Picking Optimal Altitudes

I travel about 8-10 thousand into the wind and 14-20 with the wind. I agree.
Usually the headwind increases faster than TAS with altitude. I travel 8-10
for safety--glide distance.



"Jeff" wrote in message
...
when I plan a flight against the wind (like a few days ago comming back
from
phoenix) I go with the altitude that gives me the best ground speed.
On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go
to
10500 for terrain and my GS went down to 117 kts., so I jumped back down
to
8500 when I had the chance.

Turbo airplanes take advantage of the thinner air up high is why they can
go
faster then normally aspirated planes. you maintain your full 200 HP up to
a
DA of 12,000 ft. So 12000 ft is where you start to lose horse power but
the
air is thinner allowing you a better TAS and if you play the winds right,
some really good ground speeds. stay low if you have a head wind, get up
high when you have a tail wind.

Sometimes, the wind down low will be higher then say around 10,000 or
12000
ft or about the same. If there is not much difference in the winds, I
would
select the higher altitude because of the thinnner air. Also you dont use
as
much fuel up high.


"O. Sami Saydjari" wrote:

When planning a flight against the wind, how to you pick the best
altitude when trying to minimize flight time?

If I read my performance charts correctly, my aircraft (Piper Turbo
Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
*true* airspeed for every 1000 feet you go up. Firstly, does that sound
about right to folks? I assume that this effect is from the decrease in
air friction at high altitudes (even though the prop also has less air
to "push on").

So, unless there is some other factor, I think this means that if the
winds increase at anything higher than 2 nts per 1000 feet, I am best
off staying at the Minimum Enroute Altitude. Is that right?

My experience thus far suggests that most of the time, the winds aloft
speed increase far faster then 2 nts per 1000 feet, so, in general, it
is unlikely that I will do much better than staying at the absolute
minimum altitude. Is that consistent with other folks' experience?

-Sami

I was thinking real hard about that glide distance the other day flying to
phoenix.
when passing over the colorado river area, I felt my plane kinda "surge", never
felt it before, I thought the engine was surging but didnt see any indications
on any of my instruments. I was looking around for a place to land and 8500 ft
just didnt look high enough at the time.
the trip was unevenful tho, I am thinking it was a gust of wind hitting me from
behind making the plane surge forward for a second.

Wyatt Emmerich wrote:

I travel about 8-10 thousand into the wind and 14-20 with the wind. I agree.
Usually the headwind increases faster than TAS with altitude. I travel 8-10
for safety--glide distance.

"Jeff" wrote in message
...
when I plan a flight against the wind (like a few days ago comming back
from
phoenix) I go with the altitude that gives me the best ground speed.
On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go
to
10500 for terrain and my GS went down to 117 kts., so I jumped back down
to
8500 when I had the chance.

Turbo airplanes take advantage of the thinner air up high is why they can
go
faster then normally aspirated planes. you maintain your full 200 HP up to
a
DA of 12,000 ft. So 12000 ft is where you start to lose horse power but
the
air is thinner allowing you a better TAS and if you play the winds right,
some really good ground speeds. stay low if you have a head wind, get up
high when you have a tail wind.

Sometimes, the wind down low will be higher then say around 10,000 or
12000
ft or about the same. If there is not much difference in the winds, I
would
select the higher altitude because of the thinnner air. Also you dont use
as
much fuel up high.


"O. Sami Saydjari" wrote:

When planning a flight against the wind, how to you pick the best
altitude when trying to minimize flight time?

If I read my performance charts correctly, my aircraft (Piper Turbo
Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
*true* airspeed for every 1000 feet you go up. Firstly, does that sound
about right to folks? I assume that this effect is from the decrease in
air friction at high altitudes (even though the prop also has less air
to "push on").

So, unless there is some other factor, I think this means that if the
winds increase at anything higher than 2 nts per 1000 feet, I am best
off staying at the Minimum Enroute Altitude. Is that right?

