Steve Ayres summarises and comments on accident reports from around the world and looks at some rather nifty tyre pressure sensors which might just warn of an impending flat…
22 December 2020
While backtracking, the pilot of G-COLF noticed an area of undulating soft ground across Runway 08. After turning around at the threshold, he taxied forwards to position beyond the area before starting his take-off. While crossing the ground the aircraft became bogged down and the pilot applied increasingly more power to overcome the resistance. G-COLF’s power setting increased to such a level that bystanders thought it was starting its take-off run.
“Unlicensed airfields can have their own specific hazards, to which pilots need to be alert”
They then saw the nosewheel caster left before the aircraft veered off the runway and collided with G-BAFG on the adjacent grass parking area.
The pilot of G-COLF believed his aircraft may have become stuck in a rut on the runway, leading to the left wheel spat digging into the ground and causing the aircraft to pivot under power. The proximity of G-BAFG to the runway edge meant that the accident pilot had little time to react before the collision.
By their nature, unlicensed airfields can have their own specific hazards, to which pilots need to be alert. In this case, parked aircraft near the runway and high power, to avoid bogging down in undulating soft ground were catalysts for an accident.
Comment We’ve all been there – forgotten to remove the chocks, park brake left on or bogged down. In this instance it had to be the latter, especially as the bad ground had been spotted on the way out to the threshold.
But there’s only so much power that’s safe to add before stopping to think through the potential consequences of adding more… something will ultimately give way!
The pilot was visiting Compton Abbas Airfield and, having taxied out for departure, proceeded to line up on what he thought was the runway. However, he had actually lined up to the left of the runway. During the take-off roll, the aircraft pulled to the left, which was subsequently diagnosed as a binding left brake. This, combined with his starting position, meant he got close to a line of parked aircraft. The pilot described that he lined up to the right of what looked like two ‘black cones’.
The UK Aeronautical Publication (AIP)1 page on Compton Abbas details the runway markings which include black and white runway threshold markers positioned to the side of the runway threshold. The pilot of G-BPPF probably lined up between the marker board and the left side chalk line of the runway.
It’s the AIP that contains validated aviation data, but image tools such as Google Earth can be useful to pilots who are visiting places with which they may not be familiar. While they do not give detailed, up-to-date info, they can add a visual image of what to expect.
The pilot was flying G-CCFW, a Replica WAR FW190. The skies were clear with bright sunshine and light winds from the south-west. At around 1200, the pilot returned to the airstrip to land on its southerly runway. On landing, the aircraft had travelled a short distance when it ‘stopped violently’ and pitched over onto its back, trapping the pilot. The pilot was removed from the aircraft by emergency services and had suffered serious injuries. The aircraft was damaged extensively and deemed uneconomic to repair.
The aircraft had landed in crop to the left of the grass runway. He reported that he mistook the unmarked grass runway to be part of the crop in the adjacent field to the right of the runway owing to its similarity in colour. Instead, he made an approach to and landed in the field to the left of the runway, where tractor marks and the edge of the grass airstrip had created the appearance of a ‘false’ runway similar in size and shape.
The sun overhead may have reduced the contrast between the grass strip and the crops, contributing to the reduced conspicuity of the grass airstrip.
The pilot reported that the runway has since been marked out with white chalk lines.
Comment It’s that time of year again. Any markings on grass quickly get washed away or muddied, sun angles can be blindingly low, colour contrast between landing surfaces and their surrounds, poor.
Having only recently averted an off-strip touchdown myself by catching sight of much rougher terrain than expected beneath me, I know how easily it can happen. All it cost me was an additional landing fee although, as these events highlight, the outcome is sometimes extremely serious. And such occurrences are sadly not restricted to grass strips either, ‘take-off misalignment’ in poor visibility or at night occurs on paved surfaces with worrying frequency.
The pilot reported that he attempted to hand prop the engine numerous times without success. He returned to the cockpit and turned the magneto switch to the ‘off’ position and advanced the throttle to between ½ and ¾ travel.
He then exited the cockpit and turned the propeller backward five to six ‘blades’ to clear the cylinders. The pilot again returned to the cockpit and turned the magneto switch back to the ‘on’ position, but he did not retard the throttle back to idle. He attempted to hand prop the engine again, and it started.
Due to the engine’s throttle setting, the aircraft moved forward over the wheel chocks and struck the pilot, resulting in serious injuries, and then a hangar, which resulted in substantial damage to the firewall and fuselage.
Comment Hand-swinging props has never been a favourite pastime of mine having grown up on a diet of horror stories, with this type of accident featuring prominently, of course. Getting the technique wrong is pretty unforgiving and any sense of complacency must be banished. In the end, it comes down to check the settings and then check again… and again!
The pilot reported that he intended to fly to a nearby airfield and that when he departed the cloud base was obscuring the high ground. He also stated that as a result of the low cloud he became disorientated and lost. Moreover, his engine started to run roughly, and he ‘anticipated’ that he might need to carry out a forced landing. However, the engine continued running and he returned to the airfield and landed.
“The aircraft pivoted to the left and came to a stop wedged against the telehandler”
While taxying back to the hangar, the left wing struck a stationary telehandler parked alongside the taxiway. The aircraft pivoted to the left and came to a stop wedged against the telehandler. The impact dented the left wing leading edge near the wingtip, displaced the wing and distorted the flap. The propeller was severely damaged, and the lower engine cowl was dented. The pilot and a construction worker, who was standing close to the telehandler at the time, were uninjured. The lime green coloured telehandler was parked perpendicular to the tarmac taxiway, at the edge of an area of hard ground, in front of a newly constructed low hangar. A taxiway widening strip, referred to as a ‘ditch’, ran alongside the taxiway on the opposite side to where the telehandler was parked.
The ditch had a smooth unfinished surface which had been added to widen the taxiway to allow glider wings to pass the building site. It was about 100mm lower than the taxiway surface and had chamfered edges. Just prior to the collision, the aircraft was being taxied towards the left side of the telehandler putting the ditch on the right side of the aircraft.
The pilot described how he allowed the right main wheel to run into the ditch to make room to pass the telehandler. In his opinion, it was the wheel running in the ditch that caused the aircraft to swing around to the left and into the telehandler.
Individuals who responded to the collision commented that there was a dent on the left leading edge consistent with the outer section of the left wing contacting the telehandler, causing the aircraft to swing to the left and hit the main body of the vehicle.
Comment The precise details of how a bright green telehandler came to be struck are slightly confusing, but that can perhaps be forgiven, taking into account the pilot’s probable emotional state. Having just been forced to turn back on a flight due to bad weather, which caused them to become disorientated and lost, then surviving the threat of an engine failure and potential forced landing, one can only imagine how they must have been feeling. But any euphoria of having got back safely vanished as they faced the telehandler. A useful reminder that the trip isn’t over until the aircraft is signed back in or the hangar doors locked.
Don’t want to be let down by low tyre pressures this winter? Why not simply replace your tyre valve caps with this clever and discreet Aviation Tyre Pressure Monitoring System (ATPMS). Derived from systems used widely on bicycles and motorcycles these Bluetooth connected devices will give you real time tyre pressures even when airborne. Just check that your mobile phone or smartwatch is able to connect with the wheel sensors in flight or simply use them when checking tyre pressures and temperatures on your walk round. With ATPMS, you will get an alert as soon as the tyre pressure drops below a certain pre-set level as long as your personal device is within the Bluetooth range (-30m) and the App is running. Batteries on these sensors last for around a year so should keep you connected through to your next annual and, who knows, they may just save the cost of a major airframe repair. We’re testing some, so will report back in the next issue.
