Safety Mat­ters

Safety Mat­ters and Safety Briefs are based on the AAIB Bul­letin and UK Air­prox Board re­ports, with ad­di­tional ma­te­rial from the US Na­tional Trans­porta­tion Safety Board

Pilot - - CONTENTS -

Sad out­comes, avoid­able er­rors and the lat­est Air­prox sum­mary

Fa­tal power loss on take­off?

Air­craft Type: Europa Date & Time: 28 May 2017 at 1200 Com­man­der’s Fly­ing Ex­pe­ri­ence: LAPL, 1,146 hours, 880 on type Last 90 days: 7 hours Last 28 days: 1 hour The pi­lot was mak­ing his third flight in the air­craft that day. Wit­nesses saw it lift off from Coal As­ton’s Rwy 29, but it did not ap­pear to be climb­ing well, and as it passed them they heard the en­gine noise re­duce and ‘splut­ter’. The Europa then started a left turn at the end of the run­way be­fore de­scend­ing out of sight in a steep nose-down at­ti­tude, fol­lowed moments later by a ‘thud’. Wit­nesses south of the air­field who saw the air­craft fly­ing very low in a banked at­ti­tude heard the sound of a crash, im­me­di­ately alerted emer­gency ser­vices and ran to the ac­ci­dent site. The pi­lot had not sur­vived the im­pact.

Although the air­craft was se­verely dis­rupted, wing and tail sur­faces re­mained at­tached to the fuse­lage, which had crum­pled in the en­gine/cock­pit area, and the rear fuse­lage had de­tached. Fly­ing con­trols were in­tact and there was no ev­i­dence to sug­gest that they would not have op­er­ated nor­mally. The in­stru­ment panel was heav­ily frag­mented so it was not pos­si­ble to de­ter­mine pre-im­pact switch po­si­tions. The rpm gauge was stuck at 4,100 rpm and the fuel pres­sure gauge at 0.14bar, which is be­low the 0.15 - 0.40bar min­i­mum fuel pres­sure spec­i­fied by en­gine man­u­fac­turer Ro­tax.

The en­gine’s fuel fil­ter assem­bly was re­moved and its el­e­ment was in­spected. It was found contaminat­ed with gen­eral dirt and de­bris which in­cluded in­sect re­mains. Flow tests car­ried out us­ing the fil­ter el­e­ment fit­ted at the time of the ac­ci­dent and a new fil­ter both recorded fuel flows well in ex­cess of that re­quired by the en­gine at full power.

A sam­ple of the air­craft’s fuel was found to be con­sis­tent with fore­court un­leaded fuel to EN228 spec­i­fi­ca­tion and it con­tained 4.5% ethanol (E5 Mo­gas). His­tor­i­cally, suit­able Light Avi­a­tion As­so­ci­a­tion Per­mit air­craft such as this had been able to op­er­ate on un­leaded Mo­gas to EN228 stan­dard (fore­court un­leaded fuel), but around 2010 fuel com­pa­nies started to in­tro­duce ethanol [in re­sponse to an EU di­rec­tive] to pre­serve fos­sil fu­els. The usual choice is ethanol, cur­rently not ex­ceed­ing 5% by vol­ume, and the re­sul­tant fuel is des­ig­nated E5 Mo­gas.

Un­til late 2014 the CAA pro­hib­ited the use of Mo­gas con­tain­ing ethanol in sin­gle-en­gine pis­ton aero­planes, but then trans­ferred re­spon­si­bil­ity for choice of fuel and pro­vi­sion for ap­pro­pri­ate guid­ance to the air­craft’s type de­sign or­gan­i­sa­tion, in this case the LAA, whose tech­ni­cal guid­ance notes: ‘A vapour re­turn line must be fit­ted to cir­cu­late a small amount of sur­plus fuel, and any vapour back to the fuel tank’, while the man­u­fac­turer’s man­ual for the Ro­tax 912/912S en­gine, as fit­ted to this Europa, states: ‘The [vapour] re­turn line pre­vents mal­func­tions caused by the for­ma­tion of vapour lock.’

