Yeah but I thought you did it.

[Lu Zuckerman]

Back around 1955 or early 56 Sikorsky got a contract from Israel for several S-55s.  At that time the US could not provide military assistance to Israel so the helicopters were purchased on a commercial contract.  The helicopters underwent extensive inspection prior to first flight and during the test and checkout one of the helicopters accumulated about six hours where all of the crabs were to be worked out.  The test pilots and the mechanics couldn’t find anything wrong.  Since the helicopter did not have any electronics installed the technicians installed a pallet on the cargo deck containing several radios to allow the delivery flight to New Jersey.  The helicopter was sold officially in New Jersey to evade the Connecticut sales tax.  The S-55 was loaded aboard a freighter in an unprotected cargo hold.  Upon arrival in Israel the blades were installed and the helicopter taken for a check flight.  The pilot noted a severe vibration and a loud clunking noise.  They landed the helicopter to check the transmission hold down bolts and they were found to be installed correctly.  They went inside the helicopter and pulled the soundproofing material.  Attached to the forward right transmission mount was a small cotton sack containing several bolts, nuts and washers and a note telling the reader that I couldn’t get these in why don’t you try.  These bolts were supposed to secure the “fish plate” which ties the helicopter structure to the trannie hold down bolts.  The “fish plate was installed and attached to the structural element of the hold down bolt attachment but was not attached to the structure.  There was evidence that someone on the production line tried to align the boltholes with a screwdriver.  The structure, which was magnesium, was severely scratched and severely corroded due to the sea transport.

 

What had happened was that the transmission was installed on the helicopter out of position causing the structure to deflect.  The man that normally would install the bolts through the “fish plate” couldn’t get the holes to align.  He put the hardware in the bag and requested that the next workstation install them.  Obviously they ignored the request and Sikorsky had to provide a new helicopter and place the original in remanufacture.

 

The strange thing is that the Sikorsky test pilots did not note the vibration.