The case of American Eagle 4184 (Oct. 31, 1994): study it well.

[DemoTex]

NARRATIVE: American Eagle Flight 4184 was scheduled to depart the gate in Indianapolis at 14:10; however, due to a change in the traffic flow because of deteriorating weather conditions at destination Chicago-O'Hare, the flight left the gate at 14:14 and was held on the ground for 42 minutes before receiving an IFR clearance to O'Hare. At 14:55, the controller cleared flight 4184 for takeoff. The aircraft climbed to an en-route altitude of 16,300 feet. At 15:13, flight 4184 began the descent to 10,000 feet. During the descent, the FDR recorded the activation of the Level III airframe deicing system. At 15:18, shortly after flight 4184 leveled off at 10,000 feet, the crew received a clearance to enter a holding pattern near the LUCIT intersection and they were told to expect further clearance at 15:45, which was revised to 16:00 at 15:38. Three minutes later the Level III airframe deicing system activated again. At 15:56, the controller contacted flight 4184 and instructed the flight crew to descend to 8,000 feet. The engine power was reduced to the flight idle position, the propeller speed was 86 percent, and the autopilot remained engaged in the vertical speed (VS) and heading select (HDG SEL) modes. At 15:57:21, as the airplane was descending in a 15-degree right-wing-down attitude at 186 KIAS, the sound of the flap over-speed warning was recorded on the CVR. The crew selected flaps from 15 to zero degrees and the AOA and pitch attitude began to increase. At 15:57:33, as the airplane was descending through 9,130 feet, the AOA increased through 5 degrees, and the ailerons began deflecting to a right-wing-down position. About 1/2 second later, the ailerons rapidly deflected to 13:43 degrees right-wing-down, the autopilot disconnected. The airplane rolled rapidly to the right, and the pitch attitude and AOA began to decrease. Within several seconds of the initial aileron and roll excursion, the AOA decreased through 3.5 degrees, the ailerons moved to a nearly neutral position, and the airplane stopped rolling at 77 degrees right-wing-down. The airplane then began to roll to the left toward a wings-level attitude, the elevator began moving in a nose-up direction, the AOA began increasing, and the pitch attitude stopped at approximately 15 degrees nose down. At 15:57:38, as the airplane rolled back to the left through 59 degrees right-wing-down (toward wings level), the AOA increased again through 5 degrees and the ailerons again deflected rapidly to a right-wing-down position. The captain's nose-up control column force exceeded 22 pounds, and the airplane rolled rapidly to the right, at a rate in excess of 50 degrees per second. The captain's nose-up control column force decreased below 22 pounds as the airplane rolled through 120 degrees, and the first officer's nose-up control column force exceeded 22 pounds just after the airplane rolled through the inverted position (180 degrees). Nose-up elevator inputs were indicated on the FDR throughout the roll, and the AOA increased when nose-up elevator increased. At 15:57:45 the airplane rolled through the wings-level attitude (completion of first full roll). The nose-up elevator and AOA then decreased rapidly, the ailerons immediately deflected to 6 degrees left-wing-down and then stabilized at about 1 degree right-wing-down, and the airplane stopped rolling at 144 degrees right wing down. At 15:57:48, as the airplane began rolling left, back toward wings level, the airspeed increased through 260 knots, the pitch attitude decreased through 60 degrees nose down, normal acceleration fluctuated between 2.0 and 2.5 G, and the altitude decreased through 6,000 feet. At 15:57:51, as the roll attitude passed through 90 degrees, continuing toward wings level, the captain applied more than 22 pounds of nose-up control column force, the elevator position increased to about 3 degrees nose up, pitch attitude stopped decreasing at 73 degrees nose down, the airspeed increased through 300 KIAS, normal acceleration remained above 2 G, and the altitude decreased through 4,900 feet. At 15:57:53, as the captain's nose-up control column force decreased below 22 pounds, the first officer's nose-up control column force again exceeded 22 pounds and the captain made the statement "nice and easy." At 15:57:55, the normal acceleration increased to over 3.0 G. Approximately 1.7 seconds later, as the altitude decreased through 1,700 feet, the elevator position and vertical acceleration began to increase rapidly. The last recorded data on the FDR occurred at an altitude of 1,682 feet (vertical speed of approximately 500 feet per second), and indicated that the airplane was at an airspeed of 375 KIAS, a pitch attitude of 38 degrees nose down with 5 degrees of nose-up elevator, and was experiencing a vertical acceleration of 3.6 G. The airplane impacted a wet soybean field partially inverted, in a nose down, left-wing-low attitude.
Based on petitions filed for reconsideration of the probable cause, the NTSB on September 2002 updated it's findings.


