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ATR 72 Icing & Loss of Control - Recovered

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ATR 72 Icing & Loss of Control - Recovered

Old 17th Dec 2017, 18:45
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ATR 72 Icing & Loss of Control - Recovered

I cannot find any thread started at the time (almost exactly a year ago) of a serious incident involving an ATR 72, for which an AAIB report has just been released. .

the Conclusion was;

The aircraft suffered an in-flight upset at FL130 after accruing airframe icing during the climb, resulting in the adverse aerodynamic effect of ice build-up on the wings. The crew were presented with a degraded perf caution but did not action the relevant checklist because they focused on climbing out of the icing conditions. The IAS was not maintained at or above red bug +10 kt and control of the aircraft was lost when a turn was initiated in the lnav mode of the flight director.
I think it's worth a read, not so much for the technical issues but for the Human Factors elements of why the crew did what they did.

If it's been done already in PPRuNe, apologies for not finding it, please delete...

PS I found a mention in PPRuNe, but buried in Airlines, Airports & Routes
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Old 17th Dec 2017, 19:00
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FYI:

https://aviation-safety.net/database...?id=19941031-1
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Old 17th Dec 2017, 19:06
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The ATR does not seem to like ice very much:

Incident: Jettime AT72 near Bergen on Nov 14th 2016, drops left then right wing in icing conditions
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Old 18th Dec 2017, 06:08
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NNUTS. In anything other than a High Speed Jet Transport (or pehaps VERY high performance Turboprop), out climbing ice is a fool's decision. Always was and always will be.
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Old 18th Dec 2017, 06:38
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control of the aircraft was lost when a turn was initiated in the lnav mode of the flight director.
With the potential of degraded performance, am I the only one that thinks they might have been better off actually flying the aircraft, or is this something peculiar to an ATR?
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Old 18th Dec 2017, 07:16
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The ATR has "normal speeds" and "icing speeds". The icing speeds are higher than normal speeds. Anytime the aircraft detects icing conditions a caution is generated and the icing speeds apply. Had the crew concentrated on flying the published speeds, loss of control would not have occurred.

American Eagle 4184 from Indianapolis to Chicago was the first such incident involving an ATR 72. Following this Aérospatiale did extensive icing testing and found the aircraft safe for icing conditions with a mod including larger de-icing boots.
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Old 18th Dec 2017, 08:02
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Bank angle limitations in severe icing conditions just released.
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Old 18th Dec 2017, 10:43
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With the potential of degraded performance, am I the only one that thinks they might have been better off actually flying the aircraft...........?
No, the QRH drill for severe icing - reproduced in the AAIB report - tells the crew to disconnect the AP (amongst other actions).
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Old 18th Dec 2017, 11:46
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Originally Posted by Domi View Post
Bank angle limitations in severe icing conditions just released.
If I recall correctly the American Eagle ATR was in a holding pattern.
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Old 18th Dec 2017, 12:40
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control of the aircraft was lost when a turn was initiated in the lnav mode of the flight director.
Flight Directors are an aid. To follow them blindly during inappropriate conditions is only asking for trouble. A universal problem it seems
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Old 18th Dec 2017, 12:45
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Flying slowly at a high angle of attack in a holding pattern with a cold soaked aircraft in icing conditions can cause grief.
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Old 18th Dec 2017, 13:02
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Originally Posted by RVF750 View Post
NNUTS. In anything other than a High Speed Jet Transport (or pehaps VERY high performance Turboprop), out climbing ice is a fool's decision. Always was and always will be.
Originally Posted by TangoAlphad View Post
Agreed. It is one thing continuing a climb through icing etc but if you are picking up ice to the degree of being performance limiting unless you can already see patches of blue you probably aren't going to get through it.
Although most of my turborop experience was not in the area where I live, the area where I live is a well-known location for severe icing conditions in freezing rain.

A retired test pilot that I know did Twin Otter in flight icing tests. His advice was that the worst of the icing was actually in quite narrow bands several thousand feet thick.

Of course, each situation is different but in a situation where one cannot descend to air warm enough to melt ice or clear of both cloud and icing(ie no freezing rain), I would consider climbing first. In the case of a warm front, you may get to warmer air.

With regard to climb/descend options......When in icing conditions, you will always have the capability to descend but the climb option may no longer exist if you chose the descend option first.

At night, you will never see blue patches and if there is a higher cloud layer, you won't see blue in the day either.

As I said, this is not based on significant personal experience in such conditions and I'm sure others could give theirs based on more personal experience.
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Old 18th Dec 2017, 13:52
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I experienced severe icing once, in a Shorts 360 back in '86. The conditions had brought another one down some 48 hours previously, luckily with no fatalities. Airborne some 30 minutes, diverted, never reduced below climb power, and had the throttles firewalled coming over the hedge. Never try to climb above it, unless you are CERTAIN that you can clear the conditions.
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Old 18th Dec 2017, 14:03
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Don't get slow in icing, if you do get slow don't turn, if you elect to turn use half bank until your not slow anymore.

