388 W&B

Based on the numbers I have at home for arms and empty weight, our Thanksgiving trip easily falls within the moment envelope, even with 80 lbs of make-believe luggage.

	Weight (lbs)	Arm (inches)	Moment (lb-in)
Empty weight	1392.4	37.54	52270.7
Fuel	228 (38 gals*6lbs/gal)	48	10994
Oil	15 (8qts*1.875/qt)	-0.2	-3
Front	290	36	10440
Rear	95	70	6650
Baggage	100	95	9500
Total	2120.4		89.8

That's right smack in the middle of a line that diagonally bisects the envelope long-ways.

If Husband and I each put on 50 lbs eating Thanksgiving dinner, we're still well inside the envelope.

If I flew and Husband sat in the back with the Dog, we'd be ok.

According to the W&B, we'd be okay if all of us sat in the back! (Wait, who's flying?!?!?!)

We'd be ok if we brought one of my Brothers and his luggage back with us. We'd be ok with three adults, one black lab, 120 lbs of luggage and full fuel. And at that, we've just about maxed out the useful room in the plane without exhausting the useful load!

The constraints for 388 are (1) total weight must be less than 2300 lbs, (2) no more than 120 lbs in the luggage area, and (3) total moment must be less than 109 lb-in. It's pretty flexible within those limits. Husband says this is the most flexible plane for which he's ever done the W&B.

But one point of this lesson was to think about the plane crash from Sunday morning. The couple was on vacation and the crash happened on takeoff. Bad loading of the plane can result in bad takeoff performance. In 388 on a calm and comfortable fall day, a gross weight of 1700 lbs (basically me on a solo flight) has a ground run of 435' and it would take 780' to clear a 50' obstacle. JGG is 3200' long, so that's ok.

Load the plane to a gross weight of 2000 lbs and that ground run goes up to 630' or 1035' to clear that 50' obstacle -- up by ~50%.

Max it out at 2300 lbs and those numbers go to 865' and 1525', roughly double the solo numbers.

Max it out at an altitude of 7500' on a cold day and the distance required to clear that obstacle tops 3800'. I wonder if their numbers are for normal or short-field take-off procedures (it doesn't specify, so I'd assume normal).

Based on the numbers in the take-off data chart in the POH (from whence the numbers above also came), weight has a larger effect than altitude, which has a larger effect than temperature (for 388, anyway).

Bad loading can also cause control ineffectiveness of varying degrees. Weight in general affects load factor, which must be regarded during turns and other situations where the plane is physically stressed.