Ground/Air Nautical Miles

[M.Lopresti]

I have never really seen the terms used with light aircraft flight
planning (G.A), only with heavy aircraft flight planning. Whats the
difference between GNM and ANM?

[John T Lowry]

"M.Lopresti" > wrote in message
...
>I have never really seen the terms used with light aircraft flight
> planning (G.A), only with heavy aircraft flight planning. Whats the
> difference between GNM and ANM?
>

A trip of 100 nm over the ground, in an hour, if into a 10 knot direct
headwind, would be a trip of 110 nm relative to still air. For logical
range calculations, the ANM concept is necessary.

John Lowry
Flight Physics

[David CL Francis]

On Wed, 3 Nov 2004 at 12:33:39 in message
. net>, John T Lowry
> wrote:
>A trip of 100 nm over the ground, in an hour, if into a 10 knot direct
>headwind, would be a trip of 110 nm relative to still air.

Are you sure about that?

Aircraft flying at 200k effective speed over the ground 190 knots
agreed?
Time taken = 100/190 = 0.5263157 hours
Effective distance at 200k TAS is 200*0.5263157 = 105 .26 nm

try a very low flight speed of 50k

Effective speed 50 -10 = 40k
Time take = 100/40 = 2.5 hours
effective distance = 50*2.5 = 125 nm

Try 1000k
effective speed over ground 990k
time taken = 100/990 = 0.10101010hours
effective distance = 1000*0.1010101 = 101.1nm

If you imagine that the headwind is the same as the aircraft speed than
it makes no progress at all and covers an infinite distance through the
air to cover that 100nm.
--
David CL Francis

[Raul Ruiz]

Divide by zero error! A division by zero is undefined, so I think
John's statement is correct. Even if you take the limit as the
effective speed goes to zero, the result is infinity, which is also,
theoretically, an undefineable number since it leads to inherent
contradictions in the strict sense. If we were to take ANM as a strict
mathematical concept, then I fear we would be laughed at. But
practically speaking, you're never going to have an effective ground
speed of 0 in an airplane.

[David CL Francis]

On Thu, 4 Nov 2004 at 18:23:24 in message
om>, Raul Ruiz
> wrote:
>Divide by zero error! A division by zero is undefined, so I think
>John's statement is correct. Even if you take the limit as the
>effective speed goes to zero, the result is infinity, which is also,
>theoretically, an undefineable number since it leads to inherent
>contradictions in the strict sense. If we were to take ANM as a strict
>mathematical concept, then I fear we would be laughed at. But
>practically speaking, you're never going to have an effective ground
>speed of 0 in an airplane.
>
That does not answer the fact that the original statement by John
appears to me to be wrong.

What is wrong with my calculations? I am perfectly willing to hear
corrections or that I was wrong.

A divide by zero error is a *computing* error that computers cannot
easily handle. There is nothing mathematically wrong with a result of
infinity.

In this case it merely represents the obvious fact that if you head into
a wind of the same strength as your cruising speed you will not get
anywhere. There is no contradiction in a result of infinity per se. Some
practical problems break down at that point. This one doesn't. The
meaning of infinity in this case is perfectly clear.

Finally a division of a real number by zero is *not* undefined, the
answer is unequivocally infinity. Zero divided by zero is undefined.

I await John's response.
--
David CL Francis

[Stealth Pilot]

On Fri, 05 Nov 2004 15:33:21 GMT, David CL Francis
> wrote:

>On Thu, 4 Nov 2004 at 18:23:24 in message
om>, Raul Ruiz
> wrote:
>>Divide by zero error! A division by zero is undefined, so I think
>>John's statement is correct. Even if you take the limit as the
>>effective speed goes to zero, the result is infinity, which is also,
>>theoretically, an undefineable number since it leads to inherent
>>contradictions in the strict sense. If we were to take ANM as a strict
>>mathematical concept, then I fear we would be laughed at. But
>>practically speaking, you're never going to have an effective ground
>>speed of 0 in an airplane.
>>
>That does not answer the fact that the original statement by John
>appears to me to be wrong.
>
>What is wrong with my calculations? I am perfectly willing to hear
>corrections or that I was wrong.
>
>A divide by zero error is a *computing* error that computers cannot
>easily handle. There is nothing mathematically wrong with a result of
>infinity.
>
>In this case it merely represents the obvious fact that if you head into
>a wind of the same strength as your cruising speed you will not get
>anywhere. There is no contradiction in a result of infinity per se. Some
>practical problems break down at that point. This one doesn't. The
>meaning of infinity in this case is perfectly clear.
>
>Finally a division of a real number by zero is *not* undefined, the
>answer is unequivocally infinity. Zero divided by zero is undefined.
>
>I await John's response.

I cant believe that you are asking this.
you always use the airspeed corrected for wind to determin time
enroute so that you can then determin the actual fuel consumed for the
leg.
John's response was correct.
Stealth Pilot

[Raul Ruiz]

Brush up on your math...
http://www.math.utah.edu/~alfeld/math/0by0.html

[Richard Cochran]

David CL Francis > wrote in message >...
> On Wed, 3 Nov 2004 at 12:33:39 in message
> . net>, John T Lowry
> > wrote:
> >A trip of 100 nm over the ground, in an hour, if into a 10 knot direct
> >headwind, would be a trip of 110 nm relative to still air.
>
> Are you sure about that?
>
> Aircraft flying at 200k effective speed over the ground 190 knots
> agreed?
> Time taken = 100/190 = 0.5263157 hours
> Effective distance at 200k TAS is 200*0.5263157 = 105 .26 nm

What you say confirms what John T Lowry said. He said that if you
spend an hour taking that 100nm (measured on the ground) trip into
a 10nm headwind, you add 10nm to your total air distance travelled.
Your calculations show that if you spend approximately one-half
hour going into that headwind, you'll add approximately one half
that distance, or about 5 nm.

Actually, John's original statement could have been generalized to
say that a trip of X nm over the ground in an hour, if into a 10 knot
direct headwind, would be a trip of X+10 nm relative to still air.

