Exposure to Aircraft Bleed-air Contaminants Among Airline Workers - Health Care

PORTUGUÊS  ENGLISH (scroll down)

Boeing Settles Toxic Cabin air Case

Boeing concorda com causa judicial sobre toxicidade de ar de cabine

Gerenciamento de exposição aos contaminantes de ar de sangria de aeronaves entre trabalhadores de empresa aérea

Um guia para provedores de serviço de saúde

Robert Harrison, MD, MPH¹
Judith Murawski, MSc, CIH²
Eileen McNeely, PhD³
Judie Guerriero, RN, MPH¹
Donald Milton, MD, DrPh<sup>4

1</sup>University of California, San Francisco
  ²Association of Flight Attendants
   ³Harvard School of Public Health
    ⁴University of Massachusetts Lowell

Financiamento para este projeto foi fornecido pela Administração Federal de Aviação (FAA)
Gabinete de Medicina Aerospacial e é parte de um projeto colaborativo entre o Consórcio Ocupacional de Pesquisa de Saúde na Aviação (OHRCA) e o Centro de Excelência de pesquisa de Ambiente de Cabine de Aeronaves de Linhas Aéreas (ACER)/ Embora a agência FAA de Medicina Aerospacial tenha patrocinado o projeto, ela nem endossa nem rejeita as descobertas desta pesquisa.

O ar externo fornecido para a cabine de passageiros e pilotos em avião comercial ("ar de sangria") pode  às vezes estar contaminado com bio-óleo* do motor e/ou fluido hidráulico. Como um resultado desta contaminação, trabalhadores em empresa aérea e passageiros podem desenvolver efeitos crônicos e/ou agudos de saúde e buscar atenção de provedores de serviços de saúde.
* bio-óleo [pyrolized oil]
Óleo convertido a partir de biomassa sólida para um bio-óleo líquido.
A produção de bio-óleo a partir de biomassa é baseada no processo rápido de pirólise, a qual é composta de cinco áreas maiores de processamento: secagem e manuseio de alimentação, pirólise, combustão de carvão, recuperação do produto e geração de vapor. A figura abaixo é um diagrama de bloco do fluxo de um processo rápido de pirólise.
Na seção de manuseio de alimentação, a biomassa é reduzida em tamanho para menos de 1 a 5 mm e secada para 5 a 10% de umidade. Ela é depois enviada para pirólise onde ela é aquecida para 400 a 500°C em uma atmosfera deficiente de Oxigênio para degradar a biomassa dentro de uma mistura de gases, bio-óleos e carvão. O carvão é removido usando ciclones de alta energia e é queimado para alimentar a reação de pirólise. Para maximizar o rendimento de bio-óleos, a reação é rapidamente  apagada através de intercâmbio de calor ou injeção direta de líquido (por exemplo: água, bio-óleos reciclados). Os bio-óleos estão presentes no vapor de gas como aerosóis e requerem esfregadores e/o precipitadores eletrostáticos molhados para captura eficiente. Após estarem limpos, alguns dos gases limpos da pirólise são reciclados para fluidizar o leito e os gases remanescentes são queimados pelo processo de aquecimento. Onde viável, calor é recuperado dos gases de pirólise para gerar vapor para produção de eletricidade.

Este documento fornece informação acerca de efeitos de saúde que podem resultar após exposição a contaminantes de ar de sangria de aeronave, e faz recomendações a respeito de métodos de tratamento. A informação neste documento é grandemente baseada em informação que foi publicada na literatura médica e científica, e também conta com experiência clínica de um dos autores (Robert Harrison, MD, MPH) que diagnosticou e tratou trabalhadores de empresa de linhas aéreas com exposição ao ar de sangria contaminado. Uma discussão mais detalhada sobre a toxidade de aditivos de óleo de tricressylphosphate do motor pode ser encontrada no Anexo 1. Para mais informação, links da web para fontes adicionais e referências detalhadas estão fornecidas no final do docmento.

Durante o voo, ar comprimido em alta temperatura é sangrado dos motores e, após ser resfriado, é fornecido para a cabine [de passageiros] e [de pilotos]. No solo, aviões de linhas aéreas frequentemente contam com um compressor menor localizado na cauda da aeronave chamado Unidade Auxiliar de Força (APU).

Bio-óleo do motor ou fluido hidraulico podem contaminar o ar nestes compressores como um resultado de falhas mecânicas, irregularidades de manutenção, e projetos defeituosos (ASHRAE, 2006; van Netten, 2000; BAe Systems 2000) (Tabela 1). O mais recente estudo deste assunto no Conselho Nacional de Pesquisa (NRC) concluiu que, sob certas condições de falhas, tais tóxicos como bio-óleos do motor e fluidos hidráulicos podem vazar para dentro da cabine da aeronave e para sistemas de suprimento de ar da cabine dos pilotos, e que estes tóxicos podem estar associados com efeitos de saúde (NRC, 2002). O relatório do NRC caracterizou a necessidade de definir a toxicidade destes contaminantes em voo e investigar a relação entre exposição e doença como uma alta prioridade.

Tabela 1. Mecanismo para Contaminação de Air de Sangria de Aeronave

Tipo de Falhas	Exemplo
Falhas Mecânicas	Selos de óleo que também separam o “lado molhado” do ar do compressor de ar, do “lado seco”, pode vazar ou falhar
Irregularidades de Manutenção	Trabalhadores podem  encher demais os reservatórios de óleo/fluido hidráulico ou espirrar óleo/fluido hidráulico quando abastecendo o reservatório
Projetos Defeituosos	Alguns selos de óleo podem ser menos efetivos, operações transientes e alta temperatura do motor, a tomada de entrada de suprimento de ar pode estar no fluxo de fluido hidráulico que goteja através das portas de alívio de resíduos e é carregada em direção a cauda da aeronave

Os agentes tóxicos em voo para os quais passageiros e tripulantes da aeronave podem ser expostos quando o ar de suprimento estiver contaminado com bio-óleo do motor/fluido hidráulico formam uma mistura complexa, incluindo de 1 a 5% de tricresylphosphates (TCPs) (adicionado aos óleos do motor da aeronave e pelo menos um fluido hidráulico) e N-phenil-L-naphthylamine (PAN) (Bobb, 2003). Se a temperatura do sistema de suprimento de ar estiver alta o suficiente, então bio-óleo/ fluido hidráulico pode também gerar monóxido de Carbono (CO) (van Netten, 2000).

