Planning a flight

It depends on what airplane you are flying.
The slower the airplane, the longer the "point-of-no-return" zone in the
middle of the lake.
Are you flying into a headwind or tailwind?
Calculate your glide distance and airspeed to determine where you can
and cannot make it from.

"jsmith" wrote in message
...
It depends on what airplane you are flying.
The slower the airplane, the longer the "point-of-no-return" zone in the
middle of the lake.
Are you flying into a headwind or tailwind?
Calculate your glide distance and airspeed to determine where you can and
cannot make it from.

I will be in a Pa28-181 and I suspect flying west to east there might be a
tail wind as the norm but will just depend on the weather. In my OP I did
say the trip was in July.

Flying over long stretches of water does not bother me that much as it has
to be done in the UK if you want to go anywhere interesting (besides which
with AVGAS at $7.50 a gallon some routings are just not worth it).

My philosophy is that an airplane engine does not know whether it is over
land or water and as long as you can fly high enough then the margin of
safety increases.

It is why learning to trim the plane for best glide is a really useful
exercise and so important as is the ignoring the temptation to stretch the
glide out. Its worth studying the L/D diagrams to convince yourself that
it does not work.

Chris

What possible difference could it make whether you have a tailwind or
headwind en route?

Imagine one slightly less than your cruise speed. It pushes your point
of no return way out there. With a supersonic tailwind, the point of no
return could easily be before you even hit the lake.

While such extreme conditions are not likely, they do illustrate that
wind will make a difference, and it's worth figuring out how much
difference it will make, depending on speed and altitude.

Jose
--
Nothing is more powerful than a commercial interest.
for Email, make the obvious change in the address.

Imagine one slightly less than your cruise speed.

I was talking here, of course, about a headwind.

Jose
--
Nothing is more powerful than a commercial interest.
for Email, make the obvious change in the address.

On Wed, 23 Feb 2005 02:44:57 GMT, Jose
wrote:

What possible difference could it make whether you have a tailwind or
headwind en route?

Imagine one slightly less than your cruise speed. It pushes your point
of no return way out there. With a supersonic tailwind, the point of no
return could easily be before you even hit the lake.


Obviously, your point of "no return" comes sooner. At the same time,
the "point of making the opposite shore" comes earlier, so the risk is
essentially the same. The "window in which you are screwed" stays the
same, it just moves to a different place.



While such extreme conditions are not likely, they do illustrate that
wind will make a difference, and it's worth figuring out how much
difference it will make, depending on speed and altitude.

Jose


Wind only makes a difference in the direction you will turn, if and
when the worst happens. The risk is determined by the (a) gliding
capabilities of the aircraft, (b) your altitude, (c) the quality of
your planning for the occasion and (d) your skills in flying your new
glider.

Obviously, your point of "no return" comes sooner. At the same time,
the "point of making the opposite shore" comes earlier, so the risk is
essentially the same. The "window in which you are screwed" stays the
same, it just moves to a different place.

That's not the way I see it. With a =headwind= close to your cruise
speed, when you turn around you will be rushed home but if you continue
forward you will take almost forever to get across. So, the point of no
return is farther from your starting point. (you cover more distance
going back in the time it takes you to descend). The reverse is true
with a riproaring =tailwind=. If your tailwind is equal to your cruise
speed, the point of no return is right over your starting point. Faster
than your cruise speed, there is no point of no return - you'd never
make it back.

You are correct that the time to descend will be the same no matter what
the head or tail winds are. However, I do not agree that the time spent
in pucker factor territory is the same. Consider a tailwind that is
half the speed of light. You will be over your destination almost as
soon as you took off, and you won't have time to pucker, let alone make
a standard rate U-turn. With a headwind that is almost equal to your
cruise speed, you will remain in the pucker region almost forever,
assuming you can even get there before running out of fuel.

As to the position (on the ground) of this region, it may well stay the
same size. After all, it's just you flying through still air while the
earth moves underneath you at constant speed. It is good for flight
planning purposes to know (on the map) where you are screwed if the
pilot's cooling fan stops working, but the risk is proportional to time,
not distance. If the winds carry you over the terrible maw of death
quickly, you are less likely to fall into it.

Jose
--
Nothing is more powerful than a commercial interest.
for Email, make the obvious change in the address.

On Wed, 23 Feb 2005 13:34:24 GMT, Jose
wrote:

As to the position (on the ground) of this region, it may well stay the
same size. After all, it's just you flying through still air while the
earth moves underneath you at constant speed. It is good for flight
planning purposes to know (on the map) where you are screwed if the
pilot's cooling fan stops working, but the risk is proportional to time,
not distance. If the winds carry you over the terrible maw of death
quickly, you are less likely to fall into it.

