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Old 16-04-2019, 12:45   #16
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Re: AIS Military vessel alarm

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Originally Posted by AedanC View Post
All the Search and Rescue helicopters here in Ireland transmit AIS.


I wonder why?
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Old 16-04-2019, 12:52   #17
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Re: AIS Military vessel alarm

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I wonder why?
Pretty accurate position, COG and SOG information for those in CIC? AIS can be better than ARPA or a backup to ARPA, especially at greater distances. The US military has GPS units with no DOP, which can help in accuracy with COG as well. More accurate than radar azimuth and distance to a contact. They would be allowed to transmit their AIS at a greater power, giving them greater range than us civilians are allowed.
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Old 16-04-2019, 13:01   #18
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Re: AIS Military vessel alarm

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Originally Posted by a64pilot View Post
Iíve never heard of an aircraft transmitting AIS, itís possible of course, but wonder why one would?

Yep, happens. The ones I've seen are listed as SAR. Kind of weird, given their serious speed.

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Old 16-04-2019, 13:05   #19
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Re: AIS Military vessel alarm

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Originally Posted by AedanC View Post
All the Search and Rescue helicopters here in Ireland transmit AIS.
And you can even find them on Marine Traffic....

https://www.marinetraffic.com/en/ais...:SAR_250002897

https://www.marinetraffic.com/en/ais...:SAR_250002899
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Old 16-04-2019, 13:12   #20
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Re: AIS Military vessel alarm

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Originally Posted by a64pilot View Post
Iíve never heard of an aircraft transmitting AIS, itís possible of course, but wonder why one would?

Yes, they have their own type of AIS. My friend has a home-built kit plane with an AIS on it. I don't recall if it was the transceiver type or not. He gave me the impression that it is now an FAA requirement.
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Old 16-04-2019, 13:25   #21
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Re: AIS Military vessel alarm

Pilot transfer helos here on the East coast of Oz also transmit AIS as they shuttle back and forth to bulkers and oilers lying offshore. Kinda fun to watch on the display.

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Old 16-04-2019, 13:37   #22
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Re: AIS Military vessel alarm

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Originally Posted by Taipe View Post
Yes, they have their own type of AIS. My friend has a home-built kit plane with an AIS on it. I don't recall if it was the transceiver type or not. He gave me the impression that it is now an FAA requirement.
Very close, ADS-B is an FAA requirement as of 2020 in the US. ADS-B is a somewhat similar system to AIS in that it lets a pilot know the type, position, speed, COG, distance to, CPA and altitude of other aircraft in his area. It works differently from AIS but it does many of the same things.

https://en.wikipedia.org/wiki/Automa...0%93_broadcast
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Old 16-04-2019, 19:00   #23
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Re: AIS Military vessel alarm

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Originally Posted by jmschmidt View Post
US military vessels do not run their AIS equipment in transmit mode when operating on the open sea for obvious reasons.

It seems like I'm lacking the most basic understanding of the OP's question, since there were three or four responses saying "military vessel don't always transmit AIS"?



He mentioned that he could see the vessel on his AIS screen, just the alarm didn't go off.


And to answer that quesion, no, I have never heard of an AIS option in the sending device to suppress a CPA alarm on all the receivers.
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Old 16-04-2019, 22:28   #24
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Re: AIS Military vessel alarm

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Human beings are not nocturnal animals - we are genetically programmed to sleep when it gets dark. Shift workers, and people who live at high polar latitudes suffer various ailments when they have to be awake when it is dark.
Sorry here is some thread drift but I couldn't help but to express some mild disagreement with the quoted.

You must realize that it isn't fair to compare a few days or weeks, even, of night watches to years and years of constant night shift work in the stress of most any real job.
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Old 16-04-2019, 23:21   #25
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Re: AIS Military vessel alarm

Chinese Cargo ships rarely transmit in Philippine waters and do not care much about navigation rules anyway. In particular "a sailing vessel under sail is only a Fata Morgana", nice to see, but nothing to care about.
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Old 17-04-2019, 00:09   #26
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Re: AIS Military vessel alarm

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Originally Posted by a64pilot View Post
I wonder why?
Because it's very handy for the target, nearby coastguard vessel, and other assisting ships to know where the SAR helicopter is...
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Old 17-04-2019, 09:02   #27
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Re: AIS Military vessel alarm

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Originally Posted by BenBowSirocco View Post
It seems to me based on my study of solo sailing, (I hope to do some in the future) that the best time for a solo sailor to get sleep is in the daytime when your vessel is most visible to others and hazards are most visible to you.