This ac­ci­dent air­craft/en­gine com­bi­na­tion can be ap­proved to use E5 Mo­gas and although it was fit­ted with the re­quired plac­ards, no log­book en­try or checklist could be found to show the re­quired pro­ce­dure to use E5 Mo­gas had been com­pleted or ver­i­fied by an LAA in­spec­tor. Anal­y­sis of the air­craft and en­gine log­books show that be­tween June 2006 and June 2011 there were a num­ber of re­ports of the en­gine ‘rough run­ning’, but af­ter rec­ti­fi­ca­tion work and re­place­ment of fuel and ig­ni­tion sys­tem parts no sub­se­quent re­ports were recorded, although the pi­lot’s per­sonal fly­ing log­book en­try for a flight made ten months be­fore the ac­ci­dent con­tained the an­no­ta­tion ‘Vapour lock – not nice’.

The AAIB re­port con­cludes: ‘The air­craft was seen to take off on the ac­ci­dent flight but it did not achieve a ‘nor­mal’ rate of climb. The en­gine power was re­duced although it was still pro­duc­ing power at im­pact. Ev­i­dence from the wreck­age and wit­nesses sug­gests it may have been op­er­at­ing at ap­prox­i­mately 4,000 rpm. This would rep­re­sent about 40% of take­off power, prob­a­bly suf­fi­cient to main­tain level flight or a small climb gra­di­ent, but any turn would di­min­ish this per­for­mance…

‘The air­craft was at an es­ti­mated height of 100-150ft when the left turn be­gan; start­ing to turn at such a low height sug­gests the pi­lot was aware of a prob­lem… The par­tial loss of power could have led the pi­lot to con­sider a turn­back, be­liev­ing he could main­tain height, but in the take­off phase as soon as any turn is started the as­so­ci­ated re­duc­tion in climb per­for­mance is likely to re­quire a de­scent to main­tain air­speed… The ground cues dur­ing the low level turn down­wind could have given the pi­lot an im­pres­sion of an in­creas­ing and higher than ac­tual air­speed, and thereby led to a stall. Any pre-stall in­di­ca­tions of buf­fet would have been very brief; a re­cov­ery from such a low height would not have been pos­si­ble…

‘There was one sig­nif­i­cant anom­aly re­lat­ing to the fuel sys­tem that may have been rel­e­vant to the ac­ci­dent. The fuel vapour re­turn line was con­nected to the in­let of the fuel se­lec­tor valve, rather than to the fuel tank. This would have the ef­fect of rout­ing any fuel vapour that formed in the fuel sys­tem back to the en­gine in­stead of re­turn­ing to the fuel tank to dis­si­pate… The air­craft was us­ing E5 Mo­gas, and although it was el­i­gi­ble to use this fuel, no ev­i­dence of the rel­e­vant pro­ce­dures to ap­prove its use could be found. The checklist that is com­pleted as part of this pro­ce­dure in­cludes an in­spec­tion to en­sure a fuel vapour re­turn line is in­stalled to route any vapours back to the fuel tank… [On this air­craft] it would have been re­turned to the en­gine, where it is likely it would dis­rupt its fuel sup­ply, re­duc­ing the power it was able to pro­duce.’

Height mis­judge­ment on land­ing

Air­craft Type: Van’s RV-7A Date & Time: 12 Au­gust 2017 at 1325 Com­man­der’s Fly­ing Ex­pe­ri­ence: LAPL, 88 hours, 43 on type Last 90 days: 23 hours Last 28 days: 8 hours This was the pi­lot’s third land­ing on grass, and his sec­ond on Sy­well’s Rwy 23 that day. Sur­face wind was 280º/14kt. The air­craft was po­si­tioned over the run­way cen­tre­line, but the pi­lot had dif­fi­culty judg­ing his height above it and landed heav­ily on the air­craft’s nose­wheel, which col­lapsed.

The pro­pel­ler struck the ground and the air­craft slid to a halt in a tail-high at­ti­tude, rest­ing on its lower en­gine cowl­ing.

The pi­lot com­mented that just be­fore touch­down he was not aware of any use­ful ground fea­tures in his field of vi­sion to help him to judge his height ac­cu­rately. The 30m wide run­way’s edge mark­ings are 3m x 1m chalked slabs, spaced 80m apart and slightly re­cessed into the ground, which he said were al­most in­vis­i­ble just be­fore touch­down and that the grass land­ing sur­face was too fea­ture­less to help him judge the air­craft’s height.

