KC-135TestInstruction.pdf.pdf

TO 6J3-4-112-3

CHAPTER 7

TESTING

7.1 GENERAL.

This chapter contains information for testing the fuel con-trol assembly. Included are test setup requirements and instructions for performing operational checks. Tests are performed to make certain the assembly has been properly overhauled and will fulfill the established operating requirements for the assembly. Reference should be made to troubleshooting requirements (paragraph 7.4) for aid in determining a possible cause and remedy for malfunctions encountered during testing.

7.2 CALCULATIONS.

When calculations are required to convert certain observed values to standard values, the necessary instructions, charts, curves, tables, or other pertinent data are provided in the text.

7.3 TEST PROCEDURES.

The fuel control assembly shall be calibrated and tested in accordance with the following procedures:

NOTE

• Prior to testing, the fuel control assembly shall be inspected for loose or improper assembly, dirt or other contamination.

• An assembly that does not meet the test parameters specified herein shall be rejected.

• Reworked fuel control assemblies, to correct faults found in testing, shall be retested.

• Fuel control assembly may be received with or without fuel pump. If received without a fuel pump, attach a slave pump.

7.3.1 Fuel Pump Test. The fuel pump shall be tested in

accordance with the following procedures.

a. Mount fuel pump to fuel control test bench, 285304-1-1 (Figure 2-1, 1), and connect appropri-ate inlet and discharge lines (see Figure 7-1 for test setup).

WARNING

Do not close off high pressure valve at 600 psig or damage could result to equipment and injury to personnel.

b. Apply 10-20 psig inlet pressure and increase speed to 4200 rpm.

c. Set inlet pressure to 10 psig and discharge pressure at 600 psig.

d. Verify that flow is 921 pph maximum.

e. Decrease speed to 400 rpm.

f. Set inlet pressure to 10 psig and discharge pressure to 200 psig minimum.

g. Verify that flow is 49 pph minimum.

h. Check for leakage, ensuring that leakage rate past the fuel pump inlet drive shaft is no more than one drop per minute over a period of 15 minutes.

i. Remove fuel pump from test bench.

7.3.2 Test Setup. The test setup of the fuel control

assembly is shown in Figure 7-1.

NOTE

A slave fuel pump may be used for testing the fuel control.

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Figure 7-1. Test Setup, Fuel Control Assembly

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7.3.3 Test Requirements.

WARNING

Calibrating fluid, Specification MIL-C-7024, Type II, may affect skin, eyes, and respiratory tract. Use in a well-ventilated area. Avoid pro-longed breathing of vapors. Avoid eye and repeated skin contact. Keep away from sparks and flames.

a. Calibration shall be performed using calibration fluid, Specification MIL-C-7024, Type II.

b. Boost pressure shall be maintained at 10-20 psig for all testing, unless otherwise specified.

c. The fuel control assembly shall be installed on the fuel control test bench, 285304-1-1 (Figure 2-1, 1).

Data required shall be recorded on a data sheet (Figure 7-2).

7.3.4 Bleed.

WARNING

When operating test equipment, wear ear pro-tection. Failure to comply may result in injury to personnel.

a. Open start and main fuel solenoid valves and manual valve V2.

b. Increase current to 100 mA.

c. Increase fuel control assembly speed to 4444 (±20) rpm.

d. Open needle valve (Figure 3-2, 18) on fuel control and bleed air completely.

e. Close needle valve and reduce current to 0 mA.

7.3.5 Servovalve Check.

a. Close start fuel solenoid valve. Leave V2 and main fuel solenoid valve open, current at 0 mA, and fuel control assembly speed at 4444 (±20) rpm.

b. Adjust differential pressure (ΔP) valve (plunger, Figure 3-2, 22) until gage 2 reads 200 psig.

c. Remove Phillip screw under expansion plug (17) on servovalve (14). Save screw for reinstallation after testing.

d. Using a 1/16 inch Allen wrench or 0.033 inch, four-tooth spline wrench, adjust servovalve (14) to obtain 25 (±3) pph flow on the rotometer.

e. If adjustment cannot be obtained, replace servovalve (14) and repeat test.

7.3.6 Relief Valve and Leakage Checks.

a. Increase input current to 100 mA at 4444 (±20) rpm.

b. Close main fuel solenoid valve. The pressure on gage 2 is relief valve full flow pressure (700 psig maximum). Record on data sheet (Figure 7-2).

c. Reduce fuel control assembly speed to 1000 (±10) rpm.

d. Open main fuel solenoid valve. Slowly close V2 until boost pressure (gage 1) begins to increase rapidly. Repeat several times to ensure that boost pressure is increasing rapidly. The pressure on gage 2 is relief valve cracking pressure (475-550 psig). Record on data sheet (Figure 7-2).

e. If relief valve does not fall into limits, replace body assembly (5) and relief valve (35).

f. Close main fuel solenoid valve. Visually check for leakage past the start and main fuel solenoid valves by disconnecting the lines at the fuel control.

Monitor leakage for approximately 1 minute Record on data sheet (Figure 7-2). If leakage is in excess of above limit, replace faulty valves.

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Figure 7-2. Data Sheet

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7.3.7 Low Speed Performance.

a. Open start fuel solenoid valve and V2 (main fuel solenoid valve closed). Adjust input current to 0 mA.

b. Reduce fuel control assembly speed to 444 (±5) rpm and record flow on the flow meter and pump discharge pressure on gage 2 on data sheet (Figure 7-2).

c. Maintain fuel control assembly speed at 444 (±5) rpm. Open main fuel solenoid valve. Record same parameters as in step 2 on data sheet (Figure 7-2).

d. Increase fuel control assembly speed to 622 (±5) rpm. Record same parameters as in step 2 on data sheet (Figure 7-2).

e. Maintain fuel control assembly speed at 622 (±5) rpm. Close main fuel solenoid valve. Record same parameters as in step 2 on data sheet (Figure 7-2).

