Wednesday, February 18, 2009

A few words about Colgan 3407

My story related to the JungleBus' FMS will have to wait for the next post. I've been debating whether I should write about Colgan 3407; I generally take the "let's wait for the investigators to do their jobs" approach to airline accidents. Unfortunately the media doesn't share this sentiment in the least, and in their drive to solve the accident before the wreckage is cold they've put out a tremendous amount of disinformation in the last week. Few of the media's sources appear to have any experience flying turboprop airliners, much less the Q400. While my knowledge of the airplane isn't perfect and has faded a bit in the year and a half since I last flew it, I do have a few thousand hours in it.

I'm not going to speculate on what caused the crash. All that I know about the circumstances are what's been reported by the NTSB thus far and repeated in the media. The morning after the crash, enough was already known that there were only a few likely culprits. I myself suspected it was one of two scenarios. The first known facts made one seem most likely, and subsequent information is now shifting the investigation towards the second possibility. The media hasn't reported accurately on either scenario, with a few exceptions. There's a decent chance that more information will come to light that will take the investigation in a completely different direction before it's all over. To say I have any idea what really caused this accident would be a farce. I will, however, give my take on some of the ways the known information has been interpreted and reported to the general public.

"Significant" versus Severe Icing

Because the air traffic controller was prudent enough to collect icing PIREPs from other pilots immediately following the accident and the audio of those interactions was immediately available on LiveATC.net, speculation that this was an icing accident reached a fever pitch before the fire was even out. The investigation now seems to be proceeding in a different direction, but it could came back to icing as a contributing factor.

The media seized upon the NTSB's statement that the crew noted "significant" icing on the descent. They've treated this term as the equivalent of severe icing, even though the NTSB has specifically said they have no reports or evidence of severe icing in the area. There were a number of other airlines that landed just prior to and after the accident aircraft. One that landed a half hour later was another Colgan Q400. There were also several light aircraft in the area at the time. The very worst reports of icing were for what would normally be considered moderate. None of the airliners requested routing or altitude changes to get out of the ice, and nobody even bothered giving a PIREP until the controller started soliciting them after the accident. That's not what a bad ice night in the northeast sounds like. Although icing conditions can vary significantly over small changes of distance and time, it seems rather unlikely that one crew could encounter severe ice when multiple pilots around them were barely noting it.

Ice and the Q400

Horizon has been flying the Q400 in the Pacific Northwest, Montana, and southwestern Canada since 2000. This area gets its share of bad icing conditions every year, and the Q400 has shown itself to be up to the challenge. It does have deice boots, but they generally do an excellent job of keeping the leading edges of the wing and tail clean in moderate icing. The one problem spot is that the deice valves sometimes freeze closed, but this is immediately annunciated in the cockpit with a "Deice Pressure" caution message and nine times out of ten the crew can cycle the system off and on and get the valve to unstick. The NTSB has indicated that the deice system was turned on before the aircraft entered icing conditions (which was Horizon's procedure, too), and there were no obvious, annunciated malfunctions of the system.

It's easy to tell when you're getting a lot of ice on the Q400. The windshield wipers are excellent collectors of it, and there's a little plastic pin on the top of them that accumulates ice before any other part of the airframe. The cockpit even has a built in light to illuminate the pin at night. All of the wings outboard from the engines are visible from the cockpit, as is the unprotected propeller hub. Both are well illuminated by ice inspection lights.

As soon as the ice detection probes detect ice, a message starts flashing on the EICAS and won't stop flashing until the pilots select the ice speeds switch on. This makes the stall protection system speeds 20 knots faster, forcing the pilots to use adjusted ice speeds for landing.

I've had decent ice loads on the Q400 several times, including one thankfully short encounter with icing possibly falling into the "severe" category. The airplane has so much excess power, especially down low, that performance wasn't even an issue. I never felt that controlability was an issue either, although I suppose it's pretty easy to get to the edge of controlability in ice without realizing you're at the edge (more on that later).

Turboprops under Fire

Given that the Q400 is a turboprop with deice boots, there have been (premature) parallels drawn between this accident and others involving turboprops with boots. There has been a fair amount of insinuation that turboprops are inherently dangerous in ice. Today, former NTSB chairman Jim Hall, who now partners in an aviation litigation firm, carried this idea to it's ultimate, idiotic conclusion: all twin turboprops ought to be immediately grounded.

