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1. 10:42 AM - long avionics views (ivo welch)
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| Subject: | long avionics views |
--> RV9-List message posted by: ivo welch <ivo.welch@yale.edu>
Hi chaps: because many of you are still building, maybe some more
flying stories and some avionics opinions will be useful.
I put the dynon EFIS into my revised cockpit. (for anyone who plans to
fly IFR, I think having such a backup system is an absolute-must. do
not trust your life to mechanical gyros alone!) I now flew around with
it for a while. definitely recommended. better than the standard
instruments.
Q: to fly IFR/VFR, in an experimental, the instruments need not be
TSO'ed. so, is the AI/ASI/ALT in the Dynon a legal replacement to fly
IFR/VFR? this is important because it determines whether you can
legally fly when your ordinary AI/ASI/ALT are broken [as just happened
to my ALT].
I also determined that the dynon shows airspeeds that are about 10mph
higher than my ordinary ASI (aircraft spruce; highest-priced non-TSO
asi). because I now have GPS GS, altimeter IAS, and dynon IAS, I could
try to determine how good the airspeed indicators are (taking altitude,
temperature, etc., into account to compare TAS to GS). It appears as if
the errors are not constant over the entire range of airspeeds. At low
airspeeds (say, TAS=100mph), it appears as if the standard altimeter
works ok. The best estimate is 2/3 ASI, 1/3 Dynon. At high airspeeds
(say, TAS=160mph), the Dynon is much more accurate. Actually, this
explains most of my earlier flying concerns: landing behavior as if the
airplane is too fast (it was!) and cruise speeds that are too low
(primarily, faulty indication of IAS). At 10,000' altitude and 2350rpm,
I am getting mid 170mph TAS/GS. This is about 10mph slower than it
could be, but given that I am not flying under ideal conditions [when
measured by Vans], is probably reasonably ok.
Some more avionics opinions:
$3k BK KMD-150: best deal for MFD. very easy to use.
$2.5k Dynon EFIS: superb.
$2k Trutrak Altrak: altitude hold system. the rv-9a loses or gains
altitude
very quickly. it is a very safe plane, but not very
stable in
this respect. so, if you want to be able to hold
altitude,
eg, in an IFR environment, this is well worth it.
$2k Navaid autopilot: affordable, replaces ball, built-in GPS steering.
$7k GNS-430+indicator necessary for IFR flight IMHO. GNS-530 seems way
overpriced.
$.3k CO Guardian don't be stupid. put one into your airplane.
$1k Garmin audio: recommended. ok.
$1k garmin solid state transponder: highly recommended. please
avoid the old tube ones.
add in switches, ordinary instruments, collision avoidance, good brakers
+ internals, an automobile CD player, and you will spend $25k w/o buying
the *really* expensive stuff. it is amazing how quickly money for
avionics can add up. still, it is not the plane that is worth it, but
my life that is worth it.
what would I do differently now?
- a good, but more expensive alternative to my two separate autopilots
would be a more expensive trutrak system w/ GPS steering.
- a CNX-80 would be a good but more expensive alternative to the
GNS-430.
- an MX-20 w/ the CNX-80 would be a good idea, too. again, twice the
price of the KMD-150.
together, the first three gadgets would add another $10k to the price of
the avionics.
- there may be better collision warning devices now. I have not seen
them in action, though. I would avoid the riteangle stall warning.
so, in retrospect, I think I pretty much bought the correct avionics.
(in fact, because I may eventually be selling my RV-9A, I am wondering
whether I should recycle most of these avionics in order to reduce the
RV-9A price: I am planning to put almost the same avionics into my next
plane (an RV-10). does anyone have a good idea of what percentage of
avionics one usually recaptures in the resale price?)
regards,
/iaw
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