It could be further generalized to say that a trip of X nm over the
ground in T hours, into a Y knot headwind, will be a trip of X + T*Y
nm relative to still air. Using your numbers, we get X=100, T=.526,
Y=10, X + T*Y = 105.26nm effective distance, just as you claim.

--Rich

[David CL Francis]

On Fri, 5 Nov 2004 at 11:16:17 in message
>, Todd Pattist
> wrote:

>David CL Francis > wrote:
>>That does not answer the fact that the original statement by John
>>appears to me to be wrong.
>
>It's not wrong.
>
Nice to meet you here again Todd. I agree I was wrong, in that the
problem he postulated was different from what I assumed. I think my
calculations were right though.

I apologise to those concerned

However John's actual statement now I read it more carefully seems to
imply that given the wind speed you must find the TAS at which you
must fly to get there in an hour!

Is this the calculation that is intended? Even more trivial than my
calculations!

John wrote:
"A trip of 100 nm over the ground, in an hour, if into a 10
knot direct headwind, would be a trip of 110 nm relative to
still air."

Thus we have an unknown cruise TAS cruise speed
Let that be V

We have a 100 nm distance and a head wind of 10k
We have a time of flight of exactly one hour

Therefore 100/(V-10)= 1

and V -10 = 100

it follows that V = 110k

So at a TAS of 110k you travel a ground distance of 100nm against a wind
of 10k and surprise, surprise you than fly 110 'air' nm

More or less self evident so I am unclear what that achieves?
>
>You're wrong, here's why:
>
>You wrote :
>
>"Aircraft flying at 200k effective speed over the ground 190
>knots Time taken = 100/190 = 0.5263157 hours
>Effective distance at 200k TAS is 200*0.5263157 = 105 .26
>nm"
>
That is still mathematically correct I hope?

>John assumed an airspeed that would take 1 hour exactly to
>fly 100nm in one hour into a 10 knot headwind. During that
>hour, the air moved 10 nm so the aircraft covered 110nm of
>air and 100 nm of ground.
>
So he did, but that means he is implying a cruise speed that will get
you there in one hour.

Perhaps I am naive but it seemed to me you needed to calculate the
effect of head winds on a given cruise speed not a cruise speed to give
constant time? So if your aircraft had to fly against a 50k wind it
simply has to increase its cruise speed to 150k and it covers a 100nm in
one hour just the same. Is that useful thing to know? In that case it
is of course true that the aircraft would have covered 150 'air' miles.

>You assumed a speed that would take 1 hour to fly 100nm in
>no wind, and then calculated the time. (actually you chose
>200 knots, I'm not sure why). The assumptions were
>different. For John's case, the aircraft was not flying 100
>knots - it was flying at 110 knots and covered 110 air nm
>and 100 ground nm.
>
I chose three different speeds I believe, 200k, 50k and 1000k just to
show the differences.

I apologise again to those concerned for my error in reading the
original statement..

More interesting would be to know the galls per hour consumed at various
speeds and then create a table of cruise speeds against head wind
components (Positive or negative) and then determine the best cruise
speed for each wind speed for minimum Gallons per mile perhaps?

--
David CL Francis

[Jim Weir]

Not to complex the issue up, but you also have to do a table for various
altitudes - head/tailwinds - power settings in the data set. I've done this for
the 182; given Excel and a rainy Saturday, it wasn't too hard.

Jim



David CL Francis >
shared these priceless pearls of wisdom:


->More interesting would be to know the galls per hour consumed at various
->speeds and then create a table of cruise speeds against head wind
->components (Positive or negative) and then determine the best cruise
->speed for each wind speed for minimum Gallons per mile perhaps?



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Kevin Darling]

David CL Francis > wrote in message >...
> On Wed, 3 Nov 2004 at 12:33:39 in message
> . net>, John T Lowry
> > wrote:
> >A trip of 100 nm over the ground, in an hour, if into a 10 knot direct
> >headwind, would be a trip of 110 nm relative to still air.
>
> Are you sure about that?
> Aircraft flying at 200k effective speed over the ground 190 knots
> agreed?
> Time taken = 100/190 = 0.5263157 hours
> Effective distance at 200k TAS is 200*0.5263157 = 105 .26 nm

I'm no expert, but I think you misread and overanalyzed his statement
<grin>.

He said the 100nm trip was actually made in 1 hour while into a 10kt
headwind. Therefore the effective speed was 110kts, and the effective
distance (which is the point of ANM) was 110nm in that 1 hour.

ANM is sometimes used to compute the theoretical range of an aircraft.
For example, you fly a prototype jumbo jet from NYC to Paris, and it
took X thousand pounds of fuel. But after you add in the headwind x
time, then you can figure out the total ANM that it it went, and thus
compute its range or fuel usage/nm.

Kev

[Stealth Pilot]

On Fri, 05 Nov 2004 22:14:57 GMT, David CL Francis
> wrote:

>On Fri, 5 Nov 2004 at 11:16:17 in message
>, Todd Pattist
> wrote:
>
>>David CL Francis > wrote:
>>>That does not answer the fact that the original statement by John
>>>appears to me to be wrong.
>>
>>It's not wrong.
>>
>Nice to meet you here again Todd. I agree I was wrong, in that the
>problem he postulated was different from what I assumed. I think my
>calculations were right though.
>
>I apologise to those concerned
>
>However John's actual statement now I read it more carefully seems to
>imply that given the wind speed you must find the TAS at which you
>must fly to get there in an hour!
>
>Is this the calculation that is intended? Even more trivial than my
>calculations!
>
>John wrote:
>"A trip of 100 nm over the ground, in an hour, if into a 10
>knot direct headwind, would be a trip of 110 nm relative to
>still air."
>
>Thus we have an unknown cruise TAS cruise speed
>Let that be V
>
>We have a 100 nm distance and a head wind of 10k
>We have a time of flight of exactly one hour
>
>Therefore 100/(V-10)= 1
>
>and V -10 = 100
>
>it follows that V = 110k
>
>So at a TAS of 110k you travel a ground distance of 100nm against a wind
>of 10k and surprise, surprise you than fly 110 'air' nm
>
>More or less self evident so I am unclear what that achieves?
>>
>>You're wrong, here's why:

you're still wrong and that is why you're not achieving anything.
in the real world your cruise speed remains constant so what happens
is that the 110 nautical miles that the wind makes the 100 miles seem
like, takes longer to fly. engine running for longer equals more fuel
burn from the fixed tankage in the aircraft hence the need to pre calc
the usage and plan for it.

