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Shoulder Harnesses

 

July 2002

 

This month's ShopTalk will jump back into the nuts and bolts of your Mooney aircraft. Specifically we will take an in depth look at seat belts. Aircraft seat belts over the years have progressed a lot. The old TSO. (technical standard order) C22 (currently C22G) to the latest T.S.O. C114. TSO. C22G are a lap belt with a 1500 pound breaking strength with no upper torso belt. These belts were the typical installation up until 1979. Then in 1979 someone at Mooney got smart about safety and the factory started installing upper torso restraints at each seat.

 

Years ago the N.T.S.B. did a study of aircraft crashes with fatalities and determined that lives could be saved by the installation of a shoulder harness for each front seat occupant. The N.T.S.B. also identified equipment installed in the aircraft that can cause death when the shoulder harness is not available or utilized. Some of the items identified by the N.T.S.B. are post lights and control wheels. The FAA created FAR 23.785 to establish the criteria for a shoulder harness to meet.

 

When Mooney first started installing three point restraint systems in their aircraft they chose Davis and Indiana Mills restraints. The Davis restraints have a bad habit of coming lose in flight. Its not uncommon when seated in either front seat to tighten the shoulder harness only to find the lap belt is now above your belly button. Not only is this annoying but its dangerous. How far do you think your body will continue to travel foreword in a forced landing situation with a worn restraint system holding you in place?

 

Finally in 1989 Mooney got smart and installed AmSafe restraints in all current production aircraft. These new restraints meet TSO C114 and have a rating of 3,000 pounds. Mooney did recognize that they built a whole bunch of aircraft without shoulder harness. Back in 1984 Mooney offered for sale a shoulder harness kit to retro fit the pre 1979 aircraft. Production drawing #940044 was created so their kit can be installed in the front seats. Unfortunately Mooney did not address the back seats.

 

The current standards for aircraft restraints can be found in a number of different documents such as SAE AS8043, SFI spec 16.1 TSO’s C22G and C114. AmSafe also produces a component maintenance manual based on the above documents and some very interesting Dupont test data on how exposure to the elements cause restraint systems to deteriorate over time. Take a look at the Dupont graph that accompanies this article and think about your airplane and where it fits in on this graph. With the aging general aviation fleet it is not uncommon to find 25 or 30-year-old restraints installed.

 

There are some very big differences in how Mooney attached seat belts in the early aircraft. The M20B installed the belts on the floor. This caused the buckle of the lap belt to not be in the proper position to add a shoulder harness to when the seat was moved to the extreme forward or aft position. The Johnson bar can also interfere with the buckle under these conditions. I am currently working with AmSafe to develop an adjustable buckle for these aircraft. The C, E; F, G and J airplanes came with lap belts installed on their seats. This solved most of the problems. The long body aircraft (F, G and J) can be retrofitted with TSO C114 restraints in the front and back seats but the short body aircraft don’t have a good spot to locate the rear seat shoulder harness to that meets the requirements of FAR 23.785.

 

No one wants to think about when they may have to make a forced landing but I believe that a little preventive maintenance and some common sense will make your chances of surviving aviation a lot better. By adding shoulder harnesses to the front seats of your aircraft (TSO C114 type) you can have the same safety as the restraints installed in cars (3000 LBS). Now you know why I started working with AmSafe two years ago to develop seat belt kits for the Mooney fleet and why I am now working on developing kits for the Cessna fleet.

 

As always, if you have a question about this article, you may contact me at my aircraft repair shop, 307-789-6866 or via e-mail. Until the next ShopTalk, enjoy flying your Mooney.

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