It's true that jets are superior to turboprops in ice. The reason has a lot less to do with equipment than with performance. Yes, hot leading edges are nice and do a better job of keeping the wing perfectly clean in "normal" conditions. In severe ice, though, hot wings are just as susceptible as boots are to runback (ice forming behind the protected area). A jet aircraft's main advantage is that its superior performance and greater altitude capabilities allow it to get out of ice quicker and stay out for longer.

That said, I believe turboprops can be safely operated in icing conditions so long as their pilots monitor the situation carefully, know the limits of their equipment, and always have an out if things get nasty. Overall, turboprop pilots have done a great job of doing just that. Two icing accidents out of 30 years and millions of hours of flying small turboprop airliners does not make them inherently unsafe, as some would have it - especially when you look at what actually happened in those accidents. One involved prolonged flight through supercooled water droplets (SLD), which wasn't widely understood but we now know is the worst kind of severe ice, because it runs behind the protected areas before freezing, with drastic implications for controlability. The other involved getting too slow in an iced up airplane on which the deice system had not been activated. Both of these had little to do with the systems or limitations of a turboprop aircraft, and could've as easily happened in a jet. To use these accidents, plus a currently unsolved accident in which ice may have played a factor, to call for the grounding of all turboprops is the height of insanity.

Tailplane Stall

One subset of the icing scenario which attracted the most attention among pilots but received fairly little coverage from the media was the possibility of a tailplane stall. The reason it caught so many pilots attention was the NTSB's announcement that Colgan 3407 suffered an upset immediately after the pilots selected Flaps 15, and NASA's previous research has shown that flap extension can cause a nearly-stalled tailplane to stall. Subsequent information from the flight data recorder, however, appears to contradict the tailplane stall sceneario.

On all conventional aircraft, the wing is positioned so that the center of lift is behind the center of gravity (which is essentially the pivot point of the aircraft during maneuvering). This causes a nose-down, tail-up pitching moment whenever the wing is producing lift. To compensate, the horizontal stabilizer is designed to generate tail-down force. It does so with an airfoil much like an upside-down wing. Like a wing, the horizontal stabilizer can only generate lift up to a certain angle of attack. Beyond that critical AoA, it stalls, or ceases to generate lift. When that happens, the aircraft rapidly pitches down thanks to its natural pitching moment.

Under normal conditions the tail is pretty hard to stall. At slow speeds where the boundary layer might tend to separate, the aircraft is usually flying at a higher AoA, which is actually a low AoA for the tail. Lowering flaps decreases the aircraft's AoA, making it greater for the horizontal stabilizer, generally at slower speeds where the boundary layer can detatch more easily. High-wing aircraft with conventional tails, like the Twin Otter, also generate quite a bit of downwash on the tail with flap extension, which further increases the A0A. Throw in some ice contamination and you have the potention for real trouble: an unexpected, rapid pitch down at presumably low altitude. It looks a lot like a conventional stall, but the recovery is exactly opposite: pull up, retract flaps, and go easy on the power. Aircraft with unpowered elevators can be very difficult to recover from a tailplane stall, with stick forces of well over 100 pounds required.

The Q400 has a hydraulic-powered elevator, which would make recovery from a tailplane stall much easier, assuming you know it's a tailplane stall and take the appropriate recovery steps. I'd be surprised if this accident had anything to do with a tailplane stall due to more recent information that's come to light: the initial upset was a pitch up, not down, and the autopilot disconnect was precipitated by the stick shaker. A stick shaker indicates critically high aircraft angle of attack, which would be a low AoA for the horizontal stabilizer.

If you're interested in learning more about tailplane stalls in icing - and if you're a pilot who flies in ice, you should be - there's a very interesting NASA video for you to watch here. Of particular note is the inadvertent tailplane stall they experience in a Twin Otter.

On Autopilot Usage

For a few days there was an absolute uproar over the fact that the aircraft was on autopilot just prior to the upset. If anything indicates the media's cluelessness about how we operate airliners, this is it. I'm a big proponent of turning off the automation and hand flying the airplane at times. A dark, snowy night when I'm about to shoot an approach is not one of those times. That's when you use the automation to keep your workload low. Yes, if really iced up, I'll turn off the autopilot early to get a feel for the plane. But there's nothing in the Q400 manual (or Colgan's procedures, apparently) that says you have to hand-fly the airplane except in severe icing. The media acted as though Captain Renslow was being negligent merely by having the autopilot on in fairly normal icing conditions. That's baloney.

