AVIATION Reports - 1999 - A99A0100

2.0 Analysis (cont'd)

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2.1 Pre-flight

The pre-flight preparations were completed in accordance with normal procedures. The crew had all appropriate documentation required for the flight, and the aircraft was dispatched in accordance with company policy. The performance calculations showed that a safe landing could be effected in St. John's, despite the displaced threshold and the unserviceable lift dumpers. Furthermore, an uneventful flight in similar conditions had been made earlier that day. The captain's decision to conduct the flight to St. John's was informed and reasonable.

2.2 Approach

Before the approach, the crew had considered flying the approach to Runway 34. This would have provided the following advantages: a 300-foot lower MDA, visual vertical guidance to the threshold, a closer approach to the runway end, standard approach lighting, and standard runway touchdown zone markings. These advantages would have allowed a more stable approach and would also have allowed the crew to more easily acquire and fly a constant 3º approach angle from MDA to touchdown.During the final approach to Runway 16, there were deviations from the recommended airspeeds and required altitudes, and the approach flown was steeper than normal. When the decision to land was made, the aircraft was above the recommended airspeed and was 1 nm from the displaced threshold. The pilot assessed that he could continue the approach and arrive at the threshold at the required parameters. To achieve the required profile, the aircraft was placed on a steep descent in a low-energy regime. The steep descent and the manual silencing of the GPWS were not in accordance with company SOPs. The ability to perform a balked landing or a go-around was reduced by the low-energy state of the aircraft. At the displaced threshold, the aircraft was 35 feet higher and 18 knots faster than the recommended crossing height and airspeed.

2.3 Approach Lighting Standards and Recommended Practices

The recommended practice in TP312 to provide a VASIS to temporarily displaced thresholds is meant to lessen the risks associated with approaches to a non-standard landing environment. A displaced threshold increases the risk because the visual cues that a pilot would normally rely on to judge the approach to landing are frequently absent or may be misleading. The stopping distance available is also shortened. A VASIS would have assisted the pilot in maintaining the correct glidepath to the touchdown point.

2.4 Landing Roll

The deceleration data provided by the FDR showed that the aircraft did not decelerate in a similar manner to a flight landing on the same runway in St. John's earlier that day in similar conditions. Further, representative flights flown in a flight simulator consistently showed that the aircraft was capable of stopping within the confines of the shortened runway. Therefore, extensive testing of the brake system was carried out, and a comprehensive evaluation of the runway condition was undertaken to assess why the landing roll carried the aircraft beyond the end of the runway.For dynamic hydroplaning to occur, the water had to have been deeper than the tread channel. No standing water was observed after the accident, and the tires were in good condition with good tread depth. It is reasonable to conclude that dynamic hydroplaning did not occur. The extent to which viscous hydroplaning and/or reverted rubber skidding contributed to the lack of wheel braking could not be determined; however the conditions necessary for either were present, and there are indications for the occurrence of both. The lack of effective wheel braking during the application of normal braking is consistent with viscous hydroplaning, as is the negligible turning force displayed during yaw excursions on the landing roll. However, on the previous flight into St. John's, the same runway was used successfully under similar operating and environmental conditions, and no viscous hydroplaning occurred. This suggests that a successful landing should have been possible without encountering viscous hydroplaning. The damage to the tires indicates reverted rubber skidding during the alternate braking attempt and that the alternate braking system was functioning.

2.5 Braking

FDR analysis and performance calculations suggest that there was sufficient weight on wheels for the ground/flight relays to switch to the 'ground' position within four seconds of touchdown. FDR data also suggest that main wheel spin-up occurred shortly after touchdown. With these two parameters met, the normal braking system should have been available to the crew shortly after the aircraft touched down. The application of the alternate braking system caused the wheels to lock and resulted in the flat spots found on each tire. The locked wheels indicate that the alternate braking system was functioning. The lack of any discernable increase in deceleration indicates that poor braking conditions prevailed.It is possible that the normal braking system was functional during the landing roll but that effective wheel braking was unavailable due to a unique combination of factors, such as the following: reduced weight on wheels due to lack of lift dumpers, thus delaying the completion of locked-wheel touchdown protection circuits; antiskid cycling during viscous hydroplaning; reverted rubber skidding after the application of the alternate braking system; and the reduced braking to the right-hand inboard wheel. The extent to which any of these factors contributed to the lack of braking could not be determined.

