Aviation / History

The Graves of Buffalo: Five Years after the Crash

Five years ago yesterday, on February 12, 2009, Continental Connection (CO) Flight 3407 from Newark International Airport (EWR) to Buffalo International Airport (BUF) crashed into a house in Clarence Center, New York.  The flight, operated by Colgan Air, killed one individual on the ground and all of the occupants on board the Bombardier DHC-8-402 Q400 (herein referred to as Q400).  The deceased 47-year old captain of CO 3407, Marvin Renslow (often erroneously referred to as “the pilot” instead of the proper regulatory term pilot-in-command (PIC)), to this day receives significant scorn for his inability to prevent his and 49 other deaths and the destruction of N200WQ, the aircraft he commanded:

Continental Connections Flight 3407 operated by Colgan Air left Newark International Airport on Feb. 12, 2009, with a fatigued pilot and co-pilot who failed to compensate for loss of speed caused by ice on the plane’s wings. When an indicator alerted the pilots the aircraft was going into an aerodynamic stall as it approached Buffalo Niagara International Airport, they didn’t know how to respond.

All 49 people on board and one person on the ground died when the plane crashed into a house in the Buffalo suburb of Clarence Center and set it ablaze.

Unsurprisingly, USA Today is editorializing a bit:

In its final report on the accident, NTSB said that the captain caused the airplane to stall by pulling on his control column when the stick shaker activated at an artificially high airspeed— a reaction that was consistent with “startle and confusion” rather than with his training.

The report said that factors contributing to the accident were “the flight crew’s failure to monitor airspeed in relation to the rising position of the low-speed cue [on their primary flight displays], the flight crew’s failure to adhere to sterile cockpit procedures, the captain’s failure to effectively manage the flight, and Colgan Air’s inadequate procedures for airspeed selection and management during approaches in icing conditions.” 

Fatigue also was a likely factor, but investigators could not determine conclusively the extent to which the pilots were impaired by fatigue or how it might have contributed to their “performance deficiencies” during the flight, the report said.

Coming from an organization entitled Flight Safety, it has to be expert analysis, right?  Unfortunately, looking back a half decade puts this tragedy in stark relief: air carrier stall recovery procedures were extremely dangerous up until very recently, and the Q400 crash was the almost inevitable result from this deficiency.

Who Caused this Crash?

Any airplane crashing to Earth attracts governmental investigators, specifically by the Department of Transportation’s National Transportation Safety Board (NTSB) in the United States.  Tasked with determining the probable cause of all civil aviation accidents within American jurisdiction, the NTSB’s reports invariably direct a large share of civil litigation in the wake of large-scale loss of life and property destruction.  Corporations with deep pockets have a vested interest in blaming the individual operators of the vehicles involved in such accidents, deflecting responsibility (and more importantly civil judgments) onto the estates of the deceased. 

As a result, overwhelming pressure was directed at two individuals that could not speak for themselves, Captain Marvin Renslow and First Officer Rebecca Shaw in the early-2009 rush to judgment.  But weren’t the pilots responsible?  Who else was in control of N200WQ, the Q400 that crashed and burned on Abraham Lincoln’s 200th birthday?

No one physically.  To a certain extent, those that still live can find fault in two of the victims that lost their lives too soon.  Renslow and Shaw were the only two human beings on that airliner that had their destinies literally in their own hands; the other 47 (and to a certain extent the victim on the ground) had the misfortune of being along for the ride that night.  The emotional need to ascertain who’s responsible is visceral, yet understandable.  But did the pilots harbor any malice towards the others that were about to perish with them?  Almost certainly not—no evidence has ever appeared that either pilot was suicidal.  Renslow and Shaw didn’t deliberately crash N200WQ; they lost control and their Q400 crashed.  In the case of CO 3407 the who is immaterial—the what (caused the Q400 to crash) and why (couldn’t the pilots prevent the Q400 from crashing) are the relevant questions.

