Francis Meyrick

Moggy’s Tunaboat Helicopter Manual “GPS 4-4 “

Posted on April 13, 2010

Moggy’s Tunaboat Helicopter Manual

Section 4. GPS Systems and Offshore Navigation Issues

4-4 Limitations and Failures

1) Limitations

You need to consider carefully that a ship can move quite a distance in the two hours you are away. Some purse seiners can cruise at 18 knots. That’s 36 nautical miles! If you are in a Hughes 500, you can still cover that fairly quickly, but in a slower Bell 47 that can really worry you. And be aware it may be a matter of a lot more than 36 miles for you. The problem can become compounded. You have to allow for flying perhaps to the wrong spot, realizing the error, sorting it all out, and then flying another leg back to the right location, during which delay the boat has moved yet further perhaps, and so….
Added to this is the problem that there is a limited range on the Ross DSC 500. Beyond this range, you simply will not be able to pickup the ship and get its latest position. You’ll get ‘no response’ every time.
The point at which you actually lose the ship varies with height, but also seemingly with equipment set up and especially aerial installations, and weather. Most guys fly somewhere between 800 and 1000 feet. I do when I’m spotting tuna. Some days you will lose the ship at 24 to 28 miles. Other days you will keep it much further. I’ve had a perfect ‘connect’ at 42 miles. On a calm day.
In a Bell 47, speed and fuel considerations make 30 miles from the ship a long, long way. On the way back to the ship you will be expecting to get an update on the ship’s position pretty quickly.
So (if it’s not an automatic update) you will be hitting ENT a few times until you get “Deedle-deedle-dee… “.
There’s always a feeling of relief when it comes through, and the ship’s range is within the expected numbers!
The WORST thing a ship can do,is launch you one way, head off 180 degrees the other way, and not tell you.
Oh yeah… it happened to me one day…

I was in a Bell 47, new and raw in the Tuna Fields, and I’ll give you one guess which way the wind was blowing! Smack into my face on the way back, 20 plus knots! And that, in a Bell 47, is bad news! We struggled on back, and I was trying to get a manual lock on the ship. I kept getting ‘no response’. Until such time as you get a new (updated) position, the old position will be available, (depending on equipment) and you navigate towards that, hoping to get a lock on the new position.
As we went through the 20 miles point (from the old ship position), I started to get really worried. Little did I know what had happened! My observer spoke little English, and didn’t understand when I asked him if he knew where the ship had gone. Onwards I struggled, against the 20 knot headwind, becoming more and more worried. When eventually the Ross does give you the ‘Deedle-deedle-dee….’ and you suddenly find the ship is 26 miles further away from you… you sweat! In a Bell 47, with 20 knots against you, you’re looking at running on vapor! The communication with my observer at that time was so poor, I never could get the ship to turn around. It is really frustrating seeing the ship, struggling towards it, desperately low on fuel, whilst all the time the ship is steaming full speed away from you.
Needless to say, I had a big pow-wow sitdown with the captain, a meeting of the minds, (he was a real good guy), and it never happened again.

What I learned to do from that, is that I check after 30 minutes or so, (in a Bell 47) before I go out of range,and I update the ship’s latest position right then. So I don’t wait two hours. I try and keep the ship’s position loaded into GPS as accurate as possible as long as I can. Of course, in the Hughes 500, speed is so much higher, and it’s also easy to climb quickly for a better signal.

Okay, here’s a little quiz for you. To test your knowledge.

Quiz 1: You take off the ship, in a Bell 47, from this position:

(I’ve put you somewhere North of Papua New Guinea, south of Truk Island, and West of Micronesia)

5 45.00 North (degrees/minutes/seconds)
151 56.00 East

You fly heading 300 degrees. (West North West).
After 30 minutes, you check on the ship’s new position.

It comes up as:

5 40.00 North (degrees/minutes/seconds)
152 02.00 East

Question 1: how do you represent those positions in decimals?

Question 2: Is there anything to worry about?

A) No, the ship has not moved much
B) No, on the contrary, the ship has kindly moved in the same direction as you are going.
C) Oh yeah! She’s moving away at warp speed….

Question 3: Roughly, what speed is she steaming at?

A) 8 knots
B) 15 knots
C) 4 knots
D) 44 miles an hour (it’s a jetfoil)

The answers are at the bottom of this chapter!

2) failures

Some guys carry a spare GPS for back up. I generally didn’t bother, but that’s always good thinking. The good news is that the Ross DSC 500 units are very reliable. I’ve had a total electrical failure, which was interesting. The only thing left working was the stop watch and the TigerShark GPS. (it has a battery back up). Needless to say, we couldn’t hear or answer radio calls, and there were apparently some anxious moments back on the bridge. They called and called and called. NO reply! Have they crashed!???? Then they spotted us on radar. A dim, intermittent little blip. Struggling home.
“They’re still flying! ”

I’ve also had a minor argument with two mini waterfalls pouring into the cockpit, through both open doors, which involved copious amounts of water washing all over the radio stack. All the lights flickered alarmingly several times, ON-OFF-ON-OFF…. but it still got me home. That was another story, and you’ll find it described under this title:
A Blip on the Radar (Part 2) “Running the Gauntlet “.
I don’t recommend that experience at all.

