When Engine Instruments Lie

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Remember Air Florida Flight 90, the Boeing 737 that crashed into an icy Potomac River after takeoff from Washington National Airport in January1982, killing 74 of the 79 aboard? A contributing factor in that accident was anomalous engine instrument readings caused by ice-blocked EPR pickup tubes. Retired 737 captain and AVweb contributor John Laming tells of experiencing a similar problem, on takeoff from the tiny Pacific island of Nauru, which brought him to within seconds of disaster, saved by the actions of a quick-thinking pilot-in-command who was subsequently crucified by the airline whose airplane he saved. It's a fascinating story of technical intrigue and political injustice.

SafetyIn writing this article, I am reminded of the often-used patter by young instructors in which the student is told to keep an eye on the engine temperatures and pressures during the takeoff. The reality is that oil and cylinder head temperatures are slow to indicate trouble, while oil pressure needles can flicker and vary by small amounts depending on engine power and RPM. A sudden drop of oil pressure near liftoff could be an impending engine failure or a gauge malfunction, but there is simply no way of knowing for certain. A late abort for an engine gauge reading, when combined with a limiting runway length, has all the potential for an overrun accident.

The correct time for a last-minute assessment of engine health is at brake release, with priority then given to directional control, lookout, and airspeed indications. Good airmanship dictates that a critical stop/go decision should not normally be based upon one gauge alone. Always check for corroborative evidence before committing yourself to an irrevocable course of action.

The following incident happened on a dark Pacific night, where a seemingly impossible combination of factors caused a B737 to come just a few seconds away from disaster.

Air Nauru...

Boeing 737The best job I ever had was flying a Boeing 737 for a small airline, which was based on the tiny island nation of Nauru just 27 miles from the equator in the Central Pacific. The nearest daytime alternate was 375 miles away and a night diversion meant 500 miles to the Marshall Islands, or the burning of one's bridges of two hours island holding fuel, followed by landing or ditching! Our destinations included many of the Pacific islands between Hong Kong and Honolulu, the Solomons to Rarotonga, and New Zealand to Fiji. Our air hostesses all spoke English in a variety of charming regional accents and many were natural dancers who had been taught from childhood that music, laughter, and dancing was all that was needed to enjoy a full life.

We flew the popular Boeing 737 with most of the pilots expert at short-runway operations and black-hole approaches to remote islands. Some of us had been trained in the Royal Australian Air Force (RAAF) and our number included experienced ex-fighter and transport pilots. Other pilots included Americans and Kiwis, while the remainder were Australian GA pilots who had been employed on charter and instructor flying before getting that lucky break into an airline.

The runway on our island base was 5600 feet long, with a road cutting across only feet from each end. The overrun area was just 100 feet from the ocean, with the prospect of fatal damage if the aircraft collided with huge phosphate rock boulders which formed the sea wall. In the wet season, strong southerlies meant crosswinds up to 30 knots while huge waves whipped up by the winds dashed themselves against the rocks, sending mist and spray over the threshold.

...and Air Florida

Readers may remember a widely publicized 1982 accident involving Air Florida Flight 90, a Boeing 737 that crashed on takeoff from Washington National Airport as it tried to get airborne while covered in snow and ice. The aircraft was unable to hold altitude and, after hitting a bridge, crashed nose first into the frozen Potomac River. The FDR was recovered and its evidence showed that the engines had not delivered full takeoff power during the takeoff. The engine power indicators had given false information to the crew, possibly due to ice blocking air inlet tubes which, in turn, sensed the power delivered. These tubes, which have an opening the size of a drinking straw, measure the pressure of air being drawn in by the engine compressors, and compare it to the pressure increase due to combustion which is pushed out at the back of the engine. Known as PT2 sensing tubes, they show the engine pressure ratio (EPR) on a cockpit gauge. (See CVR Transcript.)

Air Florida Flight 90In simple terms, if the front tube is blocked, the sensor thinks no air is coming into the front of the engine. The rear sensor, operating normally, senses lots of high-pressure hot air being ejected from the tail pipe and thus the EPR will indicate an abnormally high reading. The natural tendency to remedy the apparent excessive power indication on the EPR gauges is for the pilot to ease the throttles back in order to keep within perceived engine limits. The engine RPM gauge will, however, show the pilot the real power being produced. Obviously, if 100% RPM is indicated, the engine is really pushing out lots of power, regardless of a false reading on the EPR gauge caused by a blocked PT2 tube. The advantage of the EPR gauge is that accurate power settings can be measured, providing of course that the system works as advertised.

