[TwentyDeewar]

On 9th August, 2024, an ATR 72 turboprop belonging to a regional Brazilian carrier - Voepass Linhas Aereas - crashed just outside Sao Paolo while it was at cruise altitude.

Videos show the plane in a flatspin as it plummeted to the ground. As per reports, there were warnings for severe icing at the altitude the plane was cruising at. Hard to believe icing can bring down a modern airliner, remains to be seen what the investigators find out.

RIP to the 61 souls lost.

Link to video

[Jeroen]

Originally Posted by TwentyDeewar

Hard to believe icing can bring down a modern airliner, remains to be seen what the investigators find out.
]

Still remains to be seen of course, but icing can indeed bring a modern airliner down. Has happened in the past. Icing is a very dangerous phenomena. Only a small layer of ice can dramatically change the lift characteristics of a wing.

All modern airliners have de-icing features. Varying from pneumatic boots that inflate breaking up the ice, to heated air being blown across the wing.

On the little planes I flew we had a system that would, through a series of small holes in the wing, seep de-icing fluid across the wing leading edge.

If the de-icing system are not working 100% you cannot fly into a known area of icing conditions. There are also known cases where pilots simply forgot to switch the system on!

If you want to read some more, I happened to have come across this booklet.

https://www.theairlinepilots.com/for...operations.pdf

Here is an example of those pneumatic de-icing boots on an ATR.

https://youtu.be/BdHawSnHtRk?si=zT-eFbo9je6Epgaq

Jeroen

[itwasntme]

Originally Posted by Jeroen

All modern airliners have de-icing features. Varying from pneumatic boots that inflate breaking up the ice, to heated air being blown across the wing.

Here an example of those pneumatic de-icing boots on an ATR

Jeroen, maybe a silly question but do ATRs flying in Indian airspace have these boots as standard? Somehow never noticed them although it has been some time since I actually boarded one.

EDIT: Googled a bit and did find this noticeably black strip on the leading edges.

[sandeepmdas]

1,217 aircraft built. 40 hull losses, 13 of them fatal.

The ATR 72 flies feeder and regional routes, and let us say 50% of its operation is almost always from smaller and / or remote airports with limited equipment. While many major airlines use them, many are with fly-by-night operators. Naturally, the pilot training and evaluation programs too might not be up to the standard. Indeed, eight crashes were happened due to human error.

Still, the stats are not exactly on par with that of the 21st century aviation. 5 accidents due to icing alone.

(Data sourced from Wikipedia)

[V.Narayan]

Originally Posted by Jeroen

Still remains to be seen of course, but icing can indeed bring a modern airliner down. Has happened in the past. Icing is a very dangerous phenomena. Only a small layer of ice can dramatically change the lift characteristics of a wing.

Thank you as always for your excellent factual posts on aviation.

Originally Posted by itwasntme

Jeroen, maybe a silly question but do ATRs flying in Indian airspace have these boots as standard? Somehow never noticed them although it has been some time since I actually boarded one.

Yes all airliners that fly in Indian airspace carry anti-icing equipment.

Ice formation as Jeroen states can drastically alter lift - overall and asymmetric between the wings. It could also degrade the effectiveness of the flight control surfaces. In automobile terms think of it as your brakes & steering getting whooshy and you cannot reduce the accelerator {airspeed needed}. Once an airliner type of aircraft gets into a tailspin recovery can be difficult. Fighter jets practise this but an airliner is not designed for it in the normal course.

[skanchan95]

Originally Posted by V.Narayan

Ice formation as Jeroen states can drastically alter lift - overall and asymmetric between the wings. It could also degrade the effectiveness of the flight control surfaces. In automobile terms think of it as your brakes & steering getting whooshy and you cannot reduce the accelerator {airspeed needed}. Once an airliner type of aircraft gets into a tailspin recovery can be difficult. Fighter jets practise this but an airliner is not designed for it in the normal course.

