The Malone Column
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