Cooling the Windshield Temp Sensor
Summertime is here and in full force, especially down here in Texas. But we still have to perform anti-ice system inspections such as of the “Inspection of Windshield Heat Cycling Contactor (WCC) I.A.W. 30-40-00 para. 1.B.”, which is accomplished at every “A” Inspection. In order to perform the check, you will have to cool the temp sensor within the windshield if the outside air temperature is 100°F or greater. The Maintenance Manual calls out to pour water over the temp sensor to lower the temperature. I use a plastic bag with ice in it and simply stick it under the windshield wiper blade over the temp sensor (this is considerably less messy). By all means, DO NOT spray the glass windshield with any type of freeze spray. There is a caution in the Maintenance Manual in the following paragraph (1.C.) “DO NOT SUBJECT WINDSHIELD TO THERMAL SHOCK OF SUDDEN TEMPERATURE CHANGES…MAY RESULT IN A FAILURE OF WINDSHIELD GLASS THROUGH THERMAL STRESS.” I have seen the “freeze spray” results on another type of aircraft, and I can attest to you that it wasn’t pretty. You also must consider the possibility that the outer windshield on the Westwind might not have been shimmed properly at the last install, resulting in it being slightly stressed already. It may not take much more to break it.
Friday, June 30, 2006
ATA 27
Nitrogen Bottle Service Life
The nitrogen storage bottles have a 24-year service life starting at the date of manufacture, NOT the date when it was placed in service as Israel Aircraft Industries (IAI) thinks and Chapter 5 states. Pacific-Scientific, who makes the bottles, issued a letter stating the life limit begins at date of manufacture. If you need a copy, let us know. The same criterion applies to any pressurized container carried on or in an aircraft such as portable fire bottles, oxygen bottles, etc. Next time the bottles are removed, enter the date of manufacture in the logbook.
The nitrogen storage bottles have a 24-year service life starting at the date of manufacture, NOT the date when it was placed in service as Israel Aircraft Industries (IAI) thinks and Chapter 5 states. Pacific-Scientific, who makes the bottles, issued a letter stating the life limit begins at date of manufacture. If you need a copy, let us know. The same criterion applies to any pressurized container carried on or in an aircraft such as portable fire bottles, oxygen bottles, etc. Next time the bottles are removed, enter the date of manufacture in the logbook.
ATA 05
Onboard RVSM Documentation
This is just a reminder to all crewmembers and maintenance shops to make sure that the RVSM ops manual, FAA Letter of Authorization, and the Minimum Equipment List (MEL) are aboard the aircraft at all times. These are required as part of the RVSM approval.
ATA 27
Rear Horizontal Splice
We continue to get phone calls concerning the rear horizontal spar splice radial and axial play. Everybody wants to just jump in and replace the bushings and bearings. In fact, this is a major undertaking, requiring precise measurements and controls. Most, if not all, of these “excessive“ clearance problems can be brought under control by reading and applying Service Bulletin (SB) 1124-55-021 Paragraph E. sub. Paragraph 1.9 thru 1.12. It is a simple procedure that has excellent results. We have found that when the aircraft is re-assembled following splice replacement, the radial and axial measurements are already at or very near the limits called out in the Maintenance Manual, even with the splice having new bushings. It’s frustrating to the shop that after all that work, the tail is still “loose”. Using the above SB procedure will, in most cases, fix the problem. At the same time, take a look at the forward scissors, which have replaceable bushings. Keep them tight with shimming when needed.
We continue to get phone calls concerning the rear horizontal spar splice radial and axial play. Everybody wants to just jump in and replace the bushings and bearings. In fact, this is a major undertaking, requiring precise measurements and controls. Most, if not all, of these “excessive“ clearance problems can be brought under control by reading and applying Service Bulletin (SB) 1124-55-021 Paragraph E. sub. Paragraph 1.9 thru 1.12. It is a simple procedure that has excellent results. We have found that when the aircraft is re-assembled following splice replacement, the radial and axial measurements are already at or very near the limits called out in the Maintenance Manual, even with the splice having new bushings. It’s frustrating to the shop that after all that work, the tail is still “loose”. Using the above SB procedure will, in most cases, fix the problem. At the same time, take a look at the forward scissors, which have replaceable bushings. Keep them tight with shimming when needed.
ATA 05/24
Emergency Battery Maintenance
The Emergency Gyro and Emergency Lighting Batteries are an important part of your Westwind’s operating systems. Chapter 5-25-00 of the 1124/1124A Westwind Maintenance Manual requires the batteries to be checked every 200 hours or 3 months. Many people consider this requirement to be a nuisance. Quite often we find the batteries have been run down or their inspection interval was ignored. Do not let this happen to you. Take the time to check your batteries. Try putting them in sync with your “A” Inspection, if possible. If you are tracking them by calendar time, be sure to give yourself enough turn time, as they require 16 hours to charge. Considering their importance in the event you should need them, you will be glad you took the time to ensure their airworthiness.
