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Weight and balance question

G

Gnvflyer

Active Member
Getting ready to do my weight and balance tomorrow. I notice on page 14-10 of the construction manual it says:

"Aircraft weighed in level flight attitude, (includes 8 qts. of oil, no fuel.)"

I plan to run my 0-320 D3G with 6 qts. and fill at 5. Why do W&B with 8 qts?

If the engine was burning so much oil that I had to fill to 8 to ensure a safe flight, I wouldn't fly.

Thanks
 
Fill with 6 and take 2 more and sit on top of cowling above oil sump area if you want to be exact but as Walt says, the difference is negligible.
 
So the proper way to do the weigh and balance is wet or normal operating conditions. If normal for you is 6 qts then 6 it should be. To be by the book you would want your POH to state normal is 6 qts. If not the engine manufacturer states 8 and that would be normal.
 
Gnvflyer said:
Getting ready to do my weight and balance tomorrow. I notice on page 14-10 of the construction manual it says:

"Aircraft weighed in level flight attitude, (includes 8 qts. of oil, no fuel.)"

I plan to run my 0-320 D3G with 6 qts. and fill at 5. Why do W&B with 8 qts?

If the engine was burning so much oil that I had to fill to 8 to ensure a safe flight, I wouldn't fly.

Thanks
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Weigh it the way you are going to fly it - but change your POH to reflect that in case someone else flies it, or you sell the plane. 8 quarts is the engine manufacturers recommendation, but in reality anything over 6 gets spit out the breather in short order. I do the same as you, fly with 6 and add at 5.
 
Do it with 6. Then set the 2 extra quarts on top of the cowl and do again with 8. Note which one you use for W&B in the POH.

Just for poops and grins, let us know the difference.
 
If you are flying with 6 quarts in the sump then you are really 7 quarts of oil including what is in the lines and in the filter. So if you have not run the engine yet so lines and filter are empty then you should weigh with 7 quarts in the sump.
 
plehrke said:
If you are flying with 6 quarts in the sump then you are really 7 quarts of oil including what is in the lines and in the filter. So if you have not run the engine yet so lines and filter are empty then you should weigh with 7 quarts in the sump.
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Good point. My filter and lines are empty at this point, so I'll add one more quart to account for this.

Thanks for all the feedback. We'll see what she weighs today.
 
Don’t overcomplicate this. The reason you do it that was is because there has to be some kind of standard. A weight and balance is supposed to include undrainable fuel and full engine fluids.

If it has 6 quarts in it, sit two more on the cowl over the engine to weigh it.
 
Desert Rat said:
Don’t overcomplicate this. The reason you do it that was is because there has to be some kind of standard. A weight and balance is supposed to include undrainable fuel and full engine fluids.

If it has 6 quarts in it, sit two more on the cowl over the engine to weigh it.
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It is acceptable to do it with full oil or no oil as long as it is noted on the W&B report. Most people use the full oil method to avoid having to add the weight of the oil every time they do a W&B.
 
Mel said:
It is acceptable to do it with full oil or no oil as long as it is noted on the W&B report. Most people use the full oil method to avoid having to add the weight of the oil every time they do a W&B.
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Yes, I understand, but the point is there has to be some sort of standard that you can start from.

Full or empty are valid starting points, “about 6 quarts” isn’t.
 
Desert Rat said:
Yes, I understand, but the point is there has to be some sort of standard that you can start from.

Full or empty are valid starting points, “about 6 quarts” isn’t.
Click to expand...
It CAN be standard for your airplane; again, if it is noted on the W&B report.
 
27-years ago, I weighed my airplane with 4 quarts of oil and that is noted on the weight and balance report. I would never fly the airplane with less than 4-quarts of oil and the only way the airplane would be in the air with less than 4-quarts is if something happened to the engine during flight and got rid of the oil. I also weighed the airplane with unusable fuel. (1/2 gallon each tank is unusable on MY airplane.)

The weight of extra oil will help move the CG. The weight of additional oil is not a big factor for the airplane but the Center of Gravity is. It is very easy to get to an aft center of gravity limit with baggage and fuel burn. On my airplane, CG moves aft 0.5" going from full to empty tanks. By using the minimum oil I would fly with for my weight and balance, it helps keep the airplane forward of the Aft CG limit when I add my normal oil level and baggage that I would use on a trip. Adding more oil moves the CG forward with only a few pounds of extra oil weight.
 
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