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the gremline digest — listen to the warning bells
Listen to the Warning Bells
Every pilot has, at some time during training, been warned of the danger of pressing on with a flight when there is some doubt about the safety and suitability of conditions for the continuation of the flight as originally planned. Every pilot has, at some time during training, been told that it is dangerous to submit to pressure to reach a planned destination when something, however apparently trivial at the time, sounds a warning bell in the pilot’s mind. Many pilots will experience the well-concealed feeling of relief at the end of a flight that has pushed the boundaries of their own skill and experience just a little too far. Pilots who live to grow old will learn from their brush with the outer edges to increase their skills instead of pushing their luck.
Sadly, all too many pilots ignore the warning bells in their own minds and, despite a whole chain of warnings, push beyond the boundaries of their skill and experience – and pay with their lives. The only good that can come from these avoidable accidents is that others may learn not to ignore the warning bells when they sound, however faintly, in their own heads. Listen to the warning bells.
A 66 year-old man had owned a 36 year-old Cessna F150F for several years. He held a Private Pilot’s Licence and had accumulated a total of 1,054 hours flying experience, with 331 hours on type. The aircraft was normally based at Popham Airfield in Hampshire but was occasionally based at Enniskillen Airfield in Northern Ireland. On Wednesday 6 February 2002 the pilot began a flight from Enniskillen, planning to return to Popham with a refuelling stop at Blackpool Airport. The aircraft engine developed rough running on the leg between Enniskillen and Blackpool, forcing the pilot to seek engineering assistance on his arrival at Blackpool at 12.40 hours. One may assume that his original plan was to refuel at Blackpool, depart at about 14.00 hours and arrive at Popham at about 16.30 hours. He was informed that it was not possible to repair his aircraft until the following morning. Listen to the warning bells.
The pilot found local accommodation for the night and returned to the airport next morning to continue his flight to Popham. The engine was run, and replacing one spark plug and cleaning and adjusting the others rectified the fault. During a further engine run there was a RPM drop on the left magneto that was just within limits. It was suggested to the pilot that further work was advisable. The pilot decided to continue the flight to Popham and have the RPM drop rectified later. Listen to the warning bells.
The aircraft was refuelled to full tanks after arrival at Blackpool, giving maximum endurance of about three hours. The planned route would have taken 2 hours 10 minutes in still air and 2 hours 40 minutes in the prevailing wind conditions. The aircraft was not topped up after the engine runs during the rectification work. Listen to the warning bells.
The pilot telephoned a pilot colleague who was in London at about 10.00 hours and said that high winds were forecast and he was concerned about being able to get tie-downs for his aircraft if he stayed at Blackpool. He called the colleague again at midday and enquired about the weather along the planned route to Popham. His colleague expressed concern about the forecast headwinds and held a transceiver to the phone so that the pilot could listen to the VOLMET broadcast. Listen to the warning bells.
The planned route was Blackpool – Manchester Low Level Corridor – Stoke-on-Trent – Lichfield – Daventry – Westcott – Stokenchurch Mast – Popham. The pilot called his friend again at 14.00 hours to say he was about to depart Blackpool and “Regarding the weather problem, I might pull into White Waltham.” The pilot took off from Blackpool at 14.38 hours and declared his destination as Popham, although no flight plan or arrival booking was received at Popham. If all had gone as planned, he would have arrived at Popham at 17.18 hours, 15 minutes after sunset. Blackpool ATC reported the cloud base to be 200 feet and the controller was concerned to see the aircraft enter cloud soon after take off. The controller called the aircraft and the pilot reported that he was “Clear on top.” The pilot had once held an IMC rating but it had expired. Listen to the warning bells.
The UK Met Office Low Level Forecast (Form 215) valid for the time of the planned flight showed a cold front lying from Cardiff to Hull and a warm front from Southampton to Hull, with both fronts moving south-easterly at 20 to 25 knots. Between the fronts (which included the final leg of the flight to Popham) the forecast gave extensive cloud based at 800 feet with occasional areas of stratus at 200 feet and visibility of 1,500 metres in rain, drizzle and mist. Cloud on the hills was forecast both north and south of the cold front. Predicted winds were 230/20 knots at 1,000 feet and 250/35 knots at 2,000 feet. The Blackpool METAR was wind 230/18 knots, 4,000 metres visibility, scattered cloud at 200 feet, broken at 1,200 feet, overcast at 2,500 feet, temperature 10C, dew point 9C and QNH 1007 millibars. Listen to the warning bells.
Popham Airfield is at 550
feet amsl. The controller there estimated that the cloud base was less than
100 feet and visibility was about 400 metres at 16.00 hours. Odiham Airfield,
11 nm east of Popham and 405 feet amsl, had the following weather at the Cessna’s
projected arrival time:
The pilot had a GPS unit to assist with his low level navigation along a route apparently planned to avoid penetration of air traffic zones between Blackpool and Popham.