if you are actually a pilot you are an accident waiting to happen.
Stealth Pilot

[David CL Francis]

On Fri, 5 Nov 2004 at 09:44:49 in message
. com>, Raul Ruiz
> wrote:
>Brush up on your math...
>http://www.math.utah.edu/~alfeld/math/0by0.html
>
I may be out on limb here with modern high school math but I don't
really agree with everything there! Perhaps it is my great age! I try to
learn form what people tell me but it gets harder and harder. :-(

(Infinity + infinity) = infinity so I agree you cannot just subtract one
of them each side and say infinity = 0 !!!

What is (1 + 1/n)^n as n tends to infinity? (Clue: it's a very
important number - assuming I have not screwed up that expression at my
great age.)

As I understand it only under very special circumstances can infinities
can be cancelled out. But it is done in some esoteric equations.

What is tan(Pi/2)? Better still plot tan(theta).

Of course infinity cannot be treated as an ordinary number but it still
'exists' and you can compute larger and larger numbers as long as you
like.

What I did was to plot three points on a function which at one point
tends or goes to infinity.

Do you agree that 20/b gets larger and larger as b gets smaller and
smaller and that there is no point at which you can say that ends? I
can say with confidence that 20/0 is infinity and I can go on from that
to say that 20/0 = 40/0. What I cannot do is to infer from that that 20
= 40. But that is the nature of infinity. I know that dividing both
sides of equation by zero cannot be done with impunity either. I agree
that you cannot place a value on (infinity * 0) but I didn't want to do
that.

Let a = b
multiply both sides by b a*b = b^2
subtract a^2 from both sides a*b - a^2 = b^2 - a^2
therefore a*(b - a) = (b + a)*(b - a)
cancel (b - a) then a = b + a
but a = b therefore 1 = 2

But I expect you all know that one!

It's all good fun!
--
David CL Francis

[Jose]

> Of course infinity cannot be treated as an ordinary number but it still
> 'exists' and you can compute larger and larger numbers as long as you
> like.

Infinity is not a number. Because of this, when you get infinity as an answer, final or intermediate, you need to look closer. That said...

There is more than one size of infinity. Consider for example the positive integers and the odd positive integers. Obviously the set that is missing all the even integers has to be smaller. But it ain't so. You can pair each member of one set
with a member of the other set, and you'll never run out.

1..2
2..4
3..6
etc.

Ok, so much for that. What about fractions? There have to be more fractions than integers, because the fractions include the integers (6/3 is just another way of spelling 2). Let's arrange a grid however:
(note - at this point you'll probably want a fixed spacing font to see the grid)

* 1 2 3 4
1 1/1 1/2 1/3 1/4 ...
2 2/1 2/2 2/3 2/4 ...
3 3/1 3/2 3/3 3/4 ...
4 4/1 4/2 4/3 4/4 ...
....

This chart has to have all the fractions in it. And all the integers are listed in the column to the left, going down. Each row has an infinite number of fractions in it, so there just =have=to= be more fractions than integers. Well, no. (and it
has nothing to do with the fact that 2/1 is the same as 4/2)
Consider a path that starts with 1/1, and goes diagonally up right as far as it can (which isn't far at all!) then goes to the next diagonal down, and the next diagnoal up, zigzagging along, until it reaches the end (which is, of course, never). It
would cover (and I've paired them with integers starting with 1, below)
1/1 1/2 2/1 3/1 2/2 1/3 1/4 2/3 3/2 4/1 ...
1 2 3 4 5 6 7 8 9 10 ...

I'll never run out, and I'll never miss a beat. There must be the =same= number of fractions as there are integers.

Ok, we get three strikes in baseball, I get three ups here. Lets look at all the real numbers beween 0 and 1 and try to list them. They are listed as infinite decimals,
though some of them may end in lots of zeros - i.e. .5 is the same as .500000.... (and also .4999999..., which I won't get into here)

Here's my list. Itegers on the left, decimals on the right (in no particular order):

1 .348791037984....
2 .500000000000....
3 .000023416898....
4 .142857142857....
5 .141592653589....
6 .414213562373....
.... ...

No matter what I do, I can't list all the decimals on the right, and not because I can't afford the paper. However the list is created (and I have not put them in an order for several reasons), there is always at least one number that's not on the
list. Create it thusly: Write a decimal point and then take the first decimal place of the first number on the list, and write it down. Take the second decimal digit of the second number and write it down... take the nth decimal digit of the nth
number on the list.. and write it down... (see below)

..300893...

Now, just below it write a number whose digits differ in every place.

..411904

That number IS NOT ON THE LIST! ("Sure it is... it's the 52342th one, you must have missed it." "nope, the 52342nd digit is different." "oh yeah... oh wait, here it is, it's the 230498103984th one on the list." "nope... "

So, there are more real numbers between zero and one than there are integers! There are at least two sizes of infinity... the "original size" and the "giant size". :)

(actually, there are an infinite number of sizes of infinities, but that step is less mind boggling than the first one)

So, what does this have to do with aviation? Well, it will give you something to ponder on those long cross countries, it will explain why your fuel calculations were a bit off in the headwind (Oh, it must have been a big infinity in the
calculations instead of a little one), and it will give you something to impress the girls with when a pilot certificate doesn't do the trick.

Ok, maybe not. But it's still interesting. :)

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

[Blanche]

Jose > wrote:
>> Of course infinity cannot be treated as an ordinary number but it still
>> 'exists' and you can compute larger and larger numbers as long as you
>> like.
>
>Infinity is not a number. Because of this, when you get infinity as an

Actually, in the world of digital computers, infinity *is* a finite
number.

