How high?

"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?

First, I think previous posters have said it well when they pointed
out all the variables involved and concluded that "the best altitude"
is different for each flight.

Second, a minor correction: An earlier poster said he gained about 1
kt TAS per 1000'. The rule of thumb is 2% per 1000' so I'd expect more
like 2-4 kt TAS gain per 1000', assuming your cruise speed is between
100 and 200 kts. That can offset a slight increase in head wind.

Third, no one so far has pointed out the added safety that higher
altitude buys in the event of an engine failure. From 7500' and
assuming a 10:1 glide ratio (about right in practice for most small GA
planes, with a small safety margin added on), you can glide 75,000' or
over 12 nm. From 3000' you can glide only 5 nm. In civilized areas,
airports are often close enough that the 7500' cruise would allow an
engine out landing at an airport, while the 3000' cruise would
probably not. Of course, you'd also have to practice side slips and
S-turns in order to dump any excess altitude as you approach the
runway. (Altitude becomes your fuel, but unlike a power plane, you
have to land with "zero fuel.")

I fly a motor glider and, in glider mode, must constantly think in
terms of altitude to make an airport. Even though the engine is there
and it's always started for me when I've needed it so far, the prudent
assumption is that it won't start. That thinking carries over to
engine on time too, but I'll admit that with a 50:1 glide ratio and a
turbo charged engine, I have it a bit easier than you power guys.

Even considering their reduced glide ratios, I think many power pilots
don't adquately consider their planes as potential gliders when they
lose an engine. From the few stories I've heard, it sounds like, no
matter how much the pilot has been taught that the engine doesn't make
the plane fly, a gut reaction often takes over when the engine quits
and tells the pilot the plane is going to fall like a rock. That's
probably why all pilots I know who are rated for both power and
gliders say that all pilots should do at least a few landings in a
glider. It helps get over that gut reaction.

Martin