Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
SW-09-44
July 28, 2009
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) informs you,
owners or operators, of an airworthiness concern regarding possibility
of separation of the cabin door while in flight for the following
Schweizer Models: 269A, TH-55A, 269A-1, 269B, 269C, serial numbers 001
through 1917, 269C-1, serial numbers 0001 through 347, and 269D, serial
numbers 0001 through 0073.
Background
There are two door hinges for each cabin door on Schweizer models 269
series aircraft. Each door hinge consists of the hinge pin assembly
which is attached to the airframe and the door hinge plate which
contains top and bottom hinge pin receptacles installed on the door.
The hinge pin assembly has two door hinge pins with a spring located in
between. The two hinge pin receptacles are openedend cylinders. When
the door is installed on aircraft, the spring-loaded door hinge pins
engage the top and bottom hinge pin receptacles respectively. Serrated
hinge pins (Schweizer Pilot’s Flight Manual refers these pins as hinge
pin tabs) are installed on each door hinge pin to provide travel stops
to the door hinge pins inside the hinge pin receptacles, and they are
also used to retract the door hinge pins out of the hinge pin
receptacles for door removal. The serrated hinge pins are secured in
position by an interference press fit. Loss of the serrated hinge pin
will result in lost of retention of the door hinge pin inside the hinge
pin receptacle. When both serrated hinge pins inadvertently come off
from the door hinge pins, the stop is lost and the spring will push the
lower door hinge pin through the hinge pin assembly and falls out of
the open end of the bottom hinge pin receptacle. With the lower door
hinge pin missing at the bottom hinge pin receptacle, the upper door
hinge pin inside the top hinge pin receptacle will drop down, and the
vibrations of the aircraft will cause the upper door hinge pin to fall
out of the bottom hinge pin receptacle. The door hinge plate will
separate from the hinge pin assembly which could result in separation
of the door from the aircraft.
Since 2005, there have been several occurrences of the cabin door
detaching from aircraft due to the serrated hinge pins coming off from
the door hinge pins, allowing the door hinge pins to separate from the
hinge pin receptacles on the cabin door. In December 2007, a cabin door
was reported separated from an aircraft in flight as a result of
separation of the serrated hinge pins from the door hinge pins.
Schweizer decided a "fail safe" device was needed to preclude any
future door losses, and the production hinges are now manufactured with
caps to replace the open ends of the hinge pin receptacles. For those
aircraft in the field, Schweizer issues service bulletins to provide an
alternate method to retain the door hinge pins within the hinge pin
receptacles for all affected aircraft. These service bulletins provide
instructions to weld a stainless steel rod on the open ends of the
hinge pin receptacles (Figure 1) to prevent the door hinge pins from
falling out of the hinge pin receptacles when the serrated hinge pins
are lost.
The door hinge is the original design that has been in continuous
production since the type certificate was issued. Therefore, the door
hinges installed in all Schweizer models 269 series helicopters
manufactured to this date are affected.
There has been no reported incident since December 2007. At this time,
this airworthiness concern is not an unsafe condition that would
warrant AD action under Title 14 of the Code of Federal Aviation
Regulations (14 CFR) part 39.
Recommendations
We recommend all owners and operators comply with actions outlined in
Schweizer Service Bulletins DB-026, C1B-028 and B-292 (as appropriate).
It is recommended to conduct a visual check of the cabin door hinge
installation before each flight until implementation of the appropriate
service bulletin at the next available maintenance opportunity. The
service bulletin action is not required when the new production hinge
is installed.
For Further Information Contact
Leung Lee, Aerospace Engineer, FAA NYACO, ANE-171, 1600 Stewart Avenue,
Suite 410, Westbury, NY 11590; phone: (516) 228-7309; fax: (516)
794-5531; email: leung.lee@faa.gov.
For Related Service Information Contact
Customer Support
Attention: Curt Northrop
Phone: (607)739-3821 ex 4519
Email: Northrop.curt.sacusa.com