Well, this is like saying that I reduce my chances of having any kind
of aircraft accident by flying less.

Nevertheless, a gliding radius is a gliding radius, and that radius is
moving along with the winds. When the engine quits, whether that wind
a moment ago was a tailwind or a headwind is irrelevant. If you don't
know where the edge of the radius is going to end up at the time you
reach the surface, that surface might be water, not land, when you get
there.

So you may be correct to say that short (tailwind) trips are less
hazardous than long (headwind) trips. Once the engine stops, however,
your chances of reaching land are proportional to your altitude and
L/D of your aircraft, and your flying skills, and knowledge of those
winds. You might be better off gliding straight ahead into a
headwind, or turning to a tailwind, or vice versa.

It would be good to have that figured out ahead of time.

Well, this is like saying that I reduce my chances of having any kind
of aircraft accident by flying less.

That's not what I had in mind. I was addressing the size of the pucker
area in more appropriate terms (minutes), and saying that that size does
depend on winds.

whether that wind
a moment ago was a tailwind or a headwind is irrelevant

.... true but what is relevant (and related) is whether it will continue
to be a headwind or tailwind. Granted the winds change with altitude as
you descend.

if you don't
know where the edge of the radius is going to end up at the time you
reach the surface, that surface might be water, not land, when you get
there.

True. (actually it might be water even if you do know... but presumably
you'd be more likely to turn in the right direction!)

Once the engine stops, however,
your chances of reaching land are proportional to [the situation]

Yes. I was addressing flight planning, and your contention that the
area of no (good) options is independent of winds. I claim that the
area location =is= dependent on winds, and the area's size in minutes is
also dependent on winds. The first is useful for flight planning (draw
a line on the chart) and the second is useful for a go/no-go decision.
One might be comfortable with a fifteen minute no-option time, but not
with a forty-five minute no-option time.

It would be good to have that figured out ahead of time.

Yep.

Jose
--
Nothing is more powerful than a commercial interest.
for Email, make the obvious change in the address.

On Wed, 23 Feb 2005 18:23:35 GMT, Jose
wrote:


Yes. I was addressing flight planning, and your contention that the
area of no (good) options is independent of winds. I claim that the
area location =is= dependent on winds, and the area's size in minutes is
also dependent on winds. The first is useful for flight planning (draw
a line on the chart) and the second is useful for a go/no-go decision.
One might be comfortable with a fifteen minute no-option time, but not
with a forty-five minute no-option time


The area in square miles that is available to you to glide to at any
given moment is independent of winds. It is an inverted cone around
your aircraft. The geographic center of this cone will be downwind of
the aircraft, but its area does not change. You can glide to the edge
of that cone, period. You can get farther in one direction (downwind)
than another, but that's merely a tradeoff, and you might not
necessarily strive for the furthest possible point (especially if it's
under water.)

The cone will move faster,as the aircraft moves faster over the
ground, so the cone will be completely surrounded by water (the "no
good option" time) for a shorter period, the greater the
groundspeed..

I don't know what you mean when you say the "area's size in minutes
is dependent on winds". One can only alter the distance one can
glide by using winds, by gliding in one direction or another. One
cannot alter the size of the area. What one gains in one direction,
he gives up in the other.

Can you guys continue this discussion in another thread and leave this one
to deal with the original post.

Chris
wrote in message
...
On Wed, 23 Feb 2005 18:23:35 GMT, Jose
wrote:


Yes. I was addressing flight planning, and your contention that the
area of no (good) options is independent of winds. I claim that the
area location =is= dependent on winds, and the area's size in minutes is
also dependent on winds. The first is useful for flight planning (draw
a line on the chart) and the second is useful for a go/no-go decision.
One might be comfortable with a fifteen minute no-option time, but not
with a forty-five minute no-option time


The area in square miles that is available to you to glide to at any
given moment is independent of winds. It is an inverted cone around
your aircraft. The geographic center of this cone will be downwind of
the aircraft, but its area does not change. You can glide to the edge
of that cone, period. You can get farther in one direction (downwind)
than another, but that's merely a tradeoff, and you might not
necessarily strive for the furthest possible point (especially if it's
under water.)

The cone will move faster,as the aircraft moves faster over the
ground, so the cone will be completely surrounded by water (the "no
good option" time) for a shorter period, the greater the
groundspeed..

I don't know what you mean when you say the "area's size in minutes
is dependent on winds". One can only alter the distance one can
glide by using winds, by gliding in one direction or another. One
cannot alter the size of the area. What one gains in one direction,
he gives up in the other.