On Tue, 22 Dec 2015 23:03:27 +0000, Phil W Lee
wrote:

John B. considered Tue, 22 Dec 2015 19:01:17
+0700 the perfect time to write:

On Tue, 22 Dec 2015 02:51:04 +0000, Phil W Lee
wrote:

John B. considered Mon, 21 Dec 2015 08:01:54
+0700 the perfect time to write:

On Sun, 20 Dec 2015 20:04:43 +0000, Phil W Lee
wrote:

John B. considered Sun, 20 Dec 2015 17:50:33
+0700 the perfect time to write:

On Sun, 20 Dec 2015 02:25:09 +0100, "Jakob Krieger"
wrote:

- John B. / Tue, 15 Dec 2015 11:49:53 +0100

Of course with plastic ropes and fixtures,
you don't need a knot any more for many things.

But for rescuing »man overboard« or joinig ropes
for more length, classical knots are still used.

What ropes would that be? The main halyard? About 80% wire rope? The
main sheet? Wire again, or the jib sheet... wire once again.

Well, it used to be considered as a good precaution to
have a roll of rope lying somewhere in the boat.
Even in cars, towing-ropes can be found.


May be except for GPS sailors, they don't know
what a knot or even a rope is.

Sort of snarky remark isn't it? After all big ships navigate with GPS,
airplanes navigate with GPS. It has been quite a number of years now
since anything commercial used the stars.

Nobody with a little bit of experience (bike or car drivers
included) relies on GPS only.


I see. Do you really think that the 1st officer on, say the Emma
Maersk" is out on the bridge wing every day taking his noon sight? Or
that a B-52 comes equipped with a sextant? Or that any modern
commercial or military vehicle comes with a copy of the six H.O.
tables?

The U.S. navel Academy stopped teaching celestial navigation nearly 20
years ago stating that while celestial was accurate to a 3 mile radius
that GPS was accurate to a 60 ft. radius.

Almost everything of any size used inertial navigation in between
traditional and GPS, and certainly until VERY recently, it was not
legal to use GPS as the primary means of navigation in an aircraft of
UK registry.
That's what radio beacons are for, in all their various types - VOR,
DME, NDB, and ILS (and yes, I know how to use them all, although not
for all the various functions required for a full UK instrument rating
- the NDB approach is notoriously difficult). I'm fairly sure that in
coastal waters, ships use a similar system of beacons, mostly housed
in what used to be primarily lighthouses (and sometimes still perform
that function as well).

So, do you navigate across the Atlantic, or even worse, across the
Pacific with radio beacons?

Actually, you can.
DR gets you close enough to pick up beacons in plenty of time to avoid
bumping into anything and correct your course to make landfall where
you need to.

That isn't the way that you described navigation in the U.K. :-)

I don't believe I ever did describe navigation IN the UK, just that
required for a rating under UK regulations. I'm fairly sure that
celestial navigation is still taught in the Royal Navy - it certainly
is in the Merchant Navy, and it would be a bit strange for Naval
Reservists to out-qualify their full time Naval counterparts.
Nearly all training is about what you need to do when things go wrong,
not when they are going right, and electrical failure is certainly not
an unanticipated failure mode.

Re costal radio beacons. It might be an anomaly but I certainly have
never seen them anywhere in Asia, nor have I seen a reference to them
and certainly if they were in common use navigation charts and sailing
directions would have reference to them. Any active light house is
marked on the chart and it's light signal described.

They certainly do have radio beacons in Asia - they may not be
intended primarily for maritime use, but can be used by suitably
equipped craft. You can even DF on commercial stations fairly easily
if you have the (not particularly expensive) equipment.


Come now. You wrote, "I'm fairly sure that in
coastal waters, ships use a similar system of beacons, mostly housed
in what used to be primarily lighthouses".

I reply that I've never seen such a thing and then you tell me that,
"They certainly do have radio beacons in Asia".

Well, of course they do. Intended for aircraft use, not in light
houses. And of course, if one has the required equipment one can get a
direction fix from any radio transmitter.

But how many ships and boats have radio direction finding equipment.
In fact, how many commercial ships still carry a Radioman or have a
"radio room".




Bubble sextants were certainly part of the standard equipment on the
Vulcan, so why not the B-52?

The last (I believe) U.S. made aircraft that had the ability to use
celestial navigation were early models of the Boeing 747, which were
phased out in the 1960's. The SR071 had a automated celestial and
inertial navigation. The last SR-71 left service in 1989. The last
Vulcan was delivered in 1965.

You are talking about old technology.

Which you certainly CAN use in anything which has outside windows big
enough to give horizon and solar/star sighting at the same time.
There are even specialist gyro stabilised bubble sextants designed for
the purpose, and tables to offset horizon angle by altitude.
Battery life isn't really much of a problem in the duration of any
normal aircraft flight, and on water you can pick your moment over a
much larger timescale.

Yup, certainly. But no windows :-) And, without a bubble sextant it is
awful hard, at 30,000 ft to get a good horizon. And if a fancy
electronically stabilized sextant then why not just use GPS.

Well, a military aircraft should anticipate the possibility of the GPS
constellation being knocked out.

But there is no necessity. You said, above, that you could use radio
beacons and other radio stations to navigate by.

By the way, to accurately locate the seismic lines used in oil field
exploitation they haven't used a sextant in years and years. All GPS
these days.

Well, that's a commercial decision, so you use the cheapest that works
(or your shareholders are going to complain).

But why all the excitement about sextants? Just use your D.R. and when
you get close look for a landmark. All sailing directions have a
wealth of descriptions of landmarks.

And, there are days, sometimes weeks, that you can't see well enough
to get a sight, and other days when it is too rough to get a good
sight and even when you do your "cocked hat" is probably a mile on
more on a side... if you are really good and more then likely, in a
small boat, a lot bigger.