Following the lengthy investigation into the Potomac accident, notices were sent to all operators of Pratt & Whitney JT8D series engines, warning that crews should be on alert for erroneous EPR indications in icing conditions and to rely primarily on the engine RPM gauge for actual indications of power. Typically, the RPM gauge is called an N1 or Fan gauge and will usually show 35% N1 while idling, 83% in cruise, and 95% 101% on takeoff. Blocking of PT2 tubes by substances other than ice was not discussed in the Alert Bulletin.

Boeing recommended that the crew calculate the expected EPR and N1 gauge readings for each takeoff. These readings, which are placed on a takeoff data card, will vary, depending on the takeoff weight of the aircraft, length of runway, ambient air temperature, and aerodrome pressure altitude. Also on the card will be the V1 decision speed, rotation speed, and other information pertaining to the takeoff.

An interesting situation

The following episode began when I was rostered to fly as a passenger on a nonstop night flight to Guam in the Western Pacific. Flight time was four hours and, on arrival at Guam in the early morning, I had planned to catch some sleep at The Hilton Hotel before crewing another flight to Manila.

There were 60 passengers including some deadhead crew on the flight and, after boarding, I settled into a first-class seat, adjusted my reading glasses, and watched the senior hostess brief her cabin crew as the engines were started. A few minutes later, at 0130 local time, the aircraft moved onto the runway, back-taxiing for takeoff to the northwest. From my window seat, I could see a line of cars on the nearby road only 50 yards from the runway. The flashing blue light on a traffic policeman's motorbike indicated that he had stopped all traffic to prevent anyone getting blown off the road by the jet blast on takeoff.

A few seconds later, the senior hostess came to me and said that the captain had invited me up front for takeoff. Like most pilots, I welcomed the chance of observing the action from the cockpit and, leaving my reading glasses on the seat next to me, I entered the darkened flight deck, quickly sat on the jumpseat, and thanked the captain, whom I had trained for his command some months earlier.

The first officer was to carry out the takeoff and I caught the last part of the emergency briefing as we slowly turned to line up. The takeoff data card indicated 10 degrees of flap for takeoff, V1 of 130 knots, VR (rotate) speed of 135 knots, and initial climb speed of 145 knots. Even without reading glasses, I could plainly see the EPR gauge digital cursors set for 2.18 EPR, which meant maximum takeoff power was needed. This was understandable, considering the short runway, the hot night, and the extra fuel needed for a long flight. The data card also showed that the crew had calculated 100% N1 was needed for takeoff, and this tied in with the 2.18 EPR limit. The N1 gauges were dimly lit and I could not see the needles clearly without my glasses, which I had left back in the cabin.

The traffic officer's blue strobe light was still flickering on the road ahead and, from our position on the runway threshold, I could just make out the surf of the Pacific a few feet behind us and the dark shape of the control tower some two thirds down the runway and just off the parallel main road. From previous experience, I knew that the indicated airspeed should be around 120 knots as the aircraft passed abeam the tower, with liftoff speed usually 10 seconds later.

Takeoff power

The captain opened the throttles to 1.6 EPR with brakes set, checked that both engines spooled up evenly, then quickly advanced the throttles to the planned takeoff power of 2.18 EPR. The brakes were released and the first officer began to steer the aircraft down the runway centerline. Acceleration appeared normal, and I could clearly see both EPR gauges steady at 2.18. The airspeed indicator needle began to accelerate past 60 knots and I checked all engine gauges in a swift eye scan. Fuel flow, N1, and exhaust gas temperature (EGT) were all pointing in the right area, although somewhat blurred to my vision without my glasses. Seconds passed and the captain called "80 knots" as the dual airspeed indicator check. A sixth sense warned me that the acceleration was not the solid kick in the back that I would have expected from 2.18 EPR, and at the same instant I noticed the captain begin to glance rapidly from the instruments to the remaining runway ahead. There was no readily discernible problem but I had an uneasy feeling that something was not quite right.

The company procedure was that, apart from the 80 knot airspeed check, no calls were to be made by either pilot unless something was seriously amiss. On this occasion, the takeoff seemed to proceeding normally and, apart from my vague unease at the perceived lack of marked acceleration, I was unable to pinpoint any impending problem.

