BMS F-16C/D 4.34, Руководство по эксплуатации самолета

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T.O. BMS1F-16CM-1 BMS 4.34 Change 2.00
BMS 4.34 Dash 1
© Red Dog 2012-2019
Page: 126
1.7.7. Fuel imbalance
It should come as no surprise that aircraft behaviour in the air is heavily influenced by the position of
its centre of gravity. Obviously the centre of gravity moves according to the way the aircraft is loaded.
In this way fuel load and fuel transfer will greatly impact the centre of gravity position. The CG moves
along two axes depending on the load and must remain within certain limits for the aircraft to remain
controllable. In the same way asymmetric weapon loadouts induce the heavy wings to drop, a fuel
heavy wing will drop as well.
Fuel transfer can also induce a forward or aft shift of the CG if there is only one of the two fuselage
tanks feeding the engine. In that case the fuselage fuel load does not decrease evenly in the front or
rear of the aircraft and the CG will move accordingly. This CG longitudinal shift is much more subtle
than left & right shift because it often goes unnoticed but may induce quicker departure at higher AOA,
especially dangerous for aerobatics, approach and landing.
We can therefore define two types of imbalance and luckily the least dangerous one will probably
happen before the more dangerous one, which will help you to correct it before it becomes serious.
Since the left and right side empty first into the fuselage any kind of imbalance happening soon after
takeoff will probably induce a shift of the CG to the left or to the right, inducing a roll which can be
neutralized with the aileron trim in the exact same way an asymmetrical loadout is compensated.
That roll will be noticed before the external wing tanks are empty and if you succeed in overcoming the
temptation to check the possibility of joystick drift, you will probably realise something is wrong with
your load. Since your weapons
haven’t been dropped yet you should think about a potential fuel
imbalance problem.
Furthermore as said above, when one of the wing tanks starts to empty you might get a TRP FUEL
warning signalling that some fuel is trapped in the other external tank. That is your second clue.
If you need a third clue you should consider playing PS3 games
☺
The second type of imbalance will happen when the wing tanks are empty (both external and internal)
and concerns only the internal fuselage tanks. If they empty into the FFP unevenly the difference in
weight will induce a shift of the CG forward or backward.
That imbalance is much harder to detect by simply flying the aircraft and may induce serious problems
in some envelopes of the flight model: the aircraft becomes more prone to departure of controlled flight
under certain AOA.
The only way to detect such a condition early is to check the needles on the fuel quantity gauges as
often as possible. As long as you don’t see the red portion of the needles there is no fuel imbalance
problem. The red portion of the needles becomes visible when the difference between the two needles
is more than 600 lbs.
Remember you may not feel this kind of imbalance before it
is too late. That is why Ops checks are so important.
Aft CG saves fuel, but forward CG makes the aircraft more
responsive to pilot input (when staying within the
established %Mac CG loading of course).