46-01-01 CESSNA: (Was Service Note 1 of AD-722-5.) Applies to all T-50 Aircraft.
Improper flap chain operation, characterized by jumpy chain action, may lead to the chain jumping the idler and jamming. Improper operation is probably due to incorrect chain tension or excessively worn sprockets or both. The chain tension can be checked at the flap screw inspection opening by pressing the chains together at a point approximately 4 inches inboard of the flap screw sprocket. The distance between the chains should not be less than 1/4 nor more than 3/4 inch. The chain tension may be adjusted by means of the adjustable arm or the idler. The sprockets are considered excessively worn and should be replaced when the teeth are 1/2 the thickness of the sprocket web. In addition, the chain guard on the idler should be checked to make certain that it has not been bent or worn through. Inspect all chain links for cracks and replace any links that are found cracked. It is recommendedthat the chain be replaced every 1,000 hours.
(Cessna Service Bulletin No. 100 dated July 13, 1945, covers this same subject.)