.
From the loading point of view the aft limit must be as aft as possible.
For aft CG limits, there is no need for a compromise between loading operations and
performance.
Only the structural limitations and the handling quality will be taken into account when
establishing the aft limit of the CG envelope.
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
A. GENERALITIES
4.7.2. Landing limits
The limitations that apply for take-off also apply for landing.
Nevertheless at landing the aircraft weight is lower than at take off so some limitations are not as
restrictive as for take off.
In addition the nose wheel adherence does not generate a limitation.
a) Forward limit
The forward landing envelope is superimposed on the take off one.
b) Aft limit
The aft landing envelope could usually be set aft of the take off one (less restrictive) . Depending on the aircraft type and on the fuel vector shape it might be useful or not to extend the landing aft limit, so the aft landing envelope is :
. either superimposed of the take off one, (fig1)
. or set aft of the take off one (fig 2).
Fig1 Fig2
A. GENERALITIES
4.7.3. In flight limits
a) Forward limit
The design of the forward limit takes into account the following: . Fuel consumption . Efficiency of the elevator . THS stall
b) Aft limit
The design of the aft limit takes into account the following: . Point at 1° per g. . Stability in steady flight and during maneuvers . Go-around and Alpha Floor
Those limitations are classified as handling quality and structural limitations
.
From the performance point of view the forward and aft limit of the envelope must stayas aft as possible to reduce fuel consumption.
.
From the loading point of view the operational limit must be as wide as possible.
Usually the in-flight phase is less limiting than the take-off one as limiting factors such as high weights; low speeds and TOGA are specific to take-off phase. During cruise (flight phase), the passenger movements modify the aircraft CG, so during this phase to check the aircraft CG against the in flight envelope those slight CG position modifications must be taken into account.
Consequently, the in-flight envelope is chosen with respect to the take-off one. . Opening this envelope as much as possible is useless as the CG is constrained by the T/O phase.
. Choosing the in-flight envelope of the same size as the take-off one is too restrictive. Indeed, because of the passenger movements during cruise the in flight envelope becomes more limiting than the take off one.
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本文鏈接地址：Getting to Grips with Aircraft Weight and Balance(49)
