Abort net for jungle ops.

[avbug]

This failure was documented in a Canadian A&P document, but there are no references in Service Bulletins or ADs in the US.

Certainly not documented in this Australian article from 2003...

http://docs.google.com/gview?a=v&q=...+cessna+336+aileron+cable+failure&hl=en&gl=us

Spelled out by CASA bulletin AWB 27-3...

http://www.casa.gov.au/scripts/nc.dll?WCMS:STANDARD::pc=PC_90529

AWB 27-3 Issue 1, 28 February 2003

Cessna 336/337 Flap Cable Wear

Applicability

All Cessna 336/337 series aircraft.
Purpose

The purpose of this bulletin is to advise operators and maintenance organisations that excessive wear of the flap cable may exist in an area that is difficult to inspect during the periodic check of the cable in accordance with the maintenance manual. Excessive wear, corrosion or broken wires may result in failure of the flap cable, which can result in asymmetric flap deployment.
Background

This model aircraft has suffered a number of asymmetric flap extensions as the result of failed flap cables. The failure of the flap cable is caused by excessive wear at the inboard bellcrank, P/N 1462020-27. The wear location is at the tight radius bend on the bellcrank prior to the termination point of the cable. The cable wear is on the inside radius of the bend and is not noticeable without removal of the cable.
During one incident in the USA, the pilot lost control of the Cessna Model 336 on landing, but was able to recover control and successfully land the aircraft without sustaining damage or injuries. In a separate accident, again in the USA, the pilot of a Cessna Model 337 lost control of the aircraft on landing, after suspected asymmetric flap deployment caused by a failed flap cable.
In addition to the above two incidents, an incident occurred in Australia on 1 February 2003 where, on approach to land, the left flap completely retracted. Upon investigation it was found that the left flap operating cable P/N 1460100-7 had failed approx 1" from the left flap inboard bellcrank P/N 1462020-27. Further investigation revealed the right hand flap cable had broken internal strands. These were not visible until the cable was removed from the aircraft and carefully inspected. The cable has a severe bend by design at the inboard bellcrank location, which seems to exacerbate the wear and fatigue of the cable in this location.
The Model 336/337 Maintenance Manual requires a 100 hour inspection of the flap cable system. It is recommended that maintenance personnel treat the left and right hand inboard bellcranks (P/N 1462020-27) and all others in the flap system as "critical fatigue areas". A critical fatigue area is defined by FAA AC 43-13-1B as the working length of a cable where the cable runs over, under, or around a pulley, sleeve, or through a fair lead; or any section where the cable is flexed, rubbed, or worked in any manner. It also includes cable within 1 foot of a swaged fitting. As such, these areas require close visual inspection, which, in this case, can only be accomplished by complete removal of the flap cable so that hidden areas of the cable can be inspected for excessive wear.
In addition to the requirements of the Cessna 336/337 Maintenance Manual and the requirements of FAA AC 43-13-1B, operators maintaining the aircraft in accordance with CASA Schedule 5, must, according to Section 1 - The Airframe Part (2) (f);

"inspect the flight control system bellcranks, push pull rods, torque tubes, cables, fairleads, turnbarrels and pulleys".
​

A thorough inspection of the flap cable at the inboard bellcrank location will require complete removal of the cable in order to detect hidden damage.
Recommendations

1. Because of the criticality of the flap cables, and the difficulty of inspecting them in situ, the left and right flap cables should be removed and inspected for wear, broken wires and corrosion in accordance with FAA AC 43-13-1B, chapter 7, Section 8, paragraph 7-149(d) and the Maintenance Manual at the100 hourly or annual inspection, whichever first.
2. Reporting Action: If any excessive wear, corrosion or broken wires are detected, report it to CASA via a Major Defect Report (MDR) form (as required by CAR 52). In the MDR form, specify the exact location of the cable damage and include a sketch if possible showing the location of damage in relation to pulleys, bellcranks and other hardware. This additional information will allow CASA to assess the fleet-wide condition of the flap cable system and develop possible future action.

The CASA Airworthiness Bulletin cites two separate incidents in the USA. Imagine that. Unheard of in the US, you say? Really?

In 2003 the FAA issued an airworthiness concern sheet which reads much like the CASA sheet...

