I'm sorry but I can't understand your observation:

First.
What you exactly mean by "test the landing gear" ?! What you want to
test ?
The green lights, the actuator, the switch, or what ?
But testing the X-FEED selector is very specific on the PA34.

Second.
I've never seen something like "Don't *test* the landing gear during
taxying."
in any P.O.H. I've read.
But I did see "Check the operation of the fuel management controls by
moving each fuel
selector to CROSSFED for a short time, while the other selector is in
the ON position."
(PA-34-200T P.O.H. Section 4 Normal Procedures 4.23-Taxiing)

Also the "short time" terms are questionable. Do you remember how long
it took to stop the
engine when your FI/CRI simulated an engine failure cutting your fuel
? And the engine was
(hopefully) at cruise power. How long would it take to use all the
fuel in the whole main
pipeline from the same side and let the X-tank fuel feed the engine ?
Making this test for 3-4-5 seconds is meaningless.


Third.
Should a student ask such a question every FI will know the answer:
"Because the safety valve may not work and your landing gear may
retract
while on the ground."
But I couldn't find any answer to my question yet.

Fourth.
The answer every FI should know (to your student's specific question)
is usually
reported in the P.O.H.s (At least in that of the PA23 Atzec).
But I couldn't find anything similar for the fuel selectors yet.
Maybe someone who reads the P.O.H. more carefully than me can
answer...


Silvio

"kage" wrote in message ...

Imagine you are a FI and your student asks you why you should not test
both X-FEED at the same time durign taxying. What are you gonna answer
him ? "Because it is written in the POH." ?! If your student is a good
one He would not be satisfied by this answer since it is an answer it
could find himself.

Thank you anyway...
Silvio

Imagine you are a FI and your student asks you why you should not test
THE LANDING GEAR time durign taxying. What are you gonna answer
him ? "Because it is written in the POH." ?! If your student is a good
one He would not be satisfied by this answer since it is an answer it
could find himself.

Best,
Karl