DQ-125

Question 1

• Describe the primary functions of the Hydromechanical Unit that affect fuel flow metering.
• Describe the other HMU functions that do and do not affect fuel flow.

Answer 1

Affect fuel flow:

• Pumps fuel @ high pressure
• Meters fuel in responce of PAS and LDS
• Collective pitch compensation through LDS
• Accel/decel fuel flow. Prevents comp stall/flameout
• Ng limiting. Limits MTA @ low temp

Do not affect fuel flow:

• Variable geo position of inlet guide vanes
• ECU/DEC Lockout
• TQ motor to trim Ng output
• Open vapor vent for HMU purging

Question 2

Describe the primary functions of the Overspeed and Drain Valve

Answer 2

• Sequences fuel through the main fuel manifold to the injectors for starting acceleration and engine operation.
• Purges fuel from the main fuel manifold on shutdown to prevent coking.
• Shuts off fuel flow to prevent an engine overspeed (120% ±1%) when the overspeed system is sensed by the DEC.
• Shuts off fuel to prevent hot starts when activated by the hot start preventor (HSP).

Question 3

The Enhanced Digital Engine Control (EDECU) incorporates what feature not found on a DEC?

Answer 3

• Upon power up, the EDECU will send a signal validation to the associated engine torque meter indicating its configuration, 20 seconds after initial application of ac power. (15% / 25%)
• The TGT limiting system limits fuel flow when the TGT TEMP reaches the dual engine 10 minute limiting value of approximately 866ºC.
• Activates a contingency limit (higher TGT limiting value) when both EDECUs sense excessive rotor/Np droop.
• On engines with the EDECU (DAS plug connected), the dual engine 10 minute limiting value will automatically switch to the higher single engine 2.5 minute limiting value, when any of the following conditions apply:
  • % RPM 1 or 2 drops below 96%.
  • Greater than 3% droop between reference Np and actual Np.
  • Greater than 5% per second Np droop rate exists and Np less than or equal to Np reference speed.

Question 4

When would it be considered normal for engine oil pressure to exceed limits and/or the engine oil filter bypass caution to illuminate?

Answer 4

During extreem cold wx

• Oil press may exceed limit
• Oil filter bypass may come on (go out @ 38ºC)

Question 5

Given these departure conditions what is the Maximum Allowable Gross Weight OGE/IGE and explain how it is calculated? 


• Temp
 35 degrees
• PA
 2000’
• Max TRQ Avail (DE) 108%

Answer 5

Use hover chart (P-65) in CL.

• Max GW OGE is 21200lbs
• Max GW IGE is 22000lbs

Question 6

Based on the conditions and results of question #5, what is the GO/NO GO OGE and IGE and explain how it is calculated?

Answer 6

Use 7A-16

• GO/NO GO OGE 103%
• GO/NO GO IGE 92%

Question 7

Explain the crew coordination quality “Be Explicit”. Which crew coordination principle does it support?

Answer 7

Be explicit:

• Crewmembers should use clear, concise terms, standard terminology, and phrases that accurately convey critical information.
• Avoid using terms that have multiple meanings, such as “right,” “back up,” or “I have it.”
• Avoid using indefinite modifiers such as, “Do you see that tree?” or “You are coming in a little fast.”

Principle:

• Communicate timely and effectively