Report: ATR-72 control difficulties following rudder maintenance

April 18, 2011

The U.K. AAIB published a Special Bulletin including three safety recommendations regarding control difficulties that were encountered by the crew of an ATR-72 during a post-maintance flight.

The aircraft had undergone routine maintenance at an engineering facility at Edinburgh Airport immediately prior to the incident flight.
Everything appeared normal during the crew’s pre-flight checks, which included a full-and-free check of the flying controls.
The aircraft took off at 21:22 from runway 24 at Edinburgh, with the co-pilot acting as the handling pilot.
After carrying out a standard instrument departure the crew climbed the aircraft to FL 230 at a speed of 170 kt with the autopilot engaged. As the aircraft levelled and accelerated through about 185 kt, the crew felt the aircraft roll to the left by about 5 to 10° and they noticed that the slip ball and rudder trim were both indicating fully right. The co-pilot disengaged the autopilot and applied right rudder in an attempt to correct the sideslip and applied aileron to correct the roll. He reported that the rudder felt unusually “spongy” and that the aircraft did not respond to his rudder inputs. Approximately 15° to 20° of right bank was required to hold a constant heading with the speed stabilised above 185 kt and a limited amount of aileron trim was applied to assist. Shortly after regaining directional control a FTL CTL caption appeared on the Crew Alert Panel (CAP) and the FLT CTL fault light illuminated on the overhead panel, indicating a fault with the rudder Travel Limitation Unit (TLU). The commander requested radar vectors from ATC for a return to Edinburgh, later declaring a PAN.

The crew carried out the required procedure from the Quick Reference Handbook (QRH). As part of the procedure they established that both Air Data Computers (ADC) were operating, before manually selecting the TLU switch to the LO SPD position. The aircraft had at this point temporarily slowed to below 180 kt. The co-pilot reported that on selection of LO SPD more roll control input was required to maintain heading and that roll authority to the right was further reduced. The commander therefore decided to return the TLU switch to AUTO and the required roll control input reduced. The green LO SPD indicator light did not illuminate.

An approach was made to runway 24, the aircraft was established on the ILS and was normally configured for a full flap landing. The crew added 10 kt to their approach speed, in accordance with the QRH. The co-pilot had to operate the control wheel with both hands in order to maintain directional control; the commander operated the power levers in the latter stages of the final approach. The co-pilot reported that the aircraft became slightly more difficult to control as the speed reduced, but remained controllable.

The aircraft landed just to the left of the runway centreline, whereupon the commander assumed control of the aircraft and applied reverse thrust. Despite the application of full right rudder pedal during the rollout, the aircraft diverged towards the left side of the runway. The commander re-established directional control using the steering wheel tiller. The aircraft was taxied clear of the runway and back to the engineering facility for inspection.

Th subsequent investigation and testing demonstrated that it is possible to incorrectly install the cams on the rear rudder quadrant shaft during maintenance. In this incident, the right hand cam was installed in the incorrect orientation and neither an independent inspection nor an operational test of the TLU system was performed. The incorrectly installed right hand cam was not detected prior to releasing the aircraft to service. When the TLU system automatically activated as the aircraft accelerated through 185 kt, the right hand roller encountered resistance as it came into contact with the upper lobe of the incorrectly installed cam, rather than slotting into the vee groove. This caused an uncommanded rudder input and associated control difficulties.

Three safety recommendations were made to the manufacturer, ATR.

The investigation is ongoing.

More information:

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FAA proposes $550,000 civil penalty against Executive Airlines

March 30, 2011

The U.S. Federal Aviation Administration is proposing a $550,000 civil penalty against Executive Airlines, Inc., of San Juan, P.R., for allegedly operating two ATR-72 twin turboprop planes when they were not in compliance with Federal Aviation Regulations.

The FAA alleges Executive Airlines, a subsidiary of AMR Corporation, failed to complete required periodic, time-specific inspections of the aileron control systems of two aircraft, as ordered by an FAA Airworthiness Directive. Compliance with those directives is mandatory.

The FAA alleges that Executive Airlines operated the two aircraft when they were not in compliance with regulations on at least 35 revenue flights between June 13 and June 19, 2009, because the airline exceeded the mandated number of flight hours for a re-inspection.

Executive Airlines has 30 days from the receipt of the FAA’s enforcement letter to respond to the agency.


Report: ATR-72 runway excursion accident following unstabilized approach (India)

January 13, 2011

Investigators from the Indian DGCA concluded that an ATR-72 runway excursion at Mumbai was caused by the failure of the crew to execute a go around during an unstabilized approach.

An ATR-72 passenger plane, operated by Kingfisher Airlines, was substantially damaged when it aquaplaned off the runway on landing at Mumbai-Chhatrapati Shivaji International Airport (BOM), India on November 10, 2009.

Flight IT4124 operated on a scheduled domestic flight from Bhavnagar Airport (BHU) to Mumbai. There were 36 passengers, 2 Infants and four crew members on board the aircraft.

