While enroute, will the CG change as your aircraft uses fuel?

Question

While enroute, will the CG change as your aircraft uses fuel?

Answer 1

Beech Bonanzas/Barons have significant CG shifts with fuel burn.  It is extremely possible to take off within the CG envelope and land AFT of the envelope limit.  The result is decreased stability in elevator control.  Many pilots have been surprised by the extremely ‘touchy’ elevator feel on landing after long flights.  For those airplanes in particular, it is a MUST to calculate both take-off and landing CG.

You're DEAD wrong if you don't believe the CG can move to the rear as the fuel from the MAIN wing tanks is used.  Do some trials with this site:

http://www.csgnetwork.com/a36bonanzawbca...

Answer 2

Simple answer - yes. However the magnitude of the cg shift will vary depending on what type of aircraft it is. Small, single engine aircraft with a single fuel tank, will experience a negligible change in cg position as the fuel burns down - and thus no noticeable change in aircraft handling.

However, a heavy multi-engine aircraft with many fuel tanks may experience a significant cg shift as it burns fuel. If managed incorrectly, this can lead to handling quality problems as the cg position moves to its forward/aft limits. To manage this, the onboard fuel system computers will ensure that fuel is burned from tanks in a particular sequence - which keeps the cg position within a narrow band.

Each aircraft will move it's cg position differently as it burns fuel - the main factors are size and location of the fuel tanks, and the sequence of fuel tanks used during the flight.

Answer 3

Yes !

Answer 4

yes but negligible, unless you have a trim tank which is in the tail (horizontal ) section of the airplane. I mean we're talking about wing tanks and center tank only.

Answer 5

Oh yes, but it depends on the aircraft.  Yer average light aircraft will barely notice it as the tanks are close to the CG anyway.

Answer 6

It most certainly will. In larger aircraft, for instance the now retired concorde, trim tanks were incorporated into the design to supplement the trim controls.

Have a look at the first link for an article that discusses the shift of fuel in the concorde.

The second link is a previous related question.

Answer 7

Yes.  Compute the CG with full tanks and with empty tanks.  Compare.

Answer 8

heres a short answer but thats all u need to know,,  ofcourse it will change as fuel is being burnt,,  but if the cg was within limits before engine start its gona remain within limits as long till the last drop of fuel, on one condition that baggage's and passengers stay were they are

Answer 9

Yes, but the amount of CG change depends on the plane.  Light piston personal planes have only wing tanks and have straight wings, so the CG shift is negligible unless the plane has multiple tanks (wingtip tanks, auxiliary tanks, etc).

Swept wing airplanes will have more CG shift.  As the fuel burns down and there is less fuel in the wingtip area, the CG will shift forward.

Many jets have multiple tanks, not just in the wing.  Many have fuselage tanks, or even stabilizer tanks like others have mentioned.  I fly a plane that will burn fuel from the fuselage tanks first (more specifically, burn from the wings and then transfer fuel from the fuselage to the wings).  The CG will shift pretty significantly forward as the fuselage tank begins to empty.  Then the CG will stay pretty linear for a while until the fuselage tank is completely empty.  It will then begin to shift forward again (but not very much - fairly negligible) as the fuel empties from the tanks of swept wings, starting at the wingtips.

Answer 10

Absolutely!

However most fuel tanks are located in the wings, not far from the general vicinity of the Centre of Gravity. This means that the trim changes are usually pretty small, and in light planes, often negligible.

On planes like the Boeing 747-400 though, where you can carry 10 tons of fuel in the stabilizer tank (in the tail), trim changes are large, so there are also strict limitations on how the fuel is distributed.

Answer 11

All swept wing aircraft experience cg changes in flight. As fuel is used the outboard sections empty because of wing dihedral and those areas are way aft of the root. So yes, cg moves forward in flight.

Answer 12

Yes , this is why we calculate CG with full tanks , half full , and near empty. Or at least most people I know do.