Toxicidade de Esteres Organofosfatos

Tricresil Fosfatos (TCP)

Muitos organofosfatos exercem suas toxicidades agudas pela supressão da acetilcolinesterase, a qual pode causar falha respiratória devido paralisação neurosmucular.

Todavia, organosfosfatos tais como TCP são também capazes de induzir uma condição retardada de neuropatia neurodegenerativa conhecida como neuropatia organofosfato induzida retardada (OPIDN), a qual afeta ambos os nervos centrais e periferais de pássaros e mamíferos [9].

A relação entre a estrutura química de muitos fosfatos triaril puro e potêncialidade em causar OPIDN tem sido extensivamente estudada e as atividades relativas neurotóxicas destas substâncias são bem conhecidas. Tem sido reconhecido por pelo menos 40 anos que substituintes alcil nas posições orto dos anéis aromáticos são responsáveis pela atividade neurotóxica de TCP. Material sintetizado de somente m-cresol e p-cresol não causa OPIDN [4], mas a possibilidade de toxicidade crônica desta mistura isomérica não pode ser rejeitada.

De todos os 10 possíveis isômeros TCP, os isômeros mono-o-crescil são considerados os mais tóxicos; 10 vezes mais tóxicos que os isômeros tri-o-cresil e 2 vezes mais tóxicos que os isômeros di-o.
Portanto a toxicidade de TCP é relacionada com o conteúdo isômero o-cresil com os isômeros m- e p-cresil tendo baixa toxidade [10].

Ésteres Triacil Fosfatos

Fluidos hidráulicos de aviação são conhecidos por conter ésteres fosfatos como retardadores de fogo [11].
Eles incluem trifenil fosfato e triacil fosfatos [12]. Há critérios profissionais  Australianos de exposição (TWA) para trifenil fosfato (3 mg/m³) e tributil fosfato (2,2 mg/m³), mas não para tris(2-etilhexil) fosfato e triisobutil fosfato [13]. Triisobutil fosfato é considerado ser de baixa toxicidade, não mostrando sinais de neurotoxicidade em altos níveis de dosagem quando dado oralmente para frangos.
Todavia, ele está listado pela Comissão Alemã para Investigação de Riscos no Local de Trabalho (MAKKommission) como uma substância sensível à pele baseada em exposição da derme em coelhos [14, 15].

Embora, não tenha havido relatórios de sensibilidade à pele humana associados à fabricação e manuseio da substância [14]. Similarmente, tris(2-etilhexil) fosfato é considerado ser de baixa toxicidade e não sensível à pele [16]. É também usado como um plastificador [selante] retardante de fogo para fiação PVC automotiva [17].

Toxicidade de Aditivos Aminas

Como previamente relatado óleos de motores à jato em aeronave ADF contêm amina anti-oxidantes [18] e tem havido algumas considerações expressadas sobre os efeitos potenciais de saúde destas substâncias [1, 3]. Fenil-a-naftalamina (PAN) e a substância isomérica, N-fenil-b-naftalamina, tem sido encontradas por produzir um aumento na incidência de cânceres de pulmão e rins segundo administração subcutânea de ratos. Uma alta incidência de várias formas de câncer foi também encontrada entre trabalhadores expostos a óleo anti-ferrugem contendo PAN [19].

ENGLISH

MANAGEMENT OF EXPOSURE TO AIRCRAFT BLEED-AIR

CONTAMINANTS AMONG AIRLINE WORKERS

A GUIDE FOR HEALTH CARE PROVIDERS

Robert Harrison, MD, MPH¹
Judith Murawski, MSc, CIH²
Eileen McNeely, PhD³
Judie Guerriero, RN, MPH¹
Donald Milton, MD, DrPh<sup>4

1</sup>University of California, San Francisco
 ²Association of Flight Attendants
  ³Harvard School of Public Health
   ⁴University of Massachusetts Lowell

Funding for this project has been provided by the Federal Aviation Administration (FAA)
Office of Aerospace Medicine and is part of a collaborative project between the Occupational Health Research Consortium in Aviation (OHRCA) and the Airliner Cabin Environment research (ACER) Center of Excellence. Although the FAA Office of erospace Medicine has sponsored the project, it neither endorses nor rejects the findings of this research.

The outside air supplied to the cabin/flight deck on commercial aircraft ("bleed air") may
sometimes be contaminated with pyrolyzed engine oil and/or hydraulic fluid. As a result
of this contamination, airline workers and passengers may develop acute and/or chronic
health effects and seek attention from health care providers. This document provides
information about the health effects that may result after exposure to aircraft bleed air
contaminants, and makes recommendations regarding treatment methods. The
information in this document is largely based on information that has been published in
the medical and scientific literature, and also relies on the clinical experience of one of
the authors (Robert Harrison, MD, MPH) who has diagnosed and treated airline workers
with contaminated bleed air exposure. A more detailed discussion on the toxicity of
tricresylphosphate engine oil additives can be found in Attachment 1. For more
information, web links to additional resources and detailed references are provided at
the end of the document.

