Now thats turbulence for you

[pelmet]

The smartest thing they did was to leave the autopilot on......

"C-FLHJ, a Boeing 737-400 aircraft operated by Flair Airlines, was conducting flight FLE613 from Vancouver Intl (CYVR), BC to Edmonton Intl (CYEG), AB. As the flight crew expected turbulence passing FL310 during the climb to cruising altitude after the departure from CYVR, the FASTEN SEAT BELT sign was turned on and the captain instructed the cabin crew to be seated. Shortly thereafter when the aircraft was on autopilot, the aircraft pitched up 20° and the airspeed increased by 40 kts. The aircraft rolled 45° to the right, which required full left aileron deflection, then rolled 30° to the left, which was corrected with full right aileron deflection. The VSI displayed a speed of over 6000 fpm up. After a subsequent loss of 25 KIAS, the aircraft levelled off at FL350 with significant ongoing buffeting. The flight crew elected to leave the autopilot on the whole time, and let it make the corrections. There were no injuries; however, 14 passengers became ill as a result of the turbulence. The operator reported that the autopilot performed adequately, did not disengage throughout the event, and that no aircraft limitations were exceeded. An SMS report was filed."

Limitation exceedences and injuries typically happen when the autopilot is disengaged at high altitude.

[ant_321]

I’ve wondered how bad turbulence would have to get for the 737 auto pilot to kick off. Apparently really bad.

[pelmet]

Once again, the flightcrew wisely kept the autopilot engaged...

"C-FTVF, a Boeing 737-800 aircraft operated by Air Transat, was conducting flight TSC447 from Holguin/Frank País Intl (MUHG), Cuba to Toronto/Lester B. Pearson Intl (CYYZ), ON with 6 crew members and 183 passengers on board. During cruise flight at FL290, approximately 90 nm eastsoutheast of Pittsburgh Intl (KPIT), PA, the flight encountered severe turbulence for approximately 30 seconds. Altitude and pitch variations were minor. Speed variations were +/- 10 kts, and the aircraft experienced rolls of approximately 30° that were managed by the auto-pilot. The flight crew requested and was authorized to FL270, and the aircraft continued to destination without further incident. There were no injuries. The operator’s maintenance inspected the aircraft in accordance with the Aircraft Maintenance Manual (AMM). No defects were found, and the aircraft was returned to service."

[KAG]

I've had the autopilot kick off on approach in the 737 due to turbulence and it was only moderate. It's good to know at higher levels it will remain engaged.
I will say, the above described second scenario is not severe turb. In severe turb you're out of control.

[pelmet]

I've had the autopilot kick off on approach in the 737 due to turbulence and it was only moderate. It's good to know at higher levels it will remain engaged.
I will say, the above described second scenario is not severe turb. In severe turb you're out of control.

Thanks,

I suppose the definition of out of control can vary from person to person. Uncommanded 30 degree banks(ie 60 bank angle changes is certainly significant control issue).

It sounds like your autopilot did not disconnect at high altitude. Perhaps there are different parameters or maybe it depends on the autopilot type, 737 type, specific installation, etc.

Disconnecting at high altitude can be extremely risky as the aircraft is much more sensitive to a given input as compared to lower altitudes. Overcontrol is a significant risk, potentially leading to injuries.

[W5]

I have had the auto-pilot kick off at FL400 (B737-700); severe turb. which only lasted 10-15 seconds.

[pelmet]

I have had the auto-pilot kick off at FL400 (B737-700); severe turb. which only lasted 10-15 seconds.

I'm sure it can happen...at which point one has no choice but to manually fly for at least a certain period of time. But if one has a choice, I suggest keeping the autopilot on unless it is absolutely necessary to do otherwise.

['97 Tercel]

maybe had CWS mode engaged

[pelmet]

"C-GHPN, a Boeing 767-300 operated by Air Canada Rouge, was conducting flight ROU1944 from
Toronto / Lester B. Pearson Intl (CYYZ), ON to Bogota / El Nuevo Dorado Intl (SKBO), Colombia
with 6 crew members and 282 passengers onboard. When enroute about 380nm north of SKBO,
the aircraft encountered unexpected turbulence. The flight crew reported an altitude loss of
approximately 500ft; one cabin crew member received minor injuries. No passenger injures were
reported. The flight continued to the destination without further events."


An airliner instructor pilot that I know insists that whenever you hear about there being a significant altitude loss, it was because the autopilot disengaged(either manually or it tripped off). I have never encountered severe turbulence. Has anyone ever encountered severe turbulence in an airliner in level flight and had a significant altitude change while the autopilot remained engaged.

[valleyboy]

I have encountered it and while it wasn't instantaneous it warned us of what was ahead. It started with aggressive trim rolling on the auto pilot with a gain of 200 feet and then a lost of 400 feet. It wasn't violent initially, like riding a roller coaster. Altitude hold was disengage and then we hit the turbulence. Articles drifting by in the flight deck and a wild ride but the autopilot hung on but maybe that's because we had taken altitude hold off. We could not maintain our altitude so we descended and found better air.

