REFLECTOR: Performance

Geoff Gerhardt geoff.gerhardt at gmail.com
Wed May 8 12:02:16 CDT 2013


Peter,

I have the dual NACA ducts on top, down draft cooling.  Generally speaking
my cooling is ok.  I do have to watch on climb out that I lower to 75%
power as I climb from ~2000-6000' as my CHT"s can creep up to 410F if I
hold full power on climb.  If I hold 75% power on climb, though, they max
at about 400F in climb then settle down to 380F or less in cruise.  Past
about 5-6000', tho, I can go WOT as at that altitude the lower MAP doesn't
allow me to generate enough power to overheat.

I don't think the CS prop will give more speed (if you have a cruise prop
like mine), it will just allow you to still hop off the runway quicker and
have a better rate of climb.

Geoff

On Wed, May 8, 2013 at 11:35 AM, Peter Braswell <peter.braswell at gmail.com>wrote:

> Hi Geoff,
> I'm still building, so I'm afraid I can't contribute much to helping you
> find more speed, but I was wondering what you're doing for engine cooling.
>  Do you have the newer style NACA ducts for engine cooling or do you have
> the older scoop?  I understand that can make a significant difference.
>
> I was also wondering about the prop.  I opting for a V/P MT three blade
> hoping to be able to milk a little more top end.  Is your prop considered a
> climb, cruise or climb / cruise prop?
>
> -Peter
> ------------------------------------------------------------------------
> *"It's a Jungle Up There": www.zuluworks.com*
> ------------------------------------------------------------------------
>
>
> On Wed, May 8, 2013 at 10:38 AM, Geoff Gerhardt <geoff.gerhardt at gmail.com>wrote:
>
>> Folks,
>>
>> I'm getting pretty consistent performance out of my 173RG over the last
>> 8-9 months since initial flight testing.  My question to you guys is, are
>> the performance numbers I'm seeing typical, or should I be seeing better
>> performance?  Normally, on a cross country, I'll fly b/w ~8-12,000', ~60deg
>> LOP which typically has me going 150kias at 8-8.5gph.  Full power, 160kias
>> is about my max speed.
>>
>> I have a fixed-pitch Catto prop (66x74, design target 200mph @ 2800RPM).
>>  When I'm doing 160kts, my prop is spinning at ~2800RPM.  That tells me
>> that I have the power to spin the prop, but may have air frame drag that's
>> keeping me from seeing the 200mph predicted by Catto at 2800RPM.
>>
>> I have a standard 200hp, Lyc IO-360, Lightspeed EI on one side, Mag on
>> the other.  Timing as per spec for both EI and Mag.  About 90hrs on the
>> engine (rebuilt).  Compression/oil consumption is normal.  Very stable
>> performance from the engine.
>>
>> My plane is fully finished and pretty tight.  Main/nose gear doors are
>> not hanging out and are reasonably well tucked in when the gear is raised.
>>  Main wing angles of incidence are spot on, no rudder trimming was
>> necessary to center the ball - she flies nice and straight.
>>
>> The factory predicts I should be able to cruise at 175kias - that's just
>> not possible with my current setup.  Can others with Std Velocities relate
>> the performance you are seeing?  Is this as good as it gets, or does anyone
>> have suggestions for things to check to see if I can eek out a bit more
>> speed?
>>
>> Thanks.
>>
>> Geoff
>>
>>
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