A EXPOSURE TO PYROLYZED ENGINE OILS AND HYDRAULIC FLUIDS

During flight, high-temperature compressed air is bled off the engines and, after being
cooled, is supplied to the cabin and flight deck. On the ground, airlines often rely on a
smaller compressor located in the aircraft tail called the auxiliary power unit (APU).
Pyrolyzed engine oil or hydraulic fluid may contaminate the air in these compressors as
a result of mechanical failures, maintenance irregularities, and faulty designs (ASHRAE,
2006; van Netten, 2000; BAe Systems 2000) (Table 1). The most recent National
Research Council (NRC) study of this subject concluded that, under certain failure
conditions, toxicants such as pyrolyzed engine oils and hydraulic fluids may leak into the
aircraft cabin and flight deck air supply systems, and that these toxicants may be
associated with health effects (NRC, 2002). The NRC report characterized the need to
define the toxicity of these airborne contaminants and investigate the relationship
between exposure and reported ill health as a high priority.

 

The airborne toxicants to which aircraft crewmembers and passengers may be exposed
when the air supply is contaminated with pyrolyzed engine oil/hydraulic fluid form a
complex mixture, including 1-5% tricresylphosphates (TCPs) (added to aircraft engine
oils and at least one hydraulic fluid) and N-phenyl-L-naphthylamine (PAN) (Bobb, 2003).
If the air supply system temperature is high enough, then the pyrolyzed engine
oil/hydraulic fluid may also generate carbon monoxide (CO) (van Netten, 2000).

Toxicity of Organophosphate Esters

Tricresyl Phosphates

Most organophosphates exert their acute toxicity by the suppression of acetylcholinesterase, which can cause respiratory failure due to neuromuscular block.

However, organophosphates such as TCP are also able to induce a delayed neurodegenerative condition known as organophosphate-induced delayed neuropathy
(OPIDN), which affects both the central and peripheral nerves of birds and mammals [9].

The relationship between the chemical structure of many pure triaryl phosphates and
potency in causing OPIDN has been extensively studied and the relative neurotoxic
activities of these compounds are well known. It has been recognised for at least forty years that alkyl substituents at the ortho positions of the aromatic rings are responsible for
the neurotoxic activity of TCP. Material synthesised from only m–cresol and p-cresol does not cause OPIDN [4] but the possibility of chronic toxicity of this isomeric mix cannot be dismissed.

Of all the 10 possible TCP isomers the mono-o-cresyl isomers are regarded as the most
toxic; 10 times more toxic than the tri-o-cresyl isomers and 2 times more toxic than the di-o isomers.

Hence the toxicity of TCP is related to the o-cresyl isomer content with the m- and p-cresyl isomers having low toxicity [10].

Trialkyl Phosphate Esters

Aviation hydraulic fluids are known to contain phosphate esters as fire retardants [11].
They include triphenyl phosphate and trialkyl phosphates [12]. There are Australian
occupational exposure standards (TWA) for triphenyl phosphate (3 mg/m3 ) and tributyl
phosphate (2.2 mg/m 3 ) but not for tris(2-ethylhexyl) phosphate and triisobutyl phosphate
[13]. Triisobutyl phosphate is considered to be of low toxicity, showing no signs of
neurotoxicity at high dose levels when given orally to chickens. Nevertheless, it is listed by
the German Commission for the Investigation of Hazards in the Workplace (MAKKommission)
as a skin sensitising substance based on dermal exposure to rabbits [14,15].

However, there have been no reports of human skin sensitisation associated with the
manufacture and handling of the compound [14]. Similarly, tris(2-ethylhexyl) phosphate is
considered to be of low toxicity and not skin sensitising [16]. It is also used as a fire
retardant plasticiser for automotive PVC wiring [17].

Toxicity of Amine Additives

As previously reported jet engine oils used in the ADF aircraft contain amine anti-oxidants
[18] and there has been some concern expressed over the potential health effects of these
compounds [1,3]. Phenyl-α-naphthylamine (PAN) and the isomeric compound, N-phenyl-
β-naphthylamine, have been found to produce an increase in the incidence of lung and
kidney cancers following subcutaneous administration to mice. A high incidence of
various forms of cancer was also found amongst workers exposed to antirust oil containing PAN [19].

Scrap from AVweb

REFERENCES
1. Senate Rural and Regional Affairs and Transport References Committee,(1999) Report “Air Safety and Cabin Air Quality in the BAe 146 Aircraft”.
2. House of Lords (UK), (2000) Select Committee on Science and Technology, Air Travel and Health.
3. Winder, C and Balouet, J-C. (2002) “The toxicity of commercial jet oils” Environ. Res. A, 89, 146-164.
4. Mackerer, C.R., Barth, M.L., Krueger, A.J., Chawla, B. and Roy, T.A., (1999)
“Comparison of Neurotoxic Effects and Potential Risks from Oral Administration or Ingestion of Tricresyl Phosphate and Jet Engine Oil containing TricresylPhosphate”, Journal of Toxicology and Environmental Health, Part A, 56, 293.
5. Singh, B. (2004) Institute of Aviation Medicine, Royal Australian Air Force, VMED 1856/1/3/1/MED Pt 1 (6).
6. Singh, B. (2004) Institute of Aviation Medicine, Royal Australian Air Force, Private Communications.
7. Kelso, A.G., Charlesworth, J.M. and McVea, G.G. (1988) “Contamination of Environmental Control Systems in Hercules Aircraft”, DSTO Report , MRL-R-1116.
8. SIMTARS (2002) “Smoke in F-111C & G Model Aircraft Cockpits, Preliminary Investigations”.
9. Fowler, M.J., Flaskos, J., McLean, W.G. and Hargreaves, A. J. (2001) “Effects of Neuropathic and Non-neuropathic Isomers of Tricresyl Phosphate and their Microsomal Activation on the Production of Axon-like Processes by Differentiating Mouse N2a Neuroblastoma Cells”, Journal of Neurochemistry, 76, (3), 671.
10. Henschler, D. (1958) “Die Trikresylphosphatvergiftung”, Klinische Wochenschrift, 36,
663.
11. US Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry (1977) “Toxicological Profile for Hydraulic Fluids.”
12. Healy C.E., Nair RS, Ribelin W.E. and Bechtel C.L. (1992) “Subchronic rat inhalation study with Skydrol 500B-4 fire-resistant hydraulic fluid.” Am Ind Hyg Assoc J. 53(3) 175-80.
13. National Occupational Health and Safety Commission http://www.worksafe.gov.au
DSTO-RR-030315
14. Berufsgenossenschaft der chemischen industrie, (2000) Toxicological Evaluation, No. 112 “Triisobutyl phosphate” CAS No 126-71-6.
15. Jenseit W., Bunke D., Rheinberger U., Kalberlah, Zerrin A. and Moll S. (2004) “Research, development statistical and analytical work to develop appropriate environmental indicators related to chemicals”, Interim report, July, Institute forApplied Ecology, Germany
16. van Esch G.J. (2000) Environmental Health Criteria 218 “Flame retardants: tris(2-butoxyethyl) phosphate, tris(2-ethylhexyl)phosphate and tetrakis(hydroxymethyl)phosphonium salts”, World Heath Organisation, Geneva.
17. Plasticisers Information Centre , www.plasticisers.org
18. Kibby J., Hanhela P.J., DeNola G and Mazurek W. (2005) “Analysis of Jet Engine Oils” DSTO Report DSTO-RR-0292.
19. Wang H-W., Wang D. and Dzeng R.W. (1984) “Carcinogenicity of N-phenyl-1 naphthylamine and N-phenyl-2-naphthylamine in rat.” Cancer Research 44 (7) 3098-3100.
20. Kristensen, S. “Mobil Jet Oil II – Overview of Available Scientific Background Information”. Submission No. 12 of Reference 1 (NICNAS).

