Description

On 19 October 2022, the First Officer on a de Havilland DHC8-300 (C-GJYZ) being operated by Perimeter Aviation on a scheduled domestic passenger flight from Pikangikum to Sandy Lake as JV464 flew an unstabilised approach at the destination in night VMC and then mishandled the landing attempt after which the Captain took over control. Substantial damage was caused to the lower aft fuselage structure by the tailstrike but there were no confirmed injuries to the 31 occupants.

Investigation

An Accident Investigation was carried out by the Canadian Transportation Safety Board. The FDR and CVR were removed from the aircraft and their data were successfully downloaded. FMS computer NVM data were also downloaded from the aircraft.

The Captain had a total of 7,721 hours flying experience including 3,233 hours on the DHC8. He had joined Perimeter Aviation as a First Officer 3½ months prior to the accident and after 20 hours initial company training had passed his LPC and commenced line training in that rank. He had been checked out as a First Officer after 69 hours of line training (minimum required 20 hours) following which he had been promoted to Captain. In that rank, he had then completed 126 hours line training (minimum required 20 hours) before being released to fly in command. The accident flight was the first sector of his second day in command.

The First Officer had a total of 2,368 hours flying experience all but the 105 hours acquired since joining Perimeter Aviation 2½ months prior to the accident having only previously flown single engine aircraft, in almost all cases the Cessna 172. He completed 13 hours initial company training to pass his LPC and then completed 74 hours line training (minimum required 20 hours) before being released to fly without training supervision. The accident flight was the first sector of his third day unsupervised having accumulated 18½ hours in that time.

It was noted that the company OM did not include any restrictions on pairing of type-inexperienced pilots and that the regulatory requirements in that respect had already been satisfied by their extended periods of supervised line training. However, the operator’s monthly pilot roster was subject to management approval and had not initially rostered the two pilots to fly together because of “an informal practice of not scheduling pilots with limited experience in their roles on the same flight”. A subsequent change was then made during a daily reschedule by the Senior OCC Duty Manager as this “informal daily scheduling practice” took no account of experience when pairing pilots to operate together at short notice.

What Happened

The departure of the flight was delayed by three hours. It eventually departed Pikangikum for the half hour flight to Sandy Lake with the First Officer acting as PF and climbed to 7,000 feet QNH. A visual approach was planned at Sandy Lake with the LPV approach procedure to be followed. There was a brief discussion about the APAPI installed at Sandy Lake, where the 1069 metre-long, 30 metre-wide gravel runway was classified as a ‘short runway’ by Perimeter Aviation requiring a short-field landing technique to cross the threshold at around 30 feet agl instead of the normal 50 feet agl. Shortly before descent was commenced an ‘LPV APPR INHIBITED’ message was annunciated but given that VMC prevailed, this did not create any problems. The final approach track was joined at 10nm and the aircraft briefly levelled at 4,000 feet QNH (the airport elevation was 946 feet), before descent was commenced about 500 feet above the 3.29° APAPI approach angle.

When 3nm from the runway threshold at 120 KCAS (and at 1,350 feet aal, the aircraft was still 300 feet above the APAPI slope guidance), the power was set to 15% torque, the propeller levers were set to 1,200 fpm, the flaps were set to 15° and the landing gear was selected down. One minute later, passing the 500 feet agl stabilised approach gate applicable to all approaches, with 1.2nm to go and descending at 900 fpm, the Captain announced that the approach was stable “and advised the First Officer to maintain the descent profile”. However, he simultaneously reduced the rate of descent to 500 fpm and increased engine torque.

The Captain mentioned the APAPI indication and cautioned that “an adjustment needed to be made to maintain the correct approach path”. Just over half a minute later, with the aircraft still above the APAPI approach slope and just over half a mile from the runway, the First Officer returned the engine torque to approximately 10%. As the aircraft reached the APAPI approach slope, the First Officer increased the torque from 10% to almost 60% which reduced the rate of descent to approximately 160 fpm. With just 0.2 nm to go, the First Officer then reduced the power levers to flight idle - approximately 0% torque - and decreased the aircraft pitch angle by 2°.

During the subsequent flare, the First Officer attempted to reduce the excessive rate of descent he had created by making “a pronounced pitch-up control input” as the torque “began to gradually increase from flight idle”. The main landing gear then touched down 350 feet past the threshold at a 950 fpm rate of descent with the maximum recorded vertical acceleration of 3.61g recorded as the oleos compressed and the aircraft’s aft fuselage struck the runway surface with the pitch angle recorded as 7.24°. The aircraft bounced to approximately 1.5 feet and as it touched down for a second time, the Captain saw that the ‘TOUCHED RUNWAY’ indicator had illuminated. When, moments later, the First Officer called for a go-around and began to increase power, the Captain took control and brought the aircraft to a stop with only 150 metres of runway remaining and then taxied it to the apron.

Substantial lower rear fuselage structural damage was subsequently identified including airframe structure interior buckling where impact had occurred (as shown below). All main landing gear load-absorbing components were also replaced.

Buckled Structure beneath the floorboards above the missing external tail strike switch. [Reproduced from the Official Report]

Why It Happened

The unstabilised approach which preceded the mismanaged landing was examined against relevant company requirements and guidance. It was noted that there were no regulatory requirements in respect of stabilised approaches although such approaches are “recommended”. However, it was found that ‘Stabilised Constant Descent Angle’ (SCDA) training was in place and included in the DHC8 fleet’s FCTM. A 500 feet agl requirement for all approaches to be stabilised was defined as including a rate of descent of not more than 1,000 fpm without a special briefing and a power setting “appropriate for the aircraft configuration and not below the minimum power for the approach” as defined by the OM, for which no such definition was found in that Manual.

