Causal Factors of the Piper Malibu Crash near Guernsey

3 Dec 21 15 Comments

Sometimes it seems like these posts get longer every year that I keep doing this. This collection of details from the AAIB report that I left out of the Piper Malibu crash near Guernsey is almost as long as the original post. But there are a number of aspects that are interesting to look at in more detail. I’m afraid this post won’t make much sense without having read the previous one but I promise the rest of the posts this year will be stand-alone, succinct and to the point (a promise I only ever dare make in December).

Propeller and Engine

Unfortunately, as you can see from the comments last week, it is simply impossible to know what was actually wrong with the plane.

The pilot reported four separate issues that weekend:

  • A bang accompanied by a low mist
  • Loss of pressure in the left brake
  • Spurious stall warning that continued during taxi
  • Engine oil leak

I should clarify that last week I wrote “low-level mist” but looking again, the pilot said “low mist” not low-level. The left brake was looked into on the Monday and the engine oil leak was dismissed as not an issue. The pilot dealt with the stall warning by pulling the circuit breaker as they taxied to parking at Nantes. He never mentioned the issue again so it isn’t clear if resetting the circuit breaker fixed the issue or if he left the stall warner disabled. As the final manoeuvres didn’t include a stall, it wouldn’t have made much difference anyway. That leaves us with the bang and the mist.

The AAIB could not come up with a clear answer as to what might have caused the sound which startled the pilot, let alone the low mist. This is partially because the pilot wasn’t consistent in his descriptions.

After he arrived, he said that he’d heard a loud bang accompanied by a low mist halfway across the channel. However, when he spoke to the mechanic about it the following day, he described it as a thud and said that it had happened on the approach to Nantes, with no reference to the mist. Initially, he said he’d experienced the low mist before; however there was no record of this in the journey log and no one else who flew the plane reported having experienced this.

To notice a “low mist”, the pilot would have had to either look down into the footwell or back into the cabin. With temperatures at freezing outside, the cabin heat control would have been open to keep the cabin warm, including conditioned ram air blowing out of the foot warmers onto the pilot’s feet. One theory is that he never saw a mist but rather that he felt a coldness around his feet as the temperature of the heated air briefly dropped.

The investigation focused instead on the possibilities for the loud bang. No evidence was found of a bird strike or a mechanical failure of the engine. His description didn’t match a change of the undercarriage setting. If the exhaust system had failed and the mist was actually smoke, then the issue would have continued for the rest of the flight to Nantes. A cabin pressurisation issue is possible but the pilot never mentioned using the cabin pressure or losing it. The wreckage is such that it isn’t possible to know if the cabin was pressurised for the return journey, let alone verify whether it had failed on the outbound flight.

It could not have been a failure of a turbocharger turbine as the engine was operating normally on the ground at Nantes; however, an interesting possibility is that one of the turbochargers had become detached. If that were the case, then some of the exhaust gas would pass through the common duct and into the turbine section of the turbocharger, with the result that the engine wouldn’t function at maximum capacity in terms of boost and rpm. But the pilot may well have felt that the engine was still running normally and not considered that there there was an ongoing issue.

As he never reported finding any issues (for example, did the cabin pressurisation still work or whether he reset the circuit breaker for the stall warning), it is very difficult to work out what went wrong.

I wrote briefly about the engine in the accident aircraft: a Teledyne Continental TSIO-520-BE engine: fuel-injected, twin-turbocharged, air-cooled, horizontally-opposed, six-cylinder engine. The turbochargers, a combination turbine and air compressor, take in air at higher pressures which means they can burn more fuel and produce more power than a regular engine. The engine oil is cooled by ram air, external air which is “rammed” into the engine through a forward-facing inlet, so that as the airspeed increases, the ram air pressure is increased. Both turbochargers were replaced in 2017.

