Hydraulic Line Integrity
We have learned that there have been events where hydraulic lines are cracking. On a recent incident, the left main hydraulic annunciator came on about 30 minutes after takeoff, followed by the right hydraulic annunciator. The crew returned to home base, blew the landing gear down, and landing uneventfully. It was found that the pressure line into the lift dump valve was cracked near a B-nut. The hydraulic pumps ran dry for an indeterminate time. As you go about your routine area inspections, please pay attention for hydraulic fluid staining and fluidleaks. As the fleet continues to mature, we want to ensure we are aware of areas that may become fleet symptoms. Advisory Circular 43-4A identifies problem areas for corrosion, and one of them is around B-nuts and line marking tapes. Corrosion will weaken the line sufficiently to cause failure. If you have recently experienced a similar situation, please let us know via e-mail to westwind@worthingtonav.com
Monday, June 29, 2009
Friday, June 12, 2009
ATA 21
1124 Air Cycle Machine Failure Prevention Maintenance
The 1124/1124A environmental system air cycle machine (ACM) is maintained in an "on condition" basis by regular oil changes. normal service life of an ACM can exceed 2000 flight hours when all cooling system components are functioning properly to protect the machine from overspeeds or icing conditions.
If an ACM failure does occur, the operator should perform the "Post Cooling Turbine Failure Inspection" detailed in the 1124 AMM 21-50-00. These procedures include a thorough visual inspection of the ram air ducts and check of the fluid pressure regulator valve.
Along with the components checked in the procedure noted above, a dirty heat exchanger can contribute or cause a shortened ACM life. The AMM also includes an approved "Heat Exchanger Inspection and Cleaning Procedure" in chapter 21-50-00. If your heat exchanger has never been cleaned, this procedure should be considered during a ACM replacement, or as a preventative ,maintenance step at the operator's option.
There are some older Service Information Letter and Service Bulletins that have been issued that detail various system upgrades and maintenance tips. A review if these documents and their application may help prevent a future ACM failure in your aircraft.
The 1124/1124A environmental system air cycle machine (ACM) is maintained in an "on condition" basis by regular oil changes. normal service life of an ACM can exceed 2000 flight hours when all cooling system components are functioning properly to protect the machine from overspeeds or icing conditions.
If an ACM failure does occur, the operator should perform the "Post Cooling Turbine Failure Inspection" detailed in the 1124 AMM 21-50-00. These procedures include a thorough visual inspection of the ram air ducts and check of the fluid pressure regulator valve.
Along with the components checked in the procedure noted above, a dirty heat exchanger can contribute or cause a shortened ACM life. The AMM also includes an approved "Heat Exchanger Inspection and Cleaning Procedure" in chapter 21-50-00. If your heat exchanger has never been cleaned, this procedure should be considered during a ACM replacement, or as a preventative ,maintenance step at the operator's option.
There are some older Service Information Letter and Service Bulletins that have been issued that detail various system upgrades and maintenance tips. A review if these documents and their application may help prevent a future ACM failure in your aircraft.
Wednesday, June 10, 2009
ATA 56
Windshield Resistance:
The following resistance should be applicable to a new or used windshield.
Between terminals 1 and 2: -0.720 to 0.974 ohms @ 75 Degrees F +/- 5 degrees.
Between terminals 4 and 5: -0.720 to 0.974 ohms @ 75 Degrees F +/- 5 degrees.
Between terminals 3 and 6: this reading will vary with teprature changes.
the following are three examples, you will have to calculate anything in between.
Between 110 degrees F = 342 ohms
85 degrees F = 328 ohms
50 degrees F = 310 ohms
The following resistance should be applicable to a new or used windshield.
Between terminals 1 and 2: -0.720 to 0.974 ohms @ 75 Degrees F +/- 5 degrees.
Between terminals 4 and 5: -0.720 to 0.974 ohms @ 75 Degrees F +/- 5 degrees.
Between terminals 3 and 6: this reading will vary with teprature changes.
the following are three examples, you will have to calculate anything in between.
Between 110 degrees F = 342 ohms
85 degrees F = 328 ohms
50 degrees F = 310 ohms
Tuesday, June 2, 2009
ATA 05
Upcoming Revisions / AMM
AMM 5-04-03 pages 209/210 will be revised in the next issue to correctly reflect the flow from AMM 5-40-03 page 2, items 3 & 4.
AMM 5-04-03 pages 209/210 will be revised in the next issue to correctly reflect the flow from AMM 5-40-03 page 2, items 3 & 4.
ATA 80
Starter Sequence
The left starter sequence is the same as the right only change No. 1 and No2. and right and left.
