To all performance seekers.
It would be beneficial to all of us owners whether we are equipped with a,
fixed pitch, constant speed, 912/912S/914 owners trigear or mono to compare
apples to apples as much as we can.
Speed kits, attention to detail, CG, altitude, engine type, MP setting, Prop
type, are all factors affecting our aircraft. Weight is not a huge variable
on average cruise speed but it does affect the low speed end much more.
I decided to do a drag polar and plot my performance over the recommended
power ranges. (See Attached Spreadsheets of my first two days of testing at
1300lbs.)
It is not terribly hard to do if your aircraft is equipped with MP gauge,
fuel flow, and is capable of gliding with the prop stopped or better yet
feathered. Start above your target altitude and pick a range of trimmed
airspeeds on a smooth day. (With the engine off, practice over a landing
area unless you are really confident in your restart.) Climb up and repeat
over and over. Exciting stuff eh?
In my personal data collection I chose to do the following:
Drag polar was with a feathered prop at both 10,000 and 2500. Cruise was
---From 1000 to 10,000 as I really don't like flying higher (I have a great
oxygen bottle, but hate to carry it). Unfortunately, too many years at sea
level shows up when I am trying to do math in public above 10K without
oxygen. My IQ goes from two to one.
I am sure you can see from the drag polar the min point on the curve and
note the power required for Max Endurance or L/D max is only 25 HP. Too bad
the 914 loads up at 3500 RPM and 22 inches at that power setting (See your
Rotax Operators Manual). For max range you guys have already figured out
that you have to slow down to intolerable speeds of 95 Knots at 27 1/2 HP
(point of a line from the origin to a tangent on the power curve). The RPM
and MP again are well below clean plug running in my bird.
You can also see the difference between the AP420 and AP332 on N12AY's
cruise and climb performance. Best speed at max continuous is at about
7500MSL.
The wide chord Sensenich gives better speed at 7500 MSL and is only slightly
better in climb. I'm sure if I continued up to 15K I could get a bit more
speed, but higher power means more fuel burn and it takes longer to get to
15K. (That's a different chart on optimum climb vs. range.)
As one can see, I fly no lower than 4800 and 28 inches which is roughly 120
knots TAS which keeps the plugs clean without running up once in a while to
clear the carbon.
Flaw in my character. I just don't like going below 120 at cruise. ( My
gas milage is lower at around 25-27). I have tried cruising at 4300/28
while flying in formation with a crippled bird. My MPG was awesome at over
30 MPG but again I was only going about 90KIAS at 4500 MSL. The engine
after about an hour starts to miss, and requires me to run up to 5500 for a
few minutes to clear the carbon.
Get your bird tuned up and pick a nice fall day to do some performance data
collection. I use my Go Pro camera to record things for me. Then sit down
with the laptop and pull data down from the video.
Regards,
Bud Yerly
--------------------------------------------------
From: "Christoph Both" <christoph.both@acadiau.ca>
Sent: Monday, September 22, 2014 12:03 PM
Subject: Re: Europa-List: Performance chart Europa CLASSIC C-GPEL
> <christoph.both@acadiau.ca>
>
> Thanks, David!
> This confirms that the TURBO 914 is probably the best matched engine for
> this capable airframe.
> Christoph
>
> On 2014-09-22, 11:44 AM, "David Joyce" <davidjoyce@doctors.org.uk> wrote:
>
>><davidjoyce@doctors.org.uk>
>>
>>Christopher, Although not directly comparable, you may be
>>interested in the following figures for my XS mono G-XSDJ
>>with 914, Woodcomp SR3000/3/W, Smart controller and speed
>>kit at 90% MAUW and 2000 ft unless stated otherwise:
>>Max speed at 100% power (ie not using the extra 15%
>>available for 5 mins only) TAS 156kts (164 at 6500ft)
>>Fuel flow:
>> 100kts 12 l/hr
>> 110 13
>> 120 14
>> 130 19
>> 140 23
>> At 10,000ft 150kts TAS (129kts IAS) 21 l/hr
>>These figures came from a comparison I did between the low
>>twist Sr2000 prop and the high twist SR 3000W prop, which
>>showed the latter gave appreciably better performance with
>>max speed being 4kts higher at various altitudes, fuel
>>flow being on average 0.6 l/hr better, climb rate improved
>>and cooling problems transformed. The increased top speed
>>according to CAFE calculations was the equivalent of
>>having an extra 4 hp!
>>Regards, David Joyce, G-XSDJ
>>
>>
>> Christoph Both <christoph.both@acadiau.ca> wrote:
>>> Dear Europa Community:
>>> I thought you might find the following comments and
>>>attached spreadsheet of interest.
>>> I tested and tabulated fly data for Canadian C-GPEL on
>>>SEPT 17-2014. You might be interested to see where the
>>>most gain is for C-GPEL Classic 912S, Woodcomp 3000 two
>>>blade propellor, Smart Avionic Prop Control. The data
>>>collected, for 4950RPM where possible, is denoted
>>>separately for fuel efficiency and speed with a linear
>>>increase in MAP from minimum required power to keep the
>>>plane at altitude, all the way to WOT, measured at 2500
>>>feet. There are some interesting jumps in the graphic
>>>curves, most noticeable around the (EGT) point, where all
>>>4 cylinders turned out to be exactly the same EGT within
>>>10 degrees Celsius on a GRT graphic analyzer (meaning:
>>>most effective combustion=best torque). So for most
>>>efficiently butting into headwind best suggested would be
>>>27.5MAP (115 IAS) while most efficient tailwind use
>>>would suggest 24.5MAP (95 IAS) or even 23.5 MAP (91 IAS)
>>>with a fuel burn of only 9.4 litres/hour (or 2.5 GAL/hr)
>>>exactly as the book says. Endurance can be chosen at
>>>22.5MAP with a fuel flow of only 8.1 litres/hr (2.16
>>>GAL/hr), magically arriving at 87 IAS, empirically found
>>>to be the most efficient climb speed. Quite a magic
>>>square this little airplane. This is all without any
>>>speed kit or wheel pants.
>>> Chris
>>
>>
>>
>>
>
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