(*evil laugh*)

[David CL Francis]

On Sat, 6 Nov 2004 at 22:00:32 in message
>, Stealth Pilot
> wrote:

>>So at a TAS of 110k you travel a ground distance of 100nm against a wind
>>of 10k and surprise, surprise you than fly 110 'air' nm
>>
>>More or less self evident so I am unclear what that achieves?
>>>
>>>You're wrong, here's why:
>
>you're still wrong and that is why you're not achieving anything.
>in the real world your cruise speed remains constant so what happens
>is that the 110 nautical miles that the wind makes the 100 miles seem
>like, takes longer to fly. engine running for longer equals more fuel
>burn from the fixed tankage in the aircraft hence the need to pre calc
>the usage and plan for it.
>

No one disputes that statement of the obvious I would guess. Anyway as
far as I know you slightly adjust your cruise speed according to the
situation. That wasn't what anyone was discussing as far as I can see.
Perhaps you could tell me what I was trying to achieve as you seem to
know better than I do? On second thoughts don't bother.

>if you are actually a pilot you are an accident waiting to happen.
>Stealth Pilot
>
I'm not, just an elderly aeronautical engineer, so that's all right
then!
--
David CL Francis

[David CL Francis]

On Fri, 5 Nov 2004 at 14:40:51 in message
>, Kevin Darling
> wrote:
>David CL Francis > wrote in message
>...
>> On Wed, 3 Nov 2004 at 12:33:39 in message
>> . net>, John T Lowry
>> > wrote:
>> >A trip of 100 nm over the ground, in an hour, if into a 10 knot direct
>> >headwind, would be a trip of 110 nm relative to still air.
>>
>> Are you sure about that?
>> Aircraft flying at 200k effective speed over the ground 190 knots
>> agreed?
>> Time taken = 100/190 = 0.5263157 hours
>> Effective distance at 200k TAS is 200*0.5263157 = 105 .26 nm
>
>I'm no expert, but I think you misread and overanalyzed his statement
><grin>.
>
Your right - I did. See other posts.

>He said the 100nm trip was actually made in 1 hour while into a 10kt
>headwind. Therefore the effective speed was 110kts, and the effective
>distance (which is the point of ANM) was 110nm in that 1 hour.
>
>ANM is sometimes used to compute the theoretical range of an aircraft.
> For example, you fly a prototype jumbo jet from NYC to Paris, and it
>took X thousand pounds of fuel. But after you add in the headwind x
>time, then you can figure out the total ANM that it it went, and thus
>compute its range or fuel usage/nm.
>
That makes sense.
--
David CL Francis

[David CL Francis]

On Sat, 6 Nov 2004 at 18:38:22 in message
>, Jose
> wrote:
>That number IS NOT ON THE LIST! ("Sure it is... it's the 52342th one, you must have missed it." "nope, the 52342nd digit is different." "oh yeah...
>oh wait, here it is, it's the 230498103984th one on the list." "nope... "
>
>So, there are more real numbers between zero and one than there are integers! There are at least two sizes of infinity... the "original size" and the
>"giant size". :)
>
>(actually, there are an infinite number of sizes of infinities, but that step is less mind boggling than the first one)

That was fascinating and I enjoyed it but I do have trouble with the
concept of different 'sizes' of infinity although I feel sure they
exist. 0r do they? What do I mean by 'exist' anyway? :-)

I feel a bit like the definition of the size of space in the
'Hitchhiker's Guide to the Galaxy'. "Space is big!' If you think its a
long way to the corner shop..."

I can't remember it properly!

Thanks
--
David CL Francis

[David CL Francis]

On Sat, 6 Nov 2004 at 13:49:45 in message
>, Blanche >
wrote:
>Jose > wrote:
>>> Of course infinity cannot be treated as an ordinary number but it still
>>> 'exists' and you can compute larger and larger numbers as long as you
>>> like.
>>
>>Infinity is not a number. Because of this, when you get infinity as an
>
>Actually, in the world of digital computers, infinity *is* a finite
>number.
>
No, it just needs a computer memory of infinite size to display it and I
guess an infinite time to move the bits into this very large register.

>(*evil laugh*)
>
(*Hysterical laugh*)
--
David CL Francis

[Jose]

>
> That was fascinating and I enjoyed it but I do have trouble with the concept of different 'sizes' of infinity although I feel sure they exist. 0r do they? What do I mean by 'exist' anyway? :-)

Infinities (it works for finites too) are compared by attempting a one to one comparison between their elements. If one can achieve this, then they are the same "size". If it is impossible to achieve this, then one of them is "bigger".

The number of errors that can be made is bigger than the number of people.
The number of ways to skin a cat is bigger than the number of cats.
:)
There are actually an infinite number of sizes of infinity. The best way to think of an infinity is that it's the size of a set that contains all the elements. For example, the "size" (quantity of elements) that a set containing all the integers is
infinite. It is however smaller than the set of real numbers between zero and one, as shown in my original post. More generally, the quantity of subsets of an infinite set is bigger than the set being subsetted (to coin a word). (a subset is a set
which contains "some" of the elements of the original set, and no other elements, where "some" could be "all" or could be "none". Sets are designated (sometimes) by listing their elements inside curly braces; a few (i'll show three) subsets of the
days of the week are {sunday} and {tuesday, thursday, friday} and {} (that last one being the empty, or "null" set).

So, the set of positive integers ( {1,2,3,4,...} ) is not as large as the set of subsets of the positive integers ( {}, {1}, {2}, {1,2}, {1,2,3,4}, {8, 9, 423}, {500}, ... )
Note that it is perfectly fine for a set to contain sets as elements. Don't confuse a set with an element however: 1 is different from {1}. "Monday" is different from "the SET of days between Sunday and Tuesday". A car (something you can drive)
is different from "car" (the word describing something you can drive).

Ceci n'est pas une pipe.

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

[Jose]

>
> Actually, in the world of digital computers, infinity *is* a finite
> number.

No. The real "infinity" is the number of bugs in Microsoft programs. The "finite, computer infinity" is the number of bugs they will fix.

