View Full Version : Heavy Metal and Thunderstorms

bush pelican
2nd Aug 2005, 23:40
With this mornings crash of an Air France jet landing in a thunderstorm, I would like to ask those qualified if there is a culture of accepting or continuing T.O. and Lngs. in thunderstorm conditions.
I often hear requests by heavies around BN to divert right and left of track in fairly benign conditions due WX. However the same level of concern doesn't seem to happen for the TO & Lng. For example, the FAA said that an audit of approaches and departures from Little Rock (after the overrun and crash there) showed that up to 60% of airliners ignored CB conditions in the vicinity of the airport and continued rather than holding or diverting.
Relatively recent events in Aust (thinking of BN and north) look a bit similar. I am pychologically challenged (shit scared) of CBs especially during an app, and I know I'll never experence the heavies, (old PA31 driver).
I've often wondered if there is a change of thinking about CBs, for operational reasons or otherwise, when one transitions up the big airstairs!
Thanks BP

2nd Aug 2005, 23:57
Yes heavies do request diversions around thunderstorms rather than fly through them.
Speaking for myself, and I guess most other pilots would do the same, whilst there are thunderstorms in the vicinity of an airport, I look at the radar and the surface conditions before I depart or make an approach.
If there is no way around the thunderstorm, I just hold off until the path is clear.

3rd Aug 2005, 00:22
In my previous life..... the rules stipulated that I shouldn't clear an aircraft to within 10nm of an active TS if he (few "she's" then) was below the Freezing Level, and 20nm if above the Freezing Level.

Nowadays, that's the criteria I apply to my personal avoidance of a TS.

BIG invisible shears can exist at BIG distances from storms ! :ooh:

3rd Aug 2005, 09:30
The Air France accident acts as a timely reminder to us that we should avoid TS's (both enroute and in the terminal area). I apologise for assumption that the accident was caused by TS.

From my experience, the radar picture can be complicated in the terminal area. It requires a degree of experience and judgement to determine if the weather returns are 1/ Significant thunderstorms, 2/ Towering cumulus but not thunderstorms, 3/ Monsoonal heavy rain caused by Nimbostratus (with and without embedded TS's), 4/ Ground Return from high terrain, etc, etc.

I have seen occasions when the radar picture looked awful. The entire screen Green, with Yellow areas and Red blobs. And yet the ride has subsequently been quite smooth.

I have seen clouds develop so rapidly as to almost bedevil belief. About a year ago in HKG the weather changed from CAVOK to a full-blown TS (with microburst alert + Severe windshear and turbulence) in 20 minutes. Given the number of other tasks vying for our attention in the terminal area, there is a limit to the amount of time one can devote to a radar picture that looked benign 5 minutes ago.

In the wake of this mornings accident, I am ruminating on my approach to TS's in the terminal area. I have never landed with a TS over the airport. But in recent years (as I look-back at some of the approaches I have flown) I suspect that I have narrowed my margin of separation from TS's to some degree. I think I will now go back to the old rule of thumb - delay take-off, and abandon approach, if TS's are within 10nm of the airport.

Isn't it a horrible coincidence that it is 20 years since the fateful Delta Airlines L1011 accident. This accident acted as a catalyst to the whole study of microburst events. It lead our occupation to our present understanding of how to handle microburst encounters. And, as I recall, escape strategy number one was - never be there in the first place.

3rd Aug 2005, 11:20
I was going to London on Speedbird 15 or 16 or whatever it was from Brisbane a number of years ago and the pilots announced that we were going to sit and wait until a cell passed before departing. When we boarded the sky was blue but obviously a big cell was coming across. We sat for maybe 20 minutes on the taxiway just off the runway (dunno the names) and lined up after the cell had obviously dumped its load on us.

Captain Can't
3rd Aug 2005, 12:15
the most amazing thing about delaying t/o (or whatever) for wx like CBs is, is the first to do so usually triggers a whole heap of radio traffic such as "yeah, we'll wait too" etc... but it makes you wonder when you do this, what others will do, often times you are blocking the way! so you feel like a big wet blanket, but it feels good when you watch the windsock whip around the compass whilst it p!sses pickhandles :bored: