Robinson R22/44 Tail losses

[runway16]

TV news tonight shows a R22 helo with no tail feathers crashing. fatal to two.

Australia has had two like accidents, if I got it right, but as yet no comment from the accident people ATSB, the FAA or Robinson re this. Could the lose of tail feathers be related?

The Australian ATSB people are asking for input from pilots and maintainers asking for any information re tail boom issues. That came after the first one, a fatal.

There has been a second one in Australia but no mention if it was the same type of event, lose of the tail boom in the air.

[DaveReidUK]

Robinsons, when sufficiently mishandled, are prone to chopping their tails off with the main rotor. Nothing new there.

[Piper.Classique]

How do you do that, Dave? Negative G?

[First_Principal]

I'm not a fling-wing pilot, however this report may give an insight into how a tail-boom issue occurred with at least one 22:

https://www.taic.org.nz/sites/default/files/inquiry/documents/11-003%20Final.pdf

Aside from that there does seem to be a Robby 'mast bumping' problem that's been around for some years and is presently under general investigation:

https://www.taic.org.nz/watchlist/robinson-helicopters-mast-bumping-accidents-nz

[Teddy Robinson]

Another one here, two fatalities 25th March 2022


Kathryn's Report: Robinson R44 Cadet, N514CD: Fatal accident occurred March 25, 2022 in Rowlett, Dallas County, Texas (http://www.kathrynsreport.com/2022/03/robinson-r44-cadet-n514cd-fatal.html)

[henra]

I'm not a fling-wing pilot, however this report may give an insight into how a tail-boom issue occurred with at least one 22:
https://www.taic.org.nz/sites/default/files/inquiry/documents/11-003%20Final.pdf

Ok, but that one was hair- raising. In an R22 with two persons high up in steep Mountains in 30 - 40 kts winds. Russian Roulette would appear safe in comparison.

[punkalouver]

How do you do that, Dave? Negative G?

I believe there have been various articles about this over the years on the exact reason, which obviously does have to do with helicopter aerodynamics. I seem to remember reading that a fixed wing pilot whose instincts have been created for that kind of flying can be vulnerable to unintentionally using those instincts in an R22 with fatal results(but not necessarily applicable to other types of helicopters). If true, something to think about if deciding to make a transition to learning to fly the R22. It can take a long time, if ever, to truly overcome instinctive reaction. Meaning that you may want to choose another type to fly.

[megan]

The R-22 and 44 have what is called a teetering rotor head, any aircraft with such a design is subject to mast bumping, which if severe enough will cause the rotor to separate. The issue first came to prominence with the Huey series of helicopters where the US Army lost a number and so embarked on an education program. My unit lost one with its four crew and ten soldiers in Vietnam, the usual precipitating cause was a zoom climb followed by reduced "g" on the push over at the top of climb, but that's not the only manner in which to induce the problem. The following twenty minute US Army training video should enlighten as to the ins and outs of the phenomena.

https://www.youtube.com/watch?v=_QkOpH2e6tM

[punkalouver]

A separate issue for the R22 to think about(copied from the web)....

"Due to its light weight and low inertia rotor system, the R22 is not forgiving of pilot error or sluggishness. After an engine failure, real or simulated, you and the instructor will have 1.6 seconds to lower the collective and enter an autorotation. Any delay beyond 1.6 seconds will be fatal as the rotor speed, once decayed below 80 percent, cannot be recovered. Frank Robinson did not design the R22 to be a trainer; he designed the R22 for a fast cruise speed and fuel efficiency. The R22 thus has a fast cruise speed, high fuel efficiency, and is a terrible trainer. Why do so many flight schools use the R22 for training? It is cheap to operate.If you are looking for a trainer, consider the Robinson R44 (https://philip.greenspun.com/flying/robinson-r44) instead. The R44 has about 4 seconds of rotor inertia rather than 1.6. That gives a pilot time to hear the low rotor RPM warning horn, look at the gauges, come up with a plan, and implement the plan (i.e., lower the collective and enter the autorotation). Count out 4 seconds to yourself and then count out 1.6."

Robinson R22 (with some comparisons to the R44) (greenspun.com) (https://philip.greenspun.com/flying/robinson-r22)

[punkalouver]

In addition from the NZ accident investigation board......

"The Transport Accident Investigation Commission is concerned about the number of accidents in New Zealand in which Robinson helicopters have experienced ‘mast bumping’. These accidents have raised concerns about the risks of flying these helicopters in the mountainous terrain and weather conditions that are common in New Zealand.

Mast bumping is contact between an inner part of a main rotor blade or a rotor hub and the main rotor drive shaft (or ‘mast’). Serious mast bumping in flight usually results in the helicopter breaking up in flight, which is fatal for those on board.

Part of the problem is that the available evidence has not allowed the circumstances and causes of all of these ‘mast bumping’ accidents to be fully determined. However, a significant proportion have been found to have occurred in ‘low-G’* flight conditions. Helicopters with semi-rigid two-bladed main rotor systems, as used on Robinson helicopters, are particularly susceptible to mast bumping in ‘low-G’ conditions. Low-G can be caused by large or abrupt flight control inputs or by turbulence. The risk of mast bumping in turbulence increases with high power settings and operating at high speed and light weight."



" It is particularly important for Robinson pilots to be aware of the risks of flying a lightly loaded helicopter at high speed in turbulence. "