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

[Stealth Pilot]

On Sun, 07 Nov 2004 00:47:22 GMT, David CL Francis
> wrote:

>On Sat, 6 Nov 2004 at 22:00:32 in message
>, Stealth Pilot
> wrote:
>
>>>So at a TAS of 110k you travel a ground distance of 100nm against a wind
>>>of 10k and surprise, surprise you than fly 110 'air' nm
>>>
>>>More or less self evident so I am unclear what that achieves?
>>>>
>>>>You're wrong, here's why:
>>
>>you're still wrong and that is why you're not achieving anything.
>>in the real world your cruise speed remains constant so what happens
>>is that the 110 nautical miles that the wind makes the 100 miles seem
>>like, takes longer to fly. engine running for longer equals more fuel
>>burn from the fixed tankage in the aircraft hence the need to pre calc
>>the usage and plan for it.
>>
>
>No one disputes that statement of the obvious I would guess. Anyway as
>far as I know you slightly adjust your cruise speed according to the
>situation. That wasn't what anyone was discussing as far as I can see.
>Perhaps you could tell me what I was trying to achieve as you seem to
>know better than I do? On second thoughts don't bother.
>
>>if you are actually a pilot you are an accident waiting to happen.
>>Stealth Pilot
>>
>I'm not, just an elderly aeronautical engineer, so that's all right
>then!

thats ok, you make comments which one becomes attuned to over the
years as indicating a lack of knowledge at the level expected for
licencing. there was a question in my mind as to what your background
was. (at least you arent a precocious 14 yr old :-) )

you dont slightly adjust your cruise speed as you suggest. in the real
world you are cruising at the maximum continuous rpm that the engine
is capable of, that pretty well defines your cruise speed.

the navigation problem is caused by the wind is in two parts.
first: how much angle do you need to lay off into wind so that you get
blown off course by the wind back on to your intended track.
(otherwise you would never reach your destination) you solve this with
the speed vectors triangle on the graphical side of the E6B whiz
wheel.
Second: you determine the effect on your speed over the ground that
any headwind or tailwind component has, then from the resultant ground
speed and the actual distance you work out how long it will take to
fly the leg. your fuel consumption at cruise is a simple litres per
hour figure. litres per hour times the time aloft gives you the fuel
requirement. you work out the ground speed as part of the speed
vectors triangle then you take the value derived and use it on the
slide rule side of the E6B to work out time and then fuel needed in 2
calcs.

when you sit an exam on navigation quite often the question is simply
how much fuel will the flight take given a wind of XX knots from
XXXdegrees, cruise speed is XXX knots with a fuel flow of XX litres
per hour. takeoff from A, tracking via waypoints B and C to
destination D as marked on the map.
it is a sucker question :-) because you can only give the answer by
fully calculating the effect of wind on each individual leg.

btw I *have* tried to increase straight and level cruise on one
occasion by firewalling the throttle for over half an hour. I ended up
still being the original calculation past last light. the difference
was imperceptible.

Stealth (ask away on the nav questions) Pilot

[David CL Francis]

On Mon, 8 Nov 2004 at 23:02:55 in message
>, Stealth Pilot
> wrote:
>
>thats ok, you make comments which one becomes attuned to over the
>years as indicating a lack of knowledge at the level expected for
>licencing. there was a question in my mind as to what your background
>was. (at least you arent a precocious 14 yr old :-) )
>
LOL

>you dont slightly adjust your cruise speed as you suggest. in the real
>world you are cruising at the maximum continuous rpm that the engine
>is capable of, that pretty well defines your cruise speed.
>
You surprise me. Is that why ranges and fuel consumption are quoted for
different cruise power settings for many aircraft?

Lets take a review of the Diamond DA42 Twin Star

Cruise 90% @ 12,500ft 201 knots
Cruise 75% @ 10,000ft 181 knots

Range 60% standard tanks 1.061 nm
Range super long at 110 knots 2,063 nm

Seems that planning your cruise power might be rather important to
whether or not you make it. Adjustment for wind showed also be in order.
The report does not mention the likely range at 201 knots but I have a
*feeling* it will be even less.

Endurance is, naturally, even more sensitive to cruise power.

[Snip load of stuff that is teaching your grandmother to suck eggs]
>
>Stealth (ask away on the nav questions) Pilot

I don't think I will, thank you all the same. You know next to nothing
about me and if you assume that non pilots always know little about
aviation you are gravely mistaken. I have the greatest respect for many
pilots and I have known and still know a few whose words I hang on. That
does not mean that all pilots know more than I do about every subject.
--
David CL Francis

[David CL Francis]

On Mon, 8 Nov 2004 at 01:40:02 in message
>, Jose
> wrote:
>> That was fascinating and I enjoyed it but I do have trouble with
>>the concept of different 'sizes' of infinity although I feel sure they
>>exist. 0r do they? What do I mean by 'exist' anyway? :-)
>
>Infinities (it works for finites too) are compared by attempting a one
>to one comparison between their elements. If one can achieve this,
>then they are the same "size". If it is impossible to achieve this,
>then one of them is "bigger".
>
>The number of errors that can be made is bigger than the number of people.
>The number of ways to skin a cat is bigger than the number of cats.
>:)

I like it but neither the number of cats nor the number of people is
infinite! :-)

>There are actually an infinite number of sizes of infinity. The best
>way to think of an infinity is that it's the size of a set that
>contains all the elements. For example, the "size" (quantity of
>elements) that a set containing all the integers is infinite. It is
>however smaller than the set of real numbers between zero and one, as
>shown in my original post. More generally, the quantity of subsets of
>an infinite set is bigger than the set being subsetted (to coin a
>word). (a subset is a set which contains "some" of the elements of the
>original set, and no other elements, where "some" could be "all" or
>could be "none". Sets are designated (sometimes) by listing their
>elements inside curly braces; a few (i'll show three) subsets of the
>days of the week are {sunday} and {tuesday, thursday, friday} and {}
>(that last one being the empty, or "null" set).
>
>So, the set of positive integers ( {1,2,3,4,...} ) is not as large as
>the set of subsets of the positive integers ( {}, {1}, {2}, {1,2},
>{1,2,3,4}, {8, 9, 423}, {500}, ... )
>Note that it is perfectly fine for a set to contain sets as elements.
>Don't confuse a set with an element however: 1 is different from {1}.
>"Monday" is different from "the SET of days between Sunday and
>Tuesday". A car (something you can drive) is different from "car" (the
>word describing something you can drive).
>
>Ceci n'est pas une pipe.
>
Is that Maigret?

