REFLECTOR: Best Speed for MPG

Wed Aug 14 10:55:12 CDT 2013

I can look it up using a standard day.
An online E6B is showing that for a standard day you are indicating 132 
knots at 18K feet, which is going to affect parasitic and lift drag.  
That's not too far off of where the optimal airframe speed is.  Maybe 20 
knots or so.  That's going to be pretty efficient, and hard to beat.

Using your data

alt 	gph 	kts 	nm/g
18000 	10.5 	180 	17.14286
12500 	12 	175 	14.58333
4 	13.5 	175 	12.96296

17 nautical miles per gallon, almost 20 miles per gallon.  Better than 
my car.

On 8/14/2013 10:37 AM, Scott Derrick wrote:
> Brian,
>
> My IAS gauge has a TAS scale, you dial in OAT and altitude and it 
> displays both IAS and TAS. Well, it always display IAS! ;-)  I rarely 
> note the IAS as I'm more interested in my true air speed. Normally 
> comparing my TAS to my GPS ground speed to figure out what the 
> relative winds are.
>
> Next time I fly I can note those.
>
> I can say that for the 4,000 ft speed the IAS and TAS are very close.
>
> Scott
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: Best Speed for MPG
> From: Brian Michalk <michalk at awpi.com>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Date: 08/14/2013 09:18 AM
>
>> Do you have indicated airspeed at those settings?
>>
>> On 8/14/2013 9:00 AM, Scott Derrick wrote:
>>> My best is up high. 18,000 ft, 10.5 GPH 180KTAS.
>>>
>>> At 12,500 ft a more common place for me to cruise, 12 GPH at 175KTAS.
>>>
>>> At 4,000 ft I'm up to 13.5 GPH at 175KTAS
>>>
>>> Scott
>>>
>>>
>>> -------- Original Message --------
>>> Subject: Re: REFLECTOR: Best Speed for MPG
>>> From: Ron N VelocityXLFG <velocityxl at fastmail.fm>
>>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>> Date: 08/14/2013 07:52 AM
>>>
>>>> I have read  that some where also and the argument makes sense that 
>>>> the
>>>> engine is nothing more than a air
>>>> pump. So you do not want to restrict it. Though it seems there should
>>>> also be a sweet spot where the
>>>> aerodynamic is more important that the throttle position.
>>>>
>>>> On 8/14/2013 7:59 AM, Brian Michalk wrote:
>>>>> The engine runs most efficiently at wide open throttle and low RPM.
>>>>>
>>>>> If you can regulate power with altitude, fly high at WOT.
>>>>>
>>>>> On 08/14/2013 07:51 AM, Ron N VelocityXLFG wrote:
>>>>>> I was wondering what the best speed per gallon of gas  has been in
>>>>>> the velocity.
>>>>>> I have been doing some  work on this lately . Now my plane having a
>>>>>> alternative
>>>>>> motor and a fixed pitch prop will likely not be the same as other
>>>>>> installations but
>>>>>> with that said I still would like to know what Speed other velocity
>>>>>> pilots are
>>>>>> finding for the best fuel mileage  has been.  I feel most 
>>>>>> comfortable
>>>>>> at 145 knots
>>>>>> seems to be the sweet spot for me so far but that is also my comfort
>>>>>> zone for the engine
>>>>>> rpm on my fixed pitch propeller. Now this is only about Half 
>>>>>> throttle
>>>>>> for me wide
>>>>>> open I get 175 knots Or should I say 201 MPH  but I am sure my
>>>>>> mileage will go way down at the speed.
>>>>>>
>>>>>>
>>>>>> So far for me with only a few cross country's under my belt
>>>>>> Velocity XLFG LT1
>>>>>> Prop RPM 2500 Prop tip speed 535 mph
>>>>>> Prop Dia 72"
>>>>>> At 4500 alt
>>>>>> 2600 gross Weight
>>>>>> Speed of 143 knots
>>>>>> 280 mile round  trip
>>>>>>
>>>>>> I got 12 gallons an hour
>>>>>> fuel burn
>>>>>>
>>>>>> Ron
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>>
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>

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