Pressure Pattern Navigation

[dave_091]

I am just wondering who has used this method of navigation before on trips that are about 300 -350 nm?

How did you like using it?

I am going to try it out when I do my next 300nm trip.

[freego]

Instead of flying a straight line across a pressure system, it can be quicker to fly a curved track that follows the air flow around the pressure system. Gives greater tailwind component for that part of the flight which in turn compensates for and overcomes the slightly longer track distance.

____________________________________
Supreme excellence consists in breaking the enemy's resistance without fighting.
Sun Tzu brass knuckles

[Colonel Sanders]

I put pressure on the buttons of my GPS to turn
it on and select "direct". Then I put pressure on
the rudder pedals until "bearing" and "track" are
the same.

I note the heading, and write down the ETA, and
then there is no more pressure, even if all the
radios go blank.

[dave_091]

I put pressure on the buttons of my GPS to turn
it on and select "direct". Then I put pressure on
the rudder pedals until "bearing" and "track" are
the same.

I note the heading, and write down the ETA, and
then there is no more pressure, even if all the
radios go blank.

HA HA! Yep, I have become lazy with my GPS as well.

I am always willing to try out something new though. Pressure Pattern Navigation (PPN) seems like a interesting concept to me. The theory behind it makes complete sense. The math is very simple as well.
With PPN you take the pressure at your destination airport and the pressure at your departure airport. Apply the math formula and you get a a single MH that you fly for the entire course of your flight. Simple, and it makes sense.

If your pressure at the destination airport is the same as the pressure at the departing airport just point your AC at the destination airport and go. No matter how the pressure changes in between the destination and departure airports you will still arrive at your destination (for the most part).

If your pressure at the destination airport is greater than the departing airport then you will have a correction, we all know from basic meteorology that this correction will be added to your heading in this situation. The opposite would be true if the pressures were reversed at the destination and departing airports.

The book that I read this in is the first book in "The Proficient pilot" series by Barry Schiff. It is a three book series and I highly recommend this series to anyone flying. Three books for 40$ is the best money Ive spent at chapters dot ca in a while.

Im going to try this out on my next flight, I will track the flight with my GPS. I'll let you all know how it turns out.

[photofly]

Details...

http://williams.best.vwh.net/smxgigpdf/smx2001c.pdf

[Tim]

i just read another great pdf file about a brand new design for the wheel!!

seriously though, this seems like overkill for a vfr trip in a bugsmasher...

[dave_091]

i just read another great pdf file about a brand new design for the wheel!!

seriously though, this seems like overkill for a vfr trip in a bugsmasher...

In theory, its easier than traditional navigation. You point your nose at one MH and fly that heading for the entire flight.

Simple.

[CpnCrunch]

It does seem overkill, and a lot of work. From the pdf it doesn't look like you just 'point the nose and follow a MH'. You need to calculate waypoints and do the calculations at various points. Also you need to remember that weather systems tend to move, and they aren't always as forecast. Also the winds tend to vary at different heights.

My own opinion is that it's simpler and probably faster to just find an altitude with the best groundspeed and route direct with your gps.

Also, isn't it the case that if you have to 'cross a weather system' that you're likely to run into some really shitty weather at some point (if it's a low pressure)?

[trey kule]

Honestly, when I first read this, I thought it was a troll
300 NM flight using pressure pattern navigation?
Why?
A. It is definitely not a point the nose...and b. what type of a plane are we talking about here. A normally aspirated small airplane...?

[Tim]

i just read another great pdf file about a brand new design for the wheel!!

seriously though, this seems like overkill for a vfr trip in a bugsmasher...

In theory, its easier than traditional navigation. You point your nose at one MH and fly that heading for the entire flight.

Simple.

Reminds of the physics calculations that "prove" a bumblebee cant generate enough lift to fly...

[dave_091]

Honestly, when I first read this, I thought it was a troll
300 NM flight using pressure pattern navigation?
Why?
A. It is definitely not a point the nose...and b. what type of a plane are we talking about here. A normally aspirated small airplane...?

Before we get too far off course with this topic....

I wasn't intending this to be a " this works, that doesn't work" topic of conversation.

I was asking someone if they have tried PPN before and if so, what were your thoughts.

Judging by all the responses from this I don't think that anyone that has read this thread so far has tried PPN.

Be a critic all you like, I'm going to try it out. I will let you all know how it goes.

I will be doing the flight in a cherokee 140.

If you care to read about the topic there is a chapter dedicated to it in Barry Schiff's 1st book in the Proficient Pilot series.

