Classic British Flight Sim

I believe that as well Nigel, Ben .

It always comes down to people.

I asked the question knowing the answer to dissolve any illusion that the cowl and latch design were
the culprit. It's the man who's putting his hand to the task, or not putting the brain into gear when putting hands to the task.

Not to brag, but I've been called to to fix issues in electrical systems after others tried to fix and call no joy.

This is a hard one to explain. I mean this stuff ain't hard.

See, a lot of people can pass a test that's required to perform a job.
But many of them haven't the insight to figure things out by themselves, they have to be taught....
They don't "see it".


I see this with a lot of people in my trade.
and it's down right scary to think they are off by themselves wiring buildings.
they replicate the physical motion required to, set a panel, pull a circuit and wire a device. But put them in a building where lights emit higher lumen output suddenly and then return as suddenly to the output at which they were designed.

Haven't a clue....

ahhhhh

But then.. what kind of electricians are them anyway..... plumbers - who just had their heads blowed up.


I posted this before and asked if someone here "who said they could do 12 volt wiring" could say why it was,
the service grounded conductor and three of the branch circuit grounded conductors wires were overheated but the other two branch circuit grounded conductors were not.


the truth of it is... 12 volt dc or 12 ac or 48v dc or 120/240 208/230 277/480 ac etc etc etc
can all have instances such as this.

Chris Trott wrote:Nigel - not disagreeing that this case was one of human error. However, the design is also suspect as it has been faulted in at least one other case as it lends itself to being an issue. What we don't know here is whether there was an issue and the mechanic who performed the IDG check reported it or not. This is the question I have. As these latches will not work if not properly adjusted, it is possible that the mechanic encountered a problem when attempting to re-latch the cowlings and reported it for further action and that action wasn't taken.........

IF there was an issue then the system failed again. The maintenance carried out was scheduled maintenance iaw the AMM and the approved maintenance programme for the aircraft. As the aircraft was released for service, it indicates that the task was completed and the fan cowls closed iaw the AMM and signed off on the task card by the Mech and the Inspector, and then signed off on the Maintenance Control Sheet. The key issue here is the aircraft was released for service after a task that required duplicate inspection, i.e. 2, repeat 2 people had to sign off that the fan cowls were closed and latched iaw the AMM. If there was an issue, would you, as the Mech or as the inspector, sign off the fan cowls as closed and latched? I certainly wouldn't.

It also doesn't account for the number of times a plane arrived with one or more latches "unlatched" due to this problem but there was no separation of the cowling and it didn't get reported as a "mishap" or even a maintenance item.

Then that is a serious breach of the company's flight safety policy and culture and again is a systemic or procedural failure that leads to the erosion of any sort of safety margin and will ultimately cause and incident or accident. Nothing to do with the actual serviceability of the aircraft.

This from Airbus in 2007, go to page 14, you can see there are a number of modififcations, Service Bulletins and Airworthiness Directives to do with Fan Cowl latches.

http://www.airbus.com/fileadmin/media_g ... -SEQ02.pdf

Specfically


Human Performance Error Management
Maintenance Briefing Notes

The events of fan cowl door losses were reported randomly over the past years, and in every case the post-incident investigations revealed the same findings:
• The cowls were opened for maintenance prior to the flight;
• The cowls were found un-latched and not properly hooked and secured;


Similar incident

http://www.ntsb.gov/aviationquery/brief ... 078&akey=1

Again, procedural errors evident. He signed the Maint docs saying that he had entered the info in the tech log, yet the check that was mandatory for the flight crew didn't spot the open latches. You would have thought that the latches would be closely looked at if the tech log indicated they had been opened??

From a Transport Safety Board Canada report on a Skyservice A320 fan cowl separation. (My bold text)

The fan cowling of each engine includes two semicircular fan cowl doors fitted between the engine intake cowl
and an aft-fixed cowl. Each door is approximately 4.7 feet wide and 10 feet high. They are of bonded sandwich
construction, with carbon fibre composite skins, and an aluminum honeycomb core. The left door weighs 93
pounds, and the right door 103 pounds. The doors are mounted at the top, on four hinges attached to the
forward part of the engine pylon. They can be propped open by two stays carried on the interior of each door.
The doors are secured closed by four latches, attached to the lower edge of the right door, each of which
contains a hook that engages in an adjustable eyebolt, fitted in the lower edge of the left door. The hook is
operated by an over-centre linkage in the latch, driven by a pivoted stainless steel handle, which is locked with
a spring-loaded catch. Maintenance manual procedures require eyebolt adjustment to produce a latch handle
closure load of 45 to 55 pound feet.

Each latch assembly is mounted on a pivot pin attached to the right door. When engaged, the latch assembly fits
flush with the bottom of the doors. When not engaged, rotation of the latch assembly is limited by an anti-
swivel plate, also carried on the pivot pin and itself able to rotate approximately 20 degrees.

In fact, see the whole report here:

http://www.bst.gc.ca/eng/rapports-repor ... 0o0199.pdf

Of interest

The flight crew was qualified for the flight, the maintenance crew were qualified for the maintenance activities,
and the aircraft was determined to have been serviceable for the flight. Consequently, the analysis will focus on
human factors, operations procedures, and fan cowl position indication.

