Posted on Thursday, August 09, 2007 - 8:50 am:

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The article in question was one of those “tragedy to triumph” stories, an Enquirer staple, about a girl, orphaned at an early age, who rose above to graduate from college, get religion, and marry a fine fella. It also had a “where are they now” flavor to it.

Posted on Thursday, August 16, 2007 - 2:42 pm:

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2.9 Flightcrew Actions After Takeoff
Even though the Safety Board determined that the flightcrew failed to configure the airplane properly for takeoff, the Safety Board examined the flightcrew’s actions after takeoff to see
if they could have prevented the accident.
By the time the airplane lifted off, the captain had rotated it to a 11” to 12” nose-up pitch
attitude. The stick shaker activated at liftoff and continued to operate throughout the flight. After liftoff, the captain rotated the airplane to a 13” to 14” noseup pitch attitude, and, 4.5 seconds after liftoff, the SSRS alarm activated and the airplane began to roll. The subsequent rolls and controlinputs required to recover from them decreased the airplane’s climb capability by about 20 percent.

Between the start of the first roll and initial impact, the airplane’s pitch attitude varied between 13” to 14” noseup and these pitch attitudes were either at or just below the angle of attack which activated the SSRS.

The Safety Board’s performance calculations showed that the airplane would have cleared the light pole if the roll oscillations were eliminated and the captain could have avoided them by
lowering the nose of the airplane and maintaining a pitch angle that would have positioned it at or
65 just below the stick shaker’s angle of attack. Given the configuration of the wing, flaps and slats retracted, the stick shaker would have initiated at an angle of attack of about 1 l", 2" below the SSRS’s angle of attack and below the angle of attack at which the airplane’s roll stability was compromised. Had the captain flown the airplane at a constant 11” angle of attack, he would have avoided the roll oscillations and the airplane would have cleared the light pole by about 80 feet.

Three Northwest DC-g-82 captains stated that, during an encounter with a windshear, they would consider flying the airplane above the pitch angle that would cause the SSRS to begin.

They stated that the airplane was not stalled at that pitch angle. One of these captains stated that he “would not be completely uncomfortable in the supplementary stall warning region if necessary for recovery.” Although the captain of flight 255 flew the airplane at and just below the angle of attack which activated the SSRS warning, there was no evidence to indicate that the captain of flight 255 entertained similar conclusions as to the airplane’s performance capabilities in this flight regime.

The evidence does not provide a sufficient basis for the Safety Board to conclude that his
entrance into this area of flight was intentional. The airplane lifted off the runway with the stick
shaker activated and at about a 11” to 12” noseup pitch attitude. To silence the stick shaker, the
captain would have had to release the back pressure on the control column and allow the nose to lower about 2”. Given the facts that the airplane had just taken off, that its climb rate was virtually negligible, and that the stick shaker was operating continuously, the Safety Board believes that it would be almost impossible to expect the captain to introduce control inputs which threatened to reverse the airplane’s negligible rate of climb. Throughout the entire flight, the airplane was operating in proximity to the ground. The Safety Board believes that one possible explanation for the manner in which the airplane was flown was that the control inputs of the captain were merely a reflex action on his part to avoid recontacting the ground.

Any evaluation of the captain’s flight techniques must start with a conclusion as to what the captain and first officer believed the configuration of the airplane was. Since they both believed that the airplane was configured as required for takeoff before they began the takeoff, the fact that the takeoff warning did not sound in accordance with their expectations would have further reinforced their belief that the flaps were at 11” and that the slats were extended to the mid-sealed position. During the time they had been in the airplane, there had been numerous communications concerning windshear and microbursts in proximity to the airport. Also, thunderstorms, which might reinforce the possibilities of windshear or gust were in sight north and west of the airport. When the
immediate nature and strength of repetition, both verbally and visually, of the possibility of
windshear is combined with the reasons for the crew’s belief in a properly configured airplane, the Safety Board believes that it is reasonable to conclude that the flightcrew thought they had
encountered a windshear when the stall warnings began after liftoff and focused their attention on
escaping from a windshear encounter. Windshear recovery procedures do not call for a
configuration change. Instead, they call for power and attitude adjustments to prevent the airplane
from striking the ground and, thereafter, to try and establish a rate of climb. The DFDR indicated
that the captain was trying to maximize the performance of the airplane with pitch attitude
adjustments. In addition, the rolling of the airplane also would have been indicative of the type of turbulence that can accompany a low altitude windshear or microburst. The fact that the pitch adjustments exceeded those recommended for use during windshear encounters and placed the
airplane at angles of attack which activated the SSRS alarm could be attributed to reflex actions by the captain to clear the oncoming light poles.

The stall recovery procedures contained in the Northwest APH stated, in part, that if a stall
were encountered with the airplane configured for takeoff the pilot flying the airplane should apply
and call “Max power, flaps 15” while simultaneously relaxing the back pressure enough to stop the stick shaker or buffeting. The pilot not flying will select the flaps and trim the throttles to maximum power. The DFDR recording indicated that maximum power was applied; however, the CVR showed 66 that the captain did not call for the flaps to be set to 15”. The fact that the captain did not try to use this procedure could further indicate that he believed he had encountered a windshear.

