ATR-72 Crash in Brazil

ATRs and icing are a bad combination. Hang on to your hats, folks, this tale's going to be a long one. The ATR was the first aircraft to be globally certificated under the Joint Arcraft Airworthiness Standards Agreement, whereby all ICAO nations agreed to accept the airworthiness certification of an aircraft by it's originating nation at face value. No second guessing by other nations, as had been the case previously. Investigating the 1994 AmEagle crash at Roselawn IN, the NTSB determined that the unrecoverable spin was the result of a stall of the horizontal stabilizer, due to "bleed back" of ice behind the deicing boots, forming a ridge of ice on the (negative) lifting surface that detached the airflow and killed the horizontal stab's downforce. This caused the elevators to slam against the "nose down" stops, pitching the plane into a dive. When the speed increased and the stabilizer AoA decreased enough to reattach the air flow, and then stall negative, the elevators slammed nose up and drove the plane into an accelerated stall. A high G accelerated stall on a long slender wing like the ATR's is going to be super sensitive to the slightest asymmetry and highly likely to spin. With its long fuel filled wings and stretched fuselage, the ATR72 has a lot of distributed mass with a lot of rotational inertia, and it's narrow elevators are never going to get enough purchase in the roiled air of the rotation to lower the AoA and break the stall.
So what caused the bleed back icing that caused this whole event? Would you believe, droplet size? A lot of research by NTSB and FAA established that supercooled water droplets in superstable subfreezing air over the great plains of North America attained sizes seldom seen in the choppier air over Europe. These superstable droplets would remain as a flowable liquid longer after striking a fast moving airfoil, thus bleeding back farther before freezing than their European counterparts. In the case of the ATR, this was behind the boots. THE ATR HAD UNDERSIZED DEICE BOOTS!
This was news the Europeans didn't want to hear, and they insisted Roselawn was pilot error. The FAA revoked the ATR's icing certification, and the Canadians followed suit. All North American ATRs had to shift to sunnier climes, and Billy Clinton closed US airspace to foreign operated ATRs. In the end the US forced the ATR people to design and produce upgrade kits, and where feasible, to install them free of charge. This was accomplished by closing US airspace to all foreign airlines whose countries did not mandate the ATR fix. That policy was quietly maintained until the end of the Clinton administration. I don't think it's been maintained since. We may have just seen an outcome of that this week.
My ex went through AmEagle ATR72 initial training three years after Roselawn, and everybody in her class had to experience that event in the simulator. A real eye opener.

pb43 said:

The ATR has known issues with icing and the operating manuals reflect this. Stay within the limits in the operating manuals and the dangers are minimised.

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Head in the sand response for flawed aircraft certification standards. TP aircraft are generally vulnerable to icing and are less safe than modern western jet airliners, and yet they are interlaced within the same mass transport operating system. This is unsatisfactory. TP aircraft could be much safer but, they are built down to a cost and have weaker systems, such as the rubber de-icing boots. They can be built to better standards but, that would erode their operating margins. They exist because of a veneer of safety, underlain with simple cheap operating costs and vulnerability. Unsatisfactory.

Eng

DerAdlerIstGelandet said:

An ATR-72 with 62 people on board crashed today. The aircraft was filmed in a complete spin with virtually no forward airspeed.


View: https://x.com/AviationSafety/status/1821963083314835596?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1821963083314835596%7Ctwgr%5E83c54e82a2a719103f56d60a9b59a4893239a793%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fasn.flightsafety.org%2Fwikibase%2F409335

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Here is a link to the Airworthiness Directive requiring the monitoring system to alert the crew to icing. The idea being that if the autopilot is flying it may mask icing and finally switch off and hand the pilot an un flyable aircraft. https://ad.easa.europa.eu/blob/easa_ad_2009_0170.pdf/AD_2009-0170_2?trk=public_post_comment-text
Any aircraft operated outside of its capability will suffer. I haven't looked it up but from memory the ATR72 is certified for 30 minutes operation max in severe icing. So any "flight into known icing" presumes the crew will strive to escape icing conditions in less than 30 minutes.
I fully expect that ALL of the de-ice equipment and the performance monitoring system referenced in the AD are on the Minimum Equipment List (cannot fly if these are broken). For these reasons I doubt that this accident occurred with a crew flying a serviceable aircraft within certification / Pilot Operating Handbook limitations.
At this point I am favouring the speculation regarding the recent structural repairs or hijack, or, less exciting, simple deviation from MEL / POH.