There was no technical log on the aircraft and, as an aircraft for private use only, there was no requirement to have one. The aircraft had a journey log which recorded the destinations and hours flown. The person who managed the operation of the aircraft said that he did not know of any faults on the aircraft other than those that the pilot reported after arriving in Nantes.

Piston engines produce high concentrations of carbon monoxide. Carbon monoxide is a serious hazard because it is an odourless gas which can quickly overwhelm the occupants, which is why some system of carbon monoxide detection is important to safe flight.

If the exhaust system has cracks, poor seals or poorly fitted components, the carbon monoxide can enter the cabin. Common failures of the exhaust system are caused by engine vibrations, thermal cycling, high temperatures and the corrosive effect of engine exhaust gases.

In 2004, the NTSB recommended that the FAA require the installation of carbon monoxide detectors in single-engine aircraft at risk of carbon monoxide entering the cockpit. However, the FAA does not require a detector but simply recommends that owners and operators use one. There is no rule that owners or operators install a carbon monoxide detector; instead, the FAA relies on education regarding the use of these and the importance of properly inspecting and maintaining the exhaust systems.

Similarly, the CAA argues that the potential for carbon monoxide poisoning in small aircraft is dealt with through regulation of the design, maintenance and operation. The CAA promotes the use of a current carbon monoxide detector but it is not mandatory.

A common inexpensive method of detecting carbon monoxide levels in the cabin of the aircraft is a CO strip detector or spot detector. They can be mounted onto a card and stuck to a highly visible location, with the strip turning black in the presence of carbon monoxide. A strip detector lasts between 3 and 18 months after being removed from their packaging.

The person who managed the aircraft believed that there was a strip detector fitted to the right side of the instrument panel, although it wasn’t fitted by him.

The various maintenance organisations who had done the annual maintenance in 2016, 2017 and 2018 had no record of installing a CO detector. There was no record of the Malibu ever having a CO detector installed.

AAIB: Right tailpipe and heater assembly removed from a PA-46-310P aircraft

The exhaust system on the aircraft consisted of right and left exhaust tailpipes made of stainless steel. Exhaust gas on the sides of the engine is directed through a wastegate on the left tailpipe. The wastegate directs excess exhaust gas away from the turbines.

The maintenance schedule for the aircraft included an inspection of the exhaust but did not require the tailpipe/heater muff to be removed or the exhaust system to be pressurised to check for leaks. The manual included the warning (in the introduction and repeated in the section on scheduled maintenance) that the vendor publications must be consulted when inspecting vendor equipment.

AAIB: Ram air shroud removed from exhaust tailpipe / heater muff
from a PA-46-310P tailpipe

Continental Motors was the vendor for the engine fitted to the PA-46-310P. The engine manual had instructions and guidance for the continued airworthiness of the engine.

The guidance recommended that the exhaust system be pressure tested by applying air at a pressure of 5 psi to the exhaust tailpipe, using soapy water to check for leaks.

A service bulletin for the visual examination of the exhaust system and pressure-testing the exhaust system had been incorporated into the Standard Practice Manual for the engine.

Here’s the key point: If the aircraft were following Part 135 maintenance in order to be used for commercial flights, then this service bulletin would have been mandatory. Every year, a pressure test of the exhaust system would have been a requirement as a part of the examination of the exhaust system. For Part 91 (private flights), the requirements are much less strict. There was no requirement to pressure test the exhaust system to look for leaks and in the case of the accident aircraft, only a visual examination was made.

The year before, the aircraft’s annual maintenance was done by a different maintenance organisation. They carried out a detailed visual inspection of the exhaust system. Both maintenance organisations believed that the visual inspection of the exhaust system was sufficient to establish its condition and that there was no need for the exhaust system to be pressure tested.

This takes us to the heart of the issue. Grey charters, unlicensed commercial flights, are illegal but the regulations are very hard to enforce. It is up to the aviation authority to spot the flight and gather specific evidence that the pilot or broker was paid. Those using these grey charters are unlikely to understand the risk or even to be aware that the operation is illegal, let alone whether the aircraft is licensed and insured.

