on the Buffalo crash and stick-pushers  -opinion and extracts below

Please post your thoughts on Pprune or email to james.smith@iinet.net.au

Stick-pushers have a chequered history that I've only briefly covered below. They aren't very pilot-friendly at all - as a safety device. A stick-pusher is not required for airworthiness certification of a transport category aircraft. Like the "tail-feathers" of the Beech 1900D (Charlotte NC crash), they are usually added to a non-swept-wing aircraft as "a facile solution" - and only when a model is extended from its basic model. The 727, 737,747, DC9, DC8 and some ATR42's don't have one but the EMB145, ATR72, Canadair CL65 and SAAB340A do (why is that?). However my overall impression is that the Q400, as configured for stall warnings, is a dangerous beastie (note the 70% pilot response [to stick-pusher] error rate in the box way below - pretty much proving my case).

 

During a rapid deceleration the stick-shaker transitions seamlessly into stick-pusher, and about the worst thing you can do during any sudden pusher activation is to oppose it and pull the control column aft, raising the nose and preventing the airplane from regaining an orderly airflow around the wings. But wrong as that action would be, it's reasonable to imagine it happening if the airplane is already close to the ground and decelerating rapidly (stick-shaker/stick-pusher occurring simultaneously) i.e. the nose drops ominously of its own accord, the lights of the city suddenly fill the windscreen.... aerodynamic logic says to add max power and let the plane descend and accelerate; but logic can't rule and panic does - because the visual outside picture, coupled to the propensity to "go-round" as an escape maneuver, says to instinctively oppose the uncommanded nose-drop. What's needed is a gradual onset stall warning such as my proposed progressive aural alert (see final box below). We need to look further into this anomalous and inherently dangerous pusher device on plank-winged airplanes. Pilots would rarely encounter a stick-pusher in flight. But if they do, there are four things that might happen:

a.  A Buffalo style Colgan Flt3407 replay (pilot automatically countering the stick-push with an attempted go-round), the stall entry being then exacerbated by the copilot raising flap - for that go-round.

 

b.  A presumption of a false actuation (based upon other operating parameters) - leading to a pilot deactivating it.

 

c.  An incorrect presumption of a false actuation leading to a Buffalo style Colgan Flt3407 replay

 

d.  A close-call recovery from a close encounter with a low-level stall

A stick pusher is a device installed in some fixed-wing aircraft to prevent the aircraft from entering an aerodynamic stall. Some large swept-wing aircraft display poor post-stall handling characteristics or are vulnerable to deep stall. To prevent such an aircraft approaching the stall the aircraft designer may install a hydraulic or electro-mechanical device that pushes forward on the elevator control system whenever the aircraft’s angle of attack reaches the pre-determined value, and then ceases to push when the angle of attack falls sufficiently. A system for this purpose is known as a stick pusher (see link and link).

The safety requirements applicable to fixed-wing aircraft in the transport category, and also to many military aircraft, are very demanding in the area of pre-stall handling qualities and stall recovery. Some of these aircraft are unable to comply with these safety requirements relying solely on the natural aerodynamic qualities of the aircraft. In order to comply with the requirements aircraft designers may install a system that will constantly monitor the critical parameters and will automatically activate to reduce the angle of attack when necessary to avoid a stall. The critical parameters include the angle of attack, airspeed, wing flap setting and load factor. Action by the pilot is not required to recognize the problem or react to it. (but what if he does?)

Aircraft designers who install stick pushers recognize that there is the risk that a stick pusher may activate erroneously when not required to do so. The designer must make provision for the flight crew to deal with unwanted activation of a stick pusher. In some aircraft equipped with stick pushers, the stick pusher can be overpowered by the pilot. In other aircraft, the stick pusher system can be manually disabled by the pilot.

Stick-pushers should not be confused with stick shakers. A stick-shaker is a stall-warning device whereas a stick-pusher is a stall avoidance device.

 

There are many lead-up scenario events that can ultimately lead to an accident. However these type introductory scenarios happen many times a day all over the world for a multitude of reasons - and yet most don't lead to accidents. But some inevitably do - and they make the headlines and necessarily lead to a distracting indepth hindsightful examination of all those "lead-up" preliminary events. The build-up prelude (fatigue, sleep deprivation, training records, commuting to work, safety training, check-ride performance etc) then tends to detract from (and overshadow) that vital final "clincher" event's importance - as the final arbiter (i.e. to be or not to be? ....an accident or mere unreported incident?).

 

The point that I'm making is that the stick-pusher is an inappropriate alarmist device that intervenes suddenly and unexpectedly in the flight control circuit and therefore can be expected to precipitate a defensive reaction (i.e. an incorrect contrary response - which is exactly what happened in the Buffalo Dash 8). If the rate of slow-down is rapid (as in an approach-configured level-off and failure to manually throttle up), the stick-shaker and stick-pusher will happen almost coincidentally.  An alerting device that cuts in early (based on low power and rate of increase of AoA), doesn't alarm and has a built-in instinctive and familiar solution (add power and ease off back-pressure to lower the aural pitch and volume of a background audible tone - thereby avoiding an unrecoverable stall at low-level).