2.6 Passenger Safety

2.6.1 Flight Attendant Actions

The flight attendants had no warning of the overrun yet surmised that an overrun was likely. Their commands to "brace" while still on the runway were entirely appropriate and demonstrated a high level of situational awareness. Their actions likely helped reduce the incidence of injury among the passengers.

2.6.2 Configuration of Flight Attendant Stations

The PA/interphone and the emergency light switch were not within reach of the forward flight attendant while seated. The PA system was not available to the aft flight attendant. While these conditions did not result in an adverse consequence in this occurrence, they represent a risk to passenger safety.Not all passengers could hear the "brace" commands issued by the flight attendants. The forward flight attendant's forward-facing seat resulted in her voice projecting forward, away from the passengers seated behind her, which is likely why the passengers had difficulty hearing her commands. The jump seat location and orientation are not unique to this aircraft. The aft flight attendant's commands were more audible; her jump seat, at the rear of the aircraft, was forward-facing. The high level of ambient noise created during the overrun further masked the flight attendants' commands.The aft flight attendant has no means to communicate with other cabin crew or the cockpit crew regarding commands or the status of the aircraft. In this occurrence, the aft flight attendant had no means to determine whether an evacuation or a rapid deplaning was required. It is important that the cabin crew know which commands are issued because these two commands require very different procedures.

2.6.3 Evacuation

The evacuation was conducted in an orderly and prompt fashion. It was, however, delayed slightly by miscommunication between the cockpit and the cabin and by the partially opened L1 door. This delay did not result in adverse consequences to the passengers or the crew.

2.6.4 Post-evacuation

The immediate response to the occurrence was prompt and effective. The tower controller expedited the emergency response by activating the airfield crash alarm before the overrun. The delayed provision of additional ambulance response and passenger transport did not result in adverse consequences in this instance; however, these factors could be critical in a more serious accident.

3.0 Conclusions

3.1 Findings as to Causes and Contributing Factors

1. The aircraft could not be stopped on the runway because wheel braking was not effective.
2. The following factors might have contributed to the lack of effective wheel braking: delayed completion of locked-wheel touchdown protection circuits; antiskid cycling during viscous hydroplaning; reverted rubber skidding after the application of the alternate braking system; and the reduced braking to the right inboard wheel during normal brake application. The extent to which any of these factors contributed to the lack of deceleration could not be determined.

3.2 Findings as to Risk

1. A visual approach slope indicator system (VASIS) was not provided for the final approach to the displaced threshold, increasing the difficulty of visually acquiring and flying the final approach.
2. The ability to perform a balked landing or a go-around on final approach was reduced by the aircraft's low-energy state.
3. Miscommunication during the initial stages of the evacuation delayed the evacuation slightly.
4. Flight attendants did not have access to communications equipment from their seated stations, increasing the risk of miscommunication or delay.
5. There was a 40-minute delay in the provision of back-up ambulance support and passenger transportation.

3.3 Other Findings

1. Performance calculations showed that Runway 16 at St. John's, with the displaced threshold, was of sufficient length to land the aircraft.
2. The approach to Runway 34 would have provided a superior approach and landing environment.
3. No antiskid/brake system anomalies were found that would have resulted in a total lack of wheel braking.
4. The flat spots on each of the tires were due to locked wheels during the application of alternate braking.
5. Engine starts are not captured on the F28 flight data recorder because company standard operating procedures state that flight control locks, which control the starting of the flight data recorder, be released after engine start.
6. Debris on the overrun area was a major contributing factor in the nose-wheel collapse.