REFERENCES
Hanhela, PJ; Kibby, J; DeNola, G; et al (2005) "Organophosphate and amine contamination of cockpit air on the Hawk, F-111, and Hercules C-130 aircraft" Australian Government Department of Defense, DSTO-RR-0303.

Henschler, D (1958) "Tricresyl phosphate poisoning. Experimental clarification of problems of etiology and pathogenesis" (Die Trikresylphosphatvergiftung Experimentelle Klarung von Problemen der Atiologie und Pathogenese) Klinische Wochenschrift, Vol. 26(14): 663-674.

Jamal, GA; Hansen, S; Julu, POO (2002) "Low level exposures to organophosphorus esters may cause neurotoxicity" Toxicol, 181-182: 23-33.

Mackerer, CR; Barth, ML; Krueger, AJ; et al (1999) "Comparison of neurotoxic effects and potential risks from oral administration and ingestion of tricresyl phosphate and jet engine containing tricresyl phosphate." J Tox Environ Health, Part A, 56: 293-328 NRC (2002) “The Airliner Cabin Environment and the Health of Passengers and Crew” Committee on Air Quality in Passenger Cabins of Commercial Aircraft. Board of Environmental Studies and Toxicology, Division of Earth and Life Sciences. US National Research Council, National Academy Press, Washington DC.

PCA (2000) "Air Safety and Cabin Air Quality in the BAe146 Aircraft." Parliament of the
Commonwealth of Australia, Prepared by the Senate Rural and Regional Affairs and
Transport Legislation Committee. Printed by the Senate Printing Unit, Department of the
Senate, Parliament House, Canberra, Australia.

SAE (1997) Aerospace Information Report 1539: "Environmental Control System Contamination." Rev. A. First issued Jan 1981; revised Oct 1997. Society of Automotive
Engineers International, Warrendale, PA.

SHK (2001) Board of Accident Investigation Report RL 2001: 41e "Incident onboard
aircraft SE-DRE during flight between Stockholm and Malmo, M country, Sweden, on 12
November 1999." Statens haverikommission, Stockholm, Sweden.

Singh, B (2004) “Inflight smoke and fumes” Aviation Safety Spotlight, 3:10-13.

Spengler, JS; Ludwig, S; Weker RA (2004) "Ozone exposures during trans-continental and trans-Pacific flights" Indoor Air (14 Suppl) 7:67-73.

van Netten, C and Leung, V (2001) “Hydraulic fluid and jet engine oil: pyrolysis and
aircraft air quality.” Arch Environ Health, Vol 56(2): 181-186

ATTACHMENT 1

TOXICITY OF TRICRESYLPHOSPHATE ENGINE OIL ADDITIVES

Tricreslyphosphates (TCPs) are added to most synthetic jet engine oils and at least one
hydraulic fluid1 primarily because of their anti-wear properties. According to a sample of
Material Safety Data Sheets of commonly used products2, the total concentration of TCPs varies between 1 and 5%.

The inhalation toxicity of pyrolyzed and aerosolized aircraft engine oil during commercial
airline flights is a subject that has received increasing attention over the past 10 years, not only in the US (NRC, 2002; SAE, 1997), but internationally (SHK, 2001; PCA, 2000).

The TCP additives are by no means the only toxic component of these oils, but it is important for HCPs to understand the inhalation toxicity of TCPs because it has been a
source of misunderstanding and debate. The levels or nature of airborne TCPs during an
air supply contamination event have not been characterized on commercial aircraft, although a recent study on military aircraft identified total TCP levels between 0.5 and 49
ug/m3 (Hanhela, 2005). Interestingly, TCP concentrations did not correlate with visible
smoke/fume or odor detection.

The three cresyl groups in a given molecule of TCP can attach to the phosphate in different configurations; these are called isomers. In total, there are ten TCP isomers
(Table 1), including a tri-ortho isomer (TOCP), two di-ortho isomers (DOCP), three mono-ortho isomers (MOCP), and four meta/para isomers. The relative amounts of these different isomers can vary between brands and batches of aviation engine oil, but
some combination of some or all of these isomers will be present in a given sample.

Although engine oil manufacturers consider the specific isomeric blend to be proprietary, it is known that the ortho isomers make up about 0.3% of the TCP and the vast majority
(99.97%) of the ortho isomers are MOCP and DOCP, while there is very little TOCP (PCA, 2000). Little is known about the relative amounts of the remaining meta and para
isomers.