Unrecovered Stall

An aircraft wing stalls when it exceeds a certain angle-of-attack (AOA).  While aviation concepts might seem jargon-filled to those not initiated into plane-speak, this concept is rather simple:

https://i1.wp.com/www.langleyflyingschool.com/Images/CPL%20Aerodynamics%20and%20Theory%20of%20Flight%20Part%201/Angle%20of%20Attack.gif

In essence, an aircraft wing can be “pitched” upward a certain number of degrees relative to the air flowing around the wing before the air no longer flows smoothly and “separates”…

 https://i1.wp.com/www.formula1-dictionary.net/Images/stall.gif

…leading to a stalled wing.  This is also known as the “critical angle of attack,” as a wing will always stall after exceeding a specific value (say an angle of 12° for the Q400).  Recovering from this undesirable (and dangerous) aircraft condition requires one action of the pilot flying the aircraft: reduce the angle of attack.  Student pilots have the stall recovery technique “lower the nose, apply full throttle”  drilled into their skulls constantly by certified flight instructors from day one.  This technique also includes leveling the wings, but that contributes more towards recovering aircraft performance than actually breaking the stall.  Rather simple, isn’t it?  So why didn’t Renslow, the pilot flying (PF, Shaw was the pilot monitoring, or PM that night) reduce N200WQ’s angle of attack?

The NTSB indicates Renslow added power but pitched up:

At 2216:27.4, the CVR recorded a sound similar to the stick shaker. (The stick shaker warns a pilot of an impending wing aerodynamic stall through vibrations on the control column, providing tactile and aural cues.) The CVR also recorded a sound similar to the autopilot disconnect horn, which repeated until the end of the recording. FDR data showed that, when the autopilot disengaged, the airplane was at an airspeed of 131 knots. FDR data showed that the control columns moved aft at 2216:27.8 and that the engine power levers were advanced to about 70° (rating detent was 80°) 1 second later.  The CVR then recorded a sound similar to increased engine power, and FDR data showed that engine power had increased to about 75 percent torque.

I immediately became suspicious when I noticed the NTSB believes Renslow began pitching up 0.4 seconds after stick shaker activation.  That’s an awfully rapid response to both an unplanned autopilot disconnection/and unexpected stick shaker activation.  Either event is jarring individually, let alone occurring simultaneously.  Reaching out and instantly yanking back on the yoke seems out of place unless the pilot in question was flying fighters or stunt aircraft.  The only semi-plausible explanation I’ve ever read for CO 3407’s captain to react in this manner is Renslow might have mistakenly believed the Q400 was experiencing windshear.  However, I find this unconvincing on account that establishing the aircraft attitude to escape windshear almost instantly after stick shaker activation without first informing Shaw of what he was doing sounds like the hallmark of a impulsive individualist.  The NTSB report does not depict Renslow as being brazenly reckless:

The check airman who conducted the captain’s Q400 simulator training and line-oriented flight training characterized the captain’s decision-making abilities as very good. The check airman stated that the captain, when receiving unusual attitude training in the simulator, had somewhat overcontrolled the roll axis but had progressed during his subsequent simulator experience. The check airman who provided the captain with his IOE described the captain’s performance as good and indicated that his greatest strength was being methodical and meticulous.

The NTSB addresses these concerns by theorizing Renslow’s hands were on the yoke the entire time…

The aft control column input occurred within 1 second of the stick shaker activation, which suggested that the captain’s hands were close to or resting on the control column. However, it was not possible to determine whether the captain’s hands were lightly placed on the control wheel before the onset of the stick shaker and the initial aft input was the result of a rough grab in response to being startled by the activation of the stick shaker.

…a theory that leaves me somewhat incredulous due to the fact that neither Renslow nor Shaw managed to silence the autopilot disconnect horn:

At 2216:27.4, the CVR recorded a sound similar to the stick shaker. (The stick shaker warns a pilot of an impending wing aerodynamic stall through vibrations on the control column, providing tactile and aural cues.) The CVR also recorded a sound similar to the autopilot disconnect horn, which repeated until the end of the recording.

