Oh, thank you master

[Rich]

I've been using a W&B spreadsheet ( don't see a way to attach it here) but I'm sure many of you have a version in Excel.

I've been using mine to check loading for my 100# Lab who travels with me on a dog platform I put over the back seats.

I'd like to get another Lab but can't seem to get the Aft loading to work with 2 100# dogs in back, despite being under gross ..

I see another post here with a 200# woman in back w/ luggage and wonder if the spreadsheet I'm using may be in error. Obviously I need to go thru and do the manual moment arm calc but the real question I have is what the heaviest loading you've been comfortable with and how much fuel was onboard .. let's assume sea level.

thanks,
Gary

There may or may not be anything wrong with your spreadsheet. For one thing, the 200# woman was in the front seat. Her husband and all the luggage was in the back. And my plane is a 2002 40 gallon version. These older Stars have a significantly more forward empty CG (and are lighter) than the later ones and tend toward nose-heaviness. And the 40 gallon versions have a more allowable rearward CG. There's almost no way for me to load mine out of rearward CG.

That said, I did a sample loading of mine, trying to approximate your possible load and it looked OK by a pretty good margin. So maybe there's an error. What are your empty weight and moment numbers?

[CFIDave]

Gary: I don't remember whether your DA40 has ballast in the nose or not, but if you have a lighter 2 or 3-blade composite prop without 20 lbs of nose ballast, a DA40 XLS/XLT can be under max gross weight, yet not be able to put much weight in the back seat or rear luggage areas. Even with the nose ballast, a single front seat pilot might not balance out the weight of 2 big dogs in the back of your DA40.

Earlier steam-gauge Lycoming DA40s like Rich's were more nose-heavy, later G1000 Lycoming DA40s with extended-range tanks like yours tend to be more tail-heavy with limited aft CG range, and DA40 NGs with Austro engines are more nose-heavy (I guarantee you'd be able to fit 2 100-lb dogs in the back of a new DA40 NG ).

[gordsh]

"The plane leaps into the sky as if it had just been cured of the flu or something."

I could not stop laughing at this line. LOL.

[Rich]

The DA40 would be a dream machine if I could get another 200lbs useful. I'm at 800lbs on the button....

On a separate thread I covered the correction made to the empty weight/CG I was using at the start of this thread. With the MTOW/MLG mod noted at the beginning of this thread and careful reweighing I'm at 935 lb. useful load. Last summer I loaded it full of stuff and folks (though not particularly heavy kids) and flew from Spokane to Prineville. Easy Peasy. I foresee no scenario where I'd need a higher useful load. Of course, I have the 40 gallon tanks so the max poundage eaten up by fuel for me is 240 lbs., not 300.

[CFIDave]

On the subject of W&B and useful load, I thought I'd share what I learned from flying a customer's new DA40 NG built in Canada, and how it compares to Lycoming DA40s also built there.

The NG is about 200 lbs heavier due to the greater weight of the Austro turbo-diesel engine, but it has a maximum takeoff weight (MTOW) increase to 2880 lbs (1310 kg). This particular new DA40 NG has a maximum useful load of 856 lbs, which is about 30 lbs more than the 2008 DA40 XLS that the owner traded in on his new NG.

But the DA40 NG, even with its "extended range" fuel tanks, holds only 39 gallons, instead of the 50 gallons of a Lycoming DA40 XLS. The NG doesn't need to carry as much fuel because of its lower burn rate in cruise of only 6.5 gal/hour. The weight of NG full fuel is 39 gal x 6.7 lbs/gal of JetA = 262 lbs. vs. the XLS full fuel weight of 50 gal x 6.0 lbs/gal of avgas = 300 lbs: a fuel weight difference of about 38 lbs favoring the NG.

So a DA40 NG with full fuel can carry 30 + 38 = 68 lbs more payload than a typical DA40 XLS. And because the NG is more nose instead of tail-heavy, it has a more usable back seat and rear baggage compartment than the XLS. (We're taking delivery of another new DA40 NG this week with factory air conditioning, so it'll be interesting to compare its W&B and how it can be loaded.)

[gtmize]

I think I’m ok with two 100# labs in the back seats.

With me, a 200# pilot, 50# right seat, 50 gals, it works out to 2550# at 2.55 m, the upper limit.

Center Gravity Limits (Pg 6-13) 2.4 to 2.55 m.

Empty weight & moment on my N175DA = 1807# @ 2.5 M.

I thought it was humorous the POH example calculation of W&B pg 6-12 uses 1620# for Empty Mass, 180# less than mine … wow .. all those avionics? cost me a lot of useful load. Dave I want those 180# back!

But here’s a what I don’t get. The center of the wings ( pg 6-9) is at 2.63 m. If you ignore any lift from the fuselage, then the center of lift would be here, 2.63m. So why are the CG limits from 2.4 to 2.55 m? Any COG in these limits would be seem to be nose heavy.

Wherever your starting point, if you add 100# in the rear seats ( 3.25 m), with the elevator at ~ 7.3 m ( pg 6-9), would require an incremental 50# elevator down lift. I assume you’re good as long as you have sufficient elevator authority which could disappear on short final. Just depends on where you started in the envelop.

I apologize for thinking out loud, and welcome any thoughts from the experts here.

[Rich]

Empty weight & moment on my N175DA = 1807# @ 2.5 M.

I thought it was humorous the POH example calculation of W&B pg 6-12 uses 1620# for Empty Mass, 180# less than mine … wow .. all those avionics? cost me a lot of useful load. Dave I want those 180# back!

But here’s a what I don’t get. The center of the wings ( pg 6-9) is at 2.63 m. If you ignore any lift from the fuselage, then the center of lift would be here, 2.63m. So why are the CG limits from 2.4 to 2.55 m? Any COG in these limits would be seem to be nose heavy.

Wherever your starting point, if you add 100# in the rear seats ( 3.25 m), with the elevator at ~ 7.3 m ( pg 6-9), would require an incremental 50# elevator down lift. I assume you’re good as long as you have sufficient elevator authority which could disappear on short final. Just depends on where you started in the envelop.

I apologize for thinking out loud, and welcome any thoughts from the experts here.

There's a lot here. The pre-G1000 planes generally went out the door around 1680-1700 lbs. empty. Mine was 1701, where the A/P (with all its components) was, IIRC, about 25 of those lbs. Various mods have since brought it up to 1711. I don't know if Diamond actually ever produced a 1620# plane.

The CG in a plane with rear-located horizontal stabilizer/elevator has to have its CG forward of the center of lift for stability. And the COL usually migrates fore and aft with different angles of attack, flaps up and down, etc. A given design has to cover all phases of flight. In particular, as your CG ever gets aft of the COL the plane may become totally unflyable.

[ultraturtle]

...But here’s a what I don’t get. The center of the wings ( pg 6-9) is at 2.63 m. If you ignore any lift from the fuselage, then the center of lift would be here, 2.63m. So why are the CG limits from 2.4 to 2.55 m?

Center of lift is approximately 1/4 chord, not 1/2. Also (for stability reasons) center of gravity must be forward of center of lift.

[gtmize]

Well, not to micrometer the brick ..

again from 6-9 appears the 1/4 would be @ 2.45 m
& COG limits 2.4 to 2.55 pg 6-13

so a portion of the COG range would appear to extend AFT of COL?

also interesting when you think about it
the range 2.4 to 2.55 is only about 6" .. not a lot of room to play with