Gliding a B747 Out of Volcanic Ash

Fri, Apr 23, 2010 — David Evans


“Good evening, ladies and gentlemen. This is your captain speaking. We have a small problem. All four engines have stopped. We are all doing our damnedest to get them going again. I trust you are not in too much distress.”

This was the public address (PA) announcement made by Capt. Eric Moody to the 247 passengers of British Airways Flight 9, twenty eight years ago on 24 June, 1982. It was made a few moments after losing all four engines on the B747 after penetrating a cloud of volcanic ash at 37,000 feet.

What Moody did not know at the time was that Mt. Galunggung had erupted two hours before Flight 9’s nighttime takeoff from Kuala Lumpur, Malaysia, for the five-hour flight to Perth, Australia. The volcano, located some 110 miles southeast of Jakarta, had erupted for the ninth time that year, spewing an enormous cloud of ash high into the atmosphere, and into the path of Flight 9.

Mt. Galunggung erupts.

Mt. Galunggung erupts.

The geologic facts would be pieced together after the flight. At the moment of his brief address to the passengers, Moody did not know the precise nature of the emergency he was facing. First Officer Roger Greaves and Flight Engineer Barry Townley-Freeman were equally perplexed.

The crisis began innocuously. The weather radar showed the way ahead was clear. On autopilot, the airplane was cruising serenely. Moody excused himself from the cockpit to use the lavatory. Finding the upper deck toilet occupied, he descended to the main deck. During a brief chat with the purser, he was called to the flight deck. As he ascended the stairs, Moody recalled seeing smoke coming through the floor vents and noticing an “electrical burning smell.”

When he got to the cockpit, he immediately noticed a bright orange, red and blue display of St. Elmo’s Fire playing across the windscreen. Strapping himself into his seat, Moody noticed the display intensifying, momentarily distracting him from the source of smoke billowing out of the air conditioning vents. Sparks were flying off the nose and windscreen. The engines were glowing brightly from within, looking to Moody like a “magnesium fire.”

As the fireworks intensified, engine #4 started winding down. The engine fire drill was initiated. The fuel to engine #4 was cut off and the throttle was pulled back. Moody and crew stopped short of discharging Halon fire-extinguishing agent into the engine, as there was no fire indicated.

About 30 seconds later engine #2 failed. In a few more seconds, #3 was gone, followed by engine #1 quitting. Flight Engineer Townley-Freeman remarked, “Sorry, we’ve lost the lot.”

Now retired, Moody recalled, “Even though we’d trained for it at British Airways, and practiced it in the simulator, we didn’t believe what was happening.”

With the autopilot still engaged, the nose began to rise as speed decreased. (ASJ note: with all four engines flamed out, the autopilot would be trimming to fly level as the speed decreased. Ultimately, the aircraft would stall with full nose-up elevator trim, akin to what happens to turboprop airliners during undetected icing encounters and speed loss.)

“We turned to the left to avoid any oncoming aircraft on a reciprocal route and were heading to Java,” Moody said.

He ordered First Officer Greaves to put out a Mayday to air traffic control (ATC) at Jakarta. The airport was some 40 minutes flying time away.

“Jakarta, Mayday Speedbird 9. We’ve lost all four engines. We’re leaving [flight level] 370,” Greaves radioed.

He was transmitting through a tremendous amount of static. Fortunately, the message was repeated by a Singapore Airlines jet following Flight 9 by some 20 miles. Unfortunately, the message received by ATC was only that the #4 engine had failed, not ALL four.

“We could see the fans were rotating, that they weren’t locked up, so we put on both banks of igniters and anti-ice,” Moody remembered. (ASJ note: the windmilling fans showed a rotation of about 30% on the N1 gauges.) The fuel, though, was not igniting inside the engines, producing thrust, but rather was igniting behind the engines, treating passengers to a spectacular display of flames.

“I couldn’t see any cause, and remarked to the crew, ‘We’ve cocked something up,’ ” Moody said. Turning to look at the flight engineer’s panel, Moody saw readings of complete electrical loss.

Perhaps the engines failed from fuel mismanagement, which was the underlying reason for the all-engines-out drill for recurrent training. Pumps and cross feed valves were checked. Circuit breakers were checked. Engine anti-icing was checked.

Nothing seemed amiss.

Even though the Rolls Royce engines were most likely to restart in conditions below 29,000 feet and in a speed range of 250-270 knots, according to the engine manufacturer’s guidance, Moody and crew attempted to restart engines #1, #2 and #3 immediately as they began to descend from 37,000 feet. This activity, Moody said, “Was per our training, but we did not expect them to light up and, after a couple tries, they didn’t.”

