The Malone Col­umn

Pilot - - CONTENTS - Pat­malone

The Cabri is a good air­craft... with a rot­ten ac­ci­dent record

Ask­ing ques­tions is in­ter­preted as cast­ing as­per­sions on the type

At a he­li­copter event in March I was cor­nered by an old friend, Roy Har­ford, who ac­cused me of con­duct­ing a “petty ven­detta” against the Guim­bal Cabri−a base­less al­le­ga­tion, I told him, as I have never writ­ten a neg­a­tive word about the he­li­copter. Roy, who owns the first pri­vate Cabri to be brought into Bri­tain and is an in­de­fati­ga­ble booster of the type, is an­gry that I have a habit of ask­ing Cabri pi­lots how they were taught to han­dle the he­li­copter’s anti-torque sys­tem, and how well they un­der­stand the char­ac­ter­is­tics of the fen­e­stron. My ques­tions stem from an in­ter­est in avi­a­tion safety, but ask­ing ques­tions is sometimes in­ter­preted as cast­ing as­per­sions on the type. If I thought there was some­thing to be dis­cussed about the Cabri, Roy asked, why did I not write about it in Pi­lot? So I agreed to do so.

Guim­bal has sold some 250 Cabris world­wide, of which thirty have crashed. That’s a very high per­cent­age, and I think it’s sig­nif­i­cant that a large num­ber of Cabri crashes are car­bon-copies of each other. The most re­cent, at the end of Jan­uary, was F-HRCR, which crashed near Aix-enProvence. Wit­nesses said it was com­ing to the hover when yaw con­trol was lost and it be­gan to spin. The crash se­ri­ously in­jured the pi­lot, in­jured the pas­sen­ger to a lesser de­gree and wrote off the he­li­copter.

The first Cabri to come into Bri­tain, G-UIMB, crashed at Kem­ble in 2011 when it was com­ing to the hover and be­gan to spin. The AAIB re­ported that fuel-slosh­ing from the ro­ta­tion starved the en­gine, and the he­li­copter crashed. In­juries to the two pi­lots were not se­ri­ous and the he­li­copter was re­pairable.

Be­tween 2010 and 2019 there were many sim­i­lar ac­ci­dents. D-HETA was be­ing flown by an in­struc­tor and ex­am­iner with 4,500 hours (al­though only 35 hours on fen­e­stron types like the Cabri) when it be­gan to spin and crashed in Karl­sruhe, Ger­many in 2010. VH-ZZT crashed in 2012 when an in­struc­tor ‘as­sessed the rate of de­scent to be too fast and at­tempted to abort the ma­noeu­vre by in­creas­ing col­lec­tive, ap­ply­ing full throt­tle to in­crease the ro­tor RPM and full right pedal to coun­ter­act the in­creas­ing left yaw rate’. The he­li­copter yawed through

sev­eral ro­ta­tions: the in­struc­tor was un­able to re­cover the ro­tor RPM, nor ar­rest the left yaw or roll that de­vel­oped, and the he­li­copter hit the ground.

In the same year, also in Aus­tralia, an ac­ci­dent to VH-CDU was as­cribed to an un­con­trolled yaw which could not be coun­tered by the in­struc­tor. ZK-HCS crashed in New Zealand in 2013 while prac­tic­ing pedal jams: it was said that the nose yawed and got away from the stu­dent. The he­li­copter ro­tated twice, dur­ing which time the en­gine went si­lent. The in­struc­tor took con­trol but the tail struck ground and the he­li­copter rolled over.

In Ger­many in 2014, D-HAIG was said to be try­ing to hover into a take­off po­si­tion but started to spin around and crashed. F-HOLA crashed dur­ing a prac­tice go-around in 2015 when it sud­denly made ‘sev­eral turns around the yaw axis’ and landed heav­ily. In 2016, N503DS was hover-taxy­ing with a tail wind in Beau­mont, Texas, when the pi­lot ‘lost fen­e­stron ef­fec­tive­ness’. The he­li­copter spun three times and hit the ground.