Table 1: DESCRIPTION OF THE TEN ISOMERS OF TCP

Category of isomer Description of isomers

Tri-ortho: TOCP (1) o-o-o

Di-ortho: DOCP (2) o-o-m; o-o-p

Mono-ortho: MOCP (3) o-m-p; o-m-m; o-p-p

Meta and/or para (4) m-m-m; p-p-p; m-m-p; m-p-p

Probably because of some highly publicized TOCP mass poisonings resulting from adulteration of a popular alcoholic drink called "Ginger Jake" (1929) and a large batch of
cooking oil (1959), this single isomer has received the most attention, and it is the only
isomer for which an exposure limit exists (e.g., OSHA PEL: 0.1 mg/m3). These mass 1 Most engine oils used in the aviation industry do contain TCPs while most hydraulic fluids
contain tributylphosphates. One aviation engine oil that does not contain TCPs is Turbonycoil 600 manufactured by NYCO, SA. One hydraulic fluid that does contain TCPs is Chevron Hyjet
IV-A-plus (van Netten, 2001).

2 Referred to current Material Safety Data Sheets for Mobil Jet Oil II, Mobil Jet Oil 254, Mobil Jet Oil 291, BP/Exxon 2380, Royco 808, and Chevron Hyjet IV-A-plus. poisonings involving TOCP highlighted the risk of peripheral neuropathy and paralysis, which has been confirmed in laboratory studies involving animals that ingested TOCP or
absorbed it through their skin.

Peripheral neuropathy associated with dermal or oral TOCP exposure is of little relevance to the concerns raised over exposure to aerosolized engine oil on aircraft, in part because of the relative formulation and toxicity of the different TCP isomers in a given batch of engine oil. Specifically: (1) There is little, if any, TOCP in the engine oil
formulations; (2) The mono- and di-ortho isomers of TCP are five and ten times more toxic than TOCP, respectively, but are still only present at low concentrations such that
peripheral neuropathy should not be the primary endpoint of interest (PCA, 2000;

Mackerer, 1999; Henschler, 1958); (3) The ortho isomers have been implicated in chronic neurotoxicty in addition to peripheral neuropathy; and (4) The meta and para
isomers of TCP dominate commercial engine oil formulations and are not expected to cause peripheral neuropathy. However, evidence of potential for chronic symptoms of
neurotoxicity associated with acute exposures or chronic, low-level exposures has been
suggested for organophosphates in general (Jamal, 2002) and TCPs on the aircraft in particular (Singh, 2004). The ortho content of TCP has been successfully reduced in the last few decades but the toxicity of meta and para isomers are still of toxicological concern.

The majority of published research on the toxicity of engine oils has assessed symptoms of peripheral neuropathy among laboratory animals that either ingest the oil or absorb it
through their skin. However, aircraft occupants are primarily exposed via inhalation with
the potential for limited dermal exposure. There is no evidence that ground-based dermal/oral research data can be applied to inhalation exposures that are often incurred in a reduced oxygen environment. Inhalation toxicity testing in a controlled laboratory
setting, with post-mortem brain analysis of exposed animals may be necessary to confirm the observations of chronic neurotoxicity among exposed aircraft occupants.

STALL Update Procedure - Aerodynamic Review

Scrap from 17th Performance and Operations Conference in Dubai

Aerodynamic Review

STALL

•  A loss of speed can result in an aircraft reaching the stall AoA
•  BUT it remains an AoA issue

Stall is only an AoA problem [AoA = Angle of Attack]

• Low speed is a common contributing factor

AoA Control –Pitch control effect

The pitch control is a direct AoA command

• The elevators control DIRECTLY the AoA.
• A nose down command has an IMMEDIATE effect:

AoA Control –Thrust effect

• Aircraft with engines below the aircraft Center of Gravity
⇒ Thrust has a significant pitch effect

Stall Recovery

When Aircraft is stalled

•  FIRST: AoA MUST BE REDUCED
•  Release back pressure on stick or column
•  Nose down pitch input may be needed

 Note: Increasing thrust has an adverse effect on AoA reduction for Aircraft with engines below aircraft CG

•  SECOND: If speed needs to be recovered
•  When stall indications cease, increase thrust with care due to possible pitch up effect

  AoA comes first, speed  second

The change from approach to stall versus actual stall is not easy to determine, even for a specialist.

Approach to Stall versus Stall recovery procedure

• The classic recovery procedure associated with “Approach to stall” was characterized by a recovery focusing on:
-  Maximum thrust application
-  Minimum loss of altitude

• Whereas the recovery procedure from an “Actual stall” has always focused on:
-  AoA reduction as first action, followed by a speed recovery if needed

 Need for procedure change

• Drawbacks associated with this dual recovery approach are:
- TOGA application may lead to an increaseof the AoA
- Reluctance to apply nose down input
- Challenge to identify the change from “Approach to stall” to “Actual stall”

• Numerous accidents where the “Approach to Stall” recovery procedure
- was applied whereas the aircraft was actually stalled
- or generated a stall through thrust effect

A single procedure focusing on AoA reduction,           

• as a first action, required to cover both
• the “Approach to Stall” and the “Actual Stall” recovery:

It is called the “Stall Recovery” procedure

New Procedure

The FAA Stall Recovery Working Group issued a generic “Stall Recovery” procedure

•  A generic procedure for ALL types of aircraft
•  One single procedure to cover ALL stall conditions
•  Prevent full thrust/TOGA from being first action
•  Focus on AoA reduction

 Generic Stall Recovery Procedure

STALL WARNING OR AERODYNAMIC STALL RECOVERY PROCEDURE

Immediately do the following at the first indication of stall (buffet, stick shaker, stick pusher, or aural or visual indication) during any flight phases except at lift off.

