Philip Greenspun’s Weblog

“Danger spins from the sky: The Robinson R44, the world’s best-selling civilian helicopter, has a long history of deadly crashes” (LA Times):

It is the world’s best-selling civilian helicopter, a top choice among flight schools, sightseeing companies, police departments and recreational pilots.

It also is exceptionally deadly.

Robinson R44s were involved in 42 fatal crashes in the U.S. from 2006 to 2016, more than any other civilian helicopter, according to a Times analysis of National Transportation Safety Board accident reports.

That translates to 1.6 deadly accidents per 100,000 hours flown — a rate nearly 50% higher than any other of the dozen most common civilian models whose flight hours are tracked by the Federal Aviation Administration.

Robinson points out that the flight hours reported to the FAA are likely undercounted (e.g., if an owner/operator gets sick of onerous annual surveys and tosses them into recycling… not that I know of anyone that irresponsible…)

I’m not surprised that an owner-flown $400,000 R44 is twice as likely to be involved in a fatal accident than a professionally-flown $3 million Airbus AStar.

Having been an instructor in the Robinson R22, however, I’m shocked that the fatal accident rate for this $200,000-ish (rebuilt) flight school mule is comparable to that of a $3+ million Bell 407 (i.e., less than half the rate for the much-more-forgiving R44). I guess this shows the advantage of being in the training environment, in which encountering bad weather is much less likely than when an aircraft is used for transportation. Alternatively, you could say that this shows the safety advantage of a two-pilot crew. A higher percentage of R22 hours are student and instructor rather than a single pilot. (The Schweizer 269‘s accident rate is even lower; this is a machine that is essentially exclusively used for training.)

Here’s a cited accident that would have been much less likely to occur with two pilots on board:

Take the case of Jim Bechler, an Orange County attorney who had piloted Robinson helicopters for more than 30 years and bought a new R44 in 2008. He was flying home from a business meeting near Temecula when he stopped to refuel at Corona Municipal Airport.

Minutes later, as the helicopter lifted off with 40 gallons of fuel in its tanks, its rotor blades clipped a metal canopy over the fuel island. The R44 flailed briefly, dropped a few feet to the pavement and burst into flames.

(This also shows the tragic backwardness of certified human-occupied aircraft compared to $500 drones. A consumer drone wouldn’t fly itself into an obstacle as described above.)

Given the numbers, the LA Times could have cast the story as “local company makes an inexpensive helicopter that is remarkably safe when flown by two pilots”. The story’s focus on mast bumping does not make sense. The statistics in the article show that the Bell 206, which has a two-bladed rotor system subject to mast bumping, has a lower rate of fatal accidents than the Bell 407, whose 4-bladed rotor system isn’t at risk.

Personally I would like to see robot copilots for both helicopters and airplanes.

“What the Lion Air Pilots May Have Needed to Do to Avoid a Crash” (nytimes) contains a lot of good cockpit photos and illustrations explaining the combination of manual and automatic flight controls that likely played a role in the recent Boeing 787 MAX 8 crash (see https://philip.greenspun.com/blog/2018/11/11/boeing-737-crash-is-first-mass-killing-by-software/ ).

If it sensed a stall, the system would have automatically pushed up the forward edge of the stabilizers, the larger of the horizontal surfaces on the plane’s tail section, in order to put downward pressure on the nose.

To counter the nose-down movement, the pilot’s natural reaction would probably have been to use his yoke, which moves the other, smaller surfaces on the plane’s tail, the elevators. But trying that maneuver might well have wasted precious time without solving the problem because the downward force on the nose exerted by the stabilizer is greater than the opposite force the pilot would be trying to exert through the elevator, said Pat Anderson, a professor of aerospace engineering at Embry Riddle.

“After a period of time, the elevator is going to lose, and the stabilizer is going to win,” he said.

(The same guy gave an interesting lecture this summer; see “Transitioning to electric flight (lectures at Oshkosh)”.)

The pictures show a mix of 1950s (the big trim wheel), 1980s (the switch-controlled trim and trim interrupt), and 1990s (the MCAS layered on top that puts in heavy trim silently).

My comment on the NYT piece:

I sometimes fly the Pilatus PC-12, a simple 11-seat turboprop. Its stall-protection system was designed in the early 1990s. There are two angle-of-attack (AOA) sensors, one on each wing. There are two computers, each one of which is connected to a single AOA sensor. Only if both AOA sensors show a stalling angle of attack (“nose too high”) AND both computers agree THEN there will be a “stick push”. Thus there could never be a nose-down push due to a single bad AOA sensor. In the unlikely event that both sensors and/or computers went haywire at the same time, there is a “pusher interrupt” switch right on the yoke (“stick”). So the pilot need not hunt for an out-of-sight and never-previously-used switch.

It sounds as though Boeing engineered something that relies on just one sensor.

Plainly the Pilatus-style system would not have interfered with these 189 souls making their way safely to the destination. I wonder if a simple voice annunicator on top of the Boeing system would have also saved the passengers and crew. If it had said “trimming down, trimming down” into the headsets, the pilots would have known to direct their attention to the trim and trim interrupt switches.

“7 Women Accuse Dartmouth Professors of Sexual Abuse in Lawsuit” (nytimes):

Seven women are suing Dartmouth College for sexual assault, harassment and discrimination they say they experienced from three prominent professors who, according to the suit, turned a human behavior research department “into a 21st-century Animal House.”

For over a decade, the professors — Todd Heatherton, William Kelley and Paul Whalen — “leered at, groped, sexted, intoxicated and even raped female students,” according to the court papers, which were filed Thursday in federal court in New Hampshire.

The lawsuit, which seeks $70 million in damages…

There are approximately 4,300 undergraduates at Dartmouth. In-state tuition at University of New Hampshire is $18,500 per year (source). At rack rates, therefore, 4,300 students would pay $79.5 million at UNH. Assuming only a modest amount of financial aid, then, it would cost less to send all 4,300 of these undergrads to UNH than the amount of damages that was inflicted on these seven women.