7x7 verses 7x19 SS cable

[Thruster87]

What difference would it make if 7x7 was used instead of 7x19 3/32 ss cable thru two 90 deg bends [rest straight] on controls.Other then the obvious 7x19 is more flexible but the 7x7 wears better.:;)5: Cheers

 

 

[Yenn]

S.S. cable is subject to fatigue cracking and the use of a stiffer cable will make cracking and breaking more prevalent. Not good for anything that moves.

 

 

[Thruster87]

Found this info:

 

In the below statement you wrote that every commercial aircraft flying is equipped with nothing but SS cables and fittings. This statement is only partly true. Yes, the fittings are made from Stainless Steel Type 303SE but most of the cables are Zinc or Zinc & Tin Plated Carbon Steel.

 

My name is Michael Wallace and I am Vice President of Sales for Loos & Co., Inc. and we are the OEM supplier to just about every commercial aircraft manufacturer in the Western Hemisphere. I'm here at home this morning browsing the internet and stumbled across your statement in the Beech Owners chat room. I realize your statement was from way back in May '03 but I thought I might set the record straight for you.

 

Our customer list includes Boeing, Douglass, deHaviland, Cessna, Beech, Piper, Gulfstream, Lockheed, Embraer and many other smaller manufacturers. The only ones that use strictly Stainless Steel cables are Gulfstream and Cessna.

 

The others use 1/8" 7x19 Carbon Steel cables in their primary flight controls. Carbon steel cables provide much greater fatigue life compared to stainless cables. Boeing uses practically no stainless steel cables. They use the Tin over Zinc variety of carbon steel cable in their primary flight control cables.

 

As far as Aircraft Spruce is concerned, as KenV35A writes below, They pass off foreign manufactured cables as being made to the military specification MIL-W-83420. If you look at the fine print in their catalog, they state that their cables are not QPL certifiable. QPL means "Qualified Products List". It is the list of qualified manufacturers to MIL-W-83420 (The latest revision is titled MIL DTL 83420) that the U.S. Military maintains. There are only 5 companies in the whole world that are on the QPL list and they are all U.S. companies. I'll list them here for you:

 

Continental Cable - Hinsdale, NH

 

Loos & Co. - Pomfret, CT

 

Strandcore - Milton, FL

 

Strandflex - Oriskany, NY

 

Wire Rope Corp. - St. Joseph, MO

 

What Aircraft Spruce pawns off as being "just as good as" to the flying public is in no way representative of true Military Specification wire rope. When Spruces' cables are tested to the criteria in the Mil Spec, they fail miserably. Their intentional mis-representation should be stopped but the FAA has bigger fish to fry. They turn a blind eye to the Sport and Home-Built aviation industry.

 

"You get what you pay for," Wallace said, "and non-QPL certified cable is always less expensive. In most cases, it is not lubricated and the performance tests have not been performed. Lubrication greatly extends the wear properties of aircraft cable, and all QPL-certified cable is lubricated." Loos & Co. has tested a number of lots of unlubricated non-QPL cable and found significant reductions in the cable's fatigue life. "These products may pass initial breaking strength tests," he said, "but rarely pass the criteria of retaining 50 to 60 percent of breaking strength beyond 30,000 endurance cycles." As a result, the non-QPL cable can fail in a much shorter lifetime.

 

AC43.13-1B, chpt.7, section 8, lists two types of corrosion-resistant steel for flexible cable use on civil aircraft. Type I, composition B cables, MIL-W-83420 and MIL-C-18375. Goes on to say "is equal

 

in corrosion resistant and superior in non-magnetic and coefficient of thermal expansion properties. Aircraft Spruce lists MIL-W-83420 as stainless. KenV35A

 

 

[Thruster87]

From testing done back in 1967

 

Abstract : Because of the recent high rejection rates on carbon steel control cables on military aircraft, the Air Force conducted breaking strength and endurance tests on various types of aircraft control cables. Since approximately 90% of the service life of jet aircraft is flown at low temperatures, the primary purpose of the tests was to obtain information on cable fatigue life at low temperature. The tests were conducted on 1/8-inch diameter 7x19 galvanized carbon steel, tin-coated carbon steel, and stainless steel cables at both low temperature (-65 F) and room temperature (+70 F). The tests were conducted in the Climatic Laboratory at Eglin AFB, Florida. Results indicate that the stainless steel cables are far superior to the galvanized or tin-coated cables for low temperature operation. Therefore, the stainless steel cables should be considered for replacement of the carbon steel control cables on military aircraft, and the appropriate specifications should be updated accordingly. [hope the cabin heater is up to par]

 

 

 

 

 

 

 

 

[Thruster87]

Anyone know a OZ outfit that carries 3/32" ss QPL cable in 100ft rolls or less [Aviall orders theirs from the USA and it takes about 12-15 days min 100ft roll] Cheers