1. Autopilot and autothrottle…………………………….…… Disconnect

Rationale: While maintaining the attitude of the aircraft, disconnect the autopilot and autothrottle. Ensure the pitch attitude does not change adversely when disconnecting the autopilot. This may be very important in mis-trim situations. Manual control is essential to recovery in all situations. Leaving one or the other connected may result in in-advertent changes or adjustments that may not be easily recognized or appropriate, especially during high workload situations.

2.
a) Nose down pitch control…Apply until out of stall (no longer have stall indications)

b) Nose down pitch trim…….………………………………………..As needed

Rationale:

a) The priority is reducing the angle of attack. There have been numerous situations where flight crews did not prioritize this and instead prioritized power and maintaining altitude. This will also address autopilot induced full back trim.

b) If the control column does not provide the needed response, stabilizer trim may be necessary. However, excessive use of trim can aggravate the condition, or may result in loss of control or in high structural loads.

3. Bank………………………….…………………………………….….Wings Level

Rationale: This orientates the lift vector for recovery.

4. Thrust ……………………………………………………………….. As Needed

Rationale: During a stall recovery, many times maximum power is not needed. When stalling, the thrust can be at idle or at high thrust, typically at high altitude. Therefore, the thrust is to be adjusted accordingly during the recovery. For engines installed below the wing, applying maximum thrust can create a strong nose up pitching moment, if speed is low. For aircraft with engines mounted above the wings, thrust application creates a helpful pitch down tendency. For propeller driven aircraft, thrust application energizes the air flow around the wing, assisting in stall recovery.

5. Speed Brakes…………………….………………………………………. Retract

Rationale: This will improve lift and stall margin.

6. Return to the desired flight path.

Rationale: Apply gentle action for recovery to avoid secondary stalls then return to desired flight path.

Conclusion

• Working together with other aircraft manufacturers, we have:
-  Agreed the principle with the FAA Stall Recovery Working Group
- Issued a harmonized procedure focusing on AoA
   reduction as a first action

When Stalls Most Often Occur
 
Circumstantial evidence shows that most full or near-full stalls of transport aircraft occur in one of five situations, as for other paths to loss of control, often but not always when the aircraft is either in IMC or during ‘dark night’ conditions clear of cloud so that no natural horizon is available:

• During inappropriate response to an un-commanded autopilot disconnect at high altitudes. (Uncommanded AP Disconnect due to malfunction of other systems)
• at low altitudes when the indicated airspeed is unintentionally allowed to deviate significantly from the intended and necessary target (Airspeed Awareness)
• at low altitudes in the presence of frozen deposits on the wings (Airframe Icing)
• during a mishandled go around (Aircraft management and Flying Skills)
• because of insufficient understanding of automation as it affects flight envelope protection systems.
• improper slats/flaps configuration (Aircraft Configuration)

Uncommanded AP Disconnect due to malfunction of other systems is not only liable to create a significant ‘startle factor’ for both pilots but is also likely to remove some of the high level flight envelope protections commonly provided by Fly-By-Wire (FRW) flight control systems. Flying manually at high altitude is not a feature of normal operations and there is not always sufficient awareness of the different ‘feel’ of the flight controls in the high altitude case compared to the routinely- experienced low altitude case. The simultaneous removal of some or all automated flight envelope protections at the same time, often because of an automatic reversion to a lower FBW Control Law, creates a heightened imperative to retain control within that envelope in a situation where a full understanding of the different degree of protection provided by Control Laws, other than "Normal", may not be fully understood or appropriately recalled.

Air France 447 - New Findings - Recommendations - Pilots' Talkings

AIRBUS 330 - Controles de Voo

Principio Básico

As superfícies de controle de voo do A330 são:

 - Eletricamente controladas
 - Hidraulicamente ativadas

O estabilizador e o leme/direção podem ser mecanicamente controlados.

Os sidesticks são usados para pilotar a aeronave com leme e direção.
Os comandos dos pilotos, são interpretados pelos computadores, os quais enviam sinais para mover os controles de voo necessários para realizar o curso de voo desejado.
Apesar do comando dos pilotos, os computadores previnem:
 - manobras excessivas
 - que os limites da segurança de voo sejam excedidos

In a schematic manner, the threshold is stable below a Mach of the order of 0.3, then reduces in a quasi-linear manner to a Mach of the order 0.75, after which it falls more rapidly when the Mach increases up to Mach 0.82.

Onboard weather radar

The Air France Airbus A330’s are fitted with Collins WXR 700X-623 type weather radar with a flat antenna (P/N : 622-5132-623). The opening angle of the radar beam is 3.6° in elevation and 3.7° in azimuth.

Adjustments to the tilt and the gain are made manually.

Each airplane is equipped with two systems, only one antenna and only one control box.

Only one system is active at a time.

The radar image is presented on the ND overlaid with navigation and TCAS information. It is presented when the radar is operating, when the ND is not in PLAN2 mode and when the TERR3 mode is not selected. Range adjustment is done manually

.

Note: Adjusting the luminosity of the terrain and weather information is done independently of that of other information on each ND.

No malfunctions of the weather radar were reported on the other ATL of F-GZCP in the last 6 months prior to the accident.

Instructions for use of weather radar

In cruise mode above 20,000 feet, a slight downwards adjustment of tilt, depending on the scale selected, is recommended so that the ground echoes only appear on the ND at the edge of the furthest distance circles. This method enables the simple and practical application of the height/tilt rule of equivalence providing the optimum tilt adjustment.
When pilots monitor the weather situation, gain can remain in CAL position. In the confirmed
presence of storms and during their avoidance, a manual adjustment can be used for comparison with the CAL image.
A scale of 160 NM enables the change in the weather situation to be assessed and anticipate route changes. A scale of 80 NM is used for avoidance. Short scales must be periodically discontinued in order to observe distant weather conditions and to avoid an impasse amid the disturbances.
The shape of the echoes may alert the crew to the possible presence of hail. Zones of turbulence may be presented above a detected zone of precipitation.
Red or magenta zones as well as fringe-shape echoes must in this way be by-passed from windward by regularly adjusting the tilt and the range. The avoidance decision must be taken before the echoes are at 40 NM.

