By John Laming  

Simulator sessions are rarely enjoyable unless the check pilot makes it so. Too often the session is filled with tension. Hardly have you sat down, when some small action will cause the check pilot to make critical comment, and the scene is set for differences of opinion.

The crew wait with silent apprehension for the first “abnormal”. Usually it is a starting fault where a rocketing EGT indication signals hot start. Hands immediately shut off levers, stop watches are pressed, and the crew become actors, rapping out instructions to simulated ground engineers, flight attendants, and non-existent traffic controllers. A perceived wrong move or instruction, and the simulator instructor presses the freeze button to “discuss” the error. Most times it’s his opinion against yours.

An entry is made in the “remarks” column of your record sheet – usually negative. If, however, you are a senior or management pilot, chances are that all your squares will be ticked off with no amplifying remarks – except a word of praise. Cynical yes but few will not identify with these experiences.

There are some emergency situations where it is better to sit back and assess the priorities before taking decisive action. Do that in the simulator and chances are that the instructor will comment on perceived slow or indecisive action.

A loss of pressurization may or may not require urgent action. It all depends on the severity of the de-pressurization. The simulator exercise usually consists of a simulated explosive decompression requiring crew oxygen masks to be swiftly donned, and an immediate steep emergency descent started. In periodical simulator training, emergency de-pressurization drills are de rigueur.

The problem with all this is that the simulated urgency seen in the simulator, coupled with perhaps some inevitable fumbling, usually means the pilot comes in for some minor or major criticism. On the rare occasion that the real thing happens in the aircraft, then reversion to hasty action based upon simulator experience, might provoke inappropriate response in the air. For example:

The Boeing 737 landed at Nauru at 2100 hours local time. When I took over the aircraft at midnight for the four hour flight from Nauru to Apia in Western Samoa, there were no snags recorded in the maintenance document. The flight was planned initially at 33,000 feet. There was sufficient fuel to reach Apia, with Pago Pago 80 miles further on as the alternate. Extensive cloud cover was forecast for the first two hours of the trip, then clearing to a fine early morning for our arrival.

The crew consisted of the first flight officer John Campbell, four air hostesses, and me as captain. There were 25 passengers, including an old Nauruan lady on her first flight. She was going to Samoa to visit relatives. She had lived in Nauru all her life, including the period of occupation by Japanese forces during the war.

In the control tower the flight service operator typed our flight plan through to Nandi Oceanic Control Centre. As we taxied for take-off on runway 12, he passed the airways clearance to us. The first hour of the flight was outside controlled airspace within an area known as the un-named Flight Information Region or FIR. We would then enter the Nandi FIR and become under radio control of Nandi in Fiji until we arrived at Samoa. The first officer was to fly this leg, and after we were airborne, I was responsible for the navigation and radio calls.

Coffee was served by the No 1 air hostess, and as we climbed to our cruising level, I had a good look ahead on the radar for the first of occasional thunderstorms which had been forecast. There were a few storm cells around, but we were well above their tops. Suddenly we overheard a Qantas Boeing 747 on the emergency frequency broadcasting into the night that he was cruising at 31,000 feet. His presence caught us unawares, as there had been no prior warning from the Nauru flight service operator that an aircraft was in our vicinity.

The 747 was on the way to Honolulu, and if we had taken off five minutes earlier than we did, we would have passed very close to him at the same altitude and in thick cloud. Later enquires showed that our flight service operator on Nauru had forgotten to check his teleprinter from Nandi warning of the presence of the 747.

Passing through 29,000 feet in cloud, I shone my torch on the windscreen wiper arms to check for ice. Sure enough a few millimetres had built up. With the engine anti-ice system already heating the front cowls we were well protected.

However, seconds later a warning tone sounded in the cockpit indicating what Boeing quaintly describe as an “abnormal” situation occurring. Both the first office and I said ‘what the hell is that?”

The tone was insistent, an intermittent beeping noise, and for the life of me I couldn’t think what was causing it. I had heard the sound many times before in the simulator, and it indicated a take-off warning to prevent a take off with either the brakes on, the flaps in the wrong position, or a couple of other faults associated with incorrect take-off settings on various components. But we were at 29,000 feet, certainly not taking off.

Scanning the instruments I noticed that the cabin altitude, which was normally around 8,000 feet, was now indicating 13,000 feet, and increasing at the rate of 1000 feet per minute. I then remembered that the warning beeps had a secondary function – that of letting the crew know that there was a pressurizing problem.