4.0 Safety Action

4.1 Action Taken

4.1.1 Approach Lighting Standards and Recommended Practices

On 15 October 1999, the TSB forwarded an aviation safety advisory to Transport Canada (TC) asking that TC consider means of further encouraging or requiring visual approach slope indicator systems (VASIS) at Canadian airports. TC's response on 03 April 2000 indicated support for broader application of VASIS. Before undertaking a complete regulatory review of the Aerodrome Standards, TC will recommend to the Part III Canadian Aviation Regulations Advisory Committee that paragraph 5.3.6.2 of Aerodrome Standards and Recommended Practices (TP312) be upgraded from a recommendation to a standard. The regional managers of Aerodrome Safety have been advised of the concerns raised by this advisory. They are additionally requested to consider these findings while processing the approval of airport construction plans.

4.1.2 Emergency Response - Secondary Vehicles

On 02 March 2000, the TSB forwarded an aviation safety advisory to TC suggesting that airport operators and applicable agencies review their emergency response plans with the view to ensuring the prompt provision of back-up and secondary emergency response vehicles. TC's response on 10 May 2000 indicated that a major revision to Part III of the Canadian Aviation Regulations (CARs) is expected to lead to the inclusion of material that is currently available only as guidance material. One such subject area to be affected is the emergency planning requirements. The TSB advisory will be considered in this CARs revision process. TC has also indicated that observed system deficiencies will be distributed to all airport operators to encourage evaluation of their own program shortcomings. Civil Aviation, Atlantic Region, has already taken action in this regard by distributing a letter to airport operators of that region, recommending that they add to their emergency response plan a section addressing transportation of uninjured passengers in the absence of on-site airline representatives.A notice of proposed amendment (NPA 2000-244) titled "Airport Emergency Planning Standard" is presently before the Department of Justice.St. John's airport has purchased a bus to ensure that passenger transport is available during emergencies. St. John's airport and the Health Care Corporation of St. John's (the ambulance provider) have revised their communication procedures to ensure direct communication during emergencies. The ambulance provider will no longer be notified of an emergency through a third party (the 911 operator). Communications will be direct from the control tower to the ambulance provider and will include more information to determine the potential resources required. In addition, the Health Care Corporation of St. John's has implemented a new on-call system that provides a representative for immediate response to airport emergencies.

This report concludes the Transportation Safety Board's investigation into this occurrence. Consequently, the Board authorized the release of this report on 12 February 2002.

5.0 Appendices

Appendix A - Schematic of Landing

Appendix B - List of Supporting Reports

The following TSB Engineering Laboratory Reports were completed:LP 88/99 - Flight Recorders and Aircraft Performance Analysis LP 096/99 - Examination of TiresThese reports are available upon request from the Transportation Safety Board of Canada.

Appendix C - Glossary

ADT	Atlantic daylight time
agl	above ground level
asl	above sea level
ATPL	Airline Transport Pilot Licence
CARs	Canadian Aviation Regulations
deg	degrees
FDR	flight data recorder
fpm	feet per minute
ft	feet
GPWS	ground proximity warning system
hdg	heading
hr	hour
ICN	Inter-Canadien
KIAS	knots indicated airspeed
MDA	minimum descent altitude
min	minute
NDT	Newfoundland daylight time
nm	nautical mile
P1	pilot
P2	co-pilot
PA	public address system
Rwy	runway
sec	second
SFT	surface friction tester
SOPs	standard operating procedures
SPECI	aviation special weather report
TC	Transport Canada
TSB	Transportation Safety Board of Canada
Vref	reference speed
VASIS	visual approach slope indicator system
º	degree(s)
ºM	degree(s) magnetic

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1. All subsequent times are NDT (Coordinated Universal Time minus two and one-half hours).

2. TSB Report Nos. A95H0015 and A94C0034.

3. Canadian Regional, Standard Operating Procedures for the F28, paragraph 3.5.7.g, 1996, pp. 58-59.

4. Transport Canada, AIP Canada, section AIR, paragraph 1.6.5, TP2300.

5. Charles E. Dole, Flight Theory for Pilots, 2nd ed., Institute of Safety and Safety Management, University of Southern California, USA.