A further point is "what's preferable?" A loud blaring autopilot disconnected warning horn that cooks off at the stall [as the A/P disconnects automatically] and continues distracting the crew until the crash (see Trident crash and many others) - or a variable pitch (and volume) alerting system that you can make "go away" by taking the instinctively correct action?

 

Looking at that important question of "familiarity"..... reflect that an aural AoA alert would often be heard inflight at varying low pitch and low volume and so would be familiar to the pilots operating a type (both in the aircraft and the simulator - as would the stick-shaker with which it would work in late consonance). However the stick-pusher is a last second (post-stick-shaker) intervention, a "one-shot" like an engine fire-extinguisher button that's very rarely pressed. However the difference there is that the stick-pusher is an alien control input that can be instinctively overridden by a pilot - and is likely to be, based upon his unfamiliarity and very minimal exposure (if ever) to its actuation. You can flog the theory of something but sudden unalerted exposure to it inflight is a different beast altogether.

 

I'm of the opinion that the BEA Trident accident at Staines (stick-pusher being droop retraction induced) and at Buffalo (lack of an autothrottle to preserve speed at descent level-off) have much in common, i.e. pilot surprise and an instinctive contrary response exactly opposite to what was required to save the day.

 

Should we now shake up the industry, manufacturers and FAA/NTSB etc) with an invitation to disprove Buffalo's Dash8 downing as being a straight human factors system-induced accident?

In the final seconds of the flight, two pieces of safety equipment activated - a stick shaker to alert the crew their plane was nearing a stall and a stick pusher that points a plane's nose down so it can recover speed, investigators said. The correct response to both situations would have been to push forward on the control column to increase speed, they said.

But Renslow pulled back on the stick shaker, investigators said. When the plane stalled and the pusher activated, and then reactivated two more times, Renslow again pulled back all three times.

Seventy percent of pilots who had experienced the stick-pusher activation in training responded by pulling back instead of pushing forward - the deadly opposite of the correct response - even though they knew ahead of time to expect a stall, investigators said.

The first officer, Rebecca Shaw, 24, should have stepped in to push the plane's nose down herself when Renslow responded improperly, but she may not have because she was a relatively inexperienced pilot, investigators said.

from link

All criticisms directed at the Flt 3407 pilot's actions with respect to the stick-pusher have revolved around nil exposure to it in training. I suspect that training to accommodate a sudden stick-pusher at low-level would be a conflicting or negative reinforcement of a pilot's innate instincts.

An example:

The Trident was the first aircraft in the world to be certificated with stick-pusher protection against the deep-stall characteristics of high-tailed aircraft, which had caused at least four fatal accidents.

Flight BE548 was a scheduled passenger service from London to Brussels. Start-up clearance was given at 15:39 for a scheduled departure time of 15:45. Push-back was not requested until 16:00 due to load re-adjustment. Clearance to taxi was given at 16:03. The HS-121 Trident taxied to runway 28R for takeoff. At 16:06:53 the crew reported ready for take-off. Takeoff clearance was given and at 16:08:30 the brakes were released.

The standard BEA practice for this particular flight involved a take-off with 20° flap, leading edge droop (wing leading-edge slats) extended and the engine thrust at settings below full power. After take-off, speed should be increased to the initial climb speed VNA (ie, take-off safety speed, V2 pIus 25 knots). The scheduled value of VNA for this flight was 177 knots Indicated Air Speed (IAS). At 90 seconds from brakes-off flaps are to be selected fully up and the engine thrust reduced to the noise abatement settings. At 3,000 feet climb power is to be set and then as the aircraft accelerates and reaches 225 knots the leading edge droops are retracted and the en route climb established. The minimum droop retraction speed is placarded by the lever and is well-known to all pilots.

The take-off was normal and at 42 seconds the aircraft rotated, leaving the runway 2 seconds later at 145 knots IAS. At 63 seconds the autopilot was engaged 355 feet above the runway at 170 knots IAS; the IAS speed lock was selected shortly thereafter. At 74 seconds the aircraft started a 20° banked turn to port towards the Epsom Non-Directional Beacon (NDB). At 83 seconds the captain reported 'Climbing as cleared'. He was then instructed to change frequency and contact London Air Traffic Control Centre.
At 93 seconds the noise-abatement procedure was initiated. On the assumption that the captain was the handling pilot, this would involve the second officer selecting the flaps fully up and operating the thrust levers to reduce power to the pre-calculated figure. At 100 seconds the captain called 'Passing 1500' and at 103 seconds the aircraft was cleared to climb to Flight Level 60. This message was acknowledged by the captain at 108 seconds with the terse call 'up to 60'. This was the last message received from the flight.
At second 114 when the airspeed was 162 knots and the altitude 1,772 feet, the droop lever was inadvertently selected up putting the aircraft into the area of the stall as the droop started to move. At second 116 the stick-pusher stall recovery device operated, causing the autopilot automatically to disengage and the nose of the aircraft to pitch down and the stick-push to cease as the incidence decreased. Since the elevator trim would stay at its position on autopilot disengagement which at that speed with the droop up would be nose-down - the incidence then increased causing a second stick-push at second 124 and a third at second 127. At second 128 the stall recovery system was manually inhibited by pulling the lever. The aircraft then pitched up rapidly, losing speed and height, entering very soon afterwards the true aerodynamic stall and then a deep stall from which at that height no recovery was possible. Impact was at second 150 in a field next to the A30 motorway .

