REFLECTOR: Speeds

Thu Jun 7 08:11:47 CDT 2012

Interesting Bob.  I too would have expected a larger speed increase with 
altitude. Do you experience a noticeable increase in AOA above 20,000?

I love over squared. Your settings sound good to me.

Have you tried a bit higher RPM, say 2400-2450, same fuel burn to see if 
you get a better increase with altitude.  I knew a guy with a Bonanza 
V35 with a custom TIO550 installation that ran up high and I think he 
turned it a bit faster up high.

My normally aspirated IO520 burns

13.5 GPH at 6,000 175 TAS
12.5 GPH at 10,000 180 TAS
11.5 GPH at 15,000 180 TAS

haven't cruised at a higher altitude enough to get a good consumption 
number yet.

Scott

-------- Original Message --------
Subject: Re: REFLECTOR: Speeds
From: Bob Jackson (Jax Tech) <bobj at jaxtechllc.com>
To: 'Velocity Aircraft Owners and Builders list' <reflector at tvbf.org>
Date: 06/07/2012 06:48 AM

> Here are some cruising true airspeeds we've verified for our turbo XL-RG
> over the years at 2300 RPM, 28" MAP, 13.3 gph, LOP, which for our TNIO 550N
> is a 60% power setting (186 hp). These are for an aircraft flying weight of
> 3000 lb:
>
> 6000' MSL 170 KTAS
> 12,000' MSL 180 KTAS
> 18,000' MSL 190 KTAS
> 24,000' MSL 200 KTAS
>
> What we've worked the most on over the past couple of years is achieving
> these steady state cruising conditions with the CHTs at or below 380
> degrees. It gets increasingly harder with the thinner air at altitude, even
> though the OAT is much lower. One thing that helps a lot (besides good
> cooling airflow and tight plenums) is the 'over square' MAPs.
>
> We used to run 2" over square LOP (25" MAP for the 2300 RPM power setting
> above), but found that 28" or 29" produced much lower still CHTs. It doesn't
> add any more power (that's determined by the 13.3 gph fuel flow), just more
> air for increased cooling -- sort of like the way you add extra fuel ROP for
> cooling on WOT climb-outs. And the engine doesn't complain with balanced
> injectors and dual Lightspeed electronic ignitions. We haven't had any
> detonation issues.
>
> One disappointment is that we were hoping for bigger TAS increases with
> altitude than those above. Using the 2% per 1000' rule of thumb, we were
> expecting better than 230 KTAS at 24,000' (with 170 KTAS at 6000'), but are
> getting only 200 KTAS at the 60% power setting above. Changing to a four
> bladed prop didn't help much, though we do run a lot smoother. Apparently
> it's due to the increased induced drag due to the slightly higher AOA
> required in the thinner air to provide equivalent lift. Still, we're pleased
> with the performance we're getting!
>
> Anyone else have a better explanation?
>
> Bob Jackson
> N2XF - 650 hrs
>
>
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Richard J. Gentil
> Sent: Thursday, June 07, 2012 1:39 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Speeds
>
> Hey Scott,
>
> On the deck I was indicating 165-168 kts KIAS
>
> At 6,500 feet I was indicating 150-151 kts KIAS figure temp around 56F and
> altimeter around 30.03 if memory serves.
>
> As for the altitudes between 1,000 feet and 6,500 feet I do not exactly
> remember but they trued out around 170 kts KTAS.
>
> Richard
>
>
>
> Sent from my iPhone 4 Classic
>
> On Jun 6, 2012, at 10:11 PM, Scott Derrick<scott at tnstaafl.net>  wrote:
>
>> So, you do that in the air at 170 KIAS?
>>
>> -------- Original Message --------
>> Subject: Re: REFLECTOR: Speeds
>> From: Richard J. Gentil<richard at naples-air-center.com>
>> To: Velocity Aircraft Owners and Builders list<reflector at tvbf.org>
>> Date: 06/06/2012 06:10 PM
>>
>>> Scott,
>>>
>>> I own a 145 repair station with an avionics department. I had my avionics
> pump up with Velo with the test equipment while I set the calibrating
> information in both EFIS systems. Altimeter and airspeed are calibrated from
> -1,000 feet to 25,000 feet.
>>>
>>> Richard
>>>
>>> Sent from my iPhone 4 Classic
>>>
>>> On Jun 6, 2012, at 7:48 PM, Scott Derrick<scott at tnstaafl.net>   wrote:
>>>
>>>> Richard,
>>>>
>>>> I think your doing very well at 170 KTAS..
>>>>
>>>> I haven't seen a Std RG any faster when comparing TAS.
>>>>
>>>> I don't have much confidence when I hear somebody reporting faster
> speeds than that with an STD RG. The longwing STD's are 5-10 knots slower
> than the orig STD.
>>>>
>>>> There are two main reasons for incorrect airspeed reporting in
> homebuilts.
>>>>
>>>> 1.) the pitot Static system has not been calibrated. Usually this is a
> result of a bad static reading. The only way I know of to check this is a
> very low(50 ft) pass over the runway at cruise speed. before the pass set
> your altimeter(on the ground) and verify the altitude on your altimeter, add
> 50 ft for comparison. During the low pass write down the altitude.  If it is
> off by more than then 50 ft, you probably should adjust your static port. If
> it reads higher than it should you have too much static pressure, if lower
> you have too little. I adjusted mine with a small piece of aluminum tape in
> front of my port, this reduced the pressure and now I read the correct
> altitude. Because the IAS instrument is a comparator, comparing the pitot
> pressure against the static pressure, if your static port is off your
> airspeed indicator will be too.
>>>>
>>>> 2.) The other reason is the confusion between GPS ground speed and TAS.
> Yes if you are in a no wind situation, very very rare, they are basically
> equal. but more often than not they are not and you will need to subtract a
> tailwind component or add a headwind component.
>>>>
>>>> Scott
>>>>
>>>> -------- Original Message --------
>>>> Subject: Re: REFLECTOR: Speeds
>>>> From: Richard J. Gentil<richard at naples-air-center.com>
>>>> To: Velocity Aircraft Owners and Builders list<reflector at tvbf.org>
>>>> Date: 06/06/2012 04:02 PM
>>>>
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