Aerotoxic Syndrome

Firstly, my apologies for, perhaps, a lengthy ‘Blog’ this time. You will see why.

A question has winged its way over to me that set me back a little bit.

“Have you heard,” they asked, “about aerotoxic syndrome?”

The short answer to that is, “No. I have not.”

Sadly, easy questions tend to have difficult answers and so I need to go into a little detail here to sort this out for you.

The first thought was, ‘Is this another conspiracy theory that has been blown up out of all proportion?’

Some research seems in order here.

Sixteen years ago (1999) a group of chaps filed a report called ‘Aerotoxic Syndrome: Adverse health effects following exposure to jet oil mist during commercial flights’.

As a precursor to this, let us just review how the air gets into the cabin.

Ambient air—the air that surrounds the aeroplane in flight, is pushed into the engines because of forward speed. This is called ‘ram effect’. It is a good thing because the air is pre-pressurised before it gets to the compressor; it also makes the air ‘thicker’ for the fan to grip and push back.

Sorry

Once the air gets into the compressor the air pressure is raised some more to make it suitable for combustion where we shall add energy to the air by burning fuel in it.

Now back up just a little bit.

When the air is passing through the compressor there are off takes of air called ‘parasitic bleeds’ that are used for several functions on the engine and the flight computer and also a large amount goes off to the air conditioning unit(s) on the aeroplane.

This is the bit the air comes from

The amount of air passing from the air conditioning machine into the cabin is controlled. Too much bleed from the engine and fuel burn increases because we should need more ‘throttle’ to increase the airflow into the engine.

Remember that the primary need for air into the engine is for burning (for thrust) and for cooling the engine. Providing air for the passengers is, in reality, a necessary evil as far as the engines are concerned—remember the term ‘parasitic air bleeds’?

For this reason most of the air in the passenger cabin is re-circulated with only a percentage (about 50%) being replaced on a continuous basis.

How is it replaced? By making sure that the flow into the cabin is greater than the flow being released from the cabin. This will, in turn, raise the pressure of the air in the cabin to an acceptable level for human survival.

Sorry again

Survival? At 36,000’ there is not really sufficient air for a human being to survive. You would pass out in seconds and die in minutes from lack of air and cold.

So that is how the air gets there.

What about this ‘oil mist’ situation?

The oil that is used in jet engines is not dug out of the ground. It is synthetic. It is born in a factory. This is because mineral oil—oil that is dug out of the ground, is incapable of withstanding the temperature differences and pressures that exist in a turbine (jet) engine.

Note: When you see advertisements for engine oils for your car it will show you how great it is, in a CGI perhaps, at protecting the engine with the pistons going up and down and flames bursting around the cylinder.

Wonderful.

What is really needed is for the oil to protect your engine when it is not running; which is most of the time in your car. If the coating of oil runs off your car engine parts will rust. This is a bad thing.

Synthetic oil is thin to start with. When it gets hot it becomes even less viscous (it gets thinner). Keeping it where it is supposed to be is difficult.

Fortunately, those clever people at Rolls-Royce, for example, are very good at designing seals and sealing systems that will keep the oil where it is supposed to be.

But engines wear. Not much but over a period of time it can become significant.

To have an engine overhauled is expensive. Very expensive. We are talking in terms of millions of US dollars per engine.

Clearly the airlines will want to maximise the use of every engine before it gets sent back to the manufacturers, or an overhaul facility, for maintenance and servicing.

Because the air is tapped off from the compressor, the only sealing part of the engine that we need to worry about for the passengers is the bit at the front. This is called the ‘cold end’ of the engine.

The oil is re-circulated around the engine all the time while it is running. There are places where it gets really hot and the oil will partially break down. This is called a ‘pyrolised’ condition—a chemical alteration in the oil. The toxicity appears to be confined to the additives in the oil and the decomposition of the oil itself.

One of the primary checks the maintenance staff carry out every time the aeroplane is on the ground is to make sure there is no oil leak from the front of the engine—the nose cone and the fan cowl.

If oil is seen here then the engine comes off. No discussion necessary.

