Aircraft Type: Van’s RV-8A Date & Time: 21 February 2018 at 1400 Commander’s Flying Experience: PPL, 4,310 hours, 37 on type Last 90 days: 6 hours Last 28 days: 6 hours The aircraft was being flown from the rear seat. Its owner, who held a PPL with a lapsed Single Engine Piston (SEP) rating, was a passenger in the front seat. Following a local flight from Old Sarum, the pilot made two ‘short field’ landings on the grass Rwy 06 with full flap set, and with braking applied by the passenger as brake pedals were fitted only in the front cockpit. A third approach was flown, for another short field landing, and the aircraft touched down on a part of the runway close to the threshold that felt bumpy and had an uphill gradient.
It then bounced and both occupants believed that only the mainwheels had touched, but subsequent examination of the ground markings indicated the nosewheel had also made firm contact. This was substantiated by a witness, who described the third landing as heavier than the first two, with the aircraft in a relatively flat attitude when it bounced. After the bounce, when the aircraft touched down again, the pilot asked the passenger to apply the brakes “more firmly” than he had during the previous landings. The aircraft ran straight and slowed quickly, but the nose dropped and, although the pilot moved the control column fully aft, its propeller struck the ground. According to the passenger, the aircraft then “flipped over quite slowly” and came to rest inverted, with its canopy broken into several pieces.
The pilot stated that the fuel and electrics were switched off immediately and then he released his seat belt, although he later wished he had kept his belt fastened for longer, because he had to support his own body weight and clear pieces of the canopy while he was upside down. In response to the pilot’s shouted instructions, bystanders raised one of the wings, allowing passenger and pilot to crawl out through the broken canopy.
The airfield operator noted that Rwy 06 is generally regarded as smooth but with an undulation or bump close to the threshold. At the time of the accident the surface had drained well after a period of rain, but was assessed as soft.
After examining the ground marks and damage, the passenger, who was also the aircraft’s builder and owner, noted that the nose undercarriage leg had bent rearwards as a result of digging into the soft ground during the landing, and there was significant damage to the nosewheel fork unit. The pilot stated that, prior to the aircraft inverting, there was no jolt and no noise was heard that could have warned him that the undercarriage was being damaged.
The pilot commented further that he ought to have flown the aircraft from the front seat, so that he had access to all the controls. He had previously held a flight instructor’s rating for SEP aircraft and, prior to this qualification lapsing, he had trained the passenger/owner on his aircraft, with the passenger/ owner occupying the front seat. Consequently, the pilot felt comfortable flying the aircraft from the rear and relying on the passenger/ owner to operate the wheel brakes when requested. The passenger/owner had logged forty hours flying in the RV-8A and was awaiting a proficiency check to renew his SEP rating. In retrospect, pilot and passenger/owner both agreed that it had not been appropriate to attempt short field landings on the uphill section of Rwy 06, where there is a surface undulation, especially in view of the soft condition of the grass surface.
The AAIB has investigated several UK accidents during which the nose leg of a Van’s RV series aircraft has bent back or collapsed and this is the sixth such accident which has resulted in the aircraft inverting. The Light Aircraft Association (LAA) Type Acceptance Data Sheet (TADS) for the Vans RV9A includes the following statement:
‘Problems have been experienced with the RV-9A nose leg, especially when operating off grass, with instances of the nosewheel bending back and the strut digging into the ground, causing a rapid stop and further damage. In order to avoid this risk, it is important to maintain the correct nosewheel tyre pressure, and to trim the spat to ensure generous clearance between the tyre and the wheel aperture in the spat (circa half an inch). It is also important to maintain suitable preload on the nosewheel axle bearings, torquing up the axle nut gently as required in the absence of a conventional spacer between the bearings. It is also important to land the aircraft on the mainwheels first and hold the nosewheel off the ground during the initial part of the landing roll, rather than landing on all three wheels together which encourages wheelbarrowing and overloading the nosewheel.’ A similar statement is included in the TADS for other Van’s types with nosewheels, but is not included in that for the RV-8A, so the LAA has now decided to review the RV-8A.
The US National Transportation Safety Board studied eighteen landing accidents and one incident to Van’s series aircraft that inverted during landing. The study’s summary stated: ‘Once the [nosewheel] strut and fork have contacted the ground, the strut will bend aft. The aft loading from the dragging fork and the spring-back reaction of the strut produces an overturning moment and lifting action that may result in the airplane overturning without any additional forces acting on the airplane. The aerodynamic load on the horizontal stabilizer may prevent the airplane from overturning while the airspeed is greater than some critical yet presumably low airspeed… At low airspeeds, the aerodynamic loads on the horizontal stabilizer lessen to the point that the tail can now start to rise allowing the airplane to rotate about the nose gear and become inverted.’ The study concluded that there was
sufficient strength in the nose undercarriage leg, and in all these cases the nosewheel forks made contact with the ground.