Maintenance on runway runway 14/32 and runway 27 at Mumbai effected operations at the airport between certain times. There were several NOTAM’s in effect relating to runway 27:

GP RWY27 NOT AVBL DUE SHORTENED RWY27. BTN 0730-1130 ON EVERY TUE, 03 NOV 07:30 2009 UNTIL 23 MAR 11:30 2010
RWY27 CL LGT NOT AVBL. 27 OCT 12:30 2009 UNTIL 31 MAR 23:59 2010.
RWY27 TDZ LGT NOT AVBL. 27 OCT 12:30 2009 UNTIL 31 MAR 23:59 2010.
RWY27 SHALL BE USED FOR LDG AND TKOF FM A POINT 1262M FM THR OF RWY27
1.THE SHORTENED RWY SHALL BE DESIGNATED AS RWY 27A. RADAR VECTORED VISUAL APP WILL BE PROVIDED SUBJ TO VIS 2800M OR MORE.DECLARED DIST OF RWY27A-
RWY TORA TODA LDA ASDA
27A 1703M 1703M 1703M 1703M
2.THR MARKING PROVIDED ON BOTH SIDES OF RWY27A ON RWY SHOULDER AREA AT A DIST OF 180M
3.PAPI RWY27A PROVIDED
4.AIMING POINT MARKING PROVIDED ON SHOULDER OF RWY27A OPPOSITE PAPI
5.DIST INDICATION SIGN PROVIDED EV 300M FM RWY27A END.
6.TORA SIGN PROVIDED AT TWY Q HLDG POINT.
7.TEMP WING BAR LGT PROVIDED FOR THR.
8.RWY EDGE LGT,RWY CL AND RWY END LGT PROVIDED FOR RWY27A. BTN 0730-1130 UTC ON EV TUE ON [...],10,17,24 NOV 2009 [...]

Runway 27 thus was available only after runway intersection as runway 27A. To carry out operations on this reduced runway 27 a NOTAM was issued and designated runway 27A for visual approach only. The weather conditions prevailing at the time of accident was winds 070/07 knots visibility 2800 m with feeble rain. Prior to Kingfisher aircraft, Air India flight IC-164, an Airbus 319 had landed and reported to ATC that it had aquaplaned and broken two runway edge lights. The ATC acknowledged it and sent runway inspection vehicle to inspect the runway.

The ATC person was not familiar with the terminology of ‘aquaplaning’ and not realizing the seriousness of it, cleared the Kingfisher flight for landing. At the time of accident there were water patches on the runway. ATC also did not transmit to the Kingfisher aircraft the information regarding aquaplaning reported by the previous aircraft.

The ATR-72 approached high and fast. The aircraft landed late on the runway and the runway length available was around 1000 m from the touchdown point. In the prevailing weather conditions this runway length was just sufficient to stop the aircraft on the runway. During landing the aircraft aquaplaned and did not decelerate even though reversers and full manual braking was applied by both the cockpit crew. The aircraft started skidding toward the left of center line. On nearing the runway end, the pilot initiated a 45° right turn, after crossing Taxiway N10, the aircraft rolled into an unpaved wet area. It rolled over drainage pipes and finally came to a stop near open drain. There was no fire.

PROBABLE CAUSE OF THE ACCIDENT:

The accident occurred due to unstabilized approach and decision of crew not to carry out a ‘Go-around’.

Contributory Factors:

  1. Water patches on the R/w 27A
  2. Inability of the ATCO to communicate the aircraft about aquaplaning of the previous aircraft
  3. Lack of input from the co-pilot.

More information:

VT-KAC final report


EASA issues Emergency AD on ATR-72 flight controls

April 1, 2010

EASA issued an emergency airworthiness directive (EAD 2010-0063-E) regarding ATR-72 flight controls.

During flight control checks prior to take-off (cockpit pre-flight preparations), abnormal motion of the rudder pedal was observed in two ATR72-212A aeroplanes, the affected pedal staying stuck on its stop end position. Subsequent inspection showed that in both cases, one of the rudder pedal rods, Part Number (P/N) S2728116400000, was broken.

Further investigation revealed that an error has occurred during the manufacturing process of the affected rods. As a result, some of the rods (which have been identified as belonging to production batch numbers CC 2109699 and
CC 2118930) may have an outer diameter which is smaller than the minimum value as specified in the original design drawings.

The rods belonging to these batches were installed in the rudder pedal assemblies of certain aeroplanes. Most of the related rods have been checked and found to be in conformity with acceptable dimensions; those that were not
have been replaced while still on the production line, prior to delivery of the affected aeroplanes. However, seven (7) aeroplanes already in service have been identified that are likely to have the affected rods installed.

This condition, if not corrected, could lead to failure of the rudder pedal rod, possibly resulting in reduced control of the aeroplane. In combination with an engine failure or during a landing or take-off under crosswind conditions, such a failure could lead to loss of control of the aeroplane.

For the reasons described above, this Emergency AD requires inspection of the four rudder pedal rods, to detect a lower than acceptable outer diameter at each rod end, and replacement of any rods that fail the inspection criteria.


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