PROBABLE CAUSE: Immediate causes were:
1) Failure by PIC to achieve and maintain adequate speed after noise-abatement procedures; 2) Droop-retraction 60kts below minimum speed.; 3) Failure to monitor speed error and to observe droop lever movement.; 3) Failure to diagnose reason for stick-pusher operation and warnings; 4) Operation of stall recovery override lever.

This above is an example of a swept-wing aircraft for which a stick-pusher was a vital piece of equipment. See bright yellow highlights. Did the stick-pusher system work towards saving this Trident or did it induce a surprised pilot reaction (unaware of copilot's premature droop retraction) that condemned it? Think "instinctive" (but damning) pilot response to stick-pusher intervention. Wasn't it similar at Buffalo?

You can see at this link to what extent all the hindsighting of the BEA accident went. BEA Trident crews were always suspicious of droop and stick-pushers for good cause (see "the Naples incident").

 In the Staines crash, after the first stick-push: "Captain Key pulled the nose up once more to reduce airspeed slightly to the required 175 knots (324 km/h) but this further stalled the aircraft.... and it entered a deep-stall"

The Inquiry's findings as to the causes of the accident, published in its report on 14 April 1973, were that the Captain failed to maintain the recommended airspeed; that the leading edge devices were retracted too early; that the crew failed to monitor airspeed and configuration; that the crew failed to recognise the reasons for the stall warnings and stick-pusher operation; and that the crew then wrongly disabled the stall recovery system.

 

And note also that a stick-pusher can be inherently dangerous...
Transport Canada records indicate that, for the CL-65, pusher activation results in a strong nose-down pitch that can not be readily arrested with normal pilot effort. With flaps 45 and landing gear down, the aircraft typically pitches down by a maximum 20 to 30 degrees in five seconds. The height loss depends on the recovery procedure but is in the order of 1000 feet.

from link

...... and in the Flt 3407 case: "The stick-pusher may have activated at a speed higher than normal because it added a margin of safety to account for icing conditions, investigators say".

Pinnacle Flt 3701 (Bombardier CRJ-600-200 crashed in Jefferson City)

The airplane was at 41,000 feet for about three minutes, during which time Capt. Rhodes left the cockpit for a brief time to get congratulatory soda pops.

The stick shaker activated, which disengaged the autopilot. The flight crew then pulled back the control column, increasing the angle of attack sufficiently to activate the stick pusher. In fact, the stick pusher was activated three times. As the stick pusher moved the control column forward, the airplane's pitch angle changed from 7 degrees nose up to 30 degrees nose down, followed by 30 degrees nose up pitch.

The stick pusher, which forcibly drops the nose, protects the engines from pressure drops and flame outs. Not in this case. During this time, the engine core rotation speed, or N2, began to decrease, and the engines flamed out (trying to maintain the cleared height led to a drop in airspeed and axial flow through the engines). The captain declared an emergency.  from link

 see also this link   757 incident

and susceptibility to AoA faults (link)

Stall protection is another example of a protection system that could have disastrous results if full pilot authority is not maintained. This basic protection scheme often involves the use of a stick pusher. Most modern aircraft that use stick pushers provide for the crew to manually deselect the system. Earlier designs do not always provide this capability. Without pilots having the authority to disable the system, crews were forced to hold excessive amounts of backpressure to counteract a malfunctioning system.

Obviously, stall warning and stall prevention systems are very important and aircraft that use stick pushers do so for stall warning and because of undesirable stall characteristics. The most extensive over-ride capability is provided by the Embraer EMB-145, where a single push button on the yoke disables or disengages the stick pusher, the auto-pilot, and the elevator trim system. The Canadair CRJ has a toggle switch next to the captain's knee that can be used to deselect the stick pusher. Since the pilot has the ultimate responsibility for the safe conduct of the flight, the ability to over-ride a malfunctioning system is of utmost importance. (link)

 

Relevant Reading

 NTSB's findings on the Colgan Air accident near Buffalo in February 2009



NTSB logoThe National Transportation Safety Board (NTSB) released a summary of its findings regarding the February, 2009 crash of a Colgan Air Bombardier DHC-8-400 near Buffalo, NY. The title of the press release that announced the findings read (in capital letters), CAPTAIN’S INAPPROPRIATE ACTIONS LED TO CRASH OF FLIGHT 3407 IN CLARENCE CENTER, NEW YORK, NTSB SAYS. Talk about cutting to the chase, right in the title!