It can't be described any better or easy to understand than what you have Sir.

There was an episode on Nat Geo's Air Crash Investigations(Mayday)of Ice build up on wings and propellors in flight and how it proved fatal for the crew and passengers of ATR-42/72s( that is not to say it does not/cannot happen to other aircraft types), but it was no co-incidence that when this first started happening with ATRs, they had no clue what caused the crashes of those earlier ATRs, until one ATR crew was lucky enough to recover their ATR-42 from a similar icing situation:

https://www.dailymotion.com/video/x8l816o

This "Frozen in Flight" episode was one of Air Crash Investigations best episodes ever(there was similar one with early Boeing 737s suffering from rudder hard over issue), which was great as well.

[ashkamath]

Originally Posted by itwasntme

do ATRs flying in Indian airspace have these boots as standard? Somehow never noticed them although it has been some time since I actually boarded one.

De-icing on plane wings are essentially for colder regions / europe where ice/snow is a regular feature. In India, a tropical country, icing is rarely an issue for the aircrafts. I believe, No airliner in India, flying domestically has ever faced an icing issue on its wings ( again I could be wrong, I havent checked the facts). Having said that, de-icing equipments / facilities are perhaps made available in all airports in India (just guessing) as per their Standard airport operation practices. And of course by design, all aircrafts have anti-icing system on board as an integral part of the aircraft safety sytems.

I also heard that the turbo prop ATR-42 and the larger ATR-72 are very unforgiving aircrafts (though they have an excellent safety record) and thus any unforeseen / unexpected deviation from their standard / normal flying / operational failure / mechanical failure could turn catastrophic in quick time. I mean, the pilots have a very small window of time to take corrective / remedial measures to bring their aircraft under control. So, the margin of error for the pilots virtually is very less in ATR-72 aircrafts.

[Jeroen]

Originally Posted by ashkamath

De-icing on plane wings are essentially for colder regions / europe where ice/snow is a regular feature. In India, a tropical country, icing is rarely an issue for the aircrafts. I believe, No airliner in India, flying domestically has ever faced an icing issue on its wings ( again I could be wrong, I havent checked the facts). Having said that, de-icing equipments / facilities are perhaps made available in all airports in India (just guessing) as per their Standard airport operation practices. And of course by design, all aircrafts have anti-icing system on board as an integral part of the aircraft safety sytems..

Sorry, but you are mixing thing up I believe.. I think you might be thinking of de-icing of a plane prior to a flight? Usually due to ice/snow on the airplane prior to take off. That needs to be removed. The wings, tail section and so on get sprayed with a de-icing fluid prior to take off.

Here we are discussing (de) icing in flight. Which is a pretty regular occurrence and all airliners are equipped with de-icing systems.

Jeroen

[TSIboy]

Originally Posted by sandeepmdas

1,217 aircraft built. 40 hull losses, 13 of them fatal.

The ATR 72 flies feeder and regional routes, and let us say 50% of its operation is almost always from smaller and / or remote airports with limited equipment. While many major airlines use them, many are with fly-by-night operators. Naturally, the pilot training and evaluation programs too might not be up to the standard. Indeed, eight crashes were happened due to human error.

Still, the stats are not exactly on par with that of the 21st century aviation. 5 accidents due to icing alone.

Because that's what these aircraft are meant to do - operate from smaller places, feeder operations etc. which might be marginally riskier than larger operations. We have a lot of ATRs in India too with Indigo being one of the largest operators.

Both the ATR 42 & 72 are big, complex aircraft so training is on par with say an A320 maybe even more with a lower level of automation & demanding aircraft handling. Anyways not going to comment on pilot training & evaluation but human error is generally the most common cause of all accidents/incidents (in general not talking about this case).

Icing stands out simply because cruising levels of these planes are much lower than jetliners (which fly above weather most of the time) So they are always affected by weather - icing, rain, turbulence etc.

