Happy-flier
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Air Canada Flight 621: Reasons For The Go-around?

Thu Aug 19, 2004 5:26 am

Back in July, the story of the ill-fated Air Canada flight #621 that crashed on a go-around from YYZ 34 years ago made the news. As I read through the details of this sad incident, I remained puzzled by one thing: Why did the captain choose to execute a go-around after the aircraft hit the ground so hard following spoiler deployment by the FO some 60 feet above the runway?

The transcript is online at http://aviation-safety.net/cvr/cvr_ac621.shtml.

In a previous discussion, someone pointed out that ATC may not have had a view of the DC-8-63 when it hit hard and lost engine #4, so the crew might not have realized what happened right away. But I would think that with such a hard drop onto the runway, the impact itself would have been cause for not going around. And the other thing that puzzles me is the suggestion that there wasn't enough runway to stop the aircraft following impact. Arriving from Montreal, wouldn't the aircraft have been relatively under-fuelled? And besides, runway 32 is over 11,000 ft. in length. Did the DC-8 hit the runway at the halfway mark?

There are lots of things that I can't reconcile when trying to create an image of those critical moments. I'd appreciate any additional thoughts/input.

(BTW, a book is apparently going to be released next year, on the 35th anniversary of the accident. If anyone knows the release date, publisher, etc., please reply. Thanks.)

[Edited 2004-08-18 22:26:39]
May the wind be always at your back . . . except during takeoff & landing.
 
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longhauler
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RE: Air Canada Flight 621: Reasons For The Go-around?

Thu Aug 19, 2004 9:46 am

When the first officer (in error) deployed the spoilers, the captain pushed the throttles to go around thrust to arrest the sink rate. This also restowed the spoilers.

The aircraft hit the ground at the 400 ft mark of the 10500 ft runway and bounced back into the air with the engines at go-around thrust. Climbing away from the runway, the captain elected to go around, and called for go-around flaps.

This decision was not wrong, in fact, the investigators even commented in the final analysis, that the decision was not wrong, however once the decision was made, the outcome was irreversible.

FYI, engine number 4 did not hit the ground, it was "flicked" off the wing with the impact, and took a piece of tank 4A with it, now spilling fuel. The engine still running, (yes!) actually flew through the spilling fuel and ignited it, causing the results.
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Happy-flier
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RE: Air Canada Flight 621: Reasons For The Go-around?

Thu Aug 19, 2004 12:11 pm

Thanks for the explanation LongHauler. I didn't think about arresting the sink rate as being a factor. I wonder, if the captain had not done that, whether the aircraft would have broken up on initial impact? It very well may have.
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longhauler
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RE: Air Canada Flight 621: Reasons For The Go-around?

Thu Aug 19, 2004 12:25 pm

It said in the report, that had the FO deployed the spoilers 0.5 seconds earlier or later, then the result would have been quite different.

0.5 seconds earlier, then the Captain would have been able to reduce the sink rate enough to have a safe landing. 0.5 seconds later, and the plane would have crashed on the runway, but would likely have been a surviveable crash.

Also, had it been a DC-8-61 vs a DC-8-63, as was the original plan, then also, the crash likely would not have happened. The aircraft were switched at the last minute. AC805 YUL-YYZ-YEG was switched with AC621 YUL-YYZ-LAX. They departed 30 minutes apart.
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Happy-flier
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RE: Air Canada Flight 621: Reasons For The Go-around?

Thu Aug 19, 2004 12:31 pm

Also, had it been a DC-8-61 vs a DC-8-63, as was the original plan, then also, the crash likely would not have happened.

Would this be because of the difference in pylon design? Just casually observing the two types seems to me to suggest so. The -62/-63 series pylons are hung from the underside of the wing, while the -61 pylons seem to overlap right over the wing surface a bit.
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longhauler
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RE: Air Canada Flight 621: Reasons For The Go-around?

Thu Aug 19, 2004 12:41 pm

Two reasons actually.

The DC-8-62 and -63 pylon design was in question after the accident, as it was deemed less sturdy then the DC-8-10 to -40, or the -50/61 design. However unlucky, the pylon design was not deemed to be unsafe. (Although, when breaking away, it should not have taken a part of the fuel tank with it!)

Also, in the earlier versions of the DC-8, the spoilers were far less likely to deploy in the air. In fact, it was the mistrust of the DC-8-62/63 system that caused the pilots to not follow Air Canada SOPs.
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