The operator recommends avoiding flying less than 5,000 ft above or below a storm cell. It provides a formula for pilots to estimate the separation height between the top of a detected cell and the airplane. This formula uses the distance and the tilt points from which the zone echo disappears. Above 23,000 ft, it is recommended to fly more than 20 NM from these zones11.

Time (UTC)	Captain & PNF	1st Officer (PF)
22:10	Cleared to Start Up
22:29		Take Off  (TOW = 232.8) TakeOff Weight Max. TOW = 233 Ton. Including Fuel = 70.4 Ton
01:35:15		Crew Informed ATLANTICO controller the aircraft passed INTOL Fix point and they estimated SALPU at 01:48 then ORARO at 02:00 UTC.
01:35:46		Controller asked them to maintain Flight Level 350 and the estimated time at TASIL Fix point.
01:35:53 to 01:36:14		Controller asked again three times for the estimated at TASIL Fix with no answer.
01:55:00	He woke the second copilot and said:	“…he’s going to take my place”
01:59:32 to 02:01:46	He attended the briefing between the two copilots	“the little bit of turbulence that you just saw we should find the same ahead we`re in the cloud layer unfortunately we can’t climb much for the moment because the temperature is falling more slowly than forecast” “the logon with DAKAR failed”
	The airplane approached the ORARO point maintaining Flight Level 350, MAC 0.82, Pitch Altitude 2.5°, Weight & Balance 205 Ton and 29%. Autopilot 2 and Auto-Thrust engaged.
02:06:04		Called cabin crew: “in two minutes we should enter an area where it’ll move about a bit more than at the moment, you should watch out” He added: “I’ll call you back as soon as we’re out of it”
02:08:07	“you can maybe go a little to the left …”	The airplane changed the heading 12 degrees to the left. Turbulence level increased slightly and the speed was reduced to MACH 0.80.
02:10:05	The AUTOPILOT and   AUTO-THURST disengaged
		Pilot Flying said: “I have the controls”
	The airplane began to roll to the RIGHT and the Pilot Flying made a nose-up and LEFT input. The STALL WARNING sounded 2 times in a row. The recorded parameters show a sharp FALL from about 275 Knots to 60 Knots in the speed displayed on the LEFT PFD, and then a few moments later in the speed displayed on the Integrated Standby Instrument System [ISIS]. There is no record on the Flight Data Recorder about speed displayed on the RIGHT side.
02:10:16		“we`ve lost the speeds then” He added: “alternate law protections”
	The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane start climb.
		PF made nose-down control inputs and alternately LEFT and  RIGHT  roll inputs.
	The vertical speed reached 7000 feet/min, dropped to 700 feet/min and roll varied between 12° RIGHT and 10° LEFT. The speed displayed on the LEFT side increased sharply to 215 Knots (MACH 0.68). The airplane was at 37500 feet and the recorded AOA was around 4°.
02:10:50	PNF tried several times to call the Captain back
02:10:51	The STALL WARNING triggered again. The TRUST levers were positioned in the TO/GA detent
		The Pilot Flying maintained nose-up inputs
	AOA [Angle Of Attack] was around 6° continued to increase. The Trimmable Horizontal Stabilizer [THS] began a movement and passed from 3° to 13° pitch-up in about 1 minute and remained in the latter position until the end of flight.
50 seconds later	The speed displayed on the ISIS increased sharply towards 185 Knots.
		The Pilot Flying continued to make nose-up inputs
	The airplane’s altitude reached its maximum of about 38000 feet.  AOA and pitch attitude reached 16°.
02:11:45	The Captain re-entered the cockpit
	During the following seconds all of the recorded speeds became invalid and the STALL WARNING stopped.
	The altitude was then about 35000 feet, the AOA exceeded 40° and the Vertical Speed was about  minus 10000 feet/minute. The airplane’s pitch attitude did not exceed 15° and the engines’ N¹ were close to 100%. The airplane was subjected to roll oscillations that reached 40°.
		The Pilot Flying made input on the Side-stick to the LEFT and nose-up stops, wich lasted about 30 seconds.
02:12:02		PF said: “I have no more displays”
	PNF said: “we have no valid indications”
	The Thrust levers were on IDLE detent, at that moment, and the engines’ N¹ were at 55%.
50 seconds later	PF made pitch inputs.
	The AOA decreased, the speeds became VALID again and the STALL WARNING triggered again
02:13:32	PF said: “we’re going to arrive at level one hundred”
15 seconds later	Simultaneous inputs by both pilots on the side-sticks were recorded
		PF said: “go ahead you have the controls”
	AOA, while it was valid, always remained above 35°
02:14:28	The last recorded values were a Vertical Speed of minus 10912 feet/minute, a Gorund Speed of 170 Knots, Pitch Attitude of 16,2° nose-up, Roll Angle of 5.3° LEFT and a Magnetic Heading of 270°
	No EMERGENCY message was issued by the crew
	The wreckage was found at a depth of 3980 meters on 03 APR 2011 at about 6.5 Nautical Miles and to the North of the last position transmitted by the aircraft

The following tracks were recorded:

 track 1: radio communications and the signal from the microphones for the pilot seated on the left
 track 2: radio communications and the signal from the microphones for the pilot seated on the right
 track 3: radio communications, the signal from the second copilot’s microphone (rear seat), and the FSK signal
 a track made up from the first 3 tracks mixed together
 CAM track: the signal from the cabin area microphone

Analysis of the 5 audio files downloaded revealed that the event did not occur at the end of the sequence of data recorded on the 5 tracks, and that the tracks lasted for less than a few dozen seconds at the expected values.

Synchronisation of the various channels showed that some of the data was missing.
Moreover, analysis of the binary contents of the EEPROM memory confirmed the inconsistency of the pointers5 used by the manufacturer’s reader to start and end the downloading of the data.