[YYZSaabGuy]

Honestly, when I first read this, I thought it was a troll
300 NM flight using pressure pattern navigation?
Why?
A. It is definitely not a point the nose...and b. what type of a plane are we talking about here. A normally aspirated small airplane...?

Before we get too far off course with this topic....

I wasn't intending this to be a " this works, that doesn't work" topic of conversation.

I was asking someone if they have tried PPN before and if so, what were your thoughts.

Judging by all the responses from this I don't think that anyone that has read this thread so far has tried PPN.

Be a critic all you like, I'm going to try it out. I will let you all know how it goes.

I will be doing the flight in a cherokee 140.

If you care to read about the topic there is a chapter dedicated to it in Barry Schiff's 1st book in the Proficient Pilot series.

Good for you - be sure to let us know how it works out.
Too bad that a supposedly aviation-related forum can't tolerate some discussion around little-known aviation theory every once in a while. I guess it's just more fun to argue about WAWCON and mandatory retirement, piss all over new members who haven't figured out the "Search" function, debate the merits of ramp time and whether pilots are professionals who should be expected to clean out lavs, and moan endlessly about the industry's downward spiral.

[pdw]

Judging by all the responses from this I don't think that anyone that has read this thread so far has tried PPN.

Most already do pay attention to what the headwinds are in advance of a trip, and then more closely in pre-departure flightplanning to safely calculate fuel required for loading. (Which involves PPN to some degree anyway.)

Often on flight aware, when interpolating a particular AC's flightpath against current ADDS winds/temps weather-data of the track it is obvious pilots are seeking out the sweetspots in the prevailing weather pattern to maximize their tailwind (or at least minimize the headwind) esp when substantial ... and have also heard pilots speak of incentives for avoiding unecessary fuel costs where able.

[dave_091]

here is the math ( for all of you who think its too hard)

(p2-p1) k
_________ = Drift P2 is the pressure at cruise alt above destination airport
p1 is the pressure at cruise alt above the departure airport
TAS K is a factor depending on the average latitude of the trip to be flown

K factor for 43-50 degrees lat is 300
K factor for 50-55 degrees lat is 270

Lets use Halifax and Quebec airports. They are both situated between 43-50 degrees lat so we will use a K factor of 300.

Presure at halifax now is 29.90
Pressure at Quebec is 29.74
We will cruise at 100

using the formula we get -48 Nm

If you pointed the aircraft directly at Quebec airport when you flew from Halifax airport you would end up apprx. 48nm away from the airport on arrival. Not good.
So you apply the correction.
We are flying from a high pressure to a low pressure so the correction is going to be taken away from your Heading, to compensate for right drift.

Using the e6-b9 to calculate our drift angle just line up the amount of drift (42) on the outer scale to the distance travelled (350) on the inner scale and read the drift angle opposite 60 which is just shy of 7 degrees.

TADA! just minus 7 degrees from the MH between halifax and Quebec city ( corrected for variation) and fly that correction for the entire flight and it should bring you pretty darn close to your destination.

[dave_091]

well that didnt post properly. Here is the formula:

(p2-p1) K
________

TAS

= drift

[dave_091]

oops, 48 nm drift... sorry for putting 42 nm in the e6b calculation, it should be 48. This would give you just over 8 degrees correction.
Sorry for the mistake.

[ahramin]

Don't worry about the dough heads that can't do math. They're everywhere, not just this forum.

I look forward to hearing about your results.

[dave_091]

I found a post from somebody that actually used PPN on a different site. I guess it really does work.
It seems to be a form of navigation that died. I am guessing it died because you could end up flying all over a map rather than a straight line course. People are more comfortable flying straight lines from point A to point B I guess.

Here is the old timers post:


The magic formula and factors devised by Dr. J. Bellamy, Chicago give the net drift , in nautical miles:

(P1-P2)*K /TAS

Where;
P1= Pressure at Departure
P2= Pressure at Destination
K = Factor for average latitude between departure and arrival points.
TAS = True airspeed (knots).

Latitude - K Factor
22-25 - 540
25-28 - 480
28-31 - 440
31-34 - 400
34-38 - 360
38-43 - 330
43-50 - 300
50-55 - 270

(P2-P1)is positive= Left drift
(P2-P1)is negative= Right drift

When you have the net drift worked out,use flight computer (E6-B or whatever!)to figure out the drift angle. True heading + magnetic variation +/- drift angle gives single-heading to fly the route. As you probably know already, this is useless for flights at 2000" AGL or less, due to surface friction.

I’ve used this for fun, and found it to be no more than 1 or 2 miles off on trips of about 200 nm!

