SO WHAT WENT WRONG ?
What follows is purely speculation - using hindsight, a degree of guesswork and factors that were not considered directly relevant by the accident enquiry.
Given the great experience of the crew it is extremely difficult to accept that the Captain acted in an irresponsible or cavalier way - he had flown the route 90 times in the last year and had just passed an instrument landing check. However planes just don't fly into hills, and the weather seems to have been a major factor.
Logically, the crew must have been deceived as to their exact location, and theories for this are reasonably easy to construct. However there is a much wider aspect which the enquiry considered at length but did think relevant to the actual accident - how could an airliner on a short domestic flight between two local airports, be flying on the limits of operating procedure where a matter of seconds would mean life or death to fare paying passengers. And why was this permitted when the authorities knew these bad weather flights were taking place?. You may feel that this was never fully resolved.
However given that the plane was in the air that day, there are two questions - firstly why did the crew not see the coastline and avoid it, and secondly how could an experienced crew have been misled into flying the plane into that position in the first place.
INSTRUMENTS
The plane had a single receiver for use with non directional beacons. This was working as far as is known, but was unreliable at low altitude, and the local beacon at Thorney Island was masked by the mass of the Island. Additionally the weather conditions weakened the signal, and thus the NDB system would have been of very little use in the circumstances. It might even have given a false indication, but the crew would have been aware of this possibility.
VISIBILITY
These two photographs show what we believe the crew thought they would see as they approached the coast. Thick cloud, but relatively clear visibility beneath - we think that they hoped to break into clear air just above the minimum regulation height for flying over water ( 500 feet ) and believed that there would be fleeting glimpses of the sea and coast from 1000 feet, making it safe to approach the Isle of Wight at a relatively low level. Then by keeping visual contact round the coast, and while crossing the Solent, they could make a low level approach into Portsmouth. They had tried a standard instrument approach a few hours earlier and had been unable to see the airfield, so if their passengers were going to get home, this was the only way.
The pictures are of a hillside on a very foggy day with a blanket of cloud about 300' asl. The hillside continues for several hundred feet upwards into the clouds, but if flying low over the sea, and relying on the forecast weather, there would be sufficient time to avoid an obstruction. Reducing height in this way while over the sea did not break any safety rules and was a standard procedure.
The weather forecast given just before take off was:
3/8 - 6/8 cloud between 600 - 1000 feet
Possibility of complete cloud cover on exposed coasts
Surface visibility 6 - 10 miles but 1 - 2 miles in rain
Extensive hill fog
Visibility 500 - 1000 yards in hill fog
Wind Westerly 15 - 18 kts gusting to 30 kts.
This early picture of Ventnor shows St Boniface Down looming up behind the town. The crash site is to the extreme right of the photograph. Although the top of the Down would have been obscured partially or completely, the crew would be expecting at least 2 or 3 times this distance of visibility from the photographer to the base of the Down as they approached the coast. With the town between them and high ground, there would have been little chance of missing the coast.
Unfortunately local visibility was like this.... a few feet.
At the time of the accident, witnesses on the Down said visibility was almost nil and the cloud appeared to come down virtually to sea level with a base about 300 feet. Conditions were so bad that people within yards of the accident neither heard nor saw anything until alerted by someone literally on the spot. This is not uncommon on this coastline and a number of aircraft have hit the the hills in dense fog.
NAVIGATION
The accident enquiry stated that the crew were given an accurate weather forecast.... unfortunately no forecast can ever take highly localised conditions into account and it is not intended to do so. However it is also the basis for navigation, particularly in poor visibility. Flying a local route in 1962 wasn't like todays choreographed operations and the crew were relying on split second timing, their own navigation using dead reckoning, literally lines drawn on a chart with a pencil, and a sharp lookout to position the plane just off the Island for the next part of the approach. It was pencil, paper, and Mk 1 eyeball. Today, radar and GPS satellite navigation would have the position fixed within a few yards - then they could be a few miles miles out and not know it - indeed some famous cases in the 1950's had planes actually flying in the opposite direction due to basic mathematical error by the navigator. These two pilots were navigating and flying the plane and did not have a third man on the flight deck to assist, but they would have appreciated that all navigation needs to build in a safety factor to account for the unexpected.
In this case they would have been allowing 5 miles between the plane and any solid obstruction, and thus they were either reckless, which seems highly unlikely, or badly deceived as to the correct position. Given that the aircraft appears to have been aborting the descent when it hit the hill, it is possible that the crew believed they were at the edge of their safety margin - but to be this far out on a short flight indicates that something was seriously wrong.
Dead reckoning relies on plotting a projected track and positions at any given time, based on input from known factors. The main ones are the speed of the plane and the wind which will blow the aircraft off course - thus to go where the Captain intends, the crew have to fly in a different direction so that the wind can be counteracted. Winds vary with height and generally increase the higher you go. While weather prediction is reasonably accurate, it is not precise, a forecast is just that, it is not a statement of fact. Later interpretation of the charts has suggested that the wind speed may have been underestimated, especially in mid channel where again, speeds are generally higher. This was well within the margin of error but additionally we know that the island was covered in cloud and that this was lower than anticipated and extended further out to sea. Thus if the wind was a little stronger, the plane would have been travelling faster than expected and would have reached the coast - and a fog bank - a few minutes sooner.
Weather reports after the accident hinted at a slight but significant difference in the wind direction, although both were virtually on the tail for the main part of the flight. There is just a possibility that a higher speed and a more Westerly wind would have made a significant difference to the plane's track, blowing it further East and increasing the ground speed. My amateur plotting indicates that the difference, taking the worst case, would have been about 5 miles ahead of the expected position and making landfall at the very point where the Isle of Wight reaches furthest South - thus two factors would be reducing the safety margin.
