Most jets I've seen have an array
of pitots. I'm a lowly PP but I'd be willing to bet they're connected to
independent cockpit displays with multiple redundancy. Why should jet jockeys
have all the toys?
I don't think there's any harm in a separate
pitot system but I don't think there would be a great advantage. It would add
cost and weight plus the dedicated AOA pitot would still be subject to
blockage and there could be a signifcant discrepancy between the two systems due
to position error. I bought an Advanced AOA, not yet installed- the AOA is
calibrated as part of the pitot/static system. Trying to switch
between two different pitot sources would probably result in an
inaccurate instrument that could be dangerously misleading. That's my
take- it would be best to ask the manufacturer.
That being said, I'll take Grayhawk's
comment further: if someone had a glass panel I think it makes sense
to connect the backup instruments to an independent heated pitot and static
system. The price doesn't have to be crazy- pitots come up on Ebay fairly
often and I've accumulated a few good ones as spares.
Another consideration is an alternate static
system. I have one installed- just a simple valve but it would save wear
and tear on the VSI (anyone keep a hammer handy?).
If the static port gets blocked with a glass
cockpit display what should be done? Is alternate static usually part of the
install or do you break the backup altimeter? That wouldn't help much in a
pressurized plane.
I'd be careful about using GPS
groundspeed as a proxy for airspeed. Groundspeed is affected by wind
direction and velocity but the GPS doesn't know that. It just shows the
result. -Bill Wade
----- Original Message -----
Sent: Friday, August 27, 2010 4:05
PM
Subject: [LML] Re: Pitot System and
AOA
John,
If you are going to be more comfortable with a backup pitot tube, why not
just plumb it to a second airspeed indicator? Will you have pitot heat
on both?
The AOA system I use relies on 4 inputs - upper and lower wing pressures,
pitot and static. If I wanted an airspeed backup I would install another
heated pitot and a dedicated line to a separate AI in order to keep it
simple. Otherwise, I am just going to rely on known power settings cross
checked with GPS ground speed and how quickly the clouds or trees are going
by.
Scott Krueger
In a message dated 8/26/2010 8:06:05 P.M. Central Daylight Time,
JPKleber@aol.com writes:
Greetings,
I will have an AOA in my Legacy.
That said, I am concerned that if for some reason my pitot tube
gets blocked by something like an insect, bird, or other debris, my airspeed
indicator will probably be giving me an erroneous reading.
Would not this error also be reflected in the
AOA?
Therefore, would it not be a good idea to have the AOA on its
own pitot source? And could one tie both pitot tube together so that
if one was blocked, the other would continue to provide pitot
pressure?
Thank you in advance for your input.
John Kleber