Transportation Safety Board of Canada 200 Promenade du Portage Gatineau, Quebec K1A 1K8 29 April2014 Mr. Martin Eley Director General, CivilAviation TransportCanada 330 Sparks Street Place de Ville, Tower C 5th Floor, Area A Ottawa, Ontario KlAONS Bureau de fa securite des transports du Canada


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# Su~&-t~A-V~IA_T_I_O_N~S-A_F_E~~-A-D_V_I_s_O=R-Y~A-U_C_O~l-S_~_D_l_-A_l~~~~~~~~~~~~b/ Operation ofAircraft with Negative Torque Sensing Systems Dear Mr. Eley, On 10 November 2013, Bearskin Airlines flight 311, a SwearingenSA227AC (registration C-FFZN, serialnumberAC-785B), was conducting aninstrumentapproach to Runway 26 at the Red Lake Airport (CYRL), Ontario. At 1827 Central StandardTime, the crewreported 5 miles onfinal for Runway 26. At 1828 while the aircraftwas atapproximately 500 feet above ground level and 1.5 nautical miles from the runway threshold, the crew declared anunspecified emergency. Shortly after, the aircraftveered to the left and struck trees and a power line approximately 800 meters south of the approach end ofthe runway. The aircraftwas destroyed byimpactforces and fire. Two crewmembers and 3 passengers sustainedfatal injuries. Two passengers escapedwithnonlife-threateninginjuries
. The investigation (A13C0150) is ongoing. The investigationrevealed thatthe aircraft experienced a power loss toits leftengine (Honeywell TPE 331-11U-611G). Flight datarecorder informationindicatedthat an asymmetric thrust condition developed as a resultofthe power loss and continueduntil the flight crew lost controloftheaircraft. The left engine was not feathered. When the aircraftwas originally certified under FederalAviation Regulations 23-149, there was no requirementto publish a minimum control speedfor the aircraftinthe landing configuration
. Duringthe investigation, in-flighttesting was conducted atvarious airspeeds and aircraft configurations
. The results suggest thatthis aircraft type canbecome unstable in the landing configuration at airspeeds above Vmc when an enginefails and the propelleris notfeathered
. The SA227AC propeller systemincorporates a Negative Torque SensingSystem (NTS) which provjdes cyclical anti-drag andnegative torque protectionfor the engine if a negative torque conditionis sensed. Itis importanttonote thatunder certainconditions, such as an incomplete 

# Canada-2- engine shutdown or certain aircraft configuration, NTS activationparameters may notbe reached. Other types of aircraft also use a similar NTS. The investigation revealed that several SA 227/SA 226 trainingmanuals provide descriptions of the NTS thatmightcause pilots to interpret the description of the system as one thatwould automatically provide anti-dragprotectionin the event of anenginefailure or power loss. The NTS does provide partial anti-dragprotectionif a negative torque condition is sensed, butnot to the extent thatis providedby a fully feathered propeller. A misinterpretationby flight crews on the purpose or function ofthe NTS in an engine power-loss situation may lead them to believe that the NTS will always activate in the event of a power loss or thatNTS activation alone willprovide adequate anti-drag protection. As a result, flight crews may notinitiate the Engine Failure Inflight checklistin a timely manner. In a previous occurrence, A0900083, a Fairchild SA227-DC was onfinal approach to Runway 18 at the North Bay Airport (CYYB), Ontario, when the right engine (GarrettTPE331-12UHR) suddenlyfailed. Informationprovidedindicated that the failed engine's propeller NTS wasnot functioning after the engine failure and thatthe aircraft was difficult to control until the right propeller was feathered. In accordance with the TSB occurrence classification policy, the circumstances of the occurrence were assessed, and the occurrence was classified as a Class 5 occurrence. Consequently,TSB activity was limited to the collection of data, which has beenrecorded for safety analysis, statistical reporting, and archival purposes. There are currently 72 SA226/SA227 aircraft registered in Canada, with numerous others operatinginto Canadafrom the UnitedStates. Many other aircraft types equipped with a similar NTS may also be affected. ThereforeTransport Canada may wish to advise operators of these aircraft to review the NTS systems descriptionin their trainingmanuals and Standard Operating Procedures for engine failures. Particular attention shouldbe directed to flight crews operating these aircraft types to initiate standard operatingprocedures in a timely manner when an engine failure occurs. Yours sincerely,

MarkClitsome Director, Air Investigations Branch Encl. (1)
cc: Shari Currie, Director, Policy and Regulatory Services, TransportCanada John DeLisi, Director, Office of Aviation Safety, NTSB Tony Fazio, Director, Office of Accident Investigation and Prevention, FAA Marlin Kruse, Air SafetyInvestigator, Honeywell Aerospace Juan Garza, Senior Technical SupportRepresentative, M7Aerospace-3-

BACKGROUND INFORMATION
Occurrence No
. : A13C0150 This Safety Communication No
. : A13C0150-Dl-Al TSB Contact : IIC: Randy Vitt Phone: (204) 983-2565 Email: Randy.Vitt@tsb.gc
.ca