The icing layer is rarely more than 3000 feet thick.
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Old 18th Dec 2017, 17:22
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new OEB says HiBank only if IAS > icing bug + 30kts (30 !) in severe icing condition, otherwise LoBank - AND consider to descend to maintain the required speed.
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Old 19th Dec 2017, 08:59
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Originally Posted by Small cog View Post
The AAIB report says that the Captain was PF and was also LTC. Makes you wonder ...
Makes it even more likely for something to happen, Captain more or less single crew and watching what the other guy is doing, agree he should be used to being exposed those kind of situations but no one os infalliable.

I used to fly a type similar to the ATR, underpowered and a slow climber, even moderate collections of ice would cause large speed reductions and even require level offs to maintain min ice speed.

Its not an inherant problem with the ATR, if you fly a low powered aircraft with poor climb performance you are going to spend lots of time climbing through icing levels and if you get slow or don't follow procedures any aircraft in that catagory will bite you.
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Old 19th Dec 2017, 10:22
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Originally Posted by Domi View Post
new OEB says HiBank only if IAS > icing bug + 30kts (30 !) in severe icing condition, otherwise LoBank - AND consider to descend to maintain the required speed.
Not only against you but this whole is hard to believe.

Actually they did a test flight. They managed it to figure out the maximum level in ice =FL130. They stalled the aircraft at KIAS 165!

Manufacturer say >red bug speed< +10- what means 175 KIAS is recommended. That is 10 knots margin above actual stall speed.
The report cite a server ice CL- what demand minimum ice speed +10.. Is that to understand as (red bug speed/165 +10) +10 = 185 KIAS ?!
And dear Domi, never ever accept any >high bank< (what a term). Many flight directors have a small bug, omitting half bank in case pilot selecting >direct to<. You could choose pilot off FD or use a bank mode.

Generally is a lack in understanding the stall subject.
Lift oppose weight. But that is valid only under the premise, continuous unaccelerated flight.
The weight is mass multiplied by G-load. A = Mass x G-load
If you fly, like in this case, exactly at stall speed, any increase of G-load will immediate stall the wing. For that in ice, always fly above stall speed for ice, avoid any turns, avoid accelerations.Those is part of aviate, what comes before CL.
If a stall occur, reduce the actual stall speed. Push gently the yoke forward. That way you fly a ballistic curve, that reducing the G-load, that reduce the stall speed!
If a spontaneous roll occur, avoid big aileron inputs. That will increase the average angle of attack, of the aileron of outer/upper wing. That part will likely stall, aircraft bank to opposite side. (In our case reached 73°).
As you loose altitude/dive; airspeed will increase, so normal airflow should reestablish.
During recovering; likely to divert from given clearance and stall is to report as well as severe ice, if you anticipate over-stress aircraft need to report . But relevant call is PAN. Mayday is movie style as in Sullivan Movie, irl commander did no std distress call.

In conclusion, I would say, this report is to revoke.
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Old 19th Dec 2017, 10:46
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Originally Posted by rak64 View Post
Not only against you but this whole is hard to believe.
The report cite a server ice CL- what demand minimum ice speed +10.. Is that to understand as (red bug speed/165 +10) +10 = 185 KIAS ?!
It's definitely to be understood as 185.
Your minimum icing speed, half bank protected, is increased by ten knots, if you want to fly full bank or NAV you need 10 knots on top of the new red bug.

The ATR is a piece of crap, happy not flying it anymore...
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Old 19th Dec 2017, 15:57
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If I remember right on the EMB-120 we used 210Kts min and autopilot off strongly recommended in icing. The autopilot off was to prevent control forces masking. We had similar loss of controls leading up to the min speed increase.
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Old 21st Dec 2017, 11:04
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You forgot about the fuel problem. If you stuck in ice, your cruising level is decreed, like in the here mentioned case, from FL190 down to FL130, the fuelplanning is not correct anymore. If not prepared for this you could easily land below minimum diversion fuel. 2 other reasons why fuel planning in ice is delicate. Performance in ice is less than in clean weather, less IAS with same powersetting, more FF for same speed. Early descend is needed and higher speeds/pwr-setting in descend needed. Maybe idle descent not possible because bleed air is not enough for cabin and deicing.

But all airplanes have limitations. The problem starts if you fly your current type like another type. You have to consider actual stall speed in ice could be high as 165 KIAS. (BTW, you can stall any AC at any speed, it depends on G-load). I've seen blackbox printouts from actual stalls of EMB-120 in ice that happens at KIAS 155. In C421 I experienced few at KIAS130. Laminar airfoil have tendency to stall at much higher airspeeeds in ice than clean.
Secondly manufactor recommend Flaps 15 as seen in CL, what indicated Fuselage create to much drag when maintaining higher AoA. (I remember the same for SD3-60, in case of engine failure.) Despite of CL airframe (fuselage) of ATR is not antiiced, or?
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