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Preliminary Report On SAS Q400 Accident In CPH

CPHGuard From Denmark, joined Jun 2006, 254 posts, RR: 0
Posted (2 years 2 weeks 2 days 10 hours ago) and read 1675 times:

The report can be found here:

http://www.hcl.dk/graphics/Synkron-L...DI%20Preliminary%20Report%20UK.pdf

Extract from the report:

Technical investigation
During aircraft recovery, the right main landing gear remained in a partially extended position.
The right main landing gear was inspected and no visible damage or failures were observed which could have resulted in the event.
In order to lower the right main landing gear, the retraction actuator was removed to allow manual extension of the gear to the down and locked position. The actuator was found intact and the rod end was not disconnected. The landing gear ground locks were installed and the aircraft was towed to a hangar.
The technical investigation is focused on the right main landing gear and actuation assembly.
In order to isolate the fault, a known serviceable actuator was installed and the landing gear system was functionally tested. The system functioned normally.
The suspect actuator was taken to a workshop where a detailed examination was carried out.
This examination identified a blocked orifice within the actuator assembly which prevented the complete extension of the right main landing gear. This finding is not related to the two previous accidents which occurred in September 2007.
The source of the blockage is unknown at this time and the investigation continues.

13 replies: All unread, jump to last

XT6Wagon From United States, joined Feb 2007, 1814 posts, RR: 3
Reply 1, posted (2 years 2 weeks 2 days 9 hours ago) and read 1632 times:

Congradulations SAS, I guess its not all the Q400's fault is it?

CPHGuard From Denmark, joined Jun 2006, 254 posts, RR: 0
Reply 2, posted (2 years 2 weeks 2 days 9 hours ago) and read 1606 times:

Quoting XT6Wagon (Reply 1):
Congradulations SAS, I guess its not all the Q400's fault is it?

I should be careful to speculate at this point BUT:

The actuator was one of the problem items on the first two crashes. I'm pretty sure that they have been changed to new ones, which means it is a brand new actuator that has failed.

This leaves manufacturing flaw and mounting flaw.

The report states that the actuator was in place, so i guess it leans toward the first option.

FlyHoss From United States, joined Feb 2005, 598 posts, RR: 0
Reply 3, posted (2 years 2 weeks 2 days 9 hours ago) and read 1593 times:

Quoting CPHGuard (Thread starter):
The suspect actuator was taken to a workshop where a detailed examination was carried out.
This examination identified a blocked orifice within the actuator assembly which prevented the complete extension of the right main landing gear. This finding is not related to the two previous accidents which occurred in September 2007.

This reminded me of a BE 1900 incident many years (Sept. 1988) ago in Denver:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X26808&key=1

From the probable cause for the 1900 incident:

POST-INCIDENT EXAMINATION DISCLOSED FOREIGN MATERIAL LODGED IN POPPET SEAT AND RETAINER OF LANDING GEAR ACTUATOR EXTEND PORT. ACTUATOR WAS CLEANED, REASSEMBLED, AND FUNCTIONALLY TESTED OK.

A little bit louder now, a lil bit louder now...

GPIARFF From , joined Dec 1969, posts, RR:
Reply 4, posted (2 years 2 weeks 2 days 9 hours ago) and read 1555 times:

Quoting XT6Wagon (Reply 1):
Congradulations SAS, I guess its not all the Q400's fault is it?

Although It's possible that a part was designed wrong or malfunctioned to cause the blockage I think it is probably equally possible that this is an incorrect or poor maintenance issue as well.

At FCA/GPI where I work Horizon flys Q400's all the time and although they are the most mech. delayed airline here it's 99% of the time electronic or avionics related. I think that on some of the other threads there has been alot of misunderstanding of the types of incidents and accidents that the Q400 has been involved in. Any retractable gear aircraft type is going to experience cases of gear malfunction. The often quoted incidents of nose gear failure and (from the preliminary report here) this incident are not proof that this aircraft has systemic flaws in the landing gear. They are unrelated mechanical failures. But the two first RMG failures at SAS were related both in type of malfunction and airline. That is why many are questioning whether or not SAS's maintenance procedures or climate might have something to do with those two specific incidents.

While i take it as truth that Bombardier isn't necessarily the worlds best at customer service I can not believe that the they are sitting back saying "who cares if its our fault that these planes are malfunctioning You Bought them so deal with it!". Don't you think it is their responsibility to determine whether or not they are actually complicit in the problem before they pay to have it fixed? If it was their fault They Will Pay.

That being said If this incident was caused by a mistake on SAS's part this will only cast more doubt on their ability to properly maintain their aircraft and could help cause their dumping of the Q400's to backfire.

CPHGuard From Denmark, joined Jun 2006, 254 posts, RR: 0
Reply 5, posted (2 years 2 weeks 2 days 9 hours ago) and read 1532 times:

Quoting GPIARFF (Reply 4):
I think it is probably equally possible that this is an incorrect or poor maintenance issue as well.

