Well water does not freeze until 0 degrees C at any pressure we pilots
will see. It is true that there is a problem getting an accurate
static temperature at speed and it is also true that you can have
pockets of lower pressure creating lower temperatures around the wing
etc, but I would say that you certainly don't have to worry about
freezing Pitot until 5 degrees C or if you want to be conservative 10
degrees C. It is not like carb ice where you can get freezing temps in
the carb at outside static temps of, well up to 25 degrees C or so. So
I agree, the guy, if he really did write that, is not really on the
ball here, you don't need pitot heat on a hot summer day, no way.

"Paul Mennen" wrote in message y.com...
Just saw in this month's AOPA (Fall flights):

"Most pilots slumming around the pattern on a hot summer day
will probably not flip the pitot heat on, but certainly anytime
you're flying in or near moisture - at any air temperature - It's
safest to use pitot heat." - Editor in Chief, Thomas B. Haines.

Well that would cover at least half the time. Probably more if
one forgets to turn it off when the clouds finally slip out
of sight. Does this seem preposterous to anybody else?

Maybe its because my instructor covered up the airspeed indicator
of the J3 cub for an entire flight during my private training
just to make sure I wasn't becoming too dependent on it. Frankly
it didn't seem too hard to fly without it. Since the cub had no
stall warning system, I did use up more of the dirt patch next
to the runway than usual. (My instructor never actually let me
use the runway. He said that was too easy.) In the past 20 years
of flying my C185, I've flown without the airspeed indicator
several times. Twice it failed to work because of stuff in the
pitot tube. Once I just couldn't see it because there was no moon
and I had a total electrical system failure. (Actually I did have
a flashlight in my pocket, but I didn't see a great motivation
for getting it out. I just landed in the dark.) Twice I saw the
airspeed indicator rapidly head to zero because of icing conditions.
(My icing early warning system With constant power, pitch, and
altitude indications from the other instruments it never crossed
my mind to make any control inputs in response. Flipping the
pitot heater on restored the airspeed indicator within seconds.
(Well airspeed is at least a nice convenience.)

So Mr. Haines' suggestion seems somewhat radical to me. (Ok, I guess
I would use it in the cold soup when I'm already dealing with a loss
of vacuum system emergency.) Just think of all that power wasted.
And is really safer? Perhaps having it on so often would mean that it
would more likely be burnt out one of those few times it would be really
nice to have. And maybe it would snuff out that last 10 minutes of
battery capacity that you needed to complete your approach, because it
took you awhile to recognize that the alternator went belly up.

But he certainly has more experience than my meager 3000 hours,
so what do I know?

Reminds me of the instructions in the POH of my Decathlon that says I
should leave the electrical fuel pump on during takeoff because gravity
feed alone is not sufficient to produce takeoff power in the event the
engine driven fuel pump fails. Gosh, what are we - like the
monkeys on the early space missions. Can't we just turn on the
switch when we need it? (I've already replaced that very expensive
electrical pump twice because me or one of my partners forgot to turn
it off after climbout. It is not robust enough to run it continuously.
I've since given up on following the POH exactly.)

~Paul Mennen