Mervin Sims: A True WWII Tale of Survival

Written by Cliff Adams, former 418 Squadron Association Vice President and Historian

The Douglas DB7b "Boston III", serial number Z2186, was parked on a dispersal pad at RAF Station Bradwell Bay on October 17, 1942. It was fueled and ready for flight. Painted matte black with dull red markings, the aircraft bore the squadron code and aircraft designation TH - S. TH was the code assigned to 418 Squadron R.C.A.F. The aircraft was an Intruder; a specialized aircraft for a specialized role; intended to take the fight to the enemy by night. Today however was a scheduled training flight rather than a mission. The crew of three arrived at dispersal carrying their parachutes and prepared for a cross-country navigation flight to the west coast of England over north Wales. New pilots and their crews needed to train together to gain experience and confidence so they could work as a team when prowling near enemy airfields at night waiting for returning enemy night fighters. Intruding was very dangerous work.

Flight Sergeant Mervin Harold Sims (R.C.A.F.) began his customary walk around the aircraft. Newly posted to 418 Squadron, Sims was careful to ensure the snubbing pin in the nose gear was secure and checked that there were no fluid leaks in either of the wheel wells of the aircraft. The main gear looked solid enough and the tyres were nearly new. His navigator, Pilot Officer Francis Longworth (also R.C.A.F.) tossed his parachute through the forward belly hatch and climbed in after it taking the navigator's seat forward in the glassed-in nose. He would be busy for the entire trip guiding his pilot from checkpoint to checkpoint providing time, distance and directional information. Navigation in Intruder aircraft was strictly by "dead reckoning" with no radio beam "fixes" or position "fixes" by sunlight or starlight. Navigators needed to practice their dead reckoning skills for when they intruded by night over the continent and there were no visible landmarks. Wireless Air Gunner Sergeant Ronald Walker (RAFVR) also climbed into the Boston taking his seat aft of his pilot. Throughout the flight, he would alternately monitor radio signals and exercise the two .303 calibre Browning machine guns that served as defensive weapons for the aircraft.

Sims climbed into the cockpit, settling on his seat pack parachute and continued his pre-takeoff checklist. First, he checked the flight controls, then the throttle, mixture and propeller pitch controls which he set for engine start. Magnetos "ON" and the Wright Cyclone 2600 engines began to turn, catching quickly as Sims primed each engine in turn. First, the port and then the starboard engine came to life. Oil pressure quickly rose to normal as did the manifold pressure for each engine. Setting the altimeter and checking the operation of the artificial horizon and directional gyro occupied only a few moments and then Sims ran up each engine in turn checking the magnetos, pitch and mixture controls. Satisfied, Sims throttled back and taxied to takeoff.

Bradwell Bay had paved runways and as Sims and his crew lined up for takeoff, Sims closed the top cowling flaps. The Boston reached 135 mph and Sims gently lifted the nose. The Boston was airborne at 11:15 local time. While there was still runway underneath him, Sims selected landing gear up and raised the flaps. He leveled off at 1000 ft. AGL (above ground level), set the throttles and trimmed the aircraft for level flight.

Circling the airfield once to give his navigator a chance to get an initial time and position fix, the Boston and its crew flew west. The direction and timing for the rest of the flight would be in the hands of the navigator. Pilot Officer Longworth read out the initial heading to be taken and Sims set the directional gyro. He would reset the gyro every 15 minutes against the aircraft compass as necessary as the gyro precessed (drifted) as much as 5 or 6 degrees in those 15 minutes. Bradwell Bay receded behind them. The air was smooth but the sky was overcast with a ceiling of about 5000 ft. There was virtually no wind. Intruders normally flew at very low altitudes when on a mission so the overcast was not a problem. It would be different if the aircraft entered clouds. RAF Station Bradwell Bay was soon far behind them.

The mountainous region of North Wales known as the Carneddau (in Welsh, "the cairns") forms part of the region called Snowdonia and has some of the highest peaks in all of Wales. In October, the tops of these mountains are almost perpetually shrouded in mist and cloud and at times, the cloud layer descends almost to ground level. Hikers might certainly scale these peaks but in October it would be a cold wet walk up the side of a mountain with nothing to see once one reached the top. Carnedd Daffyd (David's Cairn) is the third highest peak within Snowdonia National Park at 1044 m (3427 ft.), and on that day much of the mountain was covered by clouds and mist.

As the Boston flew westward, the rising terrain below forced the aircraft to climb higher. Soon the Boston was flying in intermittent clouds and mist. P/O Longworth still gave his directions but because of the nature of navigation by dead reckoning, each small error in estimated position was compounded.

Figure 1.
F/Sgt Mervin Sims in flying gear. Date unknown

Soon the weather conditions would force the Boston to turn and head for home to Bradwell Bay. By now, however, the position of the aircraft was only a guess and Sims changed altitude once again climbing to 3000 ft. Their pre-planned turning point was 20 miles to the south but the crew did not know this. Suddenly the southeast face of Carnedd Daffyd appeared in front of the Boston. Sims had no time to turn to avoid the mountain so he pulled back on the control yoke to lift the aircraft over the mountain but he didn't really have a chance. The Boston slammed onto the ground just a few hundred feet shy of the peak on a gently sloping grassy col. Both engines were torn from the nacelles, the propeller tips were bent at right angles and the remainder of the aircraft began to break up. Both wings broke away from the fuselage and the tail broke away from the mainframe. Pilot Officer Longworth and Sergeant Walker were killed instantly. Miraculously Sims survived. There was no fire.

