The danger of overcontrolling while recovering from unusual attitudes
Thread Starter
The danger of overcontrolling while recovering from unusual attitudes
In February 1963, a Boeing 720 of North West Orient Airlines broke up in flight during an attempted recovery from an unusual attitude sustained in a thunderstorm encounter.
See: https://aviation-safety.net/database...?id=19630212-0
PROBABLE CAUSE: "The unfavourable interaction of severe vertical air drafts and large longitudinal control displacements resulting in a longitudinal "upset" from which a successful recovery was not made."
Then on 1 January 2007, Adam Air Indonesia PK-KKW a Boeing 737-400 crashed after the crew lost control in marginal VMC conditions when it developed an IRS fault. The aircraft reached 100 degrees of bank, 50 degrees nose down and 3.5g; it broke up at 490 knots in the dive.
See full report at: https://reports.aviation-safety.net/...734_PK-KKW.pdf
An extract from the accident report stated:
Throughout most of the flight, the autopilot had been holding some left wheel (aileron) to hold wings level. Just prior to the autopilot disengaging, the autopilot was holding approximately 5 degrees of left wheel. At 06:57:36, the autopilot disengaged, and the wheel returned to center. This resulted in a slow right roll of approximately 1 degree per second. The roll rate was arrested with the wheel (aileron) at 06:57:45, and again at 06:58:00, but the wheel inputs were momentary, and the aircraft continued to roll to the right.
The aural alert BANK ANGLE, BANK ANGLE, BANK ANGLE, BANK ANGLE
occurred at 06:58:10.6 when the aircraft reached 35 degrees of bank angle.
Again the bank angle was briefly arrested, but was followed momentarily by a right wing down wheel input. At 06:58:23, sufficient wheel (approx 15 deg) was used to reverse the roll rate, but again was followed by right wheel input, continuing the right wing down roll rate.
Subsequently the pilot began to pull on the control column (elevator), modestly at first, commanding approximately 1.1g. As the aircraft rolled right through 60 degrees of bank angle, the pilot began to steadily increase control column pull (elevator), while continuing to roll right.
The pitch attitude at 06:58:23 was approximately 5 degrees aircraft nose down. Shortly after, the aircraft’s pitch rate increased to 2.3 deg/sec aircraft nose down. The pitch attitude reached negative 60 degrees (nose down) at 06:58:50. The pitch rate subsequently became positive, reducing the nose-down attitude.
The CVR revealed that both pilots became engrossed with trouble shooting
Inertial Reference System (IRS) anomalies for at least the last 13 minutes of
the flight, with minimal regard to other flight requirements. For about
46 seconds after the autopilot disengaged, the pilots were completely occupied with trouble shooting. This included attempts to identify the IRS problems, and some attempts at corrective actions of the IRS and the navigation instruments.
Even after the first BANK ANGLE, BANK ANGLE, BANK ANGLE, BANK
ANGLE alert sounded at 06:58:10.6, the crew did not make timely and
appropriate flight control inputs to recover control of the aircraft.
There was no evidence that either of the pilots appropriately referenced the
flight instruments.
............................................................ ........................................
On 7 January 2017 a CL 600 Challenger lost control at cruise altitude after a wake turbulence encounter with an A380. Several thousand feet were lost before the Challenger recovered to controlled flight. A diversion was made to the nearest suitable airport. The Challenger suffered severe damage. Later investigation revealed the damage was exacerbated by inappropriate pilot inputs during the attempted recovery from the wake turbulence encounter.
The interim report by the German Federal Bureau of Aircraft Accident Investigation included the statement:
" Be aware that in-flight incidents have demonstrated that pilot inputs may exacerbate the unusual attitude condition with rapid roll control reversals carried out in an “out of phase” manner.
– Be aware that if the autopilot is engaged, intentional disconnection can complicate the scenario, and the autopilot will facilitate the recovery.