The autopilot disconnect horn can be instantly silenced by clicking the red button as seen in this image of a Q400 yoke:

https://i0.wp.com/xsimreviews.com/wp-content/uploads/2012/10/Dash8Q400_pixal-panel.jpg

How much effort does it take to click that red button; a button that would have had Renslow’s  index finger and thumb resting above and below it according to the NTSB report?  How did Renslow and Shaw resist the urge to silence an annoying warning that in most transport-category aircraft chants “autopilot, autopilot, autopilot, autopilot, autopilot…” endlessly?  The NTSB seems certain that Renslow gripped the yoke firmly as…

FDR data also showed that, while engine power was increasing, the airplane pitched up; rolled to the left, reaching a roll angle of 45° left wing down; and then rolled to the right. As the airplane rolled to the right through wings level, the stick pusher activated (about 2216:34), and flaps 0 was selected. (The Q400 stick pusher applies an airplane-nose-down control column input to decrease the wing angle-of-attack [AOA] after an aerodynamic stall.) About 2216:37, the first officer told the captain that she had put the flaps up. FDR data confirmed that the flaps had begun to retract by 2216:38; at that time, the airplane’s airspeed was about 100 knots. FDR data also showed that the roll angle reached 105° right wing down before the airplane began to roll back to the left and the stick pusher activated a second time (about 2216:40). At the time, the airplane’s pitch angle was -1°.

…all 49 occupants on N200WQ were tossed about by the wild oscillations of the out-of-control Q400.  Really?  Was Renslow manhandling the controls, exacerbating the massive roll oscillations or was he merely having his head whipped in all directions and suffering from the centrifugal forces?

About 2216:42, the CVR recorded the captain making a grunting sound. FDR data showed that the roll angle had reached about 35° left wing down before the airplane began to roll again to the right. Afterward, the first officer asked whether she should put the landing gear up, and the captain stated “gear up” and an expletive. The airplane’s pitch and roll angles had reached about 25° airplane nose down and 100° right wing down, respectively, when the airplane entered a steep descent. The stick pusher activated a third time (about 2216:50). FDR data showed that the flaps were fully retracted about 2216:52. About the same time, the CVR recorded the captain stating, “we’re down,” and a sound of a thump.

So, what is missing, what caused the steep pitch-up moment less than a half second after autopilot disconnection?  

There is the fact that N200WQ was not trimmed for level flight should the throttles be advanced forward:

[B]ecause the autopilot altitude hold mode was engaged when the airplane leveled off at 2,300 feet, the autopilot continued to add nose-up pitch trim to maintain altitude as the airspeed slowed. During the time that the low-speed cue was in view, the airplane’s pitch trim increased from 1° to 7° nose up, and the pitch attitude of the airplane increased from 3° to 9° nose up.

I would have to argue that 7° nose up trim made the Q400 prone to experience a sudden pitch-up moment upon stick shaker activation/autopilot deactivation:

CVR and FDR data indicated that, when the stick shaker activated, the autopilot disconnected automatically. The captain responded by applying a 37-pound pull force to the control column, which resulted in an airplane-nose-up elevator deflection, and adding power. In response to the aft control column movement, the AOA increased to 13°, pitch attitude increased to about 18°, load factor increased from 1.0 to about 1.4 Gs, and airspeed slowed to 125 knots. In addition, the speed at which a stall would occur increased.  The airflow over the wing separated as the stall AOA was exceeded, leading to an aerodynamic stall and a left-wing-down roll that eventually reached 45°, despite opposing flight control inputs. Thus, the NTSB concludes that the captain’s inappropriate aft control column inputs in response to the stick shaker caused the airplane’s wing to stall.

Am I really arguing that the mechanics of aircraft automation played a role in this tragedy–theorizing that the initial stall might have been induced by the excessive trim setting commanded by the autopilot?  Yes, I am.  The NTSB tries to absolve the undesirable trim, arguing…

CVR and FDR data showed that the captain made an initial aft control column input after stick shaker onset and before the application of power. The stick forces at the time of autopilot disconnect were likely less than 2 pounds and would not account for his control input, which was abrupt and inappropriate.

I’m sorry, but “likely less than 2 pounds” sounds weasely to me.  The entire NTSB report spends inordinate amounts of space mentioning improvements Colgan has made after the accident, as if the changes weren’t induced by the crash at Clarence Center.  The normally-professional NTSB even makes a galling, spurious comparison:

On March 10, 2009, a Colgan Q400 airplane, N188WQ, was en route from EWR to Burlington International Airport (BTV), South Burlington, Vermont, during night VMC. While descending into BTV, the stick shaker activated, a recovery followed, and the airplane landed at BTV without further incident. After the event, the NTSB interviewed the flight crew and the check airman who was administering the captain’s 1-year line check at the time.