Yesterday's report elaborated on the stark title of the press release, with this statement of probable cause:
The National Transportation Safety Board determines that the probable cause of this accident was the captain’s inappropriate response to the activation of the stick shaker, (note failure to discriminate between shaker and pusher - here and further below- highlit in yellow) which led to an aerodynamic stall from which the airplane did not recover.
Contributing to the accident were (1) the flight crew’s failure to monitor airspeed in relation to the rising position of the low-speed cue, (2) the flight crew’s failure to adhere to sterile cockpit procedures, (3) the captain’s failure to effectively manage the flight, and (4) Colgan Air’s inadequate procedures for airspeed selection and management during approaches in icing conditions.
The NTSB summary included a list of 46 individual conclusions. Among the findings:
  • The recovered components showed no evidence of any pre-impact structural, engine, or system failures, including no indications of any problems with the airplane’s ice protection system.
  • The air traffic controllers who were responsible for the flight during its approach to Buffalo-Niagara International Airport performed their duties properly and responded immediately and appropriately to the loss of radio and radar contact with the flight.
  • This accident was not survivable.
  • The captain’s inappropriate aft control column inputs in response to the stick shaker caused the airplane’s wing to stall.
  • The minimal aircraft performance degradation resulting from ice accumulation did not affect the flight crew’s ability to fly and control the airplane.
So, no support for those who theorized that icing was the cause of the accident. Instead, the NTSB seems to be saying that pilot error, independent of weather conditions, led to the tragic outcome.

Here's more:
  • Explicit cues associated with the impending stick shaker onset, including the decreasing margin between indicated airspeed and the low-speed cue, the airspeed trend vector pointing downward into the low-speed cue, the changing color of the numbers on the airplane’s indicated airspeed display, and the airplane’s excessive nose-up pitch attitude, were presented on the flight instruments with adequate time for the pilots to initiate corrective action, but neither pilot responded to the presence of these cues.
  • The reason the captain did not recognize the impending onset of the stick shaker could not be determined from the available evidence, but the first officer’s tasks at the time the low-speed cue was visible would have likely reduced opportunities for her timely recognition of the impending event; the failure of both pilots to detect this situation was the result of a significant breakdown in their monitoring responsibilities and workload management.
  • The flight crew did not consider the position of the reference speeds switch when the stick shaker activated.
  • The captain’s response to stick shaker activation should have been automatic, but his improper flight control inputs were inconsistent with his training and were instead consistent with startle and confusion.
  • The captain did not recognize the stick pusher’s action to decrease angle-of-attack as a proper step in a stall recovery, and his improper flight control inputs to override the stick pusher exacerbated the situation.
  • It is unlikely that the captain was deliberately attempting to perform a tailplane stall recovery.
  • No evidence indicated that the Q400 was susceptible to a tailplane stall.
  • Although the reasons the first officer retracted the flaps and suggested raising the gear could not be determined from the available information, these actions were inconsistent with company stall recovery procedures and training.
  • The Q400 airspeed indicator lacked low-speed awareness features, such as an amber band above the low-speed cue or airspeed indications that changed to amber as speed decrease toward the low-speed cue, that would have facilitated the flight crew’s detection of the developing low-speed situation.
  • An aural warning in advance of the stick shaker would have provided a redundant cue of the visual indication of the rising low-speed cue and might have elicited a timely response from the pilots before the onset of the stick shaker.
  • The captain’s failure to effectively manage the flight (1) enabled conversation that delayed checklist completion and conflicted with sterile cockpit procedures and (2) created an environment that impeded timely error detection.
These findings are uniformly damning of the captain and, to a lesser extent, the first officer. But then the NTSB report broadens the focus of responsibility to include Colgan Air, the pilots' employer:
  • The monitoring errors made by the accident flight crew demonstrate the continuing need for specific pilot training on active monitoring skills.
  • Colgan Air’s standard operating procedures at the time of the accident did not promote effective monitoring behavior.
  • Specific leadership training for upgrading captains would help standardize and reinforce the critical command authority skills needed by a pilot-in-command during air carrier operations.
  • Because of the continuing number of accidents involving a breakdown of sterile cockpit discipline, collaborative action by the Federal Aviation Administration and the aviation industry to promptly address this issue is warranted.
  • The flight crewmembers’ performance during the flight, including the captain’s deviations from standard operating procedures and the first officer’s failure to challenge these deviations, was not consistent with the crew resource management (CRM) training that they had received or the concepts in the Federal Aviation Administration’s CRM guidance.
Next, issues related to the role played by pilot fatigue and possible illness are addressed:
  • The pilots’ performance was likely impaired because of fatigue, but the extent of their impairment and the degree to which it contributed to the performance deficiencies that occurred during the flight cannot be conclusively determined.
  • All pilots, including those who commute to their home base of operations, have a personal responsibility to wisely manage their off-duty time and effectively use available rest periods so that they can arrive for work fit for duty; the accident pilots did not do so by using an inappropriate facility during their last rest period before the accident flight.
  • Colgan Air did not proactively address the pilot fatigue hazards associated with operations at a predominantly commuter base.
  • Operators have a responsibility to identify risks associated with commuting, implement strategies to mitigate these risks, and ensure that their commuting pilots are fit for duty.
  • The first officer’s illness symptoms did not likely affect her performance directly during the flight.
A number of the NTSB's findings addressed pilot qualifications and training deficiencies:
  • The captain had not established a good foundation of attitude instrument flying skills early in his career, and his continued weaknesses in basic aircraft control and instrument flying were not identified and adequately addressed.
  • Remedial training and additional oversight for pilots with training deficiencies and failures would help ensure that the pilots have mastered the necessary skills for safe flight.
  • Colgan Air’s electronic pilot training records did not contain sufficient detail for the company or its principal operations inspector to properly analyze the captain’s trend of unsatisfactory performance.
  • Notices of disapproval need to be considered along with other available information about pilot applicants so that air carriers can fully identify those pilots who have a history of unsatisfactory performance.
  • Colgan Air did not use all available sources of information on the flight crew’s qualifications and previous performance to determine the crew’s suitability for work at the company.
  • Colgan Air’s procedures and training at the time of the accident did not specifically require flight crews to cross-check the approach speed bug settings in relation to the reference speeds switch position; such awareness is important because a mismatch between the bugs and the switch could lead to an early stall warning.
  • The current air carrier approach-to-stall training did not fully prepare the flight crew for an unexpected stall in the Q400 and did not address the actions that are needed to recover from a fully developed stall.
  • The circumstances of this and other accidents in which pilots have responded incorrectly to the stick pusher demonstrate the continuing need to train pilots on the actions of the stick pusher and the airplane’s initial response to the pusher.
  • Pilots could have a better understanding of an airplane’s flight characteristics during the post-stall flight regime if realistic, fully developed stall models were incorporated into simulators that are approved for such training.
  • The inclusion of the National Aeronautics and Space Administration icing video in Colgan Air’s winter operations training may lead pilots to assume that a tailplane stall might be possible in the Q400, resulting in negative training.
The remaining findings address systemic oversight issues; flight operational quality assurance (FOQA) programs; personal portable electronic devices on the flight deck; the use of safety alerts for operators (SAFOs), and weather data, including information related to icing.