In the UK, a private pilot can operate a flight on a “cost-sharing” basis. This is a private arrangement which means that everyone on board shares the cost of the flight. The pilot must also pay his share and only direct costs can be shared, basically fuel and fees for landing or handling. In addition, a passenger in a cost-sharing flight must deal directly with the pilot; there can be no intermediaries.

However, if you are paying for the flight, then the operator of the aircraft must hold an Air Operator’s Certificate (AOC). The operator, whether that is a pilot or an organisation or an airline company, needs to meet a number of regulatory requirements to do with public safety and insurance. AOC holders are regularly inspected and audited.

The football agent who booked the flight on behalf of the customer probably had no idea of the regulatory issues. It wasn’t possible to get a direct scheduled flight from Cardiff to Nantes, so he contacted a man whom he knew was an experienced pilot; who had flown him and many of his players all over Europe on countless occasions. It didn’t occur to him that the man was running an illegal air taxi service or that he should ask if the pilot’s operation held an air operator’s certificate.

An air operator’s certificate would show that the operation followed much stricter safety standards. The company would have been required to follow more operational and engineering procedures. The pilots must be more highly qualified and their competence is tested more frequently. A pilot flying for an airline is assessed every six months, either in the air or in a simulator. To compare, a pilot with a private pilot’s licence generally only needs to renew their flying ratings every 24 months.

But who, in this case, was the operator? I have to be careful here because there is a lot of reading between the lines and the court case only actually covers the one flight, from Nantes to Cardiff, even though there is evidence of many other flights which were paid for by the passengers.

The flight was organised by a man who appeared to be generally operating the Malibu on behalf of the owner: an ex RAF officer who had hired a number of pilots in what was described in court as a “cowboy outfit” which did not follow regulations and ran undocumented operations. This appears to be the same person who is described as “responsible for the operation of the aircraft” in the report. He did not have an AOC and had never applied for one. He has since been convicted of endangering the safety of an aircraft and of arranging a flight for a passenger without permission or authorisation.

This man spoke to the football agent and then contacted the pilot to ask him to do the flights that weekend, as he was away on holiday. The pilot was clear that he would be paid for this, and in fact had been paid for similar flights on behalf of the operator in the past. The pilot agreed to fly the two daytime flights: Cardiff to Nantes on Saturday and returning from Nantes to Cardiff on Monday morning.

A representative of the trust, the owner of the aircraft, says that she told him that the pilot was not to fly the plane any more, after she received two letters from the CAA regarding airspace infringements. However, she is not on record as explaining whether she knew her aircraft was being used for illegal charter operations.

The man convicted, who initially denied being the operator, clearly understood the situation. He wrote an email to the pilot in which he made it clear that they needed to avoid CAA interference:

I have always said the flying we do is challenging and everyone has to be on the ball. It is a steep learning curve for someone new to the operation.

The prerequisite is a willingness to listen and learn. We both have an opportunity to make money out of the business model but not if we upset clients or draw the attention of the CAA… As self-employed sole traders we both have debtors and creditors and surely you understand that to remain legal we can’t take money in advance.

Radar track of final section of flight

After the news broke that the aircraft had crashed, he messaged multiple people asking them to stay silent and said that the crash would “open a can of worms.”

[The pilot] has crashed the Malibu and killed himself and VIP pax! Bloody disaster. There will be an enquiry.

On the 15th of October last year, the director of the CAA announced that they were prosecuting the man for the following charges:

  1. On the 18th and 19th of January 2019, acted in a reckless/negligent manner likely to endanger N264DB (Articles 240, 256 and Part 4 of Schedule 13 of the Air Navigation Order 2016);

  2. On the 21st of January 2019, attempted to cause N264DB to discharge a passenger in the UK (Section 1(1) of the Criminal Attempts Act 1981, Articles 250, 256 and Part 3 of Schedule 13 of the Air Navigation Order 2016).