Additionally the first leg to Alderney would have had the wind to Port (left) and thus pushing the plane East. It is perhaps interesting that although the 'official' flight plan provided by the enquiry shows the plane's track crossing Alderney, the crew reported Alderney 'in sight'. They did not say they were overhead. This may be irrelevant - or it might confirm that they were already off track due to a higher wind. Again, we can never know, but the choice of wording in flying 'speak' is a precise matter and hence this may possibly be significant.
If the cloud was lower than 500', then by maintaining a safe altitude, the crew would actually have been too high to see the sea and to get into position to make a visual approach, but reducing height to low level in poor visibility can be dangerous as it is difficult to determine where the sea ends and the sky begins. Everything they did in these circumstances would have been aimed at fixing their position off the coast or giving up the attempt in good time to climb clear of the Island, so by adhering to the rules the problem was potentially made worse. Normally this would have been no concern as the aircraft would not have been attempting to land at an airport where an ordinary instrument approach was highly unlikely to succeed. However, for reasons not entirely clear, they were doing just that, Channel did operate to the limit of weather minima, and they had no modern navigation aids to help them. It was all perfectly safe - as long as they could pick up the coastline.
Immediately before the accident the plane was climbing and turning right and while this may have been an evasive manoeuvre, as suggested by the airline, but there is no record we have seen to suggest any violent alteration in direction or emergency increase in engine noise until immediately before the impact. With piston engines any change would have been immediately noticeable. Thus it seems that power was being re-applied, but at a standard rate to enable the plane to abort the descent and climb back to a safe height. That would indicate the crew thought they were within the safety zone and were responding normally by giving up the approach and diverting to Southend.
Having found that the cloud did not clear at 600 feet as forecast they began a climb back to their original cruising altitude and were turning away from the coast which was hidden in a wall of fog and cloud. Unfortunately the weather had closed in and instead of breaking into clear air they found themselves still in a wall of cloud that was lower than expected ( although the forecast did clearly state 8/8 cloud on exposed coasts ) - with the expected wind, they would have believed the plane to be approaching the minimum 'safe' distance of five miles from the nearest obstruction and at a point where the coast was further away and much lower - unfortunately the aircraft was further East at the one point where the coast projected further into the Channel, and the plane was 5 -6 miles ahead of the expected position due to the winds. They were turning, believing they were safe over open water - and flew headlong into the hillside.
After two years research, that is my best guess as to why this tragedy happened.
But there is an alternative.
If the crew were peering through misty plastic windows in rain, looking for a fog shrouded coast line, believing that they would have a clear view when they reached it - and enough time to turn away, and if the aircraft crossed the coast where it was obscured because the cloud was much lower than anticipated, there might have been a fleeting glimpse of the left hand side of 'Coombe Bottom' . This would have appeared in the right place at the right time, on dead reckoning, and would have looked exactly like the hills on the edge of Sandown Bay. If the plane was on track, the crew would not have expected to make landfall at a point where the hills were as high and steep while the chance of being in a blind gully was so remote that no reasonable navigator would have considered it on a half hour flight. Thus, instead of flying along the coast, they were now in a valley about a mile further back and just too low to clear the top of the Down. However they saw what they expected to see - the hills along the edge of the coast. They began to climb as they had planned and turned right to cross Sandown Bay, possibly intending to climb back to cruising altitude and head for the Portsmouth beacon to use an instrument approach - and flew directly into a hillside when they expected to see open water.
Nothing was illegal. Nothing was reckless. Luck should not play a part in aviation, but occasionally it does. In hindsight actions may have been highly inadvisable, based on today's procedures, but our current attitude only came about from experience, and that was formed in part by accidents like this. Perhaps the best guess is that a combination of the forecast, the local deterioration in weather, a conscientious crew trying to get their passengers home, lack of working ground navigation aids and pressure to operate the service on the limit of prudence came together in one fateful moment to put a loaded passenger aircraft headlong into a hillside.
The modern attitude is to say it was an accident waiting to happen - the opposing view is that it had been done thousands of times before without any trouble, and this was a tragic case of that fatal pyramid of circumstances - everything going wrong at once. We can never know.
However this leaves a question we are unable to answer - and one that perhaps should have been answered by the enquiry. Why were loaded passenger planes even attempting to use Portsmouth or any other airfield in the conditions known to exist, when fundamental issues regarding safety and navigation facilities had not been resolved and had been virtually sidelined by the Ministry of Aviation despite acknowledgement of the potential for a disaster.
That was never satisfactorily answered - and yet the same Ministry were ready to blame the pilot when the reason for, if not the cause of, the accident could not be formally determined.
While the Ministry were too busy with operator licensing to follow up a known and urgent safety issue, a small independent airline , no doubt trying to juggle costs, revenue and passenger convenience were trying to land a plane full of delayed holiday makers at a fogbound airport owned by a local authority where the operator had paid for a new passenger terminal yet the Council couldn't find the funds for a basic two way radio set, let alone ground approach radar. Perhaps that is the essence of the tragedy.
The captain was blamed - the enquiry described the cause as "an error in airmanship" on his part and his part alone, and because of this all encompassing conclusion, the survivors lost compensation and many questions that could have been asked, were not - or at least not as rigorously as they might have been, although he Ministry were very swift to improve the regulations and enforcement once the dust settled.
You will have to make up your mind, because the physical evidence died with the crew on that foggy hillside, but it is perhaps fitting to quote the RAF Manual of Flight Safety AP3207 Chapter 8.
"Only in cases in which there is absolutely no doubt whatsoever should deceased aircrew be found negligent".
You decide.