Now, automation does pose its own hazards. You need to make sure its doing what you want it to do, and you have to do your own part. The Q400 has a very capable autopilot but it doesn't have autothrottles. You need to pay attention and bring up the power when leveling off from descents or its possible to get into a low-airspeed situation very quicky; those 13 foot props produce a lot of drag at flight idle.

A Big Upset

The most recent information the NTSB has released is that the aircraft was approaching the marker and was at 134 knots at the time gear was selected down and flaps selected to 15. If that number turns out to be correct, that is a very, very low speed in the Q400 without being in the landing configuration. Shortly after the flaps were selected to 15, the stick shaker and then the stick pusher activated, which automatically turns the autopilot off. An upset occured at that time, with pitch angles as high as 31 degrees nose up and 45 degrees nose down, and bank angles as high as 105 degrees.

That's a pretty huge upset, and one difficult to recover from at 1500 feet even if done perfectly with a clean, undamaged airplane. Although it's only been about a day since the media started letting go of their ice obsession and began reporting on the low speed upset, there's already been a fair amount of finger-pointing that the pilot flying let the aircraft speed get so slow, or that he supposedly pulled up and fought the stick pusher. Suffice it to say that we know very little about what was going on other than those basic numbers that the NTSB has released. It'll come out soon enough; this investigation is unusual in that the NTSB has been releasing information more or less as they find it out rather than waiting to put together a final report in a year or two. The point is, though, that until a lot more is known, about all we can say is that the aircraft appeared so suffer from a low-speed upset. We don't know why, we don't know whether icing was a contributing factor, we don't know whether recovery was possible. All those answers will come with time; in the meantime, any certitude on the part of the media, most of their sources, bloggers, or web board participants is mere affectation.

43 comments:

Mike said...

Excellent post!!

jinksto said...

Agreed! Well done... thank you. I've had people talking to me about this crash and I find that I spend most of the conversation saying... "yeah, but it doesn't work like that". Maybe I'll send a few over to read this instead.

Anonymous said...

Thanks for the educational post. I'd like to hear more about your take one what happened as more information is released. Could you explain the flaps at 15 thing? I'm not sure what that means. Thanks.

Brent F. said...

Sam:

Thanks for the great post! I always look forward to reading your blog.

I've got a question about the significant pitching and rolling that occurred. I'm a freshly minted private pilot with not a whole lot of hours, so I'll probably get this a little wrong, but it sounds like the plane might have entered a spin? A pitch up then down sounds like a stall of some sort, then the bank left and sharply right with it "breaking over" (past 90 deg) sounds like the plane might have been uncoordinated? I don't know if this is still an issue with the bigger planes, like the Q400, but is that a possibility? I would assume that a spin at 1500' in a big plane like that would probably not be recoverable...

I guess the better question is why the plane would have even gotten to that point anyway...

Thanks again, keep up the good work!

Sastre Air said...

Great post Sam. As a commercial pilot, people tend to ask me questions about accidents like this, and I always try not to speculate. But at the same time, I'm very intrigued to find out what really went wrong. Thanks again for a very informative post.

Jtsastre

leadZERO said...

Nice post!

After reading that, the talk of the pilot fighting the stick pusher makes me wonder if he hadn't suspected a tail stall. Would it be possible that the nose down pitch caused by the stick pusher made the pilot suspect a tail stall, accounting for his attempt to pitch up?

RPS PP-SEL

Aviatrix said...

I've heard that Colgan recurrent training includes that NASA video, and that the captain had very recently done his.

A stall at flap extension (for the person who asked: flaps are panels that hinge down at the back of the wings to improve the low-speed flight characteristics; flap 15 means 15 degrees of extension) matches the symptoms, even if it was the wrong diagnosis.

Was there anything unusual about the descent profile given 3407, that might cause them to use a non-standard power setting?

Bob Collins said...

I grow weary of the generalizations against the media -- being both a pilot and a member of the media, of course.

But the facts are that there ARE parallels between this crash and other crashes, not so much in the conclusion that ice was THE culprit (by the way, contrary to the assertions, no media has made this assertion.), but that how the crew handled itself.

The question about the autopilot isn't whether it was or wasn't on. The question is whether the policy of the airline was that it was on or off. It's not baloney at all.

There's a parallel to this. It's the crash in Hibbing some years ago when CONCERN about icing -- as opposed to icing itself -- caused the captain to depart from company policy, fly an unstabilized approach, and put it down into a taconite tilings hill, because he lost situational awareness.