Just over a year later, the case is concluded and the man, who eventually conceded that he acted as an operator for that flight, was sentenced by the Cardiff Crown Court to eighteen months in prison. As a part of the court case, it was shown that the pilot had regularly flown for the operator and had clearly understood that he would be paid for this flight. Obviously, this operation, whatever the scale of it, was illegal, immoral and disregarding regulations that are put into place for the safety of the flying public.

It seems clear that the aircraft flew into the bad weather. Other pilots experienced little or no ice at the levels of the Piper Malibu that night but their reports and the radar show that there were intermittent heavy showers directly on the flight path. In addition to this, the layers of cloud obscured the moonlight and most likely the lights below, at least in the distance. The autopilot was known to be faulty and could have disconnected. This feels like a recipe for disaster: a pilot with no night rating and very little instrument experience was flying in instrument conditions in the dark with no visual references. It is no surprise that a pilot could lose control under these circumstances and plunge into the sea.

However, I don’t feel at all confident that the pilot’s skill level was the cause of that crash.

The pilot’s body was never found and we cannot know the medical state he was in before the crash. But the passenger was clearly suffering from extreme carbon monoxide poisoning with a carboxyhaemoglobin (COHb) level of 58%. Normally, COHb levels are 1-2% with smokers reaching up to 5%. Anything over 9% is considered to be from significant exposure to carbon monoxide from an outside source. The most common reason for elevated COHb levels is breathing air polluted with high carbon monoxide content. Carbon monoxide is believed to be the cause of over half of all fatal poisonings around the world. Common sources of carbon monoxide causing poisoning are fires, motor-vehicle exhaust and faulty domestic heating systems.

The most common symptoms of carbon monoxide poisoning are headache, dizziness and confusion, starting at 30% COHb. From 40-50% the passenger would have suffered from extreme headache, confusion and fainting. At 58%, he would have been unconscious with convulsions, respiratory failure and death to follow if the exposure continued.

In the Piper Malibu, there is no way that the pilot was protected from the contaminated air that the passenger was breathing. The truth is, with no evidence that he was suffering from carbon monoxide poisoning, it was only a matter of time before he, too, fell unconscious.

His voice sounded normal when he asked for an additional descent and when he explained that he was avoiding weather. But confusion and lack of judgement could easily take effect before any slurring of words.

The causal factors are listed as

    1. The pilot lost control of the aircraft during a manually-flown turn, which was probably initiated to remain in or regain VMC.
    2. The aircraft subsequently suffered an in-flight break-up while manoeuvring at an airspeed significantly in excess of its design manoeuvring speed.
    3. The pilot was probably affected by CO poisoning.

Whatever happened that night as they crossed the English Channel, the pilot’s chance of survival was minimal. It didn’t matter that the pilot was struggling to maintain VMC. It didn’t matter that he lost control. It didn’t matter that he pulled up hard while the aircraft was diving.

If that flight had progressed with no issue, the fumes would have continued to affect the pilot, having already knocked out a young and very healthy footballer in his prime. The pilot would not have been competent to land the aircraft at Cardiff if, by some miracle, he was even still conscious.

The question as to whether the pilot was competent to fly in this weather is actually somewhat irrelevant. As the aircraft had no CO detector, there was no way for the pilot to know that the cockpit and cabin was filling with carbon monoxide.

There is no requirement for an aircraft to carry a CO detector, regardless of whether it was flying under Part 91 (private use) or Part 135 (commercial flights). The AAIB makes the point that passengers, pilots under training and individuals on cost-sharing flights are unlikely to understand the risk of carbon monoxide poisoning or that the pilot can choose not to have a CO detector installed. As a result, they recommend that the FAA, the CAA and EASA all require piston engine aircraft which may have a risk of carbon monoxide poisoning to have a CO detector with an active warning.

