severe turbulence

[NOSIGN]

Many of the days in this August gone had forecast severe turbulence here in Vic.

I flew many days this August and would classify the turbulence intensity as moderate turbulance or moderate chop on the most intense days. Was I just lucky :confused:?

I have experienced severe and extreme turbulence in the past and in no uncertain terms, no August days came close to that intensity.

Are BoM and pilot reports describing the circumstances the best they can? Are forecasters and or Pilots covering their arses and overestimating conditions just to cover all bases?

Severe turbulance forecasts certainly make a Pilot consider altitudes, speeds, securing baggage etc but I still chose to fly each of the days with severe turbulence forecasts. Am I an idiot :=? Am I hardened :cool:? I know that I'm not the only one :}!

The danger that I am ascerting to is that after landing, either some Pilots gain unrealistic confidence in their ability to handle "severe" conditions OR some Pilots may conlcude that all wx forecasts are pessimistic and not give them much weight during flight planning.

Did anybody lose control of their aircraft during August? What is a large change in attitude?

[tmpffisch]

Technical definitions of turbulence are:

Moderate - Small changes in airspeed, changes between 0.5g-1g, difficulty in walking, occupants feel strain against seat belts, loose objects move about

Severe - Abrupt changes in aircraft attiude or altitude, changes greater than 1.0g, being forced violently against seat belts, lose objects are tossed about.

Were the reports you read on TAF's or ARFOR? ARFOR would have the details being a bit more specific, such as MOD TURB, SEV in CB whereas the TAF for the same location would just take this as being severe.

[muffman]

Had one day in August southwest of KAT where it was some of the heaviest I've had in the last 4 or 5 years but otherwise just frequent moderate

[ravan]

Just to add to tmpffisch's post of definitions:

Moderate turbulence - "there may be moderate changes in aircraft attitude and/or altitude, but the aircraft remains under positive control at all times..."

Severe turbulence - "abrupt changes in aircraft attitude and/or altitude - aircraft may be out of control for short periods - usually, large variations in airspeed..."
(AIP Gen 3.4 Pg 107 Appendix 2 Note 11)

You may not experience severe turbulence often, but any forecast of it , either in ARFOR or Sigmet, has me paying attention to the area in which it is forecast. Poor aircraft handling in severe turbulence, where accelerometer readings exceed 1.0g, can very quickly impose loads on the aircraft which approach its load factor limits.

Besides that, it's not much fun for you or the pax!

[Capt Fathom]

Along similar lines.....

The forecast is for severe turbulence. You elect to go anyway.

A passenger is injured and there is damage to the aircraft after an encounter with turbulence!

Where does that leave you from a legal standpoint?

Two aircraft have been lost over recent times, possibly from encounters with severe turbulence?

Think about it!

[NOSIGN]

G'Day TMPFFISCH,

I am refering to the ARFOR SIGMETS, although for a more western area a typical example

WSAU21 APRF 042152
YMMM SIGMET PH02 VALID 042200/050200 YPRF-
YMMM MELBOURNE FIR SEV TURB FCST WI S4100E11200 - S3600E11200 -
S3500E11800 - S3500E12000 - S3700E12000 - S4100E11700 - S4100E 11200
BLW A050 MOV NE 25KTS INTSF
STS:REV SIGMET PH01 041805/042200

This is a very broad area where if you enter... you run the risk of losing control of your aircraft.

Capt Fathom, good question. Are you obliged to inform passengers of the forecast conditions?

"ladies and gentleman, thank-you for chosing to fly with xxx air, please ensure your belts are buckled firmly low and tight 'round you hips because SEVERE turbulence has been forecast for our departure." :uhoh::{ " Please don't be alarmed, we at xxx air fly through these conditions daily:rolleyes:. Please swipe your credit card..." and so it goes.

Or... "Mr Stein, nice to see you today Sir, would you like to postpone the business meeting in Hong Kong today because we run the risk of encountering forecast SEVERE turbulence during our flight from Sydney today?" - "Sure Captain, let's have a beer today instead".

[Tankengine]

If your upset because the forecast was for severe and you found only moderate : Did you fly in ALL the area for ALL the time of the forecast?:ugh::ugh::ugh::ugh::ugh::ugh::ugh::ugh:

One day if you keep asking your self if your an idiot you may give youreslf an answer!:}

[puff]

For those that haven't seen it some pretty sobering reading of the horrific effects of severe turb - sure it's an accident that many remember. Again I know of a pilot that flew that night in question and their comment was it was rough - but no worse than a lot of nights in VIC at that time of year. Again heaps of other a/c flew that night no worries - what do you do?

http://www.atsb.gov.au/publications/investigation_reports/2007/AAIR/pdf/AO2007029_prelim.pdf

[Ted D Bear]

That report is sobering reading. It is only preliminary - and we may never know much more. For me, a forecast of severe turbulence is more likely to cause a scrub than just about anything other than a forecast of severe ice. I might fly if there is a forecast of severe turbulence if I don't have pax, I know the route (and terrain, and its effect on turbulence) and I can complete the flight in VMC by day - especially if I'm flying something with a relatively high wing loading. But the thought of encountering fair dinkum severe turb in the dark somewhere remote from much lighting, or in IMC, with the autopilot auto-disconnecting, gives me the heeby jeebies ... :eek:

[eocvictim]

One of our a/c flew straight through Steve's track that night within 3nm of the crash site 20 mins prior with only minor turb, I'd flown along the VFR lane about 1.5hours earlier and experienced moderate turb. The "Swan hill" run had flown through there without any major reports either.

