Van’s over­turned

Pilot - - Safety Matters -

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.

Air­prox re­ports

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

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