When I look at the factors of this accident, two issues jump out at me. The first is that, if the aircraft had been operating legally as a commercial flight, it would have been mandatory for the heater muff to have been pressure-tested which may have alerted maintenance that there was a carbon monoxide leak. But more importantly, a CO detector in the cockpit is the one thing that I can see that could have completely changed the course of events. In my opinion, the lack of a CO detector and the lack of a requirement for a CO detector is really a causal factor.

In the aftermath of this accident, the CAA released a campaign on Unlicensed Charters, explaining the requirements for a legal air taxi or air charter flights and encouraging passengers to verify the operator of their flight and check that they are legal by visiting, along with requesting the name and qualifications of the pilot. If it doesn’t look right or you are unsure, you can also email [email protected] and someone will look into it for you. If you think you are being offered an illegal flight, you should report it at [email protected].

Further references:

Category: Accident Reports,


  • Minor quibble:

    “Piston engines produce high concentrations of carbon monoxide.”.

    Not if they’re running properly, they don’t.

    For best efficiency, they should run at perfect stochiometric ratios (exactly the right amount of fuel for the amount of air), which produces only CO2. Throwing CO out the tailpipe is, literally, throwing away half-burned fuel.

    That said, an air-cooled turbocharged aircraft engine may very well be designed to run significantly rich (too much fuel for the air), which will make CO. Reasons for this include:

    The excess fuel provides more cooling:
    That running lean (not enough fuel for the air) is exceedingly bad for them, so a rich safety margin is a good thing:
    Better throttle response (although with fuel injection, less so):
    They don’t need to pass air quality checks like cars:
    Second to the last above, they won’t have CO sensors in the tailpipe(s) to adjust the fuel injection for optimum fuel delivery (I imagine some do, for better fuel economy) so just how rich the engine is running may not be perfectly clear to the injection system.

    Among other things.

    Some of the major reasons to phase out the classic VW Beetle air-cooled flat four engine were listed above – the advantage of “fuel-cooling” kept the temperatures down, and running lean was a very good way to cook them in very short order. Even fuel-injected systems (like my old Type II bus, RIP) were only barely well-controlled enough to scrape by as a stopgap for awhile.


  • I have left aviation many years ago, and even so I flew turbine-powered aircraft (turbo-prop and jet) for more than twenty of my last active years.
    Most of my piston-engine time was on light singles (more than 3500 hours on Piper Super Cubs alone), the multi-engine hours included about the same time on the Cessna 310. That one was normally aspirated, not turbo-charged and of course not pressurised either.
    But what piston-eninge aircraft do have, in contrast to cars, is a way to compensate for operations in the rarefied air at altitude. (maybe later cars with computer controlled fuel injection and -ignition do). The pilot can manually adjust the mixture, reducing the amount of fuel by using the lean control. It can be done by pulling the “lean” until the engine starts running rough, and then pushing the control back in until running smoothly again. To ensure that this is done properly, many engines are also fitted with a cylinder head temperature sensor, with display on the instrument panel.
    The same principle would apply, but can be done far more accurately by monitoring the temperature.
    I never used the following, but I used to know pilots who leaned the engine PAST the high peak and reduced the fuel even further until the temperature started dropping again. They claimed a great saving of fuel, but I was never convinced that this technique, in effect using air instead of fuel in the mixture to cool the engine, would not affect the engines’ life.
    The 310’s engines had a TBO of 1700 hours. The company did not want to ground the aircraft waiting for the engines to be overhauled, so factory rebuilt units were ordered. It might have taken some time for replacements to be delivered, so we continued on an extension. The engineering facility (AMA, Aircraft Maintenance Amsterdam) monitored their condition. They could easily have done another 500 hours.
    Mist in the cabin? I was thinking of a sudden loss of cabin pressure. I have had this twice in a Citation. The first time at FL 390, the second one at FL 410. The cause in both cases was a blown door seal. The second time because a replacement had not been fitted properly. Anyway: the cabin air condensed and filled the cabin with mist.
    I was amused when Sylvia quoted “cowboy operation”. I had mentioned this in my own reaction. Although, “amused” is not really appropriate. This is a sad story.
    Sylvia’s summary is eminently plausible, in the absence of more concrete evidence.

