Citation Fall 2008
- Troubleshooting Oxygen System Leaks
- Mandatory Replacement of Controller-Inverters
- Are You Ready for WAAS?
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Troubleshooting Oxygen System Leaks
— Justin Merkling
An oxygen system leak can be a very bothersome squawk. It can potentially be costly to repair, depending on how long it takes to find. In order to give technicians a head start on finding the leak, operators can perform one very important step before traveling to a repair facility. First, service the oxygen system per the manufacture’s maintenance manual and let the bottle temperature stabilize. Next, unplug one of the crew oxygen masks and let it sit for approximately 24 hours. If after 24 hours, the oxygen level has not changed, the unplugged mask is the culprit. If the leak continues, plug the mask back in and repeat the process with the other mask. By doing this, the technician will not have to start with the masks and it will save value time and money. Better yet, if the leak is in one of the masks, no further troubleshooting will be required.
If there are any questions on this topic or any other issue, please contact me at 269.969.8422.
Mandatory Replacement of Controller-Inverters
— Ed Johnson
Cessna recently released Mandatory SL650-21- 11 and SL750-21-07, each dealing with replacement of specifically identified Airborne Controller-Inverters which could fail and cause damage to the Temperature Control System Indicator-Selector.
There is an Airborne Service Letter 73 (Model 650) or 74 (Model 750) attached to each of the Cessna SLs to identify which controller-inverters are to be replaced. The SL is somewhat confusing as to exactly which component is to be checked. Also, more importantly, you should know that there are two components on each aircraft that are to be checked. The vendor component to be checked is part number 1E48-1.
These units are installed under the aft cabin floor just forward of the aft pressure bulkhead on the Model 650 and in the aft LH and RH tailcone on the Model 750 aircraft. Again, there will be two controller-inverters per aircraft and both units must be checked to satisfy the requirements of the Service Letter.
Misunderstanding has occured when technicians confuse the part number of the Controller-Inverter (1E48-1) with that of the Indicator-Selector (1E45-(X)), which is a single unit and installed in the instrument panel. The Cessna part number for both the Controller- Inverter and the Indicator-Selector both begin with the base number 9914130-(X).
If you have any questions about these Service Letters, please contact me at 402.479.1555.
Are You Ready For WAAS?
— Ed Johnson
As a critical step in the FAA’s NextGen plans, WAAS GPS approval will open up nearly all U.S. airports for precision approaches. The latest addition to our Straight Talk series explores why WAAS is important to business aviation operations, explains equipment selection and installation and sheds light on the approval processes.
Visit www.DuncanAviation.aero/straighttalk to get the answers to your WAAS questions, subscribe to updates on the issue and join the conversation.
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