Hope that helps!

[Colonel Sanders]

I just use the 1/60 rule. For example, with a
track of 270 and 20 knots of crosswind out of
the north, at 120 knots that's a 10 degree crab.

[trey kule]

Here is a bit of trivia CS.. I ask every new CPL hire during part of the evaluation about 1.60 rule.
The vast majority of them have only just heard of it..No idea of the practical applications.
No idea whatsover how to use it , for example, to quickly get a rough heading to an alternate airport..
Using it backwards to determine the x-wind factor is completely out of their grasp.. Someone should start a thread on how to do this without a calculator, computer, or a set of forumlas or tables.

BTW. The last one I asked told me he simply determined the wind factor by looking at the G1000 screen...true story..

But I still dont understand using this technique on trips of 300nm or less, in a normally aspirated, small aircraft..I wait with baited breath to see how much time this will actually save..Flyng from SFO to Haiwii in a jet where you cross right through a huge high pressure system..Yes.. Maybe it is just a for fun thing. In any event, to do it properly you have to be able to maintain a heading, and that is a very good thing.

[sidestick stirrer]

Not to be pedantic but I think it's not exactly one-in-sixty, more like one-in-fifty seven point something...
My old Jeppesen "prayer wheel" has marks on it for pressure-pattern flying, never did figure out how to use them.
I always thought that this particular type of navigation would provide the best wind component while not taking us too far off the straight-line course to achieve it...

[Colonel Sanders]

It's pretty easy, actually.

At 180 knots, you notice that you need 15
degrees of crab on the heading, to maintain
the correct track with your GPS. What's the
crosswind component of the wind aloft? How
would you determine the actual (entire) wind
aloft?


You're inbound in your F-104 and you've
slowed to 360 knots. You notice that you
are holding a 7 degree crab to maintain
track with your Litton LN-3 INS. What
is the crosswind component?



You're heading east at 120 knots. A
strong cold front has passed. What is
your first guess at a heading and groundspeed?


Too bad they don't ask questions like
this on the CPL written. Here's another
favorite of mine:

You're asked to deliver an older airplane that
has no cruise performance data in it's POH.
It has a 180hp engine. You're told it cruises
at 90 knots. It has a 24 gallon gas tank. In
zero wind, how far can you fly before you
should stop for fuel?


****

Most experienced pilots are very good at
estimating. This is not a parlour trick. Every
once in a while something high tech will toss
something preposterous at you. Your feel
for the system through estimating, plus your
situational awareness, will catch this error
as "garbage out". So, you have to start
digging and find the "garbage in".

Something else that experienced pilots have
is a very good innate sense of estimating
time. An experienced pilot could fly a full
procedure approach without a timer - but
never voluntarily would

I ask every new CPL hire during part of the evaluation about 1/60 rule.

If he replied, "Ask 60 women at a party to fornicate. One of them will not say no", I would hire him. Shows that he's a real go-getter and shows initiative.

[trey kule]

57 point something! I guess I am one of those mathmatically challenged pilots who needs to do the math in his head using a smple 60. These calculations are not intended to provide perfect answers as all that is needed is a rough calculation, and I have never had a problem using 60 instead of some decimal number...
It really is understanding the concept, not trying to get a perfect answer , particularily with all the other variables at play...
BTW, we use this formual (60.1) on a rather routine basis to determine a rough heading to a fix, and it typically works out pretty well spot on.
Here is an actual example..
You are 45 miles from a VOR , inbound on a track of 332 (you can use the same for heading for simplicity). GS is 244 kts.( you will maintan this speed until you are finished the turn to line up with the loc. You want to go to establish onto runway heading 3 miles outside the IAP for the ILS to runway 36 (nothing in the GPS data base), and want to get there in as straight line as possible rather than flying to a specific distance and then doing an arc.. The point is 18 DME from the threshold...What is your approximate heading? And do it in your head. The rain is pounding down on the plane, you have not tweeted anything for over five minutes and your FO is giving you the deer in the headlights look when you ask them for a heading so that you can compare your calculations to see if they are similar.
This also has some very practical non theoretcial considerations, but for now, just quickly get a heading.

Speaking of drift...how is this for thread drift?

[Colonel Sanders]

how is this for thread drift?

To quote R. Lee Ermey: "I've seen better, and
I've seen worse, but not much!"

But seriously, folks ... it would be nice if only
fresh CPLs - you know, under the age of 25,
only shave once a week - answered these
questions. PhD not required.

[dave_091]

Nobody is going to answer those questions?