Triggered lightning

[dakarman]

Hi all. Quick question from the back seats to those who know if i may. I am a regular customer in the back of the choppers in the north sea with a reasonable aviation background and I should have been on a chopper inbound today.
Instead of course its another night of offshore food and the cancellation of several choppers today including mine was based on grounding due to triggered lightning.
I checked for historical lightning strikes this afternoon and found none and I also have an app that gives a CAPE index - aparently a risk of lightning based on convection, also negligable.
The only reasoning i could find was the metar for egpd this afternoon indicated cb or tcu.
Could anyone please enlighten me on the decision making behind grounding flights for this reason? I also wonder if its company specific thing as other companies were flying today.
I would like to share this info with others offshore as one bet just now is that this company had their xmas party today.
Thanks.

[Self loading bear]

Dakarman,

This brings back memories from yesteryears. I was thinking al most the same years ago when Bristow flew for Shell/NAM for Den Helder Netherlands. Bristow canceled flights before other operators.

I was at that time not so much enlightened about helicopter flying as I am now thanks to Pprune Rotorheads!

Triggered lightning is a real threat and Bristow has experience with it!
There is a good Air crash investigation documentary about it which you might want to look at while you are locked-up on board tonight:

http://www.dailymotion.com/video/x57hst1

I have experienced a triggered lightning strike as passenger on board a fixed wing during Final approach to Schiphol AMS. And i can tell you, although only the wing tip was touched, the bang scared me enough in order not to question any decision on cancelling a flight for this threat.

It might be that some operators are more carefull about it as others (Bristow?), but I also heared the the threat can be quite local and other operators might be able to fly around it on their way to other platforms.
Perhaps our fellow Pprune offshore pilots can give enlighting on that?

Cheers SLB

[diginagain]

dakarman, you might find that an enquiry to the Helicopter Safety Steering Group at Step Change In Safety will provide your answer. https://www.stepchangeinsafety.net/about-step-change-safety/steering-groups/helicopter-safety

[Noiseboy]

It is an algorithm developed by the met office to predict areas in which the helicopter being present may trigger strikes that might not otherwise occur, therefore forecasts which predict 'natural' lightening are not relevant.

There is a page on their website which dictates whether flights can go, go subject to certain other conditions being present or absent, or not go at all. This may affect a rig or the enroute phase, cutting off access. It could be fine for the outbound, but not good for the inbound time period, therefore cancelling a flight in total.

It is very flakey and generally changes beyond recognition from the +6 hour time predicted to what it subsequently says when that time is actually here, so causes far more disruption than it should. However, if by grounding hundreds of flights over a season, the 1 to 3 strikes per year are prevented perhaps it's worth it?

[tu154]

Ah triggered lightning.

All 4 companies use a Met Office forecasting tool which basically gives go areas, go areas if you can stay clear of cloud and in good visibility, and no go areas. If the computer model says your flight is to go through a no go area, then you just can't do it. The model is updated regularly, and seems to change it's mind very often which makes planning difficult.

Christmas parties. What are they? No chance any company would cancel flights on that basis.

[pants on fire...]

Computer says No.

[dakarman]

Thanks all for the quick replies.
The step change in safety link seemed to hide its information but the rest of the replies remind me of the truism to check pprune search before asking.
The Aircrash video seems to be one i have seen before but shall look again when i have quick enough internet to try and maybe also not the day before i get on another chopper.
My xmas party comment was intended as toungue in cheek, after all, how many companies are generous enough to do xmas parties now.
Finally i have one other small question. I have found the links to the Met Office Helibrief portal but obviously cant see it. Is there something like a prediction percentage that would be different amongst companies or is todays disparity between operators a location thing? My understanding is it was over egpd that the problem existed so do some operators have a higher tolerance?
I guess I would also quickly like to ask if anyone has the info, hows it looking for tomorrow? (Saturday 16th am).
Cheers again.

[GKaplan]

Here (https://drive.google.com/open?id=1YL9VbmOwV0REEIm9IobHTfE6dH3FnGGE)

This is the picture just now, the forecast at this time only goes up to 3am.

As said above the difficulty for the crew is to figure out where in space we are going to be at each time when scrolling the forecast hour after hour.
We can fly in amber and yellow without too much restrictions but red is a no-go.

[Apate]

The three UK operators all use the same Met Office tool and follow the same rules. I surmise NHV also do, but don't know for certain.

As previous messages have stated, the 'forecast' no go areas do seem to change on a regular basis. So it is quite feasible that a longer range flight would launch based on the forecast that crew were presented with, and a later shorter range flight might have a forecast that would preclude them from launching into the same area that the earlier flight might now be flying through.

Today I saw flights recovering back to Aberdeen at a time the tool was saying Aberdeen was red, so no flights will launch.

It's all a bit messy, but rest assured there is no conspiracy and there is no difference in rules between operators. What does change is the forecast, and it changes far too frequently! We do try our best to get you guys home, but we do have to follow the rules. Hopefully you view that as a good thing.

As for tomorrow the predicative tool only looks ahead by up to 6 hours, so tomorrow morning is not yet visible. Overnight it looks to be changeable :-) Most of the weather seems to be East of a line from Harding to ETAP. Later, East of Shetland doesn't look good.

[dakarman]

Well thanks to everyone i now know a lot more about triggered lightning and its definitely fair to say if a chopper does not fly for reasons to avoid crashing, i am fine with that!
All my land based forecasts show a nicer day tomorrow so fingers crossed.

[tu154]

Temperature is a good predictor, cold showery weather with a northerly airflow bad. Warmer mild stuff good! Anything about +5 at sea level should be ok.

[Evil Twin]

Yeehaa an interesting thread, and no grandstanding from anyone. :ok:

[albatross]

A long time ago in the tropics...as a 76 new co-pilot new to the area flogging along in moderate rain with a benign radar picture well clear of any nasty stuff....suddenly heard a rapid "tick, tick, tick" in the headphones...asked the Capt ( a great guy with lots of time in tropical areas ) "What's that ticking noise?". His reply was "Oh Crap!!" this was followed by a big pink flash/bang so I followed his instructions. He told me afterwards that that strange fast ticking often preceded a close lightning bolt. Strange but true.

[Special 25]

Agree with all of the above - The Triggered Lightning screens do make for very 'dynamic' planning, hence you might find your flight can be cancelled and another not too far away could still be possible.

Worth bearing in mind that despite the scary videos and information bulletins, whilst lightning is something to be avoided for sure, the net result of a strike is typically very benign. The helicopters are designed to take a lightning strike and dissipate the energy, allowing it to flow through and exit the aircraft harmlessly.

Still, for the operator there is a very expensive investigation and engineering process afterwards. They used to talk about $2m a strike about 10 years ago. Not sure if that's based on any actual fact or just something engineers would say to make us feel bad!

[Self loading bear]

Still, for the operator there is a very expensive investigation and engineering process afterwards. They used to talk about $2m a strike about 10 years ago. Not sure if that's based on any actual fact or just something engineers would say to make us feel bad!

Did I read somewhere on the thread about the H225 Norway crash that Airbus decided to scrap the whole MGB after lightning strike from now on? Or was that someones proposal?

Edit:
It is in the Airbus video about the crash investigation at 5:30 min:
“It has been decided to withdraw from service every gearbox which has suffered ... Lightning strike.....”
But that does probably mean overhaul or really scrap?

SLB