What is the likelihood of oil coming from the engine into the cabin? About 1% of the time. The possibility of the oil becoming hazardous is considerably less because stringent checks are carried out between each flight to prevent this from happening.

How do we know if there is a fume hazard in the cabin? Only the crew’s capacity to detect it is available at present. There are no detectors installed that might spot it—or other contaminants in the air.

Perhaps there is another cause for this aerotoxic condition that has not been looked at?

When the aircraft is at 36,000’ the air, in theory, should be relatively clear although certain gases are found at high altitude as a result of pollution. It is likely that these gases are a very small percentage of the total and so it is better to look at the flight envelope through the lower altitudes where industrial pollution is to be much higher.

Climbing out of, or entering, the Beijing area, for example, is likely to introduce toxic chemicals into the cabin because the incidence of industrial pollutants is much higher than in many other places. Beijing is not alone in having a pollutant rich air zone.

What are the symptoms?

            Fatigue – feeling exhausted, even after sleep

            Blurred or tunnel vision

            Shaking and tremors

            Loss of balance and vertigo

            Seizures

            Loss of consciousness

            Memory impairment

            Headache

            Tinnitus

            Light-headedness, dizziness

            Confusion / cognitive problems

            Feeling intoxicated

            Nausea

            Diarrhoea

            Vomiting

            Coughs

            Breathing difficulties (shortness of breath)

            Tightness in chest

            Respiratory failure requiring oxygen

            Increased heart rate and palpitations

    Irritation of eyes, nose and upper airways.

Can we cure it? Given rest and recuperation time your body should recover but repeated flights under these conditions can lead to considerable neurological stress that may become chronic.

Are all aircraft susceptible to engine oil bleeding into the compressor? Early BAe 146’s and Boeing 757’s are poor but the new Boeing 787 is exempt because the cabin air systems do not get their air from the engines. It has a separate electrically driven system for air conditioning and pressurisation.

“Should I worry?” you might ask.

According to the CAA (Civil Aviation Authority) in the UK there are about 30 pilots grounded by the CAA’s Medical Department because of a ‘suggested association between illnesses and the cabin environment’.

But remember that these are people who are sitting in this environment all their professional lives.

Passengers will consume far less time in the air and thus the risk is proportionately smaller.

There is no point in wearing a mask, it will not help. Even the ‘drop-down masks’ on the aeroplane will not help. The only answer is to get off.

At 36,000’ that could be a problem!

B-24 Liberator

I understand that this is not 'Jet engines' but, to an aviation person it is still interesting.

This is the forerunner of how this is mostly done today but with a greater emphasis on safety.

Watch and enjoy, then sit back and wonder at how this was achieved in 1941.

This was 6 months BEFORE Pearl Harbor! Henry Ford was

determined that he could mass produce bombers just as he

had done with cars, so he built the Willow Run assembly

plant in Michigan and proved it. It was the world's largest

building under one roof at the time.

This film will absolutely blow you away - one B-24 every 55 

minutes, and Ford had their own pilots to test them!!

ADOLF HITLER HAD NO IDEA THE U.S. WAS CAPABLE

OF THIS KIND OF THING.

https://www.youtube.com/embed/iKlt6rNciTo?rel=0

MH370: July 2015

And so we move along. Slowly, it is true, but move on is what we do.

It seems that wreckage from an aeroplane has been discovered on the island of Reunion, a small island between the small island of Mauritius and the bigger island of Madagascar – or Malagasy Republic (whatever they choose to call it now!).

Along with the piece of aeroplane, it has been reported and photographed, there has also been found the wreckage of an anonymous piece of luggage that could have come from anywhere.

We may safely ignore the luggage even if it is emotionally rewarding to associate it with the loss of an aeroplane.

The part that is potentially worth looking at is the piece of the aircraft. This is something whose identity can be established.

Firstly, what is it?

That is simple enough. It is a ‘flaperon’. What, you may ask, is a ‘flaperon’. 

This is a small piece of the trailing edge of the mainplane, usually towards the inner portion of the wing. A flaperon is a type of aircraft control surface that combines aspects of both flaps and ailerons. In addition to controlling the roll or bank of an aircraft, as do conventional ailerons, both flaperons can be lowered together to function similarly to a dedicated set of flaps.

flightclub.jalopnik.com

As you will observe from the photographs, the part that has been found is quite large and quite substantial.

