Fuel

Question 1

FUEL_001

Recall the function of the DC start pump:

Answer 1

• A DC Start Pump, operated by the START PUMP switch on the overhead panel, is installed in the right main tank and is used for APU or engine starting when AC power is not available.
• ON – Supplies power from 28VDC TRANSFER BUS to power start pump.
• OFF – Disconnects 28VDC power from start pump.
• The start pump does not have overheat protection, but is cooled by fuel in the right main tank.

Question 2

FUEL_002

(90) Recall the function of the Return To Tank system (RTT) on the MD-90:

Answer 2

• The return to tank (RTT) system provides fuel lines which allow the engine heat management system to return fuel heated by the engine and generator fuel-oil heat exchangers to the main fuel tanks.
• RTT reduces the likelihood of wing ice caused by coldsoaked fuel while improving the efficiency of the engine heat management system.
• Overwing heaters are not installed on the MD-90 due to the RTT system.

Question 3

FUEL_004

Recall that fuel may be transferred on the ground but not in flight:

Answer 3

The CENTER TANK PUMPS switch on the Fuel load control panel under the right wing enables fuel to transfer from center tank when defueling valve is open and fill valve of selected tank is opened.

Question 4

FUEL_005

Explain how fuel is supplied to the engines with all pumps operating:

Answer 4

• Each main fuel tank has two AC boost pumps installed in parallel.
• An interconnect system and crossfeed valve between the fuel tank systems permits use of fuel from either main fuel tank to both engines.
• The two AC center tank pumps are connected in series to provide pressure higher than that of the main tank pumps, and ensure usage of the center tank fuel even with both main tank pumps operating.

Question 5

FUEL_008

Recall the engine driven fuel pumps are capable of suction feeding fuel to the engine.

Answer 5

The engine driven fuel pumps are capable of suction feeding fuel to the engine from the main tanks only.

Question 6

FUEL_009

Explain the use of the auto position on the center tank fuel switches for alternate fuel burn:

Answer 6

• When both pump switches are in the AUTO position, the Alternate Fuel Burn (AFB) system will be active.
• The AFB system energizes the center tank fuel boost pumps when the center tank fuel quantity is greater than the internal float switch level.
• Automatic switching to main tanks occurs when the center tank quantity decreases to approximately 10,000 pounds (MD-88) or 3,000 pounds (MD-90).
• The center tank fuel boost pumps are re-energized when either main tank fuel quantity is approximately 4,000 pounds (MD-88) or 4,800 to 3,800 pounds (MD-90).
• Switches should be ON for start, taxi and takeoff and placed to AUTO after takeoff (if applicable).
• Do not use the AUTO position for any inoperative boost pump or any abnormal quantity indications.

NOTE: Alternate Fuel Burn is not required on MD-88’s with operable overwing heater blankets, nor with MD-90’s with operable Return To Tank (RTT) system.

Question 7

FUEL_010

(88) What is the correct response of the quantity display during a fuel quantity test on an MD-88?

Answer 7

• During test, each tank digital readout displays 3,000 ± 100.
• Total Fuel displays 9,000 + 300.
• GROSS WT displays ZFW plus 9,000 ± 300.