But the part was brand new.....

Arrow From Canada, joined Jun 2002, 2105 posts, RR: 2
Reply 6, posted (2 years 2 weeks 2 days 9 hours ago) and read 1532 times:

AIRLINERS.NET CREW
ARTICLE EDITOR

Quoting GPIARFF (Reply 4):
That being said If this incident was caused by a mistake on SAS's part this will only cast more doubt on their ability to properly maintain their aircraft and could help cause their dumping of the Q400's to backfire.

Nice to see a rational analysis. There's been a huge rush to judgment on this without any information at all about why the LG failed to extend. It may well end up in Bombardier's lap, but it's still too soon to pass judgment.

Never let the facts get in the way of a good story.

XT6Wagon From United States, joined Feb 2007, 1814 posts, RR: 3
Reply 7, posted (2 years 2 weeks 2 days 9 hours ago) and read 1525 times:

Quoting CPHGuard (Reply 2):
The report states that the actuator was in place, so i guess it leans toward the first option.

While I fully agree that it could be the quality of manufacture of the actuator, it remains that given its a new install... outside contamination during install is also very likely. It also bears looking at if/how it was tested before being put in service.

Given that the Q400 thus far has not had these same landing gear failures that result in collapse at other airlines, and that a hydraulic part is found to be the cause of a recent rebuilt assembly's failure... I'm putting money on MX issues.

I'm far from the greatest hydraulics expert, but so far as I've seen hydraulic failures are almost always user error. This sounds like someone didn't check all the parts and lines for debris before installing.

GPIARFF From , joined Dec 1969, posts, RR:
Reply 8, posted (2 years 2 weeks 2 days 9 hours ago) and read 1509 times:

Quoting CPHGuard (Reply 5):
But the part was brand new.....

That may be true, I don't know if everyone of those parts on every Q400 was replaced, but I'm assuming that it was hydraulic because it was a blocked port and there are many ways that improper maintenance procedures can introduce foreign debris in the fluid. I'm not taking any sides on the matter just pointing out that there are many different ways an orifice can be blocked and not all of them are the manufacturers fault. Smile

CPHGuard From Denmark, joined Jun 2006, 254 posts, RR: 0
Reply 9, posted (2 years 2 weeks 2 days 8 hours ago) and read 1494 times:

Quoting GPIARFF (Reply 8):
I'm not taking any sides on the matter just pointing out that there are many different ways an orifice can be blocked and not all of them are the manufacturers fault.

And i agree with you 100%.

Contamination could be an issue here.

T prop From United States, joined Apr 2001, 906 posts, RR: 2
Reply 10, posted (2 years 2 weeks 2 days 7 hours ago) and read 1404 times:

Quoting CPHGuard (Reply 5):
But the part was brand new.....

According to this article The actuator assemblies in question are not brand new. The piston and rod end are the parts of the actuator assembly that had the corrosion and were replaced with new. In order to do this someone has to take the actuator assembly apart, replace the piston and reassemble it.

[Edited 2007-10-29 23:56:47]

[Edited 2007-10-29 23:57:23]

Visityyj From Canada, joined Jun 2000, 519 posts, RR: 0
Reply 11, posted (2 years 2 weeks 1 day 18 hours ago) and read 1028 times:

Quoting T prop (Reply 10):
The piston and rod end are the parts of the actuator assembly that had the corrosion and were replaced with new. In order to do this someone has to take the actuator assembly apart, replace the piston and reassemble it.

And also...

Quote:
Steiro adds that the maintenance procedure has also involved applying an anti-humidity and corrosion-prevention sealant, known as Mastinox, to the rod-end threads.

would be nice if the report had identified the "foreign material". expressionless

CF105Arrow From Canada, joined Oct 2007, 284 posts, RR: 0
Reply 12, posted (2 years 2 weeks 1 day 18 hours ago) and read 1016 times:

Quoting Visityyj (Reply 11):
would be nice if the report had identified the "foreign material".

The foreign material is an O ring whose origin is unknown

2nd Prelim. Report On SAS Q400 Accident In CPH (by CPHGuard Oct 30 2007 in Civil Aviation)

[Edited 2007-10-30 12:34:53]

Visityyj From Canada, joined Jun 2000, 519 posts, RR: 0
Reply 13, posted (2 years 2 weeks 1 day 18 hours ago) and read 968 times:

Quoting CF105Arrow (Reply 12):
The foreign material is an O ring whose origin is unknown

Yup, saw that just after I posted (wish there was an edit feature here).

Quote:
The retraction/extension actuator restrictor valve was blocked with an O-Ring. This O-Ring did not come from the actuator and its source is unknown.

I'm guessing it didn't come from Bombardier either bitelip

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