Did that happen here? I don't know. But if several planes landed safety and one didn't, *I'd* sure think the actions of the crew are a logical place to focus.

The other aspect of this crash is one that I'm sure is uncomfortable for many pilots at regionals -- whether the crews at regionals are as experienced as the crews at majors.

The flying public -- through the paint job and branding -- are led to the conclusion that it's all one big airline. Is it?

By the way, I -- and about 500 other journalists -- wrote about tailplane icing before you did. You have to remember that some people in the media, know how planes fly. And how they don't.

Sam said...

Sorry for lumping the media into one single, incompetent entity in my post, Bob. The main object of my ire is cable TV news, followed closely by network TV news. Within print journalism the wire services are the main culprit. Many individual newspapers, and perhaps some smaller TV news outlets, do make the effort to get people who know what they're talking about reporting on technical subjects.

Regarding the experience level at the regionals, that's something I've written about fairly extensively myself. It remains to e seen whether that's even a factor in this accident but it's still a compelling safety issue. Here's one posting you might find interesting:
http://fl250.blogspot.com/2007/11/are-regional-airlines-safe.html

Regarding autopilot usage: what I wrote isn't simply my opinion, it's the basis of autopilot usage policy at most airlines. People who work for Colgan say they are strongly encouraged to use the autopilot at all times - except in severe ice, of course. In discussions on the crew's autopilot usage, that fact has been mostly absent or barely mentioned.

I agree that the actions of the crew are likely going to be the focus of this investigation...but if you're going to damn those who aren't around to defend themselves, you'd sure as hell have all the facts. I'm deeply uncomfortable with accusations of crew incompetence or negligence until after all the relevant facts are known. Now, nobody in the media has come right out and said the crew was negligent, but the facts are often presented in such a way that the uninformed viewer/reader will form their own opinion to that effect.

Bob Collins said...

And that would be my biggest problem: That "the media" has come to be associated only with cable TV and -- let's face it -- we're talking about people paid to look pretty and read what's written.

As far as crew response, I haven't heard any allegations of crew incompetence. I have heard the reporting on crew reaction.

As you know, these sorts of things are usually part of a chain of events, the breaking of any link at any time breaks the chain and prevents the tragedy.

THAT, to me, is the tragedy. That as we all look for the single boogeyman, there's usually about 20 completely understandable human reactions in that chain.

I admit that my first reaction to the crash was that it couldn't be icing because they hadn't mentioned anything about it. But I'm careful not to say "it's the crew's fault" because, well, it's just not accurate,or at least not informative.

I agree with your point about the uninformed viewer/reader. And while I may disagree with elements of your post, you and your blog remain one of the most prized components of my RSS reader.

Fly safe.

Anonymous said...

Bob, has anyone ever suggested to you that you may be a jackass?

Bob Collins said...

Of course. And -- with the exception of my first wife -- all were too timid to identify themselves.

Sam said...

Haha, funny thing is that most of the people who've suggested *I'm* a jackass on my blog have been anonymous, too!

Sarah said...

Sam, thanks for your expert views on this puzzling accident. It seems like every day a new theory pops out of the press &/or blogosphere.

I don't have more than a fascinated amateur's background on the issues, but share the desire to figure out what the heck happened.

Interesting new tidbit about the 23 ILS at BUF: plane Buzz

Bob Collins said...

I think the NTSB is still holding daily briefings. That's why every day there's something new out there, I believe.

Anonymous said...

Bob-

Unfortunately most people think "the media" is CNN or FOX etc.

Sam's post is speaking in general terms. There's no way he can say "well on CNN they said this, but on NBC they said that and in the Buffalo News they said something else."

The fact is, there are way, way, way too many unknowns to the general public, media and others for any logical conclusion to be made. Taking Sam to task for saying "the media" is kind of....well...irrelevant to the whole big picture of what his post was about.

-chris (former newspaper photojournalist and aerospace engineering student)

Paul said...

This is the best analysis I have seen in print on this subject (since I agree). Sam, I am in MSP also, and vitally interested in practical stall training. I would really appreciate a direct contact.
sarephen@aol.com

Sam said...

I just got done with a crazy 4 day trip that included bad weather, ground holds, holding, a divert, cancellations, and a reschedule to a minimum rest overnight followed by a 14 hour duty day - so I've been unable to address individual points or questions until now. Thanks for your patience!

