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hgmckay
Joined: 23 May 2006
Posts: 397
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 Posted: Thu Dec 07, 2006 12:47 pm Post subject: Empty weight and C.G. Location |
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Gentlemen:
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I have just weighed my kit built Allegro 2000 (empty weight*) to compare with the published empty weight in the Fantasy Air Flight and Operating Manual.
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* empty weight = weight of plane with standard instruments, engine, coolant, oil, ELT, & Battery (no fuel and no BRS).
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My empty weight* is 320 Kg, or 704 lbs. (Nose wheel = 154 lbs., Right Main wheel = 270 lbs., Left Main wheel = 280 lbs.)
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The Flight and Operating Manual states that the empty weight should be 275 Kg or 605 lbs. I am 99 lbs (16%) heavier than what is published for the empty weight! The published MTOW is 520 Kg, or 1144 lbs. This leaves me only 440 lbs for a BRS, Fuel and 2 occupants. Those numbers are as follows:
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Main fuel tank fuel 14.5 gal. = 88.97 lbs.
BRS = 35.00 lbs.
Wing Tanks Fuel 10.4 gal. = 64.00 lbs.
My Weight = 150.00 lbs
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Total = 337.97 lbs.
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440 lbs. minus 337.97 lbs is 102.03 lbs max weight for the passenger in order not to exceed the MTOW of 1144 lbs. With these numbers, in reality I can’t take a passenger unless he is a child or a very light weight adult.
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What is the basis of the 275 Kg (605 lbs.) stated in the F and O Manual? I don’t understand why I am 99 lbs over the published empty weight! I have nothing more in this plane at empty weight* other than what I have stated above with the *. What are the empty weights running for the ready to fly Allegros with similar items?
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With a total empty weight of 704 lbs. the c.g. is 12.18 inches behind the leading edge. The maximum allowable distance is 390 mm or 15.35” behind the leading edge. 12.18” is 81% of the limit. The F & O Manual states that the c.g. of the empty aircraft is almost exactly the same for the aircraft with one or two pilots and with an empty or full fuel tank. According to this, the empty c.g. and the MTOW c.g. stays the same (i.e I do not have to weigh the plane with fuel, and passengers to calculate a new c.g. . Is this correct?
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I have sent this information to the US Distributor, Fantasy Air USA, but I would like to get some independent feedback concerning the weight issue (605 lbs. Vs. 704 lbs.). Do any of you know your comparable empty weights, and would you share them with me? Any and all help will be deeply appreciated.
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Hugh McKay
Allegro 2000
Rotax 912UL
N661WW
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arno7452(at)bellsouth.net
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| Posted: Thu Dec 07, 2006 9:15 pm Post subject: Empty weight and C.G. Location |
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I have a Zenith CH701 kit on order. For the past year of so, I observe that most builders are significantly over the published empty weight. I can understand a small overage but nearly 100 lbs over with what appears to be standard installs is worrisome.
Ken Arnold
CH701 on order
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tcmoses(at)earthlink.net
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| Posted: Fri Dec 08, 2006 3:54 am Post subject: Empty weight and C.G. Location |
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Hugh,
I have an Allegro and a GT-500 that I just weighed for conversion to E-LSA. I can not help but wonder is your scales are accurate or if they jamed due to side movement of the main gear. As Ken Arnold said this is very worrisome. I used 3 - 400 pound digital scales to weigh the GT-500 and had no problems with repeatability of the scales each time I jacked the plane off of them and reapplied the weight.
Tim Moses
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Fri Dec 08, 2006 5:49 am Post subject: Empty weight and C.G. Location |
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Hugh,
I am guessing the "book" empty weight of 605 lb. is the lightest one
ever built in the Czech Republic which probably had nothing but the
legal minimum in the way of instruments, i.e., airspeed, tachometer,
oil pressure gauge, fuel gauge. You can be sure the "book" empty weight
airplane had not wheel pants or any other options installed for the
official weigh-in. I would not be surprised if the fuel tank (main only
- no wing tanks) did not even have the 1/2 gallon of unusable fuel (3
lb.). Also, the early models had thinner main gear legs and had fabric
on the upper and lower wings between the main and trailing edge spars.
If you calculate all these differences it would not surprise me if the
lightest possible empty weight at that time was what their out-of-date
documents state.
