How high?

I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

In a previous article, "John Harlow" said:
I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

I want to be at least 4,000 feet, because it's quieter up there - there's
very little VFR traffic, and the airliners are only passing through. If
there is a few-to-scattered layer, I want to be above it because the air
is smoother. Before I was instrument rated, I'd have to be careful it
didn't turn into a broken layer when I wasn't paying attention. I don't
like to fly above 10,000 because of the lack of oxygen, although I got up
to 12,500 looking for a way though the storms coming back from Oshkosh.
So generally I end up at 6,000 (or 6,500 if VFR) going west and 9,000 (or
9,500 if VFR) going east.


--
Paul Tomblin http://xcski.com/blogs/pt/
I'm just waiting for the day that someone decides that "ignorant moron" is
an ethnic group, and thus cannot be discriminated against.
-- Christian Wagner

In article ,
"John Harlow" wrote:

I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

Some rules of thumb:

A normally aspirated (i.e. no supercharger) engine such as found in a
172 will be running at about 65% power at 7000 density altitude with
wide open throttle. Above that, you will have less power as you climb
higher. Thus, there's usually not a lot of reason to fly much higher
than 7500 MSL, unless terrain forces you higher.

Below 3000 AGL, there tends to be lots of random traffic: people
practicing maneuvers or instrument approaches, and flights entering or
departing traffic patterns. Staying above 3000 AGL keeps you out of the
worst of that. Below 3000, you also run into Class D airspaces, and
there tends to be more turbulence (especially over rough terrain).
Thus, there's usually not a lot of reason to cruise below 3000 AGL.

It's usually not worth spending more than 1/3 of the trip time climbing.

Consider radar and radio coverage. Below 3000 AGL, both tend to be
spotty if you're not within about 10-20 miles of the charted boundary of
a Class B or C airspace (or TRSA).

Our plane (Cherokee 235 -- normally aspirated 6-cylinder O-540) runs best
(highest speed, lowest, most even EGTs and CHTs, with lowest fuel burn)
between 4500 and 6500 feet.

These altitudes work fine here in the Midwest.

We also like it there because it's usually smoother, and there is far less
traffic. We're well above the guys working the pattern, and well below the
"big boys" in the airliners.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"
"John Harlow" wrote in message
...
I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before
returns
diminish?

John Harlow wrote:

I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

A lot depends on whether I'm alone or not. It's also the case that the various
airspace restrictions around here do a lot more to determine my enroute altitude
than anything else until I get south of the DC mess.

If I'm alone and have strong headwinds, I'll stay down as low as 600' AGL to make
time. If my wife is in the plane, I will go as high as is necessary to eliminate
turbulence (if this is possible). I will go as high as 9,500' to make the best use
of a tailwind, but I do not like to fly much higher than that, since flying higher
makes me drowsy and leaves me with a headache. I have gone as high as 11,500 to
get over a class-B.

All my flying is done in the eastern half of the country without oxygen on board.
If I had to deal with mountains higher than the Appalachians, it would be a
different story.

George Patterson
Love, n.: A form of temporary insanity afflicting the young. It is curable
either by marriage or by removal of the afflicted from the circumstances
under which he incurred the condition. It is sometimes fatal, but more
often to the physician than to the patient.

In article ,
"G.R. Patterson III" wrote:

John Harlow wrote:

I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

A lot depends on whether I'm alone or not. It's also the case that the
various
airspace restrictions around here do a lot more to determine my enroute
altitude
than anything else until I get south of the DC mess.

If I'm alone and have strong headwinds, I'll stay down as low as 600' AGL to
make
time. If my wife is in the plane, I will go as high as is necessary to

600 feet AGL for cruise? Not a lot of think/plan time if your engine
fails!

Chris,

600 feet AGL for cruise? Not a lot of think/plan time if your engine
fails!


Depends on terrain. If it's an all flat agricultural area, it's not a
big problem. Also, engine failures for mechanical reasons are not that
common. A calculated risk - like everything in flying (and life).

--
Thomas Borchert (EDDH)

"John Harlow" wrote in message
...
I'd like to get input on opinions on the "best" VFR altitude for a route.

It depends on a variety of factors.

As has been pointed out, you get the most power with the least drag at
around 7000' MSL or so. So for a normally aspirated engine, that's a nice
target.

But for short flights, it may be a waste of time to climb that high. For
flights starting at high altitude, you may find 7000' is too low to keep you
out of local traffic and away from terrain. If there are strong winds going
in your direction, you may want to fly higher. If there are strong winds
going opposite your direction, you may want to fly lower. If it's a hot,
sunny day you may find it's bumpy down low and will want a higher cruise
altitude. If it's a windy, turbulent day, you may find the air smoother at
the middle altitudes.

You get the idea. Each flight is different. Rules of thumb are nice, but
you need to be considering all the factors anew each flight.

I have a turbocharged aircraft, so generally speaking, higher is better.
However, I still have to deal with headwinds and turbulence. But the winds
aloft forecast isn't reliable enough to use it to pick a cruising altitude.
So typically what I do is choose a cruising altitude independent of the
winds aloft forecast. Then I just see how things are in flight. I gain
about a knot in true airpspeed for every 1000' I climb, so that gives me a
guideline for how much the winds need to change for it to be worth picking a
new cruising altitude. Of course, if the ride is bumpy, I generally opt for
a slower but smoother flight.

For this sort of "wait and see" approach, it certainly helps to have good
climb rates at pretty much any altitude (I'm still getting 500-600 fpm at
16,000' or so, and much better lower...when I'm flying at 10,000' +/- a few
thousand, it only takes a few minutes to change altitude to a new,
significantly different altitude). It would be less practical with a
normally aspirated engine.

Pete

Except in high winds aloft or bad turbulence, I have found that flying
low (safety permitting) generally results in the most optimum
solution. Climbing higher for better tailwind doesn't buy more than a
few minutes. Of course, the ratio of climb time to cruise time has a
big effect too. There are too many variable to make a rule of thumb.
What I do is try a few altitudes on DUATs flight planner and pick the
lowest altitude that seems reasonable.



"John Harlow" wrote in message ...
I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

If I am flying a long trip (several hours), I will go up 2000' and see
if I get an improvement in groundspeed. If I do, I stay up there and
my try another 2000'. Don't forget you burn less gas per mile up high,
so even if you just go the same speed, you are ahead. Sometimes I call
Fligh****ch and ask them for the winds aloft forecasts so I can plan
my altitude. In the summer, if I go up high enough, sometimes I can
get above the turbulence. But then you may slow down so you have the
age old turbulence vs airspeed tradeoff question.

If I am going west, leave in the morning, come back in the evening
will get me less headwind west and more tailwind east as winds
increase as the day goes on, statistically. Going east, leave late in
the day and come back the next day, if possible.

I do believe I have "outflown" the wind, that is, I have had more
tailwinds than headwinds due to being able to pick times and altitudes
flown.

Although there is software that calculates best solutions, I don't
have it. Might be interesting if the GPS mfgs put that function in
their GPS's. Could be done, I suppose.

ON long flights I don't have anything else to do, so might as well
mess around with trying to make time and saving fuel.


(Andrew Sarangan) wrote in message . com...
Except in high winds aloft or bad turbulence, I have found that flying
low (safety permitting) generally results in the most optimum
solution. Climbing higher for better tailwind doesn't buy more than a
few minutes. Of course, the ratio of climb time to cruise time has a
big effect too. There are too many variable to make a rule of thumb.
What I do is try a few altitudes on DUATs flight planner and pick the
lowest altitude that seems reasonable.



"John Harlow" wrote in message ...
I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?