Anon 7:37, the Q400 has 5 flap settings: up, 5 degrees, 10 deg, 15 deg, and 35 deg. Landings are normally made at Flaps 15 or Flaps 35. In this case the crew was planning on a Flaps 15 landing. Reasons to choose Flaps 15 over 35 is for a Cat III approach or a gnarly crosswind. Some pilots also like Flaps 15 because it's easier to make a nice landing, although the chances of a bad landing resulting in a tailstrike are greater. One more possibility - and understand this is purely speculative and very well may not have been the case with this crew - is that someone concerned about the possibility of an icing-induced tail stall could choose Flaps 15 since it results in less downwash on the horizontal stabilizer.

Sam said...

Brent F - the NTSB hasn't really released enough FDR data to determine whether the aircraft actually spun. My guess is that 1500 ft isn't enough altitude for a spin to fully develop, but like you say they got to some pretty massive bank angles, and they crashed on the opposite heading from that they were on when the upset occured. Keep in mind that little is known about most transport category aircraft's deep stall characteristics, because only recovery from the most basic, benign stalls is required to be demonstrated. That's why most are outfitted with stick shakers and pushers. The other day I read the NTSB report from the Comair icing crash at DTW back in 97, and one thing that struck me is that they couldn't really analyze the FDR after about 4 seconds into the upset because Embraer didn't have *any* aerodynamic test data on the EMB120 once boundary layer separation reached 40% of chord. They simply hadn't tried that deep of a stall for fear of losing the test aircraft.

Regarding coordination or lack thereof: no data has been released on that yet, but I will remark that the Q400 has some massive left turning tendencies when power goes from flight idle to MTOP (max power). If you don't use a lot of right rudder, the inclinometer gets way off to the side.

Sam said...

LeadZero/Aviatrix: It's possible that the Captain had tail stalls on the brain. We may never know - even if he was thinking it, he may not have been concerned enough about the possibility beforehand to mention it aloud. It's true that the aircraft type he just came out of, the SF340, is known for being more susceptible to tailplane stalls, and I've also heard uncorroborated reports that he'd just finished recurrent training that included the tailplane stall recovery video. If the NTSB feels that his response to the stick shaker/pusher has no other logical explanation, they may do a little speculation of their own in this area.

Avi- Haven't heard anything about *nonstandard* power settings. The Q400 has three vertical modes: pitch hold, IAS hold, and vertical speed hold. The most common method for descent is to use vertical speed hold, and then adjust the power levers to maintain desired speed (which at Horizon, was typically redline minus 3 knots in the absence of ATC restrictions!). In a descent of 2000 fpm or greater at 240 kts, the power would be near flight idle.

Rauch Planetarium said...

I am shocked by what you said about Jim Hall. I had not heard this and find it to be something that for me has erased any credibility that Mr. Hall had.

As a very, very frequent flyer I have logged a few thousand hours in the DASH-8, the worst weather the Northeast can dish out. I am completely comfortable flying this or any similar turboprop aircraft. Shame on Mr. Hall for saying all of them should be grounded.

Love your blog and will return often.

Sam said...

Sarah, I'd seen that bulletin as well. I think people are reading a bit much into it. Firstly, the spurious glideslope signals have been detected north of the localizer, and the accident crew was intercepting from the south. Secondly, the 737's flight director/autopilot (and those of some other Boeing products) handles glideslope capture differently than that of the Q400. In the 737 it's possible to capture the glideslope before the localizer has captured, which could result in the AP chasing the spurious signals in that area well off the localizer. In the Q400, though, the FD/AP will not capture the glideslope until after the localizer is already captured (the JungleBus is the same way).

Of course what's getting everyone's attention is that whole remark about the pitch-ups being "as much as 30 degrees." I don't know whether any aircraft - SWA or otherwise - have actually experienced such a steep pitchup due to spurious glideslope signals north of the localizer, or if that remark came from the writer prematurely connecting this to CJC3407. I kinda suspect the latter is the case.

flight plan said...

thank u for explaining so clearly i am a flight attendant for Colgan Air i fly the q400 as a crew member i am proud of my work and the crews i fly with i just want to say may the crew and pax rest in peace for the rest of us left behind fly proud and high for those on flight 3407 ... it is a difficult time for us all of us

Jim Mantle said...

EXCELLENT POST.

What are the typical approach speeds in a Q400?

Stumper said...