Proposed AC 43-16A Maintenance Alert

Cessna: Model 336/337 Skymaster: Asymmetric Flap Extension; ATA 2750

This model aircraft has experienced an asymmetric flap extension as the result of a failed flap cable. The failure of the cable was caused by excessive wear at the right hand inboard bellcrank. The wear location was at the tight radius bend on the bellcrank prior to the termination point of the cable. The cable wear was on the inside radius of the bend and would not be noticeable without removal of the cable.

The Model 336/337 Maintenance Manual requires a 100 hour inspection of the flap cable system. It is recommended that maintenance personnel treat this bellcrank and all others in this system as a “critical fatigue area” as defined in AC 43-13, chapter 7, section 8, paragraph 7-149(b). As such these areas require close visual inspection, which can only be accomplished by removal of the cable from the bellcrank. As recommended in AC 43-13, chapter 7, section 8, paragraph 7-149(d) the suspect cable should be removed and inspected for wear and broken wires. It is recommended that the cable be bent as shown in the figure below to check for broken wires on the interior of the cable. The cable state should then be compared against the requirements of the Cessna Maintenance Manual and/or AC 43-16 to determine if the cable should be replaced.

Part Total Time 2892.6 hours

Again, this is fro 2003...not 2008, and the issue most certainly was known. A photograph of the inspection point may be viewed here:

A picture of the cable broken in the area in question:

And the location of the break...

Or just read the whole thread...

http://www.337skymaster.com/messages/showthread.php?t=547

Again, the Canadian alert to which you referred...issued in 2003. Your incident was July 2008, was it not?

 

[phr8dawg]

Read the blog next time. And I rest my case about flamebaiters.

 

[avbug]

I read the blog. Your outfit stacked up an airplane based on known safety information which had been available for five years. Go figure.

Flame bait? This from the man who wants rockets and safety nets for flying a Cessna 336 in and out of dirt airstrips? Your post is flame bait, your blog is flame bait, and no, you're not doing the "lord's work" by stacking up airplanes on hillsides for preventable mishaps. Call it what you will, but hiding under the guise of god and love for mankind still doesn't except you or your outfit from stupidity.

 

[phr8dawg]

Its not my outfit BTW. You are a jerk. Goodbye.

 

[avbug]

Its not my outfit BTW.

It's not your outfit? So when you said "We lost the aircraft," you really meant someone else lost the aircraft? You're not a part of the "we" any more?

FYI: We lost the aircraft due to a mechanical failure unrelated to the airport.

Read the blog next time.

Problem is that the blog is by the same folks who committed this act...not really the source to which we should turn for insight here, is it?

Your organization had five years notice...that's five years of knowing about this problem in multiple countries as cited above...but you didn't know...even though it had been addressed and discussed even in the US.

Cessna skymaster organizations knew about it. Your organization flew or owned two of them, and according to the blog are trying to sell the second one to pay for another airplane. Don't you do any research?

I did. Apparently doing research makes you a jerk...therefore you should not do research, and stick to crashing aircraft on airstrips that are too short, using airplanes that are improperly maintained, for which you compensate by adding safety nets to the hillside and contemplate rocket assisted takeoffs...while justifying your stupidity in the name of missionary work. Good on ya, mate. This still doesn't make you a "jerk," though? You won't have to try much harder to achieve that status...you're very nearly there.

I can think of a few other adjectives, though. Foolish, idiotic, stupid, half-baked, among others, leap to mind.

Goodbye.

Thank heavens. It took you long enough...with so many opportunities to slink away and save some dignity and credibility intact, you were unable. Congratulations on finally taking the plunge.

 

[TMMT]

This is better than a tennis match!

 

[phr8dawg]

Why would someone claiming to have two years in the field refer to the
Creator in lower case letters? What's the real issue?

TMMT: You are the only one here with an opinion. Congrats.

 

[avbug]

Why would someone claiming to have two years in the field refer to the
Creator in lower case letters?

Why would I not. I had four years of seminary and formal religious training as well and field missionary experience, but I'm not a Jesus-freak holy-rolling lunatic. Your organization gets a few flights out of an airplane before negligently pasting it inverted on a hillside, after considering rocket assisted takeoffs and arrested landings with nets...and you're worried about what I capitalize?

Which creator is it to whom you think you refer?

Goodbye.

Apparently not. You're not very good at this, are you?