The control tower and passenger terminal building flashed past the right wing tip, as I strained forward against my shoulder straps in an attempt to focus more clearly on the vital N1 gauges. The EPR needles were clear exactly 2.18, but again I could not get an accurate look at the N1 without glasses. The airspeed reading went through 110 knots, we should have been perhaps 10 knots faster from my experience, and my unease grew stronger. One thing was happening for sure, and that was we were rapidly using up the remaining runway. Six runway lights to go, and we were still at least 10 knots below V1, the go/stop decision speed. It was, to say the least, an interesting situation, and I hoped that the captain would not make a split-second decision to abort the takeoff because we could now never pull up in time, even with maximum reverse thrust and braking. Our V1 speed was useless now, and the invisible sea swept rocks were only seconds ahead.

My unease had just changed into the cold realization that we were never going to attain liftoff speed before reaching the end of the runway, when suddenly the captain urgently called "ROTATE NOW!" and while hauling back on the control column he pushed both throttles hard against their forward stops. Boeing terms this "firewalling the thrust levers," to be used as a last resort to climb out of trouble.

The last runway light disappeared under us, as did a fleeting close-up sight of the brilliant blue flashing strobe light of a shocked traffic cop's motorbike. I felt the reassuring surge of thrust propel the 737 upwards at a deck angle of 20 degrees, and silently thanked the Lord that the captain had made an instant correct decision to firewall those Pratt & Whitneys. I knew that the Potomac accident might have been averted if the crew had only hit the throttles wide open to the stops, to prevent their ice-laden Boeing from stalling.

We were later told that the flight data recorder showed that the aircraft had lifted off at 15 knots BELOW the calculated VR rotation speed, and that the aircraft had flown just 19 feet above the sea for several hundred yards before gradually climbing away. We never did see the towering metal structure of the phosphate cantilevers that passed above our altitude, and situated 200 yards to the right of the extended runway centerline...

What's wrong with this picture?

Ahead was sheer blackness, and the captain locked on to instruments as the ASI needle crept towards safe flap-retraction speed. The VSI was held at 1000 fpm, and the first officer set the climb thrust at 1.93 EPR as the flaps were slowly retracted in sequence. It seemed an abnormally long time before the aircraft reached 250 knots, which was the scheduled climb speed that night, and the rate of climb was well below normal. Finally we passed 5,000 ft, engaged the autopilot, and called for coffee while we held a roundtable conference on the recent events. The mechanic who had been seated in the cabin came up front and said that a couple of deadheading pilots down the back sent their respects to the captain, but they hoped he had finished playing silly buggers with the aircraft as they were hoping to get some shut eye! They had obviously felt the thrust change through the seat of their pants.

We turned our attention to a detailed scan of the engine instruments and the mechanic remarked that the N1 indications seemed low when compared with the 1.93 EPR climb setting. From the back of my mind came the recollections of previous problems that I had experienced several months ago with an over-reading EPR gauge. On the first occasion, we had just attained takeoff thrust early in the roll, when one EPR needle moved to an apparent overboost figure of 2.35 EPR, while the second needle stayed steady at the planned 2.10 EPR. The other engine parameters were normal for takeoff and, in particular, both engines were turning up nicely at 100% N1. Clearly the problem was a faulty EPR indication and, as our speed was only 50 knots, I decided to reject the takeoff and return to the terminal for a chat with the mechanics. A check of the PT2 tube, plus an engine run up, indicated the problem had cleared itself and we departed an hour later.

More recently, at 100 knots on takeoff, a similar fault occurred and this time, the F/O urgently called that the engine was over speeding. He attempted to pull back the throttle on that engine to limit the peak EPR, but I quickly stopped his hand and told him to ignore the faulty reading. He was convinced however, that the engine was overboosting because of the high EPR reading, although I felt no asymmetric yaw on the flight controls. I again prevented him from dragging the offending EPR back and we continued the takeoff using the N1 RPM (which was steady at normal takeoff thrust). Once at a safe altitude, I turned on the hot air bleed system to the engine anti-ice, and almost immediately the offending EPR needle did a few cartwheels and returned to normal. We were not in icing conditions but the hot air used for de-icing had obviously cleared some obstruction in the PT2 tube. The flight was continued without further incident.

Back now to the present situation, where early indications of long-distance storm activity began to show up on the weather radar screen. The storm tops were around 35,000 feet, and at our dismal rate of climb we would be in the thick of things in the next 20 minutes.