The NTSB summary also includes 25 new recommendations to the Federal Aviation Administration (FAA).

Here is the link to the synopsis of the NTSB report, where you can read all of the findings and safety recommendations arising from the investigation of the Colgan Air Flight 3407 accident: NTSB/AAR-10-01: Summary of Findings

 
The PC-12 crashed into a cemetery approximately 500 feet from the centerline of the runway it was trying to land on with its flaps, which are normally lowered for landing, still in the up position. Eyewitnesses stated that the airplane appeared too high to land on the runway and that the plane jerked sharply to the left and then "nose dived" into the ground... According to reports, the crew did not make any distress calls. These observations are consistent with a stall while maneuvering to land. A stall occurs when the aircraft is flying too slow such that the wings are no longer able to produce the necessary lift to maintain flight and the aircraft suddenly and rapidly loses altitude. The pilot may have been trying to maneuver the plane for landing and let the plane's speed get too slow resulting in the sudden, uncontrolled stall. If true, such a stall could have been caused by aircraft design issues, icing or other stall inducing factors, such as weight and the distribution of weight in the aircraft.

The PC-12 is known to have unusual and potentially dangerous stall characteristics. So much so, in fact, that when Pilatus Aircraft, Ltd. first sought to certify the aircraft for sale and use within the United States, the FAA required the incorporation of a "stick-pusher" system to help make the plane safer. The stick-pusher is designed to warn pilots of impending stalls and automatically lowers the nose of the aircraft when stall conditions are detected to increase the lift produced by the wings and keep the plane flying. The PC-12's stick-shaker and stick –pusher system may be implicated here for failing to prevent an aircraft stall. Within the past two years, the stick-pusher system has been the subject of two safety-related Airworthiness Directives issued by the FAA. In addition, Kreindler & Kreindler LLP is prosecuting a civil action against Pilatus for the crash of a PC-12 on March 26, 2005 in Bellefonte, Pennsylvania where it is claimed that the stick-pusher system failed to prevent a deadly stall.