    • Definitely true, in all ways. Old cars used to have manual mixture control, and the driver could monkey with it to their heart’s content. Since then, car makers have gone to great lengths to make mixture control automatic.

      Some newer engines are a bit like your fellow pilots – to save yet more fuel, they deliberately run extremely lean (and they’re called ‘lean-burn engines’ – whodda guessed?). They’re designed that way, and yes, it does improve fuel economy (and does nasty things to NOx emissions, but that’s a different problem).

      This particular aircraft also had another compensating mechanism for altitude – twin turbochargers!

      Any way you slice it, there’s not supposed to be engine exhaust in the cabin, and CO certainly poisoned the passenger. “Low Mist” could certainly also have been moisture in the exhaust cooling rapidly as it entered the cabin through a heater duct – suddenly wet feet would probably make most pilots look down.

      As the various safety outfits like to show, as does Ms. Wright, and as is typical, there were many contributing factors, but in this case it does look like the airplane poisoned its crew. J.

      • As another little aside, in the Robinson R44 helicopters I flew for a bit, the mixture control was either full on or full off – and they had a cylinder head temp gauge, and when you landed you got to sit quietly idling for three minutes as the cylinders cooled off, and only after then were you allowed to slam the mixture down to cut the engine.

        Cutting the ignition was absolutely forbidden. I did that by mistake once during a magneto check… oops.

  • ‘ “Piston engines produce high concentrations of carbon monoxide.”.
    Not if they’re running properly, they don’t.’

    As a former chemist, I doubt this. The cylinders of an internal-combustion engine are not the kind of highly-controlled reactor that produces exactly what an engineer at a chemical production plant would expect. Burning starts at (typically) a couple of points and spreads/progresses from the cylinder head to the piston in less than a hundredth of a second (probably less than a thousandth, but this wasn’t a field I specifically studied), so perfect combustion is unlikely at any mixture; the expectable result would include some CO as well as the CO2 and NOx we know the engines generate. (NOx is also not pleasant to breathe; one of the compounds is anesthetic/intoxicant, while others can combine with moisture to produce acids.)

    OTOH, as a sometime copyeditor I was also struck by the recommendation “require piston engine aircraft which may have a risk of carbon monoxide poisoning to have a CO detector”. Maybe the writer was just careless (omitting the commas after “aircraft” and “poisoning”, or maybe the writer believed that some piston-engine aircraft posed a risk and some didn’t — and that distinguishing between them was possible. I hope it wasn’t the latter, but the way it’s written lets anyone say their aircraft doesn’t need the detector. Commas count — there was a recent US case (that ISTR made enough noise to be reported by the BBC) in which a substantial amount of money hinged on a comma placement that made the difference between optional and mandatory.

    I can imagine (given the lack of maintenance history and the operator’s general attitude) that a poor door seal would let the passenger get more of a dose than the pilot — but I think Sylvia is right that the pilot would have been slowly dying without realizing it.

  • Honestly, I don’t understand why the regulatory authorities don’t require carbon monoxide detectors in piston aircraft. They aren’t that expensive or complicated, and I have seen so many accidents where carbon monoxide poisoning was a factor. It seems like cheap insurance. This is also one of the things I don’t love about the way the American accident investigation process works: the NTSB identifies the causes of crashes, but has no authority to actually fix the problems they find. They have to rely on the FAA agreeing with them that something is worth issuing a rulemaking about, and the FAA often does not for a variety of (in my opinion political) reasons. Personally, I think it would be better if the NTSB had some regulatory rulemaking authority. But unfortunately, that is not the system we have.