Engineman said:

Head in the sand response for flawed aircraft certification standards. TP aircraft are generally vulnerable to icing and are less safe than modern western jet airliners, and yet they are interlaced within the same mass transport operating system. This is unsatisfactory. TP aircraft could be much safer but, they are built down to a cost and have weaker systems, such as the rubber de-icing boots. They can be built to better standards but, that would erode their operating margins. They exist because of a veneer of safety, underlain with simple cheap operating costs and vulnerability. Unsatisfactory.

Eng

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I am curious why you find pneumatic "boots" weaker than other systems?
I have heard arguments about engine bleed air anti ice vs. Electrical resistive anti ice where the system cost and weights were compared. I recall seeing the duct losses as being very severe (the hot bleed air cools off on the way to leading edge), and the performance loss to the engine taking away from available power as may be required to maintain altitude on a heavy aircraft gaining ice weight. Due to high bleed temperatures, the ducts nearest the engine can be forced into Inconel to tolerate. Earlier stage air may not have the temperature required after duct losses.
The 787 system is all electric except for the engine inlet, and seems to be an excellent system but was integrated into the aircraft's "low loss high voltage architecture ". From memory the 787 uses a strategy where zones are heated in sequence as opposed to everything on at the same time, so is partly a de-ice system. I have read of ultrasonic and piezo shock systems in development.
I personally experienced astoundingly severe icing in a Beech 1900. Three people on board and we porpoised with both engines at max power (not TO) periodic violent roll (aileron still had authority to recover). Able to hold altitude but only at max throttle. The props were throwing heavy ice at fuselage, with impacts moving forward as the mass increased. When we landed, thick slabs of hoar ice were sliding off the aircraft, some maybe 10 cm thick. But, there was only modest localized ice on wing and tail surfaces. We stood silently on the tarmac just watching the ice fall off. The copilot was pale from stress. Due to the crew reporting ATC had moved all traffic out of that area.

RichardSuhkoi said:

Here is a link to the Airworthiness Directive requiring the monitoring system to alert the crew to icing. The idea being that if the autopilot is flying it may mask icing and finally switch off and hand the pilot an un flyable aircraft. https://ad.easa.europa.eu/blob/easa_ad_2009_0170.pdf/AD_2009-0170_2?trk=public_post_comment-text
Any aircraft operated outside of its capability will suffer. I haven't looked it up but from memory the ATR72 is certified for 30 minutes operation max in severe icing. So any "flight into known icing" presumes the crew will strive to escape icing conditions in less than 30 minutes.
I fully expect that ALL of the de-ice equipment and the performance monitoring system referenced in the AD are on the Minimum Equipment List (cannot fly if these are broken). For these reasons I doubt that this accident occurred with a crew flying a serviceable aircraft within certification / Pilot Operating Handbook limitations.
At this point I am favouring the speculation regarding the recent structural repairs or hijack, or, less exciting, simple deviation from MEL / POH.

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I agree with most of what you posted, and I agree that it is most likely going to found that Icing of the elevators will be found to be the cause. I used to work for an airline (Simmonds) that originally bought the ATR-42 & 72 aircraft that was purchased by American Eagle, and the ATR-72 involved in the Indiana crash was an aircraft I worked on. I left before the buyout by American Eagle. But I followed the investigation closely. And spoke with a couple of Pilots that flew the types that I stayed in touch with. They both had spoken of sluggish and erratic vertical performance of the types in icing conditions. But both had fortunately recognized the signs of icing before it became critical.
Also just to clarify most items on an MEL list can be inoperative. With conditions such as verifying that backup systems operate normally, and depending on the system can be inoperative for 10 or 3 days in most instances. There also can be flight restrictions such as Altitude, weight, or operating into know icing condition. Sometimes the restriction can be that it can be operated to a maintenance base for repair.