Excellent article. Has anybody speculated about the possibility of an ineffective or inoperative deicing boot on the tailplane? From your description, I gather that there is a cockpit indication about the open/close position of the valve that controls the boot operation, but could the valve be open and the boot still be inoperative?

Wayne Conrad said...

I'm curious what's changed at the NTSB that's caused them to become a political, daily-press-conference organization. Unless I haven't been paying attention, that seems new. In the past, it's always been: "We'll let you know in six months or a year when the investigation is complete." But daily press conferences with releases of findings from inside the investigation? That's new.

Sam said...

Jim--

Depends on the weight. At middle to heavy weights, we typically had a Vref of around 115 for Flaps 35 & 130 for Flaps 15...approach speed is 10 kts over Vref. Ice on the airplane increases all speeds by 20 kts (you could really be screaming on in!). Someone who's flown the airplane more recently than I could provide more exact numbers.

Stumper - Each individual boot on the wings, horizontal & vertical stabilizers, and engine cowl inlets each had its own annunciator light. This light was activated by the boot reaching a certain pressure. Failure of the valve to open, or a tear in the boot, will result in a deice pressure caution light, confirmed by the absence of the boot annunciator when you go to MANUAL mode and select that boot. So the answer is that I'm not aware of any failure modes that wouldn't be annunciated.

Wayne - I know, it's a little disturbing to me as well. There have been a LOT of leaks to the press, too. Then again, the public never seems to pay much attention when the final report comes out, even when it highlights big problems in the system that are still ongoing.

Sam said...

OK, correction to my last comment, I remember how we did it now. Vref(ice) was 15 knots over Vref, and would typically split the bugs (Vref+7 or so) for a non-ice approach and carry a few knots over Vref(ice) for Vapp when ice was on the plane.

Matt said...

Thank you so much for what is finally an honest, upfront, and seemingly neutral analysis of what happened during 3407's final moments.

I knew Becca Shaw, FO, as a friend, colleague, and my dispatcher in college. She and the captain deserve better than the finger-pointing, rush to conclusion coverage the media has displayed. As a CRJ FO myself, I know there are far too many variables for the news to simply say "ice", or "autopilot", and I can only hope they learn from their mistakes made reporting on this sad event.

The Cope Family said...
This comment has been removed by the author.
The Cope Family said...

Excellent commentary. Your write-up addresses the situation with fact and personal experience which makes it far more worthy of reading.

I wanted to add one item concerning the pneumatic boot de-icing system on the airplane. I know almost nothing about the Q400. With that said, I flew the Saab 340 for 8 years with Mesaba Airlines and experienced boot failure in icing conditions twice without an annunciation in the cockpit. Our pilot operating manuals indicated this wasn't possible, but a lengthy discussion with a mechanic shed some light on the situation. The short version is, if the line that carries air to the boot system contains moisture and freezes causing a blockage AFTER a pneumatic pressure sensor, then the system will indicate proper function but the boot will not inflate due to the blockage. The sensor sees good pressure but it never gets to the boot.

Both of the instances that involved my flight lacked inflation of any kind on the outboard boot without a fault indication in the cockpit. The only indicator was when I looked out the window and failed to see a break up of ice, while the FO's wing had shed ice normally. On the last occasion, and the one that prompted my in-depth questioning, this led to a rolling moment due to assymetric ice removal, followed by additional assymetric ice formation and removal cycles while going into Erie, PA. If the fault had occurred on the tail, or even the inboard boots, I would not have known.

The only reason I bring this up is because what is said to be true by a pilot operating manual isn't always the case. Again, I have no idea what the parallels are between the Saab 340 and the Q400 de-ice systems, but cockpit annunciators are only as good as their design allows.

I must finish by saying that the Saab took very good care of me and I enjoyed flying this very capable airplane for the time that I did. I fly the 737 for Alaska Airlines now and icing events in this airplane are far less "exciting" for a number of reasons. The guy that says all turboprops should be grounded immediately is an idiot and obviously has another agenda. When I checked in the early 2000's, the Saab 340 had a safer history than nearly all commercial airliners based on total hours (or miles?) flown. The Dash 8 must rank right up there also.

To Bob, you may report accurately on aviation related issues, but you can't deny that MOST of your colleagues do not.

Anonymous said...

