Aft CG..live and learn

pierre smith · #1 07-05-2015, 05:33 AM

My stepson and his girlfriend wanted to see the local area yesterday, so I obliged, since she's a new girlfriend

She climbed in the rear and I leaned the seat back so Aaron could get in but he said, "Pierre I'm sitting in the back so we can take pictures of ourselves."

I told him that I'm afraid we may well have a too far aft CG, then I realized I had about 50 gallons of fuel that's mostly forward of the CG, so we went. Later calculations showed us as 2" forward of the aft limit...good to know but it might have been dicey if we'd flown long enough to burn most of the fuel...I'll calculate that situation as well. With 1 hour of fuel remaining (15 gals.), we still would be within CG by 1 inch, no baggage.

Bear in mind that Aaron is 6'4" and their combined weight around 370#.

With some extra down trim added for good measure, we took off and the airplane flew remarkably solid, no oscillations and was rather fast. Amazing airplane.

Live and learn.

Best,

KRviator · #2 07-05-2015, 06:11 AM

How any people have calculated their ZFW CG before a flight, when you takeoff with the CG towards the aft limit anyway?

I suspect the answer would be "not many"... But it was mandatory for us on the C130's as part of our W&B calculations, just in case.

uk_figs · #3 07-05-2015, 07:05 AM

I built a W&B excel spreadsheet that calculates arrival fuel CG for each flight because on my -7 with 2 up and baggage it can get to aft of the aft CG with low fuel. The CG cells actually turn red when an out of range CG is detected.

Not normally an issue when 1 up going anywhere or 2 up with limited baggage gear for local fly-ins. It is an issue when travelling 2 up going on longer trips (such as Oshkosh to HBC). I use it mostly to manage baggage and plan fuel legs.

Weasel · #4 07-05-2015, 07:07 AM

Fltplan has a nice app for android and iOS that I use. Once it is configured for your airplane you just punch the numbers in and the flight time. It will show CG at take off, landing, and at 0 fuel. I use it all the time if loading an unknown load. It's pretty hard to load my 10 aft cg. I am at the far forward limit when solo.

vic syracuse · #5 07-05-2015, 07:25 AM

The AFS screens have a visual W&B calculator right there in front of you, giving you a visual indication of TO CG and CG at the planned fuel burn landing. No excuse for not using it before every flight.

Vic

Chkaharyer99 · #6 07-05-2015, 08:39 PM

Quote:

Originally Posted by vic syracuse

The AFS screens have a visual W&B calculator right there in front of you, giving you a visual indication of TO CG and CG at the planned fuel burn landing. No excuse for not using it before every flight.

Vic

I also have an AFS and find this function very informative. Still haven't flown with a passenger in back yet but before I do I will certainly use this function to ensure I am within the limits on takeoff as well as landing.

Thanks for the thread Pierre. Serves as a good reminder. Glad you were within specs.

So how'd she handle compared to your normal load out?

pierre smith · #7 07-06-2015, 04:54 AM

Quote:

Originally Posted by vic syracuse

The AFS screens have a visual W&B calculator right there in front of you, giving you a visual indication of TO CG and CG at the planned fuel burn landing. No excuse for not using it before every flight.

Vic

Unfortunately, I have the dinosaur D100, Vic. Gotta do it with calculator and pencil. I had done gross weight CG and forward CG calcs before, so I had a fair idea of what differing loads would do. We all need to practice CG calcs more often anyway.

Best,

Lindy · #8 07-06-2015, 09:59 AM

ForeFlight has a weight and balance calculator also. Pretty easy to set up and use. It is under the "More" tab at the bottom, then select Weight and Balance from the list. Gives a graphical depiction of where you are in the envelope at Takeoff, landing and zero fuel.

Raymo · #9 07-06-2015, 01:21 PM

Quote:

Originally Posted by Lindy

ForeFlight has a weight and balance calculator also. Pretty easy to set up and use. It is under the "More" tab at the bottom, then select Weight and Balance from the list. Gives a graphical depiction of where you are in the envelope at Takeoff, landing and zero fuel.

"ForeFlight has a weight and balance calculator" ... if you purchased the Pro option.

I use the Aviation W&B iPhone/iPad app for a $10 one time fee rather than the annual FF fee.

Also have a spreadsheet to do more detailed calculations on my PC.

TroyBranch · #10 07-06-2015, 01:57 PM

We just did a trip to Johnson Creek in the 10 and weighed everything going in. Did the weights on the AFS and we were .2 forward of aft CG at empty tanks. We had the two kids and the dog in the back. Plane flew just fine. The full to empty weight on the tanks do not change the numbers very much. It is the luggage in the back that really pushes it aft. I also find the full aft luggage makes the pedals a bit more sensitive holding the line in gusty conditions on the ground.