I think I've got it! By George I think I've got it Professor Higgins!
Once again where does it rain? No sorry that's not it. But there are
more raindrops than clouds and there is an infinite number of shapes and
sizes of clouds?

I do now understand the point that where you can map an infinite number
of sub objects to each integer it implies some substantial difference in
kind (scale? extent? Infinity? Whatever).

I liked the skinning a cat one!

Seriously thanks very much - I have made a step forward I think. However
what use you can make out of two sets where one of them is infinitely
greater than the 'smaller' infinite set escapes me at the moment.

Will it help with my dabbling in aerodynamics I wonder?
--
David CL Francis

[Peter Duniho]

I haven't been following this exchange closely, but one thing does stick
out...

"David CL Francis" > wrote in message
...
>>you dont slightly adjust your cruise speed as you suggest. in the real
>>world you are cruising at the maximum continuous rpm that the engine
>>is capable of, that pretty well defines your cruise speed.
>>
> You surprise me. Is that why ranges and fuel consumption are quoted for
> different cruise power settings for many aircraft?

While it is true that the most efficient speed (and thus best range) depends
on headwind or tailwind (fly faster in a headwind, slower in a tailwind, for
best economy), in practice pilots mostly ignore that. They aren't usually
flying at the best economy power setting, but rather are looking for best
speed and the power setting for best speed doesn't depend on winds aloft.

Of course, a concession is made to fuel economy, in that we rarely use the
true "best speed" power setting (which would be maximum continuous power).
That would use so much fuel as to generally be impractical.

But neither do we usually adjust the power setting (and thus cruise speed)
based on winds aloft. We just pick the power setting at the high end of the
published cruise power settings, and go with that. Alternatively, when
we're not in a hurry and we'd like to save on gas (applies only to owners
and those who rent "dry"), we'll select a lower power setting. But even
there, the winds aloft don't come into the equation for selecting the power
setting.

Mr. Pilot's response was entirely accurate, and no amount of poring through
aircraft manuals on your part will change that.

What your comment about "teaching your grandmother to suck eggs" means, I
have no idea. In the US, "go suck an egg" (and its variants) isn't a
friendly statement, and I didn't see anything in Mr. Pilot's post that would
have justified such a response. But who knows? Maybe in the UK, a
statement like that is considered harmless, for all I know. If not, it sure
seems out of character for you.

Pete

[Peter Duniho]

"Todd Pattist" > wrote in message
...
> It looks to me like Mr. Francis was "entirely accurate" and
> Mr. Pilot wrong. I don't run my engine at the "maximum
> continuous rpm that the engine is capable of."

Your operations are not relevant for what "most pilots" do. One sample does
not make any sort of generalization. The fact remains that most pilots use
the maximum cruise power setting for most operations. Mr. Pilot's statement
was certainly closer to the truth than any statement that claims pilots take
into account the wind when choosing their power setting (which was what
David said).

> None of that has anything to do with wind, but Mr. Francis
> is also right even if he was thinking of wind. Since my
> airplane is about as slow as they come, I sometimes choose
> speed during a headwind leg and efficiency during a downwind
> leg. The slower your cruise speed, the more it makes sense
> to do this. That's point 2.

"Sometimes"? Or "always"? I never said, nor do I believe Mr. Pilot
intended to say, that no one ever worries about fuel economy. The question
is what a typical operation is. And again, the typical operation does not
correlate wind, power setting, and fuel economy.

> I'd give Mr. Francis the nod for both points.

If you like.

Pete

[Jose]

>> Ceci n'est pas une pipe.
>>
> Is that Maigret?

Oui.

> But there are more raindrops than clouds and there is an infinite number of shapes and sizes of clouds?

Yes, and yes. And, oddly, there are (theoretically) more cloud shapes than there are real numbers. (the cardinality of the (which means, roughly, "number of") functions of real numbers is greater than the cardinality of the real numbers themselves.
A function is a set of real number pairs (+). Each such set is a subset of the real numbers. So the set of possible functions is essentially the set of subsets of real numbers. This has greater cardinality. ("There are more of them.") Which is
what you realize below when you say:

> I do now understand the point that where you can map an infinite number of sub objects to each integer it implies some substantial difference in kind (scale? extent? Infinity? Whatever).

It has a greater cardinality. But I'm talking about the case where the "map" is done by considering the set of subsets. Not every infinite map will give a greater cardinality. There are an infinite number of fractions with any given integer in the
numerator, but the number of fractions ("rational numbers") has the same cardinality as the integers ("there are just as many of them, no more, no less")

> Will it help with my dabbling in aerodynamics I wonder?

No. But it will help pass the time if you get bored with it. :)

Jose

(+) ok, they are ordered pairs such that the first element can only occur once in the set. For example:
{(2,4) , (3,5) , (4,5) } (the set containing the three ordered pairs (2,3), (3,5), and (4,5)) is a function, but
{(2,4) , (2,5) , (4,5) } (the set containing the three ordered pairs (2,3), (2,5), and (4,5)) is not. (It's a relation though)
Essentially, for each and every first element, there can only be one second element associated with it. Therefore, the cardinality of the function is equal to the cardinality of the first elements of the function. (there are exactly as many ordered
pairs in the function as there are distinct first elements in the function.)

--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.

