BeechTalk - BT

Username Protected · **Posted:** 03 Feb 2018, 21:56

Username Protected wrote:

So what happens when folks move around in a light cc plane during various phases of a flight? Can you get into a fatal out-of-CG state?

My theory is that CG constraints are largely based on elevator authority, and hence should only really be limiting at low speeds (take-off & landing), not during all various phases of flight. It's not like someone moving around in cruise is going to create an unflyable plane. In any case, I've never found the CG to limit where passengers can sit in the 340. I usually try out the extreme situations (heaviest pax in the back or front) to be sure of that. The only cases where I've noticed a potential issue was with 4 passengers and limited baggage. On any normal trip, the nose will be loaded up with baggage that's the most convenient space to store larger suitcases, and then it's hard to get the CG at the aft limit before you exceed the ZFW or gross weight anyway.

Username Protected · **Posted:** 04 Feb 2018, 11:21

Or, weigh it full and subtract the well-known fuel weight.[/quote]
I have found this is prone to error in a variety of ways. Many official W&B sheets I found are wrong simply because the math was done wrong. But there are many other errors, e.g. how full are the tanks really, how warm is it (fuel density changes, did you apply the correction?), are you sure you know the tankage of the airplane, are you sure your mechanic who is doing the weighing knows the tankage, etc...

If you want to actually know, then my opinion is take the time to empty the fuel. Of course, it is possible you don't want to actually know, and then using full fuel gives many opportunities to fudge the numbers to your liking. :cheers:

[/quote]

That's one positive.

Username Protected · **Posted:** 04 Feb 2018, 12:31

Username Protected wrote:

I owned a 340 for 7 years. A few points to keep in mind...

- They are all a little different, so you need to use the specific W&B for the specific aircraft of course. (Hopefully this is a given.)

- They tend to be a little tail heavy, but mine was not ridiculous. I regularly flew with me in the pilot's seat and my wife and 2 kids in the back, with baggage in both the nacelle baggage and rear shelf area. If you have a lot of stuff in the rear shelf area you need to watch the rear CG. But just put some in the nose. 4 adults in back with no one in the co-pilot seat is definitely a scenario you'd have to watch. But if you have 5+ adults on board, you probably have to watch the ZFW and gross weight as well - they are not tremendous load haulers (they do OK but not fabulous).

- When I was shopping for mine, I found a number with fairly egregious problems in calculating the W&B over time. So the CG, in particular, was often way off in the paperwork compared to what I'd expect of reality. But not only the CG, I saw planes weighed with full fuel and then subtract the weight of 203 gals of fuel - except they were configured with only 163 gal tankage. And so on.... Main point being that if you find one that seems dramatically out of whack, it probably is. It is worth spending a few hundred bucks to weigh it. Weigh it empty, make the effort to drain the fuel, you'll get a more accurate result.

So what happens when folks move around in a light cc plane during various phases of a flight? Can you get into a fatal out-of-CG state?

Cessna 340 Weight and Balance