Analysis of the flight recorder data

 Synchronisation of the recorders
The recorders were synchronised using the various alarms triggered during the flight, particularly the stall warning. The number of alarms made it possible to synchronise the recorders with an accuracy of approximately 100 ms.

The CVR recording started at about 0 h 09 UTC on 1 June.

 CVR analysis
The CVR audio recording starts at 00 h 09 min 15. The cockpit door was opened once at 0 h 26 min 19. It was later closed and opened again several times. It stayed opened for some time on several occasions. The door security system (electrical opening command by the pilots) was not heard on the overall recording.
At 0 h 36 min 26, an electrical phenomenon (audio discharge) linked to atmospheric conditions appeared on the CAM track and could be heard until the end of the recording. The following figure shows the distribution of those audio discharges as a function of time:

CONCLUSIONS

New Findings
 the composition of the crew was in accordance with the operator’s procedures,
 the airplane’s weight and balance were within operational limits,
 at the time of the autopilot disconnection, the Captain was taking a rest,
 the departure of the Captain was done without leaving any clear operational instructions, in particular on the role of each of the copilots,
 the crew had identified some echoes on the weather radar,
 the crew made a heading change of 12° to the left of its route,
 the AP disconnected while the airplane was flying at the upper limit of a slightly turbulent cloud layer,
 the copilots had not received any training, at high altitude, in the “Unreliable IAS” procedure and manual aircraft handling,
 there was an inconsistency between the speeds measured, likely following the blockage of the Pitot probes in an ice crystal environment,
 although having identified and called out the loss of the speed indications, neither of the two copilots called the procedure “Unreliable IAS”,
 the invalidity of the speed displayed on the left PFD lasted for 29 seconds, that of the speed on the ISIS for 54 seconds,
 in less than one minute after the autopilot disconnection, the airplane exited its flight envelope following inputs that were mainly pitch-up,
 the Captain came back into the cockpit about 1 min 30 after the autopilot disconnection,
 throughout the flight, the movements of the elevators and the THS were consistent with the pilot’s inputs,
 up to the exit from the flight envelope, the airplane’s longitudinal movements were consistent with the position of the flight control surfaces,
 there was no explicit task-sharing between the two copilots,
 there is no CRM training for a crew made up of two copilots in a situation with a relief Captain,
 no standard callouts were made on the disparities in pitch attitude and vertical speed,
 the airplane’s angle of attack is not directly displayed to the pilots,
 the approach to stall was characterised by the triggering of the warning then the appearance of buffet,
 neither of the pilots made any reference to the stall warning,
 neither of the pilots formally identified the stall situation,
 the stall warning was triggered continuously for 54 seconds,
 a short time after the triggering of the stall warning, the PF selected TO/GA thrust and made a nose-up input,
 the angle of attack is the parameter that allows the stall warning to triggered; if the angle of attack values become invalid, the warning stops,
 by design, when the measured speed values are lower than 60 kt, the 3 angle of attack values become invalid,
 each time that the stall warning triggered, the angle of attack exceeded the value of its theoretical trigger threshold,
 the engines functioned normally and always responded to the crew’s inputs,
 no announcement was made to the passengers.

Recommendations on Operations

Training for Manual Aircraft Handling

The investigation brought to light weaknesses in the two copilots: the inappropriate inputs by the PF on the flight controls at high altitude were not noted by the PNF through an absence of effective surveillance of the flight path. The stall warning and the buffeting were not identified either. This was probably due to a lack of specific training, although in accordance with regulatory requirements. Manual airplane handling cannot be improvised and requires precision and measured inputs on the flight controls. There are other possible situations leading to autopilot disconnection for which only specific and regular training can provide the skills necessary to ensure the safety of the flight. Examination of their last training records and check rides made it clear that the copilots had not been trained for manual airplane handling of approach to stall and stall recovery at high altitude.

Consequently, the BEA recommends:

 that EASA review the content of check and training programmes and make mandatory, in particular, the setting up of specific and regular exercises dedicated to manual aircraft handling of approach to stall and stall recovery, including at high altitude.

Relief Captain

The investigation showed that an absence of training and practice for a crew consisting of two copilots does not guarantee a level of performance equivalent to a crew consisting of a Captain and a copilot when faced with a degraded situation. The absence of a hierarchy and of effective task-sharing in the cockpit strongly contributed to the low level of synergy. The anxiety generated by the absence of the Captain from the cockpit shows that the two copilots were not capable of resolving this emergency situation. This can be explained both by the absence of any appropriate training and a lack of decision-making practice on the part of the two copilots. Numerous events turned out favourably due to the presence of the Captain whose training and experience made possible a more solid analysis and more serenereactions to the situation.

Recommendations relating to Certification

Angle of Attack Measurement

The crew never formally identified the stall situation. Information on angle of attack is not directly accessible to pilots. The angle of attack in cruise is close to the stall warning trigger angle of attack in a law other than normal law. Under these conditions, manual handling can bring the airplane to high angles of attack such as those encountered during the event. It is essential in order to ensure flight safety to reduce the angle of attack when a stall is imminent. Only a direct readout of the angle of attack could enable crews to rapidly identify the aerodynamic situation of the airplane and take the actions that may be required.

Consequently, the BEA recommends:

 that EASA and the FAA evaluate the relevance of requiring the presence of an angle of attack indicator directly accessible to pilots on board airplanes.

Recommendations relating to Flight Recorders

Analysis of the FDR parameters and audition of the CVR provide information that is essential to an understanding of the event. However, it is difficult to reconstruct the indications that were available to the crew on their instrument panel, especially the instructions given by the Flight Director crossbars when they reappear. It is also impossible to see whether there have been any attempts to re-engage the autopilot. A view of the instrument panel would complete the information provided by the FDR and the CVR and would make it possible to confirm the indications that were available to the crew and the actions that they made. Numerous recommendations have already been made on this subject over the past ten years without any real progress having been made.