Was that a Heavy Landing?
Back long ago in the early ‘70s when I was a young engineer, I worked for the then Department of Civil Aviation (DCA) as an ‘Aircraft Performance Engineer’. I had a rather unusual position in that I was employed by the Vic/Tas region of DCA, and was responsible for Victoria and Tasmania, but I was also the responsible aircraft performance specialist for South Australia, Western Australia and the Northern Territory. Back in those days DCA took the responsibility for ensuring that aircraft met their performance criteria and prepared performance charts such as take-off and landing charts. In those days DCA was actively involved in the actual testing process rather than merely reviewing company produced data as CASA does today.
On 1st December 1973 I was the official DCA flight test engineer on board a four engine DH114-2D/A1 ‘Heron’, VH-CLX, a small 16 seat piston engine airliner operated by Connair (Connellan Airways), an outback airline (unfortunately no longer in existence) based in Alice Springs. Connair had modified their fleet of Herons by replacing the original Gypsy Queen engines with IO-540 Lycomings. As a result of the modification the take-off and landing performance of the modified aircraft had to be measured and new performance charts drawn – my job. Unfortunately the DCA regulations of the day required a 43% margin on the landing performance. This meant that if the aircraft actually required 1000 metres to stop from a height of 50 feet, the required runway length would be 1430 metres. These aircraft were to spend much of their life operating from rough bush strips so with the margin of 43% to be added it was vital that the actual flight test measured landing distance was as short as could possibly be achieved. That is the job of a properly trained and proficient test pilot. Consequently the best and most experienced test pilot available was hired for the job – I won’t mention his full name, he is now deceased, sufficient to say that his first name was Stuart and he was the father of a current famous movie and TV actor – any guesses?
Anyway on the day in question we were doing the landing tests at Alice Springs airport. Stuart was flying and I was in the right hand seat acting as both co-pilot and flight test engineer. The aircraft was ballasted to the worst case performance scenario, full forward centre of gravity and maximum landing weight. The technique required to achieve minimum landing distance was to approach through 50 feet at the minimum legal approach speed of 1.3 times the stall speed with full flap, chop the power on all four engines, immediately push the control column forward to maintain flying speed (the Heron had absolutely wicked flaps with huge drag in the landing position) followed almost immediately by hard pull back on the controls to achieve a very ‘firm’ landing. Maximum braking was then applied until the aircraft stopped. Distance was then measured. This process was to be repeated five more times so that the distances could be averaged.
On the fourth landing Stuart didn’t manage to get the ‘push-pull-thump’ sequence just right and a very firm landing resulted. Stuart looked across at me and asked, “would you consider that a heavy landing?” I had to concede that I did. We taxied the aircraft to the hangar and reported the heavy landing. The engineers did a careful inspection and looked for damage in all of the areas listed in the ‘heavy landing’ inspection schedule. No damage was found so off we went to do the remaining landings. Three more landings were completed with Stuart getting the ‘push-pull-thump’ sequence perfect each time. After the last one Stuart taxied the aircraft back to the Connair flight line and we both raced off to the terminal to catch the midday jet back to Melbourne thinking no more about it.
Next morning I went to work as usual but was immediately contacted by the air safety people (then part of DCA). “What did I know of the aircraft crash in Alice Springs yesterday?” “What crash?” I asked. It was the Heron. They then showed me the photographs – the aircraft fuselage was bent in the middle just like a banana! Apparently the heavy landing had broken some stringers and other structural members in the fuselage under the floor but no engineer had looked there after the heavy landing as that area was not mentioned in the approved heavy landing inspection schedule. In hindsight I am surprised that nobody noticed some form of external damage in the area but nobody (including me) did. With no damage found Stuart and I continued with the tests without giving it another thought. Clearly each subsequent landing did a bit more damage to the already weakened area and by the time the last one was completed the damage was quite extensive. In our rush to catch the flight home we didn’t even look back so we were both quite oblivious to the damage that had occurred.
In reflection the heavy landing in VH-CLX was one where there was some doubt at the time as to whether or not it should be classified as a heavy landing requiring inspection. All pilots will at some time in their flying career make a landing where this judgement call has to be made. Aircraft are not fitted with a ‘heavy landing meter’ so it is purely the judgement of the pilot as to whether or not to report the landing as a heavy landing. In our case we chose to report it, but even then the damage was not detected during the ensuing inspection. Fortunately the aircraft went back to the maintenance hangar after our final landing and the damage was discovered before any fare paying passenger’s lives were put at risk.
The moral of this story - report any landing that could be perceived as a heavy landing even if there is some doubt. That way the aircraft can be inspected and repaired if necessary before any further damage is incurred.
So where is VH-CLX today? It underwent extensive repairs and returned to airline service with Connair. It finally finished its airline career with Airlines of Tasmania and has now been retired and is currently a static display at the Moorabbin Aviation Museum.