Ground and Flight Testing of a Boeing 737 Center Wing Fuel Tank ...

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Oxygen Concentration (% vol) 25 20 15 10 5 0 Zero Fuel Cross Vented CWT Average Center Bay Average Left Cheek Average Right Cheek Altitude Trace 0 50 100 150 200 250 Time (minutes) FIGURE 17. ZERO FUEL LOAD FLIGHT TEST NEA DISPERSION DATA WITH CROSS-VENTING CONFIGURATION Oxygen Concentration (% vol) 25 20 15 10 5 0 Zero Fuel No Cross Venting Average Center Bay Average Left Cheek Average Right Cheek Altitude Trace 0 50 100 150 200 250 300 Time (minutes) FIGURE 18. ZERO FUEL LOAD FLIGHT TEST NEA DISPERSION DATA WITHOUT CROSS VENTING 21 40000 35000 30000 25000 20000 15000 10000 5000 0 40000 35000 30000 25000 20000 15000 10000 5000 0 Altitude (ft) Altitude (ft)
descent. During descent, the oxygen concentration of the tank rose sharply as expected, as outside air rushed in the vents to equalize pressure between the outside and inside of the CWT. Figure 19 compares the overall average fuel tank oxygen concentration for both tests starting at takeoff. This highlights the effect of eliminating cross venting on the ability to maintain a low oxygen concentration in a fuel tank during flight operations after ground-based inerting. Oxygen Concentration (% vol) 18 16 14 12 10 8 6 4 2 0 Climb and Cruise, 0 Fuel Takeoff at Time 0 Vent Modified for No X Flow No Vent Modification 0 20 40 60 80 100 120 140 160 Time (minutes) FIGURE 19. AVERAGE CWT O2 CONCENTRATION INCREASE COMPARISON PLOT FOR BOTH CROSS-VENTED AND NO CROSS-FLOW FLIGHTS 4.2.2 Fuel Effects at Altitude. To study the effect of fuel load on an inert ullage, figure 18 was employed to establish a baseline of NEA dispersion without cross venting and no fuel in the CWT. The CWT average oxygen concentration increased approximately 1.5% during the ascent and 2-hour cruise. The three remaining flight tests each use the same basic flight profile with three different fuel loads. Figure 20 gives the average oxygen concentration in the three primary areas of the CWT for a flight test using the standard flight profile with a 20% fuel load. The unusually steep increase in average right-cheek oxygen concentration, at approximately 90 minutes and lasting for approximately 30 minutes, could be explained by the large decrease in temperature that bay sees at that point in the flight, but more data is needed to explain this behavior. The average oxygen concentration of the CWT is below 10% for the vast majority of the flight. As fuel is used from the CWT, ambient air flows into the vent system to equalize the pressure, increasing the oxygen concentration in the ullage of the fuel tank. Since the CWT fuel is used first, the increase should 22
Page 1 and 2: DOT/FAA/AR-01/63 Office of Aviation
Page 3 and 4: 1. Report No. DOT/FAA/AR-01/63 4. T
Page 5 and 6: 4. DISCUSSION OF RESULTS 12 4.1 Gro
Page 7 and 8: EXECUTIVE SUMMARY Significant empha
Page 9 and 10: simple fuel tank inerting manifold.
Page 11 and 12: 2.1.2 Instrumentation and Data Acqu
Page 13 and 14: level pressure (14.7 psia) in two s
Page 15 and 16: FIGURE 4. INDUSTRIAL NEA GENERATOR
Page 17 and 18: oxygen concentration. After test 1,
Page 19 and 20: Application of this concept gives t
Page 21 and 22: Inerting Ratio Oxygen Concentration
Page 23 and 24: Both figures 7 and 9 illustrate tha
Page 25 and 26: Oxygen Concentration (% Vol) 20.0 1
Page 27: The effect of fueling on the inert
Page 31 and 32: Oxygen Concentration (% vol) 25 20
Page 33 and 34: Oxygen Concentration (% vol) 18 16

Ground and Flight Testing of a Boeing 737 Center Wing Fuel Tank ...

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