1. Power flows from the No. 2 distribution bus and start circuit breaker to the right start switch.
2. From the right start switch to the left start relay SR1. If the left start circuit is not in use the SR1 will be de-energized and these contacts of SR1 will be closed.
3. From SR1 to GLR2. With no system malfunction GLR2 will energize as soon as battery power is applied, and these contacts will also be closed.
4. From GLR2 to pins K and X of the right generator control unit.
5. the power that comes in pins K and X goes out pin G of the GCU assuming the engines is below 50% N2 and the stop position of the start switch has not been pressed.
6. From pin G of the right generator control unit, power goes to the right DC contactor box and does the following:
(A) Arms the ignition circuit. There is no ignition until the right power lever is moved out of stop cock.
(B) Energizes the Start Relay (SR2) and the Auxiliary Start Relay (ASR2)
7. The Start Relay (SR2) does the following:
(A) Latches in the right start circuit so the start switch can be released.
(B) Disables the right feeder fault circuit during the start.
(C) Energizes and closes the right start contactor (GSC2).
(D) Disables the left start circuit
8. The Auxiliary Start Relay (ASR2) does the following:
(A) Opens the left bus tie contactor.
(B)Opens the left feeder fault circuit during the start.
(C) Closes the left start contactor. This is used for the cross start and will only happen during the second engine start, if the operating generator switch is on and there is no external power connected to the airplane bus system.
9. At corrected 50% N2 the right engine computer will supply a ground to pin N of the right GCU. This will cause a relay in the GCU to energize which will open its contacts and stop the power from coming out of pin G. This will terminate the start.
10. Pushing the right start switch to the STOP position will also supply a ground to pin N of the GCU and terminate the start, at any RPM below approximately 50% N2.
NOTE:
The only thing the engine computer has to do with the engine start , other than the obvious safety features, is to stop the start and provide enrichment. Everything else to do with starting is strictly a function of the DC electrical system.
The left starter sequence is the same as the right only change No. 1 and No2. and right and left.
1. Power flows from the No. 2 distribution bus and start circuit breaker to the right start switch.
2. From the right start switch to the left start relay SR1. If the left start circuit is not in use the SR1 will be de-energized and these contacts of SR1 will be closed.
3. From SR1 to GLR2. With no system malfunction GLR2 will energize as soon as battery power is applied, and these contacts will also be closed.
4. From GLR2 to pins K and X of the right generator control unit.
5. the power that comes in pins K and X goes out pin G of the GCU assuming the engines is below 50% N2 and the stop position of the start switch has not been pressed.
6. From pin G of the right generator control unit, power goes to the right DC contactor box and does the following:
(A) Arms the ignition circuit. There is no ignition until the right power lever is moved out of stop cock.
(B) Energizes the Start Relay (SR2) and the Auxiliary Start Relay (ASR2)
7. The Start Relay (SR2) does the following:
(A) Latches in the right start circuit so the start switch can be released.
(B) Disables the right feeder fault circuit during the start.
(C) Energizes and closes the right start contactor (GSC2).
(D) Disables the left start circuit
8. The Auxiliary Start Relay (ASR2) does the following:
(A) Opens the left bus tie contactor.
(B)Opens the left feeder fault circuit during the start.
(C) Closes the left start contactor. This is used for the cross start and will only happen during the second engine start, if the operating generator switch is on and there is no external power connected to the airplane bus system.
9. At corrected 50% N2 the right engine computer will supply a ground to pin N of the right GCU. This will cause a relay in the GCU to energize which will open its contacts and stop the power from coming out of pin G. This will terminate the start.
10. Pushing the right start switch to the STOP position will also supply a ground to pin N of the GCU and terminate the start, at any RPM below approximately 50% N2.
NOTE:
The only thing the engine computer has to do with the engine start , other than the obvious safety features, is to stop the start and provide enrichment. Everything else to do with starting is strictly a function of the DC electrical system.
ATA 80
Starter Sequence Troubleshooting
1. Select voltmeter in cockpit to Generator position
2. Press and hold the ammeter/voltmeter and press the start button to read the start buss volts.
a) If you receive voltage on the meter this tells you if the starter is receiving voltage and the continuity is correct-(starter is getting power but not turning, brushes, bearings worn etc.)
b) If no voltage is present, than starter is probably OK. Starter is not getting power (RCR, SR-1 etc.)
3. Depress and hold the Start Button in.
4. Bring Throttle out of idle cut-off.
a) If ignition light comes on, then the power is good thru the GCU and SR, or the GSC may be bad.
b) If opposite buss-tie opens and buss goes dead then ASR pulled.
c) Release start button.If ignition light stays on when start switch is released, then the SR is good.
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