All the videos show the plane in a flat spin which in itself is a deadly thing for most non aerobatic aircraft.

Further, the T tail design of the aircraft makes it harder to recover from a stall and almost impossible from such a flat spin. The flight controls will be ineffective in such an attitude due to the aerodynamics, vertical rates could easily go higher than 5-6000 feet per minute which would be ground in less than 3mins. Rest in peace to all departed.

[libranof1987]

Originally Posted by TwentyDeewar

Hard to believe icing can bring down a modern airliner, remains to be seen what the investigators find out.

As Jeroen and V.Narayan have explained, icing in/over various aircraft systems and sensors has been deemed to the root cause for multiple aircraft incidents over the years. It isn't the icing itself, but what it leads to: incorrect / inconsistent sensor readings for instance that actually cause the crash.

The crash of Air France 447 has been a notable, and one that brought about a lot of focus on icing in-flight, incident.

According to the final report, the accident resulted from this succession of major events:

- Temporary inconsistency between the measured speeds, likely as a result of the obstruction of the pitot tubes by ice crystals, caused autopilot disconnection and [flight control mode] reconfiguration to "alternate law (ALT)".
- The crew made inappropriate control inputs that destabilized the flight path.
- The crew failed to follow appropriate procedure for loss of displayed airspeed information.

https://en.wikipedia.org/wiki/Air_France_Flight_447

[V.Narayan]

Originally Posted by ashkamath

De-icing on plane wings are essentially for colder regions / europe where ice/snow is a regular feature. In India, a tropical country, icing is rarely an issue for the aircrafts. I believe, No airliner in India, flying domestically has ever faced an icing issue on its wings ( again I could be wrong, I havent checked the facts). Having said that, de-icing equipments / facilities are perhaps made available in all airports in India (just guessing) as per their Standard airport operation practices. And of course by design, all aircrafts have anti-icing system on board as an integral part of the aircraft safety sytems.

I also heard that the turbo prop ATR-42 and the larger ATR-72 are very unforgiving aircrafts (though they have an excellent safety record) and thus any unforeseen / unexpected deviation from their standard / normal flying / operational failure / mechanical failure could turn catastrophic in quick time. I mean, the pilots have a very small window of time to take corrective / remedial measures to bring their aircraft under control. So, the margin of error for the pilots virtually is very less in ATR-72 aircrafts.

As Jeroen points out you are mixing things. One is deicing on the ground prior to the flight. Photo below. This is something most of us have often witnessed in Northern latitudes.



What caused this crash, subject to investigation, is icing on the wing & flight control surfaces as shown in the photo below. This forms while in flight depending on humidity, formation of super cooled water droplets that freeze on contact with a cold metal surface such as a wing, propeller blade, engine inlet, aileron etc and disturbs the aerodynamics, the lift and the effectiveness of the surface.



The temperature on the ground {tropical} has only a limited effect on the weather conditions at 30,000 or 40,000 feet. It is always below minus 25 degrees centigrade in any case! Weather conditions that contain water droplets & are very cold {0 to minus 20 degrees} cause icing regardless of altitude.

Hope this helps.

[ashkamath]

Originally Posted by Jeroen

Sorry, but you are mixing thing up I believe.. I think you might be thinking of de-icing of a plane prior to a flight? Usually due to ice/snow on the airplane prior to take off. That needs to be removed. The wings, tail section and so on get sprayed with a de-icing fluid prior to take off.

Here we are discussing (de) icing in flight. Which is a pretty regular occurrence and all airliners are equipped with de-icing systems.

I agree there could some mix up here. I was referring to de-icing the wings on ground prior to flight take off.

You must be referring to the in-built anti-ice system that's a standard system across every commercial aircraft.

I stand corrected.

[Jeroen]

If you want to hear a real expert talk about this accident have a look at this.

https://youtu.be/8SJO-nEOong?si=VHlbBZ97WLdKrPYm

Jeroen