With the throttles set at the computed climb EPR, it was readily apparent that both N1 readings of 88% and commensurate low fuel flows meant that some common denominator was affecting both engines at the same time. We discussed fuel contamination but decided that it was unlikely, given that the engines had delivered maximum available overboost when the throttles had been firewalled earlier. I gave fleeting thought to the possibility of EPR gauge malfunction, especially after my previous experience with this problem, and knowledge of the Potomac accident. With a warm airport temperature of 30 degrees centigrade, icing of the PT2 tubes could be discounted and, in any case, it would be highly unlikely that an identical malfunction would affect both PT2 tubes simultaneously.

On my suggestion, the captain momentarily switched on the engine anti-ice to both engines. This would normally cause a small loss of about 5% N1 and an EPR drop of .08, which reflected the stealing of some hot compressor air for piping to the engine inlet cowls and PT2 tubes.

The N1 dropped obediently but both EPR gauges went crazy, increasing by an unheard of amount, and in the opposite direction to that expected. My mind went back to a paragraph in the Potomac accident report which mentioned that with the engine anti-ice switched on and PT2 tube blocked, the EPR needle would indicate a reverse reading to that expected. Thus, tonight, the impossible had apparently occurred: an identical erroneous reading on both EPR gauges at the same time. The PT2 tubes were obviously still blocked but we now knew for sure that both engines were operating normally. The decision was made to return to land and, at 500 feet, the landing lights were switched on, illuminating drifting mists of phosphate dust from the nearby mine. The touchdown was perfect, right on the 1000-foot runway marker. Well-coordinated reverse thrust and braking gave nice cool brakes on arrival back at the terminal.

Diagnosis

As the passengers disembarked to wait out the delay in the airport terminal, mechanics had already removed the engine nose cones in order to check out the PT2 system. With the aid of a flashlight, the cause of our troubles was soon discovered. The PT2 tubes of both engines the sensors that gave the vital Engine Pressure Ratio readings for takeoff were blocked, not with ice but with congealed phosphate dust and some other glutinous substance. It was impossible to determine the precise time that the tubes became blocked, or how the substance found its way into the system.

At dawn a few hours later, early workers driving past the departure end of the runway were the first to see debris from the coast road and nearby cliff face rocks, blasted back over the threshold by the jet efflux of the 737. Black skid marks on the road showed where the traffic policeman had burned up rubber in a spectacular scramble for safety.

Later calculations showed that the actual power on takeoff was around 2.05 EPR, even though the EPR needles were steady at 2.18. That power would have been ample for a long runway, and in fact was a setting frequently used for the right combination of runway length and gross takeoff weight. The N1 gauge scale between 91% and 100% is less than 3mm and very difficult to read in dim light, especially at a quick glance. This might explain why the crew was unable to pick the apparent lower-than-normal N1 readings on the takeoff run. At night especially, it is also impossible to make any meaningful correlation between rate of acceleration and runway remaining. Until it is almost too late, that is.

Several months afterwards, I read a report that described an incident on a Boeing 727 that departed at night from a U.S. airport. The aircraft used 9000 feet of runway and during rotation, it wiped out the ILS localizer antenna situated more than 1000 feet beyond the overrun area. The aircraft was damaged but continued to fly. Investigation revealed that icing conditions had prevailed and the crew had failed to actuate the engine anti-ice switches for takeoff. All the PT2 tubes had iced up during the takeoff roll, giving significant EPR gauge error. The crew did not detect any acceleration problem until almost too late and also did not firewall the throttles.

Later versions of the Boeing 737 have CFM56 engines which rely on N1 gauges as the primary power indication. EPR gauges still remain on many older jet transports, however.

Aftermath

Following the incident on Nauru, the chief pilot suspended the captain from flying duties. There was no in-depth investigation only the personal opinion of the chief pilot. In his report to the President of Nauru, who also held the position of Minister for Civil Aviation, the chief pilot recommended that the captain be downgraded to first officer permanently. This type of unilateral action by the chief pilot was typical of the way he operated the airline, and there was no effective avenue of appeal available to anyone unfortunate enough to cross swords with the management pilots.

As I explained earlier, the phenomenon of unreliable EPR readings on takeoff had occurred to me and other pilots, and although these had been reported through official channels to management, there had been no revisions to the operations manual warning of the specific problem. Some information had been casually disseminated over beers at the bar of the local pub.

The Civil Aviation Department of Nauru consisted then of only two individuals: the Director and a Project Officer. Neither had aeronautical experience, both being more-or-less political appointees. Hence any advice on operational matters was sought directly from the chief pilot, and his advice was then rubber-stamped. Operational surveillance of the airline was carried out by civil aviation authorities from New Zealand. This meant that a flight operations inspector from New Zealand would occasionally fly with a crew on a scheduled flight. Reports on flight crew performance were generally very good, although there was sometimes mild criticism of the administration and support services. The maintenance of the aircraft was the responsibility of Air New Zealand, and this really was first class in all respects. The government of Nauru spared no expense in this regard.

