Transportation Safety Board 

of Canada 

200 Promenade du Portage 

Gatineau, Quebec 

K1A 1K8 

29 April2014 

Mr. Martin Eley 

Director General, Civil Aviation 

Transport Canada 

330 Sparks Street 

Place de Ville, Tower C 

5th Floor, Area A 

Ottawa, Ontario 

KlAONS 

Bureau de fa securite des transports 

du Canada 

r.. N.Dl.t "iN I / Our file Reference 

\......- (, 825-A13C0150-Dl-Al 

ll Lg(J .-- fr (..00~ r _J>d )(::., ,r "\ v '.... L.f?1 M e::-

~dv-..1 tP YDV 

( ~ ~.rvt. ~ ,0 {)0 

!fJl1tttN 6 

vJl1'1 ~5. 

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 of Aircraft with Negative Torque Sensing Systems 

Dear Mr. Eley, 

On 10 November 2013, Bearskin Airlines flight 311, a Swearingen SA227 AC (registration 

C-FFZN, serial number AC-785B), was conducting an instrument approach to Runway 26 at the 

Red Lake Airport (CYRL), Ontario. At 1827 Central Standard Time, the crew reported 5 miles 

on final for Runway 26. At 1828 while the aircraft was at approximately 500 feet above ground 

level and 1.5 nautical miles from the runway threshold, the crew declared an unspecified 

emergency. Shortly after, the aircraft veered to the left and struck trees and a power line 

approximately 800 meters south of the approach end of the runway. The aircraft was destroyed 

by impact forces and fire. Two crew members and 3 passengers sustained fatal injuries. Two 

passengers escaped with non life-threatening injuries. The investigation (A13C0150) is ongoing. 

The investigation revealed that the aircraft experienced a power loss to its left engine 

(Honeywell TPE 331-11U-611G). Flight data recorder information indicated that an asymmetric 

thrust condition developed as a result of the power loss and continued until the flight crew lost 

control of the aircraft. The left engine was not feathered. 

When the aircraft was originally certified under Federal Aviation Regulations 23-149, there was no 

requirement to publish a minimum control speed for the aircraft in the landing configuration. 

During the investigation, in-flight testing was conducted at various airspeeds and aircraft 

configurations. The results suggest that this aircraft type can become unstable in the landing 

configuration at airspeeds above Vmc when an engine fails and the propeller is not feathered. 

The SA227 AC propeller system incorporates a Negative Torque Sensing System (NTS) which 

provjdes cyclical anti-drag and negative torque protection for the engine if a negative torque 

condition is sensed. It is important to note that under certain conditions, such as an incomplete 

Canada 
-2-

engine shutdown or certain aircraft configuration, NTS activation parameters may not be 

reached. Other types of aircraft also use a similar NTS. 

The investigation revealed that several SA 227 /SA 226 training manuals provide descriptions of 

the NTS that might cause pilots to interpret the description of the system as one that would 

automatically provide anti-drag protection in the event of an engine failure or power loss. The 

NTS does provide partial anti-drag protection if a negative torque condition is sensed, but not 

to the extent that is provided by a fully feathered propeller. A misinterpretation by flight crews 

on the purpose or function of the 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 that NTS activation 

alone will provide adequate anti-drag protection. As a result, flight crews may not initiate the 

Engine Failure Inflight checklist in a timely manner. 

In a previous occurrence, A0900083, a Fairchild SA227-DC was on final approach to Runway 18 

at the North Bay Airport (CYYB), Ontario, when the right engine (GarrettTPE331-12UHR) 

suddenly failed. Information provided indicated that the failed engine's propeller NTS was not 

functioning after the engine failure and that the 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 been recorded for safety analysis, 

statistical reporting, and archival purposes. 

There are currently 72 SA226/SA227 aircraft registered in Canada, with numerous others 

operating into Canada from the United States. Many other aircraft types equipped with a 

similar NTS may also be affected. 

Therefore Transport Canada may wish to advise operators of these aircraft to review the NTS 

systems description in their training manuals and Standard Operating Procedures for engine 

failures. Particular attention should be directed to flight crews operating these aircraft types to 

initiate standard operating procedures in a timely manner when an engine failure occurs. 

Yours sincerely, 

Mark Clitsome 

Director, Air Investigations Branch 

Encl. (1) 

cc: Shari Currie, Director, Policy and Regulatory Services, Transport Canada 

John DeLisi, Director, Office of Aviation Safety, NTSB 

Tony Fazio, Director, Office of Accident Investigation and Prevention, FAA 

Marlin Kruse, Air Safety Investigator, Honeywell Aerospace 

Juan Garza, Senior Technical Support Representative, M7 Aerospace 
-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. At approx. lj8th 

mile on final the aircraft entered a roll to the left which apparently could not be corrected . The 

aircraft veered off the extended runway entre line and struck a tree with it's left wing tip then 

struck a power line and crashed into a wooded area across the adjacent highway. The aircraft 

was destroyed by a post crash fire. 

Aircraft pilot will request a suitable block of airspace in which to conduct all exercises 

All exercises will be initiated from the top of the 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. F AF 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 of the 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! 

As I} 

L torqu 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 of the 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 of not more than 5 degrees. VMcLL must be established with: 

(1) The aeroplane in the most critical configuration (or, at the option of the applicant, each 

configuration) for approach and landing with all engines operating; 

(2) The most unfavourable centre of gravity; 

(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) For propeller aeroplanes, the propeller of the 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