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The Helicopter with Radioactive Blades

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Re: The Helicopter with Radioactive Blades

#41

Post by linksnapzz »

Heh...I actually knew about this.

A friend's cousin was a CH-53 pilot out of MCAS Miramar. One day, he was telling us, someone didn't properly secure one of the (chairs? racks? don't know the rotorcraft term...)in the cargo hold. The doors were open, and they were flying above the desert at a few thousand feet when...one of the aluminum & webbing chairs got sucked out the window and hit a rotor.

The number & intensity of the warning lights in the cockpit, and the accompanying alarms when that happens is pretty spectacular. The pilot knows right away.

Re: The Helicopter with Radioactive Blades

#42

Post by hansvm »

laxpri wrote: post #28
robocat wrote: post #10

Earlier quoted context omitted.

There's a good comment: MH-53E maintainer here. The system is IBIS (Inflight Blade Inspection System) and the little pods are BIM (blade inspection monitors). The box is pretty obvious sitting just behind the main rotor on the deck above the center engine. I found a random picture on the web: https://assets.verticalmag.com/wp-content/uploads/2017/01/MH... And: The IBIS devices provide in-flight warning of blade failu…

What does “inches” mean here

It's a medieval measurement, still in popular use. Nowadays it means approximately 2.54 centimeters. Historically, it's the height of the ash pile a "witch" would leave behind, and the word has morphed only slightly from "witches" into "inches."

Re: The Helicopter with Radioactive Blades

#43

Post by pixl97 »

DoctorOetker wrote: post #40
tomasphan wrote: post #7

Earlier quoted context omitted.

The titanium spar is filled with gas. If there was a crack in the spar the gas would escape, therefore tripping the pressure sensitive radiation shield. Releasing radiation that can be detected inside the helicopter. Wireless systems aren’t used for opsec reasons.

carrying a radiation source doesn't sound very opsec either to be honest...

Why? It's not like it's gamma radiation.

Re: The Helicopter with Radioactive Blades

#44

Post by Johnny555 »

DoctorOetker wrote: post #40
tomasphan wrote: post #7

Earlier quoted context omitted.

The titanium spar is filled with gas. If there was a crack in the spar the gas would escape, therefore tripping the pressure sensitive radiation shield. Releasing radiation that can be detected inside the helicopter. Wireless systems aren’t used for opsec reasons.

carrying a radiation source doesn't sound very opsec either to be honest...

Since the radiation source is only exposed if it's indicating a potential main rotor crack, and it's not a very strong radiation source in the first place (so it's not like it allows long distance tracking), it seems like a minor risk -- if the radioactive capsule is exposed, the pilot is going to be returning to safe place to land.

Beta particles typically only travel a few meters in air before they lose most of their energy.

Re: The Helicopter with Radioactive Blades

#45

Post by Johnny555 »

Neywiny wrote: post #26

> The solution is so elegant it’s still being used today. The newest versions of the CH-53 of fiber optics to detect faults in the newest all-composite blades. The older variants? They’re still going with the nuclear option. Huh? So it's not really in use today as much as hasn't been retrofit out. Those are very different. This also doesn't read well. Maybe rewritten without proofreading

If it hasn't been retrofitted out, then it's still in use today. That sentence would only be incorrect if the new solution was retrofitted on all aircraft.

Re: The Helicopter with Radioactive Blades

#46

Post by pixl97 »

xattt wrote: post #8
stackghost wrote: post #6

Earlier quoted context omitted.

Exposure to a nuclear blast doesn't necessarily make things radioactive. Hiroshima and Nagasaki are not radioactive wastelands. Even in Chernobyl, the other reactors continued to operate for a time after the accident, and nature is thriving. But, the radiation detector is on the upper surface of the rear fuselage. Hypothetical Beta particles from the ground will strike the underside of the aircraft and not the detect…

> Exposure to a nuclear blast doesn't necessarily make things radioactive Isn’t this neutron activation?

Generally they are going to airburst to cause maximum damage over an area which means what free neutrons hit are gasses which dispurse pretty quickly. Ground detonation does cause more fallout though.

Re: The Helicopter with Radioactive Blades

#47

Post by numpad0 »

laxpri wrote: post #28
robocat wrote: post #10

Earlier quoted context omitted.

There's a good comment: MH-53E maintainer here. The system is IBIS (Inflight Blade Inspection System) and the little pods are BIM (blade inspection monitors). The box is pretty obvious sitting just behind the main rotor on the deck above the center engine. I found a random picture on the web: https://assets.verticalmag.com/wp-content/uploads/2017/01/MH... And: The IBIS devices provide in-flight warning of blade failu…

What does “inches” mean here

Inches from the source. Inverse square law applies

Re: The Helicopter with Radioactive Blades

#48

Post by givc »

hansvm wrote: post #42
laxpri wrote: post #28

Earlier quoted context omitted.

What does “inches” mean here

It's a medieval measurement, still in popular use. Nowadays it means approximately 2.54 centimeters. Historically, it's the height of the ash pile a "witch" would leave behind, and the word has morphed only slightly from "witches" into "inches."

Actually nowadays it means exactly 2.54 cm as that’s how it is defined. Which also means all distance measured in US Customary units is ultimately metric too

Re: The Helicopter with Radioactive Blades

#49

Post by throwway120385 »

LorenPechtel wrote: post #27
throwway120385 wrote: post #14

Earlier quoted context omitted.

Strontium-90 is a beta emitter, apparently, so you could just measure Alpha, Beta, and Gamma and detect false positives due to elevated background radiation that way. If you're in the air you're probably much closer to your Beta source as well so you could detect it above background due to distance. Gamma is essentially light so it falls off with the square of distance. But Alpha and Beta are probably much worse than…

All nuclear things fall off much faster than square of the distance unless you're in vacuum. The atmosphere is nowhere near transparent to any of them. An addition to the inverse square issue the behavior of the various types is complex: Gamma: Halving distance in the low hundreds of meters. Alpha: Goes a few centimeters. Beta: Goes a few meters per million electron volts. Most sources don't go above a few million el…

Gamma is technically a kind of electromagnetic emission, so it falls off with the square of the distance. The others fall off as you say.

Re: The Helicopter with Radioactive Blades

#50

Post by mitxela »

throwway120385 wrote: post #49
LorenPechtel wrote: post #27

Earlier quoted context omitted.

All nuclear things fall off much faster than square of the distance unless you're in vacuum. The atmosphere is nowhere near transparent to any of them. An addition to the inverse square issue the behavior of the various types is complex: Gamma: Halving distance in the low hundreds of meters. Alpha: Goes a few centimeters. Beta: Goes a few meters per million electron volts. Most sources don't go above a few million el…

Gamma is technically a kind of electromagnetic emission, so it falls off with the square of the distance. The others fall off as you say.

Everything falls off as inverse square in 3D. His point is that the atmosphere attenuates it as well.
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