It was noted that the closest recommended power setting mentioned in the SOP in respect of the conditions at the time of the investigated event was “a power setting of 10% torque, the flaps set to 15°, both engines operating and an aircraft speed of 120 knots” which it was stated “would result in a 1,000 fpm rate of descent”. Once below 500 feet agl, the SOPs required that “only minimal adjustments should be made to the power lever settings, and the aircraft should be trimmed for the appropriate energy state so that (it) follows a consistent path”.

In respect of the immediate prelude to touchdown for the flap 15° approach flown, it was found that the SOPs stated that when the aircraft is 20 feet above touchdown, the pilot should “smoothly bring the aircraft nose up into the flare, while reducing power as required allowing the aircraft to descend to the runway” and advised that “during the flare, the pitch attitude change is approximately 4° or 5°” i.e. from approximately 0° to 1° nose up to 4° to 5° nose up. The required (tailstrike prevention) pitch awareness calls at 5° and 6° were not made.

In respect of the visual approach flown without the original intended but unavailable LPV vertical profile available, it was noted that the operator’s pilots were not provided with any guidance on the conduct of visual ‘straight in’ approaches nor was a VFR descent profile published, only a VFR Circuit profile.

In respect of the operator’s use of periods of line training for both the pilots involved, which were between three and more than six times more than the minimum required, this could reasonably be attributed to their lack of experience in the roles for which they were eventually assessed competent. However, the context for this assumption was that only 75% of the budgeted roster of 40 Captains and 44 First Officers to operate 12 DHC-8 aircraft were employed. It was also noted that in the 12 months prior to the accident, there had been “a significant turnover of company DHC-8 pilots” with 34 pilots having left the company with only 18, including the two flying the accident aircraft, having been recruited to replace them.

To provide a perspective for the accident, the way the aircraft type was being operated was examined using the FDR data for a total of 246 flights. The maximum pitch attitude during the landing flare was determined for each of these flights and the results plotted (see below). Although the SOPs stated that the pitch should not exceed 6° during the flare to avoid the risk of a tail strike, the data showed that it did so in almost 9% of landings when a hard landing at 7° pitch attitude will depress the main gear oleos sufficiently, as in this case, to cause a tail strike. It was observed that the fact that the operator relied entirely on pilots self reporting deviations from prescribed SOPs meant that only such deviations which had visible consequences were likely to be reported.

The operational safety oversight process of the Perimeter Aviation operation at the time of the accident was found to have been ineffective with a systemically ineffective but Regulator-approved SMS which was not tracking risk in everyday operations despite the fact that this was strongly recommended (although not a regulatory requirement). The absence of a recommended but not required OFDM programme was also highlighted as a particular missed opportunity to ensure operational risk awareness and thus proactively manage risk by ensuring SOPs are fit for process and compliance can be monitored.

Reproduced from the Official Report

The following Findings were formally documented based upon completion of the investigative work:

Causes and Contributing Factors

1. Below 500 feet above ground level and while trying to intercept and maintain the appropriate approach path, the pilot flying varied the power setting between 57% and flight idle, likely owing to limited experience operating the aircraft type, and the result was an unstable approach.
2. Due to insufficient detail in the standard operating procedures and the absence of awareness training on stabilized approach criteria, the pilots did not recognise that significant variations in the power setting had made the approach unstable, and they continued the approach.
3. The pilot flying, who was relatively inexperienced on the DHC-8 and had received limited guidance on pitch awareness, made a pronounced pitch-up input during the flare. There was insufficient time for the pilot monitoring to arrest this action, and the aircraft’s aft fuselage consequently contacted the runway, causing significant damage.

Risk Factors [Safety deficiencies which were assessed not to have been a factor in this occurrence but could be in future ones]

1. If an air operator does not factor a pilot’s level of experience into a formal daily crew scheduling process, there is a risk of compromised safety margins due to the assignment of two pilots with limited experience in their roles to operate the same flight.
2. If air operators rely solely on flight crews to report hazards and risks to the company’s safety management system and do not actively monitor flight operations through flight data-monitoring capabilities, unsafe practices may not be identified, increasing the risk that they will continue.

Safety Action taken by Perimeter Aviation as a result of the accident was noted at the conclusion of the Investigation as having included the following:

• incorporated the “Dash 8-Q400 Pitch Awareness” video in its initial and recurrent cockpit procedures training for the DHC-8-100 and DHC-8-300 series and made the video available for instructors to share;
• amended the DHC-8 standard operating procedures (SOPs) to revise its stabilised approach criteria to include target power settings, and added information and guidance regarding the flight management system’s “LPV APPR INHIBITED” error message;
• amended the SOPs for the DHC-8, SA227, and SA226 to include an instrument approach policy that requires flight crews to fly the instrument approach procedure for the intended runway, if one is available, regardless of weather conditions, to assist in ensuring a stabilised flight profile;
• developed flight operations quality assurance and line operations safety audit procedures;
• added this occurrence to the company’s crew resource management course;
• implemented a command and decision making course;
• amended DHC-8 initial simulator training to include excessive pitch recovery and black hole exercises;
• implemented a restricted crew status list;
• instituted a flight data monitoring program for its DHC-8 and SA227 AC fleet.

The Final Report of the Investigation was authorised for release on 27 March 2024 and officially released on 21 May 2024. No Safety Recommendations were made.

Related Articles

• Stabilised Approach
• Tail Strike
• Hard Landing
• Low Level Go Around (SKY Clip) 
• Safety Management System
• Flight Data Monitoring (FDM)
• Risk Management
• Safety Oversight
• Standard Operating Procedures (SOPs)