The captain reported that, before the event, she had been manually flying the airplane, and her attention had been mostly focused outside of the airplane.

What do I find so galling about this?  The utter banality of the event.  The stick shaker activated during manual flight—so what?  In the Burlington incident, the recovery wasn’t even noteworthy:

The captain stated that the last airspeed she noticed before the event was about 140 knots and that the stick shaker had activated at an airspeed of about 135 knots and an altitude of about 1,800 feet. The first officer reported that, while performing the before landing checklist, he heard a noise, looked up, and saw that the numbers on the IAS display had turned red. The first officer further reported that he immediately called out “airspeed” and that the captain (the flying pilot) immediately responded by increasing power. The captain reported that she had lowered the airplane’s nose and added full engine power (but did not reach the detent) in response. The first officer reported that he did not notice any significant change in the airplane’s pitch when the captain applied full power, describing the airplane as being in a “gentle descent” at the time.

Again, the stick shaker activated during manual flight.  No massive pitch-up moment was induced, as the elevator trim wasn’t excessive.  Stalls are a whole different animal when induced during autoflight (autopilot/autothrottles), according to Transport Canada (the Canadian equivalent to the FAA and the regulatory agency overseeing Bombardier, the manufacturer of the Q400):

The following items should be emphasized during manoeuvre-based training:

(A) How changes to factors such as weight, centre of gravity, G loading, bank angle, altitude and icing affect the handling characteristics and stall speeds of the aeroplane,

(B) Abrupt pitch up and trim change commonly associated when the autopilot unexpectedly disconnects during a stall event. This dramatic pitch and trim change typically represents an unexpected physical challenge to the pilot when trying to reduce AOA. In some aeroplanes, this may be exacerbated by an additional pitch up when the pilot increases thrust during stall recovery

What Procedures Caused This Crash?

This is the question the author feels that all accident investigators should ask first and foremost.  Naturally, questioning the procedures of powerful businesses and governmental organizations is not a common occurrence in this country.  Nevertheless, the NTSB really should have recognized that this is not at all appropriate:

Stall profile Entry into stall During stall Exit from stall
Landing stall 180 knots and minimumaltitude of 5,000 feet AGL [(Above Ground Level)] with flaps at 35°, gear down, and power at flight idle  PF maintains altitude andHeading PF calls “stall,” advancespower to rating detent, andcalls “check power, flaps 15” PM calls “positive rate” PF calls “gear up.” 

PM calls “Vfri”

 

PF calls “flaps 0”

 

PF adjusts power tomaintain 180 knots 

Maintain altitude.  Essentially, air carrier training emphasized “powering out” of a stall—maintaining (or possibly increasing) pitch attitude so as to avoid any altitude loss or gain.  This was industry-standard in 2009, and today is rightly considered borderline psychotic:

(D) Reducing AOA is the proper way to recover from a stall event. Pilots must accept that reducing the aeroplane’s AOA may often result in altitude loss. The amount of altitude loss will be affected by the aeroplane’s operational environment (e.g., entry altitude, aeroplane weight, density altitude, bank angle, aeroplane configuration, etc.). At high altitudes, stall recovery may require thousands of feet,

(E) Differences between high and low altitude stalls; pitch rate and sensitivity of flight controls, thrust available for recovery, and altitude loss,

(F) The need to apply nose down elevator inputs to reduce AOA when stalled at excessively low pitch attitudes and/or at large bank angles, including bank angles exceeding ninety degrees,

(G) Noises associated with stick shakers and autopilot disconnect aural alerts or alarms can cause confusion in the cockpit,

(H) Understanding that early recognition and return of the aeroplane to a controlled and safe state are the most important factors in recovering from stall events. Only after recovering to a safe manoeuvring speed and AOA should the pilot focus on establishing an assigned heading, altitude, and airspeed

That’s right—Transport Canada essentially threw stall recovery heading and altitude control requirements out the window (an eminently sensible approach, given that heading and altitude aren’t much help if the plane slams into a house on final to Runway 23 at BUF).  Current Q400 stall recovery procedures seem to have been copied-and pasted from the Canadian regulatory agency:

Stall Warning Recovery
The flight crew shall use all energy resources available, including altitude, as appropriate, to prevent or recover from a stall condition. HGS guidance should be used, if available.
 