The pilot did not make any radio calls except on departure from Blackpool and during his transit of the Manchester Low Level Corridor. A colleague who regularly flew with the pilot stated that the pilot did not normally use the radio unless necessary, other than to update the QNH by monitoring relevant frequencies. His flight into deteriorating weather took him close to several airfields such as Brize Norton and Benson that could have provided assistance with an air traffic service. The pilot did not ask for assistance although he must have realised that his situation was becoming more and more hazardous. Listen to the warning bells.
The last known contact with the aircraft was at about 17.00 hours when it was seen flying in a south-westerly direction, below 500 feet and being buffeted by strong winds. There was patchy rain and poor visibility and it was beginning to get dark. The aircraft was about ten miles from impact.
At 17.14 hours the aircraft struck and severed the earth cable between power line pylons some 100 feet above the ground. The aircraft was under power and close to level flight on a south-easterly heading when it struck the cable. The aircraft continued for 170 metres before impacting the ground in a direction of 115 degrees magnetic, it then bounced some 30 metres further before coming to rest after rotating 160 degrees to the left. There was no fire after impact and the fuel system remained largely intact. There was no more than a total of 18 litres of fuel in the aircraft at impact. The Flight Manual states that 13 litres of fuel is unusable so the aircraft had only 10 minutes of flight time remaining.
Two local residents in their house near the crash site saw a big blue flash and heard a loud bang at the time of the crash. They assumed this was a lightning strike associated with the bad weather. The husband of one of the residents arrived home at 18.05 hours and mentioned seeing an electrical cable lying on the road outside. They telephoned the local electricity board to report the broken cable. Engineers from the local electricity company and from the National Grid arrived at 18.35 and 18.45 hours and discovered the cable to be the earth cable that runs between the tops of the pylon towers. They were unable to see the tops of the pylons because of low cloud.
One of the residents mentioned hearing an aircraft before seeing the flash. One of the engineers then remembered something catching his vehicle’s headlights as he approached the site. He returned to search the area and found the aircraft in a field beside the road. The pilot was injured but conscious. First aid was administered and the emergency services arrived shortly afterwards, at about 19.30 hours. Sadly, the pilot suffered a cardiac arrest on the way to hospital and died later that evening. The aviation pathologist’s report suggests that the pilot’s injuries were probably survivable had he received prompt medical attention.
The pilot appears to have put himself under some pressure to complete the flight from Enniskillen to Popham. He was delayed overnight at Blackpool by a rough running engine and advised that the aircraft needed further work after the rough running was rectified.
The weather en route was not suitable for a VFR flight to Popham. The forecast was displayed in the pilot briefing room at Blackpool Airport. The pilot’s colleague expressed concern about the weather before the pilot departed from Blackpool. The pilot did not contact his destination, Popham, and would have been warned of the very poor weather there if he had done so. Departure from Blackpool was delayed by the necessary maintenance work on the aircraft so that arrival at Popham would have been at 15 minutes after sunset even if the flight had gone according to plan. The Blackpool ATC controller was concerned about the weather conditions as the aircraft departed from Blackpool and immediately entered cloud. The pilot did not have either a current IMC rating or a current night rating.
The pilot could have asked for assistance from airfields close to his route, or from the Distress and Diversion Cell at London Terminal Control, and this may have prevented him continuing into the trap between high ground and low cloud.
Most of the high ground on the planned route was along the last leg from Stokenchurch Mast to Popham and this coincided with the lowest cloud and worst visibility. The dominant obstacle along this final leg was Hannington Mast at 1,226 feet amsl (498 feet agl), very close to the crash site. The pilot’s map did not show obstacles below 300 feet agl. The cable he struck was about 100 feet agl.
Replay of the
pilot’s GPS receiver data showed an irregular track south of
Stokenchurch Mast that avoided high ground and tried to exploit low ground.
This suggests that cloud was covering the high ground and the pilot was
trying to find a way through the Chiltern Hills. He skirted Henley-on-Thames,
three miles east of planned track and could have diverted to White Waltham
from there without having to cross more high ground. However, he continued
towards Hannington, in the general direction of Popham. The trap had sprung.
He was faced with at least four serious problems.
This article is closely based on the facts of accident report Reference EW/C2002/02/02 published in AAIB Bulletin No.10/2002, which source is gratefully acknowledged. The inferences drawn and comments are those of the author and not of AAIB. The full AAIB report is available at www.aaib.gov.uk
Text and Photographs © 2007 Gremline & Hill House
Publications, unless otherwise stated.
Text and Photographs © 2007 Gremline & Hill House Publications, unless otherwise stated.