When I heard that the captain had been demoted, I contacted the chief pilot to register a strong protest at this unfair action. The word had quickly got around the rest of the aircrew that the captain had been shafted, but apart from a few sullen mumbles out of the earshot of management, not one pilot had openly questioned the motives behind the management's decision. Job security was the name of the game. The deputy chief pilot was a clone of his boss, and in fact had been the first person to meet the aircraft after its immediate return to Nauru on the night of the incident.

Aware of the fact that someone is always the scapegoat in this type of situation, I had vacated the cockpit after landing, and was sitting innocently in a passenger seat when the deputy chief pilot boarded the aircraft on its return. He was therefore unaware of my presence in the jump seat when the fun and games had started. I had advised the captain to let me know if he needed my backing as a witness, as knowing the then-management style, there was a strong chance that the captain would be pronounced guilty of a wrong operational decision without a fair trial. For this reason I wanted to keep my powder dry for any forthcoming stoush.

In my view as a direct witness, the captain had done an excellent job of airmanship in his decision to firewall the throttles. The chances of an identical double EPR failure at night, causing identical instrument readings, were infinitesimally small, and it would be classically wise after the event to blame the crew for not picking the problem. The actual power (EPR) used on that night was similar to that used on an everyday reduced-thrust takeoff at longer runways such as Hong Kong, Guam, Nandi or Sydney. The acceleration forces were identical to a planned reduced-thrust takeoff, and it was only at a late stage of the takeoff at Nauru that it was realized that the takeoff run was going to be insufficient to lift off.

After the mechanics had dropped the engine cowls and discovered the blocked EPR tubes, I had been witness to an extraordinary outburst from the deputy chief pilot directed towards the captain. He was told that the incident was all his fault, and to get the aircraft on its way to Guam as soon as the mechanics had signed the paperwork.

On our arrival at Guam a few hours later, I was handed a message from Nauru that I was to take over command of the return flight, and the other captain would come home as a passenger. I suspected that the scene was being set up for a kangaroo court. Later events proved I was right.

A few days later I was home in Melbourne on days off, when I heard that the captain had been suspended indefinitely until the President of Nauru had made a decision to terminate the captain's contract, or agree to the chief pilot's recommendation to demote him for good. After connecting a tape recorder I had by now, little faith in justice I telephoned the chief pilot in Nauru, and protested strongly, stating that as an observer in the jumpseat, I thought the captain should have been congratulated for having done the right thing at a most critical time. The chief pilot warned me to keep out of the affair otherwise my own future would be at risk. I replied that I had no intention of closing my eyes to the matter, and that my report would go directly to the Minister for Civil Aviation. The battle lines were drawn.

Escalation

I contacted the New Zealand flight operations inspector responsible for Air Nauru, and explained the circumstances of the incident. His name was Captain Ian Gemmel, himself a former chief pilot of Air New Zealand. Gemmel said he had only sketchy details of the incident, gleaned from hangar talk by the Air New Zealand mechanics who had recently returned from Nauru from their fortnightly tour of duty. He had not received any direct report from Air Nauru management, which of course included the chief pilot.

I explained that I had been aboard the 737 at the time, and he listened with interest to my side of the story. He was very diplomatic, and careful not to give any opinions on the telephone. I told him that the captain was under suspension, but again he made no comment. When I suggested that he should investigate the incident in the light of his position as our flight operations inspector, he replied that protocol dictated that he wait until invited by the Nauru Director of Civil Aviation to come to Nauru. I knew that wouldn't happen.

This was a dead-end conversation, but at least the inspector now knew the facts, even though he could not (or would not) act to get a formal investigation underway. Certainly he showed little interest in the fate of the captain. The first officer, incidentally, was part of the management team drinking circle, and escaped with a minor admonishment quickly forgotten over the next round of drinks.

I next contacted Captain Belton, the then-Technical Director of the Australian Federation of Air Pilots, known as the AFAP. Although Air Nauru pilots could not belong to any industrial union by the terms of their contract with Nauru, nevertheless the brotherhood of pilots meant that the AFAP would help with advice if sought. The captain and myself were interviewed by Belton, who showed great professional interest in the incident, especially with its parallel in the fatal Potomac River B737 accident in the U.S. Ansett Airlines subsequently advised their crews of the circumstances of the Air Nauru incident.

