MEC FEEDBACK ARM
RIG NOTCH ATTACHMENT BRACKET SCREW (2 LOCATIONS)OPEN VSV POSITION RIG
CABLE
ADJUSTABLE
POINTER
RIG PLATE
B
G-M56-MM-0159(1)-00-B C
Variable Stator Vane (VSV) Feedback Cable Adjustment
Figure 506
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(c)
Tighten the locking bolt for the VSV trimmer bracket to 32-35 pound-inches (3.6-4.0 Newton meters).
(d)
Make a record of the temperature (in shade of nose gear wheel well) and pressure at the location.
(e)
Make sure the applicable ENG ANTI-ICE and BLEED switches are in the OFF position.
(f)
Use the Power Plant Operation (Normal) procedure to start the engine (AMM 71-00-00/201).
(g)
At the maximum N2 motor speed before you apply the fuel and ignition, do the steps that follow:
(h)
Make sure the VSV's stay in the closed position.
NOTE: If the VSV's are not at the closed position stop at the
____ maximum N2 motor speed, adjust the feedback adjustment screw. Turn the screw clockwise (CLOSED) until the VSV is closed (35.4-37.2 degrees).
(i)
Make sure the VSV indicator reads 35.4-37.2 degrees.
(j)
Let the engine become stable at ground idle for 3 minutes.
(k)
Make a record of the N1 and N2 values.
(l)
Make sure the VSV's are in the limits and calculate N2K25.
1) If the VSV's are not in the limits, do the engine shut-down and do the steps for the adjustment of the VSV bellcrank assembly to the actuation rings again.
2) Calculate T25.
a) Use the N1 value that you wrote down to find .T25
(booster temperature rise) from Fig. 503.
b) T25 = .T25 + ambient temperature.
3) Calculate the corrected N2K25.
a) Use T25 to find correction factor in Fig. 504.
b) N2K25 = N2 value x correction factor (CR)
4) Find the limits for the VSV position (Fig. 505).
NOTE: The higher VSV angle is more CLOSED and the lower
____
VSV angle is more OPEN.
(m)
Increase the engine speed to the Maximum Power Assurance (MPA) adjustment, (AMM 71-00-00/501, Test No. 5), and let the engine become stable for 3 minutes.
(n)
Make a record of the N1 and N2 values.
(o)
Make a record of the VSV position from the indicator.
(p)
Decrease the engine speed to flight idle and let the engine become stable for 2 minutes.
(q)
Make a record of the N1 and N2 values.
(r)
Make a record of the VSV position from the indicator.
(s)
Decrease the engine speed to ground idle and let the engine become stable for 3 minutes.
(t)
Make a record of the N1, N2, and VSV position values.
(u)
Do an Acceleration Time Check (AMM 71-00-00/501, Test No. 8).
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CFM56 ENGINES
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(v) Calculate the N2K25 and the VSV position for ground idle,
flight idle, and MPA data.
1) Calculate T25.
a) Use the N1 value that you wrote down to find .T25 (booster temperature rise) from Fig. 503. b) T25 = .T25 + ambient temperature.
2) Calculate the corrected N2K25. a) Use T25 to find the correction factor in Fig. 504. b) N2K25 = N2 value x correction factor (CR)
3) Find the limits for the VSV position (Fig. 505).
NOTE: The higher VSV angle is more CLOSED and the lower
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