Spark Ignition Aircraft Engine Endurance Test of Aviation ... - FAA

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At the beginning of the test and after every 50 hours of engine operation an oil sample was taken and analyzed for viscosity changes, fuel dilution, acidity, and metals concentration. The results are shown in table 10. Test Method Table 10. Oil Analyses Sample Date (2005) 8/18 9/6 9/19 10/11 10/20 10/31 Eng. Hours 9.3 49.9 50.2 50.6 29.2 33.5 Description Engine Break-In 20W-50 Mineral Oil 15W-50 Ashless Dispersant 15W-50 Ashless Dispersant 15W-50 Ashless Dispersant 15W-50 Ashless Dispersant 15W-50 Ashless Dispersant Acid Number, mg ASTM D 664 KOH/g 0.7 1.9 1.8 1.5 1.3 1.5 ASTM D 445 Viscosity, mm²/s 40°C 132.7 179.1 182.8 164.9 145.1 142.0 100°C 16.90 22.54 22.68 21.07 19.44 19.23 ASTM D 3525 Fuel Dilution, mass % 0.09 0.08 0.06 0.06 0.07 0.41 JOAP Metals by Arc Spark, parts per million Iron 13 32 28 22 13 18 Lead 4 11 10 10 5 7 Copper 18 33 20 16 12 15 Chromium 4 5 4 3 2 3 Aluminum 8 27 26 20 11 13 Nickel 1 4 2 2 1 1 Tin 2 10 6 5 3 3 Silicon 8 8 7 5 3 4 Sodium 10 15 11 15 7 9 Zinc 14 13 9 7 5 5 Calcium 15 8 4 4 3 3 Magnesium 1 3 1 1 1 1 Molybdenum 1 1 - - - - Potassium 73 19 7 6 6 7 Phosphorous 27 304 333 388 352 334 KOH = potassium hydroxide The oil analyses indicated that neither fuel dilution nor oil degradation had occurred. The acid number of the oil was low and showed a level trend, and the same trend occurred with the oil viscosity. Fuel dilution was measured to be less than 0.1%. The metals analyses showed low values and declining trends, which is a normal wear pattern. The high levels of phosphorous were from phosphorous-based oil additives. 27
The oil filter was cut open and the filter medium was inspected for metal particles, as previously shown in figure 1. No significant amount of metallic particles were found at any of the inspection intervals. Table 11 lists the valve recession measurements. The first row of the table for a given date shows the initial depth of the valve stem, as measured with a micrometer. The second row shows the second valve stem height measurement with the number of engine hours listed since the last measurement. The third row shows the change in valve depth from the original measurement with the number of engine hours listed since the initial measurement. Table 11. Valve Recession Measurements Intake Valves (inches) Exhaust Valves (inches) Date Engine Hours Test Hours 1 2 3 4 1 2 3 4 8/18/2005 9.3 0.0 1.4300 1.4280 1.4310 1.4270 1.4850 1.4790 1.4870 1.4900 9/6/2005 59.2 49.9 1.4295 1.4270 1.4310 1.4270 1.4810 1.4730 1.4820 1.4860 wear/49.9 0.0005 0.0010 0.0000 0.0000 0.0040 0.0060 0.0050 0.0040 9/19/2005 109.4 100.1 1.4290 1.4280 1.4310 1.4275 1.4750 1.4660 1.4750 1.4820 wear/50.2 0.0005 -0.0010 0.0000 -0.0005 0.0060 0.0070 0.0070 0.0040 wear/100.1 0.0010 0.0000 0.0000 -0.0005 0.0100 0.0130 0.0120 0.0080 10/13/2005 160.0 150.7 1.4290 1.4270 1.4310 1.4270 1.4700 1.4620 1.4710 1.4780 wear/50.6 0.0000 0.0010 0.0000 0.0005 0.0050 0.0040 0.0040 0.0040 wear/150.7 0.0010 0.0010 0.0000 0.0000 0.0150 0.0170 0.0160 0.0120 10/25/2005 189.2 179.9 1.4290 1.4270 1.4310 1.4270 1.4670 1.4580 1.4670 1.4760 wear/29.2 0.0000 0.0000 0.0000 0.0000 0.0030 0.0040 0.0040 0.0020 wear/179.9 0.0010 0.0010 0.0000 0.0000 0.0180 0.0210 0.0200 0.0140 10/31/2005 193.5 184.2 1.4290 1.4270 1.4310 1.4270 1.4660 1.4580 1.4670 1.4750 wear/4.3 0.0000 0.0000 0.0000 0.0000 0.0010 0.0000 0.0000 0.0010 wear/184.2 0.0010 0.0010 0.0000 0.0000 0.0190 0.0210 0.0200 0.0150 Figure 28 shows the exhaust valve recession plotted versus total engine hours. The change in valve recession was consistent over time and did not show accelerating wear. The total intake valve recession was less than 0.001 inch, and the average exhaust valve recession over the 150- hour test was found to be 0.01875 inch with a maximum value of 0.0210 inch in cylinder 2. These values are on the high side of the normal expected range for a test this severe and this duration. Both the exhaust valve faces and exhaust valve seats showed a hammered effect, which was partly due to the necessity of running the engine with the ignition timing retarded by 5°. 28
Page 1 and 2: DOT/FAA/AR-06/43 Office of Aviation
Page 3 and 4: 1. Report No. DOT/FAA/AR-06/43 4. T
Page 5 and 6: LIST OF FIGURES Figure Page 1 Oil F
Page 7 and 8: 46 Posttest Connecting Rod Bearing
Page 9 and 10: LIST OF ACRONYMS 100 low-lead 100LL
Page 11 and 12: more fuel volume flow. Future tests
Page 13 and 14: At the completion of the test, the
Page 15 and 16: The engine was installed in a test
Page 17 and 18: Table 4. Parameter Settings for End
Page 19 and 20: Figure 1. Oil Filter Inspection Fig
Page 21 and 22: Figure 4. Corrected Power at 2700 r
Page 23 and 24: Figure 8. Corrected Power at 2300 r
Page 25 and 26: Figure 10. Corrected BSFC vs Fuel M
Page 27 and 28: Figure 12. Corrected Power and Aver
Page 31 and 32: Table 8 provides a summary of the e
Page 37: output from all six cylinders. Pist
Page 41 and 42: Figure 29. Top of Piston Face of Cy
Page 43 and 44: Figure 33. Bottom of Piston Face an
Page 45 and 46: Figure 39. Posttest Crankshaft Conn
Page 47 and 48: The camshaft lobes, shown in figure
Page 49 and 50: Figure 59 shows a combustion chambe
Page 51 and 52: Figure 63. Posttest Rocker Arm Show
Page 53 and 54: Visual observation of the intake tu
Page 55 and 56: Future testing should address effec
Page 57 and 58: Table A-2. Middle and Rear Main Cra
Page 59 and 60: Table A-4. Valve Tappet Outer Diame
Page 61 and 62: Table A-10. Top Piston Ring Side Cl
Page 63: Table A-14. Intake Valve Seat Width

Spark Ignition Aircraft Engine Endurance Test of Aviation ... - FAA

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