The NTSB chairman recently identified similarities between the Butte, Montana crash and the crash of a Pilatus PC-12 aircraft in Bellefonte, Pennsylvania. Kreindler & Kreindler represents the family of one of the victims of that crash in lawsuits pending in Pennsylvania and New Hampshire. Based upon our continuing investigation, Kreindler & Kreindler believes that the Bellefonte crash was caused by a defectively designed stick pusher system that failed to meet FAA airworthiness requirements.

 
Summary:
The aircraft had a blocked pitot tube, causing an airspeed discrepancy, which was detected early during the takeoff roll. The commander decided to continue the takeoff and deal with the problem whilst airborne. After passing FL180 the crew selected the left Air Data switch to ALTN, believing this isolated the left Air Data Computer (ADC) from the Autopilot & Flight Director System (AFDS). Passing FL316, the VNAV mode became active and the Flight Management Computer’s (FMCs), which use the left ADC as their input of aircraft speed, sensed an overspeed condition and provided a pitch-up command to slow the aircraft. The co-pilot was concerned about the aircraft’s behaviour and, after several verbal prompts to the commander, pushed the control column forward. The commander, uncertain as to what was failing, believed that a stick-pusher had activated. He disengaged the automatics and lowered the aircraft’s nose, then handed over control to the co-pilot. A “MAYDAY” was declared and the aircraft returned to Accra. The operator’s subsequent engineering investigation discovered the remains of a beetle-like creature in the left pitot system.
Download report:
PDF icon Boeing 757-258, G-STRZ 12-09.pdf (338.58 kb)

 

Buffalo News: Piedmont pilots lack key safety training

Unfamiliarity with stick pusher shocks Flight 3407 victims' families, aviation experts

By Tom Precious and Jerry Zremski

NEWS STAFF REPORTERS

Updated: January 31, 2010, 8:30 am / 8 comments

http://www.buffalonews.com/cityregion/story/941017.html

 

Nearly a year after the pilot of Continental Connection Flight 3407 tried to

override the safety device that was supposed to help rescue the tumbling

plane, pilots at another regional airline flying into Buffalo say they have

never been trained in how that safety device works.

 

Even though investigators revealed months ago that Capt. Marvin Renslow,

Flight 3407's pilot, inappropriately pulled back on the controls after the

"stick pusher" activated, two Piedmont Airlines pilots told The Buffalo News

they have received no stick-pusher training.

 

"It'd be nice to know when that thing activates that I've had some sort of

experience with it," one Piedmont pilot told The Buffalo News on condition

of anonymity.

 

A spokesman for US Airways, which owns Piedmont, confirmed that Piedmont's

main training center in Charlotte, N.C., does not include hands-on

stick-pusher instruction for the more than 300 pilots undergoing

once-a-year, mandatory recurrent training.

 

"The FAA does not compel us to have the training. We feel it should be

there," said Morgan Durrant, a US Airways spokesman, adding that the airline

is now looking into upgrading its Charlotte simulator to offer the training

for the stick pusher.

 

Renslow didn't have hands-on stick-pusher training in the plane he was

flying, either, and federal safety officials have questioned whether that

could have been one of the factors leading to the crash, which claimed 50 lives.

 

More details about Flight 3407 are sure to emerge Tuesday, when federal

investigators release their final report on the accident.

 

Still, a great deal already has been learned about Colgan Air, the regional

airline that operated Flight 3407, along with the crew and the flight and

the crash's ramifications for aviation safety, particularly on regional airlines.

 

Colgan started giving its pilots stick-pusher training in a simulator after

the crash < but the new information from the Piedmont pilots shows that at

least one regional airline is still allowing its pilots to fly without

training in one of the life-or-death devices on their plane.

 

"I think that's terrible," said Mike Loftus, a former Continental pilot who

lost his daughter, Maddie, in the Clarence crash last Feb. 12. "It's an

accident waiting to happen."

 

No one can blame the crash of Flight 3407 solely on the handling of the

stick pusher, given that investigators also said the crew < which may have

been fatigued < let the plane get too slow and mishandled the positioning of

the plane's flaps.

 

Nevertheless, investigators have devoted a great deal of attention to the

stick pusher, a safety device that automatically activates when the plane

experiences an aerodynamic stall < when it gets so slow that the wings or

tail no longer keep the plane flying.

 

When that happens, the stick pusher pushes the plane's nose downward so that

it can gain speed and start flying again.

 

Aviation experts said that sudden uncontrolled movement < and the view of

the fast-approaching ground out the cockpit window < can be a shock to a

pilot unfamiliar with the stick pusher.

 

And when the stick pusher activated on Flight 3407, Renslow did the wrong thing.

 

"There was force exerted on the wheel which countered what was supposed to

be done," said Robert L. Sumwalt, a National Transportation Safety Board

member, at the May hearings in the Colgan crash.