– Avoid large rudder deflections that can create important lateral accelerations, which could then generate very large forces on the vertical stabiliser that may exceed the structural resistance. Although some recent aircraft types are protected by fly-by-wire systems, use of the rudder does not reduce the severity of the encounter nor does it improve the ease of recovery.
............................................................ ..........................................
On 12 November 2001 an American Airlines A300 crashed after encountering wake turbulence from a departing Boeing 747.
See https://www.ainonline.com/aviation-n...-spreads-blame
One extract from that report stated:
"AA 587 had just taken off from John F. Kennedy International Airport bound for the Dominican Republic when it crashed in a residential area near the Rockaway Beach area of Queens, killing all 260 people on board and five people on the ground.
The A300’s vertical stabilizer and rudder separated in flight and were found in Jamaica Bay, about one mile north of the main wreckage site. The two engines, which also separated from the aircraft seconds before it hit the ground, were found several blocks north and east of the main wreckage.
The NTSB said the vertical stabilizer was torn off in flight as a result of aerodynamic loads that were created by the first officer’s unnecessary and excessive rudder pedal inputs after the aircraft encountered wake turbulence from a Japan Air Lines Boeing 747-400 that had taken off minutes before it. Investigators said the A300 would have passed through the wake turbulence successfully if the pilots had done nothing with the rudder".
In each case of the stated accident reports, it is apparent that inappropriate pilot input to the flying controls in response to a turbulence encounter was the catalyst to the final result.
............................................................ .........................................
Moral of the story? Over-controlling during recovery from an unusual attitude has been known to lead to severe and sometimes fatal damage to an aircraft. One good advice is to "sit on your hands" for a few seconds while determining what corrective action is most suited to recovering the situation. Another advice should be self explanatory and that is be proficient on recovery from unusual attitudes in IMC.
See: https://aviation-safety.net/database...?id=19630212-0
PROBABLE CAUSE: "The unfavourable interaction of severe vertical air drafts and large longitudinal control displacements resulting in a longitudinal "upset" from which a successful recovery was not made."
Then on 1 January 2007, Adam Air Indonesia PK-KKW a Boeing 737-400 crashed after the crew lost control in marginal VMC conditions when it developed an IRS fault. The aircraft reached 100 degrees of bank, 50 degrees nose down and 3.5g; it broke up at 490 knots in the dive.
See full report at: https://reports.aviation-safety.net/...734_PK-KKW.pdf
An extract from the accident report stated:
Throughout most of the flight, the autopilot had been holding some left wheel (aileron) to hold wings level. Just prior to the autopilot disengaging, the autopilot was holding approximately 5 degrees of left wheel. At 06:57:36, the autopilot disengaged, and the wheel returned to center. This resulted in a slow right roll of approximately 1 degree per second. The roll rate was arrested with the wheel (aileron) at 06:57:45, and again at 06:58:00, but the wheel inputs were momentary, and the aircraft continued to roll to the right.
The aural alert BANK ANGLE, BANK ANGLE, BANK ANGLE, BANK ANGLE
occurred at 06:58:10.6 when the aircraft reached 35 degrees of bank angle.
Again the bank angle was briefly arrested, but was followed momentarily by a right wing down wheel input. At 06:58:23, sufficient wheel (approx 15 deg) was used to reverse the roll rate, but again was followed by right wheel input, continuing the right wing down roll rate.
Subsequently the pilot began to pull on the control column (elevator), modestly at first, commanding approximately 1.1g. As the aircraft rolled right through 60 degrees of bank angle, the pilot began to steadily increase control column pull (elevator), while continuing to roll right.
The pitch attitude at 06:58:23 was approximately 5 degrees aircraft nose down. Shortly after, the aircraft’s pitch rate increased to 2.3 deg/sec aircraft nose down. The pitch attitude reached negative 60 degrees (nose down) at 06:58:50. The pitch rate subsequently became positive, reducing the nose-down attitude.