The other instance of the acceptance of international airworthiness approval I became aware of was the crash of a Fisher Brothers CASA C-212 at Detroit Metro Airport in the late 1980's. The aircraft was certified without a stall warning system installed by either the Spanish or European authority. The FAA accepts this if the aircraft has noticeable buffeting before the onset of a stall. In the case of the CASA C-212 did not have the warning horn, a stick shaker, or a natural buffet. And the international regulators approved it in that condition.
That approval cost the lives of 8 or 9 people that morning in Detroit. I watched it happen from the cockpit of a B-727 that I was Taxing from the Hangar to the Gate. I was standing by for clearance to cross the active runway that the CASA was landing on. It turned onto its back and if it would have gone to its right instead of its left it probably would have hit the 727 I was Taxing!

It continues to astound me that these events continue to occur decades after the issue is identified. At least the CASA's were soon out of service due to age and economic reasons. At least as far as regular passenger service is concerned.

Pneumatic boots are just fine. They are a bitch to remove and install though.

cammerjeff said:

I agree with most of what you posted, and I agree that it is most likely going to found that Icing of the elevators will be found to be the cause. I used to work for an airline (Simmonds) that originally bought the ATR-42 & 72 aircraft that was purchased by American Eagle, and the ATR-72 involved in the Indiana crash was an aircraft I worked on. I left before the buyout by American Eagle. But I followed the investigation closely. And spoke with a couple of Pilots that flew the types that I stayed in touch with. They both had spoken of sluggish and erratic vertical performance of the types in icing conditions. But both had fortunately recognized the signs of icing before it became critical.
Also just to clarify most items on an MEL list can be inoperative. With conditions such as verifying that backup systems operate normally, and depending on the system can be inoperative for 10 or 3 days in most instances. There also can be flight restrictions such as Altitude, weight, or operating into know icing condition. Sometimes the restriction can be that it can be operated to a maintenance base for repair.

The other instance of the acceptance of international airworthiness approval I became aware of was the crash of a Fisher Brothers CASA C-212 at Detroit Metro Airport in the late 1980's. The aircraft was certified without a stall warning system installed by either the Spanish or European authority. The FAA accepts this if the aircraft has noticeable buffeting before the onset of a stall. In the case of the CASA C-212 did not have the warning horn, a stick shaker, or a natural buffet. And the international regulators approved it in that condition.
That approval cost the lives of 8 or 9 people that morning in Detroit. I watched it happen from the cockpit of a B-727 that I was Taxing from the Hangar to the Gate. I was standing by for clearance to cross the active runway that the CASA was landing on. It turned onto its back and if it would have gone to its right instead of its left it probably would have hit the 727 I was Taxing!

It continues to astound me that these events continue to occur decades after the issue is identified. At least the CASA's were soon out of service due to age and economic reasons. At least as far as regular passenger service is concerned.

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Wow. I looked at MMEL. https://www.faa.gov/aircraft/draft_docs/mmel/MMEL_ATR-72_Rev_21_Draft.pdf
To my dismay the boots are on a time limited dispatch!! (As you said) One prop boot set as well.
This is disappointing to me.
I expected anll boots and de-ice fail horn and prop boots all on ferry flight only dispatch. I am disappointed by what may be unreasonable pressure from the businessmen having successfully reduced rules intended to assure safe operating. Yes of course it's up to the pilot in the end but he has a mortgage. Icing conditions are not always predicted and now I want to see the maintenance log on this aircraft. Did it dispatch with any of the relevant systems degraded? The de-ice system fail horn? The performance monitoring system? A prop boot? The fxxking elevator boots?? I personally would not want to get on a plane missing any of its boots. My experience on a beech 1900D showed me that that aircraft could survive extreme icing BUT WITH A STRUGGLE and with very very light load. With part fuel, three souls, We were unable to climb out, we were too heavy! The ice weight and drag was on various surfaces, but with the boots working there was heavy ice on wingtips and even on roof and belly. Areas that typically accumulate only thin ice we had massive thick ice. I feel there was no margin at all and wonder how things would have been with full pax and fuel? Never mind losing an engine. This brings me back to permitting dispatch with one of two prop boots unserviceable, I do not like this at all.