[Stealth Pilot]

On Tue, 9 Nov 2004 13:37:00 -0800, "Peter Duniho"
> wrote:


>intended to say, that no one ever worries about fuel economy. The question
>is what a typical operation is. And again, the typical operation does not
>correlate wind, power setting, and fuel economy.
>
>> I'd give Mr. Francis the nod for both points.
>
>If you like.
>
>Pete
>
It depends entirely on the engine Pete.
I fly an O-200 in a homebuilt wittman W8 tailwind.
a very simple setup that obeys Lear's admonition.
.....and one that I wouldnt swap for a mooney :-)
Stealth Pilot

[Stealth Pilot]

On Tue, 09 Nov 2004 18:20:48 GMT, David CL Francis
> wrote:


>
>I don't think I will, thank you all the same. You know next to nothing
>about me and if you assume that non pilots always know little about
>aviation you are gravely mistaken. I have the greatest respect for many
>pilots and I have known and still know a few whose words I hang on. That
>does not mean that all pilots know more than I do about every subject.

what non pilots can never do is get the real relative importances of
each item sorted out. it is very often never written about because the
law actually isnt flexible enough that you can be honest at times.
by all means read all the theory but do try to get involved hands on
in the aviation environment so that you have a chance to develop some
practical experience and expertise.
you sound like the sort of guy who would enjoy the EAA chapter
environment.

come back to your writings and thoughts with some practical hands on
experience and you will surprise yourself at how subtly your writing
has changed because of that experience.

Stealth (get involved it will add years of pleasure to your life)
Pilot

[Morgans]

"Stealth Pilot" > wrote

> >
> It depends entirely on the engine Pete.
> I fly an O-200 in a homebuilt wittman W8 tailwind.
> a very simple setup that obeys Lear's admonition.
> ....and one that I wouldnt swap for a mooney :-)
> Stealth Pilot

What are your real world figures for empty weight, and gross for your W8?
It seems the figures I have seen place it ever so close to sport plane
status, except for the speed, but that could be taken care of with a climb
prop, I think.
--
Jim in NC


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[Stealth Pilot]

On Wed, 10 Nov 2004 16:44:30 -0500, "Morgans"
> wrote:

>
>"Stealth Pilot" > wrote
>
>> >
>> It depends entirely on the engine Pete.
>> I fly an O-200 in a homebuilt wittman W8 tailwind.
>> a very simple setup that obeys Lear's admonition.
>> ....and one that I wouldnt swap for a mooney :-)
>> Stealth Pilot
>
>What are your real world figures for empty weight, and gross for your W8?
>It seems the figures I have seen place it ever so close to sport plane
>status, except for the speed, but that could be taken care of with a climb
>prop, I think.

empty 362kg, (798lb)
max auw 590kg, (1300lb)

you'll find drawings for all but one of the mods on a link from my web
page www.members.iinet.net.au/~tailwind
the tank is 120litres (114 usable) which gives it 5 3/4 hours duration
to dry tanks, or realistically I can make a 300 mile leg into a 15
knot headwind and get there with lots in reserve.

Stealth Pilot

[David CL Francis]

On Tue, 9 Nov 2004 at 11:04:16 in message
>, Peter Duniho
> wrote:

>What your comment about "teaching your grandmother to suck eggs" means, I
>have no idea. In the US, "go suck an egg" (and its variants) isn't a
>friendly statement, and I didn't see anything in Mr. Pilot's post that would
>have justified such a response. But who knows? Maybe in the UK, a
>statement like that is considered harmless, for all I know. If not, it sure
>seems out of character for you.

Your guess was right it is a harmless statement in the UK. All it means
is you are telling me things not only that I know but so do many
others. Maybe it has gathered connotations that I am aware of. It was
not meant in anyway to be insulting

If I had considered it to be insulting I certainly would not have used
it. It is, I guess, sometimes a hint that someone is being a little bit
patronising.

Your interpretation is correct, I normally try very hard not to be rude,
judgmental or personal. Even with that relatively innocuous remark I
slipped a bit - sorry. I have learnt a little over the years about what
things not to say in America and conversely in the UK. I need to learn
more but to avoid any sort of phrases like that.

'Pass me a rubber please', would go totally unnoticed in the UK because
it means 'pass me an eraser'.
--
David CL Francis

[Morgans]

"Morgans"
>> >What are your real world figures for empty weight, and gross for your
W8?
> >It seems the figures I have seen place it ever so close to sport plane
> >status, except for the speed, but that could be taken care of with a
climb
> >prop, I think.
>
> empty 362kg, (798lb)
> max auw 590kg, (1300lb)
>
> you'll find drawings for all but one of the mods on a link from my web
> page www.members.iinet.net.au/~tailwind
> the tank is 120litres (114 usable) which gives it 5 3/4 hours duration
> to dry tanks, or realistically I can make a 300 mile leg into a 15
> knot headwind and get there with lots in reserve.
>
> Stealth Pilot

Fantastic! Finally, a sport design I could live with.

The W-10 is the current design, right? Where could one find plans for a
W-8?
--
Jim in NC


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[G.R. Patterson III]

Morgans wrote:
>
> The W-10 is the current design, right? Where could one find plans for a
> W-8?

You'd probably have to buy them from someone who's built the plane. Check EAA want
ads. Plans for the W-10 are available from Aircraft Spruce for $180.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

[Morgans]

"G.R. Patterson III" > wrote in message
...
>
>
> Morgans wrote:
> >
> > The W-10 is the current design, right? Where could one find plans for
a
> > W-8?
>
> You'd probably have to buy them from someone who's built the plane. Check
EAA want
> ads. Plans for the W-10 are available from Aircraft Spruce for $180.
>
> George Patterson

Yep, and like most designs, the W-10 has put on some weight, right out of
the ballpark for S.P.

