The Mind-numbing Distraction of Cascading Aural Warnings
When Kenya Airways Flight 507 went missing in the early morning of Saturday, May 5, a search was initially mounted 250 kilometers (156 miles and 25 minutes) away from its 0005L takeoff point of Douala, along its eastward track towards Nairobi Kenya.
The six-month-old 737-800 (5Y-KYA) was assumed down along UA610, i.e. below its flight-planned upper airways track.
This search locale was predicated on an erroneously plotted brief Emergency Locator Transmitter (ELT) satellite signal received on the 406MHZ distress frequency.
The ELT is G activated by the de-celeratory forces of a crash. It should keep transmitting its position for many hours. However, in the case of a highly destructive accident, it might not. Also, if it is submerged, it will not.
The 5Y-KYA’s ELT gave one brief transmission burst and then ceased, presumably as the crater it had created rapidly filled with water from the torrential rain that had been pouring down as it took off from Douala, Cameroon. Douala was a regular refueling stopover on Flight 507’s route from Abidjan on the Cote d’Ivoire.
Alex Bayeck, an official with the Cameroon government, announced that the Nairobi-bound plane had gone down about 250km from Douala, the commercial capital of Cameroon.
The search thereafter moved closer with each announcement, but initially to a rugged, forested area near the town of Lolodorf, about 140km (90 miles) southeast of Douala.
It wasn’t until some 40 plus hours had elapsed that the search was redirected well back towards Douala. The impact crater, a half wingspan wide, was finally found in swampland just over 5kms from the runway’s end. “We are talking about 30 seconds, so it had only just lifted off,” Kenya Airways chief pilot Captain James Ouma told a news conference in Nairobi on May 8.
He gave the precise location of the site as just 5.42km (less than three runway lengths) from the end of the runway in the dense mangrove forest. Local fishermen had eventually led airport workers to the crash site. There were no survivors among the 105 passengers and nine crew. The aircraft had taken off an hour late due to a drenching thunderstorm.
Whatever pressure the crew had been put under to eventually take off into the torrential rain may come out in the investigation (pilots’ duty hours limit?). Douala airport has no ATC or weather radar. Weather avoidance would’ve been solely reliant upon the crew’s interpretation of their onboard weather radar just before rolling and just after becoming airborne.
Contrary to newspaper reports, the Flt 507 pilots had made no routine or emergency transmissions after acknowledging their takeoff clearance. The aircraft’s flight data recorder was recovered from the crater on May 8. It is a modern digital device with hundreds of parameters recorded (U.S. FAA’s regs require a minimum of 88).
The device will go to the U.S. NTSB’s laboratory for analysis, together with the voice recorder (if and when recovered). An NTSB GO-Team with Boeing representatives is assisting the Cameroon authorities. However, Kenyan officials said that they wanted “neutral” Canada to analyze the plane’s black boxes, but acknowledged the decision would be made by Cameroon.
Initial NTSB conjecture has centered on the 737’s two engines flaming out due to the torrential downpour, and the aircraft having attempted to glide back to Douala. The location of the crash site makes that scenario unlikely, although an Indonesian 737-300 of Garuda did lose both engines in a thunderstorm on Jan. 16, 2002, landing in the Bengawan Solo River with the loss of one crewmember through drowning.
However, that crew, of Flt GA421, had gone against “the book” and selected a flight idle power setting for their descent. That wouldn’t have been the case for 5Y-KYA. Its event was on climb-out at a high power.
Similar 737 flame extinction occurrences (Boeing 737-300 double engine flameout while descending in heavy precipitation with engines at flight idle) happened May 24, 1988 and July 26, 1988. Following these incidents OMB 88-5 and AD 6-14-88 were issued to require a minimum rpm of 45% and to restrict the use of autothrust in moderate/heavy precipitation; engine modification was provided for increased capacity of water ingestion. Later, on August 31, 2005, the U.S. NTSB recommended that the FAA:
1. Complete the review of the current turbofan engine certification standards for rain and hail ingestion, and, if necessary, revise the standards in consideration of recent service experience and atmospheric data. (rec A-05-19)
2. Require that all turbofan engine and turbofan-powered aircraft manufacturers, working with operators of such aircraft, develop effective operational strategies and related guidance materials and flight manual warnings to minimize the chance of a dual-engine power loss (rec A-05-20).
A video of the Water Ingestion Test to which engines are subjected can be viewed at tinyurl.com/3x5ex6 (Quicktime req’d). A video of the Hailstone Ingestion Test is at tinyurl.com/2l7h49 and the Icing Ingestion Test is at tinyurl.com/2rqhz2.
The Federal Aviation Regulation FAR 33.77 Water Ingestion Test specifies that a water volume, up to 4% of the total intake air, be injected into the engine without flame extinction. That is far heavier by volume than the heaviest rain. FAR 33.68 (Induction System Icing) requires that engines be exposed to a water spray at sub-zero temperatures to ensure that they will not stall when exposed to nose-wheel side-spray or ice.
It is highly unlikely that a double engine flame-out could have occurred, although an engine failure with the crew mistakenly closing down the good engine is an outside possibility.
The most recent Airworthiness Directive (AD) on the 737-800 warns of a spate of spoiler problems: “Boeing and spoiler actuator manufacturer Smiths Aerospace are replacing the supplier’s part on all 37 Boeing 737-800 short-field performance (SFP) aircraft in service and on the production line to prevent possible failures that the FAA says could cause a loss of control on take-off.”
