Thursday, September 13, 2007

Two Outta Three Ain't Bad?

The SAS gear collapse accidents have sparked a lot of conversation on the internet and in the crew rooms. A landing gear failure like this is pretty rare, and two identical failures within three days of each other is downright spooky. We actually had a gear unsafe indication on one of our planes (the Party Barge) a few days back, but thank God it was a different problem than on the SAS airplanes and the crew was able to successfully extend the landing gear.

There's been a lot of discussion online about the configuration the crew chose to land the airplane in. Some of this has amounted to Monday morning quarterbacking by the uninformed: on FlightInfo, "The Russian" was vigorously arguing that the crew should've secured both engines and made a deadstick landing (and should've touched down softer as well!). Of course, on a Q400, shutting down both engines results in the loss of all AC power, most DC power, all hydraulics, and your job. More reasonable people (like Olli from my comments) have asked whether the crew should've at least secured the right engine to prevent the spectacular prop fragmentation and engine fire seen on the video of the Ålborg crash.

I personally think the Ålborg crew did a fine job. Reports indicate that they followed the alternate gear extension and emergency landing checklists to a tee; if SAS checklists are like ours, they don't direct you to secure the engines until after the airplane has come to a stop, which you can clearly see them doing in the video. Beforehand, they moved the passengers to the left side of the airplane and away from the prop arc, which isn't in the checklist and indicates that they were mindful of the danger from the prop disintegrating. There is a Kevlar shield on the fuselage along the prop arc, but it's intended to prevent dings from ice chunks, and indeed one section of prop blade ended up penetrating the cabin. Thanks to the crew's precautions, it didn't injure anybody. As for the engine fire, CFR crews were right there to quickly extinguish it.

Interestingly, the Vilnius crew did secure the right engine before landing. Of course, they had the hindsight of the Ålborg crash three days prior. The Vilnius plane suffered much less damage, mostly due to the right prop not turning but also due to a softer touchdown (more luck than anything in a Megawhacker) and the slight left bank on landing. If you've never flown a twin engine airplane, it's standard procedure to slightly bank into the good engine when you have one secured, as this produces zero sideslip and decreases the rudder pressure required to keep going straight. Now, shutting down an engine isn't in the Emergency & Abnormal checklist, but is the sort of decision the Captain has the power to make in an emergency. In this case it worked out so everybody is saying how smart the Captain is. If it exacerbated the situation everybody would be jumping all over him or her for not just following the checklist.

The alternate gear extension checklist actually directs the pilots to make a belly landing if they can't lower both mains. The Ålborg video clearly demonstrates why: to avoid catching a wingtip and losing directional control while still at significant forward speed. It turns out that in both of these incidents, the landing gear wouldn't retract. The crews were forced to land on the nosewheel and left main.

Although the grounding was originally voluntary, Transport Canada has issued an emergency airworthiness directive that requires the visual inspection of all Megawhackers in addition to the detailed inspection of those that have over 10,000 cycles on the airframe. At least we finally have a description of the inspection so our maintenance crews can get to work. We cancelled another 140 flights today, but it sounds like we'll start getting planes back on the line by tomorrow. So it seems like I will indeed be flying my last trip on Sunday through Wednesday.


Anonymous said...

I'm glad you're leaving.

Sam said...

Because of the gear problem? As dangerous design flaws go, this one's pretty mild. Every new airplane has bugs to get worked out of it, and the JungleBus is a lot newer than the Megawhacker.

amulbunny said...

I had a pax who lost a cellphone at T3's checkpoint today call and make a report and she said she was shuffled between gates and eventually was flown to PDX on American. She said that Horizon treated them well and the gate agents at LAX were pretty shook about the grounding.
Hope the JungleBus treats you well.
PS How's Dawn doing in the Twins?

Olli Vainio said...

Thanks for your answer Sam :)

There's a preliminary statement by Dannish Accident investigators about the cause. It can be found here if you're interested.

There's also new photos by Dannish newspaper that show the extent of the damage.


§kyye said...

Hey there, great pics of the PNW area. I live in Vancouver as well... the BF flies out of PDX. How's the new job?

Industrial Accidents said...

Great post! yesterday i found another great video post about Industrial Accidents. Here is the link
Industrial Accidents