Just about every helicopter carries at least a basic transponder. You may not have encoding capability, but as long as you can deliver a nice healthy ‘blob’ on the ship’s radar screen, and as long as you are within radio range, the ship can give you “radar vectors ” IF ( a big “IF “) they are clued up on this. That is a big, and very important “IF “! One of my captains did it, just like a pro ATC approach controller, and I describe that interesting experience in the next chapter, “Sunset “.

Remember you can always climb for better radio reception. This is an area we talk about again under ‘cockpit communication’ later on in this manual. It really is a safety issue that somehow language hurdles can be bridged so you can make the observer understand when you need radar vectors! Be aware that, without a transponder, the captain may not be able to see you if there is a lot of weather clutter on his screen. I’ve been up with an observer who I know would never, ever have understood radar vectors. All he wanted to do was go asleep. More on this later. You suddenly feel naked! You sure hope your Ross system doesn’t pack up.

Corrosion is your relentless enemy in the Tuna Fields. If you’re like me, you will use a lot of fresh water, turtle wax, Triflow, WD40 and elbow grease. Some of the photos of my little bird will show you the shine! Despite all this, it’s possible your antenna may fail. Usually at the connections. If your GPS fails, and you don’t have a spare, or the spare’s battery then decides to go “bye-bye, sucker…! “ at exactly that most inopportune moment, then there is one more neat little trick I will share with you. I’d heard about in a Tuna Pilot Dosshouse cum Bar somewhere, tucked it away in a decaying memory cell, and, guess what, one day... I got to try it for real. I remember the weather was pretty rough as well, and I was actually fervently hoping it would work. What you do is you reach up, and with one hand you can unscrew the aerial coax connection. Now you have disconnected the AIRFRAME aerial, and you are going on to the GPS unit’s INTERNAL antenna. It actually worked, and took us home.
I’ll be darned…
The observer was real impressed, and secretly, so was I. Had I been a smart fellow, I would have tried it one time for practice, before I suddenly needed it for real…
But it sure was interesting watching a blank GPS screen, unscrewing the exterior antenna coax cable, and then seeing the screen jump back into life again.

Normally I have my transponder on “standbye “. It’s warmed up, ready if I need it, but normally it doesn’t get used. Why not? Because you give the game away to other captains! They also have bird radar! If you start circling and spending a lot of time in one area, they might come checking. If you disappear off the screen, and then pop back up after a couple of minutes, well, it’s a reasonable bet you’ve been down to drop a radio buoy!
Aha! Ach so…. die Leute haben etwas gefunden…!
(Pigeon German for: “Aha!!…. ze deveels have founded some zing…! “)
I have often stood with my favorite captain, the great Alan Lai, watching another helicopter, doing just that!
“Hmmmmmmm! “, we said. “Let’s take the chopper and go take a look! “
We did, we found a bunch of foamers, we called the ship in, and we caught a bunch of fish! That night we had some beers, raised our glasses, and solemnly toasted the hard working rival pilot concerned!

All’s fair in love, war, and Tuna!

The answers to my quiz above:

5 45.00 North = 5.7500 North
151 56.00 East = 151.9333 East

5 40.00 North = 5.6666 North
152 02.00 East = 152.0333 East
I included this because I’ve seen people get confused. Heck, I get confused. It doesn’t take much.

And to further confuse you, if you’ve never seen it before, some equipment will show you degrees/minutes/(thousands of a minute).
Example: 151 56.923 (151 degrees, 56 minutes, 923/1000 of 1 minute)
That is actually what we use here in the Gulf of Mexico, and it is of course way more accurate than just degrees/minutes/seconds.
You need to be able to understand the differences, and quickly convert from one to the other.

Now for the question 2). This is an urgent, real-life scenario, and, sooner or later, you WILL encounter this. I’m hoping you understand that this is where you need to have a mental ‘picture’ of what’s going on. You can’t just endlessly play the SINR and plug in numbers. And see what the magic GPS box tells you to go and do. YOU are the master, not that silly little plastic box. Mass produced by the lowest bidder in a back alley in Taiwan…

The answer is….C) !!!

Question 3) B (and it’s doing that AWAY from you…!!)

There are many more exercises for you to do to develop a mental picture of your true position vis-a-vis your moving boat. Including other little tricks of the trade. I’m working on a chapter to include later on…

Francis Meyrick

Last edited by Francis Meyrick on April 13, 2010, 4:25 pm

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