The total amount of time that the airplane was flyable was 14 seconds. Even if the crew
had recognized that the increasing airspeed was inconsistent with a decreasing performance
windshear, the short period of time for them to completely and accurately assess what was
happening to the airplane was probably inadequate. The combination of airplane rolling, the stall
warnings, and the possibility of imminent ground contact were probably powerful enough stimuli to
focus the crew’s attention completely on the factors relevant to avoiding ground contact and to
maintaining airplane control and did not allow them sufficient flexibility to expand their attention to include all the factors that were required to more completely assess the airplane’s condition.

The Safety Board believes that the captain’s bracketing of the SSRS alarm was a reflexive
action to the adverse visual cues presented to him. However, the continued operation at the higher SSRS angle of attack instead of the stick shaker angle of attack resulted in the onset of roll oscillations and the loss of critical climb capability.

All DC-9 series airplanes that have leading edge wing slat systems are equipped with an
SSRS. The SSRS system is unique in that it provides an indication of the stall angle of attack; therefore, it may lead to over-confidence while operating above the normally accepted upper limit of stick shaker angle of attack. The Safety Board found that some DC-g-82 captains expressed no concern about operating at the SSRS angle of attack. Only one captain who was interviewed stated that “he would not try to go into the supplementary stall warning area.” It appears that some captains did not recognize the SSRS as an announcement of stall. They viewed the SSRS alarm as a warning with some margin as is the case with the stick shaker where there is a margin. In addition,
these captains expressed no concern about the loss of lateral control at SSRS and the resultant
degradation of climb performance procedure taught by most airlines for windshear. Actually, the
crew were maintaining pitch at or near the SSRS and should have been maintaining a lower angle at
stick shaker.

The possible reasons for these beliefs about the SSRS are either that training is inadequate
or that the simulators do not accurately model the decreased roll stability at angles near to or
greater than the SSRS angle of attack, thus giving a false sense of security. MD-80 flightcrews should be trained on the lateral control hazards that exist while operating at the SSRS angle of attack and the fact that the additional climb performance capability that exists above the stick shaker angle of attack is minimal and easily negated when small roll oscillations commence. MD-80 pilots should be trained to operate at or below the onset of stick shaker activation and to avoid the activation of the stick shaker except in those conditions beyond their control.

The Safety Board cannot determine if the selection of the go-around mode resulted from
an inadvertent actuation of the TOGA switch when the captain advanced the throttles after liftoff or whether the TOGA switch was activated intentionally. However, there is no normal, abnormal, or emergency procedure in the Northwest APH which recommends that the F/D be transferred from the takeoff mode to the go-around mode under the conditions of flight that existed when the transfer occurred.

The simulations of the F/D’s theoretical design performance for the condition of the
accident takeoff demonstrated that, had the F/D remained in the takeoff mode and had the captain
been able to follow the guidance provided by the command bar, the airplane theoretically would
have been flown at pitch attitudes below the stick shaker’s angle of attack. Flight in this regime
would have increased the airplane’s roll stability. Consequently, the airplane’s climb performance would not have been degraded by roll oscillations and spoiler deflections and the airplane would have cleared the light pole.

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3.1 Findings

1. Flight 255 did not encounter windshear either during the takeoff roll or after
liftoff.

2. Flight 255 took off with its wing’s trailing edge flaps and leading edge slats
retracted.

3. The flightcrew did not extend the airplane’s flaps and slats.

4. The flightcrew did not perform the airplane’s checklists in accordance with the
prescribed procedures contained in the Northwest Airplane Pilots Handbook. The
flightcrew did not accomplish the TAXI checklist and therefore did not check the
configuration of the airplane.

5. The airplane’s climb performance was severely limited by the flightcrew’s failure to
properly configure the wing for takeoff.

6. The airplane would have cleared the light pole by 500 feet with only its wings slats
extended.

7. The roll stability of the airplane was decreased as a result of flying it at or below the
SSRS alarm and near the stall angle of attack. The resultant rolling of the airplane
degraded its climb performance.

8. If the airplane had been flown at or below the stick shaker angle of attack, the roll
stability would have been increased and the airplane would have cleared the light
pole.

9. The CAWS unit’s takeoff warning system was inoperative and, therefore, did not
warn the flightcrew that the airplane was not configured properly for takeoff.

10. The failure of the takeoff warning system was caused by the loss of input 28V dc.
electric power between the airplane’s left dc. bus and the CAWS unit.

11. The interruption of the input power to the CAWS occurred at the P-40 circuit
breaker. The mode of interruption could not be determined.


13. The light poles at the impact site did not exceed the limiting standards contained in
14CFRPart77.

3.2 Probable Cause

The National Transportation Safety Board determines that the probable cause of the
accident was the flightcrew’s failure to use the taxi checklist to ensure that the flaps and slats were extended for takeoff. Contributing to the accident was the absence of electrical power to the airplane takeoff warning system which thus did not warn the flightcrew that the airplane was not
configured properly for takeoff. The reason for the absence of electrical power could not be
determined.

Posted on Thursday, August 16, 2007 - 3:22 pm:

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View with caution. Not recommended for children or the weak.

http://www.aerialpics.com/N/fl ight255.html