "hunting time" whilst still alongside before sailing. It was a long time ago (1950's) but I would think that if it was taking 8 hours to settle down you must have had a sick compass. Regards Allan.
p.s. In the 1960's I had some experience with an Admiralty Pattern A.G.M.C.5 which was a gyro-stabilised magnetic compass which was ok but not as good as the real thing.


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## mikeg (Aug 24, 2006)

I recall some Auto Steering electronics on one ship (16 years ago) that incorporated a small gyro that ran on air bearings, it stabilised virtually as soon as it had reach full speed at about 20 seconds. The gyro was driven by instrument air suitably filtered and dehumidified.
Regarding aircraft gyro's I suspect with inertial nav systems they settle down in moments rather than hours.

Mike


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## slick (Mar 31, 2006)

All,
Wasn't the ARMA-BROWN Gyro developed from something out of a Thor Missile?
Yours aye,
Slick


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## K urgess (Aug 14, 2006)

Athinai has it about right.
Free spinning gyros point to a fixed point in space not north.
All gyro compasses are gyros which are constantly monitored and adjusted.
In aircraft the earth's magnetic field is used which makes them magnetic compasses with all the corrections needing to be applied. This is because of speeds and acceleration. Also the need to be used in very high and low latitudes.
A ships gyro compass is gravity controlled so, when settled, points at the true pole. Because a ship travels slowly and doesn't accelerate very fast all the various slow acting precession methods allow it to operate properly.
A ships gyro will take an awfully long time to settle on true north if it allowed to just find it's own way there. The thing to do is to point them in the right direction and apply latitude correction before starting. The limitations are that they don't work in high and low latitudes.
Most naval vessels capable of fast acceleration and speed plus the need to operate far north or south have magnetic controlled gyros. So do tanks with gyro controlled guns.
The gyro used on blind flying panels in aircraft during WW2 was a vacuum spun free spinning gyro. For those that don't know the blind flying panel was a standard fitting on all RAF aircraft from Tiger Moths to Lancasters and Halifaxes. It had an Airspeed Indicator, artificial horizon, turn and slip, altimeter, rate of climb and directional gyro. All the instruments were independent of the aircraft electrical supplies and powered by vacuum from an engine driven pump where necessary. The free spinning gyro will point at north when set in that direction but will wander over a period of 24 hours in a circle around north.
The Sperry Mk XIV was beast and huge; it had also been in use for about 40 years without too much change. Most ship's gyro compasses can trace their origins to Anschutz. Sperry visited the factory and then went home and started his own gyro company. Anschutz had help from Einstein in part of his gyro design.
In the '60s all gyro companies started to build miniature gyros and by the '70s the monsters like the Mk14 had been replaced by table top models such as the Arma Brown unit in the background of this photo -
http://www.shipsnostalgia.com/gallery/showphoto.php/photo/49171/cat/500/ppuser/8196
This was mostly done by using the suspension tank as one of the supports for the gyro and incorporating the primary gimbal into the gyro ball itself. They also started using induction loops to transfer power to the gyro ball motor instead of slip rings etc.
Lesson over.(Whaaa) 
Sorry about that. I tried to answer it for my own interest and ended up trying to understand college notes from 35 years ago and "the Ship's Compass" by Grant and Klinkert. Still don't understand a word of it but at least I now know the general differences between the gyros.
Since I've now got a headache I thought I'd share.[=P]
If anyone wants any more do a search on gyro and there's a picture of a Sperry here - http://www.shipsnostalgia.com/gallery/showphoto.php/photo/45674/si/gyro/what/allfields


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## Binnacle (Jul 22, 2005)

Further to Marconi Sahib's interesting post, the following practical details come to mind. Prior to switching on the Brown's gyro the "latitude rider" would be set to the mid lat position if on an ocean passage. The compass would be manually precessed to within about five degrees of the true heading, this reduced settling time. Brown's handbook required the compass to be cleaned after three weeks running time. Slip rinngs would be cleaned and mercury changed. If on passage say UK/NZ this would be done after clearing Panama. Looking after the gyro, to me, was a labour of love. Browns called their compass an instrument and Sperry was a machine (all same Bendix). One had to hold a wet finger up to the air jet from the main rotor to check if it was okay, this controlled the repeater system. The Browns ran from a 24 v battery supply. The Arma Brown required no shipboard servicing, was precessed to the near heading by controls and in high lats the N. seeking element could be switched to direction pointing. If the bridge windows etc were open in Arctic fog etc the early models positioned on the bridge had to be wrapped in expanded paper to insulate them from the cold as the Low Temp warning light would come on. We were told they were fitted on Nato tanks but one I was with packed up after a good rattle full astern while shifting ship.


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## K urgess (Aug 14, 2006)

I've just realised that some of my post doesn't make much sense. What are high and low latitudes? (Rhetorical question) What I meant to say was just high latitudes north and south. 
Oh well, never mind.(Smoke) 
I've noticed that I haven't made a note of the gyro types on various ships until becoming responsible for them as Electronics General Dogsbody. Quite happy to leave it to the 2nd mate before that. I do remember the 2nd mate being quite anxious about it working again after a shutdown for maintenance in Panama. Seems to have been a convenient place for a clean up.
I seem to remember that the later "miniature" ship's gyro compasses couldn't fall over like the "Bendix" (nice allusion, Binnacle) giants because of the suspension system.


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## R.Philip Griffin (Jan 16, 2006)

Ahoy Alan and Marconi Sahib, Many thanks for your comments on this subject. I did discover the "pressure on the pots" to precess? was that the word, for a quick settling period. However, I don't think I have ever heard of gyro stabalised magnetic compass. Very interesting, also answers my original question of why aircraft gyros are not used in Merchant ships. Thank you for your answers.


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