Skycatcher par deux

Talk about airplanes! At last count, there are 39 (and growing) FAA certificated S-LSA (special light sport aircraft). These are factory-built ready to fly airplanes. If you can't afford a factory-built LSA, consider buying an E-LSA kit (experimental LSA - up to 99% complete).

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MrMorden
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Re: Skycatcher par deux

Postby MrMorden » Mon Mar 05, 2018 9:04 am

drseti wrote:
Jim Hardin wrote:Curious, how do conventional instruments compare in weight to the gee whiz glass?


Mechanical round gauges are much heavier


Definitely. I have backup airspeed and altitude steam gauges, and I bet the two of them together weigh the same as my Dynon D-100 which provides ten times the information. Don't get me wrong, I'm glad I have the backups, and there's nothing wrong with real gauges, but mechanical stuff weighs more than electrons. :D
Andy Walker
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2007 Flight Design CTSW E-LSA

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Re: Skycatcher par deux

Postby drseti » Mon Mar 05, 2018 9:22 am

MrMorden wrote: Make sure every drop of fuel is removed, liquids are heavy.


Actually, Basic Empty Weight (by definition) includes UNusable fuel. So, don't drain the tanks! Rather, get them quite low, start up the engine, and run it until it quits. Then change tanks (if you have more than one) and do it again. This way, you will have left the UNusable fuel onboard when you weigh the plane.

OR, if you do have bone-dry tanks, check the documented unusable fuel quantity, and add exactly that much before weighing the plane.

OR, with bone-dry tanks, weigh the plane. Then add the weight and moment of the unusable fuel to your W/B spreadsheet, and recalculate both empty weight and empty CG, to include unusable fuel.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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Re: Skycatcher par deux

Postby MrMorden » Mon Mar 05, 2018 9:30 am

drseti wrote:
MrMorden wrote: Make sure every drop of fuel is removed, liquids are heavy.


Actually, Basic Empty Weight (by definition) includes UNusable fuel. So, don't drain the tanks! Rather, get them quite low, start up the engine, and run it until it quits. Then change tanks (if you have more than one) and do it again. This way, you will have left the UNusable fuel onboard when you weigh the plane.

OR, if you do have bone-dry tanks, check the documented unusable fuel quantity, and add exactly that much before weighing the plane.

OR, with bone-dry tanks, weigh the plane. Then add the weight and moment of the unusable fuel to your W/B spreadsheet, and recalculate both empty weight and empty CG, to include unusable fuel.


If you drain fuel until it stops flowing from the gascolator, isn't the unusable fuel still in the tanks? I think just draining the tanks until they quit flowing is acceptable. That's how I've always done it.
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2007 Flight Design CTSW E-LSA

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Re: Skycatcher par deux

Postby drseti » Mon Mar 05, 2018 9:36 am

MrMorden wrote:If you drain fuel until it stops flowing from the gascolator, isn't the unusable fuel still in the tanks? I think just draining the tanks until they quit flowing is acceptable. That's how I've always done it.


That works, if you have a gascolator installed in line with the entrance port to the fuel selector valve itself. Many LSAs have no gascolator at all, so folks try to empty the tanks through the drain valve at the bottom of each tank. Of course, doing so will empty the unusable fuel along with the usable.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
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Re: Skycatcher par deux

Postby Merlinspop » Mon Mar 05, 2018 9:37 am

MrMorden wrote:
drseti wrote:
MrMorden wrote: Make sure every drop of fuel is removed, liquids are heavy.


Actually, Basic Empty Weight (by definition) includes UNusable fuel. So, don't drain the tanks! Rather, get them quite low, start up the engine, and run it until it quits. Then change tanks (if you have more than one) and do it again. This way, you will have left the UNusable fuel onboard when you weigh the plane.

OR, if you do have bone-dry tanks, check the documented unusable fuel quantity, and add exactly that much before weighing the plane.

OR, with bone-dry tanks, weigh the plane. Then add the weight and moment of the unusable fuel to your W/B spreadsheet, and recalculate both empty weight and empty CG, to include unusable fuel.


If you drain fuel until it stops flowing from the gascolator, isn't the unusable fuel still in the tanks? I think just draining the tanks until they quit flowing is acceptable. That's how I've always done it.

Isn't UNusable fuel determined by "worst case"? Possibly a climb or a climbing turn? In which case, Andy's proposed method may leave less fuel in the tank(s) than what was deemed UNusable by the manufacturer?
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Re: Skycatcher par deux

Postby 3Dreaming » Mon Mar 05, 2018 10:19 am

Warmi wrote:I have a sneaky suspition that my inherited, paper- based empty weight is somewhat off .... what is the most reasonable ( read , cheap :D ) way to weight an LSA?


Our EAA chapter bought a set of aircraft scales a couple years ago. We do rent them to non chapter members, but for local use only.

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Re: Skycatcher par deux

Postby 3Dreaming » Mon Mar 05, 2018 10:23 am

MrMorden wrote: It's all relative. 808lb empty is pretty light for a SportCruiser, I think the one I flew in was around 825lb. Compared with the empty weight of 745lb for my CTSW, it's porky, but compared to the 830-840lb empty weight of the latest CTLSi, your SportCruiser is doing just fine.


I think one recent CTLSi that was for sale had an empty weight of 854lb.

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Re: Skycatcher par deux

Postby MrMorden » Mon Mar 05, 2018 10:46 am

Merlinspop wrote:Isn't UNusable fuel determined by "worst case"? Possibly a climb or a climbing turn? In which case, Andy's proposed method may leave less fuel in the tank(s) than what was deemed UNusable by the manufacturer?


