CUMULO NIMBUS

(There had been eight crashed Transport Command aircraft in 1945 with the death of many of the crews and some politicians and senior military personnel and such was the alarm in high quarters that there had been a Parliamentary debate on the subject earlier in that year with calls for a select committee enquiry. This never took place but the rate of crashed or lost aircraft continued to be high)

The weather had been freezing when they left Lyneham airport and now, at the end of the route in Singapore they were determined to make the most of the few days of sunshine on the beach. But they had overdone it; this was no English summer resort, they were a few degrees from the equator and the first night their skins burned with feverish heat. Freddie was the worst affected being of very light complexion he was lobster red. The rest of the crew were in varying state of sun burn,

They stayed indoors the following day; Freddie had a temperature and went to see the medical officer who thought Freddie shouldn’t fly so Ross arranged to defer the return flight scheduled for the following day. Freddie stayed in bed while the other four sat on the verandah drinking to dull the painful effects of the sunburn. They were quite merry when the session ended and B certainly slept better.

The next morning all four of them were suffering from nausea and hangovers but by this time Freddie said he felt fit enough to fly. This caused Ross to reverse the decision to postpone the take-off, and it was a less than an enthusiastic crew that made the flight preparations. When all was ready with freight and mail aboard and the passengers settled, take off drill began. The Changi airstrip runs towards the sea and at the end of it there is a cluster of palm trees on the shore line, direct in the flight path. This presents no danger on normal take-offs or landings but even so, one wonders why neither the British, nor the recently ejected Japanese airport authorities did not have them cut down because, in abnormal conditions, they might well have been a hazard. Reflexes were slow that day, and Tash the flight engineer, delayed relaying the boost figures to Ross. It looked as though the plane might be under-powered when they watched the approaching palm trees as the rising plane drew closer and closer to them. Both Ross and Tash corrected and the wheels of the undercarriage scraped the tops of the trees. There were quick looks exchanged amongst the crew; looks of relief, surprise and resignation, but there was no adrenaline going, as was usual at such times. They were an apathetic lot, working their ways back to their usual levels.

The meteorological briefing had warned of thick cloud as the early monsoon gathered pace, and it was decided to try and reach the clearer, calmer air, above the cloud formation. This was going to be a long haul and mostly over the sea. At a height of ten thousand feet they were still in the middle of nimbus cloud, dense, turbulent and electric. The York was thrown this way and that, creaking with the built up pressures, The propellers of the four engines droned ceaselessly, pulling the aircraft higher and higher into the gloomy, slate blackness. In spite of this insistent noise, a part of one’s being sensed the icy cold silence of the enveloping cloud outside. Shafts of lightening illuminated the blackness from time to time. The ascent seemed timeless, but something would have to be decided soon; when the cold and diminished oxygen would limit the level to which they could climb. Their oxygen masks would enable them to carry on climbing but, if they were still in cloud they would be in danger of icing up or, just as bad, get into the most turbulent ‘anvil’ part of the cloud. The passengers were not issued with oxygen masks and so this was another reason for a risk that few skippers would wish to take.

Their initial lethargy was now replaced by tension, and Johnny was the first to notice Freddie’s ashen face. His eyes were bright and feverish with profound sweating. Ross was informed and called B. ‘Freddie’s in no state to be up here. Will you get him as comfortable as you can at the back, and then take over the navigation.’ When the-alternatively-sweating-and-shivering Freddie had been settled in blankets after a drink from a tea flask and some aspirins from the first-aid pack, B returned to look at the situation. A few minutes perusal showed him that Freddie had not been able to take any fixes of sightings, they were therefore on an original compass course ever since leaving Changi some hours back. The wind speed and direction also being used for calculations was from the time of their take-off, so in all probability bore no similarity to the present conditions. Theoretically, they were on some point of the map but practically, they were lost. ‘How much higher can you climb, Ross? I need to get a fix.’ ‘This is about it,’ replied Ross. ‘If we can’t get through this crap in five more minutes, at twelve thou, I’ll have to go lower, possibly nine, and level out. What I need now is a new course.’ Yes, but how to go about getting one?

He re-checked Freddie’s calculations from Changi. These were OK but in an air-mass, such as the one they were in now, wind speed and direction rarely stayed constant, and because of this, they could already be many miles off their true course. It was a similar situation to the training exercise at Jarvis, a couple of years back, he thought. Only then, they were over land instead of water, had clear visibility, whereas here, there was none, and a pilot who could have done the exercise in his sleep, while here, Ross could do nothing. Only the navigator could sort this one out. So, on second thoughts, it was nothing at all like the Jarvis exercise. If only he could use his instruments for ten minutes; a sextant shot and all would be well. The turbulence within the cloud grew worse, and the darkness outside blackened still more as driving hail battered against the cabin ports. ‘I’m going down,’ yelled Ross, ‘we could be icing up soon.’ And that was the end of any chance they might have had getting over this particular cloud formation.

