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Gremline Flight Safety Report: A Ditching That Went Wrong / Beware Large 'Sailing Ships'

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the gremline digest —  a ditching that went wrong / ‘sailing ships’

Gremlins at Gremline!

We apologise for our failure to publish articles and news items in October. This was due to a catastrophic hardware crash. After several on-site tech visits (and a little discussion with the mother ship) the man from Dellmonte has replaced the equipment, so life should go smoothly from now on.

 

A Ditching That Went Wrong
(For advice on ditching light aircraft and sea survival, go to the March 2007 and April 2007 issues of Gremline.)

A 45 year old pilot with 50 hours total experience planned a solo navigation trip around the North Yorkshire Moors from Durham Tees Valley Airport in a Piper PA-38 Tomahawk. The weather was good when the aircraft departed at 1452 hrs and turned south-east while climbing to 1500 feet. He changed frequency and obtained a Flight Information Service from a radar controller who identified the aircraft, verified its Mode C altitude readout and cleared the pilot for further climb not above 4000 feet en route. The pilot resumed climbing and headed towards the Whitby area.

 

 

Some time later the controller observed the aircraft at 1300 feet over the Whitby area. This did not concern her as aircraft often descend in that area to view the scenery. At about 1515 hrs the pilot of another aircraft heard the transmission: “MAYDAY MAYDAY MAYDAY OSCAR FOXTROT FORCED LANDING”. When the radar controller did not reply the pilot relayed the MAYDAY call. The controller had not heard the original call, tried to contact G-BOLF without success. The other pilot also tried, also without success. The controller passed the last know position of G-BOLF to the pilot of the assisting aircraft who searched the area just off Robin Hood’s Bay without success.
      One witness at Robin Hood’s Bay heard an aircraft engine at about 1515 hrs with the sound increasing to high power, reducing to low power and then increasing again. He assumed that the aircraft which he could not see was performing aerobatics. Shortly thereafter he saw an aircraft flying low over the sea on the other side of the bay.
      Witnesses at Ravenscar saw a small single-engine aircraft heading in their direction, just above cliff top height and descending gently towards the sea in an apparently controlled manner. When it was just above the surface the right wing dropped, the wingtip contacted the sea and the aircraft cart wheeled. It became inverted and quickly sank.
      Search and rescue aircraft, lifeboats and the Coastguard were dispatched to the area but neither pilot nor aircraft could be found. The aircraft was found later that evening, at low tide. The pilot’s body was recovered on the following day.

 

 

The Accident Investigation
Examination of recorded radio transmissions confirmed that a MAYDAY call was made at 1514.48 hrs and the words “ROBIN HOOD BAY” and “ATTEMPTING FORCED LANDING” could be heard.
      The weather in the Robin Hood’s Bay area was good with a 2000 foot wind of about 17 kt from the west and a temperature of 6C with a dew point of 3.7C giving a relative humidity of around 85%. When these figures are plotted on the CAA Carburettor Icing Prediction Chart it gives a prognosis that serious carburettor icing could occur at any power setting between 1000 and 3000 feet amsl.
      Examination of the wreckage after the tide had ebbed showed it to be inverted with major damage to the outer right wing and a twisting failure of the rear fuselage forward of the tail unit. The engine cowlings, right landing gear, cockpit windscreen and cockpit doors were torn off either during impact or while lying on the sea bed. The propeller showed evidence of not being driven at impact. The flaps were fully deployed, fuel was selected to the left tank, and the throttle was fully open with mixture almost fully rich and carburettor heat on. The fuel primer was in and locked. The electric fuel pump, landing light, pitot heater and engine ignition were all selected off. The fuel tank drains were closed and there was no evidence of an airborne fire. There was no evidence of pre-impact failure of the flying controls, fuel system or engine operating system.
      The engine was examined in detail at an overhaul facility and was found to be in very good condition consistent with the hours since overhaul. The engine-driven mechanical fuel pump was found to be stuck in an unusual position. There was possible evidence of stiction
(i.e. static friction or friction that tends to prevent relative motion between two moveable parts at their null) on the central spindle. The central spindle was slightly bent in the area of the stiction marks. The pump had been fitted new about 1500 operating hours before the accident and had not caused any reported problems. Two other pumps of the same type were examined for comparison and both had similar marks on the central spindle but neither spindle was bent. The electric fuel pump functioned satisfactorily, even after 24 hours immersion in the sea.

 


The post-mortem revealed that the pilot had survived the impact but died from drowning. This suggests that he was able to extract himself from the crash but then drowned. None of the witnesses saw the pilot in the water. He was not wearing any flotation aid. There was no evidence of disease or toxicology that could have contributed to the accident.
      It was apparent that the aircraft had suffered a loss of power. Although the conditions were conducive to carburettor icing and this could not be ruled out, this does not appear consistent with witness reports of hearing an engine increasing to high power then decreasing and increasing again. It was not possible to determine the reason for the power loss. It is possible that the pilot could, theoretically, have achieved a forced landing on land but this would not have been obvious to him as the nearest land was behind him and hidden by the wing. He was probably concentrating on making a MAYDAY call and trying to restore engine power. By then the aircraft was probably beyond gliding distance to land. It appears that the aircraft stalled just prior to entering the water, causing the right wing to drop and the aircraft to cartwheel into the sea.
      CAA Safety Sense Leaflet No 21 contains detailed advice on ditching a light aircraft. The main cause of death after ditching is drowning. The details of this accident and the subsequent investigation are taken from AAIB Field Investigation Report EW/C2008/10/03 which source is gratefully acknowledged.

 

Be Prepared!

The following comments are those of the author and do not seek to reflect the views of AAIB nor to be critical of any actions taken by the pilot following the engine failure. They are intended to provide suggestions to other pilots on how to avoid a similar accident. The pilot who was killed in this sad accident had only accumulated some 50 hours flying experience and may have never had any training in ditching a light aircraft. He may have never even considered the possibility of being faced with a ditching. A ditching is a forced landing into water and the primary aim is to fly the aircraft accurately throughout the descent and touchdown. Everyone will benefit from careful study of CAA Safety Sense Leaflet No.21 Ditching and following the detailed advice contained therein. All the excellent CAA Safety Sense Leaflets may be downloaded for free by entering “CAA Safety Sense Leaflets” into your search engine.

 


Beware Large ‘Sailing Ships’

A very interesting picture appears in the Autumn 2009 issue of Air Transport CHIRP Feedback. The photograph, taken from a CHC Helicopter in the southern North Sea, shows a large vessel (oil tanker?) at sea with what looks like a very big parachute flying above and ahead of the ship and attached to the ship’s bow by a cable at least 1000 feet long. This is the experimental “Skysail” system that is part of a research project to use wind power to augment current forms of propulsion for large sea-going vessels.  The designers of “Skysail” and a number of authorities are collaborating to safely integrate this activity with offshore aviation. It is recommended that any sightings of “Skysail” ships be reported to ATC to permit other aircraft in the area to be alerted. Obviously it would be wise to give these vessels a wide berth and to avoid overflying any vessel at low level as the cable presents a potential hazard to low flying aircraft and may not be easily seen.

 

 

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