PROBABLE CAUSE: "The loss of control, attributed to a sudden and unexpected aileron hinge moment reversal, that occurred after a ridge of ice accreted beyond the deice boots while the airplane was in a holding pattern during which it intermittently encountered supercooled cloud and drizzle/rain drops, the size and water content of which exceeded those described in the icing certification envelope. The airplane was susceptible to this loss of control, and the crew was unable to recover. Contributing to the accident were 1) the French Directorate General for Civil Aviation’s (DGAC’s) inadequate oversight of the ATR 42 and 72, and its failure to take the necessary corrective action to ensure continued airworthiness in icing conditions; 2) the DGAC’s failure to provide the FAA with timely airworthiness information developed from previous ATR incidents and accidents in icing conditions, 3) the Federal Aviation Administration’s (FAA’s) failure to ensure that aircraft icing certification requirements, operational requirements for flight into icing conditions, and FAA published aircraft icing information adequately accounted for the hazards that can result from flight in freezing rain, 4) the FAA’s inadequate oversight of the ATR 42 and 72 to ensure continued airworthiness in icing conditions; and 5) ATR’s inadequate response to the continued occurrence of ATR 42 icing/roll upsets which, in conjunction with information learned about aileron control difficulties during the certification and development of the ATR 42 and 72, should have prompted additional research, and the creation of updated airplane flight manuals, flight-crew operating manuals and training programs related to operation of the ATR 42 and 72 in such icing conditions."

(Emphasis mine)


Fatalities: 68 / Occupants: 68

http://aviation-safety.net/database/record.php?id=19941031-1

In-flight icing can be an inscrutable motherf*cker. I will be posting a de-icing/anti-icing primer in the next day or so (maybe in parts).

So many misconceptions .. so little time.


Dash-8-400 (Similar to the Buffalo crash aircraft)
(BTW: Notice the ventral - belly - strakes between the aft door and the wing trailing edge. Red flags in my book vis-a-vis original aircraft certification. Ventral strakes are sometimes used when the aircraft has a pitch-up problem or to get the nose down to recover from a deep tailplane stall and/or a flat spin from a stall at altitude, like the Learjet 55C.)


ATR-72-212 (Similar to the Roselawn crash aircraft)

[BeGoodDoGood]

1. The Buffalo Crash..........

crew should not have been on autopilot on final approach, should they?

Walt

[DemoTex]

2. I have landed in Buffalo on autopilot: CAT-III AUTOLAND

The autopilot should be used whenever possible, especially during critical segments of flight when the flight crew's work load is high (like on final for an ILS in the snow at night), unless such use of the autopilot is proscribed by the airplane flight manual limitations, company SOP, FAA Airworthiness Directives, or aircraft MEL (Minimum Equipment List) on the autopilot for that particular flight. The use of autopilot is a very good operating procedure.

Conversely, gratuitously hand-flying (auto-pilot off) the airplane during critical phases of flight proves nothing and, in some cases, is borderline recklessness.

[BeGoodDoGood]

21. Seems like I read........

For this aircraft, the auto-pilot was not to be used on final in icing conditions. The pilots can feel better what is happening and react more quickly than the A-P.

[originalpckelly]

4. The NTSB guy said it was the transition from autopilot to manual.

The autopilot corrects for the problems the plane faces from icing, and the pilots don't know exactly how it's steering, they don't have a feel for how things are going.

[originalpckelly]

3. Say what you will, but high speed trains don't fall thousands of feet out of the sky...

to crash and burn in flames on the ground.