 

What's more, pilots at Colgan told The News in December that they had been

taught to respond to aerodynamic stalls in the wrong way. They were taught

to maintain altitude even though aviation experts say pilots should lower

the nose of a stalling plane to gain speed and regain control, which is

precisely what the stick pusher is supposed to automatically do.

 

Safety board members and witnesses discussed stick-pusher training at length

at the NTSB hearings in May.

 

Asked if pilots should receive simulator training in the stick pusher,

Robert K. Dismukes, chief scientist at the NASA Ames Research Center, said:

"Absolutely. Just a few exposures would make it somewhat less astonishing

when it happens."

 

That kind of training is not routinely happening at Piedmont, a US Airways

subsidiary that flies turboprops throughout the Northeast, including some

flights between Buffalo and New York's LaGuardia International Airport.

 

New Piedmont pilots and those being upgraded to different planes in the past

year began going to facilities in Toronto or Seattle with stick-pusher

training, said Durrant, who also said there is stick-pusher information

contained in pilot training manuals and in classroom sessions.

 

But Piedmont pilots strongly disputed those claims.

 

For one thing, the airline has not been hiring pilots during the recession.

 

And for another, the pilots said any reference to the stick pusher in any

manuals is almost useless, since it includes no information on how the

devices actually work or how a pilot should react if the safety feature

suddenly engages.

 

The Piedmont pilots blamed the lack of stick-pusher training on cost

considerations and a coziness between the carrier and the Federal Aviation

Administration, which does not require the training.

 

"It's the classic story of the FAA treating the airlines like customers,"

said one Piedmont pilot, who spoke on condition of anonymity for fear of

getting fired.

 

Told that another regional was still not doing stick-pusher training, FAA

Administrator Randy Babbitt said other airlines were considering adding such

training < but he downplayed the need for it.

 

"Remember the key component we're training for is to avoid the stall,"

Babbitt said. "You never want the situation to get that far. You may want to

demonstrate what the airplane can do, but the training is to never get to

the stall."

 

Nevertheless, other aviation experts were shocked that Piedmont pilots still

had not been trained in how to use the stick pusher.

 

"It is critical, if a piece of equipment like that is installed, that the

pilots understand why it's there and how it operates," said Capt. Rory Kay,

executive safety chairman for the Air Line Pilots Association.

 

"I fail to understand how the FAA could not require a training program to

not include a comprehensive explanation of and demonstration of the stick

pusher," Kay added.

 

One Piedmont pilot said the FAA should require the stick pushers to be

turned off until pilots are trained.

 

"You get guys who say I'm not going to let the plane get to that point. But

the guys in the Colgan crash got to that point and didn't know what to do,"

the pilot added.

Dash 8 Buffalo'd by Dumb Warnings

 

JS,
 
As I recall, the 'stick pusher' invention was made by the Poms (another quaint but inappropriate Pommy invention?) to counter the deep stall phenomena encountered during the test flying of the BAC111 at Bournemouth.  I believe test pilot Bill Bedford rode one in when he discovered himself in an irrecoverable deep stall.  It was then subsequently applied to all swept wing heavies along with stick shakers (as a belt and braces approach - typically Pommy!!) to prevent recurrence of the problem, particularly for the high 'T' tailers.  The shakers initiated first, then the pusher initiated as a last response to the developing situation.   Why it is used on a plank wing beats me.  The ATR42 was not so equipped, just a stick shaker; a far more sound tactile warning system.  All through training, the airframe pre-stall judder is hammered into us as the significant stall warning symptom; the stick shaker does this admirably, particularly with shaker modulation intensifying with a deepening approach to stall situation developing.
 
N.  
 


Subject: RE: A page from FAA.gov /Dash 8 Buffalo'd by Dumb Warnings
Date: Thu, 4 Feb 2010 23:28:57 +0800

a.    "In the next few seconds, a so-called "stick pusher" automatically tried to suddenly lower the nose of the aircraft to gain airspeed and lift as a way to recover from the stall. The captain fought that device three separate times, deepening a stall that eventually became unrecoverable."

 

b.    “the board reaffirmed its preliminary conclusions that a startled and inadequately trained crew reacted improperly to the stall.”

 

“In detailing the sequence of events as the plane quickly lost airspeed as it descended toward the airport on a stormy night, investigators and board members reiterated that Capt. Renslow reacted improperly to a so-called "stick shaker" warning that the plane was about to lose lift. Contrary to Colgan's training, he aggressively raised the nose."That's very unusual behavior," said Tom Haueter, the board's top aviation investigator. "I quite frankly can't explain it."

 

In the next few seconds, a so-called "stick pusher" automatically tried to suddenly lower the nose of the aircraft to gain airspeed and lift as a way to recover from the stall. The captain fought that device three separate times, deepening a stall that eventually became unrecoverable.