# Flight Test Protocol The safe conduct of the flight is of primary importance
1. Aircraft Limitations are not to be exceeded! 2. Attached is Flight Test Script that describes which exercises will be performed and evaluated! 3. Exercise will be terminated at the discretion of the PIC if undesirable conditions occurr. 4. There will be no Ad Hoc deviations from the script! 5. VFR Conditions must be maintained at all times 

### On Nov 10 2013 

### an SA227 crashed on landing at YRL shortly before landing. Atapprox. lj8th 

### mile onfinal the aircraft entered a roll to the left which apparently could not be corrected
. The aircraft veered offthe extended runway entre line and struck a tree with it's left wing tip then struck apower line and crashed into awooded area across the adjacent highway. The aircraft was destroyed by apost crashfire. Aircraft pilot will request a suitable block of airspace in which to conduct all exercises All exercises will be initiated from the top ofthe airspace block (eg 7000 feet) and will be completed with aircraft stable 2000 feet above the specified lower limit of the airspace block ( eg. 4000 feet ) Ground level will be considered to be 6000. FAF will be considered to be at 6600 AsL
. Time Up
___ 20:50Z_ Exercise 

### 1. Normal Ops TIME
___ ,21:06 Z_ Initiate a 700 FPM descent@ 130 KIAS, Flaps 

### Yz. At FAF (GOO AGL) gear down. At 500 feet simulate failure of the left engine. Identify failure , confirm, Stop and feather, carry out a normal overshoot as per SOP to top of airspace block. Torque Left 15% right 83% airspeed decreased to 122 Kts prior to recovery No recovery issues aircraft climbed out at approx 300 FPM

### Excercise 2. TIME
__ 21 :15Z
____ _ Initiate a 700 FPM descent@ 130 KIAS, Fl. At FAF (600 AGL} gear down. At 500 feet simulate failure ofthe left engine. left engine should be set 0 torque,( no NTS. pwr lver above flight idle) Apply Max power retract gear partially, then re select down
. Note any changes in roll or yaw! AsI} Ltorqu 5% Right 82% ( all avbl at 6500

right engine should be set to 100 torque and 100% N1, should see airspeed 125 KIAS (will it maintain 125 kias?) Airspeed, decreased to approx 120 kts reduce right engine to 97 torque should see slight N1 fluctuation then settle at 100.5% and airspeed drop to 115 (hold for 8 sees)

Reduce right engine to 50 torque for 5 sees observe Airspeed drop to 104? can altitude be maintained at this power setting, what about roll? Airspeed decreased to 95

### Note terminate exercise if aircraft starts to roll excessively or rapid altitude loss is experienced Aspd Roll? Alt?

95 Aircraft rolled drastically to the left, exercise terminated at 35° Increase right engine to 98 torque? Roll? airspeed

Not attempted Exercise 3 TIME_21 :25Z.
____ _ Initiate a 700 FPM descent@ 130 KIAS, Flaps 

### Yz. At FAF (600 AGL) gear down. At 500 feet simulate failure ofthe left engine. Left engine 0 torque. pwr Lvr back to flight idle , Right engine set to 97 torque note airspeed. Torque right 0% Torque Left 84% (max achievable@ 7000 Asl) Airspeed 1Z2 K Reduce right engine pwr to SO torque? Airspeed decreased to 95 kts Roll Sharp roll to left, exercise terminate at 35° left bank Altitude Exercise 4 TIME.
____ 21:32Z.
____ _ Attempt to establish VMCI Initiate a 700 FPM descent@ 130 KIAS, Fl. At FAF (600 AGL) gear down, flaps full
. At 500 feet simulate failure of the left engine. left engine should be set 0 torque,( no NTS. pwr lever above flight idle) Right engine set to 100 torque Control aircraft, increase pitch , note airspeed at which excessive roll (spin or stall in encountered) Max control input achieved at approx 105 kts strt 

### & lvl,

### Approx Vmcl 

# = 105 kts

(f) VMcL, the minimum control speed during approach and landing with all engines operating, is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control ofthe aeroplane with that engine still inoperative, and maintain straight flight with an angle ofbank ofnot more than 5 degrees. VMcLL must be established with: (1) The aeroplane in the most critical configuration (or, at the option ofthe applicant, each configuration) for approach and landing with all engines operating; (2) The most unfavourable centre ofgravity; (3) The aeroplane trimmed for approach with all engines operating; (4) The most favourable weight, or, at the option ofthe applicant, as a function ofweight; (5) Forpropeller aeroplanes, the propeller ofthe inoperative engine in the position it achieves without pilot action, assuming the engine fails while at the power or thrust necessary to maintain a three degree approach path angle; and (6) Go-around power or thrust setting on the operating engine(s).
Flight Test Data CONFIG. 

## TQ TQ RPM RPMR ASPD 

## vs PITCH ROLL YAW L R L l.STD 15 83 122 +300 Ovrsht
2. Accident 5 82 98 100.5 120 5 50 98 100.5 < - 95 -50 +++ lef +++left Simm VMCL 0 82 105 Max cntrl input