Stall Recovery Summary
At first sign of stall:
1. Increase airspeed by:
• Reducing pitch (altitude permitting)
• Adding power
2. Roll wings level.
3. Increase airspeed out of stall condition ≥ Low-speed Cue + 10 knots.
4. Recover to Missed Approach or appropriate flight regime. CAUTION:
Be prepared to manage control forces for required pitch inputs.
• An actual stall results in a nose-down pitch, especially if the stick pusher activates (70 lbs). Too much forward movement of the control column can produce an excessive nose-down attitude.
• As power and airspeed are increased, a pitch-up tendency may be induced.
• G/A is pressed to set a maximum pitch limit during recovery.
Reduce pitch below the Flight Director as necessary during recovery.

Before this begins to sound too pro-Great White North, I would be remiss to ignore AC-120-109:

Emphasis Items.

The following items should be emphasized during maneuver-based training:

(a) How changes to factors such as weight, G loading, bank angle, altitude and icing affect the handling characteristics and stall speeds of the airplane.

(b) Abrupt pitch up and trim change commonly associated when the autopilot unexpectedly disconnects during a stall event. This dramatic pitch and trim change typically represents an unexpected physical challenge to the pilot when trying to reduce AOA. In some airplanes, this may be exacerbated by an additional pitch up when the pilot increases thrust during stall recovery.

(c) Stall warnings for the specific airplane.

(d) Reducing AOA is the proper way to recover from a stall event. Pilots must accept that reducing the airplane’s AOA may often result in altitude loss. The amount of altitude loss will be affected by the airplane’s operational environment (e.g., entry altitude, airplane weight, density altitude, bank angle, airplane configuration, etc.).  At high altitudes, stall recovery may require thousands of feet.

(e) Noises associated with stick shakers and autopilot disconnect alarms can cause confusion in the cockpit.

(f) Understanding that early recognition and return of the airplane to a controlled and safe state are the most important factors in surviving stall events (only after recovering to a safe maneuvering speed and AOA should the pilot focus on establishing an assigned heading, altitude, and airspeed).

(g) Differences between high and low altitude stalls; pitch rate and sensitivity of flight controls, thrust available for recovery, and altitude loss.

This FAA Advisory Circular predates the Transport Canada document by a year.  Yet AC 120-109 is from August 2012—three and a half years after the Colgan crash.  I’m going to go out on a limb, and postulate the complete revamping of air carrier stall recovery procedures (more of a back to basics—after all, “lower the nose” is not news to pilots) wasn’t related to the investigation of CO 3407.  The NTSB did not argue that stall recovery procedures should be completely rewritten as a result of the February 2009 crash, though the NTSB was clearly aware of the problem:

Also, on July 29, 1997, the NTSB issued Safety Recommendation A-97-47 as a result of the ABX Air accident in Narrows, Virginia.  Safety Recommendation A-97-47 asked the FAA to do the following:

Evaluate the data available on the stall characteristics of airplanes used in air carrier service and, if appropriate, require the manufacturers and operators of flight simulators used in air carrier pilot training to improve the fidelity of these simulators in reproducing the stall characteristics of the airplanes they represent to the maximum extent that is practical; then add training in recovery from stalls with pitch attitudes at or below the horizon to the special events training programs of air carriers.

Not exactly “lower the nose,” but the NTSB in 1997 came extremely close with “pitch attitudes at or below the horizon.”  The FAA in response generated the inadequate stall recovery standard in effect from 1999 to 2012:

The FAA further stated that, to address the recommendation, it would revise the practical test standards to require pilots to adjust pitch, bank, and power to recover from an approach to stall and would add a note indicating, in part, that airspeed and/or altitude loss is critical at low altitudes and must be kept to an absolute minimum.