DerAdlerIstGelandet said:

Pneumatic boots are just fine. They are a bitch to remove and install though.

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I think these French made ones are fully bonded to leading edge and back with Viton glue? Is that correct?
So you need to abrade down then apply paint stripper type chemicals to soften the bond, utterly clean, and rebond? So at least 10 hours on the clock?

RichardSuhkoi said:

I think these French made ones are fully bonded to leading edge and back with Viton glue? Is that correct?
So you need to abrade down then apply paint stripper type chemicals to soften the bond, utterly clean, and rebond? So at least 10 hours on the clock?

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We installed our boots with L100 adhesive. Its a yellow colored adhesive. We would first mark a line using a chalk line along the center of the leading edge, and then mark it with a marker, then put three layers of the adhesive on the leading edge and the boot. Then when we were ready install we would roll the boot up into two halves. Then you roll out the boot over the leading edge while another mechanic activates the adhesive with a lil toloul (spelling… lol). Then you would have lay the upper and lower parts down doing the same thing, taking care not to get bubbles/air pockets under the boot.

Removing them sucked. The adhesive is so strong we would rip them off in strips. Then you would have to clean thd leading edge. We did that by "tenting" the leading edge with tolule soaked rags, and then using a non-metallic scraper to remove the boot material and adhesive residue.

DerAdlerIstGelandet said:

We installed our boots with L100 adhesive. Its a yellow colored adhesive. We would first mark a line using a chalk line along the center of the leading edge, and then mark it with a marker, then put three layers of the adhesive on the leading edge. Then when we were ready install we would roll the boot up into two halves. Then you roll out the boot over the leading edge while another mechanic activates the adhesive with a lil toloul (spelling… lol). Then you would have lay the upper and lower parts down doing the same thing, taking care not to get bubbles/air pockets under the boot.

Removing them sucked. The adhesive is so strong we would rip them off in strips. Then you would have to clean thd leading edge. We did that by "tenting" the leading edge with tolule soaked rags, and then using a non-metallic scraper to remove the boot material and adhesive residue.

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Thank you for bonding these on well. I can guess that if they delaminated in flight it's a bad day

RichardSuhkoi said:

Thank you for bonding these on well. I can guess that if they delaminated in flight it's a bad day

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If the mechanic uses the right adhesive the boot is not coming off. Lol

I`m brazilian, i can tell a few things that has happened:

• Voepass is a old airline which is hanging on by being the regional codeshare of bigger airlines, especially LATAM
• Tons of client complaints, bad smelling planes, broken seats, weird noises in the cabin, my aunt flew on that airline a couple weeks before the crash and it was a horrible experience, she was terrified, and she is a prosecutor who has to fly several times a month, so she's used to normal flying
• After the crash several pilots complained of poor maintenance, no rest periods, the FAs called one of the ATRs "hopes and wishes" because to them that was the only way the plane was still flying
• A lot of stuff leaked from July, including the de-icing gear being considered INOP
• An ATR from another airline was stuck in icing and nearly crashed due to lack of UPRT in 2013, from what i've watched from ATR training instructors on youtube is that you keep full power and you declare a emergency so you don't wait for clearance before descending to avoid icing

A Voepass pilot reported in June, during a public hearing at the National Civil Aviation Agency (Anac), a routine of pressure from the airline to carry out flights outside the work schedule and without respecting the crew's rest needs.

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He said he had already woken up with eight missed calls on the phone, on his day off, with requests to fly. And he warned that this situation increased the risk of an air disaster occurring at some point.

