Reply by Deputy Prime Minister and Minister For Defence to Parliamentary Questions on Emergency Landing of Apache AH-64 Helicopter

Mr Speaker, Sir, may I have your permission to take Er Lee Bee Wah, Mr Michael Palmer, Mr Low Thia Khiang and Associate Professor Paulin Tay's questions together.

MINDEF has carried out investigations with the aircraft and engine manufacturers into the cause of the loss of power in both engines which led to the incident of the Apache landing in an open field. Following the incident, both engines were sent to the manufacturers for full tear-down and inspection. The manufacturers have identified a defective component which is present in both engines of the aircraft, which led to the loss of power and shut-down of both engines during flight.

The defective component is called the Anti-Ice Start Bleed Valve or AISBV for short. A corroded valve would lead to malfunctioning of the guide vanes that channel air to the aircraft engine. The disruption of airflow to the engine would lead to the loss of engine power. The Anti-Ice Start Bleed Valve (AISBV) in both engines was found internally corroded when opened up by the manufacturer. The defect was caused by corrosion in the valve which occurred over time. The investigation then looked into why the AISBV was corroded and why the corrosion went undetected. We looked into whether there was a manufacturing defect or a maintenance error. Sir, the valves used in the RSAF Apache fleet are the same as those used by other Apache operators around the world. We have no evidence that there were manufacturing defects in these valves. We have also ascertained that the RSAF maintenance crews adhered to the required maintenance procedures specified by the manufacturer for the aircraft, including the AISBV. Prior to this, there were no reported incidents of the same nature. Currently, there are no stipulated maintenance checks that would allow such internal corrosion in the AISBV to be detected by the maintainers. The maintenance procedure does not call for the RSAF to open up the AISBV. This can be done only by the manufacturer. The aircraft operator, in our case the RSAF, needs to replace the AISBV only after a fault code appears in the aircraft computer during flight, or when running the engine on the ground for tests. The nature of the malfunction arising from the corrosion was not detected by the aircraft computer and therefore no fault code was generated. We are now studying, together with aircraft manufacturer, the maintenance procedures to see whether the maintenance procedures mandated by the manufacturer need to be modified so that corrosion which occurs inside this valve is prevented, or can be detected and corrected should it occur.

To ensure that our helicopters are fitted only with valves that operate properly, the RSAF will replace all existing valves with new ones, or valves that are re-certified by the manufacturer, and test the engines thoroughly before we clear each helicopter for flying. Having also reviewed and established that the RSAF's maintenance, flight and training safety procedures are sound, the Apache and the SeaHawk helicopters will progressively resume flying this week.

Mr Speaker, Sir, the RSAF maintains the highest standards of maintenance and flight safety. Let me now turn from the cause of the power loss in the engines, to how the RSAF's pilots are trained to handle emergencies. Training in emergencies is a key part of the training of all our pilots. In the event of an emergency, where possible, the aircraft will be flown back to the nearest air base immediately. If this is not feasible, the pilots will attempt a safe landing at the nearest open space. In doing so, the key priority is always to avoid populated areas. Safety to the populace has the highest priority and this is what the two pilots did in this incident. When they determined that they were not able to land at an air base, they considered their options, and found an open space away from buildings and populated areas, verified and confirmed that the field was clear of people, and then executed an emergency landing.

Any unused open plots of land or open fields are potential emergency landing sites for helicopters. Depending on the flight route of the helicopter, various open spaces are identified and briefed as part of the pre-flight procedures for that flight. This is carried out for all RSAF helicopter flights. Hence, it is not possible to identify any specific open spaces as designated emergency landing sites, as emergency landing sites depend on the flight routes being taken and where the emergency occurs. Our pilots are trained to ensure the safety of the public before making a decision to land in any of these open spaces, and they will forego such a landing even at risk to themselves if there is a danger to population.

Let me now turn to the issue of flight training in Singapore and the safety of our population. Mr Speaker, Sir, Singapore is densely populated and has limited airspace. The RSAF also has to share the tight airspace with civilian aircraft. Given these constraints, in addition to local training, the RSAF conducts training in overseas training areas as well as on simulators. The RSAF strikes an appropriate balance amongst these three forms of training. Local training is essential to maintain the proficiency of our Singapore based aircrew, and to ensure that all our pilots are familiar with the local operating environment. Overseas training is more costly but it helps address the airspace constraints our pilots face at home. Simulator training is a useful and effective component of pilot training to improve piloting and operational skills. It allows pilots of varying experience to be trained on aircraft handling under different operational scenarios, and this includes, in particular, training all our pilots on handling the various types of aircraft emergencies.

Mr Speaker, Sir, the safety of our populace is a top priority of MINDEF and the RSAF. We have thus taken steps to ensure that training flights over residential areas are minimised whenever possible, that they are conducted safely, and that they are in accordance to norms prescribed by international aviation bodies, such as the International Civil Aviation Organisation and the Federal Aviation Authority of the United States. These norms govern the minimum flying altitudes designed to ensure the safety of residents living in close proximity to air bases or airports or air fields. They are similar to those adopted in airports which operate in densely-populated cities, as well as where civilian helicopters are used for transportation in major cities and land on helipads on high-rise buildings in densely populated areas. So it is not uncommon for aircraft or helicopters, even civilian ones, to operate over densely populated areas.

While we cannot totally prevent machine failures from occurring, we will do our best to minimise the risk of such failures. The RSAF has in place a comprehensive maintenance programme to ensure the air worthiness of our aircraft. In addition, all our pilots undergo regular emergency aircraft training; and discussions on emergency procedures are carried out as part of every pre-flight preparation. This is to ensure that the pilots are able to respond quickly and professionally in order to minimise any risk posed to the public in the event of an aircraft emergency.

More Resources

Fact Sheet: Anti-Ice Start Bleed Valve (AISBV)