Agreed with pitot heat comments.

For those jets at high altitude, the difference between stall speed=20
(slow where it falls out of the sky) and do not exceed, probably near=20
full power at the high altitudes is small, and without the proper=20
airspeed given the pilot and plane's systems, it would be relatively=20
easy to stall the plane, which goes into a "deep stall", where the=20
airflow across the tail surfaces is turbulent, and there is insufficient=20
to generate lift (in the negative direction), to bring the tail up and=20
nose down to a diving attitude and pick up air speed to regain control.=20
The forward airspeed quickly diminishes and the plane mushes to the=20
ground. :(
On 3/14/14 10:54 AM, John Ferrell wrote:
> I used to fly a lot of single engine, real instruments flights. The
> preflight check for pitot heat was simply to observe the ammeter while
> switching it on/off.
> An instrument pilot is expected to have a good idea about what the
> airspeed is for a given power setting at a given altitude in level
> flight. The Pitot source affects only the airspeed indicator.
> While needle, ball and airspeed are considered adequate to fly on
> instruments, the Altimeter is the secondary (backup) airspeed indicator.
>
> On 3/14/2014 7:00 AM, BOB wrote:
>> The heaters in pitot tubes fail.  We used to check them on every pre and
>> post flight inspection.  But then we could reach them from the ground
>> without stands or ladders.

--=20
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