The Emergency Gyro and Emergency Lighting Batteries are an important part of your Westwind’s operating systems. Chapter 5-25-00 of the 1124/1124A Westwind Maintenance Manual requires the batteries to be checked every 200 hours or 3 months. Many people consider this requirement to be a nuisance. Quite often we find the batteries have been run down or their inspection interval was ignored. Do not let this happen to you. Take the time to check your batteries. Try putting them in sync with your “A” Inspection, if possible. If you are tracking them by calendar time, be sure to give yourself enough turn time, as they require 16 hours to charge. Considering their importance in the event you should need them, you will be glad you took the time to ensure their airworthiness.
ATA 32
Brake Fuse
A fuse is installed between the forward and rear brake line at the main gear. Why is the fuse in the system? If this fuse were installed backwards, what would be the effect on the normal braking system? On the emergency braking system? Answer: The fuse is in the system to prevent the loss of braking should a rear brake line fracture. If a forward line were to fail, the emergency brake system would still function through the brake shuttle valve. If the aft line were to fail, the fuse would stop the flow of fluid overboard and allow the forward brake housing to continue to work. If the fuse were to be installed backwards, the system would work normally unless you had a rear line failure. If the rear line broke, all braking fluid to that gear would be lost overboard.
A fuse is installed between the forward and rear brake line at the main gear. Why is the fuse in the system? If this fuse were installed backwards, what would be the effect on the normal braking system? On the emergency braking system? Answer: The fuse is in the system to prevent the loss of braking should a rear brake line fracture. If a forward line were to fail, the emergency brake system would still function through the brake shuttle valve. If the aft line were to fail, the fuse would stop the flow of fluid overboard and allow the forward brake housing to continue to work. If the fuse were to be installed backwards, the system would work normally unless you had a rear line failure. If the rear line broke, all braking fluid to that gear would be lost overboard.
ATA 21
In Flight Pressurization Issues:
An operator reported the cabin altitude would climb when the power lever was reduced during routine descents. The aircraft power lever was set to a higher setting and pressurization control was regained, followed by an uneventful landing. Note: The cabin pressure 10,000-foot red warning light did not illuminate.
During the troubleshooting process, it was noted that the left Bleed Switching Valve (BSV) was inoperative and the right High Pressure (HP) side of the right BSV was inoperative. The operator was concerned that they experienced a simultaneous failure of both valves in flight. Past experience has shown that the aircraft most likely did not have a simultaneous failure, but rather the left BSV valve had previously failed and the right BSV valve was the valve that experienced the most recent failure. The ground bypass valve is installed in the right engine bleed system, and due to the increased air flow, it is the most common selection used on the ground. Airplane Flight Manual Section IV, Normal Procedures, Before Take-Off checklist says to set the cabin air selector to both engines; however, it does not require the left bleed source be operationally checked. The aircraft will operate normally on one engine bleed source. If the left and right bleed sources are not both periodically checked, it can lead to pressurization issues in flight. It is recommended that the left bleed source be checked before takeoff to help prevent in-flight pressurization issues. It should also be noted that this condition has been seen only on the Westwind and Astra/Astra SP aircraft.
An operator reported the cabin altitude would climb when the power lever was reduced during routine descents. The aircraft power lever was set to a higher setting and pressurization control was regained, followed by an uneventful landing. Note: The cabin pressure 10,000-foot red warning light did not illuminate.
During the troubleshooting process, it was noted that the left Bleed Switching Valve (BSV) was inoperative and the right High Pressure (HP) side of the right BSV was inoperative. The operator was concerned that they experienced a simultaneous failure of both valves in flight. Past experience has shown that the aircraft most likely did not have a simultaneous failure, but rather the left BSV valve had previously failed and the right BSV valve was the valve that experienced the most recent failure. The ground bypass valve is installed in the right engine bleed system, and due to the increased air flow, it is the most common selection used on the ground. Airplane Flight Manual Section IV, Normal Procedures, Before Take-Off checklist says to set the cabin air selector to both engines; however, it does not require the left bleed source be operationally checked. The aircraft will operate normally on one engine bleed source. If the left and right bleed sources are not both periodically checked, it can lead to pressurization issues in flight. It is recommended that the left bleed source be checked before takeoff to help prevent in-flight pressurization issues. It should also be noted that this condition has been seen only on the Westwind and Astra/Astra SP aircraft.
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