Belton then wrote to the Director of Civil Aviation (DCA) in Nauru expressing concern at the treatment by management of the captain, stating that such injustice would never be tolerated in Australian airlines. He urged the DCA to release the captain from suspension and initiate a full technical investigation of the incident. There was no reply from Nauru.

Politics

About that time, some hard decisions regarding the future of Air Nauru were being debated in the Nauruan parliament. The airline was heavily subsidized by the government, and was losing money. The chief pilot was told to dismiss half of the total pilot workforce, and it was left to his discretion who got the chop. About 15 pilots were given one week's notice, although there were rumors that most of these would be rehired once the political crisis in parliament had been resolved. The President of Nauru and his people were inordinately proud of the airline and its crews, and it had been with great reluctance that the order to dump crews had been sent down the line.

In situations like this, it would normally be last-on-first-off in order of seniority with the company. I thought I would be safe. I was dead wrong. The chief pilot first got rid of all those captains over the age of 50, except himself. There were four of us, all senior in the airline. That neatly got rid of a few thorns in his side with no bloodshed. Next went a few more captains and first officers. One first officer had recently been recruited and had volunteered for the secondary appointment of navigation officer. His job was to update the office Jepp charts. He had only been in the airline for a few months, but kept his job because he had a formal "title." He was also on excellent terms with all the management captains.

Seniority or good service counted for nothing. One pilot sacked was the captain of the EPR incident. He was already on suspension anyway. While in limbo, he spent a lot of money on a Boeing 727 command endorsement, and got a job flying a 727 for a Saudia Prince. He went from success to success and at the time of writing is a senior captain with a well-known Australian airline.

The crews dismissed were not told on what basis their names were chosen. I believe it was a night of the long knives. A few weeks later, there was good news for some that were sacked, as Parliament authorized the rehiring of everyone, subject to the chief pilot's choice. The knives were twisted when none of the over-50s were hired, and were left to go on the dole in Australia. Soon afterwards, more pilots were hired to replace the over-50s that had been sacked, and first officers waiting in the wings were promoted in their place. There were no airline jobs in Australia, and so I became a taxi driver, as did a few others. My most bitter moments were waiting for customers in a taxi rank outside Melbourne airport to find that my clients were newly-recruited Air Nauru pilots hired to replace my colleagues and me.

Unfinished business

My last flight was a scheduled service from Nauru to Fiji and return. Attempts on my part to get justice for the suspended captain had foundered. The Nauruan DCA simply lacked the technical knowledge to adequately assess the recommendations by the chief pilot that the captain be demoted. They saw that as an internal matter between the captain and expatriate management. The captain was dismissed as part of the sudden retrenchments, and the file closed. There was no follow up by the New Zealand Civil Aviation inspector because he was never invited for his opinion.

It was nighttime in Fiji as we loaded passengers for what was to be my last flight with the company after 10 years of service. I was deep in thought as the first officer set up the navigation systems. I could hear the soft voice of the young Nauruan flight attendant as she welcomed her brood on board. The last of the passengers arrived at the bottom of the airstairs, and I noticed that one of them was a Nauruan cabinet minister whom I knew well. He had been the Director of Civil Aviation when I first joined the airline all those years ago, and was well regarded as a thorough gentleman. He was a qualified aeronautical engineer.

My own career with Air Nauru was to end with a final touchdown on Nauru in four hours time, but now I saw an opportunity to clear up some unfinished business. I was down the stairs in a flash, and greeting the minister like an old friend, I took him aside and asked him if he was aware of the near accident to the 737 a few weeks earlier. He looked puzzled when I told him that there were certain aspects of the incident which I didn't like. He said Parliament had been told by the Director of Civil Aviation that it was the captain's fault, and that the dismissal was warranted. Ink was now dry on the rubber stamp.

I invited the minister to the cockpit for takeoff, but meanwhile showed him the tiny air intake in the front of the 737's engines which had been blocked by unknown debris on the night of the incident. I showed with a flashlight that any blockage would be undetected because of the curvature of the PT2 tubes. He was surprised that the blockage of such a tiny tube could cause a near disaster.

After he boarded, the senior flight attendant closed the front door, and ushered him to the cockpit. I asked him to bear with me while I gave him a thumbnail sketch of the EPR gauge operation, and backed it up by showing him the schematic from the systems manual. All this time, the mechanics below were patiently standing by to push the Boeing backward away from the airport terminal, prior to our starting the engines. We were already late on schedule, but I didn't give a damn.

