Flight optimisation by altitude and vectors

[Ian]

Hi All,

 

Given variations in wind speed at altitude the "shortest" path between two points is may not be a direct route especially on longer flights. Does anyone know of software or other tools so optimise flight paths, engine time and fuel use?

 

 

[RFguy]

Now that's a cool idea Ian. No doubt the airlines have something like that. Years ago one  would write a fancy algorithm. Now you might just compute all options (IE in 100' and 3 deg track steps)  and present the user with the best three to evaluate. I assume the published GPWT charts could be obtained as a data matrix. -glen

Edited April 12, 2023 by RFguy

[skippydiesel]

I do not see a practical use for such a service for, most,  recreational level aircraft (allowing for those flying high performance "jet" & turbo props). Even on "longer flights" we rarely travel for long/far enough, say within a  6 hrs period. The weather(winds aloft) information we get now  (Google/BOM)/Ozrwys/etc) is more than enough for our short range/time capabilities.

[Ian]

Not being particularly practical didn't stop facebook or twitter! 😉

 

[spacesailor]

Yes ! , But.

If you ' catch 'the " morning glory " , heading west from Weipa, Cape York to Darwin , you could turn off your motor & coast the 745 mile trip .

But to answer your question , Ask the 'ballooning ' fraternity. They Will know . As that's their specialty. 

Three days Perth WA to the east coast ! . Faster than a speeding Jabiru . LoL

And , Propane powered .

spacesailor

[spacesailor]

FACEBOOK .

Is the worlds most ' practical ' way of " communication! .

Every year ( before FB  ) we paid excessive amounts of money to the " telecommunications " and " postal services .

Ended with  $ 5 calender + $ 3 envelope + $7 postage for our ten closest relatives in Europe .

Every phone call to them , was in the tens of dollars per minute .

Add to that every bithday / wedding or baby's arrival was an expensive affair .

SO

F B a big thankyou .

We can see & speak to our relo's , so far away , 

spacesailor

Ps ( post Australia is now in the ' red ' with the decline of letter writer's.

While our ' telecommunications sold out to China 's Singtele corp .) .

 

 

[facthunter]

A lot of your level choice will be terrain, turbulence, cloud base and quadrantal . Not a lot of choice under 9,000/10,000 ft  Nev

[turboplanner]

3 hours ago, Ian said:

Hi All,

 

Given variations in wind speed at altitude the "shortest" path between two points is may not be a direct route especially on longer flights. Does anyone know of software or other tools so optimise flight paths, engine time and fuel use?

 

 

Yes, a Kane computer and  a WAC Chart.

There are alternatives to flying straight into a head wind, and in some cases on some days a CTA obstruction becomes less of an obstruction. You don't have to do too many trials to get a reasonable optimum.

[old man emu]

7 hours ago, Ian said:

Hi All,

 

Given variations in wind speed at altitude the "shortest" path between two points is may not be a direct route especially on longer flights. Does anyone know of software or other tools so optimise flight paths, engine time and fuel use?

 

 

A couple of good conversation points here. The answers depend on what result you are after: 

1. Shortest time to get from A to B
2. Minimum registered engine hours for the flight from A to B.
3. Minimum fuel usage

1. Shortest time:

Basically, if the wind is directly behind you, distance/speed will be least. So draw the direct route on your chart. Then draw a line parallel to the wind direction. See how far you can fly along the wind direction line before you have to turn off it to a heading to close the triangle to your destination. That is a method to reduce the numbers of hours you write in your logbook.

 

2. Engine time:

Engine time meters (Hobbs meter) are not clocks. They are geared so that R revolutions of the crankshaft = 1 hour. So, it you push the throttle through the firewall, the hour meter will overread compared to clock time. If you use normal cruise power (about 75%) the meter and the clock should show the same.

 

3. Minimum fuel usage

This is determined by two things - engine revs and  fuel/air mixture. The first thing to do is to determine what airspeed you want to use to get either 1 or 2 above.

 

If you have a tailwind component that is added to your airspeed to give you your ground, then maybe you could reduce engine revs to reduce the actual airspeed. In other words, use the wind to your advantage. 

If the tailwind component isn't of use, you could look at altitude to make use of the reduced amount of fuel to produce a chemically correct mixture (leaning out). 

 

It was these last techniques that Charles Lindbergh showed the  P-38 Lightning pilots so that they could carry out the raid that resulted in the death of Admiral Yamamoto. This technique was used extensively by Japanese navy pilots to enable them to traverse long ocean distances in the A6M (Zero)

[facthunter]

The longer you are in a tailwind the more benefit you get from it. Use a lower cruise speed and save fuel. With a head wind if you have a slow plane consider flying another day, if the groundspeed is ridiculously low or fly at the higher cruise airspeeds. There are times in U/Ls where I've gone fairly low in remote areas to get out of the freestream a bit with high headwinds.  Nev

[Ian]

7 hours ago, turboplanner said:

Yes, a Kane computer and  a WAC Chart.