Nigel

Further from the Canadian report

Five walkaround checks were completed by three qualified personnel before the aircraft departed, but none
noticed the unlatched cowlings. This included CC2 picking up the rag underneath the left engine. All of the
personnel associated with the aircraft before its departure were aware of the need to check the latches. They
were also aware of the placards directing this action; however, none of them could identify the location or
number of the placards.

Nige

Nigel,

It seems that Airbus has attempted to rectify the situation with various modifications, however, I note only the CFM installation has a revision to the springs (which presumably makes them an "over center" latch). The CFM's I assisted with had the original design as I described which (to my understanding) is substantially identical to the IAE latches.

Also, I did find this Safety Reccomendation from the NTSB that I think is somewhat more concerning to me that was released in late 2008, a year after the Airbus document you linked -

http://www.ntsb.gov/doclib/recletters/2 ... _79_82.pdf

I've not dealt with the CRJ cowlings to know if they use the same kind of latch or not, but it proves this is not a small issue as both the CRJ and Airbus family have seen a disproportionately large number of cowl separations and latches not being secured or unsecuring themselves.

It's an interesting discussion as I've found no examples of the CFM as installed on the 737 having this issue nor any example of the MD-90 having a problem with the IAE, which again goes back to - why is it that the A320 family seems to have this happen far more often than anyone else?

A stall situtation during an emergency return to the airport after separation of the no.4 engine cowlings was concluded to have caused a fatal accident involving a Boeing 707 cargo plane , according to the UAE General Civil Aviation Authority (GCAA). It was also concluded that there was poor safety oversight within the airline as well as by the Sudanese CAA.

The Transport Canada report provides a great image on page 14 of the IAE latch.

I have not personally dealt with this style, but it is substantially the same as the original CFM latch. The silver "button" in the middle is not a mechanical latch, it is simply a "pushbutton" to push the latch far enough from the cowl so you can get your hand into the end and pry the latch open. On the CFM, this pushbutton doesn't exist on the original design and instead there is a "slot" at the end of the handle where a screwdriver can be inserted and the latch pried open. I've seen mechanics use the screwdriver method to open the IAE cowling as well (specifically on United Airbuses). On Boeing aircraft equipped with CFM engines, there is a similar latch design, but the pushbutton actually actuates a catch that releases the latch from the faired position. The latch is actually hanging loose in this position and can be easily moved up and down from the faired position (where it latches) to this unfaired position. On the Airbus, there is tension on the latch all the way from initial cowling contact to fully latched.

NigelC wrote:A stall situtation during an emergency return to the airport after separation of the no.4 engine cowlings was concluded to have caused a fatal accident involving a Boeing 707 cargo plane , according to the UAE General Civil Aviation Authority (GCAA). It was also concluded that there was poor safety oversight within the airline as well as by the Sudanese CAA.

I was specifically speaking of the CFM-eqiupped 737's, not any Boeing aircraft. Both the CFM on Airbuses and the CFM on 737s use cowlings manufactured by Goodrich Aerospace.

Just came across that by chance

Consequently, the analysis will focus on human factors, operations procedures, and fan cowl position indication.

That is the key statement. Forget type, manufacturer etc.

Airbus have stated that the greater number of incidents occurs on the A320 family because of the low ground clearance.

As before:

Five walkaround checks were completed by three qualified personnel before the aircraft departed, but none
noticed the unlatched cowlings. This included CC2 picking up the rag underneath the left engine. All of the
personnel associated with the aircraft before its departure were aware of the need to check the latches. They
were also aware of the placards directing this action; however, none of them could identify the location or
number of the placards.

Nowt to do with the type. They are all qualified, they all know where the latches are, and they all know the consequences of the latches not being fastened.

Quick look

Incident: Turkish Airlines B738 at Vienna on Jul 18th 2010, parts of engine cowl separated

A passenger reported to a B737-500 crew that an engine cowling panel separated on the runway at touchdown.

Can find other instances on 737, 747, DC8 etc

B737=200 didn't drop used to drop cowlings but the whole engine!!!!!

Anyway, footie's starting, back later!!

N

Thanks Nige, I've looked at the incidents, and one thing sticks out on all the other types (including 2 DC-9/MD-80 incidents) - they all occurred on touchdown. All of the Airbus incidences have occurred on takeoff. That is what I find interesting.

Also, this is the reason I was specifically comparing the 737 and the A32x family. The 737 actually has LESS ground clearance under the engine than the Airbus. So if the Airbus has had 22+ incidences and the 737 family has had less than 10 (which is what I've been able to find) and there's nearly 4 times as many CFM-equipped 737s versus A32x family aircraft, what is the difference between the Airbus and the Boeing that causes the Airbus cowling to be more susceptible to separation? I'm not making a conclusion or giving a possible reason, just saying that there is something about the design of that cowling that has made it more likely for it to be left open and fail than on other types and the focus needs to be finding out why that is and not blaming just the people.

One of the things the Railroads here in the US discovered over a century ago is that it's only "human factor" if it applies across the board. If it only occurs on one type of equipment, then there's something about the equipment that makes it more prone to failure and thus that needs to be addressed and not just blame the humans for doing what humans do - make mistakes. I see here a pattern of failures that seems to occur more on cowlings produced for 2 different manufacturers than anyone else by several magnitude. I thus see the need to address not only the human factor, but the mechanical factor because you can't prove that some of these airlines are just putting the least intelligent crews and maintenance personnel on their Airbus fleets. If they are, then maybe that's something that needs to be addressed too...