AA 757 loses 7500ft in turbulence encounter

[andrasz]

I'm surprised it has not been picked up here, reported on AVH. Incident happened 30 August:

An American Airlines Boeing 757-200, registration N177AN performing flight AA-213 (dep Aug 29th) from Miami,FL (USA) to Brasilia,DF (Brazil), was enroute at FL350 about 160nm west of Caracas (Venezuela) when the aircraft lost more than 7500 feet within a minute. The crew recovered the aircraft below FL275, then radioed "We lost altitude due to severe turbulence and are climbing back to FL350".

It does not sound like a controlled descent... Anybody in a position to enlighten us ?

[AMS]

perhaps there is a clue in the following:

"The crew recovered the aircraft below FL275, then radioed "We lost altitude due to severe turbulence and are climbing back to FL350"."

:}

[poorjohn]

More generally, I hope a bunch of scientists somewhere have been granted a pot of money to tell us if the atmosphere has already become a significantly more dangerous place than our aircraft and systems were designed for. Some folks may wish it weren't so (and despite my individual thought that the atmosphere 'seems' to be more violent than a couple of decades ago, they may well be right).

[Stanwell]

An interesting 'incident'. The detail will also be interesting.


poorjohn's post reminds me of that famous exclamation from Chicken Little...

[andrasz]

perhaps there is a clue...

Let's just say if that aircraft was under control at all times, it was a helluva downdraft...

[jmmoric]

Is the aircraft under control when you loose 7000+ feet from something you can't control?

[Stanwell]

....just like the motorcyclist on another thread who, quote... "I was in complete control until I hit the fence".

[moonburn]

PJ, Funny you should say that, I think you may find that is not an ""individual thought"" if they asked enough of us it might even become an established fact.:)

[Herod]

I agree with PJ's point. I've been retired now for ten years, but I reckon in the fifteen or so years before that the average tops of a CB in Europe went up by several thousand feet. Perhaps someone with a met. background would know the facts.

[glendalegoon]

simply look up the definitions of turbulence both severe and extreme to find if the plane was in control

;-)

funny, if I had lost 7500 feet in turbulence, I don't think I would climb back up to see it again!

[justanotherflyer]

I reckon in the fifteen or so years before that the average tops of a CB in Europe went up by several thousand feet.

Curiously enough, the average height of cloud tops is, in fact, falling (http://www.jpl.nasa.gov/news/news.php?release=2012-046).

[Herod]

Ah well, I retired in Sep '04, so that was before it really became noticeable!;)

[captplaystation]

Gone over the Alps at F410 sometimes when that wasn't nearly enough . . . certainly wasn't how it was portrayed in my Met exam for my ATPL circa 1983.

I don't remember the level of turbulence en-route in Europe as being so severe 20 years ago. . . is it just my imagination ? or I am becoming sensitive with age. . . . . . bless :rolleyes:

[Sober Lark]

Not to worry, you're not imagining it. New classifications of 'severe turbulence' are being discovered all the time. ;)

[Nemrytter]

More generally, I hope a bunch of scientists somewhere have been granted a pot of money to tell us if the atmosphere has already become a significantly more dangerous place than our aircraft and systems were designed for.I've applied for funding for something similar to this for several years, it's only in the last ~18 months that funding bodies have decided it's worth looking at.
Curiously enough, the average height of cloud tops is, in fact, falling.The other poster was talking about CBs, not clouds in general. The reduction in height was due to a reduction in Cirrus clouds.

[Ian W]

The Accumulated Cyclone Energy (ACE) has dropped globally over the last few years. There have been less hurricanes and less tornadoes. The 'global average temperature' (which is not really a useful metric**) has risen by just over a degree Centigrade since the beginning of manned flight. In the last 17 years there has been no statistically significant atmospheric warming (called the 'Pause' by the IPCC).

What has happened is that over the last few years the jetstreams have become more latitudinal (i.e. more lobes and those lobes extending more equatorward - called the Polar Vortex by the weather men in the USA - see earth :: an animated map of global wind, weather, and ocean conditions (http://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-44.52,40.99,353)) probably because the Hadley convection cells that are driven by the convection in the Intertropical Convergence Zone are less active (lots of discussion and research in that area). The latitudinal jetstreams could mean that associated turbulence with both jetstreams and jetstreaks, is found in areas where it normally would not be expected.