There are alternatives to flying straight into a head wind, and in some cases on some days a CTA obstruction becomes less of an obstruction. You don't have to do too many trials to get a reasonable optimum.

Yes but while artillery tables could be calculated manually this is the type of thing that can be automated and parameterised pretty simply. Sites like windy provide far more granular data than a WAC chart, where every pixel colour is a speed associated with a vector. While some people have fond memories of slide rules they're an anachronism in the present day and age.

I know that someone mentioned that "Fuel and airframe time" were the most important thing in aircraft operations, and yet we're counselling people to optimise with a bit of paper and a slide rule?

[turboplanner]

30 minutes ago, Ian said:

Yes but while artillery tables could be calculated manually this is the type of thing that can be automated and parameterised pretty simply. Sites like windy provide far more granular data than a WAC chart, where every pixel colour is a speed associated with a vector. While some people have fond memories of slide rules they're an anachronism in the present day and age.

I know that someone mentioned that "Fuel and airframe time" were the most important thing in aircraft operations, and yet we're counselling people to optimise with a bit of paper and a slide rule?

Yet we are having this discussion now; we are looking at lost knowledge of how to achieve the result; we are looking at a majority of people actually in command of aircraft not knowing there was a result to achieve.

 

Of course you can build an algorithm so optimise the result, but how silly is it that the Captain of a ship in the 1700s knew how to optimise a voyage but a Pilot in Command doesn't know he can.

[old man emu]

14 minutes ago, Ian said:

slide rules they're an anachronism in the present day and age.

I have to agree that electronic devices and their software make the completion of computations so much easier that mechanical devices like a whizz-wheel. However, both devices are ultimately dependent on the user determining which data to use as values for the variables. 

 

As for using a WAC, I think one's choice depends on your style of understanding information. I admit that I understand things best when I see them represented in "written" form. I have more information of a situation by looking at Heading and Wind direction lines on a WAC than I can by other means. Maybe that's a result of my education being conducted before electronic digitisation. Is it that a person born after, say 1975, has had the way their mind works influenced to a great extent by electronic digitisation. 

 

The drawback I see is that by having devices to do tasks, fails to provide a person with the basic knowledge behind the operation. Here's an instructional video on how to use a simple calculator. You don't need to watch past teh first calculation to get the point I want to make.

 

 

Now this does not show what addition actually is. To do that, you need to have real objects. Let's use paper clips.  From a container of paper clips, take out some and from those count out three, and put them down together. Then count out six and put them down away from the first three. Now, put the three clips on the pile of six. Now count how many clips there are altogether. You will count nine. That shows that three things added to six things results in your having nine things.

 

Note this very important concept: In the example above I initially used the names of the numbers (three, six and nine), but note that in my last sentence those names can be seen as adjectives describing the word "things", the same way that "paper" together with "clip" describes the object. When we verbalise mathematical tasks, we shorten our speech by only using the adjective, not mentioning the physical thing that the adjective describes. That's why our maths teachers always have to remind us to include the object when quoting our answer - nine paper clips.

[RossK]

16 hours ago, old man emu said:

2. Engine time:

Engine time meters (Hobbs meter) are not clocks. They are geared so that R revolutions of the crankshaft = 1 hour. So, it you push the throttle through the firewall, the hour meter will overread compared to clock time. If you use normal cruise power (about 75%) the meter and the clock should show the same.

A Hobbs meter is a clock, it does measure time.

What you are talking about is a Tach Time meter

[old man emu]

5 hours ago, RossK said:

A Hobbs meter is a clock, it does measure time.

What you are talking about is a Tach Time meter

OK.

 

There is also the airspeed activated timer that begins timing as soon as the aircraft's airspeed is above stall speed and stops when the airspeed goes below. That sort of time measures wheels-up to wheels-down, which is the official Time in Service for an airframe.

 

BUT! BUT! BUT! There is also the manufacturer's TBO which is based on the number of hours that the engine is operating: start-up to shut-down. 

 

How about we accept that these two systems operate at the same time;  that they cause confusion in record keeping, and that it is probably wiser to apply engine time to airframe time. It's probably only after many years that the difference become relevant.

[facthunter]

You won't come across too many "lifed" parts on most airframes. Happens more with aerobatic planes. The operator decides which system to use and has to stick to it . There's a factor used to reach an equivalent so there's no ridiculous a advantage gained by how it's done.  Nev

[spacesailor]

The advantage to ' Hire'rs ' is Hobs adds more hours than flight time, When held for longer than normal time on taxiway .

