Followup, was: First time instrument failure while in IMC

Well...it could have been water in the pitot system...and maybe not.
After the shop removed the ASI then blew high pressure air through the
system, everything works just fine. No identifiable debris from the
system though.

Before removing the ASI, blowing low pressure air through the system
would get an indication on the ASI but the rate of movement was slower
than normal (which would indicate something blocking the system).

A day before the shop took a look, I did a high speed taxi (12 kt.
headwind, got up to maybe 5 mph below rotation speed)...but...no
movement on the ASI.

Both heating elements in the pitot tube were verified as properly
working (good to know, I've been logging lots of cloud time lately).

So, still somewhat of a mystery but at least I can continue instrument
lessons and hoping for a decent VFR day to just fly for fun (not likely
in the next few days as the Pacific storms roll in).

Estimated repair cost: .1 AMU. Value of having all instruments while
flying through the clouds: priceless. Lesson learned: Notify ATC upon
failure of a required instrument (wasn't an issue on our flight where it
failed but we should have notified ATC).


While riding as a passenger in our plane today, the airspeed
indicator started reading much lower than normal and finally wound
down to zero. Just to make things more interesting, we were in solid
IMC. Pitot heat was checked before the flight, had been on since
shortly after takeoff and we could observe movement on the ammeter
when turning the pitot heat off/on. Alternate static didn't change
anything significantly and all other instruments were working fine.
GPS was indicating reasonable ground speed given the winds. Outside
air temp was 9 degrees C at the time. Deduction: blockage somewhere
in the pitot system. Probably water as we had a similar situation
over the summer after washing the plane (without the pitot cover
on...duh...new owners). A couple days baking in 100 plus degree heat
solved the problem that time.

We wound up heading back home. No flying for me today :-( However,
it was a great learning experience, even from the back seat as the
three of us did the troubleshooting and figuring out our best course
of action. There's always something new to learn or experience.

Hopefully, more IMC time in a couple of days as we seem to have some
nice storm systems rolling through the left coast.

--
Jack Allison
PP-ASEL-IA Student
Arrow N2104T

"When once you have tasted flight, you will forever walk the Earth
with your eyes turned skyward, for there you have been, and there
you will always long to return"
- Leonardo Da Vinci

(Remove the obvious from address to reply via e-mail)