The emergency airworthiness directive issued by the FAA in March requires crew or qualified personnel to visually verify that spoilers are stowed after every landing or rejected take-off and after any maintenance that deploys the actuators.
The measure was prompted by at least two “hardover” failures, or jamming in the up position, being reported. Such a failure could cause “significant roll and consequent loss of control of the airplane”, said the FAA’s descriptor.
The real danger? The takeoff configuration warning will not sound if any flight spoiler remains extended with the speedbrake handle in the DOWN position (i.e., if it happened on landing at Douala and then, as it was dark at the time of departure and bad weather, it could have been missed on the pilot’s walkaround preflight check).
The AD allowed operators to waive the visual inspections by replacing all eight actuators on the 737, an action the regulator said it may ultimately decide to mandate. Boeing has so far replaced spoiler actuators on nine aircraft, and plans to finish the remainder by the end of summer. However, as far as is known, 5Y-KYA was not an SFP model.
In recent memory, we have witnessed the fumblings of a government with no idea of their carrier’s airliner crash site (Adam Air Flt 574 on Jan. 1).
This sorry situation seems no different in Africa. Thus far the Flight KQ507 crash bears remarkable similarity to the thunderstorm-related downings of an ADC Airlines 737-200 on Oct. 22, 2006 at Abuja, Nigeria (tinyurl.com/39fesn) and a 737-200 model of Bellview Airlines (Flt 210) on departure from Lagos on Oct. 22, 2005.
The Bellview plane was first reported found the next morning by a police helicopter search team near the rural town of Kishi, Oyo state, 400km (320 miles) from Lagos. Rescue helicopters were dispatched to that area but found no trace. A local government official Adeola Oloko described the scene for national radio and claimed that at least 50 of the 117 onboard had survived.
Many hours later, a TV crew working on some relayed garbled messages went to a site near the village of Lissa, about 20 miles North of Lagos, along the aircraft’s departure route and discovered the actual wreckage. The impact crater in swampland had in similar fashion immersed and killed off the tail-mounted ELT’s signal.
Flight 210 had taken off from Lagos on the Saturday night, then lost contact with the control tower during a heavy electrical storm. The Bellview Report is still awaited. Like Kenya Airways, up until the Bellview crash, that airline had enjoyed a reputation for over 12 years as being one of the safest and most reliable of Nigerian airlines.
The airline was used by U.S. embassy staff and one U.S. consular official died in the crash. Six months earlier, a Bellview Airlines domestic 737 flight had returned shortly after take-off, but without drama, from the northern city of Kano after declaring an emergency because of an uncontrollable engine fire.
The Kenya Airways (KQ) website says its fleet is 23 strong. KQ is 26 percent-owned by Air France KLM’s Dutch company KLM, which happens to be the world’s oldest airline, with a sturdy and well-deserved reputation for safety.
This crash is the first for Kenya Airways in seven years of safety-challenging African operations. Its last crash, also in western Africa, claimed 169 lives (see ASW Feb. 7, 2005 or tinyurl.com/yrye98). In that accident at Abidjan, an angle-of-attack transmitter on the fuselage side of an A310 had been damaged on the ramp but not reported.
After lift-off, due to the damaged sensor, the stall warning sounded and the stick-shaker operated. At around 300 feet, the first officer pushed forward slightly on the control column to increase speed and escape the stall. However, the Ground Proximity Warning System (GPWS) then cooked off, followed by the Continuous Repetitive Chime (CRC), which corresponds to a master warning of over-speed with flaps extended.
At the same time, the non-flying captain was shouting at him to “go up”. At that point, despite the radar altimeter call-outs, the F/O was well into task, information and sensory overload and flew the airplane into the darkened ocean just off the end of the runway. The gear and flaps were still down.
The investigation found that the crew had not taken the correct prompt recovery action: “At the first sign of an imminent stall or at the time of a stick shaker activation, the following actions must be undertaken simultaneously: thrust levers in TOGA position, reduction of pitch attitude, wings level, check that speed brakes are retracted.
The investigation showed that the pilot flying reduced the pitch attitude but did not apply TOGA thrust on the engines.” Apart from it being a dark moonless night, it was found that: “…the pilot flying’s action on the control column put the airplane into a descent without the crew realizing it, despite the radio altimeter callouts.”
The GPWS warnings that could have alerted the crew to an imminent contact with the sea were masked by the priority stall and overspeed warnings, in accordance with the rules on the prioritization of warnings. The drag of the gear and flap being left down didn’t help at all either. There was no simulator sequence in the syllabus that exposed flight-crews to this intellectually challenging smorgasbord of irruptions.
There’s a slow dawning realization that, as in Indonesia, it’s not the airplanes and it’s not the geography (Africa), but it may well be that the dismal accident record is attributable to the pilots, both their CRM indoctrination and their training.
Even amid the hoots, cackles and wails of an automated system, “Power plus attitude still equals performance” and a “cleanup” of gear and flap is taught at flight school as part of a stall recovery.
It’s an old saw, but one that must be trained for. It’s unlikely to be recalled and enacted amid a cacophony of cascading extraneous aural and visual inputs, unless your instincts are honed for the survival priorities.
It’s likely that the May KQ507 accident at Douala will prove to have had a similar daft prelude, complete with the distracting and unhelpful flashers, bells and whistles. It’s an atmosphere conducive to panic and well lacking the “sounds of a useful silence.”