The Guardian

zenithair.com

Where has it come from?

The type and size match that fitted to a Boeing 777. It has yet to be confirmed that this is the case but it looks fairly certain that it is from that particular type of aircraft.

Point of fact: there have been no other Boeing 777’s lost in this area than MH370

If it is definitely proven that this flaperon came from a B-777 then, inevitably, the result must be that this is part of MH370.

Sad.

Why so far from the search site?

Ocean currents are strong and relatively fast. The aircraft went missing over a year ago. That this part showed up at all is miraculous and shows that there must have been, at least, some air inside it to keep it buoyant enough to float so far. It has floated for some time because there are barnacles on it.

Is it feasible that this part could have come from the search area?

Absolutely.

i.guim.co.uk

This illustration shows how far pieces could reasonably be expected to go given (statistically normal) condition in the southern reaches of the Indian Ocean.

http://edition.cnn.com/2015/07/30/world/mh370-debris-investigation/

What should we learn from this?

Well, we should learn that waiting for the results of an investigation is always a good plan. Rearing up and prancing around with a conspiracy theory, no matter how exciting it is, is always counterproductive.

As I have mentioned previously, in another ‘Blog’, it is inevitable that as soon as an aircraft crashes under mysterious circumstances everyone suddenly becomes an aviation expert. Conspiracy theories are always more attractive than truth.

Do we know what happened now?

No. We do not. But we are a step closer. 

One step at a time; step slowly, step positively; step carefully.

It may not be exciting but it is more satisfying to know the truth.

Aviation Experts!

Some time ago during the sad – and ongoing, situation with MH370 I mentioned that the World fills with aviation experts.

For some inexplicable reason everyone suddenly has an important facet that they feel should be introduced into the search or investigation.

These ideas range from the most fanciful conspiracy theory to the more down to earth and considered thoughts.

None of these conjectural inputs, as I said at the time, are helpful.

The only thing that matters here is that “we do not know”. The full stop (or ‘period’ as our transatlantic friends would have it) marks the point at which we cease to converse.

No more should be said until we have more knowledge; more facts.

There are still no more facts than we had before in that instance.

So we move on to Flight QZ8501.

It has started again.

I did mention that conspiracy theories arose on day one but now we have inputs from people who should know better.

Let me quote from a source that a few people regard as being a ‘news’ paper (‘The Guardian’, it said on the top of the web page):

“Weather was the “triggering factor” in the crash of AirAsia flight QZ8501 with icing likely causing engine damage, Indonesia’s meteorological agency said on Sunday, as bad weather continued to hinder rescue efforts.”

And:

“The most probable weather phenomenon was icing which can cause engine damage due to a cooling process. This is just one of the possibilities that occurred based on the analysis of existing meteorological data.”

‘Cooling process’? Suddenly the meteorological office is a source of expertise on thermodynamics and the operation of the Brayton cycle (jet engine – for those who are not aviation people).

The problem, let me set you straight, with icing is twofold.

1.            The formation of ice on the rime of the airframe intake and the first stage fan blades may create problems when it breaks off and goes down the intake duct.

2.            Icing on the airframe intake rim may cause a disruption of the airflow into the engine. A smooth airflow is necessary for the efficient operation of the compressor. Turbulence can cause surge that can seriously damage the compressor components.

In the first instance one would imagine that these pilots, who were experienced fellows, would have selected anti-icing to ‘ON’ before entering inclement conditions.

This would preclude ice forming on the airframe intake.

Ice formation on the fan blades will, on most high by-pass engines, pass down the cold air duct if it breaks off. That said, ice formation on the fan blades is a fairly remote possibility considering the angular velocity of any section of the blades.

The engine choices for the A320-200 are the CFM56 and IAE (International Aero Engines V2500).

[Note: The Pratt & Whitney PW6000 engine choice is available only on the A318 variant.]

Both the CFM and the IAE engines have been around for a considerable time. Both are renowned for reliability – as they must be for aircraft that can be certified for ETOPS (Extended-range Twin-engine Operational Performance Standards).