There was no reason for this flight, along the NE there is a high population density, and it already supports a robust regional rail system. These people could be here today if we focused on trains for short hops, where they are actually much better than airplanes time wise. In 40 years of operation the Shinkansen in Japan have had no fatal accidents while in operation, the only deaths have been at platforms, where people are too retarded to get on/off a train. I think it was only one or two deaths.

Think about that, that's a hell of a lot less people than even just one flight that crashed of regional air. It's because airplanes have more impact energy and can't be as heavily reinforced because of weight issues.

We can save lives with rail, even if we don't do it for the environment.

[Theres-a]

6. Agreed.

Superior transportation,so underdeveloped.

[originalpckelly]

8. In Europe, high speed trains have replaced regional routes on airlines...

when the lines are built. It's so stupid to risk our lives, I can see it for really low density areas, but the NE certainly doesn't qualify there. I love all forms of transportation, but being enchanted with flying in the sky is not something that should cause an entire nation to adopt one form of transport over a safer one. Trains can also handle higher density in the same space, planes need very large distance between one another.

[hedgehog]

9. I wouldn't call it a superior form of transportation; for example,

high speed rail between New York and London is very impractical for the near future! It's a matter of selecting appropriate technology for given conditions and requirements.

[originalpckelly]

11. Well, for the given flight, it was.

Over the ocean, it isn't at this time, though there are always possibilities, it appears highly unlikely anything would be successful.

There's no reason for air travel between high density areas, unless there is a large body of water between the two points of travel.

[hedgehog]

14. I agree that for the given flight, high speed train travel makes much more sense.

All you have to do is stand at Newark and look at the departure boards to see the 10 o'clock flight to Buffalo, the 10:20 flight to Albany, the 11:15 flight to Rochester, the 11:38 flight to Syracuse, etc, to realize that there is a lot of inefficiency with the system we have in place now. I just wanted to point out that there is no all-around best means of transportation. We have to think in terms of making the best match between needs and technology. Sometimes that means a good pair of walking shoes!

[originalpckelly]

15. Exactly, couldn't agree more!

I'm glad we've got some people with common sense. :P

If only we could take that an infect the rest of our society with it.

[hedgehog]

7. The other advantage is that high speed rail isn't shut down by snow storms,

(at least I don't think so) and can easily handle extra passengers during the holiday seasons. There are reports that New York will see money for high speed rail in the stimulus package. This is an idea that has been kicking around since Jerry Brown ran for President!

[originalpckelly]

10. Not as easily shut down. You're absolutely right...

trains are more resistant to weather delays, exponentially so. Crash survivability is a big plus, even when things go wrong on rail, because there is no chemical propellant on board an electrified train, there is not as much a danger of massive fires burning people/killing them. The high placement of lines means that electrocution is a lower risk. Even if a train does crash into poles supporting the catenary, there's only so much of the train that can be subjected to electrocution because of it's length, and if people aren't ejected from the train, the outer structure of the train can ground the electricity, much like the metal structure of a car protects its passengers from lightning.

[DemoTex]

17. Just a matter of time for high-speed rail. It's gonna happen (even in rail-resistant Texas).

Texas advocates renew push for high-speed rail

But Southwest and Fort Worth-based American Airlines now see the benefit of high-speed rail, Dallas transportation consultant David Dean said.

“The old, post-World War II model of sending planes 250, 300 miles to collect passengers and bring them to central hubs . . . is no longer feasible,” Dean said. “The short-haul flights are dropping like flies in the United States. They’re depending upon passengers to find their own way to the airport. If you have high-speed rail . . . bringing potentially 16 million passengers to your central airports, it becomes a collection system for them. If the rail comes to the airport, they will support it because it becomes a matter of convenience.”

http://trains4america.wordpress.com/2009/02/01/texas-advocates-renew-push-for-high-speed-rail/

The long-proposed Texas Triangle high speed trains (Dallas-Houston-San Antonio, with Austin in the middle) has been blocked for years by the Texas-based airlines: American, Southwest, and Continental (formerly Texas Air Corp.). Like Sgt. Elias says in Platoon, "The worm has definitely turned."