Even in rough weather and a solid overcast a GPS will give you a
location within feet :-)

After an intermittent soaking with seawater?

Well, an intermittent soaking with sea water will pretty much destroy
your charts and your H.O. tables and having a sextant without these
two accessories is pretty much a futile exercise in navigation :-)

But more realistically, most yachtsmen, on offshore voyages, carry at
least two GPS receivers, and sometimes even more. I've even got a
wrist watch device that includes GPS. Some boats carry "chart
plotters" and don't use paper charts at all any more.




Note that INS units had to be "borrowed" from some old airliners in
museums to strap down in the crew compartment of the Vulcans used in
the "Black Buck" operations of the (pre-GPS) Falklands war. In their
original (nuclear) role, they were expected to navigate by DR and
celestial, as it was assumed that most beacons would be off air or out
of range, and the DR part is kind of difficult over a featureless
ocean like the South Atlantic, as it relies on position checks (which
were carefully surveyed for the routes the Vulcan force was assigned
to on their nuclear role). All INS units are large, as they have big
gyros in them, so aren't suitable for small craft, and have to be set
up with accurate starting positions - in aircraft this is done by
positioning the craft on a carefully plotted navigation marker painted
on the hardstanding and hand entering the exact latitude and
longitude. The aircraft has to be kept completely still for several
minutes while the internal gyros spin up to speed and self-tests are
performed. They also accumulate errors over time, as they have to
make a "best guess" approach to precession.
I had no idea that US naval navigators were so badly trained - aren't
naval forces supposed to be able to operate in time of war, when EMP
could have killed the GPS constellation, along with most other outside
reference signals?
Or maybe they rely on being able to scavenge some old kit out of
obsolete vessels in that situation?

Of course, on smaller craft, the bigger problem is likely to be
reliance on power - particularly on sailing vessels.
One of the major certification requirements for aero engines is that
they be electrically self-contained, usually achieved by using magneto
ignition.




I hate to be the one to disillusion you but I don't believe that any
operational U.S.A.F. engine today uses magneto ignition :-)

I think you'll find that some of the smaller trainer aircraft do use
piston engines, complete with magnetos.

I made a very quick check and I don't believe that the USAF has any
reciprocating engine aircraft in use. At least every thing I see with
a propeller is a turbo-prop.

They still have at least one Slingsby Firefly, with it's Lycoming
engine, based at Edwards AFB, and believe it or not, an AN-2, but the
main reason so few piston engine aircraft are still officially used is
that they outsourced nearly all of their primary training, and the
aircraft that went with it! Despite that, there are still 25 T-53As
(Cirrus SR20) in the inventory, and I believe a few T-52As (Diamond
DA40), although these may have all been replaced by T-53s now.
There are even 3 T-51As (Cessna C150) still in use.

The USAF has done, probably the majority of their primary flight
training, through outside contractors for years and years. My first
job after school was at an airfield in a small town in Georgia
operated by Southern Airways Corp. that provided primary flight
training for the Air Force... using the original T-6.

As for Edwards AFB, they have a lot of odds and ends of aircraft
there. Some, and I suspect the Slingsby Firefly, as there were a
couple of crashes with that aircraft, that Edwards did some flight
testing to see if the aircraft would recover from one particular
maneuver. The aircraft passed the tests I believe :-)




I did, how ever, work on what may have been the last of the
reciprocating powered bombers that the USAF had - the B-50 which did
have magnetos.... however to start the engines the system used
"voltage boosters" that served to feed a higher voltage to the
ignition system than the magnetos could produce at starting RPM. The
"voltage boosters" were operated by the air craft's electrical system,
that for starting was powered by an external power supply.

Nope. A voltage booster. the P&W 4360 had a low voltage magneto system
to avoid voltage leaks at high altitude and they definitely had a
voltage booster for each of the two mags.

The old tried and true of making a rough check of whether the mags are
putting out was to grab a spark plug lead and tell the guy to "hit the
starter". The shock was enough to jolt you but it did make for a quick
check.

I once watched a bloke try the same thing with the R-4360, which had
voltage boosters, and it almost knocked him off the stand :-)

IIRC, magnetos don't lose much in the way of sparks at low revs - it's
more to compensate for the voltage sag that engaging the starter
causes.

Nope, magnetos produce a lower voltage at starting revs. Way back they
used what was refereed to as an "impulse coupling" to sort of kick
start the mag to get enough voltage to fire the plugs at starting.

Magnetos, you may recall, work perfectly well on motorcycles with
kickstarters!

But, you get more revs from the kick starter on a bike than the
starter on a large aircraft engine.

On large aircraft engines, maybe, but I've not had much to do with
them. I do know that motorcycle kickstarters are very variable,
partly depending on size. Big singles (500+cc) are particularly slow.

Really, I had a Harley 80 cu. inch, flat head, and had no problem kick
starting it. I never owned a 500 c.c. bike but I did ride a mate's 500
c.c Norton single and it started easily. (In fact, the first
motorcycle I saw with an electric starter, I wondered about whether it
was intended for the ladies :-)



That goes pear-shaped pretty quickly if you then can't find
a runway to land on as soon as the power goes off! This is also why
at least a basic set of primary instruments are vacuum powered, so you
can at least keep the aircraft flying the right way up and in the
right direction if all the smoke comes out of the electrical system.

Come now. I flew with my father when I was just a lad, in a Piper J-3
and it didn't have any vacuum instruments in it.

Only because it only had pitot/static instruments and a turn & slip
indicator!

No turn and slip indicator. An altimeter, magnetic compass and air
speed was all the flight instruments it had.


some snipped
--
cheers,

John B.