The dreaded Cumulo Nimbus cloud in tropical climates can range in height from sea-level to sixty thousand feet, spread for hundreds of miles. ┬áIf glazed ice began forming on the leading edges of the wings, stability would deteriorate until the aircraft became unmanageable. As the York sought a new, lower, ice-free level B was carrying out further checks; first that the gyro heading indicator was synchronised with the magnetic compass, and then that the flight log had been correctly calculated. There were no errors anywhere; Freddie had been as accurate as ever in spite of his indisposition. He made a quick dead reckoning calculation of their position with a circle around it, having a radius of 10% of the distance flown from Changi. This circle of uncertainty gave him what he wanted. It is assumed that a lost aircraft is somewhere within such a circle. There is a 1 in 60 rule in navigation that says an aircraft one degree off course will be one nautical mile off track, after flying sixty nautical miles. The formula says, 60 over distance flown, times distance off track, equals track error in degrees. It is accurate up to 20% so long as it is calculated on or before the half way position of the leg, and can be used for a course correction. With the theory now all nicely worked out he could do nothing further without a bearing because, in a circle of uncertainty it wasn’t possible to know whether to correct to port or starboard, nor by how much.

Ross had levelled out and was waiting. To concentrate he had drawn the curtain across the navigator’s port hole and the lighted angle-poise lamp gave his work place a cosy, den-like atmosphere. He wished for a moment that he didn’t have to take a decision. There was no navigational text book could help him out here. He knew that going down below a monsoon cloud of this size was the wrong thing to do. The turbulence would be tremendous, and if there had been any mis-setting of the altimeter at Changi, sea-level wouldn’t be where they should be heading. But they couldn’t get above the cloud and they couldn’t carry on as they were at present, lost and maybe heading into the Indian Ocean, running low on fuel. So, where else to go?

There is a way of getting wind velocity from a point on the surface, in this case, the sea, if you can find a point, and hold it long enough to make the reading meaningful; and then, if you managed to get a reading, a calculation had to be made to adjust for the different wind angles, as surface wind angles varied from the winds at higher altitudes. And then there is the fateful assumption that the figures you come up with have been constant for all of, or most of, the previous flying time. It was so tenuous that he hesitated to set the idea in motion. He sat there, having thought it through, and needing an impulse to launch it. This came with the sound of Ross’s voice, ‘Any ideas, Bill?’ ‘Sea level, a wind check, then re-calculate a new course.’ He bit the words back, half fearful of letting them out. Ross raised an affirmative thumb and down they went.

The cloud base varied between five hundred and a thousand feet above sea level and, as expected, the turbulence made flying in that zone perilous. and the idea of finding and keeping a fixed point under such conditions seemed to be quite unrealistic, but Ross knew what was wanted and, in spite of the fierce upward currents of air buffeting the plane about, he persisted at the controls in keeping as level a course for as sufficiently long for a sighting to be obtained. B watched for surf tops and ridges of distinguishing waves ahead, and plotted the lines, once, twice, three times. They were sure to be crude, but the result might show on which side of the circle of uncertainty they were on.

He signalled to Ross and the York rose again to be shrouded once more into the cloud mass, as he bent over the work table, holding his mind back from racing over the calculations. These showed that they were slightly outside the circle on the port side. More calculations followed. What were they? What were they? Come on; come on. Double the error and apply it to the required track at a distance ahead that is equal to the distance already travelled.. And the new course will then be…..what? he stared at the result. This is what he had to give to Ross; and get them to Negombo. Or would it? His own circle of uncertainty was closing in on him. He jerked, and handed over a slip of paper, getting back an unequivocal stare. Ross began to set the new course, and when this was done, turned the paper over and wrote on it before passing it back. ‘It’s Berlin or bust,’ B read, ‘can you calculate our remaining fuel?’ This he could do fast, as it was a fairly straight forward check. He made the calculation as well as the gallons per nautical mile to destination. Ross studied figures for a few seconds, before calling Tash. The margin was narrow and the engines were throttled back. All they could do now was to fly the plane in the obscurity of the monsoon clouds and wait.

B went back to have a look at Freddie and found him sleeping sweetly, his breathing even and relaxed. The passengers needed some reassuring; most of them had been sick and appeared to be in various stages of dejection; the air smelled stale and vomit scented. he tried talking to some of them, but it was difficult over the roar of the engines, so he left them and returned to the crew cabin.

The York remained in the turbulence of the cloud until late in the afternoon, and when they emerged into the sunlight, the dazzling, tropical brightness of its shining slantwise on to the sea was like an uplifting boost to their tired spirits. There was an easing of tension as the crew relaxed back into their seats. Within half an hour they spotted a ship and shortly afterwards the sight of land. ‘Are we back at Changi? asked Johnny with an air of innocent mischief. It was not Changi, but the south-eastern coast of Ceylon and, whether by luck or judgement they had only to fly due west, across the island to reach their destination. Ross turned and gave a great grin.

1947