New W&B

[pilot716]

Last year when we bough the M20J it was re-weighed and on the new W&B sheet shows a FWD CG of 45.0 & and an AFT CG of 50.0. The original CG limit envelope graph had FWD 41 & aft 50.10. So my question which may seem obvious is, can the envelope really be shortened that much? they did not provide a new envelope graph but I am not sure if I just "shorten" the old one all the other parameters will be the same. Basically this is for a W&B app that forms the envelope graph with the parameters you put in. Thx

[John Pleisse]

45.1" is my total aircraft CG (not forward). I have a loaded down 79-J.

[jetdriven]

I think only the manufacturer can change the weight and balance limits, unless a mechanic gets a field approval to do so. How much useful load did you lose? Our plane isnt getting near a scale.

[danb35]

No, weighing the aircraft will not change the envelope at all. It's possible, I guess, that you're mis-reading the new W&B sheet; if not, it's in error. The envelope is part of the aircraft certification, and the only way to change it is by STC or field-approved major alteration.

[flyboy0681]

I'd be curious to know what the difference between the old and new weight is.

[pilot716]

I tried to post the forms but it comes up error. The Max weight of course is the same. But on the same line next , it says CG range FWD 45.0 AFT 50.1. is that an adjustment to the envelope? If someone can PM me their email I can send it like that, take a look and see what you think. thx

[danb35]

I looked at what you sent me, and it's incorrect, for a couple of reasons. Your correct CG range is set out on page 29 of the TCDS, which is at http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/2fb25685d0303ab1852567ed004f59b8/$FILE/2A3.pdf.

Looking at that, and at the envelope in your POH, you can see that you don't have a single allowable CG range--there are a number of ranges depending on the weight. So, the first reason the form they gave you is wrong is that it only has a single entry for CG range. Mooney isn't unique in this; plenty of other aircraft have CG envelopes that aren't perfect rectangles.

The second reason that form is wrong is that they give the CG range for a max gross weight that your plane doesn't even qualify for. Newer M20Js can get a MGW of 2900 lb, and at that weight, the CG range is 45.0 - 50.1". At 2740 lb, which is your MGW, the range is 43.8 - 50.1".

The fact that they indicated this on your W&B worksheet doesn't mean that they've changed your CG envelope; it just means that the numbers they included for informational purposes are wrong. Only the FAA can approve a change to the CG envelope, by either amending the TCDS, issuing an STC, or giving a field approval on a 337 for the change. Your CG envelope is unchanged. If you talk with the shop, I'd hope they'd do up a new sheet with correct CG range information on it, but they'll never be completely correct with that form that they're using.

[pilot716]

Dan,

Thank you for the info. I called the shop this morning and still have not heard back, regardless of that. I am going to just go with the original CG envelope, My max weight at 2740 has not changed, and just continue to use the new empty weight of 1950 for all calculations. I appreciate all the responses and help. I will post any updated info once I speak to the shop.

Mark

[jetdriven]

Dan,

Thank you for the info. I called the shop this morning and still have not heard back, regardless of that. I am going to just go with the original CG envelope, My max weight at 2740 has not changed, and just continue to use the new empty weight of 1950 for all calculations. I appreciate all the responses and help. I will post any updated info once I speak to the shop.

Mark

Mark, what was the previous empty weight and reason for weighing?

[pilot716]

The weight was 1820 and it was done in 2005 for previous owner and then done for us 3/11 prior to purchase.

[pilot716]

Yep that is correct, We have not added anything, so all the avionics were already there. a couple of items can be removed but they will not make much of a difference. a few pounds here or there.

[jetdriven]

Is there a way to shred that new weight and balance and forget the whole thing happened? It was legal before, right?

[pilot716]

Good questions...I will bring it up at our next oil change when we are there...I was quite shocked when I saw it last year, but figured that was that and what can you do..Not sure where all the extra weight is coming from...speed brakes, avionics...etc..?

[jetdriven]

it may come a shocker the airplane was never weighed at the factory.

[N601RX]

IF the new weight and balance was accidently lost, ate by the dog ect the easiest way to get a new one would be to take an old weight and balance to a mechanic of your choice (perhaps not the one who wieghed the plane) and ask him to generate a new one by just adding the weight and arms of any new equipment that was added since the weight and balance that you provided him.

[Smiles201]

Is it possible that the genius who created your new w&b sheet mis-weighed your ship? Hard to believe empty weight gained so much in seven years.