** The average global temperature has been described as being as useful as an average phone number.

[oldoberon]

IAN W

The average global temperature has been described as being as useful as an average phone number.

not seen that one before , great one :-)

[Nemrytter]

The Accumulated Cyclone Energy (ACE) has dropped globally over the last few years. There have been less hurricanes and less tornadoes. To actually address Herod's original point: The average max altitude of a CB over Europe has increased by about 400 meters (~1200ft) between 2007 and 2014. On a global scale there is no significant trend.

As for the rest of your post: That's better confined to jet blast where there's a thread full of similar rhetoric.:ok:

[Algol]

How many times have you heard passengers say 'oh it was terrible, we hit an air pocket and dropped like a stone'?
In 30+ years of flying I've never come across one of these mysterious 'air pockets'. This must have been one!

[sherburn2LA]

surely you would be more likely to drop in a 'no air pocket'

[JammedStab]

The other day,

A14O0165: Atlantic Southeast Airlines, flight 4538 (EMB-145LR, registration N16954) departed Grand Rapids (KGRR) destined for Newark (KEWR). Due to weather the flight deviated north and was transitioning through Canadian airspace at FL 370. Approximately 53 NM west of London, ON the aircraft encountered severe weather and turbulence. ATC reported the aircraft climbing and then descending to FL 340, with a rapid rate of descent (approximately 8800 fpm). There was no reported damage.

[mikedreamer787]

funny, if I had lost 7500 feet in turbulence, I don't think I would climb back up to see it again!

+1

I lost 2000ft once in severe bloody CAT at 350
and decided to stay where I was slamdunked!

[poorjohn]

No offense but who and why would write this 'report'? And what exactly would be in this report?This is best answered by a poster up-tread who actually does such research for a living and seems to have gotten some funding after a couple of years of asking.

If this was directed to me as OP: I assume that either the FAA or NASA would grant funding to a university with the right atmospheric weather skills (perhaps involving NOAA?).

Neither agency has funding to spare these days, and one poster suggested the thought was chicken-little-sky-is-falling nonsense. Any organization asked to pony up some money would have to consider that possibility but could start with a relatively inexpensive overview.

The effort would probably revisit and update the previous work that established how nasty the atmosphere could be expected to be and therefore how strong our aero vehicles needed to be to provide the one-in-x-billion max failure rate everyone on board expects to enjoy.

Fortunately it seems that we're nowhere near wings tearing off - the guys who look at the growing body of telemetered flight data can agree - but the concern in this thread is about uncontrollable departure from flight path in ever-more-crowded airspace, so the study would certainly be expected to quantify that problem too. It wouldn't surprise me to learn that's never been studied as a threat.

So far all we have is anecdote so Chicken Little is certainly a possibility. Anecdotally, turbulence seems to injure persons (usually FAs) about once a week, compared to 'very, very seldom' in the past. I personally don't remember a previous severe-turbulence-induced (rendering crew unable to navigate off the centerline) altitude excursion like this one. (Another ~3k bust also recently mentioned.) Maybe it's just the AvHerald effect, and ignorance is really bliss.

[Prober]

40 years of aviation gave me only 3 occasions to cause lower muscle contractions due to turbulence. The first was in the tropics, flying in a military light aircraft. The initial indication was the HF headset, which was usually hung on the VHF frequency change knob thus handy for a quick grab, rising up like the Indian rope trick and waving about in front of me. Next came a cloud of dust from the floor boards followed by any loose objects floating around as if weightless. Then came a breath-removing crash and the aircraft carried on as if nothing had happened – except that I had lost 1,300ft. It might not seem much, except that I had only been at 4,000ft beforehand. It was a fine afternoon and, although I was flying close to a mountain range, there was no turbulence other than the usual heat bubbles.
Second was flying out of Madrid one summer evening and the weather radar showed Cb over the majority of its screen. Reaching 310 the speed decreased rapidly and an increase of power gave an overtemp on all engines. The problem was solved as we fell almost immediately to 270 and all went back to normal. I cannot recall ATC’s exact response except that they said that we should not bother them with such problems as they had enough of their own!
The third was over the Ukraine on a spring afternoon at 370. There was a rapid fluctuation of the outside air temperature on page Progress 2, of plus or minus 10-12 degrees within a few seconds. This was followed by a very strong rolling motion which took the two of us to control. It seemed as if we had reached almost 90 degrees from level flight, but I expect it was nearer 50 – 60. This lasted for about 5 minutes in clear air, and then it all went back to normal.
The second incident can be explained by our knowledge of the atmosphere, but the other two have puzzled me for a long time. I was lucky in that an old-timer once told me to keep an eye on the outside air temp. It could always give you a clue.
I now dig the veg patch – much safer!