Fantastic post. Interesting to me, however, as a former commuter pilot now flying at the majors, is that no one seems the least bit concerned that the FAA and NTSB has "busted" the "myth" of bridging without doing a proper comparison between the "old" technique of building ice till you're a little uncomfortable and then popping the boots ONCE, then waiting for another good buildup, and the "new" technique of switching the boots on to "auto" like some Pavlovian monkey, then going brain dead in glib confidence that your life is safe in the hands of a bunch of bureaucrats who never fly and their spurious "findings". READ those studies - they aren't valid!

I believe bridging was at the very least a contributing factor, and possibly was the primary cause, of this tragedy.

All you young bucks out there - you can be legal and turn your boots on immediately, or you can be safe and do what Goodrich Aerospace (the inventor of deicing boots!) recommended for 75 years: build that ice till you get nervous, then pop the boots - just be sure you pop them one last time before approach, before you extend flaps, and don't even think about trying to go slow till you're on the ground!

If that means you can't land because the runway's too short or too slick, divert and/or CANCEL!

Sam said...

Cope Family - great story & commentary, and point well taken. I certainly don't know the Q400 systems on a mechanic's or engineer's level, it's entirely possible that its boots have unannunciated failure modes the book doesn't talk about.

Anonymous 2:51--
You know that last sentence of my post, where I said any certitude on the part of anyone not directly involved in the investigation is a mere affectation? It most certainly applies to this statement of yours:

"I believe bridging was at the very least a contributing factor, and possibly was the primary cause, of this tragedy."

Saying that blew a lot of your credibility for me. Secondly, it was NASA that concluded that ice bridging wasn't as serious of a threat as previously thought, not the FAA or NTSB. They did so after a lot of lab testing using equipment BFGoodrich couldn't have dreamed of 75 years ago, as well as seeking out and flying in some pretty nasty real-world conditions. I'm not saying ice bridging is a myth: I've actually seen it, but that was after following your exact advice of waiting before blowing the boots since that's how we did it on the Chieftain at Amflight.

As far as the "new" technique being "switching the boots on to 'auto' like some Pavlovian monkey, then going brain dead in glib confidence that your life is safe in the hands of a bunch of bureaucrats,' that's a straw man if I ever saw one. You seem to think all the turboprop pilots have gone brain dead since you left the commuters, even though they have a far better safety record than they used to. Auto or Manual, any pilot worth his salt is going to be monitoring how the wings are doing and adjust his boot usage as necessary while he exits those icing conditions expeditiously.

The only reason I didn't dismiss your comment outright is that the last part contained a good deal of wisdom:

"ust be sure you pop them one last time before approach, before you extend flaps, and don't even think about trying to go slow till you're on the ground!

If that means you can't land because the runway's too short or too slick, divert and/or CANCEL!"

Amen to that.

Anonymous said...

Sam-
Affectation, huh? Perhaps, but only out of angst against the continual dumbing-down of this profession being perpetrated by our government "experts". If I was showing off just for self-aggrandizement, wouldn't I gladly sign my name? The reason I don't is that I don't want to have a Fed sitting on my jumpseat for the rest of my now-five-years-longer career.

Nothing I wrote was intended to mean that ANY pilot, current or former, passenger or freight, military or civilian, commuter or major, is actually GOING to go brain-dead after hitting the "auto" switch on their deice controls; but only that that is PRECISELY what the NTSB and FAA seem to be seeking from us when they broadcast ill-begotten conclusions (yes, fine, of a "NASA" study, as if that makes any difference) like "bridging is a myth" (their words, VERBATIM - look it up! Look up the rest of this "study" while you're there, and you too may see how flawed it was), only because ONE crew of ONE flight (Comair, 1/97) elected to not activate their boots before slowing to a speed that would have been creepy-slow with CLEAN wings, and they want to prevent the rest of us "idiot pilots" from exposing ourselves to THAT risk, while simultaneously exposing ourselves to another, just because their own database (which only goes back so far) doesn't have any bridging-related accidents in it.

I don't doubt that you experienced bridging or something like it. I never said that "my" (actually Goodrich's 70-year-old) recommendation would PRECLUDE bridging. I only said that it was the accepted BEST way to operate boots to prevent it from occurring. There is a subtle difference, and I think you're intelligent enough to see that, if you'll drop your defenses long enough to see it.

I'm frankly amazed to see someone imbued with so much otherwise good, impartial information so reluctant to accept that perhaps just once in a while the government tries a little too hard to protect us from ourselves.