In the crash of N989HH in St Louis in 2018, ac­cord­ing to the in­struc­tor the stu­dent ‘did not ap­ply suf­fi­cient right pedal’ on com­ing to the hover and the he­li­copter rapidly yawed. The in­struc­tor took con­trol but the he­li­copter rolled over. OK-BRI crashed in Slo­vakia in 2018 when the in­struc­tor failed to stop the ‘spon­ta­neous ro­ta­tion’ of the he­li­copter on take­off and it hit a fence. The crash of C-GELP in Canada in 2018 hap­pened when ro­tor RPM was al­lowed to de­cay in au­toro­ta­tion, fen­e­stron ef­fi­ciency was lost and the he­li­copter rolled over.

In sev­eral other ac­ci­dents, im­per­fect yaw con­trol seems to have been a fac­tor−hence my in­ter­est in how yaw con­trol is be­ing taught. The Cabri is a good he­li­copter and I re­viewed it pos­i­tively in Pi­lot when it first came to Bri­tain: the only is­sues I high­lighted, like main ro­tor vi­bra­tion at speed, were al­ready in the process of be­ing ad­dressed. But a fen­e­stron is not a con­ven­tional tail ro­tor and can­not be treated like one, and my ques­tion­ing leads me to think not all Cabri pi­lots are fully au fait with the dif­fer­ences.

Fen­e­stron thrust in­crease is not lin­ear, but flat­tens out in the mid­dle sec­tion of pedal travel. The beefi­est thrust is ob­tained with the last ten per­cent of pedal, so in case of un­com­manded left yaw you really have to get your right foot to the floor and keep it there−and if you can avoid it, don’t move the col­lec­tive! In 2005 Euro­copter is­sued a ser­vice letter warn­ing pi­lots against rais­ing the lever in cases of un­com­manded yaw, as the in­creased torque would ex­ac­er­bate the fuse­lage ro­ta­tion. And de­creas­ing col­lec­tive, it said, would cause the he­li­copter to tilt and hit the ground.

The Cabri ac­ci­dents men­tioned here oc­curred at low-en­ergy stages of flight and there have been no deaths−the only peo­ple killed in a Cabri were struck by an­other air­craft, and pi­lots and he­li­copter were blame­less. Per­haps this ex­plains an ap­par­ent lack of ur­gency. I think Guim­bal should take a leaf out of Robin­son’s book. When the R22 was cer­ti­fied forty years ago it cre­ated a new mar­ket where in­struc­tors of­ten had lit­tle more ex­pe­ri­ence than their stu­dents, and the ac­ci­dent rate was hor­ren­dous. The fac­tory’s Safety Course brought the sit­u­a­tion un­der con­trol, teach­ing peo­ple how the he­li­copter should really be han­dled. No re­design has been done−ed­u­ca­tion was the key. To­day the R22’s safety record is bet­ter than GA fixed-wings.

Guim­bal has al­tered a few things on the he­li­copter−warn­ing lights and so forth−but pi­lots keep hav­ing the same ac­ci­dent. The fact that I ask ques­tions that some would pre­fer not to be asked means my name is tra­duced in cer­tain cir­cles: I am ac­cused of be­ing a Robin­son stooge, and worse. I hold no brief for Robin­son−i have nine­teen types in my log book and they all have their good and bad points. Per­sonal vil­i­fi­ca­tion has no place in avi­a­tion safety, but I’m pretty thick­skinned, and I think aware­ness is a vi­tal weapon against mishap. So if you’re a Cabri pi­lot and I meet you, I may have the temer­ity to ask you a few things.

Pat has worked as a jour­nal­ist on three con­ti­nents and is a fixed-wing pi­lot and for­mer he­li­copter in­struc­tor with 1,500 hours TT

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