What are the major differences that caused the W-10 put on weight? It is
hard to tell, but from reading personal web sites, it looks like around 350
gross lbs. Also, anyone have some hard numbers on stall speeds for the 8
and 10?
--
Jim in NC


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[Stealth Pilot]

On Fri, 12 Nov 2004 01:05:20 -0500, "Morgans"
> wrote:

>
>"G.R. Patterson III" > wrote in message
...
>>
>>
>> Morgans wrote:
>> >
>> > The W-10 is the current design, right? Where could one find plans for
>a
>> > W-8?
>>
>> You'd probably have to buy them from someone who's built the plane. Check
>EAA want
>> ads. Plans for the W-10 are available from Aircraft Spruce for $180.
>>
>> George Patterson
>
>Yep, and like most designs, the W-10 has put on some weight, right out of
>the ballpark for S.P.
>
>What are the major differences that caused the W-10 put on weight? It is
>hard to tell, but from reading personal web sites, it looks like around 350
>gross lbs. Also, anyone have some hard numbers on stall speeds for the 8
>and 10?

my tailwind plans are the original wittman drawings and have both the
W8 and W10 on them with the improved wing aerofoil.
I dont know what it would take to copy them.

stall speeds.
let me caveat these with mention that the bottom of the curve for a W8
is 65 knots and below that you can encounter some amazing sink rates.
takeoff safety speed is 57 knots btw. you wont enjoy flying around
near the stall.

at gross weight of 590 kg
zero flap = 46 knots
15 deg = 44 knots
30 deg = 42 knots
42 deg = 41 knots.

tracking across the nullabor plain with a vintage piper cub I tried
flying throttled back to 65 knots. the tailwind wallows around all
over the place. it really likes to cruise above 100 knots.

a chap in canada has a W8 with a C85 in it and his speeds are within a
knot of mine.
Stealth Pilot

[David CL Francis]

On Tue, 9 Nov 2004 at 11:04:16 in message
>, Peter Duniho
> wrote:
>What your comment about "teaching your grandmother to suck eggs" means, I
>have no idea. In the US, "go suck an egg" (and its variants) isn't a
>friendly statement, and I didn't see anything in Mr. Pilot's post that would
>have justified such a response. But who knows? Maybe in the UK, a
>statement like that is considered harmless, for all I know. If not, it sure
>seems out of character for you.

Just to add to your question about the above phrase I have been looking
it up and I found a large number of cases where it is being used in a
no-pejorative way. Many of them use it in an apologetic mode where they
are apologising in advance for what they are about to say. i.e. "I may
be teaching my grandmother to suck eggs but I still think that..."

The following is a reasonable history and explanation:

TEACHING ONE’S GRANDMOTHER TO SUCK EGGS

[Q] From Jonathan Downes: “I wonder if you would care to explain a
phrase in wide use but rather odd in its direct meaning: teaching your
grandmother to suck eggs? (This has been in use by my parents, both in
their 70s).”

[A] It does look odd, but its meaning is clear enough: don’t give
needless assistance or presume to offer advice to an expert. As that
prolific author, Anon, once wrote:

Teach not thy parent’s mother to extract
The embryo juices of the bird by suction.
The good old lady can that feat enact,
Quite irrespective of your kind instruction.

Many similar expressions have been invented down the years, such as
Don’t teach your grandmother how to milk ducks, and don’t teach your
grandmother to steal sheep. These have the same kind of absurd image as
the version you quote, which has survived them all. It was first
recorded in 1707 in a translation by John Stevens of the collected
comedies of the Spanish playwright Quevedo: “You would have me teach
my Grandame to suck Eggs”. Another early example, whimsically
inverted, is in Tom Jones by Henry Fielding, published in 1749: “I
remember my old schoolmaster, who was a prodigious great scholar, used
often to say, Polly matete cry town is my daskalon. The English of
which, he told us, was, That a child may sometimes teach his grandmother
to suck eggs”.

But the idea is very much older. There was a classical proverb A swine
to teach Minerva, which was translated by Nichola Udall in 1542 as to
teach our dame to spin, something any married woman of the period would
know very well how to do. And there are other examples of sayings
designed to check the tendency of young people to give unwanted advice
to their elders and betters.


--
David CL Francis

[Morgans]

"Stealth Pilot" > wrote

> my tailwind plans are the original wittman drawings and have both the
> W8 and W10 on them with the improved wing aerofoil.
> I dont know what it would take to copy them.

So are the plans that are now available now, contain the W-8 and the W-10?

> stall speeds.
> let me caveat these with mention that the bottom of the curve for a W8
> is 65 knots and below that you can encounter some amazing sink rates.
> takeoff safety speed is 57 knots btw. you wont enjoy flying around
> near the stall.
>
> at gross weight of 590 kg
> zero flap = 46 knots
> 15 deg = 44 knots
> 30 deg = 42 knots
> 42 deg = 41 knots.
>
> tracking across the nullabor plain with a vintage piper cub I tried
> flying throttled back to 65 knots. the tailwind wallows around all
> over the place. it really likes to cruise above 100 knots.
>
> a chap in canada has a W8 with a C85 in it and his speeds are within a
> knot of mine.
> Stealth Pilot

Thanks for the info. It does not matter if the stall is comfortable or not,
to fit in the new SP class. <g> I may have to look into the Tailwind more
seriously.
--
Jim in NC


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[G.R. Patterson III]

Morgans wrote:
>
> Thanks for the info. It does not matter if the stall is comfortable or not,
> to fit in the new SP class. <g> I may have to look into the Tailwind more
> seriously.

The tailwind is an experimental design and cannot be certified as a light-sport
aircraft. In addition, the maximum allowable stall speed of a SP class aircraft is 45
knots and the maximum speed in level flight cannot exceed 120 knots.

There's some performance data here
http://members.eaa.org/home/homebuilders/selecting/kits/Wittman%20Tailwind.html .
Based on the information in an article in the November issue of Sport Aviation, you
will not be allowed to fly a Tailwind on a Sport Pilot certificate, due to the top
speed of the plane.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

[Stealth Pilot]

On Sat, 13 Nov 2004 03:18:03 GMT, "G.R. Patterson III"
> wrote:

>
>
>Morgans wrote:
>>
>> Thanks for the info. It does not matter if the stall is comfortable or not,
>> to fit in the new SP class. <g> I may have to look into the Tailwind more
>> seriously.
>
>The tailwind is an experimental design and cannot be certified as a light-sport
>aircraft. In addition, the maximum allowable stall speed of a SP class aircraft is 45
>knots and the maximum speed in level flight cannot exceed 120 knots.
>
so you run it with a c65 and fine pitch prop, or a subaru conversion,
corvair conversion, rotax, jabiru 2200.
existing tailwinds are experimental but a new one modified for LSA
rules would be ok I think. raspet commented that the design required
65hp to fly.

re the current plans content for morgans. I dont know, I've never
sighted them. suggest asking aircraft spruce or jim irwin directly
what is actually on the plans
Stealth Pilot