My point was simply that the NTSB and FAA (NASA has no governing function over us) have overreached with this edict, and should have instead simply admitted that pilots can and do make mistakes sometimes, sad as that is, but that tying our hands with nonsensical procedure isn't always the best way to keep us out of trouble.

The Cope Family said...

Sam,

I noticed in one of the earlier posts that it was stated the 737 can capture the glideslope prior to localizer capture. I just wanted to chime in from my corner of the industry and say that our (Alaska) 737s won't do that. I fly the 737-400/700/800/900 models. The GS capture function is inhibited until VOR/LOC (localizer) capture occurs. Perhaps the reference was to older models of the 737? I can't speak to the older ones. Once again, nice job on the blog.

Anonymous said...

Sam - Your blog on 3407 was very insightful and well written. I am an expert in the field who will remain quiet. I want to invite you to particpate in a reaearch program that involves some very interesting flyng. Could you please vist www.Calspan.com/URT. Once there press "contact" button and put attention "jep".

Anonymous said...

rumor head from an ALPA guy...

no sterile cockpit what-so-ever.

Anonymous said...

Excellent post.
I have several thousand hours in charter, corporate, and airline turboprops and jets. Your article was very well thought out and written.

I agree that all pilots should watch the NASA video on icing. Flight Safety and many airlines have been using it for years to instruct pilots.

Unfortunately the largest obstacle to turbo prop safety is the experience of the crew. Yes, that was me too at one time. I was fortunate that I flew with experienced captains while I was figuring it all out.

It is easy to recovery from an attitude upset in the sim and the aircraft when you are ready for it. The problem lies in having the experience to know that you are in a dangerous situation that may lead to such an upset..and avoiding it. The fact that the crew had icing and continued to violate sterile cockpit proves that they didn't have that experience. Yes, I have violated that law many times, but never in IMC on an ILS.

Do all commuter pilots lack experience? NO! I have many friends still in the business. MOST of them have MORE experience than the main line pilots. But you do get what you pay for. The Colgans and Mesas get pilots who have low time. Because of high turnover at those airlines, they never keep pilots once they are experienced. Those airlines are basically training facilities with student pilots building time.

Turboprops are safe if safely operated (like all aircraft).

Anonymous said...

I agree with anonymous above. The NTSB changed the way we operate boots after Comair 3272 crashed, and they are WRONG, WRONG, WRONG. I was involved (only slightly) in the study. Bridging does NOT occur with continuous operation of the boots, but you can not get a clean wing either. Performance in moderate icing is severely degraded with the boots operating continuously, and in an unpredictable manner (one wing may get more contaminated than the other causing unknown stall characteristics).

The problem is that the NTSB wanted a definitive procedure in response to Comair 3272. They had 2 options: 1. force the airlines to install ice detection systems and tell pilots to operate the boots continuously in icing which they knew only worked poorly. Or, 2. Trust pilots to rely on their judgment as to when to "pop" the boots.
In the spirit of bureaucracy, not changing the procedure was not an option.

We are operating less safe than we were before Comair 3272. I nervously await the new change that will come from the Colgan investigation. At least the public can rest assured that the NTSB is on the job.

Anonymous said...

Nicely thought out blog post. When I heard about the crash initially I was wondering about tailplane icing and the possibility of SLD (supercooled liquid droplet) icing which would result in icing aft of the boots.
Looking at the NTSB animation I'm baffled at the power lever positions. It looked just like he was setting up for a stall in the sim. I have around 4000 hours in transport category turboprops and our stall profile was pretty much in line with what I saw on the animation. Level off with reduced power and add drag in the form of flaps and gear. Predictably it results in a stall. This type of training was only done in a simulator. Recovery for a stall was to leave pitch attitude alone and simply power out of it.
I noted the FO apparently took it upon herself to raise the flaps. I have no idea what she was thinking at the time as no stall recovery calls for a configuration change until the aircraft is under positive control and generally climbing. Maybe she was a low time pilot who simply panicked.

I think an ATP certificate should be required before anyone steps inside a Part 121 cockpit.

Kent Wien said...

Thanks Sam for the great write up. I've been reluctant to comment as well, since it's just so easy to be wrong early on in an investigation.

I finally couldn't keep quiet anymore:

http://www.gadling.com/2009/05/25/plane-answers-chit-chat-did-not-doom-colgan-flight-3407/

Thanks for your take. It's was good to hear from someone with time in the Q400.

Kent

RonRuss63 said...

Now that the NTSB report is out, how does it square with the comments that have been written?

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