V1Rotate

Hello,
Was just going thru my ATP written test and came across this question:

"Precipitation static problems caused by defective dischargers may include

answer: Complete loss of VHF communications, 30degrees of compass error, high pitched audio squeals, and erratic instrument readouts."

Thru-out my training I don't recall ever learning about this phenomenon, does anyone know more about this? Kinda sounds like something that might happen in a thunderstorm, but I want to make sure I understand this, because it's sounds like it could make for kinda a bad day, lol.

jungle

For the test just give the answer they have programmed.

Yes it happens, usually in dry precip(snow, ice crystals) at or above the freezing level and may or may not be in the area of a thunderstorm. Heavy dust can cause the same effect. The good news is that it is fairly rare in modern aircraft in good repair. Even heavy St. Elmo's fire or a lightning strike will rarely cause a serious problem. Good luck on the test.

bagofhammers

I have experienced this several times flying westbound over the cascades into Seattle. If I flew into moderate or worse rain (our aircraft didn't have radar), I would go NORDO for 20 to 30 seconds, just static. It made no difference if I keyed the mic or turned the squelch up or down, just loud, constant static until I exited the rain. I have never experienced the compass errors, high pitched audio squeals, or erratic instrument readouts associated with precipitation induced static though, just the complete loss of VHF communications.

V1Rotate

Interesting. I had heard of St. Elmo's fire before. I know that there was an A340 that flew thru some volcanic ash over SE asia somewhere that encountered St. Elmo's fire, and ultimately multiple engine failures, not sure if they experienced radio trouble or not though.

Ewfflyer

TBM's are horrible at this, but it's only on very certain occasions. I've had it happen twice in my 2.5yrs flying them. One time was at 15k, heavy rain everywhere, and the second was at FL240 about 20-40nm ahead of a front, going parallel to it. It blocks out both in and out, so it really does leave you in a NORDO situation, but usually after a few minutes you get out of it. I contemplated a heading change on the FL240 occurance because we were in it for too long and just couldn't hear anything at all, and Center never heard our request for a new heading either.

The best St. Elmo's I had was on an old C310P. I had props, tip-tanks, and windshield all just glowing! I think it was my first "near t-storm" experience as a freight-dog when I started out. Didn't even have a strike-finder in that POS to know what was coming.

rickair7777

St. Elmos Fire is very common in the flight levels, I see it several times a year in routine airline ops. It is harmless, although it does indicate the existence of localized static charge buildup.

The CRJ has many static wicks, which seem to work well since I've never had radio or nav problems in that airplane. Some of the static wicks are grounding items if missing, so apparently they are important.

tomgoodman

We used to get "high pitched audio squeals" when the crew van hit potholes in New York.

detpilot

I always wondered why composite aircraft like the Cirrus don't have static wicks. I attributed it (probably incorrectly) to the lack of an ADF.

Ewfflyer

I would say it's more of a lack of metal surfaces to build the static charge on, so therefor there's no need to disapate something that's not there.

Does bring into the conversation on the composite aircraft the modifications for lightning protection. I dont' believe the Cirrus has any just because it's a piston single, but jets such as the Premier do.(I think it's a mesh inlayed into the fuselage, but not really sure)

detpilot

It does.


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