Speaking of out-of-date documents, the MTOW figure in your manual is
the way it was certificated in Europe because of their micro-light (or
whatever they call that category) legal limitations. The MTOW in the
LSA category here is 1,232 lb. which gives you another 88 lb. to play
with but don't forget to add in the 3 lb. for the 1/2 gal. of unusable
fuel into your empty weight, if you weighed it before adding fuel. I
never bothered trying to do the W&B with the formulas in the manual. I
do not doubt that they are mathematically equivalent to the way we do
it here but I just used the US method. Keep in mind that the 1144 lb.
MTOW was used to establish the 4G+ and 2G- load limits. The actual load
limits for the 1232 lb. MTOW would be factored down a bit. I posted
something about this on the Allegro List many months ago. I suspect the
1232 lb. limit for the LSA category is to keep the max stall speed Vs1
at 45 knots or less as required by the LSA regs.
Our Allegro #03-202 has a current empty weight of 649 lb. with the
empty CG at 11.13" aft of wing root leading edge. This is based on the
documentation that came with the aircraft when we bought it as a demo
unit from the Nebraska dealer plus the few small additions we made to
it since the purchase. We've never done an actual accurate weighing of
the airplane so this could be off somewhat. It would not surprise me
that it is off several pounds. I suspect there was some equipment added
between the time it was imported and the time we bought it and the new
items not added into the official W&B documents. I don't know this for
certain. Our Allegro is the only one in the US with the fabric wing
panels and it had the older thinner gear legs too until we replaced
them with the newer heavier ones. We did not add anything to the empty
weight for the legs because the factory didn't tell us they were
heavier but I can tell you from measuring them that they are thicker
and hopefully stronger. No problems so far with the new legs. Our
airplane has only the main fuel tank but it also has the electric
artificial horizon, Icom A-200 radio, intercom, King transponder (we
install after purchase) electric engine pre-heater (~4 oz) an oil
thermostat (~2 lb.), wing tip nav and strobes, and landing lights.
That said, one of my partners weighs 280 lb. and our check-out
instructor weighs 210 lb, so when they flew together with full main
fuel, they were close but not over the 1232 lb. MTOW with no handling
issues at all according to my partner's reports. I've personally flown
it at nearly 1200 lb. and it flies great at that weight though the ROC
is not as good.
I hope this helps a bit.
Thom in Buffalo
do not archive
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
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hgmckay
Joined: 23 May 2006
Posts: 397
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| Posted: Fri Dec 08, 2006 7:38 am Post subject: Empty weight and C.G. Location |
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Thom:
Thanks for your excellent explanation. I am going to check my scales and
their calibration again to make sure my weights are correct. I thought the
MTOW for LSA in the USA was 1320 lbs. not 1232 lbs. Am I wrong? If it is
1320 lbs., the real question is; "is the Allegro 2000 designed to safely fly
with a MTOW of 1320 lbs, or only 1146 lbs. (520 Kg)?
Hugh
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dave(at)dreamwings.co.za
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| Posted: Sat Dec 09, 2006 8:40 am Post subject: Empty weight and C.G. Location |
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Hugh
My Allegro (factory-built) weighs 308kg or 672 lbs. It has metal skinned
wings, strobes and nav lights, wheel spats and a GRS ballistic chute. The
chute weighs 13kg, so without it the empty weight comes out at 295kg or 650
lbs. I think your scales must be out. Considering the parts for the kit
are almost completely factory built, I can't see where you could possibly
pick up so much weight during the build process. We have now added wing
tanks but have not re-weighed it since then.
Dave
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ray
Joined: 26 Apr 2006
Posts: 6
Location: australia
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| Posted: Wed Dec 20, 2006 1:10 am Post subject: Re: Empty weight and C.G. Location |
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Hugh
You say the weight of your plane as being 320kg empty. This may be right.
I`ve taken all the parts off my plane, radio,spates, extra switchs and guages, gps, antena, wing tanks, fuel taps and hosing, strobe light, wing lights, landing light, taken off the differance in weight of a 582, two blade prop instead of three, as the brochure did state that the Allegro will fly with a 582. It would`nt take much to get over 300kg plus if the weights at the factory were calculated with a two stroke and very basics flight equipment.
Ray
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