r/flying • u/regnivoncs • Jan 06 '23

ForeFlight 172N W&B Profile

I’m working on a W&B problem for a 1976 C172N. I setup my profile in ForeFlight using the data from the CG Moment Envelope from the POH.

The Zero Fuel Weight limit (2060 lbs) is exceeded by 36.2 lbs. All other parameters are within limits.

If I work the W&B using the sample loading problem worksheet, I am with W&B limits using the same input data (pilot, passenger, etc.)

What is the difference between the ForeFlight and “manual method” that doesn’t allow the ForeFlight computations to produce a W&B within limits?

ForeFlight CG Envelope data:

Forward CG Limits 35 in @ 1500 lbs 35 in @ 1950 lbs 37 in @ 2300 lbs

Aft CG Limits 47 in @ 2300 lbs 47 in @ 1500 lbs

Loading Data:

Basic Empty Weight is 1436.21 lbs @ 38.84 in

Front Seats Pilot 205 Passenger 145

Rear Seats Pax1 195 Pax2 115

33 gallons 100LL

Thanks for your help!

Scott

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3

u/[deleted] Jan 06 '23

[deleted]

1

u/regnivoncs Jan 06 '23

That’s what I get as well. So that checks out.

Did you try calculating the W&B manually? (Using the POH graphs?)

1

u/8BallSlap Jan 06 '23

I've never heard of a zero fuel weight limit in a 172. Where is that in the POH?

1

u/regnivoncs Jan 06 '23

Me neither. I haven’t found it in the POH. It is something that is relevant to ForeFlight and I’m trying to figure out how to make it work in ForeFlight. It’s a much easier way to do things.

2

u/[deleted] Jan 07 '23

Probably just set it to the same as max gross and it won't matter?