[danb35]

It's probably a little late to ask why you had the plane weighed--it's done now. Looking through the W&B records for '48Q, whenever a new one was done, the old one was marked "Superseded" with the date the new one was done; if yours is this way too, you probably can't really go back to the old W&B record.

Like others here, I'm pretty suspicious of an unexplained weight gain of 130 lb. Before deciding that the shop screwed it up, though, go through your old W&B records carefully for errors--I found several in mine, even going back to the factory W&B. Check the weights, and check the math. You may find an error in there that would help explain the discrepancy. Even so, though, your useful load sounds awfully low.

[Bennett]

My 1983 J has an empty weight of 1932 pounds after the last weight and balance. This is after the new glass panel and other avionics changes resulted in a net saving of a bit over 30 pounds, and the lightweight interior (aircraft honeycomb / carbon fiber panels and window frames) saved another 20 pounds or so. The complex paint adds some weight; new antennas are offset by removal of old unnecessary antennas, but I suspect the LoPresti cowl and Powerflow exhaust system have added a good deal of weight. At this point I am ready to roll the dice and have the airplane reweighed. It is not so much a problem of takeoff weight, as I generally fly alone, but adding a good sized passenger, with full fuel, could get me up to Gross Weight. Frustrating in that the slightly later Js have the weight increase with the same engine and wing, etc. I understand there is a slight change in part of the "roll cage", and a few landing gear parts, but in flight, these should not matter. I am not advocating flying over gross, but I think this is more a regulatory issue than an aerodynamic issue. Too bad there is no STC to "push the paper".

[jetdriven]

Weighing the plane shouldn't have to be a "roll of the dice".

Write your previous empty weight on your left forearm with a Sharpie marker.

Push it on the scale, if the weight it shows is less than your left arm, write it up and pay your A&P. If it weighs more, push it off, give your A&P a 12-pack, and go hunting or something.

as an emergency measure you can always let 40 pounds of air out of each tire, and drain a gallon of oil to get it under the old weight.

[BigTex]

Find your local EAA Chapter and borrow their scales and weigh the plane yourself.

[Hank]

Wow! Bummer . . .

Even my C has a useful load of 970 lb, or 656 with full fuel [5½ hours theoretical endurance].

Seems like a friendly discussion with the mechanic is in order, maybe with a cool, refreshing adult beverage or two. Get the scoop without upsetting him.

I'm especially curious how he can calculate a new CG envelope rather than use the approved one in the TC and POH?

[danb35]

I'm especially curious how he can calculate a new CG envelope rather than use the approved one in the TC and POH?

I don't think he calculated anything, or intended to change anything. The form he used has one line for forward and aft CG limits, and he entered the wrong numbers (numbers at MGW for a 2900-lb MGW J). The form itself is defective, though, as the limits depend on the weight, so you can't reasonably enter them all on one line. I know this isn't unique to the Mooney; many (perhaps most) other planes have a W&B envelope with steps and angles.

I also don't understand why anyone would bother indicating W&B limits on the sheet--they don't change, so it's extra work and a chance of error for no payoff.

[pilot716]

We are looking into the gain of 130lbs....It does say it was weighed with 15 gal unusable fuel which is 90 lbs and unusable should only be 6gal(3 per side).. regardless, our A&P believes it could have been weighed incorrectly before. He says it does not matter what is on the equipment list because its what the scale says...Maybe next year at the annual we will weigh it again and be present.. The load at this point has worked well for us. we have been at Gross many times and she performs quite well.

[danb35]

No, it says it was weighed with 15 pounds of unusable fuel. He's right that the weight is the weight, and it really doesn't matter what the prior paperwork says--at the same time, that much of a discrepancy should give rise to some concern, and maybe to double- and triple-check the process (make sure it's actually 15 lb, rather than 15 gal., of fuel on board, make sure the plane is otherwise empty, maybe rotate the scales around, etc.).

There's a place that advertises in Trade-a-Plane for aircraft scales with a 2000-lb capacity for ~$400. It's kind of tempting. If you built two platforms the same height as the scale deck, you could get away with weighing a plane with only one scale (though it'd obviously be a lot more hassle than having 3). Or, as someone else here suggested, you could see about borrowing scales from your local EAA chapter.

Edit: The new W&B is also showing over a 5-inch shift in CG. That's a lot. Something is pretty seriously wrong, either with the previous records or with the weighing procedure this time.

[pilot716]

Dave at air mods N87 is reviewing all paperwork and will get back to me...keep ya posted..