Do you choose to rely on the nav equipment during your naps at night because that is when your accustomed to sleeping and have to sleep?
That's my method: sleep during the day - stand watch at night. And if I'm awoken because something goes wrong while I'm sleeping, it's far better to be dealing with the problem in daylight.

I worked for 10 years on the midnight-to-eight shift with no problems. I may be a statistical outlier in terms of adaptability. My biggest problem is coping with less than 5 hours of uninterrupted sleep or less than 7 hours sleep per day total.

There are a lot of myths in single-handing about sleep: the one I see most commonly is that people can survive for many days on just 20 minute naps. No, they can't - what those people are doing is sleeping unawares while sitting up. Getting substantially less than 5 hours of uninterrupted sleep causes real physiological harm and turns your mind into mush. Prolonged sleep deprivation causes permanent irreversible cognitive harm - in fact - it's considered to be a form of torture. Do some research on the topic outside of the myth-filled sailing forums and you'll find plenty of scientific data to back up that assertion. Just Google: "sleep myths."

I would never try sleeping with less than 50 miles of seaway in all directions.

After the USS Fitzgerald and McCain accidents, the US Navy is now broadcasting AIS in busy sea lanes. But they stop transmitting once they are out of the high traffic lanes. USCG vessels on patrol often discontinue transmitting AIS as well. And you can't count on Naval vessels to alter course - there're are jokes about US Naval vessels expecting bridges and islands to give way. There's some truth in those jokes.
https://youtu.be/KvRYd8U7qGY
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Old 17-04-2019, 09:25   #28
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Re: AIS Military vessel alarm

I'm guessing that it is unlikely for an AIS unit to have a "don't alarm Military Ship" mode. The reason is that the "need" for this is for the military to have a pseudo stealth mode but that would depend on the software in the AIS unit. And thus be easily defeated.

Running without transmitting and turning on when close sounds like a good possibility. Along with "sleeping through the alarm (is that likely?).

My own encounter with a naval vessel of note was with the John C Stennis on approach to the Straights of Juan de Fuca. The Stennis was transmitting AIS with the ship name of NVXX (I don't recall the number used(XX)).

We could see them 20+ nm out on AIS and on Radar. The CPA was something like 1/4 nm. With binocs it was obvious that they were an Aircraft Carrier and I was very nervous about getting anywhere close to a carrier. I just do not want to be on the threat list.

At 5 (or was it 10?) miles out they changed course and opened up the CPA to many miles.
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Old 17-04-2019, 09:28   #29
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Re: AIS Military vessel alarm

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Originally Posted by Cpt Pat View Post
That's my method: sleep during the day - stand watch at night. And if I'm awoken because something goes wrong while I'm sleeping, it's far better to be dealing with the problem in daylight.

I worked for 10 years on the midnight-to-eight shift with no problems. I may be a statistical outlier in terms of adaptability. My biggest problem is coping with less than 5 hours of uninterrupted sleep or less than 7 hours sleep per day total.

There are a lot of myths in single-handing about sleep: the one I see most commonly is that people can survive for many days on just 20 minute naps. No, they can't - what those people are doing is sleeping unawares while sitting up. Getting substantially less than 5 hours of uninterrupted sleep causes real physiological harm and turns your mind into mush. Prolonged sleep deprivation causes permanent irreversible cognitive harm - in fact - it's considered to be a form of torture. Do some research on the topic outside of the myth-filled sailing forums and you'll find plenty of scientific data to back up that assertion.
That is what Hal Roth stuck to fervently. Its also mentioned in "Single Handed Sailing" and a few other good sources.

Seemed very logical to me. I personally have never had much trouble with staying awake during my night watch (knock on wood!) despite certainly being sleep deprived during a couple passages. I find there is usually plenty to do- even staying warm can keep a person occupied!

There are some humans who have performed well on the "cat nap" system, but it does not work for everyone. My Grandfather currently only sleeps in snatches, 1/2 hour or so every 3 or 4 hours. But it didnt start until his mid-80's.

Commercial shipping insurance companies will tell you the number one reason for mistakes at sea is fatigue. So it seems more important to get proper sleep, than when/how you get it. I supposed everyone has to work that out for themselves.
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Old 17-04-2019, 09:33   #30
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Re: AIS Military vessel alarm

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My own encounter with a naval vessel of note was with the John C Stennis on approach to the Straights of Juan de Fuca. The Stennis was transmitting AIS with the ship name of NVXX (I don't recall the number used(XX)).
I see the same practice here: US naval vessels transmit only their radio callsign in AIS - no vessel name.

Gee, I hope opposing navies never figure out how to google the callsign.
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