BC-12 AD 78-20-11 Aileron Sprocket pins

[Mark Hazelden]

I was going through the ADs on the BC-12 that we are working on and have some questions on AD 78-20-11.

Our serial number does not fall under the AD but, sometimes parts from affected aircraft are put into other aircraft.

What I found were aileron sprocket stop pins that don't look like either drawing in Service Bulletin 78-002. Our stop pins extend aft about 1/8 inch and a button or universal shaped head on the forward side. The button head on the forward side is smaller than the pin on the aft side. It looks like a rivet peened into a pin. The stop pins are not the AN 393-9 clevis pins mentioned in the AD.

Questions:

1) Is the AN-393-9 Clevis pin supposed to be on all serial numbers or was it a fix for only the serial numbers listed on the AD?

2) Our pins don't extend aft 1/4" as stated in the AD. Again, are all stop pins suppose to extend 1/4" or only the sprocket that were fixed.

3) If this sprocket is not legal, where can the correct sprocket be purchased? Univair said they don't stock them and an internet search didn't turn up any.

I can upload a picture early this week if it would help.

I don't want to sign off this AD as "N/A by Serial number" with out doing my home work.

Thanks,

Mark Hazelden A&P
Bipe, Inc
Andrews, NC

[Pearson]

Re: BC-12 AD 78-20-11 Aileron Sprocket pins

I have two 1946 BC12Ds. They both have exactly the same two pins in the sprockets to comply with this AD. None of the pins extend to what I would call "approximately 1/4 inch" as stated in the AD. However on both aircraft the head of the pins make good solid contact with the stop on the top of the H column, preventing the yoke from turning any further.

I went to Aircraft Spruce's website to see what a AN393-9 clevis pin looked like. The pins on my sprockets have much larger heads that make better contact than the puny little heads on the clevis pins shown on their website.

I measured the distance the pins protrude from the sprockets. They are 0.135". The heads are about 1/4" in diameter on the side of the sprocket toward the rear of the aircraft. This causes me to wonder if the 1/4" measurement mentioned in the AD should have been referencing the diameter instead of the protrusion length.

On the front side of the sprocket you can see that the pins appear to be about 3/16" in diameter. They protrude only enough so that staking them secures them in the hole in the sprocket.

Compared to the heads of the AN393-9 clevis pins shown on the AC Spruce website, the heads of the pins on my aircraft are more squared off in relation to the edges around the circumference of the head. The ones AC Spruce shows look rounded off, and would not make good contact with the stops on the H column.

I hope this helps.

[Forrest Barber]

Re: BC-12 AD 78-20-11 Aileron Sprocket pins

Lets see what we can do. If the AN393-9 in the first paragraph is there you are good to go ; the 1/4 is approx. . Just check the purpose, they should stop the aileron movement. IF they are the 3/16 pins ( no head) ; do like its says and inspect . NOW FOR the Reason back in Alliance with Mrs. Feris , she sent a F-19 to a Float manufacturer in Florida ; during their testing on lake Jesse , their Test Pilot was doing roll testing and timing the roll rate ; he banged the ailerons past the stop and could not get it back. ( Interesting situation)
WE inspected the sprockets in stock and found that a batch had been made with the 3/16 rod and they were "too soft" . the factory SL explains the ser#'s affected: check your ser# ; to my knowledge ALL bad pins were located and changed way back in 1978. HOWEVER , out in the field MANY strange things happen . Just inspect for proper operation. IF the stops were banged in the wind and went too far around then you ahve a problem ; I will check my sprocket collection..... I have raw sprockets without stop pins ; more soon. Interesting discussion for the Fly-In at Alliance this year.


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78-20-11

TAYLORCRAFT

Amendment: 39-3314

Applicability:

Applies to Model BC-12D, Serial Nos. 6923, 8376, 8444, 8570, and 10538, and Model F-19, Serial Nos. F-080 through F-105, F-107 through F-112 and F-115 through F-126 certificated in all categories.To prevent malfunction of the aileron controls, accomplish the following:

(a)Inspect the two aileron stop pins (Taylorcraft P/N A-235) of the aileron control assembly (Taylorcraft P/N A-A231) prior to next 10 hours time in service after the effective date of this AD or by December 1, 1978, whichever occurs first.


The proper pins (2) are identified by the flat head of the pins against front face of the sprocket. The flat head is cut partially to clear chain and obtain smooth operation of control. The shank of the stop protrudes approximately 1/4". If the sprocket has AN393-9 clevis pins, no further action is necessary.

(b)If the pins are made from 3/16" diameter rod (no head), inspect for the following:

(1)Bent pins

(2)Loose pins

(3)Inadequate protrusion (less than 1/4") of pin through aft of sprocket or improper functioning.

(c)If any of the conditions identified in (b) above are present, replace the sprocket prior to further flight.

(d)If the AN393-9 clevis pin is not installed and none of the three conditions in (b) are found, replace the sprocket within 50 flight hours or by May 1, 1979 with a sprocket in which clevis pins (AN393-9) have been installed. Until the sprocket is replaced, reinspect within 10 hours time in service from last inspection. A proper sprocket may be obtained from Taylorcraft Aviation Corporation, 14600 Commerce N.E., P.O. Box 243, Alliance, Ohio 44601.

[Mark Hazelden]

Re: BC-12 AD 78-20-11 Aileron Sprocket pins

Thank you for your replies Richard and Forrest.

Mark