7.3.8 Calibration.

a. Open main fuel solenoid valve and close start fuel solenoid valve (V2 open). Adjust current to 100 mA.

b. Increase fuel control assembly speed to 4444 (±20) rpm.

c. Adjust ΔP (Figure 3-2, plunger 22) valve to obtain 370-425 pph flow.

d. Reduce input current to 0 mA

e. Adjust servovalve to obtain 25 (±3) pph flow.

f. Repeat adjustments at 100 and 0 mA until the flow is in the proper range at both ends.

g. Record flow at 0, 20, 40, 60, 80, and 100 mA and plot (Figure 7-3). Points must lie between limits indicated by the dotted lines, unless otherwise noted.

NOTE

If performance verification is to be accom-plished per paragraph 7.3.9, record flow with decreasing current. Do not plot. Determine maximum hysteresis (difference in flow with increasing and decreasing current).

7.3.9 Performance Verification.

a. Perform calibration per paragraph 7.3.8 prior to performance verification.

b. Open main fuel solenoid valve and close start fuel solenoid valve (V2 open). Adjust current to 100 mA.

c. Fuel control speed set at 4444 (±20) rpm.

d. Obtain a hysteresis loop of fuel flow versus current required (see Figure 7-4 for sample plot). Input current to be 0-100 mA at a linear triangular speed of 0.01 Hz. Record maximum hysteresis on data sheet (Figure 7-2).

e. Determine sensitivity by slowly increasing input current manually until flow increases. Then slowly decrease input current until flow decreases. Record change in current required to produce a change in flow on data sheet (Figure 7-2).

f. Disconnect XY plotter and reduce fuel control assembly speed to 0 rpm.

g. Determine linearity (see Figure 7-4 for sample plot) and record on data sheet (Figure 7-2). Use increasing (lower) curve only.

7.3.10 Alternate Performance Verification.

NOTE

If alternate performance verification is to be accomplished per paragraph 7.3.10, record flow with decreasing current. Do not plot. Determine maximum hysteresis (difference in flow with increasing and decreasing current).

a. Perform calibration per paragraph 7.3.8 prior to alternate performance verification.

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Figure 7-3. Fuel Control Calibration Limits

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Figure 7-4. Test Data, XV Plotter

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b. Determine linearity by drawing the most favorable straight line (equal current deviations on both sides of the line) through the points plotted in paragraph

7.3.8. Record maximum current deviation from the

straight line on the data sheet (Figure 7-2).

c. Determine sensitivity by noting the current change required to produce a change in flow when increas-ing and decreasing current above and below 50 mA. Record maximum current change on the data sheet (Figure 7-2).

7.3.11 Installation of Expansion Plugs.

a. Install Phillip screw (6-32 inch) on servovalve (Figure 3-2, 14).

b. Install expansion plugs (17 and 21) after comple-tion of calibration and testing.

WARNING

Lubricating oil, Specification MIL-L-6081, Grade 1010, may cause skin rash. Do not breathe vapors. Use in well-ventilated area.

Wear eye protection and gloves. Failure to comply may result in injury to personnel.

NOTE

If either expansion plug is removed, the fuel control assembly shall be retested to meet requirements.

c. Using soft-ended drift punch, flatten expansion plugs (17 and 21).

d. Apply lubricating oil, Specification MIL-L-6081, Grade 1010, to threads of plug (Figure 3-2, 1) and torque to 90-100 inch-pounds.

e. Safety wire servovalve (14) using lockwire, MS20995C20.

7.4 TROUBLESHOOTING PROCEDURES.

Refer to Table 7-1 for troubleshooting procedures for the fuel control and fuel pump.

7.5 PRESERVATION AND SHIPPING.

Preservation and storing or shipping procedures for the fuel control assembly are as follows:

WARNING

Lubricating oil, Specification MIL-L-6081, Grade 1010, may cause skin rash. Do not breathe vapors. Use in well-ventilated area.

Wear eye protection and gloves.

a. Partially fill the fuel control assembly with lubrica-ting oil, Specification MIL-L-6081, Grade 1010.

b. Close all ports and rotate fuel control assembly as a unit to uniformly coat all interior surfaces.

c. Rotate fuel pump drive shaft to ensure gears and bores are well protected.

d. Remove all protective caps and plugs from ports and drain excess oil.

e. Install protective caps and plugs to prevent entry of foreign objects and to prepare for shipping or storage.

f. Insert layer of Kimpak filler, Specification MIL-P- 26541, in the bottom of a cardboard container, Specification MIL-P-38721.

g. Wrap fuel control assembly in Kraft paper, Specifi-cation MIL-P-17667, Grade A, and place in a plastic bag. Tape bag closed with masking tape, Specification MIL-T-21595.

h. Place fuel control assembly in cardboard container, Specification MIL-P-38721, and place six units of desiccant, Specification MIL-D-3464, around fuel control assembly.

i. Fill remainder of space around fuel control assem-bly with Kimpak filler, Specification MIL-P- 26541.

j. Close cardboard container, Specification MIL-P- 38721, and seal flaps closed with masking tape, Specification MIL-T-21595.

k. Attach label to outside of container identifying component nomenclature, part number, and date of repair.

l. Store fuel control assembly in dry, enclosed area.

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