How are you going to simulate "the worst case" on the ground? Assuming you can't, how are you going to drain the last bit of fuel out of the tanks so that you can then add in the factory specified unusable fuel?

Being perfectly accurate is great, but there are considerations that make that nearly impossible in some cases. In this case I think my method is "close enough", will be accepted by FAA representatives, and doesn't compromise safety.

Since we are talking about W&B here, consider my airplane as an example. Each tank has unsusable fuel of 0.5 gallons, according to the factory. Let's say that in flat attitude on the ground, the unusable fuel is really 0.3 gallons. So we're talking about a total difference between the two tanks of 0.4 gallons, or 6x0.4 = 2.4 pounds. Which is right over the center of lift and center of gravity, which are the same in a CT.

What kind of engineering and mathematical shenanigans are we willing to go through over 2.4lb that has zero CG effect that the FAA considers to not be an issue (by virtue of them accepting this method for W&B purposes)?
Andy Walker
Athens, GA
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2007 Flight Design CTSW E-LSA

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Re: Skycatcher par deux

Postby MrMorden » Mon Mar 05, 2018 10:53 am

3Dreaming wrote:
MrMorden wrote: It's all relative. 808lb empty is pretty light for a SportCruiser, I think the one I flew in was around 825lb. Compared with the empty weight of 745lb for my CTSW, it's porky, but compared to the 830-840lb empty weight of the latest CTLSi, your SportCruiser is doing just fine.


I think one recent CTLSi that was for sale had an empty weight of 854lb.


I believe it. The CTLSi IS "porky". Very nice, but fat. Legally, it's essentially a single-seat airplane if you are normal adult...a 200lb human, full fuel (34 gallons) and 62lb of baggage and "airplane stuff". At half fuel you can take a 150lb passenger, but then your teeth start to ache because you are thinking about fuel the entire trip.
Andy Walker
Athens, GA
Sport Pilot ASEL, LSRI
2007 Flight Design CTSW E-LSA

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Re: Skycatcher par deux

Postby drseti » Mon Mar 05, 2018 1:19 pm

MrMorden wrote: I think my method is "close enough", will be accepted by FAA representatives, and doesn't compromise safety.


I concur.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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Re: Skycatcher par deux

Postby TimTaylor » Mon Mar 12, 2018 8:43 pm

I read the specs on the new Vason today. It is an all metal, well equipped airplane with Continental 100 hp engine. The interior is very sparse but the airplane has a useful load about 45 pounds less than the SkyCatcher. It does carry about 4 more gallons of fuel. Price for basic model (which includes autopilot), which is what I would buy, is just over $99,000.
Commercial Pilot Airplane Single & Multiengine Land; Instrument Airplane; Sport Endorsement Airplane Single Engine Sea; Flight Instructor Airplane Single And Multiengine; Ground Instructor Advanced Instrument

Warmi
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Re: Skycatcher par deux

Postby Warmi » Mon Mar 12, 2018 8:48 pm

It really sounds like the kind of plane that would fit your style/mission quite well ( mostly solo, continental engine etc ) - and it is a nice looking plane too . Not as nice looking as Tecnams but only half the price and it does pretty much everything Tecnams can do.
Flying Sting S4 ( N184WA ) out of Illinois

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Re: Skycatcher par deux

Postby TimTaylor » Mon Mar 12, 2018 9:16 pm

Warmi wrote:It really sounds like the kind of plane that would fit your style/mission quite well ( mostly solo, continental engine etc ) - and it is a nice looking plane too . Not as nice looking as Tecnams but only half the price and it does pretty much everything Tecnams can do.

To me, it looks better than the Tecnam. That's because I look first at price and capability for my mission. I want to call them and see when they will start shipping to individual owners vs flight schools. If it's a year or more out, I might think about putting down a deposit if it's refundable.
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Re: Skycatcher par deux

Postby Cub flyer » Sat Mar 17, 2018 5:37 am

For unusable fuel you need to establish max climb angle during a test flight. Then on the ground set the fuel level at minimum day VFR reserves. 1/2hr. Back the airplane over a hill or prop it up to that max angle on the ground. Allow fuel to gravity flow to the pump inlet and into a calibrated container until it stops making a flow rate which is 150% of max takeoff fuel flow. If the electric boost pump will supply the same rate as the engine run the pump until it stops adequate flow with the hose outlet at the same elevation as the engine driven pump inlet.

That’s the short version of how it’s done for Part 23. There are more details.

There are more details but unusable fuel is not where it stops flow. The weight and volume difference on an LSA may be minimal but it’s worth checking this way. It’s usually possible to run in level flight into the usable fuel capacity but if you have to go around on landing it may not feed. A left, both, right selector is useful sometimes so you can run one tank completely dry and keep higher fuel level in another tank for approach to landing. The single tank with higher level may not un port as easily in the extreme range situation.
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Re: Skycatcher par deux

Postby drseti » Sat Mar 17, 2018 12:35 pm

Getting back to actually weighing the plane:

If the manufacturer or designer has specified what the quantity of unusable fuel is, you can drain the tanks completely, then add back exactly the specified amount, and just weigh the plane. But, there's an easier way, assuming you know the arm of the fuel tanks (which you should be able to find on the wt/bal worksheet). Remove everything else from the plane, fill the tanks to the top, level the plane on the scales, read its total weight and compute CG in that configuration. Then, work backwards through the wt/bal sheet, subtracting out the wt and moment of the specified usable fuel. You now have computed the EW and EWCG, without first having to figure out exactly how much unusable fuel to add.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
fly@AvSport.org
AvSport.org
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