[hedgehog]

5. As near as I can tell, being only an interested bystander, this was a typical type of aircraft

making what amounts to a commuter run between Newark and an Upstate New york airport, landing in typical Upper New York State weather that inexplicably crashed. Any given day between October and May, dozens of matching aircraft make the same landing in similar or worse conditions. Either something was wrong with that particular plane and/or the way it was flown, or else that means that all those other aircraft could also crash during any given landing.


I imagine the same situation holds true in Chicago, Cleveland, Detroit and other airports in the rain shadow of the the Great Lakes. This investigation is important to millions of people who fly in and out of these airports routinely.

[DemoTex]

12. The ATR-72 was grounded from "northern" flying after Roselawn.

The ATR-72s, too, had flown thousands and thousands of hours in icing conditions with no known or reported problems. Then BLAM! A smoking hole in the ground at Roselawn.

The geographic grounding of the ATR-72 in the US was a joke, though. I picked up the mother-of-all-ice-loads in a C-47 going into El Paso in the Spring. Some equatorial countries banned flying of the ATR-72 totally until the accident investigation was far enough along to have a better idea of what happened. A better way to do it is to ban flight into known icing conditions.

Buffalo might not have been ice, but it probably was. Meanwhile, the FAA should ban the dispatch of Dash-8-400s into known icing conditions. That way, when a Dash-8-400 inadvertently flies into icing the captain can declare an emergency and get priority handling out of the ice (with relative immunity).

But you are absolutely right about the flying public's right and need to know the facts about this aircraft. And, in my opinion, the investigation should go back as far as the original aircraft certification (to include test flight cards with test pilot notes and comments, especially from the in-flight icing tests behind the water tanker). If the NTSB doesn't go back that far (and they will), the plaintiff's' lawyers will.

[Hawkowl]

25. Ban flight into freezing drizzle and rain

In my opinion as professional pilot, the FAA has relaxed the regulations into dispatching aircraft into slight amounts of reported or forecasted freezing drizzle. (Freezing drizzle was forecasted and reported for Buffalo). This allows dispatch to cherry pick the weather and put the entire onus of whether to proceed, on the shoulders of the captain. Most captains will exercise good judgment, but others will feel pressure from the company to complete the "mission", relying on the company's interpretation of the regs to proceed into hazardous icing conditions. This problem is compounded when the company, such as Colgan in the Buffalo crash, is operating a new type of aircraft (less than a years operating experience in the Dash 8 Q400).

No amount of freezing rain or drizzle should be allowed period! The pattern of accretion of ice is completely unpredictable. We've all heard how no two snowflakes are alike, right? So it follows that during a freezing rain or drizzle, unpredictable, freakish ice accumulations are going to be normal. Such ice accumulation behind the wing and tail boots (deicing devices) or asymmetrical buildups on one control surface vs. another, resulting in un-commanded rolling, pitching or yawing moments and a subsequent loss of control of the aircraft.

The FAA needs to highlight the danger of freezing drizzle and rain by banning operations into known areas of this type of precipitation. I, personally never, ever fly into an airport reporting this type of precipitation.

[DemoTex]

13. Re: The Q-400 ventral strakes

I have been told that during the Q-400's development testing, the six-bladed propeller slipstream was found, during side-slips at V2, to wrap round the fuselage and impinge on the opposite side of the fin and rudder. This tendency was cured by fitting the two long ventral strakes under the fuselage's rear half. Thus, they serve as "blocking" fences, as opposed to pitch and/or yaw dampening strakes.

[TahitiNut]

16. Is that an aerodynamic result of the "stretch" design?

AFAIK, no such amelioration is evident on the Q100-Q300. (I tend to regard 'stretch' designs to be lazy engineering.)

[DemoTex]

18. Yep on the stretch. Yep on the lazy engineering.

Actually, the engineers probably have no say. Certification of the Q-400 was probably grandfathered in on the original certification of the DeHavilland (Canada) Dash-8 series. However, I don't know that for a fact.

[AZCat]

29. IIRC that's what they wanted on the LR-55 too.

It was supposed to be lumped in with the other LR-Jets, but was determined to be dissimilar enough to warrant a separate cert.