 Moreover, the NTSB had eventually given up altogether on pursuing improvements in stall recovery training:

On November 19, 1999, the NTSB stated that the ability of simulators to faithfully replicate an airplane’s actions in some stall and stall recovery regimes could be improved. The NTSB noted that generic simulator modules that were developed for some highly variable events have provided useful and necessary training for pilots. The NTSB pointed out, as an example, microburst and windshear simulator training, which provides realistic and effective training to pilots on specific models, even though an actual encounter is likely to be significantly different. The NTSB stated that it was disappointed that the FAA did not make changes to improve the fidelity of simulators in reproducing stall characteristics to the maximum extent feasible. The NTSB added that airline pilots need to be afforded this type of training so that they are fully prepared to recover stalled aircraft. As a result, Safety Recommendation A-97-47 was classified “Closed—Unacceptable Action.”

 The Hidden Victims

Colgan Air threw its dead crewmembers under the bus, having the audacity to argue Renslow and Shaw were alone responsible for the “loss of situational awareness and failure to follow Colgan Air training and procedures.”  Considering Colgan couldn’t be bothered to properly train its flight attendants to use the fire extinguishers on its aircraft or schedule its crews enough rest, I guess Colgan’s “training and procedures” were subjective.  I’ve already mentioned that Colgan’s stall recovery procedures bordered on insane, a “possible misinterpretation” of FAA regulations:

•Reduction of AOA is the most important response when confronted with a stall event.

•Evaluation criteria for a recovery from a stall or approach-to-stall that does not mandate a predetermined value for altitude loss and should consider the multitude of external and internal variables which affect the recovery altitude. (Reference: Safety Alerts for Operators (SAFO) 10012, Possible Misinterpretation of the Practical Test Standards (PTS) Language “Minimal Loss of Altitude”)

 The Federal Aviation Administration has also been avoiding responsibility in regards to the Clarence Center crash, as the FAA initiated and signed off on the dangerous air carrier stall recovery procedures for 13 years—where exactly was “minimal loss of altitude” misinterpreted given that in the new FAA and Transport Canada Advisory Circulars there are warnings that stalls may require trading thousands of feet of altitude to recover the airspeed performance necessary to break the stall (albeit this scenario is only likely in the event of a stall at high altitude)?

Two human beings were victimized beyond having the great misfortune to die horribly as their cockpit slammed into the ground.  These two pilots will never be heralded as heroes—after all, their failure to recognize that the “Increase” button required a Vref 20 knots faster than calculated did put their aircraft into an undesirable state.  They failed to reduce N200WQ’s angle of attack and save 48 lives along with their own.

But Marvin Renslow and Rebecca Shaw have been vilified mercilessly for making errors that any pilot could make—forgetting the position of a switch led to the stick shaker activation far above stall speed (am I alone in thinking this is a rather glaring design flaw in the Q400)?  Vilified for experiencing a major pitch upset, a situation that planes in autoflight are prone to experiencing that, at the time of the deadly crash, was understood by neither airlines nor regulators.  Vilified for not following their training when Colgan’s training regime did not account for serious real-world threats such as major pitching moments associated with stick shaker activation coupled with sudden autopilot disconnect.  Vilified for failing to lower the angle of attack during the real-world stall of the Q400 they were flying when their employer’s stall recovery procedure emphasized maintaining altitude–a procedure that in many cases would necessitate increasing the plane’s pitch angle.  Vilified for failing to accomplish a stall recovery procedure that made no sense.

What can anyone say to these two victims, whose victimization led to the deaths of 50 individuals on that cold February night five years ago?  Only this:

 http://assets.nydailynews.com/polopoly_fs/1.408909!/img/httpImage/image.jpg_gen/derivatives/landscape_635/alg-pilots-jpg.jpg

Sorry—you deserved better.

Advertisements

6 thoughts on “The Graves of Buffalo: Five Years after the Crash

  1. Pingback: The Procedures Factor | In The Corner, Mumbling and Drooling

  2. Pingback: Five Years After the Fall: The Atlantic Angle of Attack | In The Corner, Mumbling and Drooling

  3. Pingback: Aeronautical Common Sense | In The Corner, Mumbling and Drooling

  4. Pingback: Navigating Aeronautical Safety–Part 3 | In The Corner, Mumbling and Drooling

  5. Pingback: Six Years Since the Bicentennial | In The Corner, Mumbling and Drooling

  6. Pingback: Aviation Investigation Snow Job | In The Corner, Mumbling and Drooling

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s