The LAA noted that occupants of this aircraft were helped in their escape because the aircraft’s canopy had broken, but in other accidents to Van’s types, pilots had had to use an axe or other tool in order to break the canopy and escape. The Association will now consider the case for requiring, or promoting, the carriage of an appropriate escape tool in certain aircraft types.
During its May meeting, the Airprox Board assessed 26 incidents, of which sixteen were aircraft-to-aircraft. Five had a definite risk of collision−two Category A where ‘providence played a major part’, and three Category B where ‘safety was much reduced due to serendipity, misjudgement, inaction, or late sighting’.
‘The dominant theme concerned nine cases of poor choice of airspace or poor integration with others, including a couple of instances where pilots flew over promulgated and active glider/microlight sites,’ says the Board. ‘Poor choice of airspace is an emotive topic, although all the cases involved pilots flying in airspace in which they were entitled to operate, but a little more thought for how their activities may have impacted on others might have avoided the conflicts. Poor communication in the air, or less-than-good liaison between neighbouring units, featured in six incidents; non/latesightings accounted for six others and inaction or flying too close to other aircraft was seen in five. Three incidents involved TCAS resolution advisory events caused by flight vectors impinging on the TCAS envelopes of larger aircraft.’ Of the six non/ late-sightings, three were linked to a lack of transponder transmissions from one or both aircraft which, if selected on, might have assisted ATC in providing traffic information, or allowed other collision warning-equipped aircraft to detect the other aircraft well before they came into proximity.
‘SERA 13001 came into force in UK in October 2017 mandating that, if fitted and serviceable, transponders must be switched on with all modes selected,’ says the Board. ‘A straw poll of GA Board members revealed that in their experience twothirds of pilots they either instructed or interacted with, including other instructors, did not know that transponder selection was now mandatory. Although this requirement was highlighted in Skywise by the CAA when it came into force, it seems that much of the GA community is still not aware of the change, hence an associated Board recommendation that the CAA consider further publication and education efforts about it.’
The Board also recommended that RAF Benson and local airfields engage in liaison to improve co-ordination of activities. This recommendation resulted from an incident in which the pilot of a CAP 231 was operating from White Waltham and flying aerobatics in one of its ‘aeros boxes’ that is about 10nm out on final to Benson’s Rwy 01. ‘Normally it’s not an issue with prevailing south-westerly winds,’ says the Board, ‘however on this day the easterly wind meant that the pilot [of a RAF Puma helicopter] was conducting a TACAN hold and approach to R01. ‘Although both pilots saw each other, it seems that neither really knew of the other’s operating intentions and so they ended up in proximity. Both pilots were entitled to operate where they did, but a bit more coordination would have eased the problem, especially if the CAP 231’s pilot had been able to make a call to Benson ATC to let them know his intentions.
‘The Regional Airspace User Working Groups (RAUWG) run by the military units are a brilliant way for pilots and clubs to engage with each other and the military to exchange information about such things as aeros boxes etc, so we highly recommend asking your local military ATC when they are holding the next one, and going along to participate (and also enjoy the usual free lunch that’s included!).’
The Board’s ‘Airprox of the Month’ involved the pilot of a Citabria who was departing from a private strip near Worcester, and trying to ensure a good lookout by lowering the aircraft’s nose regularly as he climbed, but nonetheless still didn’t see a Robinson R44 helicopter, which was probably a small stationary target in his peripheral field of view, approaching on the beam.
‘For his part,’ says the Board, ‘the R44’s pilot would have been looking down onto a dark background and didn’t see the Citabria climbing up until they were very close. Both saw each other at the last moment and had to take emergency evasive action. Neither aircraft was fitted with a collision warning system [although] both were using transponders [so it is] worth emphasising that the increasingly affordable systems now available could have helped… For the price of a couple of tanks of fuel, it would be well worth thinking about investing for just such eventualities when circumstances conspire to render see-and-avoid a fairly poor barrier to collisions−an alert in either aircraft here would have helped immensely in allowing at least one of the pilots to take earlier action.’
The full reports of these and other incidents can be found at airproxboard.org.uk in the ‘Airprox Reports and Analysis’ section, and they make instructive and thoughtprovoking reading
GASCO Safety Evenings
The General Aviation Safety Council (GASCO) is drawing up its programme of Safety Evening presentations for the 2018/19 season, which runs from 1 October 2018 to 30 April 2019. Flying clubs, schools, training organisations, groups or others who would like to host an evening (or afternoon) should telephone: 01634 200203 or email: [email protected] demon.co.uk
The RV-8A'S nosewheel dug into soft ground and its leg bent rearwards – similar to other RV landing incidents
The Citabria and R44 came within 2-4 seconds of collision