My experience thus far suggests that most of the time, the winds aloft
speed increase far faster then 2 nts per 1000 feet, so, in general, it
is unlikely that I will do much better than staying at the absolute
minimum altitude. Is that consistent with other folks' experience?

-Sami

Altitude is your friend. On the way to OSH last summer, we leveled off
at 10,000' (C172) after leaving BTV. A few minutes later, the engine
developed some serious roughness. It went away when I jammed the
mixture control in and pulled the carb heat. Then it came back. I was
about to declare an emergency when it cleared up for good. (I believe
that I had some water in the fuel that didn't hit the port until we were
in level cruise.) An event like that will certainly make you sit up
straight and start looking (my "copilot" had VERY wide eyes for a few
minutes). But at 10,000' (and my trusty handheld GPS), I had a couple
of airports within gliding distance (and lots of recently mowed hay
fields) to choose from. The remainder of the trip was uneventful (other
than the 2-day layover in Dayton to wait out the front).

For my IFR check ride, my DE asked me to plan a trip from CON (Concord,
NH) to HYA (Hyanis, MA). He asked why I selected 9000' feet for my
enroute altitude. Answer was, "In case I lose the engine." IMHO,
unless the headwinds are much stronger at 10-12K', I'd rather take a few
more minutes (OK, sometimes many more minutes) to get there, but have a
few more minutes and miles in case of an engine failure. My time is
just not that important.


Jeff wrote:
I was thinking real hard about that glide distance the other day flying to
phoenix.
when passing over the colorado river area, I felt my plane kinda "surge", never
felt it before, I thought the engine was surging but didnt see any indications
on any of my instruments. I was looking around for a place to land and 8500 ft
just didnt look high enough at the time.
the trip was unevenful tho, I am thinking it was a gust of wind hitting me from
behind making the plane surge forward for a second.

Wyatt Emmerich wrote:


I travel about 8-10 thousand into the wind and 14-20 with the wind. I agree.
Usually the headwind increases faster than TAS with altitude. I travel 8-10
for safety--glide distance.

"Jeff" wrote in message
...

when I plan a flight against the wind (like a few days ago comming back

from

phoenix) I go with the altitude that gives me the best ground speed.
On my way back from phoenix at 8500 ft I had a GS of 130 kts, I had to go

to

10500 for terrain and my GS went down to 117 kts., so I jumped back down

to

8500 when I had the chance.

Turbo airplanes take advantage of the thinner air up high is why they can

go

faster then normally aspirated planes. you maintain your full 200 HP up to

a

DA of 12,000 ft. So 12000 ft is where you start to lose horse power but

the

air is thinner allowing you a better TAS and if you play the winds right,
some really good ground speeds. stay low if you have a head wind, get up
high when you have a tail wind.

Sometimes, the wind down low will be higher then say around 10,000 or

12000

ft or about the same. If there is not much difference in the winds, I

would

select the higher altitude because of the thinnner air. Also you dont use

as

much fuel up high.


"O. Sami Saydjari" wrote:


When planning a flight against the wind, how to you pick the best
altitude when trying to minimize flight time?

If I read my performance charts correctly, my aircraft (Piper Turbo
Arrow III -- service ceiling 20,000 ft) seems to gain about 2 nts of
*true* airspeed for every 1000 feet you go up. Firstly, does that sound
about right to folks? I assume that this effect is from the decrease in
air friction at high altitudes (even though the prop also has less air
to "push on").

So, unless there is some other factor, I think this means that if the
winds increase at anything higher than 2 nts per 1000 feet, I am best
off staying at the Minimum Enroute Altitude. Is that right?

My experience thus far suggests that most of the time, the winds aloft
speed increase far faster then 2 nts per 1000 feet, so, in general, it
is unlikely that I will do much better than staying at the absolute
minimum altitude. Is that consistent with other folks' experience?

-Sami




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