Sy­well’s op­er­a­tor said that the mark­ings on Rwy 23 ac­cord with the CAA’S ‘Li­cens­ing of Aero­dromes’ pub­li­ca­tion and had been re-chalked less than four months be­fore the ac­ci­dent. The AAIB says that it has re­ported on sev­eral pre­vi­ous ac­ci­dents in which the nose land­ing gear legs of Van’s Rv-se­ries air­craft have bent back or col­lapsed, many of them oc­cur­ring on grass run­ways. Its re­port also men­tions an ‘Anti Splat kit’ for RVS which is in­tended to re­duce nose gear res­o­nance and pre­vent the nose land­ing gear leg from tuck­ing un­der. The air­craft in­volved in this ac­ci­dent was so fit­ted.

Lat­est Air­prox re­ports

At its Oc­to­ber meet­ing the Air­prox Board re­viewed eigh­teen air­craft-toair­craft and six­teen air­craft-to-drone in­ci­dents. Seven of the air­craft-toair­craft in­ci­dents were as­sessed as Risk B: ‘safety much re­duced ei­ther due to serendip­ity, mis­judge­ment, in­ac­tion, or where emer­gency avoid­ing ac­tion was taken at the last minute’. Four of the in­ci­dents in­volv­ing drones were Risk A, seven Risk B, most in­volv­ing con­flicts be­tween drones and com­mer­cial air­lin­ers, but one con­cerned a Cessna 152 in­bound to Big­gin Hill. The pi­lot did not see it, but his non-pi­lot pas­sen­ger, who had been alerted to look out for other traf­fic, re­ported that it was “about the size of a foot­ball and passed ver­ti­cally level and about three light air­craft lengths hor­i­zon­tally” from the Cessna.

‘Be­cause we work about four months in ar­rears, it’s usual at this time of the year when as­sess­ing the sum­mer’s crop of in­ci­dents that late- and non-sight­ings ac­count for many Air­prox as folk got air­borne in large num­bers over the sum­mer with some­times rusty look­out,’ says the Board’s lat­est re­port. ‘Seven of this month’s in­ci­dents were at­trib­uted to this cause. That is not to crit­i­cise in­di­vid­u­als, the lim­i­ta­tions of the hu­man eye in the avi­a­tion en­vi­ron­ment are well doc­u­mented, as is the need to en­sure a ro­bust look­out and scan tech­nique as a

re­sult. It is sim­ply that when other pri­or­i­ties, pres­sures or tasks start to dis­tract us, dis­ci­pline is re­quired to over­come any lack of cur­rency and main­tain look­out as a key part of the “Avi­ate-nav­i­gate-com­mu­ni­cate” and “Look­out-at­ti­tude-in­stru­ments” mantras. Some­thing to think about when we all dust off our fly­ing gloves again next year.’

Note­wor­thy in the re­port is an Air­prox near RAF Lin­ton-on-ouse in­volv­ing two RAF Shorts Tu­cano tur­bo­prop train­ers and an au­t­o­gyro. ‘This in­ci­dent pri­mar­ily demon­strated how mis­un­der­stand­ing be­tween pi­lots and ATC can sud­denly snow­ball into a real is­sue,’ says the Board, ‘but the added un­cer­tainty as to the in­ten­tions of the au­t­o­gyro pi­lot as he flew near to the ap­proach path of RAF Lin­ton at 1,000ft cer­tainly ex­ac­er­bated the prob­lem for them.

‘ATC were try­ing to be help­ful by pass­ing in­for­ma­tion to the Tu­canos about a pri­mary-only radar track (i.e. they had no height in­for­ma­tion) as they made a radar-to-vis­ual re­cov­ery to Lin­ton. Un­for­tu­nately, the Tu­cano leader mis­in­ter­preted their call and ended up un­in­ten­tion­ally turn­ing to­wards the au­t­o­gyro he was try­ing to avoid. If the au­t­o­gyro pi­lot had called up Lin­ton ATC, then that would have re­moved all doubt as to his track, height and in­ten­tions, and there­fore en­abled ATC to pro­vide the Tu­canos, and per­haps him, with a bet­ter ser­vice.

‘There’s no re­quire­ment to make such a call of course, but if you can do so as you pass close to an air­field’s MATZ/ATZ then why not? Some­times pi­lots worry that ATC will then try to con­trol them, but they won’t: they might ask if you can help by al­ter­ing course or height slightly, but sim­ply of­fer­ing them in­for­ma­tion is not an in­vi­ta­tion for them to take over!’

To view the Board’s monthly re­ports in de­tail visit air­prox­board.org.uk

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