    • When it comes to regulations, we have safety on one hand, and money/airline interests on the other. Whoever makes the regulations has to effect a compromise, via a process that is necessarily political. The fact that NTSB does not have that power insulates it somewhat from these politics and allows it to be the voice for safety, because it doesn’t need to compromise. It’s good to have that voice.

  • I think that Jon is correct, although in my opinion there is a chain of events that started with “cowboy operation”. The operation was largely illegal and the pilot did not really share what, in the light of what followed, was probably vital information about the state of the aircraft with the mechanics. The end result, yes I agree with Jon, was more than likely CO poisoning.

  • I should note wrt my previous comment that “high concentration” is a loose term. A well-tuned internal-combustion engine won’t produce much CO compared to badly-tuned engine, but it produces a lot compared to (e.g.) a steam engine and possibly even a jet engine (since modern jet engines take in far more air than is needed). The problem with CO is that it’s one of the few poisons that the body can’t expel given time — it binds to hemoglobin much more tightly than either O2 or CO2 — so not-very-much can still do a lot of damage. Having the exhaust in front of the passenger compartment (unlike automobiles, where exhaust is piped past the rear bumper) makes single-engine planes inherently more dangerous.

    The NTSB is responsible for all forms of transportation, where the FAA is responsible only for aviation; it may also find being powerless is an advantage, because it’s more likely to at least get facts exposed for the politicians to fight over. Not that this always works — ISTR legitimate complaints that it has been too likely to consider the pilot at fault if the pilot didn’t do Sully-class miracles with a misbehaving or failing airplane, rather than bring out facts that would embarass major manufacturers — but it may help.

    • My personal expertise in the field comes mostly from automobile engines and their exhaust gases from an air pollution standpoint.

      No, no piston is going to be a “perfect reactor”, but there’s an awful lot of work that’s gone into making them as good as they can be. “Flame front management” is a thing, as the burn sweeps through the compressed fuel-air mixture. I can’t imagine aircraft engine makers overlooking it any more than car manufacturers.

      There exist dual ignition point gasoline engines, but they’re distinctly unusual. The vast majority only have one spark plug, and any other source of ignition is a sign of a major failure.

      Those that do exist are for the reason above, to improve complete combustion. This comes with many advantages, not merely reducing air pollution – again, CO in the tailpipe is literally throwing away fuel.

      Worth noting, however, automobiles (if they want to pass modern smog tests) also all have catalytic convertors (‘cats’) to process (“burn”, if you like) CO into CO2 (among other things). The pistons are not perfect, and without the ‘cat’, they wouldn’t pass air pollution laws.

      Aircraft, as far as I know, don’t have cats, mostly (I suspect) for weight reasons, plus bits of cost and size. Thus an exhaust leak would be worse there.

      Incidentally, the VW Beetle (and all air-cooled flat-four rear-engined VWs) used the same heater mechanism as the incident aircraft – a muff around the tailpipe that interior air is blown through then into the cabin. They worked better in the little Beetle than in the Type II microbus.

      Between engine design and smog-reducing equipment, modern cars (when in proper working order) are remarkably clean-running. The old-school suicide technique of running a hose from the tailpipe into the cabin, then starting the car and taking a nap inside won’t work anymore – your body can process the CO faster than the car will emit it.

      Back to the incident – There’s no evidence for this that I’ve seen, but it’s possible that this “airline” had the same cavalier attitude towards engine maintenance as they did to legality, and engines can drift quite a long way away from ‘running properly’ before it’s obvious to a casual eye that something’s wrong. The engine may well have been putting out rather more CO than it should have been.

      Between that, and its merely being a high-strung aircraft engine, the evidence of the passenger, and the other incidental weirdness of the flight, I think CO poisoning should rank high on the list of ‘why this happened’.

      Thanks for your time, J.