The forecast was there and while no one else experienced any of the wx associated, there was obviously reason for it. Conjecture is that they may have flown into a tornado/sheer funnel and having seen them in the area I wouldn't be surprised.

[bushy]

The "severe turbulence" forecasts have been coming for years and thousands of aircraft have flown through the relevent areas with no problems thousands of times. The forecasts are logical, and the met people do a very good job but the forecasts are very broad and they do appear to be very, very conservative. And believeable?

I believe that the Americans have radar which can identify local areas of turbulence, but we don't, and never will while our government departments have to make a profit.

I also wonder about the crashes of two aero commanders.
(sure it happened) But identical aicraft types, and one that had been authorised to carry overloads.

[eocvictim]

I also wonder about the crashes of two aero commanders.
(sure it happened) But identical aicraft types, and one that had been authorised to carry overloads.

Actually YJB hadn't been modified for the increased MTOW and was extremely low time for a Shrike. I heard it had been cleared from a corrosion inspection relatively recently prior to the break up.

[glekichi]

The problem I have in Australia after having flown overseas is that it is forecast much too conservatively. The result is that nobody has any idea when a flight REALLY should be cancelled.

Severe turbulence SHOULD mean that all flights in the relevant area should be cancelled.

At the moment, in the area I fly in OZ, I would guess about a fifth of all flights throughout the year would be cancelled if we didn't fly under the current 'severe'.

Not good enough.

[sockedunnecessarily]

where accelerometer readings exceed 1.0g

You can't fly an aircraft around without exceeding 1.0g. The post referred to abrupt CHANGES of 1.0g. Sorry for being all technical, but there is a big, big difference.

[bushy]

I have seen evidence of what must have been a tornado in central Australia.(not forecast)
A caravan and two water tanks were shredded and spread around the plain, the top was ripped out of a gum tree, but an unrestrained 172 parked nearby did not move.
A very violent and very localised nasty weather event.

[breakfastburrito]

Capt Fathom makes a very good point!
Personally I request PIREPs prior to entering the forcast area.

[Dalek Leader]

Turbulence forecasting is a difficult problem for any aviation met.
What can be severe turb for one aircraft type may be mild or moderate for another - depends on aircraft weight, penetration speed and configuration. What is severe turb for a microlight is not for an F50 or a 737 on climbout. BoM forecasts for ALL users and with extremely limited resources and tools for forecasting turb, you will only get broad and usually unspecific forecasts of turb.

Some types of turb can be viewed on some specialised radars (available at some airports in the US). Not all radars can (very few in Oz!), and has to be occurring to be seen - nowcasting rather than forecasting it ahead of time so pilots can avoid it. Not a high percentage of Oz is covered by weather radar, let alone those that can suggest severe turb areas.

Our best tool for alerting others to sev turb is PIREPS - but we see fewer and fewer of these due mainly I think to pilots not doing them and overworked ATC not having time to pass them on. Usually do not advise of aircraft type either. Perhaps some of it is like landing in unforecast fog/low cloud - if I don't report it, I won't get in trouble for landing in it!

Users of ARFORs also should be aware that they are getting extremely good value for money for the product - ARFOR users pay very little of the aviation forecasting budget (main airlines pay a very high percentage of the costs recovered) but ARFOR forecasting and weather watch is approx 45% of the total time allocated to aviation forecasting in most weather offices. I DO NOT think GA should yet more fees, just be aware that we do the best we can and you get a product for almost free from people with very limited resources.

[rmcdonal]

Technical definitions of turbulence are:

Moderate - Small changes in airspeed, changes between 0.5g-1g, difficulty in walking, occupants feel strain against seat belts, loose objects move about

What counts as a small change in airspeed? 10kts+?

[-438]

A bigger issue I believe is ATC not passing on turbulence reports.
I'm not sure if it is a requirement for ATC to pass on reports of turbulence to following aircraft but from my experience it has become less common in recent years.
Maybe controllers are too under the pump with the large areas they cover??

[ForkTailedDrKiller]

Severe turbulence SHOULD mean that all flights in the relevant area should be cancelled

WSAU21 ASRF 170708
YBBB SIGMET SY07 VALID 170800/171200 YSRF-
YBBB BRISBANE FIR SEV TURB FCST WI YHAY - HRD - YGDA - YSTW - S3330
E15300 - S3730 E15100 - YMCO - YSWG - YHAY BLW A100 STN NC
STS:REV SIGMET SY06 170800/171200


I assume that there are/will be no aircraft movements below A100 within this area ????

Dr :8

[davidgrant]

I heard an interesting definition of turbulence from an old graybeard called the coffee test.
If the turbulence was enough to cause your coffee to swill around inside the cup...that's light.
If it slops out of the cup...its moderate.
If you have whitecaps on your coffee...moderate to severe.
If you cant fine the cup..its severe

[NOSIGN]

:ok: David!