What are the flight deck effects when in a radioactive cloud?

[Hardy Heinlin]

Good morning,

I'm asking because one of the weather phenomena coded in the SIGMET system is "RDOACT CLD", i.e. "radioactive cloud".

The biological effect is obvious. But what may happen in the digital and analog avionics?

Of course, radioactive zones should be avoided, and probably nobody ever flew within such zone, so nobody knows.

Are there any historic SIGMETs on this subject?


Regards,

|-|ardy

[Markus Vitzethum]

Hi Hardy,

quick relpy with "gut instinct" ("Bauchgefühl"). I'm rather specialized on automotive electronics but as far as I know aerospace electronics has a requirement to be radiation-hardened due to the presence of cosmic radiation (interstellar gamma radiation, high energy neutrons, secondary radiation [cosmics ray, e.g. pions]).

e.g. quick Google results
https://www.sciencedirect.com/science/article/pii/S0141933198001069 (I need to read that one... )
http://www.solarstorms.org/SEUavionics.pdf

I don't expect an immediate dominant effect from any radioactive cloud. If the effect would be dominant e.g. larger than the amount of cosmic radiation the electronics is qualified for, I would expect a much bigger effect on the flight crew anyway.

Markus

[Hardy Heinlin]

Hi Markus,

I'm thinking of catastrophes like Chernobyl or Fukushima. I learnt, for example, that photographers and filmers were unable to take pictures there due to overexposure or extreme noise. If this is so intensive, couldn't this affect the WX radar and other radios, for instance?


|-|ardy

[Markus Vitzethum]

Hi Hardy,

that's difficult to answer.

Let's look at the robots TEPCO sent into Fukushima. The first models were designed for radiation levels of (cumulative) of 1000 Sievert and started to fail after two hours. (6 to 8 Sievert are lethal for a human.)  ( https://www.theverge.com/2017/2/10/14580674/fukushima-record-high-radiation-cleaning-robot-recalled ). Later models were more successful. So you can probably build electronics / cameras to survive in a such a harsh environment. The Honeywell / Rockwell / Smith / Thales avionics are probably not as robust.

Another aspect ... when looking at a disaster site you'll probably have a very high radiation dose (say 10...80 mSievert / second) but, to my knowledge, rather comparatively low energy radiation. On the other hand, radiation in the upper atmosphere / space is not that high (say, 100 .. 400 mS / year) but, to my knowledge, rather high energy.  (For comparison, annual limit for aviation personell is 20 mS / year.)
Nice comparison: https://space.stackexchange.com/questions/17301/how-was-it-possible-for-the-apollo-11-to-film-and-take-pictures-with-such-radiat

The critical parameter for radiation hardening seems to be the energy deposited by radiation into the electronics (LET, Linear Energy Transfer). It seems that if you design for high energy radiation from outer space you might still have buffer for high flux, low energy radiation near a reactor.

Also, I think that in a cloud you are in a gaseous surrounding, already diluted compared to the surface. So the radiation density is probably much less. Also, the radiation source needs to get close to the electronics because there is at least some shielding (packaging, computer housing, airplane hull)

Regarding WX radar ... basically no idea, but since you'll need to amplify radar return signals next to a powerful transmitter, you'll have a sensitive amplifier, e.g. a super heterodyne amplifier with a local oscillator designed to amplify signals with a small SNR ratio. I guess the system will tolerate some extra noise but hard to tell how much.

Markus

[Hessel Oosten]

May be more to find in the literature of the Concorde ?

I did see several "radioactivity detectors.." in the flight engineers space of this aircraft, when I saw her in the fantastic Imperial War Museum (in fact a sort of aircraft museum) in Duxford near Cambridge (UK.
(https://www.iwm.org.uk/visits/iwm-duxford).

H.

[John H Watson]

Boeing told us about Neutron Single Event Upsets (NSEU). It affected the MCP, mostly, on 744's and would lock up some of the digital readouts until the CBs had been cycled. It was rare, though.

I see NSEUs were blamed for the QF27 incident

https://en.wikipedia.org/wiki/Single_event_upset

Perhaps not so much the cloud, but the nuclear explosion itself.

[Hardy Heinlin]

Thanks, Markus, Hessel, John ...

That effect on the MCP: Is that the LCD or the electro-magnetic version?


|-|ardy

[Jeroen Hoppenbrouwers]

Neither the LCD nor the electromechanical display parts themselves would be susceptible to a single alpha/beta particle. It's the CPU and the memory that will suffer from SEU, unless the register/memory cell has extra error correction bits.

A single parity bit will only detect the upset and then only a forced restart can help. Two or three bits per word will effectively mask or even correct a SEU and the really important stuff has such extra bits all over the place.

Of course the LCD version may have a significantly more powerful computer core; I don't know this. More powerful usually means smaller and more FETs and thus more susceptibility to SEU. So if there is a difference, I bet it is the LCD version that suffers most.

By the way the MCP is the most susceptible box as it is exposed nicely to whatever comes through the windshield. I believe radome is a good second but there's less sensitive electronics there, mostly radio stuff that is designed to cope with abuse.


Hoppie

[Hardy Heinlin]

Interesting ...

[torrence]

Two items come to my mind.  1. Altitude: reactor leakage and damage will mostly be important at low altitudes.  The material that gets into the stratosphere will be very diluted (All bets off if you're dealing with a large atmospheric nuclear explosion - penetrating radiation, electromagnetic pulse effects, etc. You don't want to be there.)
2. At any altitude, I assume that standard procedures would include closing off all outside air intake if possible.  Most fallout harm to humans results from ingesting/inhaling radioactive particles that have relatively low energies but can play havoc with unprotected tissues.  So radioactive cloud particles on the exterior of the aircraft wouldn't be much of a problem as long as the ship was isolated and cleaned off after landing.  As mentioned in this thread, very high energy cosmic rays constitute most of the background hazard to aircraft equipment, crews and passengers - for frequent flyers the dose can build up to equivalent of multiple chest X-rays over time, not catastrophic but something to keep in mind. 

Cheers
Torrence

[John H Watson]

That effect on the MCP: Is that the LCD or the electro-magnetic version?

It was first mentioned in days of electro-magnetic displays. As Hoppie says, it's the microprocessors which are susceptible. I don't know if the LCD type had any additional shielding.

It wasn't damage, per se, but logic states changing and confusing the microprocessors. We were told to cycle the CBs and if that fixed it, scroll slowly through every value on the MCP to see if they all worked. It used to take ages. It did catch me out once, however. The displays froze (I think altitude) and I cycled the CBs and checked all the digits, and signed it off as serviceable, but it failed on the next flight (so not an SEU).

The female captain wasn't amused ))) She thought I was pulling her leg when she saw my initial write-up... and probably angry on the second leg when it failed. It was a 767 doing short domestic runs. It must take a bit of creativity to produce a workaround for a failed altitude selector.

[Hardy Heinlin]

Thanks, Torrence, John.

It must take a bit of creativity to produce a workaround for a failed altitude selector.

I guess within the target altitude conflict zone she used the V/S mode and at FMC altitude capture VNAV PTH :-)


|-|ardy