Nothing happened for a few minutes. Sims, who had been thrown from the cockpit during the crash, was badly injured. He had incurred a fractured skull and spine, a broken leg, a swollen knee and many bruises but he crawled away from the wreckage. In shock, suffering a concussion and drifting in and out of consciousness, Sims was able to gather bits of the wreckage to make a rude shelter. He would remain there cold, alone, and in pain for 48 hours.

Geologically, the Carneddau were formed during the Paleozoic (late Cambrian and early Ordovician) about 450 million years ago. The geology is extremely complex but during the Pleistocene ice age only a few thousand years ago, a thick sheet of ice covered much of Wales. The peaks of Snowdonia were much eroded by these glaciers and contributed to the flattening of the col between Dafydd and Llewellyn. It is here that Boston Z2186 crashed. Sims must have tried to pull the aircraft up, for although it had broken up, the aircraft would have been completely destroyed had it struck the mountain in level flight. We shall never know for sure, however.

The Location of Carnedd Dafydd

Figure 2.

Mt. Snowdon is to the southwest and Mt. Carnedd Llewellyn is the peak to the north. Both Snowdon and Llewellan are higher peaks. Llyn Ogwen (Lake Ogwen) is just south of Carnedd Dafydd. Boston Z2186 crashed on the (almost) flat grassy col between Carnedd Dafydd and Carnedd Llewellyn near the summit of Carnedd Dafydd.

(retrieved from https://sco.wikipedia.org/wiki/File:Conwy_UK_relief_location_map.jpg, 22, November 2020)

An account of the rescue of Mervin Sims is given in the book "No Landing Place" by Edward Doylerush (1985). In it, he writes of the discovery of the crash around noon of the 19 October 1942; nearly 48 hours later. According to Doylerush, an airman and his girlfriend were hiking upward along the ridge toward the summit of Carnedd Dafydd on one of the few sunny days there when they came across the crash and found Sims, by now in a much-weakened condition, in his makeshift shelter made from wrecked airplane parts. The airman ran as fast as he could down the mountain leaving his girlfriend with the barely conscious F/Sgt. Sims. The airman was fortunate in that Doctor Mostyn Williams was also hiking that day in the pass by Llyn Ogwen. Before climbing back to the crash site, they sent word to the mountain rescue team led by Flt/Lt Desmond Graham MD based at RAF Llandwrog. Graham had previous climbing experience and had advocated for months with the authorities for improvements to mountain rescue both in techniques and in better equipment. The Boston crash was one of the first examples Dr Graham cited in his need for better equipment and better training for mountain rescue personnel. Williams and the unnamed airman then climbed upward from Llyn Ogwen on a fairly steep slope to Ffynnon Lloer (Well of the Moon) by following the stream draining this small tarn. From there they climbed higher until they reached the crash site. Dr. Williams treated Sims as best he could but had to wait for the mountain rescue team to arrive to take Sims down the mountainside. The rescuers followed the same route down as Williams and the unnamed airman had taken on their rush back to the crash site. At Ffynnon Lloer, Sims was treated by the RAF Doctor as well, before being carried the rest of the way down to Llyn Ogwen. A waiting ambulance carried Sims along the road to Bangor, Wales and the hospital there.

Topographic map of Carnedd Dafydd

Figure 3.

The red star indicates the approximate position of the crash, the yellow arrow indicates the presumed direction of flight just before the crash and the purple dotted line indicates the route taken by the rescue party. Normally the route to the summit of Carnedd Dafydd would take the hiker first to the peak of Pen Yr Ole Wen and then northeast along the ridge to the higher peak.

Retrieved from https://www.the mountainguide.co.uk/wales/carnedd-dafydd-map.htm (Accessed 26 November 2020) Colored annotations added later by the author.

Fixing the precise crash site is somewhat difficult because the wreckage was scattered over a fairly large area, and the scar made by the crashed aircraft was never mapped. A photograph of one wing section (Figure 4 below) shows the slope of the mountain downward towards the base of the mountain at the east end of Llyn Ogwen. That wing section is now preserved in the Aviation Museum at Norwich, Norfolk in East Anglia. The roadway seen from left to right in the figure is the A5 terminating in Bangor, Wales. about 20 miles away.

Figure 4.

Starboard wing section of Z2186. A piece of the landing gear can be seen down slope and the parking lot at Gwern Gof Uchaf on the A5 highway can be seen in the distance below. Llyn Ogwen is down slope and to the right in this photo.

Photo by Hywell Evans. 1981

The rescue team still had to carry the bodies of Pilot Officer Longworth and Sergeant Walker from the mountain top which they did. Pilot Officer Longworth was buried at Llanbeblig Public Cemetery in Caernarfon. He was 26 Years old and the son of Harvey and Hannah Longworth of Woodstock Ontario Canada. Sergeant Walker was buried at Letchworth Cemetery in Herefordshire. The son of Edward and Jinnie Walker of Letchworth, Ronald Walker was 22 years old.

F/Sgt Sims remained in hospital until May of 1943 but was still carried on strength with 418 Squadron. Sims returned to 418 Squadron for a short while but as the squadron was transitioning from Boston III aircraft to Mosquitos, Sims was sent to 60 OTU (Operational Training Unit) at High Ercall a few miles northeast of Shrewsbury Here he trained on Mosquitos. With his Mosquito training under his belt, Sims, now a WO1 once again returned to 418 Squadron, which had now moved to RAF Ford, and Sims once again became an Intruder. With his navigator, Pilot Officer (later Flying Officer) James David Sharples, the team accounted for 6 ½ enemy aircraft and 1 V-1. Sims and Sharples received the DFC effective September 1, 1944. It is significant also that Sims and Sharples would crew the first allied aircraft over France on D-Day.

Written by Cliff Adams

December 2020