Excessive TCAS Evasion Injures 20

IrishSheepdog

Sitting in the median
Excessive TCAS evasion injured 20 on Taiwanese 757: inquiry

Taiwanese investigators have found that a Boeing 757's unnecessarily fierce descent during a collision-avoidance maneuver injured 20 people on board the jet, four of them seriously.

Three passengers were left with broken bones and a fourth was knocked unconscious as the pilot put the Far Eastern Air Transport aircraft into a dive which, at one point, exceeded 12,000ft/min. Ten other passengers and six flight attendants suffered light injuries and interior cabin fittings were damaged.

During the maneuver, a response to a 'descend' command from the TCAS collision-avoidance system, the aircraft was subjected to negative forces of up to 1.06g for about 4s, followed by positive 2.48g for 2s as the pilot arrested the descent and leveled.

Taiwan's Aviation Safety Council, in its inquiry into the 16 November 2006 incident, has concluded that the evasive action was "excessive" and that a properly-executed standard response to the TCAS alert would have sufficed.

The 757 had been approaching Jeju in Korea along airway B576 when an Inchon area controller instructed it to descend from FL390 to FL310. As the jet neared FL340 the controller realized it could conflict with a Thai Airways International Boeing 777-300 cruising at FL340 in the opposite direction.

With the jets separated by 12.2nm (22.6km) horizontally, and just 51ft vertically, both aircrews received initial traffic advisories warning of one another's presence. The controller, also aware of the potential threat, started instructing the 757 to halt its descent before he realized the aircraft had already passed below FL340, and decided to let it continue. The 757's crew, however, did not comprehend the mixed message and leveled the aircraft at FL338.

Thirteen seconds after the traffic advisory the TCAS ordered simultaneous collision-avoidance commands, telling the 757 pilots to descend and the 777 crew to climb.

"The [757's] flight crew did not complete the TCAS resolution advisory standard operation procedures and commenced an excessive high-rate descent," says the ASC inquiry. "The induced negative g-force resulted in the occupants' injury."

It states that maintaining a normal 1,500ft/min descent rate would have provided enough vertical clearance between the aircraft, and points out that the controller was also resolving the conflict in the horizontal plane by instructing the 777 to make a right turn. At their closest point of approach the two aircraft had 0.85nm lateral and 2,611ft vertical separation.

Although the 757's crew had illuminated the seat-belt sign a few minutes before the encounter, several passengers were still moving around the cabin either to reach the washrooms or purchase duty-free goods.

"Most of the injured passengers lost their protection because their seat-belts were not fastened while the 'fasten seat-belt' sign was still on," says the ASC.

Investigators have stressed that the original conflict arose partly from the use of non-standard phraseology and a failure, both by the 757 pilots and the controller, to follow proper TCAS procedures.

Although Taipei-based Far Eastern Air Transport started introducing improved TCAS and crew resource management training, the airline suspended operations in May after running into financial problems.
 
I don't have TCAS but from speaking with another pilot last week, he says it's designed so that a 5 degree change in pitch is enough to avoid traffic.
 
Different manufacturers have different ways of displaying RA guidance. Instead of standardizing the presentation, everyone patented their own method. E.g., Patent No. 5248968, "TCAS II pitch guidance control law and display symbol"

As far as I know, TCAS can't provide guidance beyond ±6,300 ft/min, and yeah, typically will not have a minimum advisory altitude rate greater than 1,000 ft/min.

Incidentally, the flaps-up manuevering load limits for a 757 are -1g to +2.5g ... and they managed to hit both. :eek:
 
This type of overreaction should be have been trained out in the simulator. Its obvious that they had never been trained how to respond to a RA, the PF freaked out and overreacted. It reminds me of this Eagle pilot who kept damaging engines by firewalling the power levers on a missed approach/go-around (I heard they fired him after the 3rd set of saab engines he trashed.)
 
"Most of the injured passengers lost their protection because their seat-belts were not fastened while the 'fasten seat-belt' sign was still on," says the ASC.

Unrelated to the TCAS issue, but a good reminder to always keep that seatbelt fastened......
 
Especially when the sign is on....friggin idiots.
Oh you know how some passengers get, especially the professional "frequent" fliers! They think we put that sign on when nothing is going to happen, or that it won't be much and they can handle it. After all, they've driven over potholes before and managed just fine. ;)
 
Freaking Asian drivers.

When I instructed, I had a Chinese-American student. He had a great sense of humor and liked to poke fun of himself. Whenever we taxied out of the ramp he would say "luk out ayaplane! Chinese driva!"

It was classic!
 
and just when you think with all that automation in the cockpit pilots can't screw up anymore... :D
 
Oh you know how some passengers get, especially the professional "frequent" fliers! They think we put that sign on when nothing is going to happen, or that it won't be much and they can handle it. After all, they've driven over potholes before and managed just fine. ;)

Yeah, might as well just get rid of the "Fasten Seatbelts" sign like they got rid of the "No Smoking" sign on some aircraft like Mesaba's CRJ-900s.

Last year in EWR, we were taxiing to Terminal C and we had to stop on Y short of RL for a few moments, with another 737 also holding short of RL on the parallel taxiway. Some of the pax thought that we stopped at the gate, so they started unfastening their seatbelts and getting up to get their luggage and the purser had to get up to tell them to sit down because we were not at the gate, and the "Fasten Seatbelts" sign was on the whole time (as it should have been because we were not at the gate). But people don't care. Flying has become so routine for them that they think they know what will happen during any phase of the flight and they don't expect anything to go wrong.
 
Yeah, might as well just get rid of the "Fasten Seatbelts" sign like they got rid of the "No Smoking" sign on some aircraft like Mesaba's CRJ-900s.

Last year in EWR, we were taxiing to Terminal C and we had to stop on Y short of RL for a few moments, with another 737 also holding short of RL on the parallel taxiway. Some of the pax thought that we stopped at the gate, so they started unfastening their seatbelts and getting up to get their luggage and the purser had to get up to tell them to sit down because we were not at the gate, and the "Fasten Seatbelts" sign was on the whole time (as it should have been because we were not at the gate). But people don't care. Flying has become so routine for them that they think they know what will happen during any phase of the flight and they don't expect anything to go wrong.
It's okay. When someone gets injured and they're expecting some type of compensation they will find out it was their error that caused them injury so "hard luck!" to them. :)
 
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