Beech has a unique identification system for the flexible air ducts used inside the cabin, for both heat and ventilation. Is there any way to decode what the part number stands for?
Search strings (CAT, CEET, SCAT, SCEET, air hose)
What follows are the decoding keys for the cabin ventilation air ducts used in the Beech light aircraft. I am still working on the data for the other ducts.
Sample part number is 111728-6E6-40
111728 is the prefix for ventilation ducting, 250 degrees and cooler.
-6 means that the duct has a 6/8 (3/4″) molded cuff on the leading end, as measured in eighths of an inch.
-6F means that the duct is size ‘F’, or 2.5″ inside diameter’, where:
A = 1.00″ ID
B = 1.25″ ID
C = 1.50″ ID
D = 2.00″ ID
E = 2.50″ ID
F = 3.00″ ID
G = 3.50″ ID
H = 4.00″ ID
J = 0.625″ ID (5/8″ radio stack cooling duct)
-6F6 means that the duct has a 6/8 (3/4″) molded cuff on the trailing end, as measured in eighths of an inch.
-6F6-40 means that the duct is 40 half-inches, or twenty inches long, end-to-end (including the cuffs).
The cabin heated air duct part numbers for the late-model C23 and C24 airframes are shown below. These numbers apply to airframes MB716, plus MB731 and up; M1586, M1600 and up; MC293, MC305 and up; essentially 1975 and later planes. If possible, try to buy ducts having preformed collars on the attachment ends, as they will connect more ‘cleanly’, will have less leakage, and will be much more durable during installation and in service. Note that full lengths as sold by Aircraft Spruce will have collars on the finished ends. If the 1.25” duct is purchased in a complete 144” length, the added ten inches will not pose an interference problem when installed.
111728-8C8-264 This is the long duct to the rear seat lower spar cover heating outlets (two ducts required); 1.5″ ID by 132″ long. You will have extreme difficulty getting the old duct out of the forward cabin area, and even more difficulty trying to get new 1.5” duct installed. I strongly recommend that you use 1.25” SCEET (red silicone) duct instead, for this particular application. It will go in far easier, and won’t cause as many interference and corrosion problems due to an overly-cramped installation. The smoother inner liner will flow as much or more air as the 1.5” CEET duct. You can use short lengths of the 1.5” duct to connect to fittings. The 1.25” duct is a fairly snug fit inside the 1.5” duct, and can also be sealed with red RTV compound. The SCEET will never absorb moisture, regardless of age.
111728-8C8-14 This is the very short 1.5” ID by 7” long duct which connects the firewall outlet to the right-side splitting Tee.
111728-8B8-10 This is the very short 1.25” ID by 5” long duct which connects the splitting Tee to the inline Wye feeding the two center-pedestal outlets.
111728-8B8-19 This is the short 1.25” ID by 9.5” long duct which connects the inline Wye to the RH center-pedestal outlet.
111728-8B8-46 This is the moderate-length 1.25” ID by 23” long duct which connects the inline Wye to the LH center-pedestal outlet.