Ash having clogged one or more pitot tubes, there was now a good 20-knot difference between the left and right airspeed indicators. The first officer’s instrument on the right displayed 270 knots. Moody’s airspeed gauge on the left showed 320 knots. “I had no idea which was the more accurate, mine or the first officers, as we only had a choice of two, so I varied the airspeed on both,” Moody said.

Now having dropped below their 37,000 foot cruise altitude, Moody recalled, “I thought we should reinstate #4.”

Meanwhile, without bleed air to maintain the artificial cabin altitude of 8,000 feet, the cabin altitude began to climb. The cabin pressurization alert sounded as the cabin altitude rose to 10,000 feet. The pilots donned oxygen masks. Or, at least two of the crewmen did. Greaves’ mask came apart in his lap, and he had to reconnect the oxygen supply tube to the mask before donning it.

As a guard against Greaves passing out from lack of oxygen, Moody disconnected the autopilot and pushed the nose over to dive the airplane to a lower altitude. The cabin altitude continued to climb. As it passed through 14,000 feet, the yellow supplementary oxygen cups deployed out of the passenger service units. However, the automatic announcement failed.

About this time, Moody recounted, he was thinking of having to ditch theairplane, and regretting that the £250 in his wallet might be lost to the briny deep.

It was at this moment when Moody made his PA announcement to the passengers, discreetly avoiding any mention that they might be involved in a ditching.

At 14,000 feet, they were able to get engine #4 restarted. A minute later, #3 was resurrected. Then, some 90 seconds into the sequence, engines #1 and #2 were restarted. At this point, the airplane was at 12,000 feet. Moody, concerned about staying safely above the 10,500-foot high mountaintops on Java, climbed the aircraft to 15,000 feet – unknowingly back into the ash cloud. A s S t. Elmo’s Fire returned, #2 engine started to surge violently. “Boom! Boom!” Moody exclaimed. Fearing the engine might tear itself off the wing, he shut down #2 and set the remaining engines at 85% power, leaving them at that setting for the remainder of the flight.

By this point in the saga, Flight Engineer Townley-Freeman surmised that the black material that stuck on Moody’s palms as he grasped the handrail in his earlier climb back up the stairs might be volcanic ash. Realizing the probable cause of their engine woes, Moody prudently decided to stay below 15,000 feet.

Now the crew had to land at Jakarta. ATC offered an instrument approach. However, as he attempted to comply, Moody noticed the needle indicating aircraft position relative to the glide slope was not working, although the needle showing aircraft position relative to the center line of runway 24 seemed to be functioning. Jakarta ATC was advised that a visual landing would be made and to please turn on the runway lights.

As they approached, Moody recounted that the whole city of Jakarta looked like it was bathed in a mist. When the runway lights were turned on, the windscreen turned white. The volcanic ash had sandblasted the windscreen to an opaque, dull finish. Neither Moody now First Officer Greaves could see out the front. However, they could see through a small –inch section on their side windows. Sitting on the armrest in order to peer through the precious 2-inch strip of clear glass, while controlling the yoke with his outstretched arms, Moody continued the descent as Greaves called out the radio altitude. At 100 feet, Moody said he knew that a safe landing could be made, although the few seconds remaining before the wheels touched down seemed much longer.

On the left, F.O. Greaves. Middle, Capt. Moody. Right, Flt. Engr. TownleyFreeman.

On the left, F.O. Greaves. Middle, Capt. Moody. Right, Flt. Engr. TownleyFreeman.

In the aftermath, all four engines, damaged by the sand blasting effect of the volcanic ash, had to be removed. The pitot system, contaminated by ash, was replaced. The scoured windscreen was replaced. Some 80 tons of fuel, possibly contaminated by ash particles, was drained off.

The volcanic material that adhered to the engine blades.

The volcanic material that adhered to the engine blades.

Although the aircraft did not look all that bad after the dramatic flight, the shiny paint had been scoured to a dull finish. Much cosmetic work was done to restore the aircraft to flight service.

The effect of sandblasting on a landing light cover.

The effect of sandblasting on a landing light cover.

Nearly three decades later, Moody believes the harrowing event had an effect on his appearance. Six months after the emergency landing at Jakarta, Moody noticed that some of his hair was turning white. Within 18 months, all of the then 42-year old pilot’s hair had turned white.

Captain Eric Moody today, with a healthy respect for volcanic ash based on experience.

Captain Eric Moody today, with a healthy respect for volcanic ash based on experience.

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