The Beechcraft 1900D is a popular turboprop aircraft. With more than 380 aircraft in service, many mechanics are working on these venerable aircraft. On Sept. 20, 2004, Pratt & Whitney Canada (P&WC) issued Service Bulletin 14003R10. This service bulletin affects the PT6A-67D and -67R engines. I talked to Kris Charlesworth of Raytheon Airline Aviation Services, who worked with P&WC in developing this latest revision to the service bulletin, to gain a little more insight into how it works. In this article, we will look at some of the key points of the revision, and how it affects operators of 1900s.
The crux of SB 14003R10 deals with recommended basic operating time between overhaul (TBO) and hot section inspection (HSI) frequency. The pre-established frequencies of periodic inspections issued by P&WC help ensure engine serviceability. The TBO and HSI intervals are the two major scheduled periodic inspections for these engines and are discussed in SB 14003R10. In addition, the SB provides TBO extension and progressive maintenance procedures for operators with an average utilization higher than 500 hours per year.
SB 14003R10 has three major categories of TBO -- basic, fleet, and engine.
Basic TBO. The basic industry TBO is P&WC's recommended TBO per the service bulletin and is applicable to all operators.
Fleet TBO extension. This is a TBO extension granted by P&WC for an operator with a fleet of similarly operated and maintained engines. P&WC uses the condition of the engines when they are examined at overhaul as the primary means of validating that the operator is operating and maintaining the engines in a manner that warrants extending the TBO interval for a specific fleet.
Engine TBO extension. This TBO extension is applicable to a specific engine. TBO extension under this case is granted for a specific engine and is granted on an engine-by-engine basis (vs. the fleet TBO above).
Under this SB, all TBO extensions go through P&WC for approval. Extension recommendations from P&WC are based on both the operator's procedures and experience, and on the experience of P&WC. P&WC's experience takes the following factors into consideration.
- Engines are built only with new P&WC recommended components, components refurbished by P&WC owned shops, or components refurbished by P&WC recommended shops per P&WC procedures.
- The engines are P&WC factory built engines or engines overhauled/repaired at a P&WC service center or a P&WC Distributor and Designated Overhaul Facility (DDOF).
An important thing to note is that once TBO extension is recommended by P&WC under the SB, the engine maintains its TBO extension recommendation as long as it is operated within the limitations established in the operating manuals and maintained in accordance with the maintenance manual and the terms of SB 14003R10.
Prior to this new SB revision, operators had to go through a lot to get a TBO extension on their engine. They had to go through the local Pratt representative, and it was considered a cumbersome process.
Variables affecting TBO extension
There are several variables that are considered when reviewing whether or not the TBO should be extended. These include:
- Average flight duration
- Percentage of time at any given power level
- Climatic conditions and environment
- Maintenance practices
- Engine modification standards
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