"The company sometimes calls me to take a flight: 'Come on, I can do it [to fly]'. But [the stopover] says it's not to go", said pilot Luis Claudio de Almeida, on June 28, at a hearing at the regulatory agency that discussed changing the rules on crew members' working hours.

The answer, according to him, came immediately: "No. Go, go, go, whatever."

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Voepass planes were having problems with the deicing system, according to images obtained by TV
Records show "inoperative" warnings on mechanisms crucial to preventing ice on aircraft parts

While the Center for Research and Prevention of Aeronautical Accidents (Cenipa) does not release the final report on the crash of the Voepass plane in Vinhedo, in the interior of São Paulo, one of the main hypotheses raised is that of excess ice on the wings of the aircraft. In new images obtained by Fantástico on Sunday, the 18th, Voepass plane panels indicate problems with the deicing system.

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The photos released by the TV Globo program further increase speculation about the possible causes of the fall. In one of them, made in July, it is possible to see an "inoperative" warning for the deicing system on the same plane that crashed in Vinhedo. The feature is important because, when inflated, it 'expels' ice from parts of the aircraft.
Another image from the same period also captured a "deicing system inoperative" warning on a plane from the same airline. A third photo shows the ATR with the fuel level indicator in an inoperative state.

The most recent click obtained by the program is from August 1st. In the photo, the plane's performance monitor is missing the selector button. On an aircraft, it is important that the feature works to ensure flight safety.

This is because, when turning the selector knob, the pilot indicates the total weight of the plane. Based on this information, the system starts to indicate whether the performance in the air is correct and whether the ice is not hampering the flight.

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Voepass manual prevents flight attendants from recording aircraft faults

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Anac (National Civil Aviation Agency) identified, a month ago, problems in the procedures adopted by VoePass for reporting maintenance failures on flights operated by the company.

An inspection by the regulatory body noted that the company prohibits flight attendants from directly reporting problems associated with the maintenance of its aircraft. Instead, failures must be reported to pilots for eventual inclusion in a technical report.

Anac understands that this policy discourages the reporting of technical problems on aircraft operated by the company and requests that the company review the guidance…

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tonycat77 said:

I`m brazilian, i can tell a few things that has happened:

• Voepass is a old airline which is hanging on by being the regional codeshare of bigger airlines, especially LATAM
• Tons of client complaints, bad smelling planes, broken seats, weird noises in the cabin, my aunt flew on that airline a couple weeks before the crash and it was a horrible experience, she was terrified, and she is a prosecutor who has to fly several times a month, so she's used to normal flying
• After the crash several pilots complained of poor maintenance, no rest periods, the FAs called one of the ATRs "hopes and wishes" because to them that was the only way the plane was still flying
• A lot of stuff leaked from July, including the de-icing gear being considered INOP
• An ATR from another airline was stuck in icing and nearly crashed due to lack of UPRT in 2013, from what i've watched from ATR training instructors on youtube is that you keep full power and you declare a emergency so you don't wait for clearance before descending to avoid icing

Piloto relata pressão da Voepass para exceder jornada e trabalhar em dia de folga: “Vai, vai que dá para voar“ | CNN Brasil

Em audiência pública na Anac, profissional da companhia aérea contou rotina de cobranças e fadiga: "Não queremos entrar em estatística de acidentes"

www.cnnbrasil.com.br

Aviões da Voepass estavam com problemas no sistema de degelo, indicam imagens obtidas por TV

Registros mostram avisos de "inoperante" em mecanismos cruciais para evitar o gelo em peças da aeronave

www.terra.com.br

Andreza Matais: Manual da Voepass impede comissários de registrarem falhas nas aeronaves

A Anac (Agência Nacional de Aviação Civil) identificou, há um mês, problemas nos procedimentos adotados pela VoePass para o reporte de falhas de manutenção em voos operados pela empresa.Uma inspeção do órgão regulador observou que a companhia proíbe co

noticias.uol.com.br

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If the crashed aircraft flew into heavy ice with a boot inoperative the risk would be very high. If the performance monitor system is inoperative the risk is the crew wouldn't notice ice soon enough to take action.
I hope we learn the facts soon.