Happily the Meteorological Office seems to know better. How fortunate we are to have their insight and recommendations.

Remember what we said about that ‘full stop’?

Reviews

Just as a passing note: thank you to Benjamin Yee of Maryland, USA, for the wonderful review he submitted to ‘Amazon.com’ for “A Simple Guide to Understanding Jet Engines”.

Let me emphasise that I have no idea who Benjamin is other than the fact that he is a person of taste and discernment.

Why am I grateful?

Because all authors benefit from reviews. Sometimes the review is unfavourable as was one I had for a science fiction story I wrote.

But the criticism contained within the review was most helpful because it was constructive.

There is no doubt that whatever you write, or create, it will not be received with open arms by everyone.

Somebody will not like what you do. That is their prerogative. It is also their right to tell you why they were disappointed with it.

It is also encouraging that the person took the time to write the review. Positive or negative though it might be they sat down and put their thoughts about your creation on to the website.

For that alone, I thank you – who ever you may be.

Whether you are writing course or lesson notes; short stories; novels or textbooks the effort required is considerable. The words just do not pour out automatically – at least, they do not for me!

So appreciation from others is warmly received.

Thank you.

As a final note about ‘ASGTUJE’ (as we call it here in my house!) it was not written with the idea of making millions. The idea was to make the subject clear and simple. Even those who do not have English as a first language will be able to understand. For all readers, the objective remains the same – “K.I.S.S.” = Keep It Simple & Straightforward.

The endeavour with this ‘Jet Engine’ book was to explain the subject up to the level required (IATA Level 3) for license examinations without inundating the reader with complex equations and theorems.

And it has cartoons. Cartoons? In a textbook? Perish the thought! It has humour here and there, too. How heretical is that? After this you can ‘go on’ to the Rolls-Royce book of the jet engine, or Klaus Hünecke’s book, more confidently.

We hope that you all enjoy it. Not just pilots and engineers but also enthusiasts and hobbyists, too. It may even be useful for youngsters doing physics as there is a lot of basic knowledge covered in the early chapters that could be thought of as ‘Applied Physics’!

Thank you, again, for your reviews – for anyone’s story or book.

ASGTUJE

Think about the new term coming up.

Why the 'new term'? Because the basics of jet engines is the basics of applied physics. If you are doing science at school this may help you understand what the teacher is saying in a non-academic manner.

If you are in aviation this could be very useful to you.

Why? Because if you are an 'old salt' it will be a refresher and, at least, amusing.
If you are new it will help you learn and pass the Gas Turbine module for licensing (it is written to EASA Level 3 especially for trainee Engineers and pilots at Ground School)

If you are an aviation enthusiast it will help you to know what pushes aeroplanes through the air and tickle your funny bone at the same time.

If you are just curious about jets it is the best introduction you can get.

It does what it says on the tin - it is simple, straightforward and humorous. Black and white, no complications.

QZ8501

Sadly the news has been grievous.

QZ8501 has been found – or parts of it, floating around the Java Sea.

Bodies have also been discovered and the recovery of those bodies and the delivery of them to Surabaya has begun. That will, inevitably, be a slow process.

Naturally enough the cause of the crash has yet to be determined. It will be a while before the ‘black boxes’ are found and their contents analysed.

At least, unlike MH370, some closure is available for the relatives in that the immediate knowledge has been confirmed as a fatal hull loss.

Our deepest condolences go out to the family and friends of those who perished in this tragedy.

Air Asia was the subject of an incident in the Philippines when another A320-200 flying from Manila to Kalibo overshot the runway.

It was said that the weather had been very bad and that the pilot had brought the aircraft in under very windy conditions.

Happily, there was no loss of life (hence it was an ‘incident’ and not an ‘accident’) as all the passengers successfully evacuated the aircraft using the emergency procedures.

This particular A320 is owned by Air Asia ‘Zest’. This is a domestic Philippines airline that is partly owned by Air Asia.

Just to put this into some sort of perspective, runway overruns are fairly common; it is not something we should be getting excited about.

Right now we should be concentrating on MH370 and QZ8501 and waiting patiently for information.