 

 

Solution: 1. Fighting a stick-pusher by opposing it is instinctive, particularly when caught by surprise. You have to ask yourself: "if there'd been no stick-pusher fitted and just a stick-shaker, would the captain have carried out a standard stall recovery?” The stick-pusher is meant to encourage and stimulate a response in the correct direction (i.e. the pilot is supposedly stimulated to lower the nose and reduce the angle-of-attack whilst selecting max power). However the practical effect is the innate human instinct to oppose the most evident characteristic of the surprise anomaly. That’s why the captain raised the nose repeatedly, compounding the situation and embedding the aircraft in an unrecoverable accelerated stall.

             2.  A far more realistic human-factored arrangement would be an audio stall warning that cut in as the AoA exceeded a logical threshold and then changed pitch as the AoA increased. Think in terms of an identifiable low volume, low-pitched moan upsweeping to a high volume, high-pitched scream as the AoA increases. It would need a cut-out for use in malfunctions, however its use for stimulating a correct response for stall recovery would be far more instinctive than the offensive stick-pusher interfering with the flight-controls. The psychology is undoubtedly in favour of the audio alert. I can recall when the first RAWS warning was fitted to the SP2H Neptune. Prior to this fitment of a Radar Altimeter Warning System, we had a mere non attention-getting radalt height-selectable bug-initiated red light (non-flashing) adjacent to the Radar Altimeter. It was in no way attention-getting. The RAWS introduced an aural alert and a flashing red light whose frequency (of flashing and aural tone) changed in consonance as both the rate of descent increased and the radar altitude decreased. That system must have saved countless numbers of P-2’s and P-3’s involved in low-level Julie hexing and MAD trapping at night at 300ft. You tended to get distracted by trying to visually ontop the sonobuoy lights and retro-markers and flame-floats and markers marine. On a starry night you could easily become confused by lights in the water intermingling with the stars of the sky (there being no visible horizon) – especially when turning steeply to counter cross-wind drift. I can recall responding promptly and correctly to sudden aural/visual RAWS alerts on numerous occasions. The chop-rate cooked off for three seconds passing 300ft, went silent until 100 feet and then cut in continuous as you passed 100 feet ASL. But the background continuous tone went on telling you that you had a rate of descent – and only cut out with a rate-of-climb transition. That’s old technology. Imagine what they could now do with aural/visual AoA warnings on an approach. I prefer pitch-toned alerters, rather than the muttered monotone of artificial voice warnings.

 

c.   These accident pilots (Buffalo’s Dash8 and Amsterdam’s Turkish 737) were criticized for missing the speed trend indication. But that’s a non-obvious little bug lost in a sea of bugs on the panel. Aural alert cut-in is a TRUE ALERTER, whereas (proven at Buffalo) the stick-pusher is a proven killer. It alarms rather than alerts.

Summary:

The “go for it” escape mentality. i.e. I blame the inbred 'Go Around' culture.

Missed the 500' stabilized approach gate? ............Go Around.

Late configuring?................Go around.

Landing a bit long, even when light?.............Go Around.

Something happens.. maybe a low-key caution or latish ATC clearance?..............Go Around.

Lose an engine on final.........(like FR at Rome?) ......Go around.

Unstable approach? fix it? ..nope....Go around!

So when this guy, in an a/c with manual throttles got in trouble, what do you think his instinct was?

 

Why did the copilot pull the flap in, thus exacerbating the high AoA incipient stall into an accelerated stall?? Cause she (also) was in GOING AROUND mode!

 

Conclusion:   All other prelude factors (fatigue, complacency, inattentiveness, commuting, non-sterile cockpit chat, improper icy approach speed (the ice reference switch), lack of an autothrottle etc) were contributing and preliminary, i.e. they helped set the stage. However this type of dumbo setup occurs daily - in aviation globally. The true airmanship trick is in then avoiding the coup-de-grace of completing the Swiss Cheese hole alignment. That’s where the timely alert (but do not alarm) hardware comes into its own during a highly dynamic event. If the alerting system is properly keyed to ping the pilots into a sudden awareness of their peril and offers an instinctive solution (lowering the nose and increasing power quickly makes the very annoying high-pitched squeal noise diminish), then success is practically automated. However on the Dash 8 and in many other stick-pusher types, the converse is true. It would be something easily practiced in a simulator….. then stall recovery becomes truly instinctive and is accomplished safely at the incipient stage, with or without a stick-pusher. The NTSB emphasis is on training pilots to escape from sudden stalls. My opinion is that you need the appropriate system to stimulate a correct response. What they have in the stick-pusher is a lethal incentive for instinctive denial and contrariness i.e. to oppose the sudden foreign and unfamiliar flight-control input. Even an “old head” could be sucked into that mistake. What is needed is not necessarily a defence in depth…… just an appropriate last minute life-saver. That’s presently missing. The stick-pusher is a psychologically inappropriate device, given the go-round mindset that’s a large part of modern airline training.

 
any responses to: james.smith@iinet.net.au