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).