I explained to the minister that the incident to the 737 had important ramifications to future takeoff departures from Nauru, and that there was some suspicion that the debris that had blocked the EPR tube contained phosphate dust from the island mines. I then gave him a notepad and pencil, and asked him to record the various engine instrument readings on takeoff. I was hoping to convince him that on a night takeoff with dim instrument lighting, it was possible to misread the main RPM gauges by a small amount. That small amount had proved critical on the night in question, and fatal on the Potomac accident.

As an aeronautical engineer, he was aware of my explanations, and as we later lined up for takeoff, I told him to read the gauges at 80 knots and at liftoff.

I opened the throttles to full thrust and as the airspeed reached 80 knots I asked the minister to take down the EPR, N1, and fuel flow readings. He asked me to turn up the instrument lighting, as he could not get an accurate reading. At liftoff he again took the readings and complained that the N1 gauges (which give the fan rotor speed in percent of RPM) were too hard to read at a quick glance. I then reduced the power to climb thrust and asked for a final reading of the three engine parameters.

Next I asked the minister to adjust the throttle settings to various positions, and then asked him to call out the actual readings from the gauges. By now he had got the message that on takeoff, it took more that just a half-second glance to focus one's eyes at night on the critical engine power instruments. With perhaps no more than three millimeters between a needle indicating 93 percent and 100 percent power, it was possible to miss a critically low power indication when the cockpit lighting was dim, as in a darkened cockpit. The situation where the main engine EPR digital readout was falsely displayed on the EPR gauge as full power only exacerbated the problem.

The aircraft was by now established on course for Nauru, and after engaging the autopilot and double-checking that the ground-based navaids confirmed that the aircraft inertial navigation systems were tracking correctly, I switched off the seat belt signs and asked the flight attendant to send up the coffee. The minister sat quietly, his eyes scanning the cockpit levers and instruments and finally settling on the green glow of the weather radar screen. A few areas of heavy rain clouds were inching towards us from the top of the 180-mile markers, and I made a mental note to watch these radar echoes more closely in the next ten minutes. Our senior flight attendant, who was from the Solomon Islands, opened the cockpit door and delivered us three steaming cups of coffee. As she closed the door and returned to the bright lights of the passenger cabin, the minister said to me quietly, "Captain, what you are trying to tell me is that you disagree with the opinion of the chief pilot in sacking the captain who had the takeoff incident at Nauru?"

I chose my words carefully, as it was not my intention to come out with a direct criticism of the chief pilot. This would conflict with the island culture where it may be construed as poor manners to criticize one's immediate superior, and any ill-chosen words could be counterproductive. I told the minister that he had politics to contend with in his area of work, and that there was office politics in the flying and operational of the airline.

I pointed out to him that a similar event had occurred in Washington D.C., where false engine readings, this time caused by ice blocking the engine instrumentation, had caused the crash of Boeing 737 with many killed. The pilots had failed to realize the cause of the problem until too late and the captain had failed to firewall the throttles to power the 737 out of a stall. The captain on the Air Nauru incident had acted quickly by advancing both throttles to maximum available overboost and probably averted an otherwise-certain accident. I added that there should be an independent technical investigation on the incident, because as it was, the captain had, in the opinion of many Air Nauru pilots, been unfairly dealt with by the chief pilot and others of the management.

"What do you want me to do?" asked the minister. I replied that the normal procedure would be to formally advise the New Zealand Civil Aviation authorities of the circumstances of the incident, and ask them to send an inspector to Nauru to interview the various people concerned. The minister agreed to discuss the situation with his Cabinet colleagues. As I was about to become unemployed in three hours, there was no more I could do except hope that the minister would keep his word.

From gauges to radar

It was time to turn my attention to more immediate matters. The large clouds on the radar screen were growing closer, and their ominously red centers on the radar display indicated we would run into severe turbulence if the aircraft maintained the direct track to Nauru. We were in thick cirrus cloud, which meant that we were unable to visually navigate around the big stuff ahead, and were now relying entirely on the radar to "see" the storms, and avoid them.

Over the years, the airline had experienced many failures of the radar, and several aircraft had inadvertently flown directly into severe thunderstorms without any warning. Radar spares were held in New Zealand and Australia and could take several days to finally reach the aircraft. Due sometimes to commercial pressures, and occasionally a misplaced sense of the macho, there were captains who would invariably accept the aircraft without a serviceable weather radar, and press on into the night risking thunderstorm penetration with all its well-known hazards to flight safety.

