Plane Answers: "Chit-chat" did NOT doom Colgan flight 3407

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Mr, Wien states:

"......pilot failed to notice a loss of airspeed while on approach"

I question this statement. According to the CVR transcript , the pilots had the Vref (landing speed) bugged at 118kts:

22:05:29.5 HOT-1
... uh we got the weather. bugs are set eighteen
fourteen flaps fifteen. uh off of twenty three I forget let me look it up.

So 130kts was roughly the speed they intended to be flying, not an "unnoticed loss of airspeed". The pilots mistake was in setting their bugs incorrectly, not inadvertently letting their speed get too slow.

5-25-2009 @ 8:45PM

Kent Wien said...

That was a confusing part for me in the transcript. I've never heard Vref abbreviated to just the last two digits before, but it might be a Colgan thing. Could they have been referring to the altimeter bugs, perhaps? I looked up the ILS to 23 at Buffalo and didn't find any 18 or 14 in the missed approach altitudes.

Even if the bugs were set at Vref plus any additives, there were no autothrottles, so the airspeed was entirely dependent on what the flying pilot did with the throttles.

Are you suggesting that they mistakenly put in the wrong Vref? That would likely show up in the wreckage, I would think.

I'm open to ideas though. That's a new one that I hadn't heard before. Thanks for bringing it up, Bob.

5-25-2009 @ 9:11PM

Kent Wien said...

Just found this, Bob:

"During one of the briefings, the NTSB said that the crew had selected 114 kts for Vref15 then described the ref speed increase switch (it was turned on) which added 20 kts and resulted in the airspeed bug setting of 134 kts."

So you're right, they had 114 plus additives to the 134 knot ref speed.

The stick shaker activated at 130 knots with the flaps at 10 degrees. Not a lot of room between ref and the shaker it would seem. I look forward to reading the NTSB's report.

5-26-2009 @ 3:30PM

Laura said...

The Vref speed, plus corrections for things like wind and wind gust, etc...is the speed you fly with the flaps at their extended for landing position. That speed is generally too low to be safely flown with less than landing flaps selected. You will note that later in the article that it is mentioned that by the F/O bringing the flaps up, it made the recovery harder due to the need for increased speed at the lesser flap setting. Most jets land with flaps set at 25-30 degrees extended. I do not know the specifics for this one.

5-26-2009 @ 4:46PM

Kent Wien said...

Thanks Laura. They were apparently planning a flaps 15 landing, so the ref speed they chose was based on that.

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