  • A solid, albeit circumstantial, case that the pilot suffered from CO poisoning. It is difficult to envision a scenario where the football player was poisoned elsewhere.

    The half life of carboxyhemoglobin is a long 300 minutes at sea level but the player’s levels would have been declining slowly ever since arriving at the airport if his exposure was earlier.

    It’s important to understand that measured carboxyhemoglobin is only weakly associated with severity of symptoms and it matters if the exposure is slow (low levels of CO for a long time) or fast (high CO levels for short duration). That being said, 58% is very high and it is unlikely he was even conscious .

  • All of the comments have merit. We do not know for sure what happened exactly, nor the sequence of events. All we can do is weigh the facts as they have been presented and try to come to a conclusion that makes some sense.
    But still, there is this niggling sense in my mind that the pilot was not really paying much attention to the state of the aircraft. He was not even properly licenced, not qualified nor did he have the necessary experience to carry out this flight.
    The Malibu is pressurised – normally. Why did the pilot elect to return to Cardiff at a low altitude? Usually a higher level results in a smoother ride, which is easier on the pilot and reduces fatigue. So there still remains the possibility that something went wrong with the pressurisation, which he then failed to communicate to maintenance. Was he afraid that the aircraft would be grounded if he told the truth? I don’t know enough about the systems that provide cabin pressure in a single piston-engine aircraft. It has to be a compressor, engine- or exhaust gas driven? In other words: mechanical or via a turbine? If the latter, could there have been a defect , for instance a seal, allowing exhaust gas to escape through the turbine into the compressor side and so feeding CO into the cabin? Could this have progressed from a minor CO leak into a major one as the defective seal would continue to deteriorate? All these are questions, not statements, because I do not know these systems. But it might explain the “bang” or “thud” and the “mist”.
    I have logged probably in the order of 9000 flying hours on aircraft with piston engines. But none had a pressure cabin nor were they turbo-charged. So I am a bit out of my depth here, quite frankly.
    One thing jumps right out of the page: YES the pilot was guilty. Maybe not the only guilty party, but apart from not being qualified for this flight, it really seems to me that he did not want to lose this one due to necessary maintenance so he elected to “play stumm” and depart without having the aircraft properly looked at by the nechanics.
    He paid for it with his life, and that of the passenger.

    • The general slackness of the programme and likely of maintenance, and the lack of appropriate pressure testing of exhaust system also points in the direction of carbon monoxide poisoning.

      I should point out that carbon monoxide is not a direct poison. It works by displacing oxygen from hemoglobin, leading to hypoxemia and thence to oxygen starvation of the brain and the cardiac system. This is what leads to the central nervous system collapse, Cardiac arrhythmia, and death.

      Further, carboxyhemoglobin causes a leftward shift in the oxygen saturation curve, which limits the delivery of oxygen to the tissues.

      These effects are worsened by altitude.

  • I picked up a colleague of the pilot who died, a few months after this happened. I work as a taxi driver in York and the job was from a small airfield north of York, Rufforth, into the city and there was 2 people. The colleague had had to make an emergency landing at Rufforth due to a fault with the aircraft they were flying, he said they’d received a fine from the airfield manager at Rufforth becuase its for glider use only, I think it was only a £100. He said they were flying from Cumbria to London, and had a problem with the plane (he was specific what the issue was but I forgot, he told me what airplane it was too but i dont recall that either), I remember it seemed odd becuase York isnt really on a straight line trajectory from Cumbria to London. The piolt said he had the pilot deceased’ s log book and speculated whether air crash investigation were going to ask him for it otherwise he said he would keep it. He also said the crash flight had been organised through wingly a website that setup ride sharing flights. Presumably the flight he was on was of a similar nature as the conversation between him and the other passenger revolved around getting to the destination, which they said they would do by train. Even though I did’nt drop them at the station I took them to a pub!
    I’ m a big fan of the site, it’s a great read. I thought giving you this extra info might help paint a picture of the accident flight.

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