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View of downtown San Francisco from a helicopter cockpit

The National Transportation Safety Board (NTSB) has just released its Preliminary Report (PR) on yet another Robinson Helicopter fatal crash, this one involving a Model R66 which took the lives of two citizens of Buffalo, New York, Pilot Mark D. Croce and passenger Michael Capriotto.  Tragically, according to the NTSB, this was yet another in-flight breakup, the cause of which remains undetermined.

The Robinson Helicopter line, consisting of the original, two-seat introductory R-22, the four seat R-44, both piston-powered, and the R-66, a four-seat turbine-powered version, have a history of fatal and non-fatal accidents.  Depending upon which aviation expert you talk to or how accident rates are spun, its accident history is attributed to Robinsons being terribly deadly machines often operated by inexperienced/risky pilots—or some combination of faulty machine and pilot.

Aviation attorney Joseph Anderson, who has represented victims of several of these fatal crashes, lists four major problem areas with all versions of the Robinson helicopters (1) mast bumping, where the aircraft’s teetering (see-saw) rotor system contacts the mast causing rotor system separation, (2) delamination of the rotor blades where the blades actually come apart, (3) aluminum fuel tanks which split open on impact causing post-crash fires, and (4) low inertia rotor system which allows for rapid loss of rotor rpm during powered-off situations.  “Because the aircraft are all similar dynamically and structurally with the same rotor systems and, until recently, fuel tanks, they all pose the same risks to their pilots and passengers,” Anderson states.

Anderson’s opinions are supported by numerous news stories, none more thorough than Danger Spins From the Sky, a November 2018 article by Los Angeles Times reporters Kim Christensen and Ben Welsh/.

The article is well-researched, has helpful graphics, and is worth a read. Its staggering premise: the Robinson R44, the world’s best-selling civilian helicopter, has been involved in more than 42 fatal crashes in the U.S. from 2006-2016, more than any other civilian helicopter, which translates into 1.6 deadly accidents per 100,00 hours flown, a rate nearly 50% higher than the other common civilian helicopters tracked by the Federal Aviation Administration (FAA).

Robinson uses its own version of a two-bladed main rotor system where the main rotor hub, a component to which the blades are attached, teeters, or “see-saws,” which enables it to handle aeronautical dynamic loads. This is a somewhat antiquated “semi-rigid” system but has been used most widely by Bell Helicopter on its UH-1 “Hueys,” its Bell 206 OH-58 “Jetrangers,” and its earlier AH-1 “Cobras.” More modern helicopters, such as Airbus and Sikorsky, and now even Bell, utilize a “fully articulated rotor system,” where, instead of “teetering” to absorb loads, the rotor blades are allowed to “lead” and “lag” on a hinge where the blade attaches to the hub.

The gravest hazard associated with teetering rotor systems is mast-bumping, where the heavy main rotor hub leaves its normal plane of rotation and actually smashes into the mast, causing the mast to break and the rotor system to depart the helicopter, which means the helicopter is now an aircraft without wings.  This can occur during drastic maneuvers or during turbulence or if the pilot reacts less than correctly to an in-flight emergency such as an engine failure. It can happen almost instantaneously–before the pilot can react.

The Bell products were notorious for this phenomenon during combat operations in Viet Nam which often necessitated radical maneuvering to avoid enemy fire.  In fact, a reporter for the Fort Worth Star Telegram, Mark Thompson, won a Pulitzer Prize for his series on this phenomenon

In the 1980’s, I handled a mast-bumping case which occurred at the U.S. Navy Test Pilot School which cost the life of one of the two aviators on board. The other pilot escaped.  At the time, it was the only known accident in which someone survived an in-flight rotor separation due to mast bumping–only because the test protocol required the wearing of parachutes.

But the fatality in the Pax River AH-1 crash was consistent with what can occur in Robinson mast bumping events.  The rotor system leaves the aircraft, which means the aircraft is no longer capable of flight, but as it does so, it often slashes through the cockpit with obvious fatal results.  The FAA finally responded to this problem as it usually does—not by correcting the equipment issue but by focusing on the pilot, issuing Special Flight Regulation 73, which required extra instruction for Robinson pilots. With The Robinson R-44’s Safety Issues, The FAA Has Taken a More Hands-Off Approach, Kim Christensen, LA Times, November 18, 2018.

The low-inertia rotor system causes another hazard for the pilot.  Unless he or she responds instantly to an engine failure by getting the collective down to preserve rotor rpm, rotor blade rpm can quickly deteriorate to a hazardous rate, adversely affecting the pilot’s ability to “autorotate” the helicopter to safe landing.  In most helicopters there are ways to restore rotor rpm by maneuvering, but in Robinson helicopters, once the rotor rpm goes below 75%, the pilot might not get it back (Robinson R22: The Good, The Bad and the Ugly, Neal Lanning, AOPA Magazine, July 15, 2014), meaning the aircraft can no longer fly.  “Imagine that the wings would come off of a single engine airplane if the pilot didn’t respond immediately to an engine failure—that’s what we have here,” says aviation attorney Joseph Anderson.

The delamination of the rotor blades caused several accidents and was initially addressed when in 2007 the FAA required Robinson operators to perform a crude test—tapping the blade with a quarter. But in December 2014, after a dozen blade failures world-wide, the FAA determined that de-bonding had continued to occur and ordered the replacement of main rotor blades on over 2500 R-22’s and R-44’s–at a cost to owners of more than $122 million.

The aluminum fuel cell fire hazard occurred when the cells split open during otherwise non-fatal crashes causing a post-crash fire with often fatal results.  One commentator glibly noted: “…it’s worth remembering that the fuel tanks didn’t cause any of these accident—they caused them to become fatal.” (What’s Wrong With Robinson R44 Pilots? John Zimmerman, John’s Blog, January 14, 2019). This non-sensical observation ignores the fact that Robinson has, at least partially, recognized the hazard and taken moderate steps to fix it.  In 2006, Robinson addressed the matter not by fortifying the tanks but by recommending that flight crews wear fire-retardant Nomex flight suits—almost unheard of in the civilian helicopter industry and a clear admission that the aircraft was a fire hazard. 

Thankfully, this was followed in 2009 by the company equipping its R44 tanks with puncture-resistant flexible bladders designed to not rupture in low-impact crashes.  Robinson also offered them as a retrofit to helicopters already in service at $6,800 plus labor.  Robinson claimed the delay was due to the time it took develop these bladders, apparently unaware that the U.S. Army had been utilizing such technology in its helicopter fleet since the 1970’s. 

There are many who say there is nothing wrong with the Robinson design. They argue that the accidents are the are due to the novices that operate the helicopters (see articles cited herein)—in some ways the very customer base that Frank Robinson intended to serve when he started his company in 1973. The House That Frank Built, Robert W. Moorman, Vertiflight, May/June 2013

But it is precisely because of its intended customer base that Robinson helicopters should be designed to be forgiving, non-hazardous flying machines.  When a problem has a solution, wisdom and safety demand that the solution be applied, even where government agencies don’t demand it. When it’s broke, fix it, especially when lives are at stake.  

One Comment

  1. Gravatar for Terry Comins
    Terry Comins

    Hello

    I started my flying career with a R22 serial number 23 in NZ

    That machine went on to become the very first Robinson in deer hunting and live capture

    I believe very capable flown inside the flute envelope

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