[DemoTex]

32. I've got a lot of time in the Lear 55, and IIRC it was grandfathered under original certificate.

It is certainly the same type rating as the Learjet 23/24/25/35/36 series. I got type rated in a Lear 35 and flew a LR 25 for a couple of hundred hours. Then I spent a couple of thousand hours flying a Lear 55. The common type rating was a joke. I'd kill myself in an older Lear 23 or 24. Seriously kill myself and others. The models are that different.

But, the Lear 55 had some wicked characteristics that were tamed somewhat in the Lear 55C. In fact, I flew the Lear 55C with Learjet's chief test pilot, Pete Reynolds, and we did things that would kill you in a straight Lear 55 (or 23/24/25/35). We did full aft-stick stalls at 51,000 ft! Steep turns at 51,000 ft! The new ventral tail strakes and wing tweeking made all the difference in the world. Reynolds even rolled the Lear 55C several times for me at 15,000 ft. (Bob Hoover, Jr.).


Learjet 55C

[AZCat]

34. You're right, I was confusing it with the LR-45.

It's been a while since I thought about this stuff, and I've forgotten quite a bit.

I know some of the Lears had problems with porpoising - was that the early LR-55? I didn't realize the LR-55C was such an improvement. Full stalls and rolling, huh? I would have been puking in the back.

Yeah, the common type rating was probably the wrong thing to do. You're supposed to train the pilots on differences between the variants of a type, but it didn't seem like that many companies did it. If you're going from the LR-35 to the LR-36 it probably doesn't make much of a difference, but some of the other variants differ significantly.

[hedgehog]

19. Better to say "cheap" engineering. Engineers can and will produce

just about anything given a certain set of specs, and if the most important spec is limited engineering cost, minimum design modification, they'll give you exactly that.

[TahitiNut]

20. "Cheap - Fast - Good : Pick Two" (I'm familiar with the conundrum.)

:thumbsup:

[Missy Vixen]

22. DemoTex, may I ask you a stupid question?

I realize this probably isn't the most intellectual thing you'll hear today, but I have to ask. ;-)

I am wondering if there will come a time that airlines just stop flying into areas of extreme cold because of the risk of icing they can't control. Is this even something that sounds logical? I'm remembering something WillPitt posted the day of the ditching in the Hudson -- that a pilot friend of his had to make two emergency landings that day, too. It was intractably cold over most of the country.

How will climate change affect aviation?

Of course, I'm just curious. ;-)

[DemoTex]

23. Extreme heat will stop the airlines before cold.

In-flight icing is not a problem in 99.99% of the cases in which it is encountered. You will see why when I finish my de-ice/anti-ice primer and get it posted here. Runways contaminated with snow or ice are no problem either, if you follow the rules and use good judgment (like diverting to an alternate when the braking action is reported as "poor" at La Guardia).

Extreme heat, on the other hand, degrades all aspects of aircraft and engine performance (as well as human performance*). I took a 6-hour delay in Phoenix back in July 1995 (as did everyone else) until the daytime high temperatures cooled after sunset. At my scheduled mid-afternoon takeoff time the tower was reporting a still air temperature of 121 degrees-F. That was about 6-degrees F higher than the Boeing 737-300 takeoff charts were designed for (IIRC). No takeoff data .. no go.

*The flight-deck of a jet airliner is a greenhouse. Lots of windows to let in lots of sunlight. Additionally, windshield heat must be on for at least 10 minutes prior to takeoff .. even in Phoenix, even on the hottest day on record .. for bird-strike protection (ask Capt. Sullenberger about that). The A/C is useless in the cockpit on the ground in the summer in the sunbelt. I have taken off from sunbelt airports before with a shirt dripping wet with perspiration from the temperature in the cockpit.

[hedgehog]

24. It's my impression that in recent years, either airports are more willing to close runways

due to high wind, and/or they are getting more days with high wind. I'm thinking of Newark/New York especially. I'm not complaining either. I'd rather be late any day than take the chance of crashing.

