The key to achieving the best possible cruise performance and fuel efficiency in a Twin Commander while providing the most comfortable ride and environment for pilot and passengers is maintaining a properly pressurized cabin. It’s not an easy job in any aircraft, what with countless locations where pressurized cabin air potentially could leak into lower-pressure ambient air. The people at Twin Commander Aircraft, along with highly experienced technicians at authorized service centers, regularly discuss methods and materials to keep pressurization systems performing at their optimum level.
Over the years, various upgrades and fixes have made significant improvements in the fleet’s ability to maintain cabin pressure. Fixes may be as simple as a seal and as complex as a complete system overhaul. Following is a review of available solutions, as well as what is in the pipeline for the future.
Service Letter (SL) 384, applicable to Twin Commander models 685, 690/A/B/C/D and 695/A/B, contains replacement engine control cable seal nuts to prevent loss of pressurization through the cockpit ends of the engine control cables. Parts for SL 384 are available immediately.
Custom Kit (CK) 50, applicable to Twin Commander models 680, 680F and variants, 680T/V/W, 681, 685, 690/A/B/C, and 695, provides improved cockpit control column and rudder pedal boots. The replacement boots, which are manufactured using more durable material than original factory-installed rubber boots, and the associated mounting hardware last longer and do a better job preventing pressurized cabin air leaks. CK 50 is available immediately.
SL 382, applicable to Twin Commander models 680FP/FLP, 680T/V/W, 681, 685, 690/A/B/C, and 695, surveys areas where cabin air leaks could potentially occur in aircraft pressurized to the floor, and offers a variety of solutions for sealing potential leak areas.
SL 383, applicable to Twin Commander models 695A/B, concerns areas of potential cabin leaks, and solutions, for aircraft pressurized to the skin.
CK 184, applicable to the same Twin Commander models as SL 382 (above), is a replacement for the original molded rudder pedal plug, which can deteriorate over time.
CK 185, applicable to the same Twin Commander models as SL 383 (above) is a replacement for the original molded rudder pedal plus. Both CK 184 and CK 185 are available immediately.
SL 388, applicable to all pressurized Twin Commander models, reviews methods for effectively sealing skin laps on the exterior of the aircraft.
CK 183, applicable to Twin Commander models 690C/D and 695/A/B, provides a complete package to replace an existing Sundstrand Environmental Control System with an Enviro system.
Twin Commander Aircraft is actively working on additional pressurization-related projects including replacement ducts for the Sundstrand Environmental Control System, and a new wing root seal.
CK50 Boot Kit
Many of the ducts for the Sundstrand system are not currently available, so Twin Commander has commissioned design and testing to provide a complete array of Sundstrand system ducting. The project is expected to be completed later in 2016.
A new wing root seal would replace the original design, which used sealant-saturated cloth to seal the wing root area and maintain cabin pressure. However, the sealant and cloth are subject to deterioration over time, resulting in leakage. Twin Commander is designing a plug that would be inserted into the wing root, providing a permanent seal between ambient and cabin air.
For more information about available solutions for upgrading your cabin pressurization system, contact your authorized Twin Commander Service Center.
