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Have I been doing my weight and balance wrong?

ragedracer1977
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ragedracer1977 Veteran

ragedracer1977

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I downloaded the Garmin Pilot app to try it out, put in all my w&b info.  

To my surprise, Garmin and ForeFlight don’t agree with the weight of the plane or CG when I enter the same numbers.  After some playing around, I figured out it’s because ForeFlight apparently has no way to enter the weight of the oil!  

Anyone know how to fix this?

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carusoam Grand Master

carusoam

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DSo here is where things go down hill...

I pull out my trusty M20C POH...

Warning: Check the aircraft weight and balance before proceeding with the flight. Consult the weight and balance record, furnished in the airplane file, for detailed data needed to calculate load distribution and limitations.

That’s the graph paper that was folded up and stuck in the air frame log on day one.... mine went with the M20C, so I don’t have a copy...

See if @Hank can help you out...

Some bits of data... for the M20C in the POH...

1) MGW... 2575

2) Forward Cg 2100Lbs 42.0”

3) Forward Cg 2575Lbs 46.5”

4) Aft Cg all weights... 49.0”

5) Note... the 0.0 mark... is the nose gear attaching bolt center line... 33” forward of the wing leading edge... at wing station 59.25”

A few notes Loading Information... 10Lbs on the hatrack and 120Lbs in the baggage compartment...

Bummer... no people, no oil, no arms mentioned in the latest POH...

Best regards,

-a-

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Yetti Grand Master

Yetti

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If you have the original sheet from the factory that should help figure things out.    Mine is not close by, but the factory sheet has all those pesky things like oil and fuel and such.   Also if you have the original equipment list. 

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Hank Grand Master

Hank

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The W&B spreadsheet I made for my C does not have Oil as a separate item, but a reference spreadsheet I have for an E does show Oil at -7.4". Seems I don't have the TCDS on my tablet, so I'll have to look for it. Just saw it yesterday on a thumb drive . . . .

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ragedracer1977 Veteran

ragedracer1977

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11 hours ago, hmasing said:

Here's my latest W&B from my F.  While it doesn't have oil called out specifically, it's what I have to offer. 

LoadingSummary.pdfFetching info...

So is yours wrong too? Or is oil included in the empty weight? I know it isn’t in my C, it just never dawned on me that I have 12-16 extra pounds on the nose.

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Ragsf15e Grand Master

Ragsf15e

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Keep in mind the rules/techniques for certificated w&b changed a bit through the 60s and 70s.  Some may not have oil counted in basic empty weight, but later models likely do.

It should include full oil in later models.  Only way to know for sure is read your original documents.

62B30D4A-E673-40EF-8139-3B55EC85325D.jpeg

Edited by Ragsf15e
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EricJ Grand Master

EricJ

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4 minutes ago, Ragsf15e said:

Keep in mind the rules/techniques for certificated w&b changed a bit through the 60s and 70s.  Some may not have oil counted in basic empty weight, but later models likely do.

Yes, the confusion may be because pre-1975 (I'm pretty sure that's when it changed) oil was not included in empty weight and after that it was.    

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PT20J Grand Master

PT20J

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Mooneys were originally certificated under CAR 3 and the empty weight did not include oil. At some point (for sure by the time the M20J was introduced) Mooney started using the GAMA empty weight definition which includes full oil.

You can use either empty weight in your calculations so long as you use the correct corresponding empty CG/moment. 

It’s a simple matter to add a station for oil in Foreflight. Just select Setup and then Edit.

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Ragsf15e Grand Master

Ragsf15e

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11 hours ago, ilovecornfields said:

Has the airplane even been weighed? I would be really surprised if whoever weighed it drained the oil. My plane includes oil in the empty weight, and I would assume that almost every plane that has been weighed includes oil in the empty weight.

I guess the other question would be- does it make a meaningful difference? 

Be careful with that assumption... I rechecked my original documentation after the above discussion.  1968 F model.  They weighed the airplane at the factory and then subtracted the weight of full useable fuel and full oil (15lbs).  This was the first w&b which is the basis for all the rest of the adjustments through the years.  So my weight doesn’t include oil.  I generally use w&b pro app, and I have it set for 10 lbs of oil which is about 6 qts.

For your M20R, I agree, oil is included based on the year of the airplane.  However, they don’t have to drain it to exclude it in the old ones.  Just subtract the weight of 8 qts or whatever amount is in there.

As stated above it depends on year of the airplane.  It’s worth checking the original documents.  Or better yet (maybe) getting it reweighed.  I’m pretty sure there’s bigger mistakes that 10-15 lbs of oil in there!

Edited by Ragsf15e
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Ragsf15e Grand Master

Ragsf15e

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Since we brought this back up, and for future reference, the oil arm is on the tcds.  For the F it is -11.5”.  From the above, it appears that’s different from the E for some reason, but the tcds has the data.

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David Lloyd Mentor

David Lloyd

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New Garmin Pilot user.  For years I used my spreadsheet that had full engine oil included in the empty weight, unlike the the calculation in the operator manuals.  GP has the empty weight with unusable fuel to which you add in the oil, fuel, pilot, passengers, baggage. Well that didn't match my thinking so I found GP has a way to turn the engine oil weight to a fixed value included in the empty weight (bet ForeFlight has the same ability).  After playing around with all the values, realizing how close my airplane with just me and no baggage is to the forward edge of the CG envelope, the weight of only 6 quarts of oil versus 8 does make a difference.  Not much, but enough.

One of the really neat things with the GP versus my spread sheet is the fuel slider button.  Change the fuel from full to empty and watch the dot on the graph move almost parallel to the forward edge of the envelope.  Not quite but almost.  I added my friend's Citabria to my airplane list.  Solo, the CG is way forward.  6 Quarts oil, and 2 in the extended baggage, brings a solo trip back inside the envelop.  Moving the fuel slider, again full to empty, the dot on the graph moves exactly parallel to the forward edge of the envelope.

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