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Comment by buildsjets | Hacker News Reader

I'm really not a big "fan" of MT's cheezy wooden propellers. They call them "Natural Composite" but it's really just densified/compressed wood with a thin fiberglass wrapping. Here's an example of what you can expect from in-service damage, a Jetstream 41 recently hit a bird, shed a blade, and it shot right through the passenger cabin. The hilarious thing is that the government investigation called it a "survivable accident" because no one happened to be seated in the row that it shot through. https://avherald.com/h?article=4f2a35e6

I was involved in the evaluation of proposed repairs to a Beechcraft Bonanza with a 3 bladed MT prop that taxied into a vinyl traffic cone at idle speed. The Beech shed two prop blades, bent the engine mount and firewall. There was a slight cut in the traffic cone, but it was returned directly to revenue service.

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> The hilarious thing is that the government investigation called it a "survivable accident" because no one happened to be seated in the row that it shot through.

No, that’s not why. See FAA definition below.

Survivable Accident - an accident in which the cockpit and/or structure remains relatively intact and the forces experienced by the occupants did not exceed or should not have exceeded the survivable limits of human G-tolerance. Such an accident is classified as survivable even if some or all occupants were fatally injured. (NOTE: the investigator makes his or her greatest contribution to air safety by documenting the reasons why aircraft occupants were fatally or seriously injured in survivable accidents.)

https://www.faa.gov/documentlibrary/media/order/8020.11c_.pd...

Trust me, if that propeller had hit someone in the head, they would have experienced forces that would have exceeded the survivable limits of human G-tolerance.

> Such an accident is classified as survivable even if some or all occupants were fatally injured.

> occupants did not exceed or should not have exceeded the survivable limits of human G-tolerance

I think it was a joke.

In other words, a survivable accident is approximately an accident in which one or more occupants could have theoretically survived, even if in fact they all died. One or more survivors would seem to prove the accident was survivable.

Since in enough quantities or the lack thereof everything is lethal, where does the threshold land?

I'm sure some people have survived explosions, I know of the one woman who fell out of a plane without a parachute and survived it, so falling off the empire state building is a survivable incident, right?

They mention limits on acceleration, etc. I presume there's a standard table somewhere. I'm not sure if they use median survivablility or some higher quantile.

Are the wooden construction essential to the new blade design? What are the Beechcraft Bonanza props made of?

(As a complete layman, not even a pilot, I love the sound profile of the proposed props)

Normally, the prop on a Bonanza is made of aluminum. Based on observation of prior incidents, I would expect no or negligible damage to an aluminum propeller in the same circumstance. However, even if no external damage is seen, some engine manufacturers (and insurers) require a complete engine teardown and inspection in the event the propeller contacts an object while the engine is running.

I agree with what you're saying.

But to add a bit of colour to the incident: the Kori Bustard is the biggest flying bird in Africa, and it's mostly ground dwelling.

Seems like some bad luck was involved too, and I wonder if the same damage will occur with a smaller bird?

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