Just a student waiting to '' soar like an eagle '' .

spacesailor

[Ian]

3 hours ago, turboplanner said:

Yet we are having this discussion now; we are looking at lost knowledge of how to achieve the result; we are looking at a majority of people actually in command of aircraft not knowing there was a result to achieve.

The approximation that you're talking about isn't a lost art, generally it's basic maths. However it is significantly different from an optimised curve through 3d space which a half decent algorithm can achieve with the correct inputs.

Anyone with half decent maths ability and an understanding of vectors can do most of the calculations which a whizz wheels do in their head. Personally I'd like to be able to instantly have an optimised path through a range of altitudes and vectors. Personally I think that whizz wheels are due for the dustbin, fun to use but no more relevant than the cavalry in WW2.

There is a significant lack of understanding in relation to how planes actually work. If you ask most people why planes fly high they'll say because it's more efficient. The reality is that if you fly at the best L/D ratio this is your minimium fuel consumption, however altitude impacts your speed or time in the air.

 

 

 

The diagram below shows that range isn't impacted by altitude.

Jets are a bit different because turbine are terribly inefficient at part throttle. The american turbine powered tanks were terrible at idle.

[spacesailor]

Not many Jets are good at the speed our light aircraft tend to achieve .

Our smallest aircraft has moved from a prop to a jet, & now has all but disappeared .

'' The Bede BD-5 Micro is a series of small, single-seat home-built aircraft '' .

spacesailor

[old man emu]

10 hours ago, Ian said:

whizz wheels are due for the dustbin, fun to use but no more relevant than the cavalry in WW2.

The battery doesn't go flat on a whizz wheel, and they still work after you from them on the ramp. 

 

10 hours ago, Ian said:

Anyone with half decent maths ability and an understanding of vectors can do most of the calculations which a whizz wheels do in their head

Let's use the example of an aircraft flying straight and level on a known heading, and a known airspeed, and the heading and speed of the air mass it is encountering are also known. That sets up a 2-Dimensional system of vectors, which could be represented by coordinates (x, y) with appropriate identifying subscripts. Note I said that the aircraft was flying straight and level, thereby eliminating the need to consider the third dimension (vertical displacement) it has no speed of direction in his example.

 

So, given that the vectors of the aircraft and wind can be considered as the sums of their vectors in the x and y directions, how can you calculate, in your head, the resultant vector since that calculation involves the use of the values of sine and cosine of the two headings?

[facthunter]

Use the one in sixty rule.  Nev

[Ian]

1 hour ago, old man emu said:

The battery doesn't go flat on a whizz wheel,

I do like whizz wheels, however I believe their place in the industry is somewhat overemphasised. They're a calculator that doesn't require batteries

For example the current ban on being able to use trigonometric functions such as  sin and cos during navigation exams is absurd. No you have to use a whizz wheel. At one point there was resistance in the school and university system to getting rid of slide rules and log tables. 

 

1 hour ago, old man emu said:

So, given that the vectors of the aircraft and wind can be considered as the sums of their vectors in the x and y directions, how can you calculate, in your head, the resultant vector since that calculation involves the use of the values of sine and cosine of the two headings?

High school and further maths tends to spend a bit of time working around the unit circle where values like 1/sqrt(2) (0.0707) and sqrt(3)/2 0.87 and their inverses which can provide you with some of the approximations that you need, at some point I developed a habit the habit of mentally checking calculated values with approximations. If you understand how the values change between these points you can generate better approximations if required. Given the error values associated with the actual wind values your error bar isn't that bad.

On 14/04/2023 at 8:40 AM, old man emu said:

I have to agree that electronic devices and their software make the completion of computations so much easier that mechanical devices like a whizz-wheel. However, both devices are ultimately dependent on the user determining which data to use as values for the variables. 

It relates to what you said in the exercise above, if you make your mental model incorporate something like the unit circle then it also incorporates vector arithmetic.

 

[old man emu]

Ian,

You sound as though the Force of mathematics is strong in you. I appreciate that. However, I wonder how many of those who read your post have a clue what the Unit Circle is. I do, but for them it might be a number of high rise residences laid out on a round ground plan. That wind problem is depicted visually on the sliding scale of a Jeppo at the start of the calculation phase of flight planning, which makes it clear to most people.

 

I wonder how many people, when doing a flight plan seek the answer to, "If the forecast winds are relatively correct and remain so during the period of my flight, what sort of crosswind can I expect when I arrive?  And another useful help the Jeppo wind slide gives: If I'm heading ddd degrees, and the noise stops , which way should I be looking to head so that I set up my Final direction to land into wind as much as possible. 

[facthunter]

Dust, smoke and wind trails on water give you these things enroute as well as the drift and groundspeed you achieve. Excess X wind forecast requires an alternate be carried or holding if the period is suitable. (Forecast to improve by a certain time).  Nev