I had been a passenger on some of these occasions, and had been scared witless knowing that the radar was unserviceable. Passengers and flight attendants were always blissfully unaware of the possible menace ahead. The weather forecasts around the Pacific almost always warned of the presence of occasional thunderstorms. Murphy's Law dictated that one of these would have your name on it. Sod's Law amplified Murphy's which meant you could count on the probability of blundering into a whole line of storms that were aligned with your current track! There would be little warning until static electricity would start to flicker in blue sparks over the windscreen, and next second there would be savage buffeting and frightening turbulence. The knowledge that certain types of thunderstorms could cause the destruction of an aircraft was ever in my mind on those occasions, because the aircraft was flying blind and the crew counting on statistics and luck to avoid the really bad storms.

The solution was easy, and that was to place radar spares at strategic ports around the airline network. Guam and Nauru were the two hubs of our operations, but the various management teams closed their eyes to the problem, and instead relied upon captains to "cooperate" to keep the aircraft flying until the spares caught up.

With these thoughts in my mind, and the presence of a captive minister in the jump seat, I formulated a plan. If the plan was successful, it would mean a safer operation of the airline. Either way, I had nothing to lose, because my airline career was over for the time being, that is.

The single thunderstorm (isolated, in meteorological terminology) was less than 50 miles ahead and we were closing on it at 7 miles a minute. That meant in 7 minutes we were going to get beaten up by nature. Unless, of course, I steered the aircraft around it.

Hitting the stopwatch, I quickly briefed the first officer of my intentions through the headset communication system, without the minister hearing the conversation. I then showed the minister how the radar controls worked, and explained how to judge the severity of a storm by the various color codes on the screen. I let him adjust the various radar control switches, adding that without the radar we would not see the monster ahead. I then switched the radar to standby, leaving a blank screen. The storm by now was 30 miles dead ahead, and invisible to the three of us in the cockpit.

I told the minister that lack of suitable spares positioning around the airline network meant aircraft were occasionally flying without operating radar for several days. We operated broadly by Australian Air Navigation Orders, which required Australian-registered aircraft to have an unserviceable radar repaired at the next major servicing base, and in any case the aircraft must not be operated in to areas where thunderstorms were forecast without a serviceable radar. I explained that there were many servicing bases in Australia, and an unserviceable radar was quickly replaced. This luxury was not available to our crews because of the far-flung nature of the Air Nauru route structure, coupled with reluctance to hold spares at intermediate airports.

I had my eye on the stopwatch, with three minutes left before I would turn off course to miss the storm cloud ahead. The minister began to sweat a little, as I explained that the blank screen in front of him represented an unserviceable weather radar, and could he not see the danger of flying blind without radar? Especially as we knew that there was indeed trouble ahead. I explained that this then was the dilemma facing the captains who were forced into the difficult choice of canceling a flight or accepting risks by keeping to schedule.

To avoid these situations, we needed to place radar spares on Nauru and Guam, I said. By now, the minister was getting tense, and so was the first officer. Both knew that the storm was almost upon us, and the minister hinted that it was high time the radar was switched on. I asked him to do the honors, and in a flash he had switched the control knob from the standby position to on. Seconds later, a solid red mass bloomed at 15 miles, and I began to turn the 737 to starboard using the autopilot controls.

Hardly had the aircraft straightened out on the new heading, when the cloud that we were in magically disappeared and we were bathed in light from a full moon. Miles below there were hundreds of tiny cloud shadows on the Pacific, a characteristic of this part of the ocean. There on our left a single monstrous cloud towering from the ocean to 35,000 feet slid silently past the wing into the darkness behind us. Lightning flickered and flashed deep inside its core and I watched the face of the minister as he stared transfixed at the raw power of nature.

"You have made your point, Captain," he said. "Now where do you want those radar spares?"

Partial victory

A few weeks later, I was driving a taxi. I heard through the grapevine that the New Zealand inspector had been invited to Nauru to investigate the takeoff incident. His report exonerated the captain, and recommended that he be commended for his actions in firewalling the throttles and thus preventing a certain disaster. The inspector also made critical comment on the lack of operational information in the company operations manual, following previous instances of EPR tube blockage on takeoffs from Nauru.

The captain was not offered reinstatement despite the recommendations of the inspector, and ten years later he has still received no official commendation for his actions.

Radar spares were allocated to be held on Nauru, but not on Guam. Ah well, you can't win them all, I suppose!