Overdue Cargo Airplane Bound for CYXS

[Unit 969]

If the wing spar carry thru AD was completed properly, I cant see it failing. It is also subject to a recurring inspection. However I have seen the wing to fuselage skin attachments crack again even after repair, and have seen the castings inside the aircraft cracked. During the scraping of a Metro II we cut 3/4 of the way through the wing spar near the fuselage and were still unable to break the wing with a front end loader. The carry thru AD is complicated and takes special tooling, manpower and a lot of hours to do correctly. Done incorrectly or missing defects during re-inspection is the only way I could see the wing breaking off.

[North Shore]

So if the wing is bulletproof, then perhaps the tail...
Poor guys.
My thoughts to the families..

[ogc]

There are a couple of ADs on this aircraft regarding fatigue cracking at the wing spars and the wing attach fittings.

With respect to the comments directed to the TSB, do you people really think the TSB is NOT working effectively when they investigate these crashes? Why bash them for no reason? Is it because they are a government institution?

In my experience they are a very professional and responsible organization that not only does a good job investigating, they do the proper thing when it comes to disseminating information.

There are AD's for wing spar cracks and from what ive heard it is pretty common

[midwingcrisis]

I am unfamiliar with the Metro II/III/23 but understand the initial airframe life @ 35,000 hrs can be extended to 50,000 hrs. Does anyone know the detail of obtaining this extension and what the focus of attention is on?

[boeingboy]

It wasn't originally lifed but is now due to the damage tolerance design requirements. They envisioned 35,000 hrs but as all operaters incroperate the SID/STU-MOO inspections into their maintenance programs.....it is a seemless transition to 50,000. The Horizontal stab is lifed. It is life limited at 40,000hrs. After that you replace it. Everyone thought that no-one would do this but Perimeter has done it to a few planes. They have the highest time machines anywhere I believe.

The STU-MOO/SID inspections lay out in great detail the structural inspection requirements for the aircraft.There are not many unknowns about the airplane. With the testing done - I'll bet sometime in the future they may extend the life to 100,000 hrs!

[boeingboy]

Some interesting FAA fatigue tests....

3.5.2.1 Fuselage Fail Safe Tests.
As reported in reference 5, after 98,000 hours of the SA226 full-scale fatigue testing, a small saw
cut was made in the T-stringer at the fuselage crown. The growth of this crack was monitored.
At the completion of the test, the saw cut was extended to 5 inches along the stringer and the full
7 psi cabin pressure was applied without failure.
A saw cut was also made at 98,000 hours in the two most highly stressed hat channels on the
forward pressure bulkhead. These cracks were allowed to grow to the end of the test at which
time the full pressure load was applied without failure.
The fail safety of the cargo door latching system was substantiated by removing one of the clickclack
latches and subjecting the remaining latches to 15 cycles of full pressurization. The
remaining latches held the door without failure.

3.5.2.2 Wing Fail Safe Tests and Analysis.
Complete fail safety analyses were carried out for the SA226 and SA227 wings for certification
[ref 2 fail safety reports]. These analyses showed that failure of any one element of the forward
or rear spar caps would not cause total failure of the wing at limit load. This was also shown by
test during the SA226 full-scale fatigue test. At 98,000 hours of the test, 0.050-inch saw cuts
were made through the depth of the main spar cap at fastener holes at stations 9 and 99. Since
the simulated cracks did not grow, they were artificially extended at the end of the test and
subjected to limit load without failure.

3.5.2.3 Empennage Fail Safe Tests.
When the initial saw cuts were made in the wing and fuselage, similar cuts were made in the
empennage. A cut was made in the vertical tail main spar at about waterline 130. The cut was
made in a fastener hole, in the direction away from the spar web, and was long enough to extend
beyond the fastener head so that it could be monitored for the remainder of the test. A saw cut
was also made in the horizontal stabilizer rear spar at about butt line 20. This cut was made in
the last fastener hole where the strap at that location ends, in the direction away from the spar
extended at the end of the fatigue test and subjected to limit load. Neither of the simulated
cracks caused failure.

[boeingboy]

A/C has been tested to 105,000 hrs without failure

Therefore, the time to onset of WFD for the wing, fuselage, and tail structure is determined to be
greater than 105,000 hours with a high degree of certainty and greater than 50,000 hours (the
goal of this program) with a very high degree of certainty.


