Flight Planning for Long Trips

"Andrew Sarangan" wrote:
One thing look for is the difference between great circle distance and
actual distance.

It's pretty rare that GC calculations become significant for the kinds of
flights most GA aircraft are capable of making.

I just worked a pretty extreme example: 45N/68W (roughly Bangor, ME) to
45N/92W (roughly Duluth, MN). This is about 1000 miles, beyond the range
of most of our aircraft. It's also a route parallel to the equator, and
further north than most of us fly. All of these are factors that increase
the GC error.

It works out to an initial heading of 279 (true), compared with the
Mercator rhumbline of 270. That's a pretty small difference, and almost
certainly other factors such as terrain, weather, airspace, and possible
alternates are going to be more important.

Put together a few fuel-bounded legs in a row, and then GC starts to become
important for the overall trip (assuming it's mostly east-west).

I programmed a HP 27S calculator for GC navigation. I put
in a departure and destination LAT/LON and it calculates the
CG distance in SM and NM, I input an estimated ground speed
out and back and it gives the equal time point in distance
and time. But I can also enter a series of LON points and
it calculates the LAT for each LON, very handy for reporting
points over-water. I have not gone to the trouble of making
the program "smart" in that I have to know and adjust
courses since the program measures courses east and west of
north.
It also calculates the difference between GC and rhumb line.


--
James H. Macklin
ATP,CFI,A&P

"Roy Smith" wrote in message
...
| "Andrew Sarangan" wrote:
| One thing look for is the difference between great
circle distance and
| actual distance.
|
| It's pretty rare that GC calculations become significant
for the kinds of
| flights most GA aircraft are capable of making.
|
| I just worked a pretty extreme example: 45N/68W (roughly
Bangor, ME) to
| 45N/92W (roughly Duluth, MN). This is about 1000 miles,
beyond the range
| of most of our aircraft. It's also a route parallel to
the equator, and
| further north than most of us fly. All of these are
factors that increase
| the GC error.
|
| It works out to an initial heading of 279 (true), compared
with the
| Mercator rhumbline of 270. That's a pretty small
difference, and almost
| certainly other factors such as terrain, weather,
airspace, and possible
| alternates are going to be more important.
|
| Put together a few fuel-bounded legs in a row, and then GC
starts to become
| important for the overall trip (assuming it's mostly
east-west).

Roy Smith wrote:
"Andrew Sarangan" wrote:
One thing look for is the difference between great circle distance and
actual distance.

It's pretty rare that GC calculations become significant for the kinds of
flights most GA aircraft are capable of making.

I just worked a pretty extreme example: 45N/68W (roughly Bangor, ME) to
45N/92W (roughly Duluth, MN). This is about 1000 miles, beyond the range
of most of our aircraft. It's also a route parallel to the equator, and
further north than most of us fly. All of these are factors that increase
the GC error.

It works out to an initial heading of 279 (true), compared with the
Mercator rhumbline of 270. That's a pretty small difference, and almost
certainly other factors such as terrain, weather, airspace, and possible
alternates are going to be more important.

Put together a few fuel-bounded legs in a row, and then GC starts to become
important for the overall trip (assuming it's mostly east-west).

I think you misunderstood my post. What I was saying that small jogs to
a route does not add much extra distance compared to a straight line
route. I was using the term great circle and straight line
interchangeably, which is true for short distances.

"Andrew Sarangan" wrote in message
oups.com...



I think you misunderstood my post. What I was saying that small jogs to
a route does not add much extra distance compared to a straight line
route. I was using the term great circle and straight line
interchangeably, which is true for short distances.


I agree with that.

Flying to St George, Utah, I can climb over the Las Vegas Class-B, or stay
at a lower altitude and jog around the south margin. The distance increase
in the jog around is only six miles. Fuel- and time-wise, considering the
extra climb, the jog comes out about the same. Most of the times, the winds
aloft make the decision for me.