[ROSCO328]

Interesting to read all of above. I only fly in Europe and have done for past 12 years. I've been convinced for a while now that it's a much more hostile environment than years past I.e more jet streams, higher jet speeds and much larger cells than I can honestly recall. I would even say I fly more conservative nowadays and certainly confirm with ATC if their has been " ride reports " on our routing when checking in on a frequency ( based on forecast ). Sometimes F.o's look at me like I'm a paranoid fart but then I mention an old word from times gone by " AIRMANSHIP ". :ok:

[Nemrytter]

If this was directed to me as OP: I assume that either the FAA or NASA would grant funding to a university with the right atmospheric weather skills (perhaps involving NOAA?). Both NASA and NOAA fund research into aviation weather. I presume that the FAA does too but I've never seen any of their staff, or anyone funded by them, at conferences or in research papers (not that I've been paying particular attention to looking for them, mind you).

[FLCH]

It seemed as if we had reached almost 90 degrees from level flight, but I expect it was nearer 50 – 60. This lasted for about 5 minutes in clear air, and then it all went back to normal.

That must have felt like an eternity !

[HDRW]

I remember my mother referring to "air pockets" when I was a kid (she was a very nervous passenger), and I now know the technical term: CAT, but I've always wondered what it actually is?

As I see it, the possibilities for causing sudden loss of altitude are:

1 - A "pocket" of low-pressure air, causing loss of lift (would also cause lowering of IAS since the density of air hitting the pitot is lower).

2 - A downward-flowing column of air, so the aircraft still has the same lift (and IAS) and is flying straight-and-level, but the air it's flying through is going down taking the aircraft with it.

3 - Sudden tailwind, causing loss of IAS and lift.

Any others?

Does anyone know which of these is involved in CAT?

I don't suppose anyone looks at the IAS indicator when this sort of thing happens? :-)

[FlightDetent]

7500 feet to lose, we are not hearing the full story. My 2pc.

[ATC Watcher]

In 30+ years of flying I've never come across one of these mysterious 'air pockets'. This must have been one!

Well in French they are called " trous d'air " or " air holes" and yes , they do exist, but you only noticed them if you are a pax :E.

back to the thread : dropping 7500ft and climbing again to original altitude ? From an ATC point of view this does not make sense if it was caused by severe turbulence. .Maybe a camera stuck somewhere again ?:rolleyes:

[blind pew]

An air hole is what you punch in a can so that you can pour the liquid out without it glugging.
In principal there are two forms of CAT...those caused by shear between layers and rotor.
The atmosphere is a bit like a lava lamp with "bubbles" of air with different homogenous properties. They don't easily mix and it's the shear due to speed differences that cause the turbulence. Sometimes this is associated with temperature difference hence the aircraft can go from a sustainable altitude to one where the engines do not produce enough thrust (WAT).
Vertical shears are normally associated with thermal differences I.E. Thunderstorms.- IMHO the most dangerous as often poor recovery techniques can cause catastrophic failure.
The correct procedure is to fly a fixed attitude manually with fixed thrust and trims settings...you accept the altitude gain/loss unless you is near terra firma.

The second type is normally associated with mountain wave systems and is a relatively stationary tumble dryer like motion at low level although I have been knocked unconscious in a rotor associated with convergence.
But if a pilok says he hit an air pocket he must be right ....could be man made such as a SAM.

[henra]

7500 feet to lose, we are not hearing the full story. My 2pc.

+ 1.

Scrap 'Air pockets' or 'downdrafts'. If it were 750ft maybe yes, but 7500??
Only with a complete LoC you will see such numbers.

[FlightDetent]

Exactly mu point. LoCs do not happen due to air pockets.

[harrryw]

fl370 -fl340 =3000ft which I can accept. 7500 ft seems a big drop.