[Hawkowl]

26. Due to controller shortage

I think the tendency to close runways is due to a TREMENDOUS shortage of air traffic controllers. The Bush administration reduced pay and benefits by some ridiculous percentage (30-50%) and the FAA can no longer retain and recruit controllers. So for example, at an airport like Denver, a new huge airport with six runway strips that were designed to be used simultaneously, we often use only two or three, simply because there aren't enough controllers to handle the flow of aircraft.

At least that is what the controllers tell me.

[hootinholler]

28. Not just that last...

ATC have been operating without contract under terms dictated by the Fed.

The big influx of ATC people when RayGun fired them? Well they're retiring now.

Double republic induced whammy.

-Hoot

[RamboLiberal]

27. Question about the boots

Ran in to this - don't know the author's expertise. But NTSB did say the boot deicing was turned on 11 minutes in to the flight if I remember correctly? Could this have been too early if the below is correct?

So the system most turboprops - including the Dash 8 and ATR series - use is the rubber de-icing "boot". These black "boots" that wrap around the leading edges of all the lift-producing surfaces work by employing engine bleed air as economically as possible. The de-icing system provides pulses of pneumatic energy to cause the boots to inflate slightly, then deflate, then re-inflate and so on. This is intended to break off ice that has already formed on the leading edges.

Yes, you did read that correctly: the ice has to form first and then be broken off, and this is called de-icing, not anti-icing.

If the system is operated before ice starts to build up, there is a danger that, when buildup begins, the pulsed inflations of the boot will cause a gap to form between the ice buildup and the deflated boot, so when it re-inflates it has little effect on the ice that can quickly wrap around the entire leading edge to points beyond the boot itself.

So although the system works well if used just at the right time, it can have reduced effectiveness if used at the wrong time. Knowing the difference between the right time and the wrong time is difficult because we are talking about weather here, and no two sets of conditions are ever the same.

http://www.flightglobal.com/blogs/learmount/2009/02/colgan-3407-icing-and-turbopro.html

[DemoTex]

31. I've got a little about boots in this post (inc. pics):

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=389x5072543

[RamboLiberal]

33. Thanks DemoTex I'll be sure to read it n/t

[RamboLiberal]

30. 2005 Incident in Canada earlier version of this aircraft model

-----

An incident in Canada aboard an earlier version of the same aircraft could hold clues to Thursday's crash. A Provincial Airlines Limited flight slowed to an unsafe speed in icy conditions and plunged 4,200 feet before the pilots recovered May 27, 2005.

The Canadian Transportation Safety Board said the plane lost lift in its wings — the same type of problem that occurred in Thursday's crash.

Canadian investigators found that the pilots exacerbated the condition because they had not been trained to recognize that wings can lose lift at higher speeds in icing conditions. Instead of pushing the nose down to gain speed, the captain "continued to try to lift the nose of the aircraft," investigators said. The pilots eventually recovered and landed safely.

The NTSB has not said whether pilots pulled the nose up in Thursday's crash.

http://www.usatoday.com/news/nation/2009-02-16-crash_N.htm?loc=interstitialskip

[conscious evolution]

35. Looking forward to your anti-ice post.

When I was a student at Embry-Riddle I took a class on fluid dynamics and one on basic aerodynamics.
The labs for those classes had time in wind tunnels.One of our labs was on what icing does to the cambor of an air-foil and how it affects the airflow. Pretty eye-opening.It does not take much to screw up the air pressure differential betwwen the top and bottom of the wing.

I kinda wish I had kept a copy of that lab report.Oh well.

[RamboLiberal]

36. DemoTex has it posted at

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=389x5072543

I just read it and its very informative.

[DemoTex]

37. The not-so-short anti-ice/de-ice primer is here:

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=389x5072543

Yep. Even a little frost on top of a Piper J-3 Cub's fat wings plays havoc with the "Bernoulli's Principle" lift. The Newton's Law lift, which predicts that a barn door will act as a wing and fly if enough power is available, can handle a bit more ice. Air Florida 90 ("Palm 90," DCA Jan. 13, 1982) could have flown even with the snow and ice on the wings if max thrust had been achieved. Sad story, that.