[pelmet]

I have encountered it and while it wasn't instantaneous it warned us of what was ahead. It started with aggressive trim rolling on the auto pilot with a gain of 200 feet and then a lost of 400 feet. It wasn't violent initially, like riding a roller coaster. Altitude hold was disengage and then we hit the turbulence. Articles drifting by in the flight deck and a wild ride but the autopilot hung on but maybe that's because we had taken altitude hold off. We could not maintain our altitude so we defended and found better air.

Autopilot from an aircraft designed in the ‘60’s. I wonder if such an experience applies to new generation(designed in ‘80’s and newer) aircraft.

[pelmet]

C-FNJZ, a CRJ 900 operated by Jazz Aviation LP was conducting flight AC8670 from Vancouver
Intl. (CYVR), BC to San Diego Intl. (KSAN), CA. While on top at FL270 Vicinity of PASKE (Porter,
CA), the crew encountered clear air turbulence. Airspeed fluctuated +/-30kts but did not over-speed
nor did the Auto Pilot kick off. Turbulence and Ignition buttons were on. The turbulence made
reading the instruments on the panel impossible as they were too blurry. The motion was up/down
as well as side/side. The seat belt signs were switched on about 2 min prior to the encounter.
Flight crew initiated descent to FL 250 where they had moderate to borderline severe turbulence.
Continuing descent to FL230 flight encountered a severe turbulence event that lasted
approximately 5 minutes. Flight climbed to FL250 where the turbulent event ceased. Maintenance
is arranging for an inspection.

[pelmet]

C-FSRY, a Jazz Aviation LP Bombardier DHC-8-400 aircraft, was conducting flight JZA8075 from
Vancouver Intl (CYVR), BC to Victoria Intl (CYYJ), BC with four crewmembers and forty
passengers on board. During the descent into CYYJ, the flight encountered severe turbulence with
the captain reporting that the aircraft could not be controlled. Both pilots reported never having
experienced such severe turbulence and made the decision to return to CYVR. The flight landed in
CYVR with no injuries to the crew or passengers. Maintenance conducted a turbulence inspection
and found no obvious defects. They downloaded the FDR data that showed that the aircraft had
not exceeded any vertical or lateral limits. The aircraft has been returned to service.


Good idea to keep those shoulder harnesses on.

[porcsord]

Both pilots reported never having
experienced such severe turbulence and made the decision to return to CYVR.

They say, having under 2000hrs between them...

[co-joe]

Pelmet, you keep saying the smartest thing to do is let the auto stay in control, and I'm not arguing that, but I was wondering, do you have any examples of crews who tried to hand fly and caused more harm than good in severe turbulence at altitude?

[pelmet]

The smartest thing they did was to leave the autopilot on......

"C-FLHJ, a Boeing 737-400 aircraft operated by Flair Airlines, was conducting flight FLE613 from Vancouver Intl (CYVR), BC to Edmonton Intl (CYEG), AB. As the flight crew expected turbulence passing FL310 during the climb to cruising altitude after the departure from CYVR, the FASTEN SEAT BELT sign was turned on and the captain instructed the cabin crew to be seated. Shortly thereafter when the aircraft was on autopilot, the aircraft pitched up 20° and the airspeed increased by 40 kts. The aircraft rolled 45° to the right, which required full left aileron deflection, then rolled 30° to the left, which was corrected with full right aileron deflection. The VSI displayed a speed of over 6000 fpm up. After a subsequent loss of 25 KIAS, the aircraft levelled off at FL350 with significant ongoing buffeting. The flight crew elected to leave the autopilot on the whole time, and let it make the corrections. There were no injuries; however, 14 passengers became ill as a result of the turbulence. The operator reported that the autopilot performed adequately, did not disengage throughout the event, and that no aircraft limitations were exceeded. An SMS report was filed."

Limitation exceedences and injuries typically happen when the autopilot is disengaged at high altitude.

C-GJFZ, an Air Canada Express CRJ900 was operating flight AC8844 from Vancouver
International Airport (CYVR), BC to San Francisco International Airport (KSFO), CA. At FL290, the
aircraft encountered severe turbulence. Swings in airspeed 20-30 kts, and there was altitude and
attitude changes of over +/- 100 feet. The auto pilot stayed on at all times and all crew and
passengers were strapped in. There was no loss of control at any time. All passengers were
prepared before the occurrence as the flight crew were advised of the sigmet area that was
published enroute by both ATC and dispatcher. The flight landed in KSFO with no further issue and
there was no emergency was declared. The flight crew was conferenced with their OCM and
agreed that it was severe turbulence.

[Dias]

Was this yesterday? Did they fly near that thunderstorm? I can imagine thunderstorms near mountainous terrain can produce some wild turbulence.