Picking Optimal Altitudes

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

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 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




--
Remove "2PLANES" to reply.

"O. Sami Saydjari" wrote in message ...
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?

The 2 kts per 1000 feet seems about right. The speed increase is due
to the fact that the turbo allows the engine to maintain power output
at a much higher elevation than a normally aspirated engine. The
increased power output coupled with thinner air allows the plane to go
faster.

Generally speaking, the winds above 10k are out of the west, and can
be strong enough to negate the speed advantage of the turbo. On these
trips, it makes sense to fly lower. Going Eastbound, you will
generally want to fly high to take advantage of both the high TAS and
the large tailwinds.

There are exceptions however, so you need to look at the forecast and
PIREP'ed winds aloft as part of your flightplanning to decide whether
or not it makes sense to climb high.

However, you will find many times that having a turbo and oxygen are a
great advantage no matter what the winds aloft. Just last week, I was
on top of a rising cloud layer at 10,000 in my Cherokee, a smooth ride
and in the sun. (The clouds were ~9kft thick at my location.)
However, as I traveled North, I was to pass a weak cold front, and the
temps were already dropping. I considered climbing higher, but had
visions of my Cherokee struggling to outclimb iceladen clouds, and of
course the hypoxia issues as one continues climb... I ended up
descending and flew 2 hrs in bumpy, rainy IMC. Not much fun, but I
kept the OAT above zero and made it to my destination no problems.

If I had turbo and oxygen, I would have zipped up to 12,14,16,
whatever it took to clear the clouds, enjoyed a smooth ride home in
the sun, and an easy descent in the better weather at my destination.

-Nathan

"O. Sami Saydjari" wrote in message
...
When planning a flight against the wind, how to you pick the best
altitude when trying to minimize flight time?

You need to run the performance charts against some actual weather. Use
ADDS for wind and everything else. Up wind and downwind are completely
different exercises. Every day is different but patterns will quickly
develop with experience. The turbo changes things a bit. Hit the books
with some actual weather.

In article , "O. Sami Saydjari"
writes:

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?


Yes, but it is generally smoother up higher.

Chuck

In a previous article, said:
When planning a flight against the wind, how to you pick the best
altitude when trying to minimize flight time?

Since Santa was good to me and I now have the complete Sporty's Air Facts
on DVD, I've now seen Richard Collins say several times that he chooses
his altitude based on finding a smoother ride rather than a faster trip.
Of course, he's got a pressurized and turbo charged P-210, so he's got a
lot more choice of altitude than I do.


--
"The magic of usenet has never been its technology; and, only in part, its
reach. Its magic -- its power -- is based on the very real human connections
that form 'round its threads of conversation... the relationships that are
kindled, flamed and, on occasion, extinguished and mourned." -deCadmus

Lazy people (like me) ask their computer. FlightStar from Jepp has an
"optimize altitude" function that is pretty handy. Once it has downloaded
DUATs weather it will display groundspeed and fuel burn for all altitudes
and highlight the optimal flight level.

"O. Sami Saydjari" wrote in message
...
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