This was the simulator session all over again, this time for real. I took over the control from the first officer, levelled out on the automatic pilot, and together we carried out the rote cockpit drill of donning the emergency oxygen masks. The warning beep was insistent and irritating. I had forgotten that the beeps could be silenced by simply pressing a switch for that purpose. The next few minutes were memorable. In donning my oxygen mask, I succeeded in knocking my glasses to the floor of the cockpit. I cursed my ineptness; although confident I could cope without them in a fashion.

The beeps filled the cockpit until the first officer hit the right button on the dim instrument panel. I felt quiet calm about the situation, but was worried about the effect of the depressurization on the little old lady down the back. I announced on the PA system that we were about to commence an emergency descent and for that seat belts should be fastened and cigarettes put out.

With throttles at idle, and speed brakes extended, I lowered the nose and commenced a steep descent to 10,000 feet where we could breathe without emergency oxygen. At this stage we had no idea what had caused the pressurization problem, so the first officer went through the full drill which included closing the cabin air flow valve. I became conscious of a build up of pressure in my ears which became painful. The oxygen mask was made of rigid plastic, and it was impossible to relieve the pressure by the normal method of squeezing one’s nose and blowing hard.

The rate of descent had built up to over six thousand feet per minute, and because of total blackness outside, I was flying on instruments. Because of the nose altitude the radar beam was now reflecting from every moisture filled cloud around us, and the radar screen was filled with red returns. By now my ears where extremely painful, and without my glasses the instrument panel looked blurred.

Handing over the control panel to the first officer, I told him to keep the aircraft in a maximum rate descent while I scrabbled around the floor near my feet to find my specs. I couldn’t help thinking how appropriate were the words to an old British song which went: “My eyes are dim – I cannot see – I did not bring my specs with me....” Except my specs were somewhere near the base of the bloody control column!

We had plunged through 20,000 feet still in cloud, when I found my glasses, and angled them on to the bridge of the oxygen mask. The first officer and I were snorting like pigs through our masks, the snuffling being amplified through the cockpit overhead speakers. He was doing a good job of flying the aircraft, so I took the opportunity to look at the pressurization switches to try and sort out our problem. I was immediately astonished to see that the cabin altitude was now reading 3000 feet, which meant that we no longer needed to carve off height. The first officer in closing the outflow valve had obviously regained control of the pressurization system, which meant we could level out at our present altitude and sort out future action at our leisure.

The pain in my ears gradually subsided with much nose blowing, and we re-stowed our oxygen masks. We were now 90 miles from Nauru at 23,000 feet with 1600 miles to go to Samoa. There was no guarantee that the pressurization problem would not play up again, and after discussion with the first officer, I decided against pressing on to Samoa. The senior hostess appeared in the cockpit and offered a hot drink which we both gratefully accepted.

The cabin emergency oxygen masks (known as the rubber jungle), had not extended, which meant that we had stopped the cabin pressure rising before it had reached the trigger altitude of 14,000 feet. The passengers seemed unfazed, except for some that still experienced difficulty clearing their ears of pressure. The old lady seemed quite unconcerned. At least the entry into the emergency descent had been smooth and gentle!

We landed back in Nauru fifteen minutes later, and the passengers disembarked to wait in the terminal. As the little old lady released her seat belt, she looked up at the air hostess and said: “That was a quick flight dear, are we in Samoa already!”

Our Air New Zealand engineer replaced the suspect pressurization controller, and I contacted the chief pilot. He sounded curt on the telephone, and told me that I should have been aware that the pressurization controller had been faulty on the previous trip to mine. Apparently he had flown the aircraft into Nauru from Melbourne, and the cabin pressure had been continually changing by small amounts. While we had been flight planning at the control tower, the engineers had extracted a spare controller from a spares package held in the cargo hold of the aircraft, and fitted it. That spare controller had been in a plastic covering, and it turned out that moisture had seeped into the plastic cover, and eventually got into the controller. As we climbed through the freezing level, the moisture had frozen causing incorrect pressurization signals in the controller.

The fault on the Melbourne to Nauru leg had been logged on the last page on the maintenance document, and for our trip to Samoa, a new log book started. As we had not seen the inbound crew, we were not aware of a possible problem. The snag had not been carried over to the new log book. The upshot was that two pressurization controllers were faulty.

We resumed the flight to Samoa a few hours later, and I made sure that our little old lady was upgraded to First Class and treated like a Queen.