Here is the full report plus all the required inspections for anyone interested...
http://www.tc.faa.gov/its/worldpac/techrpt/ar00-18.pdf

[midwingcrisis]

Thank you boeingboy. Interesting where you mentioned in your earlier post where SKC was at with airframe TT/Cycles, and the document you posted. Curious if you have knowledge of a "high time" airframe example in Canada.

[boeingboy]

Not specifics. The ones I was intimate with were a lot younger than these. However most metro 2's are in the 30,000 hr range, 3's are around the 20,000 hr range and 23's are 10,000.

Like I said - I think Perimeters are the highest time ones around with a few in excess of 40,000hrs. They have replaced the tails on those ones.....but I don't know the actual number of hours.

[fish4life]

Perimeter has had a few hit the 50000 hr mark only to be turned into pop cans

[gimmepars]

A/C has been tested to 105,000 hrs without failure

Therefore, the time to onset of WFD for the wing, fuselage, and tail structure is determined to be
greater than 105,000 hours with a high degree of certainty and greater than 50,000 hours (the
goal of this program) with a very high degree of certainty.


Here is the full report plus all the required inspections for anyone interested...
http://www.tc.faa.gov/its/worldpac/techrpt/ar00-18.pdf

Reference 5 was the Fairchild full scale fatigue test. I would like to see how they simulate the type of flying the previous posters mentioned and which many of us have heard about at regional cargo operators, not to mention the temperature and moisture extremes and constant exposure to salt air these old airframes are subjected to out here on the west coast. I would not be surprised if that document is revised as a result of this investigation.

[boeingboy]

maybe....

[Illya Kuryakin]

Bloody sad day. Can't come up with anything. Going to have to wait this one out. Just hoping it doesn't take two years.
Illya

[midwingcrisis]

History of C-GSKC from birth

http://aviation-safety.net/database/rec ... cation=ufi

[xsbank]

Two of the things that used to keep me awake at night after a particularly evil pizza - midair and inflight breakup.

Godspeed you guys, we all feel your loss.

[cncpc]

I'm curious to know what, if any, changes have happened at Carson Air from the day following this accident.

Was a memo sent out, any emergency inspections, any aircraft grounded pending...?

An airplane comes apart in the air and it seems odd that business would carry on as usual. I'm not saying it has, but interested in how operations might have changed after this accident and with these aircraft.

[howard40]

I shudder at the thought of sudden airframe failure....Sincere condolences to the families and friends...

[ei ei owe]

Has there been any talks about a gear well fire? That, unfortunately, is a possibility.

[floydfrank]

There was nothing reported to do with fire, either prior to or after the aircraft (or parts thereof) impacted the ground.

[boeingboy]

Has there been any talks about a gear well fire? That, unfortunately, is a possibility.

Pretty unlikely. There would have been multiple issues long before it broke up.
Not to mention it only happened once, the crew knew about it, and they made multiple major screw ups.

[Diadem]

There was nothing reported to do with fire, either prior to or after the aircraft (or parts thereof) impacted the ground.

There was a small fire in the area of the right engine nacelle.

http://www.tsb.gc.ca/eng/enquetes-inves ... 5p0081.asp

[wallypilot]

Does the metro have any gear well fire warning system?

[Taxivasion]

Does the metro have any gear well fire warning system?

Not necessarily. It has a "Wing Overheat" light, which if I remember correctly gives you about 12 mins to get on the ground if it's a true wheel well fire before it burns through the spar and you have wing seperation. If that light ever came on they advised get the gear out of the well and land asap.

[cncpc]

Does the metro have any gear well fire warning system?

Not necessarily. It has a "Wing Overheat" light, which if I remember correctly gives you about 12 mins to get on the ground if it's a true wheel well fire before it burns through the spar and you have wing seperation. If that light ever came on they advised get the gear out of the well and land asap.

In the picture below, I'd venture this is the left wing. It seems that may be part of the fuselage lying across the top beside it. This wing is upside down in the picture. Obviously.

The gear is extended backwards, rotated about 90 degrees from the down position. No sign of burning and that wing didn't separate.

TSB says that there was a small fire in the right nacelle. Does that mean they have the whole right wing?

No one at Carson seemed to want to comment on what if anything changed the next day.

[Meddler]

Don't hold your breath. If a couple of my buddies had just died I wouldn't be in a rush to explain everything to you or to avcanada.