The CVR revealed that both pilots became engrossed with trouble shooting
Inertial Reference System (IRS) anomalies for at least the last 13 minutes of
the flight, with minimal regard to other flight requirements. For about
46 seconds after the autopilot disengaged, the pilots were completely occupied with trouble shooting. This included attempts to identify the IRS problems, and some attempts at corrective actions of the IRS and the navigation instruments.
Even after the first BANK ANGLE, BANK ANGLE, BANK ANGLE, BANK
ANGLE alert sounded at 06:58:10.6, the crew did not make timely and
appropriate flight control inputs to recover control of the aircraft.
There was no evidence that either of the pilots appropriately referenced the
flight instruments.
............................................................ ........................................
On 7 January 2017 a CL 600 Challenger lost control at cruise altitude after a wake turbulence encounter with an A380. Several thousand feet were lost before the Challenger recovered to controlled flight. A diversion was made to the nearest suitable airport. The Challenger suffered severe damage. Later investigation revealed the damage was exacerbated by inappropriate pilot inputs during the attempted recovery from the wake turbulence encounter.
The interim report by the German Federal Bureau of Aircraft Accident Investigation included the statement:
" Be aware that in-flight incidents have demonstrated that pilot inputs may exacerbate the unusual attitude condition with rapid roll control reversals carried out in an “out of phase” manner.
– Be aware that if the autopilot is engaged, intentional disconnection can complicate the scenario, and the autopilot will facilitate the recovery.
– Avoid large rudder deflections that can create important lateral accelerations, which could then generate very large forces on the vertical stabiliser that may exceed the structural resistance. Although some recent aircraft types are protected by fly-by-wire systems, use of the rudder does not reduce the severity of the encounter nor does it improve the ease of recovery.
............................................................ ..........................................
On 12 November 2001 an American Airlines A300 crashed after encountering wake turbulence from a departing Boeing 747.
See https://www.ainonline.com/aviation-n...-spreads-blame
One extract from that report stated:
"AA 587 had just taken off from John F. Kennedy International Airport bound for the Dominican Republic when it crashed in a residential area near the Rockaway Beach area of Queens, killing all 260 people on board and five people on the ground.
The A300’s vertical stabilizer and rudder separated in flight and were found in Jamaica Bay, about one mile north of the main wreckage site. The two engines, which also separated from the aircraft seconds before it hit the ground, were found several blocks north and east of the main wreckage.
The NTSB said the vertical stabilizer was torn off in flight as a result of aerodynamic loads that were created by the first officer’s unnecessary and excessive rudder pedal inputs after the aircraft encountered wake turbulence from a Japan Air Lines Boeing 747-400 that had taken off minutes before it. Investigators said the A300 would have passed through the wake turbulence successfully if the pilots had done nothing with the rudder".
In each case of the stated accident reports, it is apparent that inappropriate pilot input to the flying controls in response to a turbulence encounter was the catalyst to the final result.
............................................................ .........................................
Moral of the story? Over-controlling during recovery from an unusual attitude has been known to lead to severe and sometimes fatal damage to an aircraft. One good advice is to "sit on your hands" for a few seconds while determining what corrective action is most suited to recovering the situation. Another advice should be self explanatory and that is be proficient on recovery from unusual attitudes in IMC.
One problem these days is that the vast majority of pilots have never been above 2G or beyond 60 AoB. So when the upset occurs it's completely new. Basic aeros should be a requirement prior to PPL.
Guest
Posts: n/a
Usually for unusual attitude Sim checks my control input is inversely proportional to the amount of pressure felt through the control yoke - sometimes resulting in the airspeed briefly exceeding Vne prior to coming climbing out of the parabola. The idea in mind is to be gentle and not overstress the airframe, especially above Vma.
If the amount of force applied resulted in disconnection of a quasi "interconnect unit", could this be an indication that excessive force was being applied?
If the amount of force applied resulted in disconnection of a quasi "interconnect unit", could this be an indication that excessive force was being applied?
